1
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Neumann T, Thompson BC, Hebron D, Graycon DM, Collauto A, Roessler MM, Wilson DWN, Musgrave RA. Heterobimetallic 3d-4f complexes supported by a Schiff-base tripodal ligand. Dalton Trans 2024. [PMID: 38808633 DOI: 10.1039/d3dt03760f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2024]
Abstract
Complexes featuring multiple metal centres are of growing interest regarding metal-metal cooperation and its tuneability. Here the synthesis and characterisation of heterobimetallic complexes of a 3d metal (4: Mn, 5: Co) and lanthanum supported by a (1,1,1-tris[(3-methoxysalicylideneamino)methyl]ethane) ligand is reported, as well as discussion of their electronic structure via electron paramagnetic resonance (EPR) spectroscopy, electrochemical experiments and computational studies. Competitive binding experiments of the ligand and various metal salts unequivocally demonstrate that in these heterobimetallic complexes the 3d metal (Mn, Co) selectively occupies the κ6-N3O3 binding site of the ligand, whilst La occupies the κ6-O6 metal binding site in line with their relative oxophilicities. EPR spectroscopy supported by density functional theory analysis indicates that the 3d metal is high spin in both cases (S = 5/2 (Mn), 3/2 (Co)). Cyclic voltammetry studies on the Mn/La and Co/La bimetallic complexes revealed a quasi-reversible Mn2+/3+ redox process and poorly-defined irreversible oxidation events respectively.
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Affiliation(s)
- Till Neumann
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London, SE1 1DB, UK.
| | - Benedict C Thompson
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London, SE1 1DB, UK.
| | - Denny Hebron
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London, SE1 1DB, UK.
| | - Daniel M Graycon
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London, SE1 1DB, UK.
| | - Alberto Collauto
- Molecular Sciences Research Hub, Department of Chemistry, Imperial College London, 82 Wood Lane, London, W12 0BZ, UK
| | - Maxie M Roessler
- Molecular Sciences Research Hub, Department of Chemistry, Imperial College London, 82 Wood Lane, London, W12 0BZ, UK
| | - Daniel W N Wilson
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London, SE1 1DB, UK.
| | - Rebecca A Musgrave
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London, SE1 1DB, UK.
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2
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Karnes JP, Kumar A, Hopkins Leseberg JA, Day VW, Blakemore JD. Trivalent Cations Slow Electron Transfer to Macrocyclic Heterobimetallic Complexes. Inorg Chem 2024; 63:8710-8729. [PMID: 38669449 DOI: 10.1021/acs.inorgchem.4c00230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2024]
Abstract
Incorporation of secondary redox-inactive cations into heterobimetallic complexes is an attractive strategy for modulation of metal-centered redox chemistry, but quantification of the consequences of incorporating strongly Lewis acidic trivalent cations has received little attention. Here, a family of seven heterobimetallic complexes that pair a redox-active nickel center with La3+, Y3+, Lu3+, Sr2+, Ca2+, K+, and Na+ (in the form of their triflate salts) have been prepared on a heteroditopic ligand platform to understand how chemical behavior varies across the comprehensive series. Structural data from X-ray diffraction analysis demonstrate that the positions adopted by the secondary cations in the crown-ether-like site of the ligand relative to nickel are dependent primarily on the secondary cations' ionic radii and that the triflate counteranions are bound to the cations in all cases. Electrochemical data, in concert with electron paramagnetic resonance studies, show that nickel(II)/nickel(I) redox is modulated by the secondary metals; the heterogeneous electron-transfer rate is diminished for the derivatives incorporating trivalent metals, an effect that is dependent on steric crowding about the nickel metal center and that was quantified here with a topographical free-volume analysis. As related analyses carried out here on previously reported systems bear out similar relationships, we conclude that the placement and identity of both the secondary metal cations and their associated counteranions can afford unique changes in the (electro)chemical behavior of heterobimetallic species.
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Affiliation(s)
- Joseph P Karnes
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Amit Kumar
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Julie A Hopkins Leseberg
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Victor W Day
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - James D Blakemore
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
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3
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Alvarez-Hernandez JL, Zhang X, Cui K, Deziel AP, Hammes-Schiffer S, Hazari N, Piekut N, Zhong M. Long-range electrostatic effects from intramolecular Lewis acid binding influence the redox properties of cobalt-porphyrin complexes. Chem Sci 2024; 15:6800-6815. [PMID: 38725508 PMCID: PMC11077573 DOI: 10.1039/d3sc06177a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 04/02/2024] [Indexed: 05/12/2024] Open
Abstract
A CoII-porphyrin complex (1) with an appended aza-crown ether for Lewis acid (LA) binding was synthesized and characterized. NMR spectroscopy and electrochemistry show that cationic group I and II LAs (i.e., Li+, Na+, K+, Ca2+, Sr2+, and Ba2+) bind to the aza-crown ether group of 1. The binding constant for Li+ is comparable to that observed for a free aza-crown ether. LA binding causes an anodic shift in the CoII/CoI couple of between 10 and 40 mV and also impacts the CoIII/CoII couple. The magnitude of the anodic shift of the CoII/CoI couple varies linearly with the strength of the LA as determined by the pKa of the corresponding metal-aqua complex, with dications giving larger shifts than monocations. The extent of the anodic shift of the CoII/CoI couple also increases as the ionic strength of the solution decreases. This is consistent with electric field effects being responsible for the changes in the redox properties of 1 upon LA binding and provides a novel method to tune the reduction potential. Density functional theory calculations indicate that the bound LA is 5.6 to 6.8 Å away from the CoII ion, demonstrating that long-range electrostatic effects, which do not involve changes to the primary coordination sphere, are responsible for the variations in redox chemistry. Compound 1 was investigated as a CO2 reduction electrocatalyst and shows high activity but rapid decomposition.
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Affiliation(s)
| | - Xiaowei Zhang
- Department of Chemical and Environmental Engineering, Yale University New Haven CT 06520 USA
| | - Kai Cui
- Department of Chemistry, Princeton University Princeton NJ 08544 USA
| | | | | | - Nilay Hazari
- Department of Chemistry, Yale University New Haven CT 06520 USA
| | - Nicole Piekut
- Department of Chemistry, Yale University New Haven CT 06520 USA
| | - Mingjiang Zhong
- Department of Chemical and Environmental Engineering, Yale University New Haven CT 06520 USA
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4
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Long C, Ray M. Water-soluble chiral coordination polymers of Li +, Na +, K +, and Ba 2+ with an anionic iron(III) complex of a L-threonine derivative and a significant red shift of visible spectra with Al 3+ salt. Dalton Trans 2024; 53:6642-6652. [PMID: 38525650 DOI: 10.1039/d3dt03945e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/26/2024]
Abstract
Four salts of an anionic iron(III) bis-complex, [Fe(LL-thr)2]1-, were synthesized from water or methanol. H2LL-thr is a tridentate ligand derived from the L-threonine amino acid, and the cations used are Li+ (1), Na+ (2), K+ (3), and Ba2+ (4). Single-crystal X-ray diffraction showed that all the complexes are coordination polymers of different dimensionalities. The iron(III) complex binds to cations through its coordinated phenolate and non-coordinated carboxylate oxygen atoms. While Li+ forms a linear chain, all others have a pair of bridged cations intervening the iron(III) complexes. The 3D network of Ba2+ salt has a sizeable solvent-accessible space occupied by aquated chloride ions. The differences in circular dichroism (CD) spectra and significantly lower conductance values in water and methanol support partial retention of the polymeric nature in methanol. The visible spectra of 4 in methanol or water showed an ∼10 nm shift of the charge transfer bands from 3. However, the addition of Al3+ salt to 2 showed a significant colour shift. Further investigation confirmed that the colour shift is due to partial protonation of the complex with protons generated from salt hydrolysis. Most reports on visual aluminium detection consider aluminium's binding as the shift's source. The present results show that protonation due to hydrolysis of aluminium salt can skew the observation.
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Affiliation(s)
- Chanreingam Long
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, India.
| | - Manabendra Ray
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, India.
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5
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Lionetti D, Suseno S, Shiau AA, de Ruiter G, Agapie T. Redox Processes Involving Oxygen: The Surprising Influence of Redox-Inactive Lewis Acids. JACS AU 2024; 4:344-368. [PMID: 38425928 PMCID: PMC10900226 DOI: 10.1021/jacsau.3c00675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 12/12/2023] [Accepted: 12/13/2023] [Indexed: 03/02/2024]
Abstract
Metalloenzymes with heteromultimetallic active sites perform chemical reactions that control several biogeochemical cycles. Transformations catalyzed by such enzymes include dioxygen generation and reduction, dinitrogen reduction, and carbon dioxide reduction-instrumental transformations for progress in the context of artificial photosynthesis and sustainable fertilizer production. While the roles of the respective metals are of interest in all these enzymatic transformations, they share a common factor in the transfer of one or multiple redox equivalents. In light of this feature, it is surprising to find that incorporation of redox-inactive metals into the active site of such an enzyme is critical to its function. To illustrate, the presence of a redox-inactive Ca2+ center is crucial in the Oxygen Evolving Complex, and yet particularly intriguing given that the transformation catalyzed by this cluster is a redox process involving four electrons. Therefore, the effects of redox inactive metals on redox processes-electron transfer, oxygen- and hydrogen-atom transfer, and O-O bond cleavage and formation reactions-mediated by transition metals have been studied extensively. Significant effects of redox inactive metals have been observed on these redox transformations; linear free energy correlations between Lewis acidity and the redox properties of synthetic model complexes are observed for several reactions. In this Perspective, these effects and their relevance to multielectron processes will be discussed.
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Affiliation(s)
| | - Sandy Suseno
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Angela A. Shiau
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Graham de Ruiter
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Theodor Agapie
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
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6
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Rickmeyer K, Huber M, Hess CR. Influence of a neighbouring Cu centre on electro- and photocatalytic CO 2 reduction by Fe-Mabiq. Chem Commun (Camb) 2024; 60:819-822. [PMID: 38113085 DOI: 10.1039/d3cc04777f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
Electrocatalytic and photocatalytic CO2 reduction by a heterobimetallic Cu/Fe-Mabiq complex were examined and compared to the monometallic [Fe(Mabiq)]+. The neighbouring Cu-Xantphos unit leads to marked changes in the electrocatalytic mechanism and enhanced photocatalytic performance.
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Affiliation(s)
- Kerstin Rickmeyer
- Department of Chemistry and Catalysis Research Center (CRC), Technical University of Munich, Garching 85748, Germany
- Faculty of Chemistry and Pharmacy, University of Regensburg, Regensburg 93053, Germany.
| | - Matthias Huber
- Department of Chemistry and Catalysis Research Center (CRC), Technical University of Munich, Garching 85748, Germany
- Faculty of Chemistry and Pharmacy, University of Regensburg, Regensburg 93053, Germany.
| | - Corinna R Hess
- Department of Chemistry and Catalysis Research Center (CRC), Technical University of Munich, Garching 85748, Germany
- Faculty of Chemistry and Pharmacy, University of Regensburg, Regensburg 93053, Germany.
