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Halcrow MA, Vasili HB, Pask CM, Kulak AN, Cespedes O. Activating a high-spin iron(II) complex to thermal spin-crossover with an inert non-isomorphous molecular dopant. Dalton Trans 2024; 53:6983-6992. [PMID: 38563124 DOI: 10.1039/d4dt00443d] [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: 04/04/2024]
Abstract
[Fe(bpp)2][ClO4]2 (bpp = 2,6-bis{pyrazol-1-yl}pyridine; monoclinic, C2/c) is high-spin between 5-300 K, and crystallises with a highly distorted molecular geometry that lies along the octahedral-trigonal prismatic distortion pathway. In contrast, [Ni(bpp)2][ClO4]2 (monoclinic, P21) adopts a more regular, near-octahedral coordination geometry. Gas phase DFT minimisations (ω-B97X-D/6-311G**) of [M(bpp)2]2+ complexes show the energy penalty associated with that coordination geometry distortion runs as M2+ = Fe2+ (HS) ≈ Mn2+ (HS) < Zn2+ ≈ Co2+ (HS) ≲ Cu2+ ≪ Ni2+ ≪ Ru2+ (LS; HS = high-spin, LS = low-spin). Slowly crystallised solid solutions [FexNi1-x(bpp)2][ClO4]2 with x = 0.53 (1a) and 0.74 (2a) adopt the P21 lattice, while x = 0.87 (3a) and 0.94 (4a) are mixed-phase materials with the high-spin C2/c phase as the major component. These materials exhibit thermal spin-transitions at T½ = 250 ± 1 K which occurs gradually in 1a, and abruptly and with narrow thermal hysteresis in 2a-4a. The transition proceeds to 100% completeness in 1a and 2a; that is, the 26% Ni doping in 2a is enough to convert high-spin [Fe(bpp)2][ClO4]2 into a cooperative, fully SCO-active material. These results were confirmed crystallographically for 1a and 2a, which revealed similarities and differences between these materials and the previously published [FexNi1-x(bpp)2][BF4]2 series. Rapidly precipitated powders with the same compositions (1b-4b) mostly resemble 1a-4a, except that 2b is a mixed-phase material; 2b-4b also contain a fraction of amorphous solid in addition to the two crystal phases. The largest iron fraction that can be accommodated by the P21 phase in this system is 0.7 ± 0.1.
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Affiliation(s)
- Malcolm A Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.
| | - Hari Babu Vasili
- School of Physics and Astronomy, University of Leeds, W. H. Bragg Building, Leeds, LS2 9JT, UK
| | - Christopher M Pask
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.
| | - Alexander N Kulak
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.
| | - Oscar Cespedes
- School of Physics and Astronomy, University of Leeds, W. H. Bragg Building, Leeds, LS2 9JT, UK
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2
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M Zahir FZ, Hay MA, Janetzki JT, Gable RW, Goerigk L, Boskovic C. Predicting valence tautomerism in diverse cobalt-dioxolene complexes: elucidation of the role of ligands and solvent. Chem Sci 2024; 15:5694-5710. [PMID: 38638213 PMCID: PMC11023039 DOI: 10.1039/d3sc04493a] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Accepted: 03/08/2024] [Indexed: 04/20/2024] Open
Abstract
The ability of molecular switches to reversibly interconvert between different forms promises potential applications at the scale of single molecules up to bulk materials. One type of molecular switch comprises cobalt-dioxolene compounds that exhibit thermally-induced valence tautomerism (VT) interconversions between low spin Co(iii)-catecholate (LS-CoIII-cat) and high spin Co(ii)-semiquinonate (HS-CoII-sq) forms. Two families of these compounds have been investigated for decades but have generally been considered separately: neutral [Co(diox)(sq)(N2L)] and cationic [Co(diox)(N4L)]+ complexes (diox = generic dioxolene, N2L/N4L = bidentate/tetradentate N-donor ancillary ligand). Computational identification of promising new candidate compounds prior to experimental exploration is beneficial for environmental and cost considerations but requires a thorough understanding of the underlying thermochemical parameters that influence the switching. Herein, we report a robust approach for the analysis of both cobalt-dioxolene families, which involved a quantitative density functional theory-based study benchmarked with reliable quasi-experimental references. The best-performing M06L-D4/def2-TZVPP level of theory has subsequently been verified by the synthesis and experimental investigation of three new complexes, two of which exhibit thermally-induced VT, while the third remains in the LS-CoIII-cat form across all temperatures, in agreement with prediction. Valence tautomerism in solution is markedly solvent-dependent, but the origin of this has not been definitively established. We have extended our computational approach to elucidate the correlation of VT transition temperature with solvent stabilisation energy and change in dipole moment. This new understanding may inform the development of VT compounds for applications in soft materials including films, gels, and polymers.
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Affiliation(s)
- F Zahra M Zahir
- School of Chemistry, University of Melbourne Victoria 3010 Australia
| | - Moya A Hay
- School of Chemistry, University of Melbourne Victoria 3010 Australia
| | - Jett T Janetzki
- School of Chemistry, University of Melbourne Victoria 3010 Australia
| | - Robert W Gable
- School of Chemistry, University of Melbourne Victoria 3010 Australia
| | - Lars Goerigk
- School of Chemistry, University of Melbourne Victoria 3010 Australia
| | - Colette Boskovic
- School of Chemistry, University of Melbourne Victoria 3010 Australia
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Cramer HH, Duchemin C, Kovel CB, Kim J, Pecoraro MV, Chirik PJ. Ligand Field Sensitive Spin Acceleration in the Iron-Catalyzed [2 + 2] Cycloaddition of Unactivated Alkenes and Dienes. J Am Chem Soc 2024; 146:9947-9956. [PMID: 38537152 DOI: 10.1021/jacs.4c00591] [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: 04/11/2024]
Abstract
Redox-active pyridine(diimine) (PDI) iron catalysts promote the reversible [2 + 2] cycloaddition of alkenes and dienes to cyclobutane derivatives that have applications ranging from fuels to chemically recyclable polymers. Metallacycles were identified as key intermediates, and spin crossover from the singlet to the triplet surface was calculated to facilitate the reductive coupling step responsible for the formation of the four-membered ring. In this work, a series of sterically and electronically differentiated PDI ligands was studied for the [2 + 2] cycloaddition of ethylene and butadiene to vinylcyclobutane. Kinetic studies revealed that the fastest and slowest turnover were observed with equally electron-deficient supporting ligands that either feature phenyl-substituted imine carbon atoms (MeBPDI) or a pyrazine core (MePZDI). While the oxidative cyclization was comparatively slow for both catalysts, the rate of reductive coupling─determined by stoichiometric 13C2H4 labeling studies─correlated with the turnover frequencies. Two-state density functional theory studies and the distinct electronic structures of related (iPrBPDI) and (iPrPZDI) iron methyl complexes revealed significantly different ligand field strengths due to either diminished ligand σ-donation (MeBPDI) or promoted metal π-backbonding (MePZDI). Spin acceleration, leading to fast reductive coupling and catalytic turnover, was promoted in the case of the weaker ligand field and depends on both the nature and position of the electron-withdrawing group. This study provides strong evidence for the role of two-state reactivity in C(sp3)-C(sp3) bond formation and insights on how ligand design either promotes or inhibits spin acceleration in earth-abundant metal catalysis.
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Affiliation(s)
- Hanna H Cramer
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Coralie Duchemin
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Carli B Kovel
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Junho Kim
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Matthew V Pecoraro
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J Chirik
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Booth R, Whitwood AC, Duhme-Klair AK. Effect of Ligand Substituents on Spectroscopic and Catalytic Properties of Water-Compatible Cp*Ir-(pyridinylmethyl)sulfonamide-Based Transfer Hydrogenation Catalysts. Inorg Chem 2024; 63:3815-3823. [PMID: 38343274 PMCID: PMC10900292 DOI: 10.1021/acs.inorgchem.3c04040] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 01/23/2024] [Accepted: 01/30/2024] [Indexed: 02/27/2024]
Abstract
Transition-metal-based hydrogenation catalysts have applications ranging from high-value chemical synthesis to medicinal chemistry. A series of (pyridinylmethyl)sulfonamide ligands substituted with electron-withdrawing and -donating groups were synthesized to study the influence of the electronic contribution of the bidentate ligand in Cp*Ir piano-stool complexes. A variable-temperature NMR investigation revealed a strong correlation between the electron-donating ability of the substituent and the rate of stereoinversion of the complexes. This correlation was partially reflected in the catalytic activity of the corresponding catalysts. Complexes with electron-withdrawing substituents followed the trend observed in the variable-temperature NMR study, thereby confirming the rate-determining step to be donation of the hydride ligand. Strongly electron-donating groups, on the other hand, caused a change in the rate-determining step in the formation of the iridium-hydride species. These results demonstrate that the activity of these catalysts can be tuned systematically via changes in the electronic contribution of the bidentate (pyridinylmethyl)sulfonamide ligands.
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Huang YY, He Y, Liu Y, Fu JH, Liu XL, Wu XT, Sheng TL. Fine-tuning of thermally induced SCO behaviors of trinuclear cyanido-bridged complexes by regulating the electron donating ability of C CN-terminal fragments. Dalton Trans 2024; 53:3777-3784. [PMID: 38305017 DOI: 10.1039/d3dt04226j] [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: 02/03/2024]
Abstract
To achieve fine regulation of FeII SCO behavior, a series of trinuclear cyanido-bridged complexes trans-[CpMen(dppe)MII(CN)]2[Fe1II(abpt)2](OTf)2 (1-4) (1, M = Fe2 and n = 1; 2, M = Fe2 and n = 4; 3, M = Fe2 and n = 5; 4, M = Ru and n = 5; CpMen = alkyl cyclopentadienyl with n = 1, 4, 5; dppe = 1,2-bis-(diphenylphosphino)ethane; abpt = 4-amino-3,5-bis-(pyridin-2-yl)-1,2,4-triazole and OTf = CF3SO3-) were synthesized and fully characterized by using elemental analysis, X-ray crystallography, magnetic measurements, variable-temperature IR spectroscopy and Mössbauer spectroscopy. It is worth mentioning that different from many mononuclear Fe(abpt)2X2 (X = NCS, NCSe, N(CN)2, C(CN)3, (NC)2CC(OCH3)C(CN)2, (NC)2CC(OC2H5)C(CN)2, C16SO3 and Cl) complexes with more than one polymorph, only one polycrystalline form was found in complexes 1-4. Moreover, the thermally induced SCO behaviors of these four complexes are independent of intermolecular π-π interactions. The electron-donating ability of the CCN-terminal fragment of CpMen(dppe)MIICN can be flexibly regulated by changing the methyl number (n) of the cyclopentadiene ligand or metal ion type (MII). These investigations indicate that the electron-donating ability of the CCN-terminal fragment has an influence on the SCO behavior of Fe1II. The spin transition temperature (T1/2) of the complexes decreases with the increase of the electron-donating ability of the fragment CpMen(dppe)MII. This study provides a new strategy to predict and precisely regulate the behaviors of SCO complexes.
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Affiliation(s)
- Ying-Ying Huang
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China.
- School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yong He
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China.
- School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yang Liu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China.
- School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jin-Hui Fu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China.
- School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiao-Lin Liu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China.
- School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xin-Tao Wu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China.
| | - Tian-Lu Sheng
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China.
