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Borah A, Dey S, Siddiqui K, Gupta SK, Rajaraman G, Murugavel R. Magnetic anisotropy in octahedral Dy(III) and Yb(III) complexes. Dalton Trans 2024. [PMID: 38618749 DOI: 10.1039/d3dt04352e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
New organophosphate complexes [Ln(dippH)3(dippH2)3]·(H2O)6, (Ln = Dy, Yb and Y; dippH2 = 2,6-diisopropylphenyl phosphate), displaying octahedral coordination geometry around the metal ion, exhibit unusual slow relaxation of magnetisation, which is investigated through experimental studies and ab initio CASSCF calculations.
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Affiliation(s)
- Aditya Borah
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
- Department of Chemistry, Jengraimukh College, Majuli, Assam, 785105, India
| | - Sourav Dey
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
| | - Kehkasha Siddiqui
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
| | - Sandeep K Gupta
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, Delhi, 110016, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
| | - Ramaswamy Murugavel
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
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2
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Sarkar S, Tiwari RK, Samanta D, Guchhait T, Sañudo EC, Rajaraman G, Rath SP. Unusual Stabilisation of Remarkably Bent Tetra-Cationic Tetra-radical Intermolecular Fe(III) μ-Oxo Tetranuclear Complexes. Angew Chem Int Ed Engl 2024:e202402344. [PMID: 38478415 DOI: 10.1002/anie.202402344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Indexed: 04/24/2024]
Abstract
A hitherto unknown series of air stable, π-conjugated, remarkably bent tetra-cation tetra-radical intermolecular Fe(III) μ-oxo tetranuclear complex, isolated from the dication diradical diiron(III) porphyrin dimers, has been synthesised and spectroscopically characterised along with single crystal X-ray structure determination of two such molecules. These species facilitate long-range charge/radical delocalisation through the bridge across the entire tetranuclear unit manifesting an unusually intense NIR band. Assorted spin states of Fe(III) centres are stabilised within these unique tetranuclear frameworks: terminal six-coordinate iron centres stabilise the admixed intermediate spin states while the central five-coordinate iron centres stabilise the high-spin states. Variable temperature magnetic susceptibility measurements indicated strong antiferromagnetic coupling for the Fe(III)-O-Fe(III) unit while the exchange interactions between the Fe centres and the porphyrin π-cation radicals are weaker as supported both by magnetic data and DFT calculations. The nature of orbital overlap between the SOMOs of Fe(III) and π* orbital of the porphyrin was found to rationalise the observed exchange coupling, establishing such a complex magnetic exchange in this tetranuclear model with a significant bioinorganic relevance.
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Affiliation(s)
- Sabyasachi Sarkar
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Rupesh Kumar Tiwari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, 400076, India
| | - Deepannita Samanta
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Tapas Guchhait
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - E Carolina Sañudo
- Secció de Química Inorgànica, Department de Química Inorgànica i Orgànica, Facultat de Química, Universitat de Barcelona, C/Martí i Franqués 1-11, 08028, Barcelona, Spain
- Institut de Nanociència i Nanotecnologia, IN2UB, Universitat de Barcelona, C/Martí i Franqués 1-11, 08028, Barcelona, Spain
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, 400076, India
| | - Sankar Prasad Rath
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
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Kumar R, Ansari A, Comba P, Rajaraman G. Rebound or Cage Escape? The Role of the Rebound Barrier for the Reactivity of Non-Heme High-Valent Fe IV =O Species. Chemistry 2024; 30:e202303300. [PMID: 37929771 DOI: 10.1002/chem.202303300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 11/03/2023] [Accepted: 11/06/2023] [Indexed: 11/07/2023]
Abstract
Owing to their high reactivity and selectivity, variations in the spin ground state and a range of possible pathways, high-valent FeIV =O species are popular models with potential bioinspired applications. An interesting example of a structure-reactivity pattern is the detailed study with five nonheme amine-pyridine pentadentate ligand FeIV =O species, including N4py: [(L1 )FeIV =O]2+ (1), bntpen: [(L2 )FeIV =O]2+ (2), py2 tacn: [(L3 )FeIV =O]2+ (3), and two isomeric bispidine derivatives: [(L4 )FeIV =O]2+ (4) and [(L5 )FeIV =O]2+ (5). In this set, the order of increasing reactivity in the hydroxylation of cyclohexane differs from that with cyclohexadiene as substrate. A comprehensive DFT, ab initio CASSCF/NEVPT2 and DLPNO-CCSD(T) study is presented to untangle the observed patterns. These are well reproduced when both activation barriers for the C-H abstraction and the OH rebound are taken into account. An MO, NBO and deformation energy analysis reveals the importance of π(pyr) → π*xz (FeIII -OH) electron donation for weakening the FeIII -OH bond and thus reducing the rebound barrier. This requires that pyridine rings are oriented perpendicularly to the FeIII -OH bond and this is a subtle but crucial point in ligand design for non-heme iron alkane hydroxylation.
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Affiliation(s)
- Ravi Kumar
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Powai, 400076, India
| | - Azaj Ansari
- Department of Chemistry, Central University of Haryana, Haryana, 123031, India
| | - Peter Comba
- Institute of Inorganic Chemistry &, Interdisciplinary Center for Scientific Computing, Heidelberg University, 69120, Heidelberg, Germany
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Powai, 400076, India
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Tiwari RK, Nabi R, Kumawat RL, Pathak B, Rajaraman G. Enhancing Spin-Transport Characteristics, Spin-Filtering Efficiency, and Negative Differential Resistance in Exchange-Coupled Dinuclear Co(II) Complexes for Molecular Spintronics Applications. Inorg Chem 2024; 63:316-328. [PMID: 38114426 DOI: 10.1021/acs.inorgchem.3c03200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
Single-molecule spintronics, where electron transport occurs via a paramagnetic molecule, has gained wide attention due to its potential applications in the area of memory devices to switches. While numerous organic and some inorganic complexes have been employed over the years, there are only a few attempts to employ exchange coupled dinuclear complexes at the interface, and the advantage of fabricating such a molecular spintronics device in the observation of switchable Kondo resonance was demonstrated recently in the dinuclear [Co2(L)(hfac)4] (1) complex (Wagner et al., Nat. Nanotechnol. 2013, 8, 575-579). In this work, employing an array of theoretical tools such as density functional theory (DFT), the ab initio CASSCF/NEVPT2 method, and DFT combined with nonequilibrium Green Function (NEGF) formalism, we studied in detail the role of magnetic coupling, ligand field, and magnetic anisotropy in the transport characteristics of complex 1. Particularly, our calculations not only reproduce the current-voltage (I-V) characteristics observed in experiments but also unequivocally establish that these arise from an exchange-coupled singlet state that arises due to antiferromagnetic coupling between two high-spin Co(II) centers. Further, the estimated spin Hamiltonian parameters such as J, g values, and D and E/D values are only marginally altered for the molecule at the interface. Further, the exchange-coupled state was found to have very similar transport responses, despite possessing significantly different geometries. Our transport calculations unveil a new feature of the negative differential resistance (NDR) effect on 1 at the bias voltage of 0.9 V, which agrees with the experimental I-V characteristics reported. The spin-filtering efficiency (SFE) computed for the spin-coupled states was found to be only marginal (∼25%); however, if the ligand field is fine-tuned to obtain a low-spin Co(II) center, a substantial SFE of 44% was noted. This spin-coupled state also yields a very strong NDR with a peak-to-valley ratio (PVR) of ∼56 - a record number that has not been witnessed so far in this class of compounds. Additionally, we have established further magnetostructural-transport correlations, providing valuable insights into how microscopic spin Hamiltonian parameters can be associated with SFE. Several design clues to improve the spin-transport characteristics, SFE and NDR in this class of molecule, are offered.
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Affiliation(s)
| | - Rizwan Nabi
- Department of Chemistry, IIT Bombay, Powai, Mumbai 400076, India
| | | | - Biswarup Pathak
- Department of Chemistry, IIT Indore, Indore, Madhya Pradesh 453-552, India
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Britto NJ, Sen A, Rajaraman G. Unravelling the Effect of Acid-Driven Electron Transfer in High-Valent Fe IV =O/Mn IV =O Species and Its Implications for Reactivity. Chem Asian J 2023; 18:e202300773. [PMID: 37855305 DOI: 10.1002/asia.202300773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 10/12/2023] [Accepted: 10/16/2023] [Indexed: 10/20/2023]
Abstract
The electron transfer (ET) step is one of the crucial processes in biochemical redox reactions that occur in nature and has been established as a key step in dictating the reactivity of high-valent metal-oxo species. Although metalloenzymes possessing metal-oxo units at their active site are typically associated with outer-sphere electron transfer (OSET) processes, biomimetic models, in contrast, have been found to manifest either an inner-sphere electron transfer (ISET) or OSET mechanism. This distinction is clearly illustrated through the behaviour of [(N4Py)MnIV (O)]2+ (1) and [(N4Py)FeIV (O)]2+ (2) complexes, where complex 1 showcases an OSET mechanism, while complex 2 exhibits an ISET mechanism, especially evident in their reactions involving C-H bond activation and oxygen atom transfer reactions in the presence of a Lewis/Bronsted acid. However, the precise reason for this puzzling difference remains elusive. This work unveils the origin of the perplexing inner-sphere vs outer-sphere electron transfer process (ISET vs OSET) in [(N4Py)MnIV (O)]2+ (1) and [(N4Py)FeIV (O)]2+ (2) species in the presence of Bronsted acid. The calculations indicate that when the substrate (toluene) approaches both 1 and 2 that is hydrogen bonded with two HOTf molecules (denoted as 1-HOTf and 2-HOTf, respectively), proton transfer from one of the HOTf molecules to the metal-oxo unit is triggered and a simultaneous electron transfer occurs from toluene to the metal centre. Interestingly, the preference for OSET by 1-HOTf is found to originate from the choice of MnIV =O centre to abstract spin-down (β) electron from toluene to its δ(dxy ) orbital. On the other hand, in 2-HOTf, a spin state inversion from triplet to quintet state takes place during the proton (from HOTf) coupled electron transfer (from toluene) preferring a spin-up (α) electron abstraction to its σ* (dz 2 ) orbital mediated by HOTf giving rise to ISET. In addition, 2-HOTf was calculated to possess a larger reorganisation energy, which facilitates the ISET process via the acid. The absence of spin-inversion and smaller reorganisation energy switch the mechanism to OSET for 1-HOTf. Therefore, for the first time, the significance of spin-state and spin-inversion in the electron transfer process has been identified and demonstrated within the realm of high-valent metal-oxo chemistry. This discovery holds implications for the potential involvement of high-valent Mn-oxo species in performing similar transformative processes within Photosystem II.
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Affiliation(s)
| | - Asmita Sen
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India
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Bhatt G, Sharma T, Gupta SK, Meyer F, Rajaraman G, Murugavel R. Tuning Magnetic Anisotropy in Co(II) Tetrahedral Carbazole-Modified Phosphine Oxide Single-Ion Magnets: Importance of Structural Distortion versus Heavy-Ion Effect. Inorg Chem 2023; 62:18915-18925. [PMID: 37947449 DOI: 10.1021/acs.inorgchem.3c02401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
Three mononuclear cobalt(II) tetrahedral complexes [Co(CzPh2PO)2X2] (CzPh2PO = (9H-carbazol-9-yl)diphenylphosphine oxide and X = Cl (1), Br (2), I (3)) have been synthesized using a simple synthetic approach to examine their single-ion magnetic (SIM) behavior. A detailed study of the variation in the dynamic magnetic properties of the Co(II) ion in a tetrahedral ligand field has been carried out by the change of the halide ligand. The axial zero-field splitting parameter D was found to vary from -16.4 cm-1 in 1 to -13.8 cm-1 in 2 and +14.6 cm-1 in 3. All the new complexes exhibit field-induced SIM behavior. The results obtained from ab initio CASSF calculations match well with the experimental data, revealing how halide ions induce a change in the D value as we move from Cl- to I-. The ab initio calculations further reveal that the change in the sign of D is due to the multideterminant characteristics of the ground state wave function of 1 and 2, while single-determinant characteristics are instead observed for 3. To gain a better understanding of the relationship between the structural distortion and the sign and magnitude of D values, magnetostructural D correlations were developed using angular relationships, revealing the importance of structural distortions over the heavy halide effect in controlling the sign of D values. This study broadens the scope of employing electronically and sterically modified phosphine oxide ligands in building new types of air-stable Co(II) SIMs.
