1
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Marques HM. The inorganic chemistry of the cobalt corrinoids - an update. J Inorg Biochem 2023; 242:112154. [PMID: 36871417 DOI: 10.1016/j.jinorgbio.2023.112154] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 01/23/2023] [Accepted: 01/26/2023] [Indexed: 02/05/2023]
Abstract
The inorganic chemistry of the cobalt corrinoids, derivatives of vitamin B12, is reviewed, with particular emphasis on equilibrium constants for, and kinetics of, their axial ligand substitution reactions. The role the corrin ligand plays in controlling and modifying the properties of the metal ion is emphasised. Other aspects of the chemistry of these compounds, including their structure, corrinoid complexes with metals other than cobalt, the redox chemistry of the cobalt corrinoids and their chemical redox reactions, and their photochemistry are discussed. Their role as catalysts in non-biological reactions and aspects of their organometallic chemistry are briefly mentioned. Particular mention is made of the role that computational methods - and especially DFT calculations - have played in developing our understanding of the inorganic chemistry of these compounds. A brief overview of the biological chemistry of the B12-dependent enzymes is also given for the reader's convenience.
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Affiliation(s)
- Helder M Marques
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa.
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2
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Ghosh AP, Toda MJ, Kozlowski PM. Photolytic properties of B 12-dependent enzymes: A theoretical perspective. VITAMINS AND HORMONES 2022; 119:185-220. [PMID: 35337619 DOI: 10.1016/bs.vh.2022.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The biologically active vitamin B12 derivates, methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl), are ubiquitous organometallic cofactors. In addition to their key roles in enzymatic catalysis, B12 cofactors have complex photolytic properties which have been the target of experimental and theoretical studies. With the recent discovery of B12-dependent photoreceptors, there is an increased need to elucidate the underlying photochemical mechanisms of these systems. This book chapter summarizes the photolytic properties of MeCbl- and AdoCbl-dependent enzymes with particular emphasis on the effect of the environment of the cofactor on the excited state processes. These systems include isolated MeCbl and AdoCbl as well as the enzymes, ethanolamine ammonia-lyase (EAL), glutamate mutase (GLM), methionine synthase (MetH), and photoreceptor CarH. Central to determining the photodissociation mechanism of each system is the analysis of the lowest singlet excited state (S1) potential energy surface (PES). Time-dependent density functional theory (TD-DFT), employing BP86/TZVPP, is widely used to construct such PESs. Regardless of the environment, the topology of the S1 PES of AdoCbl or MeCbl is marked by characteristic features, namely the metal-to-ligand charge transfer (MLCT) and ligand field (LF) regions. Conversely, the relative energetics of these electronic states are affected by the environment. Applications and outlooks for Cbl photochemistry are also discussed.
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Affiliation(s)
- Arghya Pratim Ghosh
- Department of Chemistry, University of Louisville, Louisville, KY, United States
| | - Megan J Toda
- Department of Chemistry, University of Louisville, Louisville, KY, United States
| | - Pawel M Kozlowski
- Department of Chemistry, University of Louisville, Louisville, KY, United States.
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3
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Toda MJ, Lodowski P, Mamun AA, Kozlowski PM. Electronic and photolytic properties of hydridocobalamin. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2021; 224:112295. [PMID: 34548209 DOI: 10.1016/j.jphotobiol.2021.112295] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 07/06/2021] [Accepted: 08/17/2021] [Indexed: 06/13/2023]
Abstract
Hydridocobalamin (HCbl), is a known member of the B12 family of molecules (cobalamins, Cbls) yet unlike other well-studied Cbls, little is known of the electronic and photolytic properties of this species. Interest in HCbl has increased significantly in recent years when at least three experimentally proposed mechanisms implicate HCbl as an intermediary in the photoreaction of coenzyme B12-dependent photoreceptor CarH. Specifically, cleavage of the Co-C5' bond of coenzyme B12 could lead to a β-hydride or β‑hydrogen elimination reaction to form HCbl. HCbl is known to be a transient species where the oxidation state of the Co is variable; Co(I)-H+ ↔ Co(II)-H ↔ Co(III)-H-. Further, HCbl is a very unstable with a pKa of ~1. This complicates experimental studies and to the best of our knowledge there are no available crystal structures of HCbl - either for the isolated molecule or bound to an enzyme. In this study, the electronic structure, photolytic properties, and reactivity of HCbl were explored to determine the preferred oxidation state as well as its potential role in the formation of the photoproduct in CarH. Natural bond orbital (NBO) analysis was performed to determine the oxidation state of Co in isolated HCbl. Based on the NBO analysis of HCbl, Co clearly had excess negative charge, which is in stark contrast to other alkylCbls where the Co ion is marked by significant positive charge. In sum, NBO results indicate that the CoH bond is strongly polarized and almost ionic. It can be described as protonated Co(I). In addition, DFT was used to explore the bond dissociation energy of HCbl based on homolytic cleavage of the CoH bond. TD-DFT calculations were used to compare computed electronic transitions to the experimentally determined absorption spectrum. The photoreaction of CarH was explored using an isolated model system and a pathway for hydrogen transfer was found. Finally, quantum mechanics/molecular mechanics (QM/MM) calculations were employed to investigate the formation of HCbl in CarH.