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7
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Marciesky M, Aga DS, Bradley IM, Aich N, Ng C. Mechanisms and Opportunities for Rational In Silico Design of Enzymes to Degrade Per- and Polyfluoroalkyl Substances (PFAS). J Chem Inf Model 2023; 63:7299-7319. [PMID: 37981739 PMCID: PMC10716909 DOI: 10.1021/acs.jcim.3c01303] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 10/17/2023] [Accepted: 10/18/2023] [Indexed: 11/21/2023]
Abstract
Per and polyfluoroalkyl substances (PFAS) present a unique challenge to remediation techniques because their strong carbon-fluorine bonds make them difficult to degrade. This review explores the use of in silico enzymatic design as a potential PFAS degradation technique. The scope of the enzymes included is based on currently known PFAS degradation techniques, including chemical redox systems that have been studied for perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) defluorination, such as those that incorporate hydrated electrons, sulfate, peroxide, and metal catalysts. Bioremediation techniques are also discussed, namely the laccase and horseradish peroxidase systems. The redox potential of known reactants and enzymatic radicals/metal-complexes are then considered and compared to potential enzymes for degrading PFAS. The molecular structure and reaction cycle of prospective enzymes are explored. Current knowledge and techniques of enzyme design, particularly radical-generating enzymes, and application are also discussed. Finally, potential routes for bioengineering enzymes to enable or enhance PFAS remediation are considered as well as the future outlook for computational exploration of enzymatic in situ bioremediation routes for these highly persistent and globally distributed contaminants.
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Affiliation(s)
- Melissa Marciesky
- Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, United States
| | - Diana S Aga
- Department of Chemistry, State University of New York at Buffalo, Buffalo, New York 14260, United States
| | - Ian M Bradley
- Department of Civil, Structural, and Environmental Engineering, State University of New York at Buffalo, Buffalo, New York 14228, United States
- Research and Education in Energy, Environmental and Water (RENEW) Institute, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Nirupam Aich
- Department of Civil and Environmental Engineering, University of Nebraska─Lincoln, Lincoln, Nebraska 68588-0531, United States
| | - Carla Ng
- Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, United States
- Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
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8
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Boggiano AC, Studvick CM, Steiner A, Bacsa J, Popov IA, La Pierre HS. Structural distortion by alkali metal cations modulates the redox and electronic properties of Ce 3+ imidophosphorane complexes. Chem Sci 2023; 14:11708-11717. [PMID: 37920331 PMCID: PMC10619540 DOI: 10.1039/d3sc04262f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 09/15/2023] [Indexed: 11/04/2023] Open
Abstract
A series of Ce3+ complexes with counter cations ranging from Li to Cs are presented. Cyclic voltammetry data indicate a significant dependence of the oxidation potential on the alkali metal identity. Analysis of the single-crystal X-ray diffraction data indicates that the degree of structural distortion of the secondary coordination sphere is linearly correlated with the measured oxidation potential. Solution electronic absorption spectroscopy confirms that the structural distortion is reflected in the solution structure. Computational studies further validate this analysis, deciphering the impact of alkali metal cations on the Ce atomic orbital contributions, differences in energies of Ce-dominant molecular orbitals, energy shift of the 4f-5d electronic transitions, and degree of structural distortions. In sum, the structural impact of the alkali metal cation is demonstrated to modulate the redox and electronic properties of the Ce3+ complexes, and provides insight into the rational tuning of the Ce3+ imidophosphorane complex oxidation potential through alkali metal identity.
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Affiliation(s)
- Andrew C Boggiano
- School of Chemistry and Biochemistry, Georgia Institute of Technology Atlanta Georgia 30332-0400 USA
| | - Chad M Studvick
- Department of Chemistry, The University of Akron Akron Ohio 44325-3601 USA
| | - Alexander Steiner
- Department of Chemistry, University of Liverpool Liverpool L69 7ZD UK
| | - John Bacsa
- School of Chemistry and Biochemistry, Georgia Institute of Technology Atlanta Georgia 30332-0400 USA
| | - Ivan A Popov
- Department of Chemistry, The University of Akron Akron Ohio 44325-3601 USA
| | - Henry S La Pierre
- School of Chemistry and Biochemistry, Georgia Institute of Technology Atlanta Georgia 30332-0400 USA
- Nuclear and Radiological Engineering and Medical Physics Program, School of Mechanical Engineering, Georgia Institute of Technology Atlanta Georgia 30332-0400 USA
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9
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Lindeboom W, Deacy AC, Phanopoulos A, Buchard A, Williams CK. Correlating Metal Redox Potentials to Co(III)K(I) Catalyst Performances in Carbon Dioxide and Propene Oxide Ring Opening Copolymerization. Angew Chem Int Ed Engl 2023; 62:e202308378. [PMID: 37409487 PMCID: PMC10952574 DOI: 10.1002/anie.202308378] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 07/03/2023] [Accepted: 07/05/2023] [Indexed: 07/07/2023]
Abstract
Carbon dioxide copolymerization is a front-runner CO2 utilization strategy but its viability depends on improving the catalysis. So far, catalyst structure-performance correlations have not been straightforward, limiting the ability to predict how to improve both catalytic activity and selectivity. Here, a simple measure of a catalyst ground-state parameter, metal reduction potential, directly correlates with both polymerization activity and selectivity. It is applied to compare performances of 6 new heterodinuclear Co(III)K(I) catalysts for propene oxide (PO)/CO2 ring opening copolymerization (ROCOP) producing poly(propene carbonate) (PPC). The best catalyst shows an excellent turnover frequency of 389 h-1 and high PPC selectivity of >99 % (50 °C, 20 bar, 0.025 mol% catalyst). As demonstration of its utility, neither DFT calculations nor ligand Hammett parameter analyses are viable predictors. It is proposed that the cobalt redox potential informs upon the active site electron density with a more electron rich cobalt centre showing better performances. The method may be widely applicable and is recommended to guide future catalyst discovery for other (co)polymerizations and carbon dioxide utilizations.
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Affiliation(s)
- Wouter Lindeboom
- Department ChemistryUniversity of OxfordChemistry Research Laboratory12 Mansfield RoadOxfordOX1 3TAUK
| | - Arron C. Deacy
- Department ChemistryUniversity of OxfordChemistry Research Laboratory12 Mansfield RoadOxfordOX1 3TAUK
| | - Andreas Phanopoulos
- Department of ChemistryImperial College LondonMolecular Sciences Research HubLondonW12 OBZUK
| | - Antoine Buchard
- Department of ChemistryInstitute for SustainabilityUniversity of BathBathBA2 7AYUK
| | - Charlotte K. Williams
- Department ChemistryUniversity of OxfordChemistry Research Laboratory12 Mansfield RoadOxfordOX1 3TAUK
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10
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Quiroz M, Lockart MM, Xue S, Jones D, Guo Y, Pierce BS, Dunbar KR, Hall MB, Darensbourg MY. Magnetic coupling between Fe(NO) spin probe ligands through diamagnetic Ni II, Pd II and Pt II tetrathiolate bridges. Chem Sci 2023; 14:9167-9174. [PMID: 37655023 PMCID: PMC10466285 DOI: 10.1039/d3sc01546g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 08/07/2023] [Indexed: 09/02/2023] Open
Abstract
Reaction of the nitrosylated-iron metallodithiolate ligand, paramagnetic (NO)Fe(N2S2), with [M(CH3CN)n][BF4]2 salts (M = NiII, PdII, and PtII; n = 4 or 6) affords di-radical tri-metallic complexes in a stairstep type arrangement ([FeMFe]2+, M = Ni, Pd, and Pt), with the central group 10 metal held in a MS4 square plane. These isostructural compounds have nearly identical ν(NO) stretching values, isomer shifts, and electrochemical properties, but vary in their magnetic properties. Despite the intramolecular Fe⋯Fe distances of ca. 6 Å, antiferromagnetic coupling is observed between {Fe(NO)}7 units as established by magnetic susceptibility, EPR, and DFT studies. The superexchange interaction through the thiolate sulfur and central metal atoms is on the order of NiII < PdII ≪ PtII with exchange coupling constants (J) of -3, -23, and -124 cm-1, consistent with increased covalency of the M-S bonds (3d < 4d < 5d). This trend is reproduced by DFT calculations with molecular orbital analysis providing insight into the origin of the enhancement in the exchange interaction. Specifically, the magnitude of the exchange interaction correlates surprisingly well with the energy difference between the HOMO and HOMO-1 orbitals of the triplet states, which is reflected in the central metal's contribution to these orbitals. These results demonstrate the ability of sulfur-dense metallodithiolate ligands to engender strong magnetic communication by virtue of their enhanced covalency and polarizability.
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Affiliation(s)
- Manuel Quiroz
- Department of Chemistry, Texas A &M University College Station Texas 77843 USA
| | - Molly M Lockart
- Department of Chemistry & Biochemistry, Samford University Birmingham Alabama 35229 USA
| | - Shan Xue
- Department of Chemistry, Carnegie Mellon University Pittsburgh Pennsylvania 15213 USA
| | - Dakota Jones
- Department of Chemistry, Texas A &M University College Station Texas 77843 USA
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University Pittsburgh Pennsylvania 15213 USA
| | - Brad S Pierce
- Department of Chemistry & Biochemistry, University of Alabama Tuscaloosa Alabama 35487 USA
| | - Kim R Dunbar
- Department of Chemistry, Texas A &M University College Station Texas 77843 USA
| | - Michael B Hall
- Department of Chemistry, Texas A &M University College Station Texas 77843 USA
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11
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Fiorentini F, Diment WT, Deacy AC, Kerr RWF, Faulkner S, Williams CK. Understanding catalytic synergy in dinuclear polymerization catalysts for sustainable polymers. Nat Commun 2023; 14:4783. [PMID: 37553344 PMCID: PMC10409799 DOI: 10.1038/s41467-023-40284-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 07/20/2023] [Indexed: 08/10/2023] Open
Abstract
Understanding the chemistry underpinning intermetallic synergy and the discovery of generally applicable structure-performances relationships are major challenges in catalysis. Additionally, high-performance catalysts using earth-abundant, non-toxic and inexpensive elements must be prioritised. Here, a series of heterodinuclear catalysts of the form Co(III)M(I/II), where M(I/II) = Na(I), K(I), Ca(II), Sr(II), Ba(II) are evaluated for three different polymerizations, by assessment of rate constants, turn over frequencies, polymer selectivity and control. This allows for comparisons of performances both within and between catalysts containing Group I and II metals for CO2/propene oxide ring-opening copolymerization (ROCOP), propene oxide/phthalic anhydride ROCOP and lactide ring-opening polymerization (ROP). The data reveal new structure-performance correlations that apply across all the different polymerizations: catalysts featuring s-block metals of lower Lewis acidity show higher rates and selectivity. The epoxide/heterocumulene ROCOPs both show exponential activity increases (vs. Lewis acidity, measured by the pKa of [M(OH2)m]n+), whilst the lactide ROP activity and CO2/epoxide selectivity show linear increases. Such clear structure-activity/selectivity correlations are very unusual, yet are fully rationalised by the polymerization mechanisms and the chemistry of the catalytic intermediates. The general applicability across three different polymerizations is significant for future exploitation of catalytic synergy and provides a framework to improve other catalysts.