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Affiliation(s)
- Gargi Bhatt
- Department of Chemistry, Indian Institute of Technology Bombay, Powai 400076, Mumbai, India
| | - Tanu Sharma
- Department of Chemistry, Indian Institute of Technology Bombay, Powai 400076, Mumbai, India
| | - Sandeep K Gupta
- University of Göttingen, Institute of Inorganic Chemistry, Göttingen D-37077, Germany
| | - Franc Meyer
- University of Göttingen, Institute of Inorganic Chemistry, Göttingen D-37077, Germany
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai 400076, Mumbai, India
| | - Ramaswamy Murugavel
- Department of Chemistry, Indian Institute of Technology Bombay, Powai 400076, Mumbai, India
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Saha P, Chrysochos N, Elvers BJ, Pätsch S, Uddin SI, Krummenacher I, Nandeshwar M, Mishra A, Raman KV, Rajaraman G, Prabusankar G, Braunschweig H, Ravat P, Schulzke C, Jana A. Bis-Olefin Based Crystalline Schlenk Hydrocarbon Diradicals with a Triplet Ground State. Angew Chem Int Ed Engl 2023; 62:e202311868. [PMID: 37646230 DOI: 10.1002/anie.202311868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 08/28/2023] [Accepted: 08/28/2023] [Indexed: 09/01/2023]
Abstract
A modular approach for the synthesis of isolable crystalline Schlenk hydrocarbon diradicals from m-phenylene bridged electron-rich bis-triazaalkenes as synthons is reported. EPR spectroscopy confirms their diradical nature and triplet electronic structure by revealing a half-field signal. A computational analysis confirms the triplet state to be the ground state. As a proof-of-principle for the modular methodology, the 4,6-dimethyl-m-phenylene was further utilized as a coupling unit between two alkene motifs. The steric conjunction of the 4,6-dimethyl groups substantially twists the substituents at the nonbonding electron bearing centers relative to the central coupling m-phenylene motif. As a result, the spin delocalization is decreased and the exchange coupling between the two unpaired spins, hence, significantly reduced. Notably, 108 years after Schlenk's m-phenylene-bis(diphenylmethyl) synthesis as a diradical, for the first time we were able to isolate its derivative with the same spacer, i.e. m-phenylene, between two radical centers in a crystalline form.
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Affiliation(s)
- Priyanka Saha
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India
| | - Nicolas Chrysochos
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India
| | - Benedict J Elvers
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, 17489, Greifswald, Germany
| | - Sebastian Pätsch
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, 17489, Greifswald, Germany
| | - Sk Imraj Uddin
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India
| | - Ivo Krummenacher
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Muneshwar Nandeshwar
- Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, 502284, India
| | - Anshika Mishra
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India
| | - Karthik V Raman
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India
| | - Ganesan Prabusankar
- Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, 502284, India
| | - Holger Braunschweig
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Prince Ravat
- Institute of Organic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Carola Schulzke
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, 17489, Greifswald, Germany
| | - Anukul Jana
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India
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Sen A, Ansari A, Swain A, Pandey B, Rajaraman G. Probing the Origins of Puzzling Reactivity in Fe/Mn-Oxo/Hydroxo Species toward C-H Bonds: A DFT and Ab Initio Perspective. Inorg Chem 2023; 62:14931-14941. [PMID: 37650771 DOI: 10.1021/acs.inorgchem.3c01632] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
Activation of C-H bonds using an earth-abundant metal catalyst is one of the top challenges of chemistry, where high-valent Mn/Fe-oxo(hydroxo) biomimic species play an important role. There are several open questions related to the comparative oxidative abilities of these species, and a unifying concept that could accommodate various factors influencing reactivity is lacking. To shed light on these open questions, here, we have used a combination of density functional theory (DFT) (B3LYP-D3/def2-TZVP) and ab initio (CASSCF/NEVPT2) calculations to study a series of high-valent metal-oxo species [Mn+H3buea(O/OH)] (M = Mn and Fe, n = II to V; H3buea = tris[(N'-tert-butylureaylato)-N-ethylene)]aminato towards the activation of dihydroanthracene (DHA). The H-bonding network in the ligand architecture influences the ground state-excited state gap and brings several excited states of the same spin multiplicity closer in energy, which triggers reactivity via one of those excited states, reducing the kinetic barriers for the C-H bond activation and rationalizing several puzzling reactivity trends observed in various high-valent Mn/Fe-oxo(hydroxo) species.
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Affiliation(s)
- Asmita Sen
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
| | - Azaj Ansari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
| | - Abinash Swain
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
| | - Bhawana Pandey
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
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Rana TRK, Swain A, Rajaraman G. The role of agostic interaction in the mechanism of ethylene polymerisation using Cr(III) half-sandwich complexes: What dictates the reactivity? Dalton Trans 2023; 52:11826-11834. [PMID: 37555755 DOI: 10.1039/d3dt02032k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2023]
Abstract
Chromium-based catalysts play a significant role in the production of ultra-high molecular weight polyethylene, and half-sandwich functionalised-metallocene complexes were proven to be one of the most suitable candidates as catalysts for generating such large polymeric-length olefins. Earlier experimental studies on olefin polymerisation using a series of catalysts such as [L1-2CrCl2] (where L1 = 1-((pyridin-2-yl)methyl)indenyl (1) and L2 = 2-methyl-1-{[4-(yridinene-1-yl)yridine-2-yl]methyl}-1H-indenyl (2)) reveal significant variation where peripheral substitution on the ligand was found to influence the reactivity significantly. However, the specific ligand position that affects the reactivity has not been established. As these reactions are fast and robust, it is challenging to establish reactive intermediates via experiments, and therefore, mechanistic clues for such reactions are elusive. Here we have undertaken a detailed computational study by employing an array of DFT (uB3LYP-D3/def2-TZVP, CASSCF/NEVPT2, and DLPNO-CCSD(T) methods to explore the substituted and non-substituted pyridine-cyclo-pentadienyl chromium complexes and their influence on the catalytic activity in ethylene polymerisation. Our study not only unravels the catalytic pathway for olefin polymerisation for such Cr(III)-half-sandwich complexes but also reveals that the energetics of the formation of pseudo-three-coordinate alkyl intermediates is key to the variation in the reactivity observed. A detailed examination using MO and NBO analysis unveils the presence of a C-H⋯Cr agostic interaction that is found to significantly stabilise this intermediate when the pyridine ligand has strong electron-donating groups at its para position. The other substitutions, such as on the cyclopentadienyl ligand, neither yield the desired stability nor the desired interaction. Further studies on models support this proposal. In order to improve the efficiency and selectivity of catalytic systems in olefin polymerisation, we strongly advocate for the integration of agostic interactions as a crucial criterion in the design of future catalysts. Considering the prevalence of electron-deficient metal centres in successful olefin polymerisation catalysts, this research prompts a broader mechanistic inquiry to propose a unified approach for this industrially crucial reaction.
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Affiliation(s)
| | - Abinash Swain
- Department of Chemistry, Indian Institute of Technology, Powai, Mumbai, India.
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology, Powai, Mumbai, India.
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10
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Jose R, Pal S, Rajaraman G. Unraveling the origin of the cooperative adsorption of carbon monoxide in an Fe(II) metal-organic framework. Chem Commun (Camb) 2023; 59:10315-10318. [PMID: 37548232 DOI: 10.1039/d3cc01185b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Using periodic DFT calculations, we have established the mechanism of the unusual cooperative adsorption of CO gas in an Fe-bistriazolate MOF observed previously. The binding of one CO molecule to FeII triggers structural alteration of the neighbouring Fe centres, reducing the steric energy penalty and aiding cooperative adsorption. This is similar to the entatic state concept proposed for metalloenzymes, and offers novel strategies for selective gas adsorption.
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Affiliation(s)
- Reshma Jose
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
| | - Sourav Pal
- Department of Chemistry, Ashoka University, Sonipat, Haryana, 131029, India.
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
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11
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Borah A, Dey S, Gupta SK, Rajaraman G, Murugavel R. Field-induced SIM behaviour in early lanthanide(III) organophosphates containing 18-crown-6. Dalton Trans 2023. [PMID: 37317701 DOI: 10.1039/d3dt01206a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Single-ion magnets (SIMs) have attracted wide attention in recent years. Despite tremendous progress in late lanthanide SIMs, reports on early lanthanides exhibiting SIM characteristics are scarce. A series of five novel 18-crown-6 encapsulated mononuclear early lanthanide(III) organophosphates, [{(18-crown-6)Ln(dippH)3}{(18-crown-6)Ln(dippH)2(dippH2)}]·[I3] [Ln = Ce (1), Pr (2), Nd (3)] and [{Ln(18-crown-6)(dippH)2(H2O)}·{I3}] [Ln = Sm (4) and Eu (5)], have been synthesised in the present study. 18-crown-6 coordinates to Ln(III) ions in an equatorial position while the axial positions are occupied by either three phosphate moieties as in 1-3 or two phosphate moieties and one water molecule as in 4 and 5, resulting in a muffin-shaped coordination geometry around the Ln(III) centres. Magnetic susceptibility measurements reveal that Ce and Nd complexes are field-induced single-ion magnets with significant barrier heights. Furthermore, the ab initio CASSCF/RASSI-SO/SINGLE_ANISO calculations on complexes 1 and 3 reveal significant QTM in the ground state rationalising the field-induced single-ion magnetism behaviour of these complexes.
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Affiliation(s)
- Aditya Borah
- Department of Chemistry, Indian Institute of Technology, Powai, Mumbai, India.
| | - Sourav Dey
- Department of Chemistry, Indian Institute of Technology, Powai, Mumbai, India.
| | - Sandeep K Gupta
- Department of Chemistry, Indian Institute of Technology, Powai, Mumbai, India.
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology, Powai, Mumbai, India.
| | - Ramaswamy Murugavel
- Department of Chemistry, Indian Institute of Technology, Powai, Mumbai, India.