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Affiliation(s)
- Megan J Toda
- Department of Chemistry, University of Louisville, Louisville, KY 40292, United States
| | - Piotr Lodowski
- Institute of Chemistry, University of Silesia in Katowice, Szkolna 9, PL-40 006 Katowice, Poland
| | - Abdullah Al Mamun
- Department of Chemistry, University of Louisville, Louisville, KY 40292, United States
| | - Pawel M Kozlowski
- Department of Chemistry, University of Louisville, Louisville, KY 40292, United States.
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4
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Potrząsaj A, Musiejuk M, Chaładaj W, Giedyk M, Gryko D. Cobalt Catalyst Determines Regioselectivity in Ring Opening of Epoxides with Aryl Halides. J Am Chem Soc 2021; 143:9368-9376. [PMID: 34081860 PMCID: PMC8297733 DOI: 10.1021/jacs.1c00659] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Ring-opening of epoxides
furnishing either linear or branched products
belongs to the group of classic transformations in organic synthesis.
However, the regioselective cross-electrophile coupling of aryl epoxides
with aryl halides still represents a key challenge. Herein, we report
that the vitamin B12/Ni dual-catalytic system allows for
the selective synthesis of linear products under blue-light irradiation,
thus complementing methodologies that give access to branched alcohols.
Experimental and theoretical studies corroborate the proposed mechanism
involving alkylcobalamin as an intermediate in this reaction.
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Affiliation(s)
- Aleksandra Potrząsaj
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | - Mateusz Musiejuk
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | - Wojciech Chaładaj
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | - Maciej Giedyk
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | - Dorota Gryko
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
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5
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Tsybizova A, Brenig C, Kieninger C, Kräutler B, Chen P. Surprising Homolytic Gas Phase Co-C Bond Dissociation Energies of Organometallic Aryl-Cobinamides Reveal Notable Non-Bonded Intramolecular Interactions. Chemistry 2021; 27:7252-7264. [PMID: 33560580 PMCID: PMC8251903 DOI: 10.1002/chem.202004589] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Indexed: 01/12/2023]
Abstract
Aryl-cobalamins are a new class of organometallic structural mimics of vitamin B12 designed as potential 'antivitamins B12 '. Here, the first cationic aryl-cobinamides are described, which were synthesized using the newly developed diaryl-iodonium method. The aryl-cobinamides were obtained as pairs of organometallic coordination isomers, the stereo-structure of which was unambiguously assigned based on homo- and heteronuclear NMR spectra. The availability of isomers with axial attachment of the aryl group, either at the 'beta' or at the 'alpha' face of the cobalt-center allowed for an unprecedented comparison of the organometallic reactivity of such pairs. The homolytic gas-phase bond dissociation energies (BDEs) of the coordination-isomeric phenyl- and 4-ethylphenyl-cobinamides were determined by ESI-MS threshold CID experiments, furnishing (Co-Csp 2 )-BDEs of 38.4 and 40.6 kcal mol-1 , respectively, for the two β-isomers, and the larger BDEs of 46.6 and 43.8 kcal mol-1 for the corresponding α-isomers. Surprisingly, the observed (Co-Csp 2 )-BDEs of the Coβ -aryl-cobinamides were smaller than the (Co-Csp 3 )-BDE of Coβ -methyl-cobinamide. DFT studies and the magnitudes of the experimental (Co-Csp 2 )-BDEs revealed relevant contributions of non-bonded interactions in aryl-cobinamides, notably steric strain between the aryl and the cobalt-corrin moieties and non-bonded interactions with and among the peripheral sidechains.