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6
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Kulmaczewski R, Halcrow MA. Iron(II) complexes of 2,6-bis(imidazo[1,2- a]pyridin-2-yl)pyridine and related ligands with annelated distal heterocyclic donors. Dalton Trans 2023; 52:14928-14940. [PMID: 37799008 DOI: 10.1039/d3dt02747c] [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: 10/07/2023]
Abstract
Following a published synthesis of 2,6-bis(imidazo[1,2-a]pyridin-2-yl)pyridine (L1), treatment of α,α'-dibromo-2,6-diacetylpyridine with 2 equiv. 2-aminopyrimidine or 2-aminoquinoline in refluxing acetonitrile respectively gives 2,6-bis(imidazo[1,2-a]pyrimidin-2-yl)pyridine (L2) and 2,6-bis(imidazo[1,2-a]quinolin-2-yl)pyridine (L3). Solvated crystals of [Fe(L1)2][BF4]2 (1[BF4]2) and [Fe(L2)2][BF4]2 (2[BF4]2) are mostly high-spin, although one solvate of 1[BF4]2 undergoes thermal spin-crossover on cooling. The iron coordination geometry is consistently distorted in crystals of 2[BF4]2 which may reflect the influence of intramolecular, inter-ligand N⋯π interactions on the molecular conformation. Only 1 : 1 Fe : L3 complexes were observed in solution, or isolated in the solid state; a crystal structure of [FeBr(py)2L3]Br·0.5H2O (py = pyridine) is presented. A solvate crystal structure of high-spin [Fe(L4)2][BF4]2 (L4 = 2,6-di{quinolin-2-yl}pyridine; 4[BF4]2) is also described, which exhibits a highly distorted six-coordinate geometry with a helical ligand conformation. The iron(II) complexes are high-spin in solution at room temperature, but 1[BF4]2 and 2[BF4]2 undergo thermal spin-crossover equilibria on cooling. All the compounds exhibit a ligand-based emission in solution at room temperature. Gas phase DFT calculations mostly reproduce the spin state properties of the complexes, but show small anomalies attributed to intramolecular, inter-ligand dispersion interactions in the sterically crowded molecules.
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Affiliation(s)
- Rafal Kulmaczewski
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT.
| | - Malcolm A Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT.
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7
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Paschelke T, Trumpf E, Grantz D, Pankau M, Grocholski N, Näther C, Sönnichsen FD, McConnell AJ. Tuning the spin-crossover properties of FeII4L 6 cages via the interplay of coordination motif and linker modifications. Dalton Trans 2023; 52:12789-12795. [PMID: 37615965 DOI: 10.1039/d3dt01569f] [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: 08/25/2023]
Abstract
Despite the increasing number of spin-crossover FeII-based cages, the interplay between ligand modifications (e.g. coordination motif substituents and linker) is not well-understood in these multinuclear systems, limiting rational design. Here, we report a family of FeII4L6 spin-crossover cages based on 2,2'-pyridylbenzimidazoles where subtle ligand modifications lowered the spin crossover temperature in CD3CN by up to 186 K. Comparing pairs of cages, CH3 substituents on either the coordination motif or phenylene linker lowered the spin-crossover temperature by 48 K, 91 K or 186 K, attributed to electronic effects, steric effects and a combination of both, respectively. The understanding of the interplay between ligand modifications gained from this study could be harnessed on the path towards the improved rational design of spin-crossover cages.
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Affiliation(s)
- Tobias Paschelke
- Otto Diels Institute of Organic Chemistry, Kiel University, Otto-Hahn-Platz 4, Kiel 24098, Germany
| | - Eicke Trumpf
- Otto Diels Institute of Organic Chemistry, Kiel University, Otto-Hahn-Platz 4, Kiel 24098, Germany
| | - David Grantz
- Otto Diels Institute of Organic Chemistry, Kiel University, Otto-Hahn-Platz 4, Kiel 24098, Germany
| | - Malte Pankau
- Otto Diels Institute of Organic Chemistry, Kiel University, Otto-Hahn-Platz 4, Kiel 24098, Germany
| | - Niclas Grocholski
- Otto Diels Institute of Organic Chemistry, Kiel University, Otto-Hahn-Platz 4, Kiel 24098, Germany
| | - Christian Näther
- Institute of Inorganic Chemistry, Kiel University, Max-Eyth-Straße 2, Kiel 24118, Germany
| | - Frank D Sönnichsen
- Otto Diels Institute of Organic Chemistry, Kiel University, Otto-Hahn-Platz 4, Kiel 24098, Germany
| | - Anna J McConnell
- Otto Diels Institute of Organic Chemistry, Kiel University, Otto-Hahn-Platz 4, Kiel 24098, Germany
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8
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Sundaresan S, Brooker S. Solution Spin Crossover Versus Speciation Effects: A Cautionary Tale. Inorg Chem 2023. [PMID: 37482662 DOI: 10.1021/acs.inorgchem.3c00186] [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: 07/25/2023]
Abstract
Two acyclic tetradentate Schiff base ligands, HLX-OH (X = H and Br), were synthesised by 2:1 condensation of either 2-pyridinecarboxaldehyde or 5-bromo-2-pyridinecarboxaldehyde and 1,3-diamino-2-propanol and then used to prepare six mononuclear complexes, [FeII(HLX-OH)(NCE)2], with three different NCE co-ligands (E = BH3, Se, and S). The apparent solution spin crossover switching temperature, T1/2, of these 6 complexes, determined by Evans method NMR studies, is tuned by several factors: (a) substituent X present at the 5 position of the pyridine ring of the ligand, (b) E present in the NCE co-ligand, (c) solvent employed (P'), and (d) potentially also by speciation effects. In CD3CN, for the pair of NCE = NCBH3 complexes, when X = H, the complex is practically LS (extrapolated T1/2 ∼624 K), whereas when X = Br, it is far lower (373 K), which implies a higher field strength when X = H than when it is Br. The same trend, X = H results in a higher apparent T1/2 than X = Br, is seen for the other two pairs of complexes, with E = Se (429 > 351 K, ΔT1/2 = 78 K) or S (361 > 342 K, ΔT1/2 = 19 K). For the family of three X = Br complexes, the change of E from BH3 (373 K) to Se (351 K) to S (342 K) leads to an overall ΔT1/2(apparent) = 31 K, whereas the decreases are far more pronounced in the X = H family (BH3 ∼624 > Se 429 > S 361 K). Changing the solvent used from CD3CN to (CD3)2CO and CD3NO2, for [FeII(HLBr-OH)(NCE)2] with either E = BH3 or S, revealed excellent, and very similar, positive linear correlations (R2 = 0.99) of increasing solvent polarity index P' (from 5 to 7) with increasing apparent T1/2 of the complex (E = BH3 gave T1/2 300 < 373 < 451 K , ΔT1/2 = 151 K; E = S gave T1/2 288 < 342 < 427 K, ΔT1/2 = 147 K). Several other solvent parameters were also correlated with the apparent T1/2 of these complexes (R2 = 0.74-0.96). Excellent linear correlations (R2 = 0.99) are also obtained with the coordination ability (aTM) of the three NCE co-ligands with the apparent T1/2 in both families of compounds, [FeII(HLX-OH)(NCE)2] where X = H or Br. The 15N NMR chemical shifts of the nitrogen atom in the three NCE co-ligands (direct measurement) show modest correlations (R2 = 0.74 for LH-OH family and 0.80 for LBr-OH family) with the apparent T1/2 values of the corresponding complexes.
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Affiliation(s)
- Sriram Sundaresan
- Department of Chemistry and the MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Sally Brooker
- Department of Chemistry and the MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
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Wang J, Li Y, Wei RJ, Tang Z, Yao ZS, Tao J. Spin-Crossover Behaviors of Iron(II) Complexes Bearing Halogen Ligands in Solid State and Solution. Inorg Chem 2023; 62:1354-1361. [PMID: 36635894 DOI: 10.1021/acs.inorgchem.2c02815] [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: 01/14/2023]
Abstract
Numerous Fe(II) spin-crossover (SCO) compounds have been developed in the past decades, while the reports on the SCO materials with halogen atoms acting as coordinating ligands remain rare. In this study, we synthesize three iron(II) halide complexes with a general formula of [FeII(Py5Me2)X]+ (Py5Me2 = 2,6-bis[1,1-bis(2-pyridyl)ethyl]pyridine, X = Cl- or Br-) that undergo complete SCO transitions at near room temperature. The SCO properties of these compounds are investigated in detail by magnetic measurements, variable-temperature single-crystal X-ray diffractions, and Mössbauer spectra analyses. Because of the good stability of the coordination structures and suitable ligand-field strength, these compounds show robust spin transitions in both solid state and solution.
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Affiliation(s)
- Ju Wang
- Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Liangxiang Campus, Beijing Institute of Technology, Beijing 102488, People's Republic of China
| | - Yun Li
- Engineering Research Center for Nanomaterials, Henan University, Kaifeng 475004, People's Republic of China
| | - Rong-Jia Wei
- College of Chemistry and Materials Science and Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and Applications, Jinan University, Guangzhou 510632, People's Republic of China
| | - Zheng Tang
- Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Liangxiang Campus, Beijing Institute of Technology, Beijing 102488, People's Republic of China
| | - Zi-Shuo Yao
- Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Liangxiang Campus, Beijing Institute of Technology, Beijing 102488, People's Republic of China
| | - Jun Tao
- Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Liangxiang Campus, Beijing Institute of Technology, Beijing 102488, People's Republic of China
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10
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Dey B, Mehta S, Mondal A, Cirera J, Colacio E, Chandrasekhar V. Push and Pull Effect of Methoxy and Nitro Groups Modifies the Spin-State Switching Temperature in Fe(III) Complexes. ACS Omega 2022; 7:39268-39279. [PMID: 36340084 PMCID: PMC9631739 DOI: 10.1021/acsomega.2c05380] [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: 08/22/2022] [Accepted: 09/29/2022] [Indexed: 06/16/2023]
Abstract
We have explored the impact of electron-donating (methoxy) and electron-withdrawing (nitro) substituents on SalEen ligand based spin crossover (SCO) behavior of Fe(III) complexes. Thus, 3-X-substituted SalEen ligands were employed to prepare [Fe(3-X-SalEen)2]·NCSe, where X = OMe (1), H (2), and NO2 (3) (3-X-SalEen is the condensation product of 3-substituted salicylaldehyde and N-ethylethylenediamine). The characteristic spin transition temperature (T 1/2) is shown to shift to a lower temperature when an electron-donating substituent (OMe) is used and to a higher temperature when an electron-withdrawing substituent (NO2) is used. We used experimental and theoretical methods to determine the reasons for this behavior. The solid-state magnetic data revealed the transition temperatures for complexes 1, 2, and 3 to be 219, 251, and 366 K, respectively. The solution-state magnetic data also support this trend in T 1/2 values. UV-vis spectra analysis indicates that there is greater delocalization in the π-manifold of the ligand when the nitro group is the substituent. Theoretical studies through density functional theory methods suggest the methoxy substituent decreases the energy gap between the t2g and eg orbitals (explaining the lower T 1/2 value), while the nitro substituent increases the energy gap between the t2g and eg orbitals and thus increases the T 1/2 value.
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Affiliation(s)
- Bijoy Dey
- Tata
Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad500107, India
| | - Sakshi Mehta
- Solid
State and Structural Chemistry Unit, Indian
Institute of Science, Sir C V Raman Road, Bangalore, Karnataka560012, India
| | - Abhishake Mondal
- Solid
State and Structural Chemistry Unit, Indian
Institute of Science, Sir C V Raman Road, Bangalore, Karnataka560012, India
| | - Jordi Cirera
- Departament
de Química Inorgànica i Orgànica and Institut
de Recerca de Química Teòrica i Computacional, Universitat de Barcelona, Diagonal 645, 08028Barcelona, Spain
| | - Enrique Colacio
- Departamento
de Química Inorgánica, Facultad de Ciencias, Universidad de Granada, 18071Granada, Spain
| | - Vadapalli Chandrasekhar
- Tata
Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad500107, India
- Department
of Chemistry, Indian Institute of Technology
Kanpur, Kanpur, Uttar Pradesh208016, India
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11
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Dey B, Chandrasekhar V. Fe II spin crossover complexes containing N 4O 2 donor ligands. Dalton Trans 2022; 51:13995-14021. [PMID: 36040413 DOI: 10.1039/d2dt01967a] [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
Spin crossover (SCO) is one of the most studied magnetic bistable phenomena because of its application in the field of multifunctional magnetic materials. FeII complexes in a N6 coordination environment have been the most well-studied in terms of their SCO behaviour. Other coordination environments, notably the N4O2 coordination environment, has also been quite effective in inducing SCO behaviour in the corresponding FeII complexes. This review deals with such systems. The three ligand families that are discussed are: Jager type ligands, hydrazone based ligands and tridentate ligands having salicylaldehyde derivatives. These ligands allow the assembly of both mononuclear and multinuclear complexes that exhibit cooperative spin transitions. Also, FeII complexes obtained from some of these ligands are multifunctional and exhibit a coupling of optical and magnetic properties. Most of the FeII complexes obtained from these families of ligands are charge neutral which allows easy surface deposition. Further, modulation of these ligand families allows a fine tuning of the ligand field strength which results in varying SCO behavior. In addition some of the FeII complexes derived from these ligands exhibit a light induced excited spin state trapping (LIESST) effect. All of the above aspects are reviewed in this review.