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Singh J, Sharma S, Prakasham AP, Rajaraman G, Ghosh P. Accessing Bioactive Hydrazones by the Hydrohydrazination of Terminal Alkynes Catalyzed by Gold(I) Acyclic Aminooxy Carbene Complexes and Their Gold(I) Arylthiolato and Gold(III) Tribromo Derivatives: A Combined Experimental and Computational Study. ACS Omega 2023; 8:21042-21073. [PMID: 37323414 PMCID: PMC10268297 DOI: 10.1021/acsomega.3c01925] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 05/05/2023] [Indexed: 06/17/2023]
Abstract
Hydrohydrazination of terminal alkynes with hydrazides yielding hydrazones 5-14 were successfully catalyzed by a series of gold(I) acyclic aminooxy carbene complexes of the type [{(4-R2-2,6-t-Bu2-C6H2O)(N(R1)2)}methylidene]AuCl, where R2 = H, R1 = Me (1b); R2 = H, R1 = Cy (2b); R2 = t-Bu, R1 = Me (3b); R2 = t-Bu, R1 = Cy (4b). The mass spectrometric evidence corroborated the existence of the catalytically active solvent-coordinated [(AAOC)Au(CH3CN)]SbF6 (1-4)A species and the acetylene-bound [(AAOC)Au(HC≡CPhMe)]SbF6 (3B) species of the proposed catalysis cycle. The hydrohydrazination reaction was successfully employed in synthesizing several bioactive hydrazone compounds (15-18) with anticonvulsant properties using a representative precatalyst (2b). The DFT studies favored the 4-ethynyltoluene (HC≡CPhMe) coordination pathway over the p-toluenesulfonyl hydrazide (NH2NHSO2C6H4CH3) coordination pathway, and that proceeded by a crucial intermolecular hydrazide-assisted proton transfer step. The gold(I) complexes (1-4)b were synthesized from the {[(4-R2-2,6-t-Bu2-C6H2O)(N(R1)2)]CH}+OTf- (1-4)a by treatment with (Me2S)AuCl in the presence of NaH as a base. The reactivity studies of (1-4)b yielded the gold(III) [{(4-R2-2,6-t-Bu2-C6H2O)(N(R1)2)}methylidene]AuBr3 (1-4)c complexes upon reaction with molecular bromine and the gold(I) perfluorophenylthiolato derivatives, [{(4-R2-2,6-t-Bu2-C6H2O)(N(R1)2)}methylidene]AuSC6F5 (1-4)d, upon treatment with C6F5SH.
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Swain A, Tiwari RK, Khatua M, Rajaraman G. Fluxionality Modulating the Magnetic Anisotropy in Lanthanoarene [(ηC nR n) 2Ln(II/III)] ( n = 4-8) Single-Ion Magnets. Inorg Chem 2023. [PMID: 37280148 DOI: 10.1021/acs.inorgchem.3c00956] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Lanthanoarenes have emerged as the best bet for the futuristic application of single-ion magnets in information storage devices. While dysprosocenium molecules with various substituents at the arene ring exhibit a very large blocking temperature, the corresponding Er(III) analogues do not, and this is reversed if the size of the arene ring is eight. Using a combination of ab initio CASSCF and DFT-based molecular dynamics (MD) study, we have explored 25 Dy(III)/Er(III)/Ho(II)/Tb(II)/Dy(II) arene complexes with the ring size varying from 4 to 8 to understand the differences observed and decipher the correlation of structure to the spin dynamics behavior. Among the oxidation state of +2 complexes studied, Tb(II) exhibits the highest barrier, with the Cp-Tb-Cp angle being linear. Further, one of the four-membered arene model studied exhibits a very large barrier of 1442 cm-1, suggesting a potential high-blocking SIM. While bulky substituents at the arene ring help increase the axiality and the CR-Ln-CR angle, this also fetches several agostic C-H···Ln interactions, which injects transverse anisotropy. Furthermore, MD coupled with the CASSCF study reveals that the fluxional behavior of the arene ring generates several rotational conformers that are even accessible at lower temperatures offering a shortcut to the magnetization relaxation process. The importance of structural fluctuations in controlling the magnetic anisotropy by choosing apt metal-ion/ring partners and the corresponding substituents has been highlighted to offer clues to the futuristic SIM design.
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Affiliation(s)
- Abinash Swain
- Department of Chemistry, IIT Bombay, Powai, Mumbai 400076, India
| | | | - Munmun Khatua
- Department of Chemistry, IIT Bombay, Powai, Mumbai 400076, India
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Swain A, Sharma T, Rajaraman G. Strategies to quench quantum tunneling of magnetization in lanthanide single molecule magnets. Chem Commun (Camb) 2023; 59:3206-3228. [PMID: 36789911 DOI: 10.1039/d2cc06041h] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Enhancing blocking temperature (TB) is one of the holy grails in Single Molecule Magnets(SMMs), as any future potential application in this class of molecules is directly correlated to this parameter. Among many factors contributing to a reduction of TB value, Quantum Tunnelling of Magnetisation (QTM), a phenomenon that is a curse or a blessing based on the application sought after, tops the list. Theoretical tools based on density functional and ab initio CASSCF/RASSI-SO methods have played a prominent role in estimating various spin Hamiltonian parameters and establishing the mechanism of magnetization relaxation in this class of molecules. Particularly, various strategies to quench QTM effects go hand-in-hand with experiments, and different methods proposed to quell QTM effects are scattered in the literature. In this perspective, we have explored various approaches that are proposed in the literature to quench QTM effects, and these include the role of (i) local symmetry of lanthanides, (ii) super-exchange interaction in {3d-4f} complexes, (iii) direct-exchange interaction in {radical-4f} and metal-metal bonded complexes to suppress the QTM, (iv) utilizing external stimuli such as an electric field or pressure to modulate the QTM and (v) avoiding QTM effects by stabilising toroidal states in 4f and {3d-4f} clusters. We believe the strategies summarized here will help to design new-generation SMMs.
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Affiliation(s)
- Abinash Swain
- Department of Chemistry, IIT Bombay, Powai, Mumbai - 400076, India.
| | - Tanu Sharma
- Department of Chemistry, IIT Bombay, Powai, Mumbai - 400076, India.
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Sen A, Ansari M, Rajaraman G. Mechanism of Hydroboration of CO 2 Using an Fe Catalyst: What Controls the Reactivity and Product Selectivity? Inorg Chem 2023; 62:3727-3737. [PMID: 36802517 DOI: 10.1021/acs.inorgchem.2c02812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Using a combination of density functional theory (DFT) and ab initio complete active space self-consistent field (CASSCF) calculations, various elementary steps in the mechanism of the reductive hydroboration of CO2 to two-electron-reduced boryl formate, four-electron-reduced bis(boryl)acetal, and six-electron-reduced methoxy borane by the [Fe(H)2(dmpe)2] catalyst were established. The replacement of hydride by oxygen ligation after the boryl formate insertion step is the rate-determining step. Our work unveils, for the first time, (i) how a substrate steers product selectivity in this reaction and (ii) the importance of configurational mixing in contracting the kinetic barrier heights. Based on the reaction mechanism established, we have further focused on the effect of other metals, such as Mn and Co, on rate-determining steps and on catalyst regeneration.
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Affiliation(s)
- Asmita Sen
- Department of Chemistry, IIT Bombay, Powai 400076, Maharashtra, India
| | - Mursaleem Ansari
- Department of Chemistry, IIT Bombay, Powai 400076, Maharashtra, India
| | - Gopalan Rajaraman
- Department of Chemistry, IIT Bombay, Powai 400076, Maharashtra, India
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Prakasham AP, Patil SK, Nettem C, Dey S, Rajaraman G, Ghosh P. Discrete Singular Metallophilic Interaction in Stable Large 12-Membered Binuclear Silver and Gold Metallamacrocycles of Amido-Functionalized Imidazole and 1,2,4-Triazole-Derived N-Heterocyclic Carbenes. ACS Omega 2023; 8:6439-6454. [PMID: 36844527 PMCID: PMC9947987 DOI: 10.1021/acsomega.2c06729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 01/31/2023] [Indexed: 06/18/2023]
Abstract
Metallophilic interactions were observed in four pairs of 12-membered metallamacrocyclic silver and gold complexes of imidazole-derived N-heterocyclic carbenes (NHCs), [1-(R1)-3-N-(2,6-di-(R2)-phenylacetamido)-imidazol-2-ylidene]2M2 [R1 = p-MeC6H4, R2 = Me, M = Ag (1b) and Au (1c); R1 = Me, R2 = i-Pr, M = Ag (2b) and Au (2c); R1 = Et, R2 = i-Pr, M = Ag (3b) and Au (3c)], and a 1,2,4-triazole-derived N-heterocyclic carbene (NHC), [1-(i-Pr)-4-N-(2,6-di-(i-Pr)-phenylacetamido)-1,2,4-triazol-2-ylidene]2M2 [M = Ag (4b) and Au (4c)]. The X-ray diffraction, photoluminescence, and computational studies indicate the presence of metallophilic interactions in these complexes, which are significantly influenced by the sterics and the electronics of the N-amido substituents of the NHC ligands. The argentophilic interaction in the silver 1b-4b complexes was stronger than the aurophilic interaction in the gold 1c-4c complexes, with the metallophilic interaction decreasing in the order 4b > 1b > 1c > 4c > 3b > 3c > 2b > 2c. The 1b-4b complexes were synthesized from the corresponding amido-functionalized imidazolium chloride 1a-3a and the 1,2,4-triazolium chloride 4a salts upon treatment with Ag2O. The reaction of 1b-4b complexes with (Me2S)AuCl gave the gold 1c-4c complexes.
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Jose R, Pal S, Rajaraman G. A Theoretical Perspective to Decipher the Origin of High Hydrogen Storage Capacity in Mn(II) Metal-Organic Framework. Chemphyschem 2023; 24:e202200257. [PMID: 36330697 DOI: 10.1002/cphc.202200257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 11/03/2022] [Indexed: 11/06/2022]
Abstract
Herein, we report a detailed periodic DFT investigation of Mn(II)-based [(Mn4 Cl)3 (BTT)8 ]3- (BTT3- =1,3,5-benzenetristetrazolate) metal-organic framework (MOF) to explore various hydrogen binding pockets, nature of MOF…H2 interactions, magnetic coupling and, H2 uptake capacity. Earlier experiments found an uptake capacity of 6.9 wt % of H2, with the heat of adsorption estimated to be ∼10 kJ/mol, which is one among the highest for any MOFs reported. Our calculations unveil different binding sites with computed binding energy varying from -6 to -15 kJ/mol. The binding of H2 at the Mn2+ site is found to be the strongest (site I), with H2 found to bind Mn2+ ion in a η2 fashion with a distance of 2.27 Å and binding energy of -15.4 kJ/mol. The bonding analysis performed using NBO and AIM reveal a strong donation of σ (H2 ) to the dz 2 orbital of the Mn2+ ion responsible for such large binding energy. The other binding pockets, such as -Cl (site II) and BTT ligands (site III and IV) were found to be weaker, with the binding energy decreasing in the order I>II>III>IV. The average binding energy computed for these four sites put together is 9.6 kJ/mol, which is in excellent agreement with the experimental value of ∼10 kJ/mol. We have expanded our calculations to compute binding energy for multiple sites simultaneously, and in this model, the binding energy per site was found to decrease as we increased the number of H2 molecules suggesting electronic and steric factors controlling the overall uptake capacity. The calculated adsorption isotherm using the GCMC method reproduces the experimental observations. Further, the magnetic coupling computed for the unbound MOF reveals moderate ferromagnetic and strong antiferromagnetic coupling within the tetrameric {Mn4 } unit leading to a three-up-one-down spin configuration as the ground state. These were then coupled ferromagnetically to other tetrameric units in the MOF network. The magnetic coupling was found to alter only marginally upon gas binding, suggesting that both exchange interaction and the spin-states are unlikely to play a role in the H2 uptake. This is contrary to the O2 uptake studied lately, where strong dependence on exchange-coupling/spin state was witnessed, suggesting exchange-coupling/magnetic field dependent binding as a viable route for gas separation.