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Affiliation(s)
- Alexandra Tsybizova
- Laboratorium für Organische ChemieDepartment of Chemistry and Applied BiosciencesETH ZürichZürichSwitzerland
| | - Christopher Brenig
- Institute of Organic Chemistry & Center of Molecular BiosciencesUniversity of InnsbruckInnsbruckAustria
| | - Christoph Kieninger
- Institute of Organic Chemistry & Center of Molecular BiosciencesUniversity of InnsbruckInnsbruckAustria
| | - Bernhard Kräutler
- Institute of Organic Chemistry & Center of Molecular BiosciencesUniversity of InnsbruckInnsbruckAustria
| | - Peter Chen
- Laboratorium für Organische ChemieDepartment of Chemistry and Applied BiosciencesETH ZürichZürichSwitzerland
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6
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Toda MJ, Lodowski P, Thurman TM, Kozlowski PM. Light Mediated Properties of a Thiolato-Derivative of Vitamin B 12. Inorg Chem 2020; 59:17200-17212. [PMID: 33211475 DOI: 10.1021/acs.inorgchem.0c02414] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Vitamin B12 derivatives (Cbls = cobalamins) exhibit photolytic properties upon excitation with light. These properties can be modulated by several factors including the nature of the axial ligands. Upon excitation, homolytic cleavage of the organometallic bond to the upper axial ligand takes place in photolabile Cbls. The photosensitive nature of Cbls has made them potential candidates for light-activated drug delivery. The addition of a fluorophore to the nucleotide loop of thiolato Cbls has been shown to shift the region of photohomolysis to within the optical window of tissue (600-900 nm). With this possibility, there is a need to analyze photolytic properties of unique Cbls which contain a Co-S bond. Herein, the photodissociation of one such Cbl, namely, N-acetylcysteinylcobalamin (NACCbl), is analyzed based on density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The S0 and S1 potential energy surfaces (PESs), as a function of axial bond lengths, were computed to determine the mechanism of photodissociation. Like other Cbls, the S1 PES contains metal-to-ligand charge transfer (MLCT) and ligand field (LF) regions, but there are some unique differences. Interestingly, the S1 PES of NACCbl contains three distinct minima regions opening several possibilities for the mechanism of radical pair (RP) formation. The mild photoresponsiveness, observed experimentally, can be attributed to the small gap in energy between the S1 and S0 PESs. Compared to other Cbls, the gap shown for NACCbl is neither exactly in line with the alkyl Cbls nor the nonalkyl Cbls.
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Affiliation(s)
- Megan J Toda
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, United States
| | - Piotr Lodowski
- Department of Theoretical Chemistry, Institute of Chemistry, University of Silesia in Katowice, Szkolna 9, PL-40 006 Katowice, Poland
| | - Todd M Thurman
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, United States
| | - Pawel M Kozlowski
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, United States
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7
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Sitek P, Chmielowska A, Jaworska M, Lodowski P, Szczepańska M. Theoretical study of cobalt and nickel complexes involved in methyl transfer reactions: structures, redox potentials and methyl binding energies. Struct Chem 2019. [DOI: 10.1007/s11224-019-01384-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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8
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Elucidating the mechanism of cob(I)alamin mediated methylation reactions by alkyl halides: SN2 or radical mechanism? J Catal 2019. [DOI: 10.1016/j.jcat.2019.06.036] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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9
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Toda MJ, Lodowski P, Mamun AA, Jaworska M, Kozlowski PM. Photolytic properties of the biologically active forms of vitamin B12. Coord Chem Rev 2019. [DOI: 10.1016/j.ccr.2018.12.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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10
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Mamun AA, Toda MJ, Kozlowski PM. Can photolysis of the Co C bond in coenzyme B12-dependent enzymes be used to mimic the native reaction? JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2019; 191:175-184. [DOI: 10.1016/j.jphotobiol.2018.12.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 12/19/2018] [Accepted: 12/20/2018] [Indexed: 12/22/2022]
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11
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Nowakowska M, Chemaly SM, Rousseau AL, Govender PP, Varadwaj PR, Varadwaj A, Yamashita K, Marques HM. Probing the nature of the Co(III) ion in corrins: The reactions of aquacyano-5-seco-cobyrinic acid heptamethyl ester with anionic ligands. Inorganica Chim Acta 2019. [DOI: 10.1016/j.ica.2018.09.073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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12
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Wick CR, Smith DM. Modeling the Reactions Catalyzed by Coenzyme B 12 Dependent Enzymes: Accuracy and Cost-Quality Balance. J Phys Chem A 2018; 122:1747-1755. [PMID: 29389127 DOI: 10.1021/acs.jpca.7b11798] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The reactions catalyzed by coenzyme B12 dependent enzymes are formally initiated by the homolytic cleavage of a carbon-cobalt bond and a subsequent or concerted H-atom-transfer reaction. A reasonable model chemistry for describing those reactions should, therefore, account for an accurate description of both reactions. The inherent limitation due to the necessary system size renders the coenzyme B12 system a suitable candidate for DFT or hybrid QM/MM methods; however, the accurate description of both homolytic Co-C cleavage and H-atom-transfer reactions within this framework is challenging and can lead to controversial results with varying accuracy. We present an assessment study of 16 common density functionals applied to prototypical model systems for both reactions. H-abstraction reactions were modeled on the basis of four reference reactions designed to resemble a broad range of coenzyme B12 reactions. The Co-C cleavage reaction is treated by an ONIOM(QM/MM) setup that is in excellent agreement with solution-phase experimental data and is as accurate as full DFT calculations on the complete model system. We find that the meta-GGAs TPSS-D3 and M06L-D3 and the meta-hybrid M06-D3 give the best overall performance with MUEs for both types of reactions below 10 kJ mol-1. Our recommended model chemistry allows for a fast and accurate description of coenzyme B12 chemistry that is readily applicable to study the reactions in an enzymatic framework.