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Affiliation(s)
| | - Wilfred T Diment
- Department of Chemistry, University of Oxford, OX1 3TA, Oxford, United Kingdom
| | - Arron C Deacy
- Department of Chemistry, University of Oxford, OX1 3TA, Oxford, United Kingdom
| | - Ryan W F Kerr
- Department of Chemistry, University of Oxford, OX1 3TA, Oxford, United Kingdom
| | - Stephen Faulkner
- Department of Chemistry, University of Oxford, OX1 3TA, Oxford, United Kingdom
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12
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Nguyen HM, Morgan HWT, Chantarojsiri T, Kerr TA, Yang JY, Alexandrova AN, Léonard NG. Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes. J Phys Chem A 2023. [PMID: 37316977 DOI: 10.1021/acs.jpca.3c00827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The incorporation of charged groups proximal to a redox active transition metal center can impact the local electric field, altering redox behavior and enhancing catalysis. Vanadyl salen (salen = N,N'-ethylenebis(salicylideneaminato)) complexes functionalized with a crown ether containing a nonredox active metal cation (V-Na, V-K, V-Ba, V-La, V-Ce, and V-Nd) were synthesized. The electrochemical behavior of this series of complexes was investigated by cyclic voltammetry in solvents with varying polarity and dielectric constant (ε) (acetonitrile, ε = 37.5; N,N-dimethylformamide, ε = 36.7; and dichloromethane, ε = 8.93). The vanadium(V/IV) reduction potential shifted anodically with increasing cation charge compared to a complex lacking a proximal cation (ΔE1/2 > 900 mV in acetonitrile and >700 mV in dichloromethane). In contrast, the reduction potential for all vanadyl salen-crown complexes measured in N,N-dimethylformamide was insensitive to the magnitude of the cationic charge, regardless of the electrolyte or counteranion used. Titration studies of N,N-dimethylformamide into acetonitrile resulted in cathodic shifting of the vanadium(V/IV) reduction potential with increasing concentration of N,N-dimethylformamide. Binding constants of N,N-dimethylformamide (log(KDMF)) for the series of crown complexes show increased binding affinity in the order of V-La > V-Ba > V-K > (salen)V(O), indicating an enhancement of Lewis acid/base interaction with increasing cationic charge. The redox behavior of (salen)V(O) and (salen-OMe)V(O) (salen-OMe = N,N'-ethylenebis(3-methoxysalicylideneamine) was also investigated and compared to the crown-containing complexes. For (salen-OMe)V(O), a weak association of triflate salt at the vanadium(IV) oxidation state was observed through cyclic voltammetry titration experiments, and cation dissociation upon oxidation to vanadium(V) was identified. These studies demonstrate the noninnocent role of solvent coordination and cation/anion effects on redox behavior and, by extension, the local electric field.
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Affiliation(s)
- Hien M Nguyen
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States
| | - Harry W T Morgan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Teera Chantarojsiri
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand
| | - Tyler A Kerr
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States
| | - Jenny Y Yang
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States
| | - Anastassia N Alexandrova
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Nadia G Léonard
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States
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13
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Dopp CM, Golwankar RR, Kelsey SR, Douglas JT, Erickson AN, Oliver AG, Day CS, Day VW, Blakemore JD. Vanadyl as a Spectroscopic Probe of Tunable Ligand Donor Strength in Bimetallic Complexes. Inorg Chem 2023. [PMID: 37315176 DOI: 10.1021/acs.inorgchem.3c00724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Incorporation of secondary metal ions into heterobimetallic complexes has emerged as an attractive strategy for rational tuning of compounds' properties and reactivity, but direct solution-phase spectroscopic interrogation of tuning effects has received less attention than it deserves. Here, we report the assembly and study of a series of heterobimetallic complexes containing the vanadyl ion, [VO]2+, paired with monovalent cations (Cs+, Rb+, K+, Na+, and Li+) and a divalent cation (Ca2+). These complexes, which can be isolated in pure form or generated in situ from a common monometallic vanadyl-containing precursor, enable experimental spectroscopic and electrochemical quantification of the influence of the incorporated cations on the properties of the vanadyl moiety. The data reveal systematic shifts in the V-O stretching frequency, isotropic hyperfine coupling constant for the vanadium center, and V(V)/V(IV) reduction potential in the complexes. These shifts can be interpreted as charge density effects parametrized through the Lewis acidities of the cations, suggesting broad potential for the vanadyl ion to serve as a spectroscopic probe in multimetallic species.
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Affiliation(s)
- Claire M Dopp
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Riddhi R Golwankar
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Shaun R Kelsey
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Justin T Douglas
- Nuclear Magnetic Resonance Laboratory, Molecular Structures Group, University of Kansas, 2034 Becker Dr, Lawrence, Kansas 66047, United States
| | - Alexander N Erickson
- Department of Chemistry, University of Memphis, 3744 Walker Avenue, Memphis, Tennessee 38152, United States
| | - Allen G Oliver
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Cynthia S Day
- Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109, United States
| | - Victor W Day
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - James D Blakemore
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
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14
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Sundararajan M. Redox Potentials of Uranyl Ions in Macrocyclic Complexes: Quantifying the Role of Counter-Ions. ACS OMEGA 2023; 8:18041-18046. [PMID: 37251172 PMCID: PMC10210231 DOI: 10.1021/acsomega.3c01244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 04/27/2023] [Indexed: 05/31/2023]
Abstract
Several uranyl ions strapped with Schiff-base ligands in the presence of redox-innocent metal ions are synthesized, and their reduction potentials are recently estimated. The change in Lewis acidity of the redox-innocent metal ions contributes to ∼60 mV/pKa unit quantified which is intriguing. Upon increasing the Lewis acidity of metal ions, the number of triflate molecules found near the metal ions also increases whose contributions toward the redox potentials remain poorly understood and not quantified until now. Most importantly, to ease the computational burden, triflate anions are often neglected in quantum chemical models due to their larger size and weak coordination to metal ions. Herein, we have quantified and dissected the individual contributions that arise alone from Lewis acid metal ions and from triflate anions with electronic structure calculations. The triflate anion contributions are large, in particular, for divalent and trivalent anions that cannot be neglected. It was presumed to be innocent, but we here show that they can contribute more than 50% to the predicted redox potentials, suggesting that their vital role in the overall reduction processes cannot be neglected.
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15
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Maitra A, Das P, Thompson BC, Dawlaty JM. Distinguishing between the Electrostatic Effects and Explicit Ion Interactions in a Stark Probe. J Phys Chem B 2023; 127:2511-2520. [PMID: 36917012 DOI: 10.1021/acs.jpcb.2c08030] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/15/2023]
Abstract
Vibrational Stark probes are incisive tools for measuring local electric fields in a wide range of chemical environments. The interpretation of the frequency shift often gets complicated due to the specific interactions of the probe, such as hydrogen bonding and Lewis bonding. Therefore, it is important to distinguish between the pure electrostatic response and the response due to such specific interactions. Here we report a molecular system that is sensitive to both the Stark effect from a single ion and the explicit Lewis bonding of ions with the probe. The molecule consists of a crown ether with an appended benzonitrile. The crown captures cations of various charges, and the electric field from the ions is sensed by the benzonitrile probe. Additionally, the lone pair of the benzonitrile can engage in Lewis interactions with some of the ions by donating partial charge density to the ions. Our system exhibits both of these effects and therefore is a suitable test bed for distinguishing between the pure electrostatic and the Lewis interactions. Our computational results show that the electrostatic influence of the ion is operative at large distances, while the Lewis interaction becomes important only within distances that permit orbital overlap. Our results may be useful for using the nitrile probe for measuring electrostatic and coordination effects in complex ionic environments such as the electrode-electrolyte interfaces.
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Affiliation(s)
- Anwesha Maitra
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Pratyusha Das
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Barry C Thompson
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Jahan M Dawlaty
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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16
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Golwankar RR, Curry TD, Paranjothi CJ, Blakemore JD. Molecular Influences on the Quantification of Lewis Acidity with Phosphine Oxide Probes. Inorg Chem 2023. [PMID: 36943934 DOI: 10.1021/acs.inorgchem.3c00084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023]
Abstract
Gutmann-Beckett-type measurements with phosphine oxide probes can be used to estimate effective Lewis acidity with 31P nuclear magnetic resonance spectroscopy, but the influence of the molecular structure of a given probe on the quantification of Lewis acidity remains poorly documented in experimental work. Here, a quantitative comparison of triethyl (E), trioctyl (O), and triphenyl (P) phosphine oxides as molecular probes of Lewis acidity has been carried out via titration studies in MeCN with a test set of six mono- and divalent metal triflate salts. In comparison to E, the bulkier O displays a similar range of chemical shift values and binding affinities for the various test metal ions. Spectral linewidths and speciation properties vary for individual cation-to-probe ratios, however, confirming probe-specific properties that can impact the data quality. Importantly, P displays a consistently narrower dynamic range than both E and O, illustrating how electronic changes at phosphorus can influence the NMR response. Comparative parametrizations of the effective Lewis acidities of a broader range of metal ions, including the trivalent rare earth ions Y3+, Lu3+, and Sc3+ as well as the uranyl ion (UO22+), can be understood in light of these results, providing insight into the fundamental chemical processes underlying the useful approach of single-point measurements for quantification of effective Lewis acidity. Together with a study of counteranion effects reported here, these data clarify the diverse ensemble of factors that can influence the measurement of Lewis acid/base interactions.
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Affiliation(s)
- Riddhi R Golwankar
- Department of Chemistry, University of Kansas, 1845 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - T Davis Curry
- Department of Chemistry, University of Kansas, 1845 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Cecilia J Paranjothi
- Department of Chemistry, University of Kansas, 1845 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - James D Blakemore
- Department of Chemistry, University of Kansas, 1845 Irving Hill Road, Lawrence, Kansas 66045, United States
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17
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Bhunia P, Gomila RM, Frontera A, Ghosh A. Combined effects of the lewis acidity and electric field of proximal redox innocent metal ions on the redox potential of vanadyl Schiff base complexes: an experimental and theoretical study. Dalton Trans 2023; 52:3097-3110. [PMID: 36786744 DOI: 10.1039/d3dt00024a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The reactivity of biological or synthetic metalloenzymes is modulated in the presence of redox innocent Lewis acidic metal ions as they change the redox potential of the redox active metal ions present in the active site of metalloenzymes. To study this effect, we synthesised a mono-nuclear V(IV) complex (VOL, 1) with an N2O4 donor bicompartmental ligand, characterized it by single-crystal X-ray crystallography and recorded its cyclic voltammogram in acetonitrile. The CV revealed a reversible redox process for the V(IV)/V(V) couple. The potential of the V(IV)/V(V) couple shifted to a more positive value when equivalent amounts of Li+, Na+, K+, Mg2+, Ca2+ and Ba2+ ions were added separately to its acetonitrile solution, but the extent of shift for Li+ and Mg2+ was much less than that of the other metal ions. The guest metal ions except Li+ and Mg2+ were accommodated in the outer compartment of VOL as confirmed by IR and UV-Vis spectral analysis. Single-crystal structural analysis of [(VOL)KPF6]2, (1·K) and [(VOL)Ba(ClO4)2(H2O)]n, (1·Ba) also confirmed the hetero-metallic adduct formation. The correlation of the shift of the V(IV/V) redox potential with the Lewis acidity of respective metal ions deviated appreciably from linearity. DFT calculations suggest that the shift in potential is probably controlled by local electric fields induced by those ions, as indicated by 2D vector electric field maps.