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Affiliation(s)
- Reshma Jose
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Sourav Pal
- Department of Chemistry, Indian Institute of Science Education and Research, Kolkata, Mohanpur, Nadia, 741246, India.,Department of Chemistry, Ashoka University, Sonipat, Haryana, 131029, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
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Sen A, Rajaraman G. Does the Spin State and Oriented External Electric Field Boost the Efficiency of Fe(II) Pincer Catalyst toward CO 2 Hydrogenation Reaction? Inorg Chem 2023; 62:2342-2358. [PMID: 36689485 DOI: 10.1021/acs.inorgchem.2c04119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
In this study, we have explored the catalytic reactivities of four PNP-pincer supported Fe(II) complexes, namely, [(iPrPNMeP)FeH2(CO)] (1), [(iPrPNMeP)FeH(CO)(BH4)] (2), [(iPrPNHP)FeH2(CO)] (3), and [(iPrPNMeP)FeH(BH4)] (4) (iPrPNMeP = MeN{CH2CH2(PiPr2)}2 and iPrPNHP = HN{CH2CH2(PiPr2)}2) toward reductive CO2 hydrogenation for formate production. Our density functional theory and ab initio complete active space self-consistent field study have identified three fundamental steps in this catalytic transformation: (i) anchoring of the CO2 molecule in the vicinity of the metal using noncovalent interactions, (ii) catalyst regeneration via H2 cleavage, and (iii) formate rebound step leading to catalytic poisoning. The variations in the catalytic efficiency observed among these catalysts were attributed to either easing of steps (i) and (ii) or the hampering step (iii). This can be achieved in various chemical/non-chemical ways, for instance, (a) incorporation of strong-field ligands such as CO facilitating single-state reactivity and eliminating two-state reactivity that generally enhances the rate and (b) inclusion of Lewis acids such as LiOTf and strong bases found to either avoid catalytic poisoning or ease the H-H cleavages, to enhance the rate of reaction (c) evading mixing of excited open-shell singlet states to the ground closed-shell singlet state that hampers the catalytic regeneration. We have probed the role of oriented external electric fields (OEEFs) in the entire mechanistic profile for the best and worst catalyst, and our study suggests that imposing OEEFs opposite to the reaction axis (z-axis) fastens the catalytic regeneration step and, at the same time, hampers catalytic poisoning. The application of OEEFs is found to regulate the energetics of various spin states and can hamper two-state reactivity, therefore increasing the efficiency. Thus, this study provides insights into the CO2 hydrogenation mechanism where the role of bases/Lewis acid, ligand design, spin states, and electric field in a particular direction has been established and is, therefore, likely to pave the way forward for a new generation of catalysts.
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Affiliation(s)
- Asmita Sen
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai400076, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai400076, India
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Ansari M, Rajaraman G. Comparative oxidative ability of mononuclear and dinuclear high-valent iron-oxo species towards the activation of methane: does the axial/bridge atom modulate the reactivity? Dalton Trans 2023; 52:308-325. [PMID: 36504243 DOI: 10.1039/d2dt02559k] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Over the years, mononuclear FeIVO species have been extensively studied, but the presence of dinuclear FeIVO species in soluble methane monooxygenase (sMMO) has inspired the development of biomimic models that could activate inert substrates such as methane. There are some successful attempts; particularly the [(Por)(m-CBA) FeIV(μ-N)FeIV(O)(Por˙+)]- species has been reported to activate methane and yield decent catalytic turnover numbers and therefore regarded as the closest to the sMMO enzyme functional model, as no mononuclear FeIVO analogues could achieve this feat. In this work, we have studied a series of mono and dinuclear models using DFT and ab initio DLPNO-CCSD(T) calculations to probe the importance of nuclearity in enhancing the reactivity. We have probed the catalytic activities of four complexes: [(HO)FeIV(O)(Por)]- (1), [(HO)FeIV(O)(Por˙+)] (2), μ-oxo dinuclear iron species [(Por)(m-CBA)FeIV(μ-O)FeIV(O) (Por˙+)]- (3) and N-bridged dinuclear iron species [(Por)(m-CBA)FeIV(μ-N)FeIV(O)(Por˙+)]- (4) towards the activation of methane. Additionally, calculations were performed on the mononuclear models [(X)FeIV(O)(Por˙+)]n {X = N 4a (n = -2), NH 4b (n = -1) and NH24c (n = 0)} to understand the role of nuclearity in the reactivity. DFT calculations performed on species 1-4 suggest an interesting variation among them, with species 1-3 possessing an intermediate spin (S = 1) as a ground state and species 4 possessing a high-spin (S = 2) as a ground state. Furthermore, the two FeIV centres in species 3 and 4 are antiferromagnetically coupled, yielding a singlet state with a distinct difference in their electronic structure. On the other hand, species 2 exhibits a ferromagnetic coupling between the FeIV and the Por˙+ moiety. Our calculations suggest that the higher barriers for the C-H bond activation of methane and the rebound step for species 1 and 3 are very high in energy, rendering them unreactive towards methane, while species 2 and 4 have lower barriers, suggesting their reactivity towards methane. Studies on the system reveal that model 4a has multiple FeN bonds facilitating greater reactivity, whereas the other two models have longer Fe-N bonds and less radical character with steeper barriers. Strong electronic cooperativity is found to be facilitated by the bridging nitride atom, and this cooperativity is suppressed by substituents such as oxygen, rendering them inactive. Thus, our study unravels that apart from enhancing the nuclearity, bridging atoms that facilitate strong cooperation between the metals are required to activate very inert substrates such as methane, and our results are broadly in agreement with earlier experimental findings.
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Affiliation(s)
- Mursaleem Ansari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India.
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India.
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Jose R, Bangar G, Pal S, Rajaraman G. Role of molecular modelling in the development of metal-organic framework for gas adsorption applications. J CHEM SCI 2023; 135:19. [PMID: 36938494 PMCID: PMC10011768 DOI: 10.1007/s12039-022-02130-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 10/31/2022] [Accepted: 12/28/2022] [Indexed: 03/21/2023]
Abstract
More than 47,000 articles have been published in the area of Metal-Organic Framework since its seminal discovery in 1995, exemplifying the intense research carried out in this short span of time. Among other applications, gas adsorption and storage are perceived as central to the MOFs research, and more than 10,000 MOFs structures are reported to date to utilize them for various gas storage/separation applications. Molecular modeling, particularly based on density functional theory, played a key role in (i) understanding the nature of interactions between the gas and the MOFs geometry (ii) establishing various binding pockets and relative binding energies, and (iii) offering design clues to improve the gas uptake capacity of existing MOF architectures. In this review, we have looked at various MOFs that are studied thoroughly using DFT/periodic DFT (pDFT) methods for CO2, H2, O2, and CH4 gases to provide a birds-eye-view on how various exchange-correlation functionals perform in estimating the binding energy for various gases and how factors such as nature of the (i) metal ion, (ii) linkers, (iii) ligand, (iv) spin state and (v) spin-couplings play a role in this process with selected examples. While there is still room for improvement, the rewards offered by the molecular modelling of MOFs were already substantial that we advocate experimental and theoretical studies to go hand-in-hand to undercut the trial-and-error approach that is often perceived in the selection of MOFs and gas partners in this area. Graphical abstract The importance of density functional theory-based molecular modeling studies in offering design clues to improve the gas adsorption and storage capacity of existing MOF architectures is discussed here. The use of DFT-based investigation in conjunction with experimental synthesis is an imperative tool in designing new-generation MOFs with enhanced uptake capacity.
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Affiliation(s)
- Reshma Jose
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076 India
| | - Garima Bangar
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076 India
| | - Sourav Pal
- Department of Chemistry, Ashoka University, Sonepat, Haryana 131029 India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076 India
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Arumugam GS, Sen A, Dash SS, Mitra K, Doble M, Rajaraman G, Gummadi SN. Arjunetin as a promising drug candidate against SARS-CoV-2: molecular dynamics simulation studies. J Biomol Struct Dyn 2022; 40:12358-12379. [PMID: 34533107 PMCID: PMC8459932 DOI: 10.1080/07391102.2021.1970627] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Stem and bark of the tree Terminalia arjuna Wight & Arn. (Combretaceae) has been documented to exhibit therapeutic properties like cardiotonic, anticancer, antiviral, antibacterial, antifungal, hypercholesterolemia, hypolipidemic, and anti-coagulant. Our previous studies have shown that, ethanolic extract of T. arjuna bark exhibits radical scavenging anti-oxidant activity and also effectively inhibited catalase activity. In this study, oleanane triterpenoids type compounds viz., oleanolic acid, arjunolic acid, arjunolitin, arjunetin were isolated from ethanolic bark extract as bio-active compound and their structures were elucidated using 1H, 13C NMR, HR-ESIMS, IR. Of the various compounds, Arjunetin showed significant inhibition of catalase activity as compared to the other compounds. Based on the structural similarity between arjunetin and current antiviral drugs, we propose that arjunetin might exhibit antiviral activity. Molecular docking and molecular dynamics studies showed that arjunetin binds to the binds to key targets of SARS-CoV-2 namely, 3CLpro, PLpro, and RdRp) with a higher binding energy values (3CLpro, -8.4 kcal/mol; PLpro, -7.6 kcal/mol and RdRp, -8.1 kcal/mol) as compared with FDA approved protease inhibitor drugs to Lopinavir (3CLpro, -7.2 kcal/mole and PLpro -7.7 kcal/mole) and Remdesivir (RdRp -7.6 kcal/mole). To further investigate this, we performed 200-500 ns molecular dynamics simulation studies. The results transpired that the binding affinity of Arjunetin is higher than Remdesivir in the RNA binding cavity of RdRp. Based on structural similarity between arjunetin and Saikosaponin (a known antiviral agents) and based on our molecular docking and molecular dynamic simulation studies, we propose that arjunetin can be a promising drug candidate against Covid-19.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Gandarvakottai Senthilkumar Arumugam
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Applied and Industrial Microbiology Laboratory, Indian Institute of Technology Madras, Chennai, India
| | - Asmita Sen
- Department of Chemistry, Molecular Modelling Group (MMG), Indian Institute of Technology Bombay, Powai, Mumbai, India
| | - Swati S. Dash
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Applied and Industrial Microbiology Laboratory, Indian Institute of Technology Madras, Chennai, India
| | - Kartik Mitra
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Drug Design Laboratory, Indian Institute of Technology Madras, Chennai, India
| | - Mukesh Doble
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Drug Design Laboratory, Indian Institute of Technology Madras, Chennai, India
| | - Gopalan Rajaraman
- Department of Chemistry, Molecular Modelling Group (MMG), Indian Institute of Technology Bombay, Powai, Mumbai, India,Rajaraman Gopalan Department of Chemistry, Molecular Modelling Group (MMG), Indian Institute of Technology Bombay, Powai, Mumbai400076, India
| | - Sathyanarayana N. Gummadi
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Applied and Industrial Microbiology Laboratory, Indian Institute of Technology Madras, Chennai, India,CONTACT Sathyanarayana N. Gummadi Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Applied and Industrial Microbiology Laboratory, Indian Institute of Technology Madras, Chennai, 600 036, India;
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Kumar A, Ta S, Nettem C, Tanski JM, Rajaraman G, Ghosh P. One pot tandem dehydrogenative cross-coupling of primary and secondary alcohols by ruthenium amido-functionalized 1,2,4-triazole derived N-heterocyclic carbene complexes. RSC Adv 2022; 12:28961-28984. [PMID: 36320780 PMCID: PMC9557752 DOI: 10.1039/d2ra05531g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 09/29/2022] [Indexed: 11/05/2022] Open
Abstract
One-pot tandem dehydrogenative cross-coupling of primary and secondary alcohols was catalyzed by three ruthenium complexes [1-(R)-4-N-(furan-2-ylmethyl)acetamido-1,2,4-triazol-5-ylidene]Ru(p-cymene)Cl [R = Et (1b), i-Pr (2b), Bn (3b)], of amido-functionalized 1,2,4-triazole derived N-heterocyclic carbene (NHC) ligands. Density Functional Theory (DFT) calculations were employed for the ruthenium (1b) precatalyst to understand this reaction mechanism completely, and the mechanisms adapted are divided categorically into three steps (i) nucleophilic substitution of chloride ions by alcohols, (ii) dehydrogenation of primary and secondary alcohols, and (iii) olefin and ketone hydrogenation. Our mechanistic study reveals that the formation of a deprotonated Ru-alcoholate (A) or (E) intermediate is favorable compared to the protonated form (A') or (E') from (1b) by associative nucleophilic substitution. Though an ionic pathway that proceeds through (A') or (E'), has less barriers in the dehydrogenation and olefin/ketone hydrogenation steps than that of the neutral pathway, proceeding through (A) or (E), a steep energy barrier was observed in the first nucleophilic substitution step, prohibiting the reaction to proceed via the intermediate (A') or (E'). Thus, our thorough mechanistic study reveals that the reaction proceeds via deprotonated Ru-alcoholate (A) or (E) species. Furthermore, the 1,4 addition of an α,β-unsaturated carbonyl compound is kinetically and thermodynamically favorable over the 1,2 addition, and the experiments support these observations. As a testimony towards practical application in synthesizing bio-active flavonoid based natural products, five different flavan derivatives (16-20), were synthesized by the dehydrogenative coupling reaction using the neutral ruthenium (1-3)b complexes.