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Affiliation(s)
- Bijoy Dey
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad - 500046, Telangana, India.
| | - Vadapalli Chandrasekhar
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad - 500046, Telangana, India. .,Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India
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12
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Mel’nikova EK, Nikovskii IA, Polezhaev AV, Nelyubina YV. Solvatomorphs of Iron(II) Complex with N,N'-Disubstituted 2,6-Bis(pyrazol-3-yl)pyridine with a Temperature-Induced Spin Transition in Solution. RUSS J COORD CHEM+ 2022. [DOI: 10.1134/s1070328422080048] [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: 11/22/2022]
Abstract
Abstract
The reaction of the tridentate ligand 4-(2,6-bis(5-tert-butyl-1-(2,6-dichlorophenyl)-1H-pyrazol-3-yl)pyridin-4-yl)benzonitrile (L) with iron(II) salt gave the complex [Fe(L)2](BF4)2, which was isolated in a pure state and characterized by elemental analysis, NMR spectroscopy, and X-ray diffraction as two crystal polymorphs differing in the nature of the solvent molecule in the crystal (solvatomorphs I and II). According to the results of X-ray diffraction study (CCDC nos. 2104367 (I), 2104368 (II)), the iron(II) ion in these compounds occurs in different spin states and does not undergo a temperature-induced spin transition, which was previously observed for this complex in solution. The details of supramolecular organization of two solvatomorphs that prevent this transition were studied using the Hirshfeld surface analysis.
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13
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Bayeh Y, Suryadevara N, Schlittenhardt S, Gyepes R, Sergawie A, Hrobárik P, Linert W, Ruben M, Thomas M. Investigations on the Spin States of Two Mononuclear Iron(II) Complexes Based on N-Donor Tridentate Schiff Base Ligands Derived from Pyridine-2,6-Dicarboxaldehyde. Inorganics 2022; 10:98. [DOI: 10.3390/inorganics10070098] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Iron(II)-Schiff base complexes are a well-studied class of spin-crossover (SCO) active species due to their ability to interconvert between a paramagnetic high spin-state (HS, S = 2, 5T2) and a diamagnetic low spin-state (LS, S = 0, 1A1) by external stimuli under an appropriate ligand field. We have synthesized two mononuclear FeII complexes, viz., [Fe(L1)2](ClO4)2.CH3OH (1) and [Fe(L2)2](ClO4)2.2CH3CN (2), from two N6–coordinating tridentate Schiff bases derived from 2,6-bis[(benzylimino)methyl]pyridine. The complexes have been characterized by elemental analysis, electrospray ionization–mass spectrometry (ESI-MS), Fourier-transform infrared spectroscopy (FTIR), solution state nuclear magnetic resonance spectroscopy, 1H and 13C NMR (both theoretically and experimentally), single-crystal diffraction and magnetic susceptibility studies. The structural, spectroscopic and magnetic investigations revealed that 1 and 2 are with Fe–N6 distorted octahedral coordination geometry and remain locked in LS state throughout the measured temperature range from 5–350 K.
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14
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Khakina EA, Denisov GL, Nikovskii IA, Polezhaev AV, Nelyubina YV. Spin State of the Cobalt(II) Complex with N,N'-Disubstituted 2,6-Bis(pyrazol-3-yl)pyridine. RUSS J COORD CHEM+ 2022. [DOI: 10.1134/s1070328422060021] [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: 11/23/2022]
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15
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Wu C, Gao KG, Yao ZS, Tao J. A series of dynamic single crystals of [M II(en) 3]SO 4 (M = Ni, Mn, and Cd) shows tunable dielectric properties and anisotropic thermal expansion. Dalton Trans 2022; 51:6809-6816. [PMID: 35437553 DOI: 10.1039/d2dt00506a] [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 series of dynamic single crystals with a chemical formula of [MII(en)3]SO4 (en = ethylene and MII = NiII, MnII, and CdII) was synthesized. As the temperature decreases, these materials exhibit dielectric switching in the vicinity of the phase transition point accompanied by anisotropic thermal expansion in the cell parameters as a consequence of the order-disorder structural change of SO2-4 in a cavity surrounded by five [MII(en)3]2+ complex cations. Because the variation of metal centers with different ionic radii changes the shape of the complex cation, which affects the distribution of hydrogen-bond interactions around the SO2-4, the dynamic motion of SO2-4 is substantially tuned. Correspondingly, the dielectric properties and anisotropic thermal expansion of materials were largely shifted, especially in the single crystals of [MnII(en)3]SO4, whose structural change is distinctly different from the crystals of Ni(II) and Cd(II). The detailed structural mechanism accounting for the different physical properties of these materials was discussed.
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Affiliation(s)
- Cong Wu
- Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Liangxiang Campus, Beijing Institute of Technology, Beijing 102488, People's Republic of China.
| | - Kai-Ge Gao
- College of Physical Science and Technology, Yangzhou University, Yangzhou, Jiangsu, People's Republic of China
| | - Zi-Shuo Yao
- Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Liangxiang Campus, Beijing Institute of Technology, Beijing 102488, People's Republic of China.
| | - Jun Tao
- Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Liangxiang Campus, Beijing Institute of Technology, Beijing 102488, People's Republic of China.
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16
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Bondì L, Garden AL, Totti F, Jerabek P, Brooker S. Quantitative Assessment of Ligand Substituent Effects on σ‐ and π‐Contributions to Fe−N Bonds in Spin Crossover Fe
II
Complexes. Chemistry 2022; 28:e202104314. [PMID: 35224791 PMCID: PMC9310619 DOI: 10.1002/chem.202104314] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [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] [Received: 12/02/2021] [Indexed: 11/24/2022]
Abstract
The effect of para‐substituent X on the electronic structure of sixteen tridentate 4‐X‐(2,6‐di(pyrazol‐1‐yl))‐pyridine (bppX) ligands and the corresponding solution spin crossover [FeII(bppX)2]2+ complexes is analysed further, to supply quantitative insights into the effect of X on the σ‐donor and π‐acceptor character of the Fe‐NA(pyridine) bonds. EDA‐NOCV on the sixteen LS complexes revealed that neither ΔEorb,σ+π (R2=0.48) nor ΔEorb,π (R2=0.31) correlated with the experimental solution T1/2 values (which are expected to reflect the ligand field imposed on the iron centre), but that ΔEorb,σ correlates well (R2=0.82) and implies that as X changes from EDG→EWG (Electron Donating to Withdrawing Group), the ligand becomes a better σ‐donor. This counter‐intuitive result was further probed by Mulliken analysis of the NA atomic orbitals: NA(px) involved in the Fe−N σ‐bond vs. the perpendicular NA(pz) employed in the ligand aromatic π‐system. As X changes EDG→EWG, the electron population on NA(pz) decreases, making it a better π‐acceptor, whilst that in NA(px) increases, making it a better σ‐bond donor; both increase ligand field, and T1/2 as observed. In 2016, Halcrow, Deeth and co‐workers proposed an intuitively reasonable explanation of the effect of the para‐X substituents on the T1/2 values in this family of complexes, consistent with the calculated MO energy levels, that M→L π‐backdonation dominates in these M−L bonds. Here the quantitative EDA‐NOCV analysis of the M−L bond contributions provides a more complete, coherent and detailed picture of the relative impact of M−L σ‐versus π‐bonding in determining the observed T1/2, refining the earlier interpretation and revealing the importance of the σ‐bonding. Furthermore, our results are in perfect agreement with the ΔE(HS‐LS) vs. σp+(X) correlation reported in their work.
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Affiliation(s)
- Luca Bondì
- Department of Chemistry MacDiarmid Institute of Advanced Materials and Nanotechnology University of Otago PO Box 56 Dunedin 9054 New Zealand
- Department of Chemistry ‘Ugo Schiff' and INSTM Research Unit University of Florence 50019 Sesto Fiorentino Italy
| | - Anna L. Garden
- Department of Chemistry MacDiarmid Institute of Advanced Materials and Nanotechnology University of Otago PO Box 56 Dunedin 9054 New Zealand
| | - Federico Totti
- Department of Chemistry ‘Ugo Schiff' and INSTM Research Unit University of Florence 50019 Sesto Fiorentino Italy
| | - Paul Jerabek
- Institute of Hydrogen Technology Helmholtz-Zentrum Hereon Max-Planck-Straße 1 21502 Geesthacht Germany
| | - Sally Brooker
- Department of Chemistry MacDiarmid Institute of Advanced Materials and Nanotechnology University of Otago PO Box 56 Dunedin 9054 New Zealand
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17
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Kulmaczewski R, Kershaw Cook LJ, Pask CM, Cespedes O, Halcrow MA. Iron(II) Complexes of 4-(Alkyldisulfanyl)-2,6-di(pyrazolyl)pyridine Derivatives. Correlation of Spin-Crossover Cooperativity with Molecular Structure Following Single-Crystal-to-Single-Crystal Desolvation. Cryst Growth Des 2022; 22:1960-1971. [PMID: 35431660 PMCID: PMC9007408 DOI: 10.1021/acs.cgd.2c00005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 01/24/2022] [Indexed: 06/14/2023]
Abstract
The complex salts [Fe(L 1)2]X2 (1X 2 ; L 1 = 4-(isopropyldisulfanyl)-2,6-bis(pyrazolyl)pyridine; X- = BF4 -, ClO4 -) form solvated crystals from common organic solvents. Crystals of 1X 2 ·Me2CO show abrupt spin transitions near 160 K, with up to 22 K thermal hysteresis. 1X 2 ·Me2CO cocrystallizes with other, less cooperative acetone solvates, which all transform into the same solvent-free materials 1X 2 ·sf upon exposure to air, or mild heating. Conversion of 1X 2 ·Me2CO to 1X 2 ·sf proceeds in a single-crystal to single-crystal fashion. 1X 2 ·sf are not isomorphous with the acetone solvates, and exhibit abrupt spin transitions at low temperature with hysteresis loops of 30-38 K (X- = BF4 -) and 10-20 K (X- = ClO4 -), depending on the measurement method. Interestingly, the desolvation has an opposite effect on the SCO temperature and hysteresis in the two salts. The hysteretic spin transitions in 1X 2 ·Me2CO and 1X 2 ·sf do not involve a crystallographic phase change but are accompanied by a significant rearrangement of the metal coordination sphere. Other solvates 1X 2 ·MeNO2, 1X 2 ·MeCN, and 1X 2 ·H2O are mostly isomorphous with each other and show more gradual spin-crossover equilibria near room temperature. All three of these lattice types have similar unit cell dimensions and contain cations associated into chains through pairwise, intermolecular S···π interactions. Polycrystalline [Fe(L 2)2][BF4]2·MeNO2 (2[BF 4 ] 2 ·MeNO2; L 2 = 4-(methyldisulfanyl)-2,6-bis(pyrazolyl)pyridine) shows an abrupt spin transition just above room temperature, with an unsymmetrical and structured hysteresis loop, whose main features are reversible upon repeated thermal scanning.
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Affiliation(s)
- Rafal Kulmaczewski
- School
of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K.
| | | | - Christopher M. Pask
- School
of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K.
| | - Oscar Cespedes
- School
of Physics and Astronomy, University of
Leeds, E. C. Stoner
Building, Leeds LS2 9JT, U.K.
| | - Malcolm A. Halcrow
- School
of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K.