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Affiliation(s)
- Pradip Bhunia
- Department of Chemistry, University College of Science, University of Calcutta, 92, A.P.C. Road, Kolkata-700 009, India.
| | - Rosa M Gomila
- Departament de Química, Universitat de les Illes Balears, Crta. de Valldemossa km 7.5, 07122 Palma de Mallorca, Baleares, Spain.
| | - Antonio Frontera
- Departament de Química, Universitat de les Illes Balears, Crta. de Valldemossa km 7.5, 07122 Palma de Mallorca, Baleares, Spain.
| | - Ashutosh Ghosh
- Department of Chemistry, University College of Science, University of Calcutta, 92, A.P.C. Road, Kolkata-700 009, India. .,Rani Rashmoni Green University, Tarakeswar, Hooghly 712410, West Bengal, India
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18
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Pattanayak S, Loewen ND, Berben LA. Using Substituted [Fe 4N(CO) 12] - as a Platform To Probe the Effect of Cation and Lewis Acid Location on Redox Potential. Inorg Chem 2023; 62:1919-1925. [PMID: 36006454 DOI: 10.1021/acs.inorgchem.2c01556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The impact of cationic and Lewis acidic functional groups installed in the primary or secondary coordination sphere (PCS or SCS) of an (electro)catalyst is known to vary depending on the precise positioning of those groups. However, it is difficult to systematically probe the effect of that position. In this report, we probe the effect of the functional group position and identity on the observed reduction potentials (Ep,c) using substituted iron clusters, [Fe4N(CO)11R]n, where R = NO+, PPh2-CH2CH2-9BBN, (MePTA+)2, (MePTA+)4, and H+ and n = 0, -1, +1, or +3 (9-BBN is 9-borabicyclo(3.3.1)nonane; MePTA+ is 1-methyl-1-azonia-3,5-diaza-7-phosphaadamantane). The cationic NO+ and H+ ligands cause anodic shifts of 700 and 320 mV, respectively, in Ep,c relative to unsubstituted [Fe4N(CO)12]-. Infrared absorption band data, νCO, suggests that some of the 700 mV shift by NO+ results from electronic changes to the cluster core. This contrasts with the effects of cationic MePTA+ and H+ which cause primarily electrostatic effects on Ep,c. Lewis acidic 9-BBN in the SCS had almost no effect on Ep,c.
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Affiliation(s)
- Santanu Pattanayak
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Natalia D Loewen
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Louise A Berben
- Department of Chemistry, University of California, Davis, California 95616, United States
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19
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Hanaway D, Kennedy CR. Automated Variable Electric-Field DFT Application for Evaluation of Optimally Oriented Electric Fields on Chemical Reactivity. J Org Chem 2023; 88:106-115. [PMID: 36507909 PMCID: PMC9830642 DOI: 10.1021/acs.joc.2c01893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent theoretical work and experiments at molecular junctions have provided a strong conceptualization for the effects of oriented electric fields (OEFs) on organic reactions. Depending on the axis of application, OEFs can increase (or decrease) the reaction rate or distinguish between isomeric pathways. Despite the conceptual elegance of OEFs, which may be applied externally or induced locally, as tools for catalyzing organic reactions, implementation in synthetically relevant systems has been hampered by inefficiencies in evaluating reaction sensitivity to field effects. Herein, we describe the development of the Automated Variable Electric-Field DFT Application (A.V.E.D.A.) for streamlined evaluation of a reaction's susceptibility to OEFs. This open-source software was designed to be accessible for nonexpert users of computational and programming tools. Following initiation by a single command (and with no subsequent intervention) the Linux workflow manages a series of density functional theory calculations and mathematical manipulations to optimize local-minimum and transition-state structures in oriented electric fields of increasing magnitude. The resulting molecular and reaction dipole moments, field-perturbed geometries, and net effective activation energies are compiled for user interpretation. Ten representative pericyclic reactions that showcase the development and evaluation of A.V.E.D.A. are described.
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20
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Jiang T, Tian LC, Huang C, Zhu BX, Chen DM, Zhu C. A new fluorescent chemosensor based on 2,2’-bipyridyl acylhydrazone Schiff base: Synthesis, sensing properties, and coordination behaviors. Inorganica Chim Acta 2022. [DOI: 10.1016/j.ica.2022.121367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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21
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Keshtkar N, Zamanpour A, Esmaielzadeh S. Bioactive Ni(II), Cu(II) and Zn(II) complexes with an N3 functionalized Schiff base ligand: Synthesis, structural elucidation, thermodynamic and DFT calculation studies. Inorganica Chim Acta 2022. [DOI: 10.1016/j.ica.2022.121083] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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22
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Kaur S, Bera M, Santra A, Munshi S, Sterbinsky GE, Wu T, Moonshiram D, Paria S. Effect of Redox-Inactive Metal Ion-Nickel(III) Interactions on the Redox Properties and Proton-Coupled Electron Transfer Reactivity. Inorg Chem 2022; 61:14252-14266. [PMID: 36041064 DOI: 10.1021/acs.inorgchem.2c01472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mononuclear nickel(II) and nickel(III) complexes of a bisamidate-bisalkoxide ligand, (NMe4)2[NiII(HMPAB)] (1) and (NMe4)[NiIII(HMPAB)] (2), respectively, have been synthesized and characterized by various spectroscopic techniques including X-ray crystallography. The reaction of redox-inactive metal ions (Mn+ = Ca2+, Mg2+, Zn2+, Y3+, and Sc3+) with 2 resulted in 2-Mn+ adducts, which was assessed by an array of spectroscopic techniques including X-ray absorption spectroscopy (XAS), electron paramagnetic resonance (EPR), and reactivity studies. The X-ray structure of Ca2+ coordinated to Ni(III) complexes, 2-Ca2+T, was determined and exhibited an average Ni-Ca distance of 3.1253 Å, close to the metal ions' covalent radius. XAS analysis of 2-Ca2+ and 2-Y3+ in solution further revealed an additional coordination to Ca and Y in the 2-Mn+ adducts with shortened Ni-M distances of 2.15 and 2.11 Å, respectively, implying direct bonding interactions between Ni and Lewis acids (LAs). Such a short interatomic distance between Ni(III) and M is unprecedented and was not observed before. EPR analysis of 2 and 2-Mn+ species, moreover, displayed rhombic signals with gav > 2.12 for all complexes, supporting the +III oxidation state of Ni. The NiIII/NiII redox potential of 2 and 2-Mn+ species was determined, and a plot of E1/2 of 2-Mn+ versus pKa of [M(H2O)n]m+ exhibited a linear relationship, implying that the NiIII/NiII potential of 2 can be tuned with different redox-inactive metal ions. Reactivity studies of 2 and 2-Mn+ with different 4-X-2,6-ditert-butylphenol (4-X-DTBP) and other phenol derivatives were performed, and based on kinetic studies, we propose the involvement of a proton-coupled electron transfer (PCET) pathway. Analysis of the reaction products after the reaction of 2 with 4-OMe-DTBP showed the formation of a Ni(II) complex (1a) where one of the alkoxide arms of the ligand is protonated. A pKa value of 24.2 was estimated for 1a. The reaction of 2-Mn+ species was examined with 4-OMe-DTBP, and it was observed that the k2 values of 2-Mn+ species increase by increasing the Lewis acidity of redox-inactive metal ions. However, the obtained k2 values for 2-Mn+ species are much lower compared to the k2 value for 2. Such a variation of PCET reactivity between 2 and 2-Mn+ species may be attributed to the interactions between Ni(III) and LAs. Our findings show the significance of the secondary coordination sphere effect on the PCET reactivity of Ni(III) complexes and furnish important insights into the reaction mechanism involving high-valent nickel species, which are frequently invoked as key intermediates in Ni-mediated enzymatic reactions, solar-fuel catalysis, and biomimetic/synthetic transformation reactions.
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Affiliation(s)
- Simarjeet Kaur
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Moumita Bera
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Aakash Santra
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Sandip Munshi
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - George E Sterbinsky
- X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Tianpin Wu
- X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Dooshaye Moonshiram
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, Madrid 28049, Spain
| | - Sayantan Paria
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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23
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Teptarakulkarn P, Lorpaiboon W, Anusanti T, Laowiwatkasem N, Chainok K, Sangtrirutnugul P, Surawatanawong P, Chantarojsiri T. Incorporation of Cation Affects the Redox Reactivity of Fe- NNN Complexes on C-H Oxidation. Inorg Chem 2022; 61:11066-11074. [PMID: 35815773 DOI: 10.1021/acs.inorgchem.2c00762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cations such as Lewis acids have been shown to enhance the catalytic activity of high-valent Fe-oxygen intermediates. Herein, we present a pyridine diamine ethylene glycol macrocycle, which can form Zn(II)- or Fe(III)-complex with the NNN site, while allowing redox-inactive cations to bind to the ethylene glycol moiety. The addition of alkali, alkali earth, and lanthanum ions resulted in positive shifts to the Fe(III/II) redox potential. Calculation of dissociation constants showed the tightest binding with a Ba2+ ion. Density functional theory calculations were used to elucidate the effects of redox inactive cations toward the electronic structures of Fe complexes. Although the Fe-NNN complexes, both in the absence and presence of cations, can catalyze C-H oxidation of 9,10-dihydroanthracene, to give anthracene [hydrogen atom transfer (HAT) product], anthrone, and anthraquinone [oxygen atom transfer (OAT) products], highest overall activity and OAT/HAT product ratios were obtained in the presence of dications, that is, Ba2+ and Mg2+, respectively.