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Affiliation(s)
- Anuj Kumar
- Department of Chemistry, Indian Institute of Technology BombayPowaiMumbai 400 076India+91 22 2572 3480
| | - Sabyasachi Ta
- Department of Chemistry, Indian Institute of Technology BombayPowaiMumbai 400 076India+91 22 2572 3480
| | - Chandrasekhar Nettem
- Department of Chemistry, Indian Institute of Technology BombayPowaiMumbai 400 076India+91 22 2572 3480
| | - Joseph M. Tanski
- Department of Chemistry, Vassar College124 Raymond AvenuePoughkeepsieNY12604USA
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology BombayPowaiMumbai 400 076India+91 22 2572 3480
| | - Prasenjit Ghosh
- Department of Chemistry, Indian Institute of Technology BombayPowaiMumbai 400 076India+91 22 2572 3480
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Mandal S, Pramanik A, Dey S, Carrella LM, Rajaraman G, Rentschler E, Mohanta S. Experimental and theoretical investigations on three Dy III4 single molecule magnets: structural and magneto-structural correlations. Dalton Trans 2022; 51:14753-14766. [PMID: 36106563 DOI: 10.1039/d2dt02348b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The work in this report describes the syntheses, crystal structures, dc/ac magnetic behaviour, and theoretical calculations (both ab initio CASSCF and DFT) of three defect dicubane/planar butterfly type tetradysprosium(III) compounds of compositions [DyIII4L4(μ3-OH)2(carboxylate)2(dmf)2] (carboxylate = formate (1), acetate (2), propionate (3)), where H2L = 2-(2-hydroxy-3-ethoxybenzylideneamino)phenol. In the butterfly type structures, two DyIII centres (Dyb) occupy the body positions while two other (Dyw) units occupy the wing positions. SHAPE analyses reveal that the coordination geometries of the Dyb and Dyw centres, both octacoordinated, are triangular dodecahedron (TDD) and square antiprism (SAPR), respectively. Variable-temperature magnetic susceptibility measurements give an indication of weak antiferromagnetic interactions and variable-field magnetization measurements reveal strong anisotropy in all the three compounds. The variable-temperature/frequency in-phase/out-of-phase AC susceptibility data reveal that all these three compounds are SMMs with two relaxation channels under zero dc field; slow relaxation (SR) and fast relaxation (FR) processes could be assigned to the SAPR (Dyw) and TDD (Dyb) metal centres, respectively. The simulated Ueff and τ0 values are: 49.0 cm-1 and 1.76 × 10-7 s for 1, 30.3 cm-1 and 1.51 × 10-8 s for 2 and 23.4 cm-1 and 9.64 × 10-7 s for 3. Furthermore, ab initio CASSCF/RASSI-SO/SINGLE_ANISO calculations reveal that the ground state of DyIII centres are axial in nature with a dominating contribution from mJ = |±15/2>. The magnetization relaxation occurs via the first excited KD resulting in the large computed blocking barrier of Dyw (SAPR) centres compared to that of the Dyb (TDD) centres which corroborates the experimental measurements. The exchange parameters obtained from DFT calculations are generally in line with those obtained from the fitting of χMT vs. T in POLY_ANISO calculations. Interesting structural and magneto-structural correlations have been found, which are the major outcomes of this investigation.
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Affiliation(s)
- Shuvankar Mandal
- Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India.
| | - Abhishek Pramanik
- Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India.
| | - Sourav Dey
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
| | - Luca M Carrella
- Department of Chemistry, Johannes-Gutenberg University Mainz, Duesbergweg 10-14, D-55128 Mainz, Germany.
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
| | - Eva Rentschler
- Department of Chemistry, Johannes-Gutenberg University Mainz, Duesbergweg 10-14, D-55128 Mainz, Germany.
| | - Sasankasekhar Mohanta
- Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India.
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Dey S, Rajaraman G, Bolvin H. Analysis of the magnetic coupling in a Mn(II)‐U(V)‐Mn(II) Single Molecule Magnet. Chemistry 2022; 28:e202201883. [PMID: 36005891 PMCID: PMC10092672 DOI: 10.1002/chem.202201883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Indexed: 11/10/2022]
Abstract
[{Mn(TPA)I}{UO2(Mesaldien)}{Mn(TPA)I}]I formula (here TPA=tris(2-pyridylmethyl)amine and Mesaldien=N,N'-(2-aminomethyl)diethylenebis(salicylidene imine)) reported by Mazzanti and coworkers (Chatelain et al. Angew. Chem. Int. Ed. 2014, 53, 13434) is so far the best Single Molecule Magnet (SMM) in the {3d-5f} class of molecules exhibiting barrier height of magnetization reversal as high as 81.0 K. In this work, we have employed a combination of ab initio CAS and DFT methods to fully characterize this compound and to extract the relevant spin Hamiltonian parameters. We show that the signs of the magnetic coupling and of the g-factors of the monomers are interconnected. The central magnetic unit [UV O2 ]+ is described by a Kramers Doublet (KD) with negative g-factors, due to a large orbital contribution. The magnetic coupling for the {Mn(II)-U(V)} pair is modeled by an anisotropic exchange Hamiltonian: all components are ferromagnetic in terms of spin moments, the parallel component JZ twice larger as the perpendicular one J⊥ . The spin density distribution suggests that spin polarization on the U(V) center favors the ferromagnetic coupling. Further, the JZ /J⊥ ratio, which is related to the barrier height, was found to correlate to the corresponding spin contribution of the g-factors of the U(V) center. This correlation established for the first time offers a direct way to estimate this important ratio from the corresponding gS -values, which can be obtained using traditional ab initio packages and hence has a wider application to other {3d-5f} magnets. It is finally shown that the magnetization barrier height is tuned by the splitting of the [UV O2 ]+ 5 f orbitals.
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Affiliation(s)
- Sourav Dey
- IIT Bombay: Indian Institute of Technology Bombay of chemistry INDIA
| | - Gopalan Rajaraman
- IIT Bombay: Indian Institute of Technology Bombay of chemistry INDIA
| | - Hélène Bolvin
- Université de Toulouse III Laboratoire de Chimie et de Physique Quantiques 118 route de Narbonne 31400 Toulouse FRANCE
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Kumar P, Swain A, Acharya J, Li Y, Kumar V, Rajaraman G, Colacio E, Chandrasekhar V. Synthesis, Structure, and Zero-Field SMM Behavior of Homometallic Dy2, Dy4, and Dy6 Complexes. Inorg Chem 2022; 61:11600-11621. [PMID: 35849822 DOI: 10.1021/acs.inorgchem.2c01041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The synthesis, structure, and magnetic properties of three DyIII complexes of different nuclearity, [Dy2(H2L)2(NO3)] [NO3]·2H2O·CH3OH (1), [Dy4(HL)2(piv)4(OH)2] (2), and [Dy6(H2L)3(μ3-OH)(μ3-CO3)3(CH3OH)4(H2O)8] 5Cl·3H2O (3) [(H4L) = 6-((bis(2-hydroxyethyl)amino)-N'-(2-hydroxybenzylidene)picolinohydrazide)], are described. This variety of complexes with the same ligand could be obtained by playing with the metal-to-ligand molar ratio, the type of DyIII salt, the kind of base, and the presence/absence of coligand. 1 is a dinuclear complex, while 2 is a tetranuclear assembly with a butterfly-shaped topology. 3 is a homometallic hexanuclear complex that exhibits a propeller-shaped topology. Interestingly, in this complex 3, three atmospheric carbon dioxide molecules are trapped in the form of carbonate ions, which assist in holding the hexanuclear complex together. All of the complexes reveal a slow relaxation of magnetization even in zero applied field. Complex 1 is a zero-field SMM with an effective energy barrier (Ueff) of magnetization reversal equal to 87(1) K and a relaxation time of τ0 = 6.4(3) × 10-9 s. Under an applied magnetic field of 0.1 T, these parameters change to Ueff = 101(3) K, τ0 = 2.5(1) × 10-9 s. Complex 2 shows zero-field SMM behavior with Ueff = 31(2) K, τ0 = 4.2(1) × 10-7 s or τ01 = 2(1) × 10-7 s, Ueff1 = 37(8) K, τ02 = 5(6) × 10-5 s, and Ueff2 = 8(4) by considering two Orbach relaxation processes, while 3, also a zero-field SMM, shows a double relaxation of magnetization [Ueff1 = 62.4(3) K, τ01 = 4.6(3) × 10-8 s, and Ueff1 = 2(1) K, τ02 = 4.6(2) × 10-5 s]. The ab initio calculations indicated that in these complexes, the Kramer's ground doublet is characterized by an axial g-tensor with the prevalence of the mJ = ±15/2 component, as well as that due to the weak magnetic coupling between the metal centers, the magnetic relaxation, which is dominated by the single DyIII centers rather than by the exchange-coupled states, takes place via Raman/Orbach or TA-QTM. Moreover, theoretical calculations support a toroidal magnetic state for complex 2.
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Affiliation(s)
- Pawan Kumar
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Abinash Swain
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Joydev Acharya
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Yanling Li
- Sorbonne Universit Institut Parisien de Chimie Molculaire, CNRS UMR 8232, 4 place Jussieu, 75252 Paris cedex 5, France
| | - Vierandra Kumar
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Enrique Colacio
- Department of Inorganic Chemistry, University of Granada, 18071 Granada, Spain
| | - Vadapalli Chandrasekhar
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India.,Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500 107, India
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Regincós Martí E, Canaj AB, Sharma T, Celmina A, Wilson C, Rajaraman G, Murrie M. Importance of an Axial Ln III-F Bond across the Lanthanide Series and Single-Molecule Magnet Behavior in the Ce and Nd Analogues. Inorg Chem 2022; 61:9906-9917. [PMID: 35727882 PMCID: PMC9275778 DOI: 10.1021/acs.inorgchem.2c00556] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
The recently reported
compound [DyIIILF](CF3SO3)2·H2O (L = 1,4,7,10-tetrakis(2-pyridylmethyl)-1,4,7,10-tetraaza-cyclododecane)
displays a strong axial magnetic anisotropy, due to the short axial
Dy–F bond, and single-molecule magnet (SMM) behavior. Following
our earlier [DyIIILF]2+ work, herein we report
the systematic structural and magnetic study of a family of [LnIIILF](CF3SO3)2·H2O compounds (Ln(III) = 1-Ce, 2-Pr, 3-Nd, 4-Eu, 5-Tb, 6-Ho, 7-Er, 8-Tm, and 9-Yb).