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18
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Aleshin DY, Diego R, Barrios LA, Nelyubina YV, Aromí G, Novikov VV. Unravelling of a [High Spin—Low Spin] ↔ [Low Spin—High Spin] Equilibrium in Spin‐Crossover Iron(II) Dinuclear Helicates Using Paramagnetic NMR Spectroscopy. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202110310] [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)
- Dmitry Yu. Aleshin
- A. N. Nesmeyanov Institute of Organoelement Compounds Russian Academy of Sciences Vavilova str. 28 11999 Moscow Russia
| | - Rosa Diego
- Department de Quimica Inorganica and IN2UB Universitat de Barcelona Diagonal 647 08028 Barcelona Spain
| | - Leoní A. Barrios
- Department de Quimica Inorganica and IN2UB Universitat de Barcelona Diagonal 647 08028 Barcelona Spain
| | - Yulia V. Nelyubina
- A. N. Nesmeyanov Institute of Organoelement Compounds Russian Academy of Sciences Vavilova str. 28 11999 Moscow Russia
- Moscow Institute of Physics and Technology Institutskiy per. 9 141700 Dolgoprudny Moscow region Russia
| | - Guillem Aromí
- Department de Quimica Inorganica and IN2UB Universitat de Barcelona Diagonal 647 08028 Barcelona Spain
| | - Valentin V. Novikov
- A. N. Nesmeyanov Institute of Organoelement Compounds Russian Academy of Sciences Vavilova str. 28 11999 Moscow Russia
- Moscow Institute of Physics and Technology Institutskiy per. 9 141700 Dolgoprudny Moscow region Russia
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19
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Liang HC, Pan Y, Zhu HL, Meng YS, Liu CH, Liu T, Zhu YY. The substituent effect on the spin-crossover behaviour in a series of mononuclear Fe( ii) complexes from thio-pybox ligands. Inorg Chem Front 2022. [DOI: 10.1039/d2qi00208f] [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: 11/21/2022]
Abstract
The correlation of the SCO temperature and substituent electronegativity of ligands is observed and discussed for a family of [Fe(thio-pybox)2]2+ complexes.
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Affiliation(s)
- Hai-Chao Liang
- School of Chemistry and Chemical Engineering, Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009, China
| | - Yao Pan
- School of Chemistry and Chemical Engineering, Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009, China
| | - Hai-Lang Zhu
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Dalian 116024, China
| | - Yin-Shan Meng
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Dalian 116024, China
| | - Chun-Hua Liu
- School of Chemistry and Chemical Engineering, Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009, China
| | - Tao Liu
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Dalian 116024, China
| | - Yuan-Yuan Zhu
- School of Chemistry and Chemical Engineering, Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009, China
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Dalian 116024, China
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20
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Hagiwara H, Konomura S. Thermosalience coupled to abrupt spin crossover with dynamic ligand motion in an iron(II) molecular crystal. CrystEngComm 2022. [DOI: 10.1039/d2ce00501h] [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
Here we report an iron(II) molecular crystal that show thermosalient effect (crystal jumping) coupled to cooperative high-spin (HS) to low-spin (LS) spin crossover (SCO). The new iron(II) compound [Fe(LPh,Et)2(NCS)2] (LPh,Et...
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21
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Shahid N, Burrows KE, Pask CM, Cespedes O, Howard MJ, McGowan PC, Halcrow MA. Heteroleptic iron( ii) complexes of chiral 2,6-bis(oxazolin-2-yl)-pyridine (PyBox) and 2,6-bis(thiazolin-2-yl)pyridine ligands – the interplay of two different ligands on the metal ion spin sate. Dalton Trans 2022; 51:4262-4274. [DOI: 10.1039/d2dt00393g] [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 spin-crossover properties of [Fe(LR)L][ClO4]2 (LR = a chiral PyBox {L1R} or ThioPyBox {L2R} derivative) show subtle differences depending on the tridentate ‘L’ co-ligand.
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Affiliation(s)
- Namrah Shahid
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT
| | - Kay E. Burrows
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT
| | | | - Oscar Cespedes
- School of Physics and Astronomy, University of Leeds, WH Bragg Building, Leeds, UK LS2 9JT
| | - Mark J. Howard
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT
| | - Patrick C. McGowan
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT
| | - Malcolm A. Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT
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22
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Birchall LT, Truccolo G, Jackson L, Shepherd HJ. Co-crystallisation as a Modular Approach to the Discovery of Spin-Crossover Materials. Chem Sci 2022; 13:3176-3186. [PMID: 35414871 PMCID: PMC8926199 DOI: 10.1039/d1sc04956a] [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] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 02/16/2022] [Indexed: 11/21/2022] Open
Abstract
Herein we present co-crystallisation as a strategy for materials discovery in the field of switchable spin crossover (SCO) systems. Using [Fe(3-bpp)2]·2A (where 3-bpp = 2,6-bis(pyrazol-3-yl)pyridine, A = BF4- / PF6-)...
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Affiliation(s)
- Lee T Birchall
- School of Physical Sciences, University of Kent Canterbury UK
| | - Giada Truccolo
- School of Physical Sciences, University of Kent Canterbury UK
| | - Lewis Jackson
- School of Physical Sciences, University of Kent Canterbury UK
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23
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Kuppusamy SK, Suryadevara N, Mizuno A, Spieker L, Salamon S, Sleziona S, Maas A, Pollmann E, Heinrich B, Schleberger M, Wende H, Ruben M. Structural Insights into Hysteretic Spin-Crossover in a Set of Iron(II)-2,6-bis(1H-pyrazol-1-yl)pyridine) Complexes. Chemistry 2021; 28:e202103853. [PMID: 34939670 PMCID: PMC9305185 DOI: 10.1002/chem.202103853] [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] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Indexed: 11/21/2022]
Abstract
Bistable spin‐crossover (SCO) complexes that undergo abrupt and hysteretic (ΔT1/2) spin‐state switching are desirable for molecule‐based switching and memory applications. In this study, we report on structural facets governing hysteretic SCO in a set of iron(II)‐2,6‐bis(1H‐pyrazol‐1‐yl)pyridine) (bpp) complexes – [Fe(bpp−COOEt)2](X)2⋅CH3NO2 (X=ClO4, 1; X=BF4, 2). Stable spin‐state switching – T1/2=288 K; ΔT1/2=62 K – is observed for 1, whereas 2 undergoes above‐room‐temperature lattice‐solvent content‐dependent SCO – T1/2=331 K; ΔT1/2=43 K. Variable‐temperature single‐crystal X‐ray diffraction studies of the complexes revealed pronounced molecular reorganizations – from the Jahn‐Teller‐distorted HS state to the less distorted LS state – and conformation switching of the ethyl group of the COOEt substituent upon SCO. Consequently, we propose that the large structural reorganizations rendered SCO hysteretic in 1 and 2. Such insights shedding light on the molecular origin of thermal hysteresis might enable the design of technologically relevant molecule‐based switching and memory elements.
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Affiliation(s)
- Senthil Kumar Kuppusamy
- Karlsruhe Institute of Technology: Karlsruher Institut fur Technologie, Institute for quantum materials and technologies, Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen,, 76344, Karlsruhe, GERMANY
| | - Nithin Suryadevara
- Karlsruhe Institute of Technology: Karlsruher Institut fur Technologie, IQMT, GERMANY
| | - Asato Mizuno
- Karlsruhe Institute of Technology: Karlsruher Institut fur Technologie, INT, GERMANY
| | - Lea Spieker
- University of Duisburg-Essen: Universitat Duisburg-Essen, Faculty of Physics and CENIDE, GERMANY
| | - Soma Salamon
- University of Duisburg-Essen: Universitat Duisburg-Essen, Faculty of Physics and CENIDE, GERMANY
| | - Stephan Sleziona
- University of Duisburg-Essen: Universitat Duisburg-Essen, Faculty of Physics and CENIDE, GERMANY
| | - André Maas
- University of Duisburg-Essen: Universitat Duisburg-Essen, Faculty of Physics and CENIDE, GERMANY
| | - Erik Pollmann
- University of Duisburg-Essen: Universitat Duisburg-Essen, Faculty of Physics and CENIDE, GERMANY
| | - Benoît Heinrich
- IPCMS: Institut de physique et chimie des materiaux de Strasbourg, DMO, FRANCE
| | - Marika Schleberger
- University of Duisburg-Essen: Universitat Duisburg-Essen, Faculty of Physics and CENIDE, GERMANY
| | - Heiko Wende
- University of Duisburg-Essen: Universitat Duisburg-Essen, Faculty of Physics and CENIDE, GERMANY
| | - Mario Ruben
- Karlsruhe Institute of Technology: Karlsruher Institut fur Technologie, Institute of Nanotechnology, GERMANY
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24
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Ma C, Besson C. Precise control of the degree and regioselectivity of functionalization in nitro- and amino-functionalized di(trispyrazolylborato)iron(II) spin crossover complexes. Dalton Trans 2021; 50:18077-18088. [PMID: 34846411 DOI: 10.1039/d1dt03445f] [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: 11/21/2022]
Abstract
Di(trispyrazolylborato)iron(II) ([Tp2Fe]) complexes represent one of the most robust classes of spin-crossover complexes. Their stability renders them particularly suitable for integration in nanoscale devices, e.g. as sensors or information storage units. While prior studies of the functionalization of those derivatives have been focused on the electronic and steric effects of alkyl and -CF3 groups in position 3, a pyrazole exchange reaction between nitropyrazole and either trispyrazolylborate or its iron complex allows the regioselective installation of nitro substituents in positions 3, 4 and 5 of the [Tp2Fe] complexes. The degree of substitution can be varied from 1 to 4 functionalized pyrazoles per complex. The amine-functionalized analogues are accessed by reduction of the nitro analogues under hydrogen transfer conditions. With the exception of di- and tetra-3-NO2 substituted complexes, all derivatives display spin crossover properties in the solid state, with transition temperatures ranging from 180 to 380 K and showing different degrees of abruptness but no hysteresis. The Slichter-Drickamer model was used to extract the empirical thermodynamic transition parameters, allowing a systematic investigation of the influence of stoichiometry, position, and electronic nature of the substitution on the magnetic properties of the complexes. The steric effects dominate for substitution in position 3 but the electronic effects are significant for the other positions.
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Affiliation(s)
- Chenyang Ma
- Department of Chemistry, The George Washington University, 800 22nd Street NW, Washington, D.C. 20052, USA.
| | - Claire Besson
- Department of Chemistry, The George Washington University, 800 22nd Street NW, Washington, D.C. 20052, USA.
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25
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Abstract
Two new iron(II) complexes [Fe(bppCHO)2](ClO4)2 (1·ClO4) and [Fe(bppCHO)2](BF4)2·H2O (1·BF4) were synthesized by using 2,6-di(1H-pyrazol-1-yl)isonicotinaldehyde (bppCHO) as the ligand. The structures and spin states of the complexes were characterized by single-crystal X-ray diffraction and magnetic susceptibility measurements. Complex 1·ClO4 exhibits light-induced excited spin state trapping (LIESST) up to 53 K and two-step spin-crossover (SCO) over room temperature, in which the first step shows a thermal hysteresis of 26 K, whereas 1·BF4 exhibits a gradual SCO behavior. A magnetostructural study reveals that the difference in the SCO property is related to the supramolecular interactions and crystal packing effect.