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Affiliation(s)
- Pathorn Teptarakulkarn
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Wanutcha Lorpaiboon
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Thana Anusanti
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Natchapol Laowiwatkasem
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Kittipong Chainok
- Thammasat University Research Unit in Multifunctional Crystalline Materials and Applications (TU-MCMA), Faculty of Science and Technology, Thammasat University, Pathum Thani 12121, Thailand
| | - Preeyanuch Sangtrirutnugul
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Panida Surawatanawong
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Teera Chantarojsiri
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
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24
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Golwankar RR, Kumar A, Day VW, Blakemore JD. Revealing the Influence of Diverse Secondary Metal Cations on Redox‐Active Palladium Complexes. Chemistry 2022; 28:e202200344. [DOI: 10.1002/chem.202200344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Indexed: 11/09/2022]
Affiliation(s)
- Riddhi R. Golwankar
- Department of Chemistry University of Kansas 1567 Irving Hill Road Lawrence Kansas 66045 USA
| | - Amit Kumar
- Department of Chemistry University of Kansas 1567 Irving Hill Road Lawrence Kansas 66045 USA
- Current address: Department of Chemistry University of Pennsylvania Philadelphia Pennsylvania 19104 USA
| | - Victor W. Day
- Department of Chemistry University of Kansas 1567 Irving Hill Road Lawrence Kansas 66045 USA
| | - James D. Blakemore
- Department of Chemistry University of Kansas 1567 Irving Hill Road Lawrence Kansas 66045 USA
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25
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Weberg AB, Murphy RP, Tomson NC. Oriented internal electrostatic fields: an emerging design element in coordination chemistry and catalysis. Chem Sci 2022; 13:5432-5446. [PMID: 35694353 PMCID: PMC9116365 DOI: 10.1039/d2sc01715f] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 04/19/2022] [Indexed: 11/21/2022] Open
Abstract
The power of oriented electrostatic fields (ESFs) to influence chemical bonding and reactivity is a phenomenon of rapidly growing interest. The presence of strong ESFs has recently been implicated as one of the most significant contributors to the activity of select enzymes, wherein alignment of a substrate's changing dipole moment with a strong, local electrostatic field has been shown to be responsible for the majority of the enzymatic rate enhancement. Outside of enzymology, researchers have studied the impacts of "internal" electrostatic fields via the addition of ionic salts to reactions and the incorporation of charged functional groups into organic molecules (both experimentally and computationally), and "externally" via the implementation of bulk fields between electrode plates. Incorporation of charged moieties into homogeneous inorganic complexes to generate internal ESFs represents an area of high potential for novel catalyst design. This field has only begun to materialize within the past 10 years but could be an area of significant impact moving forward, since it provides a means for tuning the properties of molecular complexes via a method that is orthogonal to traditional strategies, thereby providing possibilities for improved catalytic conditions and novel reactivity. In this perspective, we highlight recent developments in this area and offer insights, obtained from our own research, on the challenges and future directions of this emerging field of research.
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Affiliation(s)
- Alexander B Weberg
- R, oy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 S. 34th Street Philadelphia Pennsylvania 19104 USA
| | - Ryan P Murphy
- R, oy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 S. 34th Street Philadelphia Pennsylvania 19104 USA
| | - Neil C Tomson
- R, oy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 S. 34th Street Philadelphia Pennsylvania 19104 USA
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26
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Ghosh TK, Maity S, Ghosh S, Gomila RM, Frontera A, Ghosh A. Role of Redox-Inactive Metal Ions in Modulating the Reduction Potential of Uranyl Schiff Base Complexes: Detailed Experimental and Theoretical Studies. Inorg Chem 2022; 61:7130-7142. [PMID: 35467851 DOI: 10.1021/acs.inorgchem.2c00645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A mononuclear uranyl complex, [UO2L] (1), has been synthesized with the ligand N,N'-bis(3-methoxy-2-hydroxybenzylidene)-1,6-diamino-3-azahexane (H2L). The complex showed a reversible U(VI)/U(V) redox couple in cyclic voltammetric measurements. The reduction potential of this couple showed a positive shift upon the addition of redox-inactive alkali- and alkaline-earth Lewis acidic metal ions (Li+, Na+, K+, Ca2+, Sr2+, and Ba2+) to an acetonitrile solution of complex 1. The positive shift of the reduction potential has been explained on the basis of the Lewis acidity and internal electric-field effect of the respective metal ions. The bimetallic complexes [UO2LLi(NO3)] (2), [UO2LNa(BF4)]2 (3), [UO2LK(PF6)]2 (4), [(UO2L)2Ca]·(ClO4)2·CH3CN (5), [(UO2L)2Sr(H2O)2]·(ClO4)2·CH3CN (6), and [(UO2L)2Ba(ClO4)]·(ClO4) (7) have also been isolated in the solid state by reacting complex 1 with the corresponding metal ions and characterized by single-crystal X-ray diffraction. Density functional theory calculations of the optimized [UO2LM]n+ complexes have been used to rationalize the experimental reduction and electric-field potentials imposed by the non-redox-active cations.
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Affiliation(s)
- Tanmoy Kumar Ghosh
- Department of Chemistry, University College of Science, University of Calcutta, 92 APC Road, Kolkata 700009, India
| | - Souvik Maity
- Department of Chemistry, University College of Science, University of Calcutta, 92 APC Road, Kolkata 700009, India
| | - Soumavo Ghosh
- Department of Chemistry, University College of Science, University of Calcutta, 92 APC Road, Kolkata 700009, India
| | - Rosa M Gomila
- Departament de Química, Universitat de les Illes Balears, Carta de Valldemossa km 7.5, 07122 Palma de Mallorca, Baleares, Spain
| | - Antonio Frontera
- Departament de Química, Universitat de les Illes Balears, Carta de Valldemossa km 7.5, 07122 Palma de Mallorca, Baleares, Spain
| | - Ashutosh Ghosh
- Department of Chemistry, University College of Science, University of Calcutta, 92 APC Road, Kolkata 700009, India.,Rani Rashmoni Green University, Tarakeswar, Hooghly 712410, West Bengal, India
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27
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Kelty ML, McNeece AJ, Kurutz JW, Filatov AS, Anderson JS. Electrostatic vs. inductive effects in phosphine ligand donor properties and reactivity. Chem Sci 2022; 13:4377-4387. [PMID: 35509471 PMCID: PMC9007067 DOI: 10.1039/d1sc04277g] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 03/15/2022] [Indexed: 11/21/2022] Open
Abstract
Enhanced rates and selectivity in enzymes are enabled in part by precisely tuned electric fields within active sites. Analogously, the use of charged groups to leverage electrostatics in molecular systems is a promising strategy to tune reactivity. However, separation of the through space and through bond effects of charged functional groups is a long standing challenge that limits the rational application of electric fields in molecular systems. To address this challenge we developed a method using the phosphorus selenium coupling value (J P-Se) of anionic phosphine selenides to quantify the electrostatic contribution of the borate moiety to donor strength. In this analysis we report the synthesis of a novel anionic phosphine, PPh2CH2BF3K, the corresponding tetraphenyl phosphonium and tetraethyl ammonium selenides [PPh4][SePPh2CH2BF3] and [TEA][SePPh2CH2BF3], and the Rh carbonyl complex [PPh4][Rh(acac)(CO)(PPh2(CH2BF3))]. Solvent-dependent changes in J P-Se were fit using Coulomb's law and support up to an 80% electrostatic contribution to the increase in donor strength of [PPh4][SePPh2CH2BF3] relative to SePPh2Et, while controls with [TEA][SePPh2CH2BF3] exclude convoluting ion pairing effects. Calculations using explicit solvation or point charges effectively replicate the experimental data. This J P-Se method was extended to [PPh4][SePPh2(2-BF3Ph)] and likewise estimates up to a 70% electrostatic contribution to the increase in donor strength relative to SePPh3. The use of PPh2CH2BF3K also accelerates C-F oxidative addition reactivity with Ni(COD)2 by an order of magnitude in comparison to the comparatively donating neutral phosphines PEt3 and PCy3. This enhanced reactivity prompted the investigation of catalytic fluoroarene C-F borylation, with improved yields observed for less fluorinated arenes. These results demonstrate that covalently bound charged functionalities can exert a significant electrostatic influence under common solution phase reaction conditions and experimentally validate theoretical predictions regarding electrostatic effects in reactivity.
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Affiliation(s)
- Margaret L Kelty
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
| | - Andrew J McNeece
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
| | - Josh W Kurutz
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
| | - Alexander S Filatov
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
| | - John S Anderson
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
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28
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Nie W, McCrory C. Strategies for Breaking Molecular Scaling Relationships for the Electrochemical CO 2 Reduction Reaction. Dalton Trans 2022; 51:6993-7010. [DOI: 10.1039/d2dt00333c] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electrocatalytic CO2 reduction reaction (CO2RR) is a promising strategy for converting CO2 to fuels and value-added chemicals using renewable energy sources. Molecular electrocatalysts show promise for the selective conversion...
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Deng YH, Yan YJ, Zhang J, Na LP, Zhang Y, Dong WK. Exploitation of a Half-Conjugate Polydentate Salamo-Salen Hybrid Ligand and Its Two Phenoxide-Bridged Heterohexanuclear 3d-s Double-Helical Cluster Complexes. Inorg Chem 2021; 61:1018-1030. [PMID: 34967616 DOI: 10.1021/acs.inorgchem.1c03066] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A half-conjugate polydentate Salamo-Salen hybrid ligand, H5L, containing two unique N2O2 pockets was first designed so that these metal ions in the complexes appear in different coordination modes. Two heterohexanuclear 3d-s double-helical cluster complexes, [Zn4Ca2L2(μ1-OAc)2(EtOH)2]·2EtOH (1; EtOH = ethanol) and [Zn4Sr2L2(μ2-OAc)2(MeOH)2]·2CH2Cl2 (2; MeOH = methanol), are reported that are formed through the reaction of H5L with zinc(II) and calcium(II) acetate or strontium(II) acetate, respectively. IR spectral analysis of the two complexes showed the existence of monodentate- and bidentate-coordinated acetate ions. The fluorescence properties of the ligand and its two heterohexanuclear complexes were explored in MeOH and water solutions, separately. In addition, theoretical calculations (density functional theory, interaction region indicator, and bond order) were performed to further understand the formation of a single-molecular double helix and the electron distribution characteristics of the two complexes.