From this series, the Ce(III) and Nd(III) analogues show slow relaxation
of the magnetization under an applied direct current magnetic field,
which is modeled using a Raman process. Complete active space self-consistent
field theoretical calculations are employed to understand the relaxation
pathways in 1-Ce and 3-Nd and also reveal
a large tunnel splitting for 5-Tb. Additional computational
studies on model compounds where we remove the axial F– ligand, or replace F– with I–, highlight the importance of the F– ligand in
creating a strong axial crystal field for 1-Ce and 3-Nd and for promoting the SMM behavior. Importantly, this
systematic study provides insight into the magnetic properties of
these lighter lanthanide ions. The
structural and magnetic properties of a family of [LnIIILF](CF3SO3)2·H2O
(L = 1,4,7,10-tetrakis(2-pyridylmethyl)-1,4,7,10-tetraaza-cyclododecane)
compounds are reported. In addition to the previously reported Dy(III)
analogue, we find that the Ce(III) and Nd(III) analogues show slow
relaxation of the magnetization due to the strong axial magnetic anisotropy
created by the axial F− ligand. AC magnetic susceptibility
data and CASSCF theoretical calculations are employed to understand
the single-molecule magnet behavior of 1-Ce and 3-Nd.
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Affiliation(s)
- Emma Regincós Martí
- School of Chemistry, University of Glasgow, University Avenue, Glasgow G12 8QQ, U.K
| | - Angelos B Canaj
- School of Chemistry, University of Glasgow, University Avenue, Glasgow G12 8QQ, U.K
| | - Tanu Sharma
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India
| | - Anna Celmina
- School of Chemistry, University of Glasgow, University Avenue, Glasgow G12 8QQ, U.K
| | - Claire Wilson
- School of Chemistry, University of Glasgow, University Avenue, Glasgow G12 8QQ, U.K
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India
| | - Mark Murrie
- School of Chemistry, University of Glasgow, University Avenue, Glasgow G12 8QQ, U.K
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Hansen HB, Krzystek J, Telser J, Swain A, Rajaraman G, Wadepohl H, Enders M. Solid-State Conformational Isomerism Lacking a Gas-Phase Energy Barrier: Its Structural, Spectroscopic, and Theoretical Identification in an Organochromium(III) Complex. Organometallics 2022. [DOI: 10.1021/acs.organomet.2c00182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Helge-Boj Hansen
- Institute of Inorganic Chemistry, Heidelberg University, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
| | - J. Krzystek
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
| | - Joshua Telser
- Department of Biological, Physical, and Health Sciences, Roosevelt University, Chicago, Illinois 60605, United States
| | - Abinash Swain
- Institute of Inorganic Chemistry, Heidelberg University, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Hubert Wadepohl
- Institute of Inorganic Chemistry, Heidelberg University, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
| | - Markus Enders
- Institute of Inorganic Chemistry, Heidelberg University, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
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28
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Dey S, Rajaraman G. In silico design criteria for high blocking barrier uranium (III) SIMs. Chem Commun (Camb) 2022; 58:6817-6820. [PMID: 35615940 DOI: 10.1039/d2cc01356h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A combination of DFT and ab initio CASSCF/PT2 calculations on U(III) fictitious models and numerous reported X-ray structures unveils several geometries from coordination number 1 to 12 that can be targeted to design potential U(III) SIMs with attractive barrier heights. Among the geometries studied, the T-shaped and capped pentagonal antiprism geometries yield values exceeding 1500 cm-1 - a value that is elusive for any uranium SIMs.
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Affiliation(s)
- Sourav Dey
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
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29
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Anilkumar A, Ash P, Chakravarty AR, Comba P, DeBeer S, Dey A, Draksharapu A, Goswami D, Itoh S, Karlin K, Lakshmi KV, Mazumdar S, Pantazis D, Parker D, Que L, Rajaraman G, Rath SP, Sastri C, Sen Gupta S, Solomon EI. Electron transfer, spectroscopy and theory: general discussion. Faraday Discuss 2022; 234:245-263. [PMID: 35510729 DOI: 10.1039/d2fd90013k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Jiang Y, Dey S, Ke H, Yang Y, Sun L, Xie G, Chen S, Rajaraman G. Steric hindrance effect of Schiff-base ligands on magnetic relaxation dynamics and emissive behavior of two dinuclear dysprosium complexes. J RARE EARTH 2022. [DOI: 10.1016/j.jre.2022.04.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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31
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Ahmed N, Sharma T, Spillecke L, Koo C, Ansari KU, Tripathi S, Caneschi A, Klingeler R, Rajaraman G, Shanmugam M. Probing the Origin of Ferro-/Antiferromagnetic Exchange Interactions in Cu(II)–4f Complexes. Inorg Chem 2022; 61:5572-5587. [DOI: 10.1021/acs.inorgchem.2c00065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Naushad Ahmed
- Department of Chemistry, Indian Institute of Technology Bombay Powai, Mumbai 400076, Maharashtra, India
| | - Tanu Sharma
- Department of Chemistry, Indian Institute of Technology Bombay Powai, Mumbai 400076, Maharashtra, India
| | - Lena Spillecke
- Kirchhoff Institute for Physics, Heidelberg University, 69120 Heidelberg, Germany
| | - Changhyun Koo
- Kirchhoff Institute for Physics, Heidelberg University, 69120 Heidelberg, Germany
| | - Kamal Uddin Ansari
- Department of Chemistry, Indian Institute of Technology Bombay Powai, Mumbai 400076, Maharashtra, India
| | - Shalini Tripathi
- Department of Chemistry, Indian Institute of Technology Bombay Powai, Mumbai 400076, Maharashtra, India
| | - Andrea Caneschi
- Department of Industrial Engineering, “DIEF” and INSTM RU, University of Florence, Via di S. Marta 3, 50131 Florence, Italy
| | - Rüdiger Klingeler
- Kirchhoff Institute for Physics, Heidelberg University, 69120 Heidelberg, Germany
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay Powai, Mumbai 400076, Maharashtra, India
| | - Maheswaran Shanmugam
- Department of Chemistry, Indian Institute of Technology Bombay Powai, Mumbai 400076, Maharashtra, India
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32
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Comba P, Rajaraman G, Sarkar A, Velmurugan G. What controls the magnetic anisotropy in heptacoordinate high-spin cobalt(II) complexes? A theoretical perspective. Dalton Trans 2022; 51:5175-5183. [PMID: 35274660 DOI: 10.1039/d1dt03903b] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The magnetic anisotropy of sixteen seven-coordinate high-spin CoII complexes with O, N, Cl and I donors was investigated with state-of-the-art ab initio CASSCF/NEVPT2 calculations and compared with experimental data. Based on the nature of the equatorial and axial ligands, which were found to tune the zero-field splitting, the complexes were classified into four groups. The experimental zero-field splitting parameters D which, for the various structures are in a range of +30 to +60 cm-1, as well as the g and E values are well reproduced. The investigation of the electronic structure shows that in these pentagonal bipyramidal complexes the donors and symmetry in the equatorial plane play an important role in the values of the axial zero-field splitting parameter D, and breaking of the horizontal plane of symmetry was found to enhance the magnitude of the D value. Although negative values of D are a desired condition for SIMs, many CoII based SIMs with positive zero-field splitting are fundamentally important to understand the nature of magnetic anisotropy, and seven coordinate CoII complexes with a large overall crystal field splitting might provide a way forward in this class of molecules.
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Affiliation(s)
- Peter Comba
- Heidelberg University, Institute of Inorganic Chemistry and Interdisciplinary Center for Scientific Computing, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
| | - Arup Sarkar
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
| | - Gunasekaran Velmurugan
- Heidelberg University, Institute of Inorganic Chemistry and Interdisciplinary Center for Scientific Computing, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
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33
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Jose R, Kancharlapalli S, Ghanty TK, Pal S, Rajaraman G. The Decisive Role of Spin States and Spin Coupling in Dictating Selective O
2
Adsorption in Chromium(II) Metal–Organic Frameworks**. Chemistry 2022; 28:e202104526. [DOI: 10.1002/chem.202104526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Indexed: 11/06/2022]
Affiliation(s)
- Reshma Jose
- Department of Chemistry Indian Institute of Technology Bombay Powai, Mumbai 400076 India
| | | | - Tapan K. Ghanty
- Theoretical Chemistry Section Bhabha Atomic Research Centre Mumbai 400085 India
- Present address: Bio-Science Group Bhabha Atomic Research Centre Mumbai 400085 India
| | - Sourav Pal
- Department of Chemistry Indian Institute of Science Education and Research Kolkata, Mohanpur Nadia 741246 India
- Department of Chemistry Ashoka University Sonepat, Haryana 131029 India
| | - Gopalan Rajaraman
- Department of Chemistry Indian Institute of Technology Bombay Powai, Mumbai 400076 India
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Jose R, Kancharlapalli S, Ghanty TK, Pal S, Rajaraman G. Front Cover: The Decisive Role of Spin States and Spin Coupling in Dictating Selective O
2
Adsorption in Chromium(II) Metal–Organic Frameworks (Chem. Eur. J. 18/2022). Chemistry 2022. [DOI: 10.1002/chem.202200660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Reshma Jose
- Department of Chemistry Indian Institute of Technology Bombay Powai, Mumbai 400076 India
| | | | - Tapan K. Ghanty
- Theoretical Chemistry Section Bhabha Atomic Research Centre Mumbai 400085 India
- Present address: Bio-Science Group Bhabha Atomic Research Centre Mumbai 400085 India
| | - Sourav Pal
- Department of Chemistry Indian Institute of Science Education and Research Kolkata, Mohanpur Nadia 741246 India
- Department of Chemistry Ashoka University Sonepat, Haryana 131029 India
| | - Gopalan Rajaraman
- Department of Chemistry Indian Institute of Technology Bombay Powai, Mumbai 400076 India
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35
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Dwivedi I, Sarkar A, Rajaraman G, Subramaniam C. Electric-Field-Induced Solid-Gas Interfacial Chemical Reaction in Carbon Nanotube Ensembles: Route toward Ultra-sensitive Gas Detectors. ACS Appl Mater Interfaces 2022; 14:13271-13279. [PMID: 35266685 DOI: 10.1021/acsami.1c23670] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The electric field at the sharp pointed tips of single wall carbon nanotube ensembles has been utilized to kinetically accelerate hitherto unobserved chemical reactions at the heterogeneous solid-gas interfaces. The principle of ″action-of-points″ drives specific chemical reactions between the defect sites of single wall carbon nanotubes (CNTs) and ppb levels of gaseous hydrogen sulfide. This is manifested as changes in the electrical conductivity of the conductive CNT-ensemble (cCNT) and visually tracked as enthalpic modulations at the site of the reaction through infrared thermometry. Importantly, the principle has been observed for a variety of analytes such as NH3, H2O, and H2S, leading to distinctly correlatable changes in reactivity and conductivity changes. Theoretical calculations based on the density functional theory in the presence and absence of applied electric field reveal that the applied electric field activates the H2S gas molecules by charge polarization, yielding favorable energetics. These results imply the possibility of carrying out site-specific chemical modifications for nanomaterials and also provide transformative opportunities for the development of miniaturized e-nose-based gas analyzers.