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Affiliation(s)
- Qianqian Yang
- State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. .,School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefe 230026, P. R. China
| | - Yin-Shan Meng
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Rd., Dalian 116024, P. R. China
| | - Tao Liu
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Rd., Dalian 116024, P. R. China
| | - Jinkui Tang
- State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. .,School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefe 230026, P. R. China
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26
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Aleshin D, Nikovskiy I, Novikov VV, Polezhaev AV, Melnikova EK, Nelyubina YV. Room-Temperature Spin Crossover in a Solution of Iron(II) Complexes with N, N'-Disubstituted Bis(pyrazol-3-yl)pyridines. ACS Omega 2021; 6:33111-33121. [PMID: 34901662 PMCID: PMC8655922 DOI: 10.1021/acsomega.1c05463] [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] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 11/09/2021] [Indexed: 05/15/2023]
Abstract
Here, we report a combined study of the effects of two chemical modifications to an N,N'-disubstituted bis(pyrazol-3-yl)pyridine (3-bpp) and of different solvents on the spin-crossover (SCO) behavior in otherwise high-spin iron(II) complexes by solution NMR spectroscopy. The observed stabilization of the low-spin state by electron-withdrawing substituents in the two positions of the ligand that induce opposite electronic effects in SCO-active iron(II) complexes of isomeric bis(pyrazol-1-yl)pyridines (1-bpp) was previously hidden by NH functionalities in 3-bpp precluding the molecular design of SCO compounds with this family of ligands. With the recent SCO-assisting substituent design, the uncovered trends converged toward the first iron(II) complex of N,N'-disubstituted 3-bpp to undergo an almost complete SCO centered at room temperature in a less polar solvent of a high hydrogen-bond acceptor ability.
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Affiliation(s)
- Dmitry
Yu Aleshin
- A.N.
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of
Sciences, Vavilova Str., 28, 119991 Moscow, Russia
| | - Igor Nikovskiy
- A.N.
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of
Sciences, Vavilova Str., 28, 119991 Moscow, Russia
- Bauman
Moscow State Technical University, 2nd Baumanskaya Str., 5, 105005 Moscow, Russia
| | - Valentin V. Novikov
- A.N.
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of
Sciences, Vavilova Str., 28, 119991 Moscow, Russia
- Moscow
Institute of Physics and Technology, Institutskiy per., 9, 141700 Dolgoprudny, Russia
| | - Alexander V. Polezhaev
- A.N.
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of
Sciences, Vavilova Str., 28, 119991 Moscow, Russia
- Bauman
Moscow State Technical University, 2nd Baumanskaya Str., 5, 105005 Moscow, Russia
| | - Elizaveta K. Melnikova
- A.N.
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of
Sciences, Vavilova Str., 28, 119991 Moscow, Russia
- Lomonosov
Moscow State University, Leninskiye Gory, 1-3, 119991 Moscow, Russia
| | - Yulia V. Nelyubina
- A.N.
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of
Sciences, Vavilova Str., 28, 119991 Moscow, Russia
- Bauman
Moscow State Technical University, 2nd Baumanskaya Str., 5, 105005 Moscow, Russia
- Moscow
Institute of Physics and Technology, Institutskiy per., 9, 141700 Dolgoprudny, Russia
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27
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Dürrmann A, Hörner G, Wagner S, Breuning M, Weber B. Sterically Encumbered Coordination Sites. Iron(II) Complexes of Jäger‐type ligands with a Terphenyl Backbone. Z Anorg Allg Chem 2021. [DOI: 10.1002/zaac.202100196] [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: 11/10/2022]
Affiliation(s)
- Andreas Dürrmann
- Department of Chemistry Inorganic Chemistry University of Bayreuth Universitätsstraße 30, NWI 95440 Bayreuth Germany
| | - Gerald Hörner
- Department of Chemistry Inorganic Chemistry University of Bayreuth Universitätsstraße 30, NWI 95440 Bayreuth Germany
| | - Stefan Wagner
- Department of Chemistry Organic Chemistry University of Bayreuth Universitätsstraße 30, NWII 95440 Bayreuth Germany
| | - Matthias Breuning
- Department of Chemistry Organic Chemistry University of Bayreuth Universitätsstraße 30, NWII 95440 Bayreuth Germany
| | - Birgit Weber
- Department of Chemistry Inorganic Chemistry University of Bayreuth Universitätsstraße 30, NWI 95440 Bayreuth Germany
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28
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Aleshin DY, Diego R, Barrios LA, Nelyubina YV, Aromí G, Novikov VV. Unravelling of a [High Spin-Low Spin] ↔ [Low Spin-High Spin] Equilibrium in Spin-Crossover Iron(II) Dinuclear Helicates Using Paramagnetic NMR Spectroscopy. Angew Chem Int Ed Engl 2021; 61:e202110310. [PMID: 34757659 DOI: 10.1002/anie.202110310] [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] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 11/10/2021] [Indexed: 12/11/2022]
Abstract
Spin-crossover between high-spin (HS) and low-spin (LS) states of selected transition metal ions in polynuclear and polymeric compounds is behind their use as multistep switchable materials in breakthrough electronic and spintronic devices. We report the first successful attempt to observe the dynamics of a rarely found broken-symmetry spin state in binuclear complexes, which mixes the states [HS-LS] and [LS-HS] on a millisecond timescale. The slow exchange between these two states, which was identified by paramagnetic NMR spectroscopy in solutions of two spin-crossover iron(II) binuclear helicates that are amenable to molecular design, opens a path to double quantum dot cellular automata for information storage and processing.
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Affiliation(s)
- Dmitry Yu Aleshin
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova str. 28, 11999, Moscow, Russia
| | - Rosa Diego
- Department de Quimica Inorganica and IN2UB, Universitat de Barcelona, Diagonal 647, 08028, Barcelona, Spain
| | - Leoní A Barrios
- Department de Quimica Inorganica and IN2UB, Universitat de Barcelona, Diagonal 647, 08028, Barcelona, Spain
| | - Yulia V Nelyubina
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova str. 28, 11999, Moscow, Russia.,Moscow Institute of Physics and Technology, Institutskiy per. 9, 141700 Dolgoprudny, Moscow region, Russia
| | - Guillem Aromí
- Department de Quimica Inorganica and IN2UB, Universitat de Barcelona, Diagonal 647, 08028, Barcelona, Spain
| | - Valentin V Novikov
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova str. 28, 11999, Moscow, Russia.,Moscow Institute of Physics and Technology, Institutskiy per. 9, 141700 Dolgoprudny, Moscow region, Russia
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Abstract
In an effort to probe the impacts of speciation on spin-state switching, the synthesis and unique solution-phase magnetic properties of [((TIPSC≡C)3tren)Fe(OTf)2] (1) are described. Analysis of the single-crystal X-ray diffraction data shows that the tris(iminoalkyne) ligand coordinates to the iron(II) center through all four nitrogen atoms, while the other two coordination sites are filled by the oxygen atoms from triflate anions. Solid-state variable-temperature (VT) magnetic studies show that 1 remains high-spin (HS) at all temperatures. In the presence of moderately strong coordinating solvents, solvent replaces the two bound triflate counteranions, as observed by 19F NMR spectroscopy and supported by conductivity measurements. VT solution measurements show 1 to be in the HS state when this solvent is oxygen-donating but low-spin (LS) with a nitrogen-donating solvent. In the noncoordinating solvent dichloromethane, both triflates are bound to the iron(II) center at room temperature, but upon cooling, 1 undergoes a coordination change, resulting in the loss of one triflate, as shown by 19F NMR. With the moderately coordinating solvent acetone, triflate dissociation upon cooling results in a spin-switching species with a T1/2 value of 171 K, characterized via 19F NMR, Evans' method, and solution magnetometry measurements. Solution magnetic measurements collected in structurally similar cyclopentanone suggest that the spin-state switching event is exclusive to the acetone environment, suggesting the influence of both the local coordination environment and aggregation. Additionally, a comparison of the solvodoynamic diameters via dynamic light scattering suggests that aggregation of 1 is significantly different in (CH3)2CO and (CD3)2CO, leading to the observation of spin-switching behavior in the former and fully HS behavior in the latter. This study highlights the sensitivity of solution magnetic properties to solvent choice.
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Affiliation(s)
- Brooke N Livesay
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Matthew P Shores
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
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30
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Capel Berdiell I, Davies DJ, Woodworth J, Kulmaczewski R, Cespedes O, Halcrow MA. Structures and Spin States of Iron(II) Complexes of Isomeric 2,6-Di(1,2,3-triazolyl)pyridine Ligands. Inorg Chem 2021; 60:14988-15000. [PMID: 34547208 DOI: 10.1021/acs.inorgchem.1c02404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Iron(II) complex salts of 2,6-di(1,2,3-triazol-1-yl)pyridine (L1) are unexpectedly unstable in undried solvent. This is explained by the isolation of [Fe(L1)4(H2O)2][ClO4]2 and [Fe(NCS)2(L1)2(H2O)2]·L1, containing L1 bound as a monodentate ligand rather than in the expected tridentate fashion. These complexes associate into 44 grid structures through O-H···N hydrogen bonding; a solvate of a related 44 coordination framework, catena-[Cu(μ-L1)2(H2O)2][BF4]2, is also presented. The isomeric ligands 2,6-di(1,2,3-triazol-2-yl)pyridine (L2) and 2,6-di(1H-1,2,3-triazol-4-yl)pyridine (L3) bind to iron(II) in a more typical tridentate fashion. Solvates of [Fe(L3)2][ClO4]2 are low-spin and diamagnetic in the solid state and in solution, while [Fe(L2)2][ClO4]2 and [Co(L3)2][BF4]2 are fully high-spin. Treatment of L3 with methyl iodide affords 2,6-di(2-methyl-1,2,3-triazol-4-yl)pyridine (L4) and 2-(1-methyl-1,2,3-triazol-4-yl)-6-(2-methyl-1,2,3-triazol-4-yl)pyridine (L5). While salts of [Fe(L5)2]2+ are low-spin in the solid state, [Fe(L4)2][ClO4]2·H2O is high-spin, and [Fe(L4)2][ClO4]2·3MeNO2 exhibits a hysteretic spin transition to 50% completeness at T1/2 = 128 K (ΔT1/2 = 6 K). This transition proceeds via a symmetry-breaking phase transition to an unusual low-temperature phase containing three unique cation sites with high-spin, low-spin, and 1:1 mixed-spin populations. The unusual distribution of the spin states in the low-temperature phase reflects "spin-state frustration" of the mixed-spin cation site by an equal number of high-spin and low-spin nearest neighbors. Gas-phase density functional theory calculations reproduce the spin-state preferences of these and some related complexes. These highlight the interplay between the σ-basicity and π-acidity of the heterocyclic donors in this ligand type, which have opposing influences on the molecular ligand field. The Brønsted basicities of L1-L3 are very sensitive to the linkage isomerism of their triazolyl donors, which explains why their iron complex spin states show more variation than the better-known iron(II)/2,6-dipyrazolylpyridine system.