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Affiliation(s)
- Yun-Hu Deng
- School of Chemistry and Chemical Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu 730070, China
| | - Yuan-Ji Yan
- School of Chemistry and Chemical Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu 730070, China
| | - Jian Zhang
- School of Chemistry and Chemical Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu 730070, China
| | - Li-Ping Na
- School of Chemistry and Chemical Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu 730070, China
| | - Yang Zhang
- School of Chemistry and Chemical Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu 730070, China
| | - Wen-Kui Dong
- School of Chemistry and Chemical Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu 730070, China
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30
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Gupta G, Bera M, Paul S, Paria S. Electrochemical Properties and Reactivity Study of [Mn V(O)(μ-OR-Lewis Acid)] Cores. Inorg Chem 2021; 60:18006-18016. [PMID: 34813300 DOI: 10.1021/acs.inorgchem.1c02601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A mononuclear manganese(V) oxo complex of a bis(amidate)bis(alkoxide) ligand, (NMe4)[MnV(HMPAB)(O)] [2; H4HMPAB = 1,2-bis(2-hydroxy-2-methylpropanamido)benzene], was synthesized and structurally characterized. A Mn-Oterm distance of 1.566(4) Å was observed in the solid-state structure of 2, consistent with the Mn≡O formulation. The reaction of redox-inactive metal ions (Mn+ = Li+, Ca2+, Mg2+, Y3+, and Sc3+) with 2 resulted in the formation of 2-Mn+ species, which were characterized by UV-vis, 1H NMR, cyclic voltammetry, and in situ IR spectroscopy. Theoretical calculations suggested that the alkoxide oxygen atoms of the ligand scaffold are energetically most favorable for coordinating the Mn+ ions in 2. Complex 2 revealed one-electron-reduction potential at -0.01 V versus ferrocenium/ferrocene, which shifted anodically upon coordination of Mn+ ions to 2, and such a shift became more prominent with stronger Lewis acids. The oxygen-atom transfer (OAT) reactivities of 2 and 2-Mn+ species with triphenylphosphine were compared, which exhibited a systematic increase of the reaction rate with increasing Lewis acidity of Mn+ ions, and a plot of log k2 versus Lewis acidity of Mn+ ions (ΔE) followed a linear relationship. It was observed that 2-Sc3+ was ca. 3200 times more reactive toward the OAT reaction compared to 2. Hammett analysis of 2 exhibited a V-shaped plot, indicating a change of the reaction mechanism upon going from electron-rich to electron-deficient Ar3P substrates. In contrast, 2-Ca2+ and 2-Sc3+ showed an electrophilic nature toward the OAT reaction, thus demonstrating the role of the Lewis acid in controlling the OAT mechanism. The hydrogen-atom abstraction reaction of 2 and 2-Mn+ adducts with 1-benzyl-1,4-dihydronicotinamide was investigated, and it was observed that the rate of reaction did not vary considerably with the Lewis acidity of Mn+ ions. On the basis of Eyring analysis of 2 and 2-Mn+ adducts, we hypothesized an entropy-controlled hydrogen-atom-transfer reaction for 2-Sc3+, which is different from the reaction mechanism of 2 and 2-Ca2+.
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Affiliation(s)
- Geetika Gupta
- Department of Chemistry, Indian Institute of Technology (IIT) Delhi, Hauz Khas, New Delhi 110016, India
| | - Moumita Bera
- Department of Chemistry, Indian Institute of Technology (IIT) Delhi, Hauz Khas, New Delhi 110016, India
| | - Satadal Paul
- Department of Chemistry, Bangabasi Morning College, Kolkata 700009, India
| | - Sayantan Paria
- Department of Chemistry, Indian Institute of Technology (IIT) Delhi, Hauz Khas, New Delhi 110016, India
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31
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Synthesis and redox properties of heterobimetallic Re(bpyCrown-M)(CO)3Cl complexes, where M = Na+, K+, Ca2+, and Ba2+. Polyhedron 2021. [DOI: 10.1016/j.poly.2021.115385] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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32
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Saund SS, Siegler MA, Thoi VS. Electrochemical Degradation of a Dicationic Rhenium Complex via Hoffman-Type Elimination. Inorg Chem 2021; 60:13011-13020. [PMID: 34492759 DOI: 10.1021/acs.inorgchem.1c01427] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Electrocatalytic reduction of carbon dioxide (CO2) by transition-metal catalysts is an attractive means for storing renewably sourced electricity in chemical bonds. Metal coordination compounds represent highly tunable platforms ideal for studying the fundamental stepwise transformations of CO2 into its reduced products. However, metal complexes can decompose upon extended electrolysis and form chemically distinct molecular species or, in some cases, catalytically active electrode deposits. Deciphering the degradative pathways is important for understanding the nature of the active catalyst and designing robust metal complexes for small-molecule activation. Herein, we present a new dicationic rhenium bipyridyl complex capable of multielectron ligand-centered reductions electrochemically. Our in-depth experimental and computational study provides mechanistic insight into an unusual reductively induced Hoffman-type elimination. We identify benzylic tertiary ammonium groups as an electrolytically susceptible moiety and propose key intermediates in the degradative pathway. This investigation highlights the complex interplay between the ligand and metal ion and will guide the future design of metal-organic catalysts.
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Affiliation(s)
- Simran S Saund
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Maxime A Siegler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - V Sara Thoi
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States.,Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, United States
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33
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Lindeboom W, Fraser DAX, Durr CB, Williams CK. Heterodinuclear Zn(II), Mg(II) or Co(III) with Na(I) Catalysts for Carbon Dioxide and Cyclohexene Oxide Ring Opening Copolymerizations. Chemistry 2021; 27:12224-12231. [PMID: 34133043 PMCID: PMC8456860 DOI: 10.1002/chem.202101140] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Indexed: 12/16/2022]
Abstract
A series heterodinuclear catalysts, operating without co-catalyst, show good performances for the ring opening copolymerization (ROCOP) of cyclohexene oxide and carbon dioxide. The complexes feature a macrocyclic ligand designed to coordinate metals such as Zn(II), Mg(II) or Co(III), in a Schiff base 'pocket', and Na(I) in a modified crown-ether binding 'pocket'. The 11 new catalysts are used to explore the influences of the metal combinations and ligand backbones over catalytic activity and selectivity. The highest performance catalyst features the Co(III)Na(I) combination, [N,N'-bis(3,3'-triethylene glycol salicylidene)-1,2-ethylenediamino cobalt(III) di(acetate)]sodium (7), and it shows both excellent activity and selectivity at 1 bar carbon dioxide pressure (TOF=1590 h-1 , >99 % polymer selectivity, 1 : 10: 4000, 100 °C), as well as high activity at higher carbon dioxide pressure (TOF=4343 h-1 , 20 bar, 1 : 10 : 25000). Its rate law shows a first order dependence on both catalyst and cyclohexene oxide concentrations and a zeroth order for carbon dioxide pressure, over the range 10-40 bar. These new catalysts eliminate any need for ionic or Lewis base co-catalyst and instead exploit the coordination of earth-abundant and inexpensive Na(I) adjacent to a second metal to deliver efficient catalysis. They highlight the potential for well-designed ancillary ligands and inexpensive Group 1 metals to deliver high performance heterodinuclear catalysts for carbon dioxide copolymerizations and, in future, these catalysts may also show promise in other alternating copolymerization and carbon dioxide utilizations.
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Affiliation(s)
- Wouter Lindeboom
- Department of ChemistryUniversity of OxfordChemistry Research LaboratoryOxfordUK
| | - Duncan A. X. Fraser
- Department of ChemistryUniversity of OxfordChemistry Research LaboratoryOxfordUK
| | - Christopher B. Durr
- Department of ChemistryUniversity of OxfordChemistry Research LaboratoryOxfordUK
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34
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Léonard NG, Dhaoui R, Chantarojsiri T, Yang JY. Electric Fields in Catalysis: From Enzymes to Molecular Catalysts. ACS Catal 2021; 11:10923-10932. [DOI: 10.1021/acscatal.1c02084] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Nadia G. Léonard
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Rakia Dhaoui
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Teera Chantarojsiri
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand
| | - Jenny Y. Yang
- Department of Chemistry, University of California, Irvine, California 92697, United States
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35
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Wesley T, Román-Leshkov Y, Surendranath Y. Spontaneous Electric Fields Play a Key Role in Thermochemical Catalysis at Metal-Liquid Interfaces. ACS CENTRAL SCIENCE 2021; 7:1045-1055. [PMID: 34235265 PMCID: PMC8228591 DOI: 10.1021/acscentsci.1c00293] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Indexed: 05/20/2023]
Abstract
Large oriented electric fields spontaneously arise at all solid-liquid interfaces via the exchange of ions and/or electrons with the solution. Although intrinsic electric fields are known to play an important role in molecular and biological catalysis, the role of spontaneous polarization in heterogeneous thermocatalysis remains unclear because the catalysts employed are typically disconnected from an external circuit, which makes it difficult to monitor or control the degree of electrical polarization of the surface. Here, we address this knowledge gap by developing general methods for wirelessly monitoring and controlling spontaneous electrical polarization at conductive catalysts dispersed in liquid media. By combining electrochemical and spectroscopic measurements, we demonstrate that proton and electron transfer from solution controllably, spontaneously, and wirelessly polarize Pt surfaces during thermochemical catalysis. We employ liquid-phase ethylene hydrogenation on a Pt/C catalyst as a thermochemical probe reaction and observe that the rate of this nonpolar hydrogenation reaction is significantly influenced by spontaneous electric fields generated by both interfacial proton transfer in water and interfacial electron transfer from organometallic redox buffers in a polar aprotic ortho-difluorobenzene solvent. Across these vastly disparate reaction media, we observe quantitatively similar scaling of ethylene hydrogenation rates with the Pt open-circuit electrochemical potential (E OCP). These results isolate the role of interfacial electrostatic effects from medium-specific chemical interactions and establish that spontaneous interfacial electric fields play a critical role in liquid-phase heterogeneous catalysis. Consequently, E OCP-a generally overlooked parameter in heterogeneous catalysis-warrants consideration in mechanistic studies of thermochemical reactions at solid-liquid interfaces, alongside chemical factors such as temperature, reactant activities, and catalyst structure. Indeed, this work establishes the experimental and conceptual foundation for harnessing electric fields to both elucidate surface chemistry and manipulate preparative thermochemical catalysis.
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Affiliation(s)
- Thejas
S. Wesley
- Department
of Chemical Engineering and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Yuriy Román-Leshkov
- Department
of Chemical Engineering and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Yogesh Surendranath
- Department
of Chemical Engineering and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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36
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Barlow JM, Ziller JW, Yang JY. Inhibiting the Hydrogen Evolution Reaction (HER) with Proximal Cations: A Strategy for Promoting Selective Electrocatalytic Reduction. ACS Catal 2021. [DOI: 10.1021/acscatal.1c01527] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Jeffrey M. Barlow
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Joseph W. Ziller
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Jenny Y. Yang
- Department of Chemistry, University of California, Irvine, California 92697, United States
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37
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Choi J, Kim SH, Lee Y. Axial Redox Tuning at a Tetragonal Cobalt Center. Inorg Chem 2021; 60:5647-5659. [PMID: 33788551 DOI: 10.1021/acs.inorgchem.0c03676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Square pyramidal cobalt complexes were prepared to study their multielectron redox properties. To build a stable redox-active cobalt complex, the combination of a tridentate acriPNP (acriPNP- = 4,5-bis(diisopropylphosphino)-2,7,9,9-tetramethyl-9H-acridin-10-ide) ligand with a bidentate ligand, such as 2,2'-bipyridine, 2-(o-phenyl)pyridine, biphenylene, and their analogues, was employed. In a cobalt complex having a tetragonal structure, the dx2-y2 orbital possesses an antibonding character and must remain empty for its structural integrity, while the dz2 orbital acts as a redox-active frontier molecular orbital (FMO). Tuning the redox potential of the Co(II/I) couple was successfully achieved by introducing a different axial donor. The reduction of Co(II) to Co(I) occurs at -2.6 V for a neutral donor but shifts to -3.4 V for an anionic donor. Since the redox-active dz2 orbital is close in energy to other ligand-based orbitals, multielectron redox activity is also observed. Electrochemical measurements indicate three reversible redox events within a window of -3.0-0.0 V vs Fc/Fc+ in tetrahydrofuran (THF). These redox processes are fully reversible for over 100 cycles, reflecting the electrochemical stability of these cobalt complexes. Surprisingly, the oxidation potential of the acriPNP ligand varies dramatically from +0.15 to -2.4 V, which is probably due to the cobalt contribution on the amido-based molecular orbital. The electronic structure of the cobalt complexes was examined structurally, spectroscopically, and theoretically.