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Affiliation(s)
- Itisha Dwivedi
- Department of Chemistry, Indian Institution of Technology Bombay, Powai, Mumbai 400076, Maharashtra, India
| | - Arup Sarkar
- Department of Chemistry, Indian Institution of Technology Bombay, Powai, Mumbai 400076, Maharashtra, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institution of Technology Bombay, Powai, Mumbai 400076, Maharashtra, India
| | - Chandramouli Subramaniam
- Department of Chemistry, Indian Institution of Technology Bombay, Powai, Mumbai 400076, Maharashtra, India
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Abstract
The concept of the "oxo-wall" was conceived about 60 years ago by Harry B. Gray, and has been found to be related to the non-existence of high-valent M-oxo species in the +IV oxidation state in a tetragonal geometry beyond group 8 in the periodic table. Several efforts have been made in the past decades to test and find examples that violate this theory. Several claims of violation in the past were attributed to the difference in the geometries/coordination number and, therefore, these are not examples of true violation. In recent years, substantial efforts have been undertaken to synthesise a true CoIVO species with various ligand architectures. CoIVO and CoIII-O˙ are electromers and, while they are interchangeably used in the literature; the former violates the oxo-wall while the latter does not. The possibility that these two species could exist in various proportions similar to resonating structures has not been considered in detail in this area. Furthermore, there have been no attempts to quantify such mixing. In this direction, we have employed density functional theory (DFT) and ab initio CASSCF/NEVPT2 methods to quantify the co-existence of CoIVO and CoIII-O˙ isomeric species. By thoroughly studying six different metal-oxo species, we affirm that the nature of such electromeric mixing is minimal/negligible for FeIVO and MnIVO species - both are pre-oxo-wall examples. By studying four different ligand architectures with Co-oxo species, our results unveil that the mixing of CoIVO ↔ CoIII-O˙ is substantial in all geometries, with dominant CoIVO species favourable for the S = 3/2 intermediate spin state. The percentage of the CoIII-O˙ species is enhanced substantially for the S = 1/2 low-spin state. We have attempted to develop a tool to estimate the percentage of the CoIII-O˙ species using various structural parameters. Among those tested, a linear relationship between % of CoIII-O˙ and a bond length based ratio is found (, where d(Co-O) and d(Co-Nax) are the axial Co-O and Co-Nax bond lengths in Å, respectively). It is found that the higher the Rd, the greater the CoIII-O˙ character will be and the geometrically portable correlation developed offers a way to qualitatively compute the % of CoIII-O˙ character for unknown geometries.
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Affiliation(s)
- Asmita Sen
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, 400076, India.
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, 400076, India.
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Saha S, Das KS, Sharma T, Bala S, Adhikary A, Huang GZ, Tong ML, Ghosh A, Das B, Rajaraman G, Mondal R. Synergistic Experimental and Theoretical Studies of Luminescent-Magnetic Ln 2Zn 6 Clusters. Inorg Chem 2022; 61:2141-2153. [PMID: 35049278 DOI: 10.1021/acs.inorgchem.1c03359] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The present work is part of our ongoing quest for developing functional inorganic complexes using unorthodox pyridyl-pyrazolyl-based ligands. Accordingly, we report herein the synthesis, characterization, and luminescence and magnetic properties of four 3d-4f mixed-metal complexes with a general core of Ln2Zn6 (Ln = Dy, Gd, Tb, and Eu). In stark contrast to the popular wisdom of using a compartmental ligand with separate islands of hard and soft coordinating sites for selective coordination, we have vindicated our approach of using a ligand with overcrowded N-coordinating sites that show equal efficiency with both 4f and 3d metals toward multinuclear cage-cluster formation. The encouraging red and green photolumiscent features of noncytotoxic Eu2Zn6 and Tb2Zn6 complexes along with their existence in nanoscale dimension have been exploited with live-cell confocal microscopy imaging of human breast adenocarcinoma (MCF7) cells. The magnetic features of the Dy2Zn6 complex confirm the single-molecule-magnet behavior with befitting frequency- and temperature-dependent out-of-phase signals along with an Ueff value of ∼5 K and a relaxation time of 8.52 × 10-6 s. The Gd2Zn6 complex, on the other hand, shows cryogenic magnetic refrigeration with an entropy change of 11.25 J kg-1 K-1 at a magnetic field of 7 T and at 2 K. Another important aspect of this work reflects the excellent agreement between the experimental results and theoretical calculations. The theoretical studies carried out using the broken-symmetry density functional theory, ORCA suite of programs, and MOLCAS calculations using the complete-active-space self-consistent-field method show an excellent synergism with the experimentally measured magnetic and spectroscopic data.
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Affiliation(s)
- Sayan Saha
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Kolkata 700032, West Bengal, India
| | - Krishna Sundar Das
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Kolkata 700032, West Bengal, India
| | - Tanu Sharma
- Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, Maharashtra, India
| | - Sukhen Bala
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Kolkata 700032, West Bengal, India
| | - Amit Adhikary
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Kolkata 700032, West Bengal, India
| | - Guo-Zhang Huang
- Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, P. R. China
| | - Ming-Liang Tong
- Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, P. R. China
| | - Arjit Ghosh
- School of Biological Science Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Kolkata 700032, West Bengal, India
| | - Benubrata Das
- School of Biological Science Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Kolkata 700032, West Bengal, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, Maharashtra, India
| | - Raju Mondal
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Kolkata 700032, West Bengal, India
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Lalioti N, Nastopoulos V, Panagiotou N, Tasiopoulos A, Ioannidis N, van Slageren J, Zhang P, Rajaraman G, Swain A, Tangoulis V. A nonsymmetric Dy 2 single-molecule magnet with two relaxation processes triggered by an external magnetic field: a theoretical and integrated EPR study of the role of magnetic-site dilution. Dalton Trans 2022; 51:1985-1994. [PMID: 35029246 DOI: 10.1039/d1dt04089h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The 1 : 2 reaction between Dy(O2CMe)3·4H2O and 1-acetyl-2-napthol (LH) in MeOH has provided access to the complex [Dy2L6(MeOH)]·MeOH (1·MeOH) in a good yield. The structures of the isomorphous complex 1·MeOH and its doped diamagnetic yttrium analogue [Dy0.14Y1.86L6(MeOH)]·MeOH (Dy@Y2) have been determined by single-crystal X-ray crystallography and characterized based on elemental analyses, IR spectra, and powder X-ray patterns. Combined dc and ac magnetic susceptibility and the magnetization data for 1 suggest that this complex shows slow magnetic relaxation. Under a 0 Oe dc field, a single relaxation mechanism is seen while two magnetization relaxation processes are evident under a 1500 G external magnetic field. The fit to the Arrhenius law has been performed using the 1.8-10 K ac data, affording an effective barrier for the magnetization reversal of 13 K and 7 K under the external dc field. Theoretical studies have been performed using ab initio and density functional methodologies to understand the electronic structure and the magnetic relaxation dynamics resulting from the single DyIII ion as well as from the dinuclear exchange-coupled states. Rich powder EPR spectra at the X-band and Q-band were obtained from Dy@Y2, as well as from the 1·MeOH dimer, while simulation studies revealed the ferromagnetic nature of the interaction between the DyIII ions in accordance with theoretical studies.
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Affiliation(s)
- Nikolia Lalioti
- Department of Chemistry, Laboratory of Inorganic Chemistry, University of Patras, 26504 Patras, Greece.
| | - Vassilis Nastopoulos
- Department of Chemistry, Laboratory of Inorganic Chemistry, University of Patras, 26504 Patras, Greece.
| | - Nikos Panagiotou
- Department of Chemistry, University of Cyprus, 1678 Nicosia, Cyprus
| | | | - Nikolaos Ioannidis
- Institute of Nanoscience and Nanotechnology, NCSR "Demokritos", 153 10 Aghia Paraskevi Attikis, Greece
| | - Joris van Slageren
- School of Chemistry& Chemical Engineering, Shaanxi Normal University Xi'an, 710199, China
| | - Peng Zhang
- School of Chemistry& Chemical Engineering, Shaanxi Normal University Xi'an, 710199, China.,Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany.
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai - 400 076, India.
| | - Abinash Swain
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai - 400 076, India.
| | - Vassilis Tangoulis
- Department of Chemistry, Laboratory of Inorganic Chemistry, University of Patras, 26504 Patras, Greece.
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Dey S, Rajaraman G. Deciphering the Role of Symmetry and Ligand Field in Designing Three-Coordinate Uranium and Plutonium Single-Molecule Magnets. Inorg Chem 2022; 61:1831-1842. [PMID: 35025497 DOI: 10.1021/acs.inorgchem.1c02646] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Actinide single-molecule magnets (SMMs) have gained paramount interest in molecular magnetism as they offer a larger barrier height of magnetization (Ueff) reversal compared to the lanthanide analogue, thanks to their greater metal-ligand covalency. However, the reported actinide SMMs to date yield a relatively smaller Ueff as there is no established design principle to enhance Ueff values. To address this issue, we have employed ab initio CASSCF/CASPT2/NEVPT2 calculations to study a series of three-coordinate U3+ and Pu3+ SMMs. To begin with, we have studied two experimentally characterized U3+ ion-field-induced SMMs, namely, planar [U{N(SiMe2tBu)2}3] (1) and pyramidal [U{N(SiMe3)2}3] (2) complexes reported earlier. Both the complexes were found to stabilize mJ = |±1/2⟩ as the ground state with a very strong quantum tunneling of magnetization (QTM), rendering them unsuitable for SMMs. Our calculations reveal that in the pyramidal geometry (such as in 2), the energy of the 5f26d1 state is lowered compared to the planar geometry (as in 1), resulting in a slightly better SMM characteristic in the former. To unravel the effect of symmetry in magnetic properties, ab initio calculations were performed on two reported T-shaped complexes [U(NSiiPr2)2(I)] (3) and [U(NHAriPr6)2I] (4, AriPr6 = 2,6-(2,4,6-iPr3C6H2)2C6H3). Quite interestingly, mJ = |±9/2⟩ is found to be the ground state for both the complexes with a blocking barrier exceeding 900 cm-1. Furthermore, to decipher the effect of the transuranic element in magnetic anisotropy, ab initio calculations were extended to the Pu analogue of 2, [Pu{N(SiMe3)2}3] (5), which yields a record-breaking blocking barrier of ∼1933 cm-1. Among the three-coordinate geometries studied, the pyramidal geometry was found to offer substantial magnetic anisotropy for Pu3+ ions, while a T-shaped geometry is best suited for U3+ ions. While the chosen theoretical protocols' overestimation of barrier height cannot be avoided, these values are still several orders of magnitude larger than the Ueff values reported for any actinide SMMs and unveil a design principle for superior three-coordinate actinide-based SMMs.
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Affiliation(s)
- Sourav Dey
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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40
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Shanmugam M, Kumar P, Sen A, Rajaraman G. An Unusual Mixed Valent Cobalt Dimer as a Catalyst for Anti-Markovnikov Hydrophophination of Alkynes. Inorg Chem Front 2022. [DOI: 10.1039/d2qi00112h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction of [Co(PMe3)4] (1) with a redox-active NNN pincer ligand (L1) led us to isolate a unique binuclear cobalt complex ([(PMe3)2CoII(L13-)CoI(PMe3)3] (2)) anchored by a three electron reduced L1...
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41
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Senthil Eagappan AR, Rajaraman G, Bhavani S, Vijayaraghavan R, Harishma S, Jeyapreetha P. Comparative evaluation of fracture resistance of fiber-reinforced composite and alkasite restoration in class I cavity. Contemp Clin Dent 2022; 13:56-60. [PMID: 35466303 PMCID: PMC9030303 DOI: 10.4103/ccd.ccd_707_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 09/26/2020] [Accepted: 10/21/2020] [Indexed: 11/04/2022] Open
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42
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Gupta D, Gaur AK, Chauhan D, Thakur SK, Jeyapalan V, Singh S, Rajaraman G, Venkataramani S. Solid-state photochromic arylazopyrazole based transition metal complexes. Inorg Chem Front 2022. [DOI: 10.1039/d2qi00325b] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new class of photoactive and chelating ligands L1-3 have been designed and synthesized by incorporating arylazo-3,5-dimethylpyrazole units in the ligand frameworks. Significantly they are designed in such a way...