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Affiliation(s)
- Izar Capel Berdiell
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K
| | - Daniel J Davies
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K
| | - Jack Woodworth
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K
| | - Rafal Kulmaczewski
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K
| | - Oscar Cespedes
- School of Physics and Astronomy, University of Leeds, E. C. Stoner Building, Leeds LS2 9JT, U.K
| | - Malcolm A Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K
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Shahid N, Burrows KE, Howard MJ, Pask CM, Cespedes O, McGowan PC, Halcrow MA. Spin-States of Diastereomeric Iron(II) Complexes of 2,6-Bis(thiazolin-2-yl)pyridine (ThioPyBox) Ligands and a Comparison with the Corresponding PyBox Derivatives. Inorg Chem 2021; 60:14336-14348. [PMID: 34472842 DOI: 10.1021/acs.inorgchem.1c01988] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
This report investigates homoleptic iron(II) complexes of thiazolinyl analogues of chiral PyBox tridentate ligands: 2,6-bis(4-phenyl-4,5-dihydrothiazol-2-yl)pyridine (L1Ph), 2,6-bis(4-isopropyl-4,5-dihydrothiazol-2-yl)pyridine (L1iPr), and 2,6-bis(4-tert-butyl-4,5-dihydrothiazol-2-yl)pyridine (L1t-Bu). Crystallographic data imply the larger and more flexible thiazolinyl rings reduce steric clashes between the R substituents in homochiral [Fe((R)-L1R)2]2+ or [Fe((S)-L1R)2]2+ (R = Ph, iPr, or t-Bu), compared to their PyBox (L2R) analogues. Conversely, the larger heterocyclic S atoms are in close contact with the R substituents in heterochiral [Fe((R)-L1Ph)((S)-L1Ph)]2+, giving it a more sterically hindered ligand environment than that in [Fe((R)-L2Ph)((S)-L2Ph)]2+ (L2Ph = 2,6-bis(4-phenyl-4,5-dihydrooxazol-2-yl)pyridine). Preformed [Fe((R)-L1Ph)((S)-L1Ph)]2+ and [Fe((R)-L1iPr)((S)-L1iPr)]2+ do not racemize by ligand redistribution in CD3CN solution, but homochiral [Fe(L1iPr)2]2+ and [Fe(L1t-Bu)2]2+ both undergo partial ligand displacement in that solvent. Homochiral [Fe(L1Ph)2]2+ and [Fe(L1iPr)2]2+ exhibit spin-crossover equilibria in CD3CN, centered at 344 ± 6 K and 277 ± 1 K respectively, while their heterochiral congeners are essentially low-spin within the liquid range of the solvent. These data imply that the diastereomers of [Fe(L1Ph)2]2+ and [Fe(L1iPr)2]2+ show a greater difference in their spin-state behaviors than was previous found for [Fe(L2Ph)2]2+. Gas-phase DFT calculations (B86PW91/def2-SVP) of the [Fe(L1R)2]2+ and [Fe(L2R)2]2+ complexes reproduce most of the observed trends, but they overstabilize the high-spin state of SCO-active [Fe(L1iPr)2]2+ by ca. 1.5 kcal mol-1. This might reflect the influence of intramolecular dispersion interactions on the spin states of these compounds. Attempts to model this with the dispersion-corrected functionals B97-D2 or PBE-D3 were less successful than our original protocol, confirming that the spin states of sterically hindered molecules are a challenging computational problem.
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Affiliation(s)
- Namrah Shahid
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Kay E Burrows
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Mark J Howard
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Christopher M Pask
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Oscar Cespedes
- School of Physics and Astronomy, University of Leeds, E. C. Stoner Building, Leeds LS2 9JT, United Kingdom
| | - Patrick C McGowan
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Malcolm A Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
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32
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Janetzki JT, Zahir FZM, Gable RW, Phonsri W, Murray KS, Goerigk L, Boskovic C. A Convenient DFT-Based Strategy for Predicting Transition Temperatures of Valence Tautomeric Molecular Switches. Inorg Chem 2021; 60:14475-14487. [PMID: 34494829 DOI: 10.1021/acs.inorgchem.1c02273] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The ability to identify promising candidate switchable molecules computationally, prior to synthesis, represents a considerable advance in the development of switchable molecular materials. Even more useful would be the possibility of predicting the switching temperature. Cobalt-dioxolene complexes can exhibit thermally induced valence tautomeric switching between low-spin CoIII-catecholate and high-spin CoII-semiquinonate forms, where the half-temperature (T1/2) is the temperature at which there are equal amounts of the two tautomers. We report the first simple computational strategy for accurately predicting T1/2 values for valence tautomeric complexes. Dispersion-corrected density functional theory (DFT) methods have been applied to the [Co(dbdiox)(dbsq)(N2L)] (dbdiox/dbsq•- = 3,5-di-tert-butyldioxolene/semiquinonate; N2L = diimine) family of valence tautomeric complexes, including the newly reported [Co(dbdiox)(dbsq)(MeO-bpy)] (1) (MeO-bpy = 4,4'-dimethoxy-2,2'-bipyridine). The DFT strategy has been thoroughly benchmarked to experimental data, affording highly accurate spin-distributions and an excellent energy match between experimental and calculated spin-states. Detailed orbital analysis of the [Co(dbdiox)(dbsq)(N2L)] complexes has revealed that the diimine ligand tunes the T1/2 value primarily through π-acceptance. We have established an excellent correlation between experimental T1/2(toluene) values for [Co(dbdiox)(dbsq)(N2L)] complexes and the calculated lowest unoccupied molecular orbital energy of the corresponding diimine ligand. The model affords accurate T1/2(toluene) values for [Co(dbdiox)(dbsq)(N2L)] complexes, with an average error of only 3.7%. This quantitative and simple DFT strategy allows experimentalists to not only rapidly identify proposed VT complexes but also predict the transition temperature. This study lays the groundwork for future in silico screening of candidate switchable molecules prior to experimental investigation, with associated time, cost, and environmental benefits.
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Affiliation(s)
- Jett T Janetzki
- School of Chemistry, University of Melbourne, Victoria 3010, Australia
| | - F Zahra M Zahir
- School of Chemistry, University of Melbourne, Victoria 3010, Australia
| | - Robert W Gable
- School of Chemistry, University of Melbourne, Victoria 3010, Australia
| | - Wasinee Phonsri
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - Keith S Murray
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - Lars Goerigk
- School of Chemistry, University of Melbourne, Victoria 3010, Australia
| | - Colette Boskovic
- School of Chemistry, University of Melbourne, Victoria 3010, Australia
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33
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Attwood M, Akutsu H, Martin L, Blundell TJ, Le Maguere P, Turner SS. Exceptionally high temperature spin crossover in amide-functionalised 2,6-bis(pyrazol-1-yl)pyridine iron(ii) complex revealed by variable temperature Raman spectroscopy and single crystal X-ray diffraction. Dalton Trans 2021; 50:11843-11851. [PMID: 34369514 DOI: 10.1039/d1dt01743h] [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: 11/21/2022]
Abstract
The synthesis of a novel amide-functionalised 2,6-bis(pyrazol-1-yl)pyridine-4-carboxamide ligand (bppCONH2) is described. The complex salts [Fe(bppCONH2)2](BF4)2 and [Fe(bppCONH2)2](ClO4)2 were synthesised and characterised by SQUID magnetometry, differential scanning calorimetry, variable temperature Raman spectroscopy and single crystal X-ray diffraction. DSC measurements of [Fe(bppCONH2)2](BF4)2 indicate a spin-crossover (SCO) transition with T↑ at 481 K and T↓ at 461 K, showing a 20 K hysteresis. DSC for the perchlorate salt shows an SCO transition with T↑ at 459 K and T↓ at 445 K with a 14 K hysteresis. For the BF4- salt analysis of low and high-spin state crystal structures at 101, 290 and 500 K, suggest stabilisation of the low spin state due to the formation of 1D hydrogen-bonded cationic chains. Variable temperature Raman studies of the BF4 salt support the presence of a high temperature SCO. It is speculated that the presence of hysteresis may be attributed to differences in the inter-molecular hydrogen bonding in the low spin and high spin states.
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Affiliation(s)
- Max Attwood
- Department of Chemistry, University of Surrey, Guildford, GU2 7XH, UK.
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34
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Singh S, Brooker S. Correlations between ligand field Δ o, spin crossover T 1/2 and redox potential E pa in a family of five dinuclear helicates. Chem Sci 2021; 12:10919-10929. [PMID: 34447566 PMCID: PMC8372313 DOI: 10.1039/d1sc01458g] [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] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 06/26/2021] [Indexed: 11/21/2022] Open
Abstract
A family of five new bis-bidentate azole-triazole Rat ligands (1,3-bis(5-(azole)-4-isobutyl-4H-1,2,4-triazol-3-yl)benzene), varying in choice of azole (2-imidazole, 4-imidazole, 1-methyl-4-imidazole, 4-oxazole and 4-thiazole), and the corresponding family of spin-crossover (SCO) and redox active triply bridged dinuclear helicates, [FeII 2L3]4+, has been prepared and characterised. X-ray crystal structures show all five Fe(ii) helicates are low spin at 100 K. Importantly, DOSY NMR confirms the intactness of these SCO-active dinuclear helicates in D3-MeCN solution, regardless of HS fraction: γ HS(298 K) = 0-0.81. Variable temperature 1H NMR Evans and UV-vis studies reveal that the helicates are SCO-active in MeCN solution. Indeed, the choice of azole in the Rat ligand used in [Fe2L3]4+ tunes: (a) solution SCO T 1/2 from 247 to 471 K, and (b) reversible redox potential, E m(FeII/III), from 0.25 to 0.67 V for four helicates, whilst one has an irreversible redox process, E pa = 0.78 V, vs. 0.01 M AgNO3/Ag. For the four reversible redox systems, a strong correlation (R 2 = 0.99) is observed between T 1/2 and E pa. Finally, the analogous Ni(ii) helicates have been prepared to obtain Δ o, establishing: (a) the ligand field strength order of the ligands: 4-imidazole (11 420) ∼ 1-methyl-4-imidazole (11 430) < 2-imidazole (11 505) ∼ 4-oxazole (11 516) < 4-thiazole (11 804 cm-1), (b) that Δ o ([NiII 2L3]4+) strongly correlates (R 2 = 0.87) with T 1/2 ([FeII 2L3]4+), and (c) interestingly that Δ o strongly correlates (R 2 = 0.98) with E pa for the four helicates with reversible redox, so the stronger the ligand field strength, the harder it is to oxidise the Fe(ii) to Fe(iii).
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Affiliation(s)
- Sandhya Singh
- Department of Chemistry, The MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago PO Box 56 Dunedin 9054 New Zealand
| | - Sally Brooker
- Department of Chemistry, The MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago PO Box 56 Dunedin 9054 New Zealand
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Nikovskiy IA, Polezhaev AV, Novikov VV, Aleshin DY, Aysin RR, Melnikova EK, Carrella LM, Rentschler E, Nelyubina YV. Spin-Crossover in Iron(II) Complexes of N,N′-Disubstituted 2,6-Bis(Pyrazol-3-yl)Pyridines: An Effect of a Distal Substituent in the 2,6-Dibromophenyl Group. Crystals 2021; 11:922. [DOI: 10.3390/cryst11080922] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A series of new bis(pyrazol-3-yl)pyridines (LR) N,N′-disubstituted by 4-functionalized 2,6-dibromophenyl groups have been synthesized to study the effect of a distal substituent on the spin-crossover (SCO) behaviour of the iron(II) complexes [Fe(LR)2](ClO4)2 by variable-temperature magnetometry, NMR spectroscopy, and X-ray diffraction. The SCO-assisting tendency of the substituents with different electronic and steric properties (i.e., the bromine atom and the methyl group) in the para-position of the 2,6-dibromophenyl group is discussed. Together with earlier reported SCO-active iron(II) complexes with N,N′-disubstituted bis(pyrazol-3-yl)pyridines, these new complexes open the way for this family of SCO compounds to emerge as an effective ‘tool’ in revealing structure–function relations, a prerequisite for successful molecular design of switchable materials for future breakthrough applications in sensing, switching, and memory devices.
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Galadzhun I, Kulmaczewski R, Cespedes O, Halcrow MA. Iron/2,6‐Di(pyrazol‐1‐yl)pyridine Complexes with a Discotic Pattern of Alkyl or Alkynyl Substituents. Eur J Inorg Chem 2021. [DOI: 10.1002/ejic.202100435] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Iurii Galadzhun
- School of Chemistry University of Leeds Woodhouse Lane Leeds LS2 9JT UK
| | | | - Oscar Cespedes
- School of Physics and Astronomy University of Leeds EC Stoner Building Leeds LS2 9JT UK
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37
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Denisov GL, Nikovskii IA, Aliev TM, Polezhaev AV, Nelyubina YV. Spin State of Cobalt(II) 2,6-Bis(pyrazol-3-yl)pyridine Complex with a Redox-Active Ferrocenyl Substituent. RUSS J COORD CHEM+ 2021. [DOI: 10.1134/s1070328421060014] [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: 11/23/2022]
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38
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Berdiell IC, Kulmaczewski R, Shahid N, Cespedes O, Halcrow MA. The number and shape of lattice solvent molecules controls spin-crossover in an isomorphous series of crystalline solvate salts. Chem Commun (Camb) 2021; 57:6566-6569. [PMID: 34113938 DOI: 10.1039/d1cc02624k] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Crystals of [FeL2][BF4]2·nMeCN (L = N-(2,6-di{pyrazol-1-yl}pyrid-4-yl)acetamide; n = 1 or 2) and [FeL2][ClO4]2·MeCN are isomorphous. When n = 1 the compounds exhibit an abrupt, hysteretic spin-transition below 200 K, but when n = 2 the material remains high-spin on cooling. [FeL2]X2·EtCN (X- = BF4- or ClO4-) are isomorphous with the MeCN solvates and undergo their spin-transition at almost the same temperature. However this now occurs in two-steps via a re-entrant mixed-spin intermediate phase, which correlates with crystallographic ordering of the bent propionitrile molecule.