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Affiliation(s)
- Jonghoon Choi
- Department of Chemistry, Seoul National University, Seoul 08826, Republic of Korea
| | - Sun Hee Kim
- Western Seoul Center, Korea Basic Science Institute, Seoul 03759, Republic of Korea
| | - Yunho Lee
- Department of Chemistry, Seoul National University, Seoul 08826, Republic of Korea
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38
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Loewen ND, Pattanayak S, Herber R, Fettinger JC, Berben LA. Quantification of the Electrostatic Effect on Redox Potential by Positive Charges in a Catalyst Microenvironment. J Phys Chem Lett 2021; 12:3066-3073. [PMID: 33750139 DOI: 10.1021/acs.jpclett.1c00406] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Charged functional groups in the secondary coordination sphere (SCS) of a heterogeneous nanoparticle or homogeneous electrocatalyst are of growing interest due to enhancements in reactivity that derive from specific interactions that stabilize substrate binding or charged intermediates. At the same time, accurate benchmarking of electrocatalyst systems most often depends on the development of linear free-energy scaling relationships. However, the thermodynamic axis in those kinetic-thermodynamic correlations is most often obtained by a direct electrochemical measurement of the catalyst redox potential and might be influenced by electrostatic effects of a charged SCS. In this report, we systematically probe positive charges in a SCS and their electrostatic contributions to the electrocatalyst redox potential. A series of 11 iron carbonyl clusters modified with charged and uncharged ligands was probed, and a linear correlation between the νCO absorption band energy and electrochemical redox potentials is observed except where the SCS is positively charged.
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Affiliation(s)
- Natalia D Loewen
- Department of Chemistry, University of California, 1 Shields Avenue, Davis, California 95616, United States
| | - Santanu Pattanayak
- Department of Chemistry, University of California, 1 Shields Avenue, Davis, California 95616, United States
| | - Rolfe Herber
- Racah Institute of Physics, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel
| | - James C Fettinger
- Department of Chemistry, University of California, 1 Shields Avenue, Davis, California 95616, United States
| | - Louise A Berben
- Department of Chemistry, University of California, 1 Shields Avenue, Davis, California 95616, United States
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39
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Henke WC, Kerr TA, Sheridan TR, Henling LM, Takase MK, Day VW, Gray HB, Blakemore JD. Synthesis, structural studies, and redox chemistry of bimetallic [Mn(CO) 3] and [Re(CO) 3] complexes. Dalton Trans 2021; 50:2746-2756. [PMID: 33459317 PMCID: PMC7983307 DOI: 10.1039/d0dt03666h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Manganese ([Mn(CO)3]) and rhenium tricarbonyl ([Re(CO)3]) complexes represent a workhorse family of compounds with applications in a variety of fields. Here, the coordination, structural, and electrochemical properties of a family of mono- and bimetallic [Mn(CO)3] and [Re(CO)3] complexes are explored. In particular, a novel heterobimetallic complex featuring both [Mn(CO)3] and [Re(CO)3] units supported by 2,2'-bipyrimidine (bpm) has been synthesized, structurally characterized, and compared to the analogous monomeric and homobimetallic complexes. To enable a comprehensive structural analysis for the series of complexes, we have carried out new single crystal X-ray diffraction studies of seven compounds: Re(CO)3Cl(bpm), anti-[{Re(CO3)Cl}2(bpm)], Mn(CO)3Br(bpz) (bpz = 2,2'-bipyrazine), Mn(CO)3Br(bpm), syn- and anti-[{Mn(CO3)Br}2(bpm)], and syn-[Mn(CO3)Br(bpm)Re(CO)3Br]. Electrochemical studies reveal that the bimetallic complexes are reduced at much more positive potentials (ΔE≥ 380 mV) compared to their monometallic analogues. This redox behavior is consistent with introduction of the second tricarbonyl unit which inductively withdraws electron density from the bridging, redox-active bpm ligand, resulting in more positive reduction potentials. [Re(CO3)Cl]2(bpm) was reduced with cobaltocene; the electron paramagnetic resonance spectrum of the product exhibits an isotropic signal (near g = 2) characteristic of a ligand-centered bpm radical. Our findings highlight the facile synthesis as well as the structural characteristics and unique electrochemical behavior of this family of complexes.
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Affiliation(s)
- Wade C Henke
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, USA.
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40
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Weberg AB, McCollom SP, Thierer LM, Gau MR, Carroll PJ, Tomson NC. Using internal electrostatic fields to manipulate the valence manifolds of copper complexes. Chem Sci 2021; 12:4395-4404. [PMID: 34163703 PMCID: PMC8179517 DOI: 10.1039/d0sc06364a] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
A series of tetradentate tris(phosphinimine) ligands (R3P3tren) was developed and bound to CuI to form the trigonal pyramidal, C3v-symmetric cuprous complexes [R3P3tren-Cu][BArF4] (1PR3) (PR3 = PMe3, PMe2Ph, PMePh2, PPh3, PMe2(NEt2), BArF4 = B(C6F5)4). Electrochemical studies on the CuI complexes were undertaken, and the permethylated analog, 1PMe3, was found to display an unprecedentedly cathodic CuI/CuII redox potential (−780 mV vs. Fc/Fc+ in isobutyronitrile). Elucidation of the electronic structures of 1PR3via density functional theory (DFT) studies revealed atypical valence manifold configurations, resulting from strongly σ-donating phosphinimine moieties in the xy-plane that destabilize 2e (dxy/dx2−y2) orbital sets and uniquely stabilized a1 (dz2) orbitals. Support is provided that the a1 stabilizations result from intramolecular electrostatic fields (ESFs) generated from cationic character on the phosphinimine moieties in R3P3tren. This view is corroborated via 1-dimensional electrostatic potential maps along the z-axes of 1PR3 and their isostructural analogues. Experimental validation of this computational model is provided upon oxidation of 1PMe3 to the cupric complex [Me3P3tren-Cu][OTf]2 (2PMe3), which displays a characteristic Jahn–Teller distortion in the form of a see-saw, pseudo-Cs-symmetric geometry. A systematic anodic shift in the potential of the CuI/CuII redox couple as the steric bulk in the secondary coordination sphere increases is explained through the complexes' diminishing ability to access the ideal Cs-symmetric geometry upon oxidation. The observations and calculations discussed in this work support the presence of internal electrostatic fields within the copper complexes, which subsequently influence the complexes' properties via a method orthogonal to classic ligand field tuning. Secondary coordination sphere electrostatic effects tune the valence manifolds of copper centers, impacting molecular geometries, photophysical properties, and redox potentials.![]()
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Affiliation(s)
- Alexander B Weberg
- Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 South 34th Street Philadelphia Pennsylvania 19104 USA
| | - Samuel P McCollom
- Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 South 34th Street Philadelphia Pennsylvania 19104 USA
| | - Laura M Thierer
- Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 South 34th Street Philadelphia Pennsylvania 19104 USA
| | - Michael R Gau
- Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 South 34th Street Philadelphia Pennsylvania 19104 USA
| | - Patrick J Carroll
- Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 South 34th Street Philadelphia Pennsylvania 19104 USA
| | - Neil C Tomson
- Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 South 34th Street Philadelphia Pennsylvania 19104 USA
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41
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Kumar A, Blakemore JD. On the Use of Aqueous Metal-Aqua p Ka Values as a Descriptor of Lewis Acidity. Inorg Chem 2021; 60:1107-1115. [PMID: 33405902 DOI: 10.1021/acs.inorgchem.0c03239] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The behavior of Lewis acidic metal ions in multimetallic systems has become a subject of intense interest in recent years. Parametrizing the behavior of these ions in nonaqueous conditions, commonly used in the field, is challenging due to the lack of direct measures of the Lewis acidity of metal ions in polar organic solvents. Here, we report the use of triphenylphosphine oxide (TPPO) as a 31P nuclear magnetic resonance (NMR) probe to quantify the Lewis acidity of a library of metal triflate salts using the Gutmann-Beckett method. Plots of the pKa values of the corresponding metal-aqua species, [M(H2O)m]n+, measured in H2O vs the 31P NMR shifts of TPPO in the presence of these metals in deuterated acetonitrile (d3-MeCN) and deuterated dichloromethane (CD2Cl2), display tightly colinear relationships, suggesting similar behavior for these ions in water, d3-MeCN, and CD2Cl2. This colinearity reinforces the utility of the common approach of using the aqueous pKa values as a descriptor of Lewis acidity, regardless of the solvent used in the immediate experiments, and provides an insight into the usefulness of this descriptor in wide-ranging applications. Titration studies in d3-MeCN suggest a 1:1 binding of TPPO with monovalent ions, greater than 1:1 binding with divalent ions, and formation of multiple species with the highly Lewis acidic trivalent ions. Together, these data suggest that both aqueous pKa values and other single-measurement descriptors, while useful, provide only a snapshot of the influence of Lewis acidity on multimetallic chemical systems.
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Affiliation(s)
- Amit Kumar
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - James D Blakemore
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
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42
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Haaf S, Kaifer E, Wadepohl H, Himmel H. Use of Crown Ether Functions as Secondary Coordination Spheres for the Manipulation of Ligand-Metal Intramolecular Electron Transfer in Copper-Guanidine Complexes. Chemistry 2021; 27:959-970. [PMID: 32833269 PMCID: PMC7839521 DOI: 10.1002/chem.202003469] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Indexed: 01/16/2023]
Abstract
Intramolecular electron transfer (IET) between a redox-active organic ligand and a metal in a complex is of fundamental interest and used in a variety of applications. In this work it is demonstrated that secondary coordination sphere motifs can be applied to trigger a radical change in the electronic structure of copper complexes with a redox-active guanidine ligand through ligand-metal IET. Hence, crown ether functions attached to the ligand allow the manipulation of the degree of IET between the guanidine ligand and the copper atom through metal encapsulation.