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43
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Selvan PS, Aparajitha RV, Ahamed AS, Bhavani S, Rajaraman G. Comparative evaluation of shaping ability of sequential rotary, single rotary, and single reciprocating file systems in simulated curved canals using cone-beam computed tomography: An in vitro study. Endodontology 2022. [DOI: 10.4103/endo.endo_87_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023] Open
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44
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Sen A, Kumar R, Rajaraman G. A theoretical perspective on the reactivity of high-valent Mn-Oxo/nitrene species towards oxidative transformations. Inorganica Chim Acta 2022. [DOI: 10.1016/j.ica.2021.120654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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45
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Dearle AE, Cutler DJ, Coletta M, Lee E, Dey S, Sanz S, Fraser HWL, Nichol GS, Rajaraman G, Schnack J, Cronin L, Brechin EK. An [FeIII30] molecular metal oxide. Chem Commun (Camb) 2021; 58:52-55. [PMID: 34807967 DOI: 10.1039/d1cc06224g] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Dissolution of FeBr3 in a mixture of acetonitrile and 3,4-lutidine in the presence of an amine results in the formation of an [Fe30] molecular metal oxide containing alternating layers of tetrahedral and octahedral FeIII ions. Mass spectrometry suggests the cluster is formed quickly and remains stable in solution, while magnetic measurements and DFT calculations reveal competing antiferromagnetic exchange interactions.
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Affiliation(s)
- Alice E Dearle
- EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, UK.
| | - Daniel J Cutler
- EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, UK.
| | - Marco Coletta
- EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, UK.
| | - Edward Lee
- WestCHEM School of Chemistry, The University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK.
| | - Sourav Dey
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, 400076, India.
| | - Sergio Sanz
- EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, UK.
| | - Hector W L Fraser
- EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, UK.
| | - Gary S Nichol
- EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, UK.
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, 400076, India.
| | - Jürgen Schnack
- Fakultät für Physik, Universitat Bielefeld, Postfach 100131, D-33501 Bielefeld, Germany.
| | - Leroy Cronin
- WestCHEM School of Chemistry, The University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK.
| | - Euan K Brechin
- EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, UK.
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46
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Spillecke L, Tripathi S, Koo C, Bahr A, Swain A, Haldar R, Ansari M, Jasinski J, Rajaraman G, Shanmugam M, Klingeler R. Role of Coordination Geometry on the Magnetic Relaxation Dynamics of Isomeric Five-Coordinate Low-Spin Co(II) Complexes. Inorg Chem 2021; 61:317-327. [PMID: 34918918 DOI: 10.1021/acs.inorgchem.1c02881] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To investigate the influence of the coordination geometry on the magnetization relaxation dynamics, two geometric isomers of a five-coordinate low-spin Co(II) complex with the general molecular formula [Co(DPPE)2Cl]SnCl3 (DPPE = diphenylphosphinoethane) were synthesized and structurally characterized. While one isomer has a square pyramidal geometry (Co-SP (1)), the other isomer figures a trigonal bipyramidal geometry (Co-TBP (2)). Both complexes were already reported elsewhere. The spin state of these complexes is unambiguously determined by detailed direct current (dc) magnetic data, X-band, and high-frequency EPR measurements. Slow relaxation of magnetization is commonly observed for systems with S > 1/2. However, both 1 and 2 show field-induced slow relaxation of magnetization. Especially 1 shows relaxation times up to τ = 35 ms at T = 1.8 K, which is much longer than the reported values for undiluted Co(II) low-spin monomers. In 2, the maximal field-induced relaxation time is suppressed to τ = 5 ms. We attribute this to the change in g-anisotropy, which is, in turn, correlated to the spatial arrangement of ligands (i.e., coordination geometry) around the Co(II) ions. Besides the detailed electronic structure of these complexes, the experimental observations are further corroborated by theoretical calculations.
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Affiliation(s)
- Lena Spillecke
- Kirchhoff Institute for Physics, Heidelberg University, 69120 Heidelberg, Germany
| | - Shalini Tripathi
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Changhyun Koo
- Kirchhoff Institute for Physics, Heidelberg University, 69120 Heidelberg, Germany
| | - Arne Bahr
- Kirchhoff Institute for Physics, Heidelberg University, 69120 Heidelberg, Germany
| | - Abinash Swain
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Rajashi Haldar
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Mursaleem Ansari
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Jerry Jasinski
- Department of Chemistry, Keene State College, 229 Main Street, Keene, New Hampshire 03435-2001, United States
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Maheswaran Shanmugam
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Rüdiger Klingeler
- Kirchhoff Institute for Physics, Heidelberg University, 69120 Heidelberg, Germany.,Center for Advanced Materials, Heidelberg University, 69120 Heidelberg, Germany
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47
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Kumar R, Sundararajan M, Rajaraman G. A six-coordinate high-spin Fe IVO species of cucurbit[5]uril: a highly potent catalyst for C-H hydroxylation of methane, if synthesised. Chem Commun (Camb) 2021; 57:13760-13763. [PMID: 34854853 DOI: 10.1039/d1cc06391j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
DFT and ab initio DLPNO-CCSD(T) calculations predict a stable S = 2 six-coordinate FeIVO species with cucurbit[5]uril (CB[5]) as a ligand ([(CB[5])FeIVO(H2O)]2+(1)). The strong oxidising capability of 1 far exceeds even that of metalloenzymes such as sMMOs in activating inert substrates such as methane, setting the stage for a new generation of biomimetic catalysts.
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Affiliation(s)
- Ravi Kumar
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
| | - Mahesh Sundararajan
- Theoretical Chemistry Section, Chemistry Division, Bhabha Atomic Research Centre, Mumbai-400085, India.
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
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48
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Vignesh KR, Rajaraman G. Strategies to Design Single-Molecule Toroics Using Triangular {Ln 3} n Motifs. ACS Omega 2021; 6:32349-32364. [PMID: 34901588 PMCID: PMC8655769 DOI: 10.1021/acsomega.1c05310] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 11/12/2021] [Indexed: 06/14/2023]
Abstract
In this mini-review, we highlight the research advanced in the field of single-molecule toroics (SMTs) with a specific focus on the triangular Ln3-based SMTs. SMTs are molecules with a toroidal magnetic state and are insensitive to homogeneous magnetic fields but cooperate with charge and spin currents. The rapid growth in the area of SMTs witnessed in recent years is correlated not only to the interest to understand the fundamental physics of these molecules but also to the intriguing potential applications proposed, as the SMTs have several advantages compared to other classes of molecules such as single-molecule magnets (SMMs). The important chemico-structural strategy in SMT chemistry is to choose and design ligand and bridging species that will help to attain toroidal behavior. Considering this primarily, all the Dy3 SMTs reported so far are summarized, showing how utilizing different peripheral ligands influences the toroidal nature beyond the role of the symmetry of the molecule and stronger dipolar interactions. Likewise, linking Dy3 toroidal units through 3d ions with suitable peripheral/bridging ligands enhances the toroidal magnetic moment and leads to fascinating physics of ferrotoroidal/antiferrotoridal behavior. Further, we have also summarized the recently reported non-Dy triangular SMTs.
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49
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Wilson LRB, Coletta M, Jose R, Rajaraman G, Dalgarno SJ, Brechin EK. Oxidation state variation in bis-calix[4]arene supported decametallic Mn clusters. Dalton Trans 2021; 50:17566-17572. [PMID: 34816846 DOI: 10.1039/d1dt03410c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction of MnCl2·4H2O, H8L (2,2'-bis-p-tBu-calix[4]arene) and NEt3 in a dmf/MeOH solvent mixture results in the formation of a mixed valent decametallic cluster of formula [MnII6MnIII4(L)2(μ3-OH)4(μ-OH)4(MeOH)4(dmf)4(MeCN)2]·MeCN (3). Complex 3 crystallises in the monoclinic space group P21/n with the asymmetric unit comprising half of the compound. Structure solution reveals that the bis-calix[4]arene ligands are arranged such that one TBC[4] moiety in each has undergone inversion in order to accommodate a [MnIII4MnII6] metallic skeleton that describes three vertex-sharing [MnIII2MnII2] butterflies. The structure is closely related to the species [MnIII6MnII4(L)2(μ3-O)2(μ3-OH)2(μ-OMe)4(H2O)4(dmf)8]·4dmf (4), the major difference being the oxidation level of the Mn ions in the core of the compound. DFT calculations on the full structures reveal that replacing the MnIII ions in 4 for MnII ions in 3 results in a significant decrease in the magnitude of some antiferromagnetic exchange contributions, a switch from ferromagnetic to antiferromagnetic in others, and the loss of significant spin frustration.
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Affiliation(s)
- Lucinda R B Wilson
- EastCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, Scotland, EH9 3FJ, UK.
| | - Marco Coletta
- EastCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, Scotland, EH9 3FJ, UK.
| | - Reshma Jose
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, 400076, India.
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, 400076, India.
| | - Scott J Dalgarno
- Institute of Chemical Sciences, Heriot-Watt University, Riccarton, Edinburgh, Scotland, EH14 4AS, UK.
| | - Euan K Brechin
- EastCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, Scotland, EH9 3FJ, UK.
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50
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Gupta SK, Dey S, Rajeshkumar T, Rajaraman G, Murugavel R. Deciphering the Role of Anions and Secondary Coordination Sphere in Tuning Anisotropy in Dy(III) Air-Stable D 5h SIMs*. Chemistry 2021; 28:e202103585. [PMID: 34788493 DOI: 10.1002/chem.202103585] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Indexed: 01/05/2023]
Abstract
Precise control of the crystal field and symmetry around the paramagnetic spin centre has recently facilitated the engineering of high-temperature single-ion magnets (SIMs), the smallest possible units for future spin-based devices. In the present work, we report a series of air-stable seven coordinate Dy(III) SIMs {[L2 Dy(H2 O)5 ][X]3 ⋅L2 ⋅n(H2 O), n = 0, X = Cl (1), n=1, X = Br (2), I (3)} possessing pseudo-D5h symmetry or pentagonal bipyramidal coordination geometry with high anisotropy energy barrier (Ueff ) and blocking temperature (TB ). While the strong axial coordination from the sterically encumbered phosphonamide, t BuPO(NHi Pr)2 (L), increases the overall anisotropy of the system, the presence of high symmetry significantly quenches quantum tunnelling of magnetization, which is the prominent deactivating factor encountered in SIMs. The energy barrier (Ueff ) and the blocking temperature (TB ) decrease in the order 3>2>1 with the change of anions from larger iodide to smaller strongly hydrogen-bonded chloride in the secondary coordination sphere, albeit the local coordination geometry and the symmetry around the Dy(III) display only slight deviations. Ab initio CASSCF/RASSI-SO/SINGLE_ANISO calculations provide deeper insights into the dynamics of magnetic relaxation in addition to the role of the secondary coordination sphere in modulating the anisotropy of the D5h systems, using diverse models. Thus, in addition to the importance of the crystal field and the symmetry to obtain high-temperature SIMs, this study also probes the significance of the secondary coordination sphere that can be tailored to accomplish novel SIMs.
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Affiliation(s)
- Sandeep K Gupta
- Department of Chemistry, Indian Institute of Technology Bombay Powai, Mumbai, 400 076, India
| | - Sourav Dey
- Department of Chemistry, Indian Institute of Technology Bombay Powai, Mumbai, 400 076, India
| | - Thayalan Rajeshkumar
- Department of Chemistry, Indian Institute of Technology Bombay Powai, Mumbai, 400 076, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay Powai, Mumbai, 400 076, India
| | - Ramaswamy Murugavel
- Department of Chemistry, Indian Institute of Technology Bombay Powai, Mumbai, 400 076, India
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