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Affiliation(s)
- Izar Capel Berdiell
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK. and Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, P.O. Box 1527, Heraklion GR-711 10, Greece
| | - Rafal Kulmaczewski
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK.
| | - Namrah Shahid
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK.
| | - Oscar Cespedes
- School of Physics and Astronomy, University of Leeds, EC Stoner Building, Leeds LS2 9JT, UK
| | - Malcolm A Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK.
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39
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Capel Berdiell I, García-López V, Howard MJ, Clemente-León M, Halcrow MA. The effect of tether groups on the spin states of iron(II)/bis[2,6-di(pyrazol-1-yl)pyridine] complexes. Dalton Trans 2021; 50:7417-7426. [PMID: 33969863 DOI: 10.1039/d1dt01076j] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The synthesis of six 2,6-di(pyrazol-1-yl)pyridine derivatives bearing dithiolane or carboxylic acid tether groups is described: [2,6-di(pyrazol-1-yl)pyrid-4-yl]methyl (R)-lipoate (L1), 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxamido]ethyl (R)-lipoate (L2), 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxy]ethyl (R)-lipoate (L3), N-([2,6-di(pyrazol-1-yl)pyrid-4-ylsulfanyl]-2-aminoethyl (R)-lipoamide (L4), 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxamido]acetic acid (L5) and 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxamido]propionic acid (L6). The iron(ii) perchlorate complexes of all the new ligands exhibit gradual thermal spin-crossover (SCO) in the solid state above room temperature, except L4 whose complex remains predominantly high-spin. Crystalline [Fe(L6)2][ClO4]2·2MeCN contains three unique cation sites which alternate within hydrogen-bonded chains, and undergo gradual SCO at different temperatures upon warming. The SCO midpoint temperature (T1/2) of the complexes in CD3CN solution ranges between 208-274 K, depending on the functional group linking the tether groups to the pyridyl ring. This could be useful for predicting how these complexes might behave when deposited on gold or silica surfaces.
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Affiliation(s)
- Izar Capel Berdiell
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT.
| | - Victor García-López
- Instituto de Ciencia Molecular, Universidad de Valencia, Catedrático José Beltrán 2, 46980, Spain
| | - Mark J Howard
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT.
| | - Miguel Clemente-León
- Instituto de Ciencia Molecular, Universidad de Valencia, Catedrático José Beltrán 2, 46980, Spain
| | - Malcolm A Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT.
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40
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Schönfeld S, Bauer W, Thallmair S, Hörner G, Weber B. Running in the Family: Molecular Factors controlling Spin Crossover of Iron(II) Complexes with Schiff‐base like Ligands. Z Anorg Allg Chem 2021. [DOI: 10.1002/zaac.202000409] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Sophie Schönfeld
- Department of Chemistry University of Bayreuth Universitätsstraße 30 NWI 95440 Bayreuth Germany
| | - Wolfgang Bauer
- Department of Chemistry University of Bayreuth Universitätsstraße 30 NWI 95440 Bayreuth Germany
| | - Sebastian Thallmair
- Department of Chemistry University of Bayreuth Universitätsstraße 30 NWI 95440 Bayreuth Germany
- Present address: Frankfurt Institute for Advanced Studies Ruth-Moufang-Straße 1 60438 Frankfurt am Main Germany
| | - Gerald Hörner
- Department of Chemistry University of Bayreuth Universitätsstraße 30 NWI 95440 Bayreuth Germany
| | - Birgit Weber
- Department of Chemistry University of Bayreuth Universitätsstraße 30 NWI 95440 Bayreuth Germany
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41
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Kulmaczewski R, Howard MJ, Halcrow MA. Influence of ligand substituent conformation on the spin state of an iron(II)/di(pyrazol-1-yl)pyridine complex. Dalton Trans 2021; 50:3464-3467. [PMID: 33660725 DOI: 10.1039/d1dt00590a] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The temperature of the solution-phase spin-crossover equilibrium in iron(ii) complexes of 4-alkylsulfanyl-2,6-di{pyrazol-1-yl}pyridine (bppSR) complexes depends strongly on the alkylsulfanyl substituent. DFT calculations imply this reflects the conformation of the alkylsulfanyl groups, which lie perpendicular to the heterocyclic ligand donors in [Fe(bppStBu)2]2+ but are oriented co-planar with the ligand core for smaller SR substituents.
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Affiliation(s)
- Rafal Kulmaczewski
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT.
| | - Mark J Howard
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT.
| | - Malcolm A Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT.
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42
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Wang RG, Meng YS, Gao FF, Gao WQ, Liu CH, Li A, Liu T, Zhu YY. Ligand symmetry significantly affects spin crossover behaviour in isomeric [Fe(pybox) 2] 2+ complexes. Dalton Trans 2021; 50:3369-3378. [PMID: 33595584 DOI: 10.1039/d0dt03978k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [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 understanding of the correlation between the spin-state behaviour and the structural features in transition-metal complexes is of pronounced importance to the design of spin crossover compounds with high performance. However, the study of the influence of ligand symmetry on the spin crossover properties is still limited due to the shortage of suitable structural systems. Herein we report the magneto-structural correlations of three mononuclear Fe(ii) isomers with respect to their ligand symmetry. In this work, two phenyl-substituted meso and optically pure pybox ligands were employed to construct meso (1), optically pure (2), and racemic (3) ligand types of [Fe(pybox)2]2+ complexes. Their magnetic susceptibilities were measured via temperature-dependent paramagnetic 1H NMR spectroscopy. We fitted the midpoint temperatures of the transition (T1/2) of 260 K for 1(ClO4), 247 K for 2(ClO4), and 281 K for 3(ClO4). The influence of structural symmetry on spin crossover was rationalized through density functional theory calculations. The optimized structures of [Fe(pybox)2]2+ complex cations show that the geometric distortion of the central FeN6 coordination sphere is mainly caused by the steric congestions between adjacent phenyl substituents. In these compounds, there is a distinct correlation that more steric congestions produce larger coordination distortion and favor the electron configuration in the high-spin state, which reflects in the increase of T1/2. Additionally, the influence of the counter anion and lattice solvent on the meso series compounds was inspected. It is revealed that multiple factors dominate the spin-state behaviour in the solid state. This work provides deep insight into the effect of ligand symmetry on the spin transition behaviour in spin crossover compounds. It demonstrates that molecular symmetry should be considered in the design of spin crossover compounds.
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Affiliation(s)
- Run-Guo Wang
- School of Chemistry and Chemical Engineering, Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009, China.
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43
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Deorukhkar N, Besnard C, Guénée L, Piguet C. Tuning spin-crossover transition temperatures in non-symmetrical homoleptic meridional/facial [Fe(didentate) 3] 2+ complexes: what for and who cares about it? Dalton Trans 2021; 50:1206-1223. [PMID: 33404561 DOI: 10.1039/d0dt03828h] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [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 [FeN6] chromophores found in [Fe(didentate)3]2+ complexes, where didentate is a non-symmetrical 2-(6-membered-heterocyclic ring)-benzimidazole ligand (Lk), exist as mixtures of two geometrical mer (C1-symmetry) and fac (C3-symmetry) isomers. Specific alkyl-substituted six-membered heterocyclic rings connected to the benzimidazole unit (pyridines in ligands L1-L3, pyrazines in L4-L5 and pyrimidines in L6-L7) control the ligand field strength and the electron delocalization so that [FeII(Lk)3]2+ display tunable thermally-induced spin transitions in solution. Thermodynamic, spectroscopic (UV-Vis, NMR) and magnetic studies in solution demonstrate that [Fe(L6)3]2+ (L6 = 1-methyl-2-(pyrimidin-2-yl)-1H-benzo[d]imidazole) exhibits a close to room temperature spin transition (T1/2 = 273(3) K) combined with a high stability formation constant ( in acetonitrile), which makes this complex suitable for the potential modulation of lanthanide-based luminescence in polymetallic helicates. A novel method is proposed for assigning specific thermodynamic spin crossover parameters to fac-[Fe(L6)3]2+ and mer-[Fe(L6)3]2+ isomers in solution. The observed difference relies mainly on the entropic content ΔS-ΔS = 11(1) J mol-1 K-1, which favors the spin transition for the meridional isomer. Intermolecular interactions occurring in the crystalline state largely overcome minor thermodynamic trends operating in diluted solutions and a single configurational isomer is usually observed in the solid state. Among the thirteen solved crystal structures 1-13 containing the [M(Lk)3]2+ cations (M = Fe, Ni, Zn, Lk = L6-L7), pure meridional isomers are observed six times, pure facial isomers also six times and a mixture (44% mer and 56% fac) is detected only once. Solid-state magnetic data recorded for the FeII complexes show the operation of slightly cooperative spin transitions in 7 (fac-[Fe(L6)3]2+) and 12 (mer-[Fe(L7)3]2+). For the meridional isomer in 6, a two-step spin state transition curve, associated with two phase transitions, is detected.
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Affiliation(s)
- Neel Deorukhkar
- Department of Inorganic and Analytical Chemistry, University of Geneva, 30 quai E. Ansermet, CH-1211 Geneva 4, Switzerland.
| | - Céline Besnard
- Laboratory of Crystallography, University of Geneva, 24 quai E. Ansermet, CH-1211 Geneva 4, Switzerland
| | - Laure Guénée
- Laboratory of Crystallography, University of Geneva, 24 quai E. Ansermet, CH-1211 Geneva 4, Switzerland
| | - Claude Piguet
- Department of Inorganic and Analytical Chemistry, University of Geneva, 30 quai E. Ansermet, CH-1211 Geneva 4, Switzerland.
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44
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Kulmaczewski R, Bamiduro F, Shahid N, Cespedes O, Halcrow MA. Structural Transformations and Spin-Crossover in [FeL 2 ] 2+ Salts (L=4-{tert-Butylsulfanyl}-2,6-di{pyrazol-1-yl}pyridine): The Influence of Bulky Ligand Substituents. Chemistry 2021; 27:2082-2092. [PMID: 33073890 DOI: 10.1002/chem.202004072] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [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: 09/08/2020] [Revised: 10/16/2020] [Indexed: 11/06/2022]
Abstract
4-(tert-Butylsulfanyl)-2,6-di(pyrazol-1-yl)pyridine (L) was obtained in low yield from a one-pot reaction of 2,4,6-trifluoropyridine with 2-methylpropane-2-thiolate and sodium pyrazolate in a 1:1:2 ratio. The materials [FeL2 ][BF4 ]2 ⋅solv (1[BF4 ]2 ⋅solv) and [FeL2 ][ClO4 ]2 ⋅solv (1[ClO4 ]2 ⋅solv; solv=MeNO2 , MeCN or Me2 CO) exhibit a variety of structures and spin-state behaviors including thermal spin-crossover (SCO). Solvent loss on heating 1[BF4 ]2 ⋅x MeNO2 (x≈2.3) occurs in two steps. The intermediate phase exhibits hysteretic SCO around 250 K, involving a "reverse-SCO" step in its warming cycle at a scan rate of 5 K min-1 . The reverse-SCO is not observed in a slower 1 K min-1 measurement, however, confirming its kinetic nature. The final product [FeL2 ][BF4 ]2 ⋅0.75 MeNO2 was crystallographically characterized, and shows abrupt but incomplete SCO at 172 K which correlates with disorder of an L ligand. The asymmetric unit of 1[BF4 ]2 ⋅y Me2 CO (y≈1.6) contains five unique complex molecules, four of which undergo gradual SCO in at least two discrete steps. Low-spin 1[ClO4 ]2 ⋅0.5 Me2 CO is not isostructural with its BF4 - congener, and undergoes single-crystal-to-single-crystal solvent loss with a tripling of the crystallographic unit cell volume, while retaining the P 1 ‾ space group. Three other solvate salts undergo gradual thermal SCO. Two of these are isomorphous at room temperature, but transform to different low-temperature phases when the materials are fully low-spin.