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Affiliation(s)
- Sebastian Haaf
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Elisabeth Kaifer
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Hubert Wadepohl
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Hans‐Jörg Himmel
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
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43
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Calvary CA, Hietsoi O, Hofsommer DT, Brun HC, Costello AM, Mashuta MS, Spurgeon JM, Buchanan RM, Grapperhaus CA. Copper bis(thiosemicarbazone) Complexes with Pendent Polyamines: Effects of Proton Relays and Charged Moieties on Electrocatalytic HER. Eur J Inorg Chem 2020. [DOI: 10.1002/ejic.202000774] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Caleb A. Calvary
- Department of Chemistry University of Louisville 2320 South Brook Street Louisville KY 40292 USA
| | - Oleksandr Hietsoi
- Department of Chemistry University of Louisville 2320 South Brook Street Louisville KY 40292 USA
- Department of Chemistry Middle Tennessee State University Murfreesboro TN 37132 USA
| | - Dillon T. Hofsommer
- Department of Chemistry University of Louisville 2320 South Brook Street Louisville KY 40292 USA
| | - Henry C. Brun
- Department of Chemistry University of Louisville 2320 South Brook Street Louisville KY 40292 USA
| | - Alison M. Costello
- Department of Chemistry University of Louisville 2320 South Brook Street Louisville KY 40292 USA
| | - Mark S. Mashuta
- Department of Chemistry University of Louisville 2320 South Brook Street Louisville KY 40292 USA
| | - Joshua M. Spurgeon
- Conn Center for Renewable Energy Research University of Louisville Louisville KY 40292 USA
| | - Robert M. Buchanan
- Department of Chemistry University of Louisville 2320 South Brook Street Louisville KY 40292 USA
| | - Craig A. Grapperhaus
- Department of Chemistry University of Louisville 2320 South Brook Street Louisville KY 40292 USA
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44
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Martin DJ, Johnson SI, Mercado BQ, Raugei S, Mayer JM. Intramolecular Electrostatic Effects on O2, CO2, and Acetate Binding to a Cationic Iron Porphyrin. Inorg Chem 2020; 59:17402-17414. [DOI: 10.1021/acs.inorgchem.0c02703] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Daniel J. Martin
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Samantha I. Johnson
- Pacific Northwest National Laboratory (PNNL), Richland, Washington 99352, United States
| | - Brandon Q. Mercado
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Simone Raugei
- Pacific Northwest National Laboratory (PNNL), Richland, Washington 99352, United States
| | - James M. Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
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45
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Deacy A, Moreby E, Phanopoulos A, Williams CK. Co(III)/Alkali-Metal(I) Heterodinuclear Catalysts for the Ring-Opening Copolymerization of CO 2 and Propylene Oxide. J Am Chem Soc 2020; 142:19150-19160. [PMID: 33108736 PMCID: PMC7662907 DOI: 10.1021/jacs.0c07980] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Indexed: 02/06/2023]
Abstract
The ring-opening copolymerization of carbon dioxide and propene oxide is a useful means to valorize waste into commercially attractive poly(propylene carbonate) (PPC) polyols. The reaction is limited by low catalytic activities, poor tolerance to a large excess of chain transfer agent, and tendency to form byproducts. Here, a series of new catalysts are reported that comprise heterodinuclear Co(III)/M(I) macrocyclic complexes (where M(I) = Group 1 metal). These catalysts show highly efficient production of PPC polyols, outstanding yields (turnover numbers), quantitative carbon dioxide uptake (>99%), and high selectivity for polyol formation (>95%). The most active, a Co(III)/K(I) complex, shows a turnover frequency of 800 h-1 at low catalyst loading (0.025 mol %, 70 °C, 30 bar CO2). The copolymerizations are well controlled and produce hydroxyl telechelic PPC with predictable molar masses and narrow dispersity (Đ < 1.15). The polymerization kinetics show a second order rate law, first order in both propylene oxide and catalyst concentrations, and zeroth order in CO2 pressure. An Eyring analysis, examining the effect of temperature on the propagation rate coefficient (kp), reveals the transition state barrier for polycarbonate formation: ΔG‡ = +92.6 ± 2.5 kJ mol-1. The Co(III)/K(I) catalyst is also highly active and selective in copolymerizations of other epoxides with carbon dioxide.
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Affiliation(s)
- Arron
C. Deacy
- Department of Chemistry,
Chemistry Research Laboratory, University
of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, U.K.
| | - Emma Moreby
- Department of Chemistry,
Chemistry Research Laboratory, University
of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, U.K.
| | - Andreas Phanopoulos
- Department of Chemistry,
Chemistry Research Laboratory, University
of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, U.K.
| | - Charlotte K. Williams
- Department of Chemistry,
Chemistry Research Laboratory, University
of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, U.K.
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46
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Shoshani MM, Agapie T. Ligand architecture for triangular metal complexes: a high oxidation state Ni 3 cluster with proximal metal arrangement. Chem Commun (Camb) 2020; 56:11279-11282. [PMID: 32832943 DOI: 10.1039/d0cc03816d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new multidentate tetraanionic ligand platform for supporting trinuclear transition metal clusters has been developed. Two trisphenoxide phosphinimide ligands bind three Ni centers in a triangular arrangement. The phosphinimide donors bridge in μ3 fashion and the phenoxides complete a pseudo-square planar coordination sphere around each metal center. Electrochemical studies reveal two pseudo-reversible oxidation events at notably low potentials (-0.80 V and +0.05 V). The one electron oxidized species was characterized structurally, and it is assigned as a NiIII-containing cluster.
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Affiliation(s)
- Manar M Shoshani
- Department of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
| | - Theodor Agapie
- Department of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
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Stojičkov M, Sturm S, Čobeljić B, Pevec A, Jevtović M, Scheitler A, Radanović D, Senft L, Turel I, Andjelković K, Miehlich M, Meyer K, Ivanović‐Burmazović I. Cobalt(II), Zinc(II), Iron(III), and Copper(II) Complexes Bearing Positively Charged Quaternary Ammonium Functionalities: Synthesis, Characterization, Electrochemical Behavior, and SOD Activity. Eur J Inorg Chem 2020. [DOI: 10.1002/ejic.202000415] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Marko Stojičkov
- Faculty of Chemistry University of Belgrade Studentski trg 12‐16 11000 Belgrade Serbia
| | - Sabrina Sturm
- Department of Chemistry and Pharmacy Friedrich‐Alexander University Erlangen‐Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| | - Božidar Čobeljić
- Faculty of Chemistry University of Belgrade Studentski trg 12‐16 11000 Belgrade Serbia
| | - Andrej Pevec
- Faculty of Chemistry and Chemical Technology University of Ljubljana Večna pot 113 1000 Ljubljana Slovenia
| | - Mima Jevtović
- Faculty of Chemistry University of Belgrade Studentski trg 12‐16 11000 Belgrade Serbia
| | - Andreas Scheitler
- Department of Chemistry and Pharmacy Friedrich‐Alexander University Erlangen‐Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| | - Dušanka Radanović
- Institute of Chemistry Technology and Metallurgy University of Belgrade Njegoševa 12, P.O. Box 815 11000 Belgrade Serbia
| | - Laura Senft
- Department of Chemistry and Pharmacy Friedrich‐Alexander University Erlangen‐Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| | - Iztok Turel
- Faculty of Chemistry and Chemical Technology University of Ljubljana Večna pot 113 1000 Ljubljana Slovenia
| | - Katarina Andjelković
- Faculty of Chemistry University of Belgrade Studentski trg 12‐16 11000 Belgrade Serbia
| | - Matthias Miehlich
- Department of Chemistry and Pharmacy Friedrich‐Alexander University Erlangen‐Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| | - Karsten Meyer
- Department of Chemistry and Pharmacy Friedrich‐Alexander University Erlangen‐Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| | - Ivana Ivanović‐Burmazović
- Department of Chemistry and Pharmacy Friedrich‐Alexander University Erlangen‐Nürnberg Egerlandstr. 1 91058 Erlangen Germany
- Department Chemie Ludwigs‐Maximilians‐Universität Butenandtstraße 5‐13 81377 München Germany
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48
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Tran TV, Karas LJ, Wu JI, Do LH. Elucidating Secondary Metal Cation Effects on Nickel Olefin Polymerization Catalysts. ACS Catal 2020. [DOI: 10.1021/acscatal.0c02949] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Thi V. Tran
- Department of Chemistry, University of Houston, 4800 Calhoun Rd., Houston, Texas 77204, United States
| | - Lucas J. Karas
- Department of Chemistry, University of Houston, 4800 Calhoun Rd., Houston, Texas 77204, United States
| | - Judy I. Wu
- Department of Chemistry, University of Houston, 4800 Calhoun Rd., Houston, Texas 77204, United States
| | - Loi H. Do
- Department of Chemistry, University of Houston, 4800 Calhoun Rd., Houston, Texas 77204, United States
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49
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Meyer RL, Anjass MH, Petel BE, Brennessel WW, Streb C, Matson EM. Electronic Consequences of Ligand Substitution at Heterometal Centers in Polyoxovanadium Clusters: Controlling the Redox Properties through Heterometal Coordination Number. Chemistry 2020; 26:9905-9914. [PMID: 32196127 PMCID: PMC7496301 DOI: 10.1002/chem.201905624] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 03/13/2020] [Indexed: 02/01/2023]
Abstract
The rational control of the electrochemical properties of polyoxovanadate-alkoxide clusters is dependent on understanding the influence of various synthetic modifications on the overall redox processes of these systems. In this work, the electronic consequences of ligand substitution at the heteroion in a heterometal-functionalized cluster was examined. The redox properties of [V5 O6 (OCH3 )12 FeCl] (1-[V5 FeCl]) and [V5 O6 (OCH3 )12 Fe]X (2-[V5 Fe]X; X=ClO4 , OTf) were compared in order to assess the effects of changing the coordination environment around the iron center on the electrochemical properties of the cluster. Coordination of a chloride anion to iron leads to an anodic shift in redox events. Theoretical modelling of the electronic structure of these heterometal-functionalized clusters reveals that differences in the redox profiles of 1-[V5 FeCl] and 2-[V5 Fe]X arise from changes in the number of ligands surrounding the iron center (e.g., 6-coordinate vs. 5-coordinate). Specifically, binding of the chloride to the sixth coordination site appears to change the orbital interaction between the iron and the delocalized electronic structure of the mixed-valent polyoxovanadate core. Tuning the heterometal coordination environment can therefore be used to modulate the redox properties of the whole cluster.
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Affiliation(s)
- Rachel L. Meyer
- Department of ChemistryUniversity of RochesterRochesterNY14627USA
| | - Montaha H. Anjass
- Institute of Inorganic Chemistry IUlm UniversityAlbert-Einstein-Allee 1189081UlmGermany
- Helmholtz Institute Ulm (HIU)Helmholtzstrasse 1189081UlmGermany
| | | | | | - Carsten Streb
- Institute of Inorganic Chemistry IUlm UniversityAlbert-Einstein-Allee 1189081UlmGermany
- Helmholtz Institute Ulm (HIU)Helmholtzstrasse 1189081UlmGermany
| | - Ellen M. Matson
- Department of ChemistryUniversity of RochesterRochesterNY14627USA
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50
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Mondol R, Otten E. Cation effects on dynamics of ligand-benzylated formazanate boron and aluminium complexes. Dalton Trans 2020; 49:9094-9098. [PMID: 32573637 DOI: 10.1039/d0dt01918f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The dynamic processes present in ligand-benzylated formazanate boron and aluminium complexes are investigated using variable temperature NMR experiments and lineshape analyses. The observed difference in activation parameters for complexes containing either organic countercations (NBu4+) or alkali cations is rationalized on the basis of a different degree of ion-pairing in the ground state, and the data are in all cases consistent with a mechanism that involves pyramidal inversion at the nitrogens in the heterocyclic ring rather than homolytic N-C(benzyl) bond cleavage.
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Affiliation(s)
- Ranajit Mondol
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
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