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Affiliation(s)
- Rafal Kulmaczewski
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Faith Bamiduro
- School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Namrah Shahid
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Oscar Cespedes
- School of Physics and Astronomy, University of Leeds, E. C. Stoner Building, Leeds, LS2 9JT, UK
| | - Malcolm A Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
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45
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Bondì L, Rodríguez-Jiménez S, Feltham HLC, Garden AL, Brooker S. Probing the generality of spin crossover complex T½vs. ligand 15N NMR chemical shift correlations: towards predictable tuning. Inorg Chem Front 2021. [DOI: 10.1039/d1qi00919b] [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: 11/21/2022]
Abstract
A study of 6 families (42 members) demonstrates that within a family the easily calculated 15N-NMR values of ligands enable predictable tuning of T1/2 in the corresponding complexes, except for 2 families with weakly influencing meta-substituents.
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Affiliation(s)
- Luca Bondì
- Department of Chemistry and the MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Department of Chemistry ‘Ugo Schiff’ and INSTM Research Unit, University of Florence, 50019 Sesto Fiorentino, Italy
| | - Santiago Rodríguez-Jiménez
- Department of Chemistry and the MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Humphrey L. C. Feltham
- Department of Chemistry and the MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Anna L. Garden
- Department of Chemistry and the MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Sally Brooker
- Department of Chemistry and the MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
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46
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Galadzhun I, Kulmaczewski R, Shahid N, Cespedes O, Howard MJ, Halcrow MA. The flexibility of long chain substituents influences spin-crossover in isomorphous lipid bilayer crystals. Chem Commun (Camb) 2021; 57:4039-4042. [DOI: 10.1039/d1cc01073e] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
These two compounds are isomorphous but show different spin-state behaviour on cooling. This may be influenced by the packing of alkyl vs. alkynyl chains in the solid state.
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Affiliation(s)
| | | | - Namrah Shahid
- School of Chemistry
- University of Leeds
- Woodhouse Lane
- Leeds
- UK
| | - Oscar Cespedes
- School of Physics and Astronomy
- University of Leeds
- Leeds LS2 9JT
- UK
| | - Mark J. Howard
- School of Chemistry
- University of Leeds
- Woodhouse Lane
- Leeds
- UK
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47
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Usman M, Chibuike M, Patil D, Rigin S, Zhang S, Wu Y, Lindline J, Timofeeva TV. Magnetic behaviour of 3D metal−organic frameworks constructed via 1,2,4,5-benzenetetracarboxylate linker and 4f Ce(III) or 3d Fe(III) metal nodes. INORG CHEM COMMUN 2020. [DOI: 10.1016/j.inoche.2020.108261] [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: 11/17/2022]
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48
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Milocco F, de Vries F, Bartels IMA, Havenith RWA, Cirera J, Demeshko S, Meyer F, Otten E. Electronic Control of Spin-Crossover Properties in Four-Coordinate Bis(formazanate) Iron(II) Complexes. J Am Chem Soc 2020; 142:20170-20181. [PMID: 33197175 PMCID: PMC7705964 DOI: 10.1021/jacs.0c10010] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [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: 12/20/2022]
Abstract
![]()
The
transition between spin states in d-block metal complexes has
important ramifications for their structure and reactivity, with applications
ranging from information storage materials to understanding catalytic
activity of metalloenzymes. Tuning the ligand field (ΔO) by steric and/or electronic effects has provided spin-crossover
compounds for several transition metals in the periodic table, but
this has mostly been limited to coordinatively saturated metal centers
in octahedral ligand environments. Spin-crossover complexes with low
coordination numbers are much rarer. Here we report a series of four-coordinate,
(pseudo)tetrahedral Fe(II) complexes with formazanate ligands and
demonstrate how electronic substituent effects can be used to modulate
the thermally induced transition between S = 0 and S = 2 spin states in solution. All six compounds undergo
spin-crossover in solution with T1/2 above
room temperature (300–368 K). While structural analysis by
X-ray crystallography shows that the majority of these compounds are
low-spin in the solid state (and remain unchanged upon heating), we
find that packing effects can override this preference and give rise
to either rigorously high-spin (6) or gradual spin-crossover
behavior (5) also in the solid state. Density functional
theory calculations are used to delineate the empirical trends in
solution spin-crossover thermodynamics. In all cases, the stabilization
of the low-spin state is due to the π-acceptor properties of
the formazanate ligand, resulting in an “inverted” ligand
field, with an approximate “two-over-three” splitting
of the d-orbitals and a high degree of metal–ligand covalency
due to metal → ligand π-backdonation. The computational
data indicate that the electronic nature of the para-substituent has a different influence depending on whether it is
present at the C–Ar or N–Ar rings, which is ascribed
to the opposing effect on metal–ligand σ- and π-bonding.
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Affiliation(s)
- Francesca Milocco
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Folkert de Vries
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Imke M A Bartels
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Remco W A Havenith
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.,Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.,Ghent Quantum Chemistry Group, Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281 (S3), B-9000 Gent, Belgium
| | - Jordi Cirera
- Departament de Química Inorgànica i Orgànica and Institut de Recerca de Química Teòrica i Computacional, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
| | - Serhiy Demeshko
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany
| | - Franc Meyer
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany
| | - Edwin Otten
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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49
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Palacios-Corella M, Ramos-Soriano J, Souto M, Ananias D, Calbo J, Ortí E, Illescas BM, Clemente-León M, Martín N, Coronado E. Hexakis-adducts of [60]fullerene as molecular scaffolds of polynuclear spin-crossover molecules. Chem Sci 2020; 12:757-766. [PMID: 34163809 PMCID: PMC8178998 DOI: 10.1039/d0sc05875k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [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: 11/21/2022] Open
Abstract
A family of hexakis-substituted [60]fullerene adducts endowed with the well-known tridentate 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligand for spin-crossover (SCO) systems has been designed and synthesized. It has been experimentally and theoretically demonstrated that these molecular scaffolds are able to form polynuclear SCO complexes in solution. UV-vis and fluorescence spectroscopy studies have allowed monitoring of the formation of up to six Fe(ii)–bpp SCO complexes. In addition, DFT calculations have been performed to model the different complexation environments and simulate their electronic properties. The complexes retain SCO properties in the solid state exhibiting both thermal- and photoinduced spin transitions, as confirmed by temperature-dependent magnetic susceptibility and Raman spectroscopy measurements. The synthesis of these complexes demonstrates that [60]fullerene hexakis-adducts are excellent and versatile platforms to develop polynuclear SCO systems in which a fullerene core is surrounded by a SCO molecular shell. Polynuclear spin-crossover molecules showing both thermal and photoinduced spin transitions have been prepared using a [60]fullerene hexakis-adduct endowed with Fe(ii) complexes of tridentate 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligand.![]()
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Affiliation(s)
- Mario Palacios-Corella
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia Catedrático José Beltrán 2 46980 Paterna Spain
| | - Javier Ramos-Soriano
- Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense 28040 Madrid Spain
| | - Manuel Souto
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia Catedrático José Beltrán 2 46980 Paterna Spain .,CICECO-Aveiro Institute of Materials, Department of Chemistry, Universidade de Aveiro Campus Universitário de Santiago 3810-193 Aveiro Portugal
| | - Duarte Ananias
- CICECO-Aveiro Institute of Materials, Department of Chemistry, Universidade de Aveiro Campus Universitário de Santiago 3810-193 Aveiro Portugal
| | - Joaquín Calbo
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia Catedrático José Beltrán 2 46980 Paterna Spain
| | - Enrique Ortí
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia Catedrático José Beltrán 2 46980 Paterna Spain
| | - Beatriz M Illescas
- Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense 28040 Madrid Spain
| | - Miguel Clemente-León
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia Catedrático José Beltrán 2 46980 Paterna Spain
| | - Nazario Martín
- Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense 28040 Madrid Spain.,IMDEA-Nanoscience C/Faraday 9, Campus de Cantoblanco 28049 Madrid Spain
| | - Eugenio Coronado
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia Catedrático José Beltrán 2 46980 Paterna Spain
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50
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Bondì L, Garden AL, Jerabek P, Totti F, Brooker S. Quantitative and Chemically Intuitive Evaluation of the Nature of M-L Bonds in Paramagnetic Compounds: Application of EDA-NOCV Theory to Spin Crossover Complexes. Chemistry 2020; 26:13677-13685. [PMID: 32671882 PMCID: PMC7702084 DOI: 10.1002/chem.202002146] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/25/2020] [Indexed: 11/16/2022]
Abstract
To improve understanding of M-L bonds in 3d transition metal complexes, analysis by energy decomposition analysis and natural orbital for chemical valence model (EDA-NOCV) is desirable as it provides a full, quantitative and chemically intuitive ab initio description of the M-L interactions. In this study, a generally applicable fragmentation and computational protocol was established and validated by using octahedral spin crossover (SCO) complexes, as the transition temperature (T1/2 ) is sensitive to subtle changes in M-L bonding. Specifically, EDA-NOCV analysis of Fe-N bonds in five [FeII (Lazine )2 (NCBH3 )2 ], in both low-spin (LS) and paramagnetic high-spin (HS) states led to: 1) development of a general, widely applicable, corrected M+L6 fragmentation, tested against a family of five LS [FeII (Lazine )3 ](BF4 )2 complexes; this confirmed that three Lazine are stronger ligands (ΔEorb,σ+π =-370 kcal mol-1 ) than 2 Lazine +2 NCBH3 (=-335 kcal mol-1 ), as observed. 2) Analysis of Fe-L bonding on LS→HS, reveals more ionic (ΔEelstat ) and less covalent (ΔEorb ) character (ΔEelstat :ΔEorb 55:45 LS→64:36 HS), mostly due to a big drop in σ (ΔEorb,σ ↓50 %; -310→-145 kcal mol-1 ), and a drop in π contributions (ΔEorb,π ↓90 %; -30→-3 kcal mol-1 ). 3) Strong correlation of observed T1/2 and ΔEorb,σ+π , for both LS and HS families (R2 =0.99 LS, R2 =0.95 HS), but no correlation of T1/2 and ΔΔEorb,σ+π (LS-HS) (R2 =0.11). Overall, this study has established and validated an EDA-NOCV protocol for M-L bonding analysis of any diamagnetic or paramagnetic, homoleptic or heteroleptic, octahedral transition metal complex. This new and widely applicable EDA-NOCV protocol holds great promise as a predictive tool.
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Affiliation(s)
- Luca Bondì
- Department of Chemistry andMacDiarmid Institute of Advanced Materials and NanotechnologyUniversity of OtagoPO Box 56Dunedin9054New Zealand
- Department of Chemistry “Ugo Schiff” and INSTM Research UnitUniversity of Florence50019Sesto FiorentinoItaly
| | - Anna L. Garden
- Department of Chemistry andMacDiarmid Institute of Advanced Materials and NanotechnologyUniversity of OtagoPO Box 56Dunedin9054New Zealand
| | - Paul Jerabek
- Centre for Theoretical Chemistry and PhysicsThe New Zealand Institute for Advanced Study andthe Institute for Natural and Mathematical SciencesMassey UniversityAucklandNew Zealand
- Department of NanotechnologyHelmholtz Centre for Materials and Coastal ResearchMax-Planck-Straße 121502GeesthachtGermany
| | - Federico Totti
- Department of Chemistry “Ugo Schiff” and INSTM Research UnitUniversity of Florence50019Sesto FiorentinoItaly
| | - Sally Brooker
- Department of Chemistry andMacDiarmid Institute of Advanced Materials and NanotechnologyUniversity of OtagoPO Box 56Dunedin9054New Zealand
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