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Affiliation(s)
- Christian R Wick
- Division of Physical Chemistry, Group for Computational Life Sciences, Ruđer Bošković Institute , Bijenička cesta 54, 10000 Zagreb, Croatia
| | - David M Smith
- Division of Physical Chemistry, Group for Computational Life Sciences, Ruđer Bošković Institute , Bijenička cesta 54, 10000 Zagreb, Croatia.,Center for Computational Chemistry, FAU Erlangen-Nürnberg , Nägelsbachstrasse 25, 91052 Erlangen, Germany
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13
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Pavlova A, Parks JM, Gumbart JC. Development of CHARMM-Compatible Force-Field Parameters for Cobalamin and Related Cofactors from Quantum Mechanical Calculations. J Chem Theory Comput 2018; 14:784-798. [PMID: 29334459 DOI: 10.1021/acs.jctc.7b01236] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Corrinoid cofactors such as cobalamin are used by many enzymes and are essential for most living organisms. Therefore, there is broad interest in investigating cobalamin-protein interactions with molecular dynamics simulations. Previously developed parameters for cobalamins are based mainly on crystal structure data. Here, we report CHARMM-compatible force field parameters for several corrinoids developed from quantum mechanical calculations. We provide parameters for corrinoids in three oxidation states, Co3+, Co2+, and Co1+, and with various axial ligands. Lennard-Jones parameters for the cobalt center in the Co(II) and Co(I) states were optimized using a helium atom probe, and partial atomic charges were obtained with a combination of natural population analysis (NPA) and restrained electrostatic potential (RESP) fitting approaches. The Force Field Toolkit was used to optimize all bonded terms. The resulting parameters, determined solely from calculations of cobalamin alone or in water, were then validated by assessing their agreement with density functional theory geometries and by analyzing molecular dynamics simulation trajectories of several corrinoid proteins for which X-ray crystal structures are available. In each case, we obtained excellent agreement with the reference data. In comparison to previous CHARMM-compatible parameters for cobalamin, we observe a better agreement for the fold angle and lower RMSD in the cobalamin binding site. The approach described here is readily adaptable for developing CHARMM-compatible force-field parameters for other corrinoids or large biomolecules.
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Affiliation(s)
- Anna Pavlova
- School of Physics, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Jerry M Parks
- Biosciences Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - James C Gumbart
- School of Physics, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.,School of Chemistry and Biochemistry, Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
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14
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Kepp KP. Energy vs. density on paths toward more exact density functionals. Phys Chem Chem Phys 2018; 20:7538-7548. [DOI: 10.1039/c7cp07730k] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The density-energy balance of density functionals is quantified using trial densities. Density errors commonly amount to only a few kJ mol−1.
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Affiliation(s)
- Kasper P. Kepp
- Technical University of Denmark, DTU Chemistry, Building 206
- 2800 Kgs. Lyngby
- Denmark
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15
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Ji L, Wang C, Ji S, Kepp KP, Paneth P. Mechanism of Cobalamin-Mediated Reductive Dehalogenation of Chloroethylenes. ACS Catal 2017. [DOI: 10.1021/acscatal.7b00540] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Li Ji
- College
of Environmental and Resource Sciences, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058, China
| | - Chenchen Wang
- College
of Environmental and Resource Sciences, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058, China
| | - Shujing Ji
- College
of Environmental and Resource Sciences, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058, China
| | - Kasper P. Kepp
- DTU
Chemistry, Technical University of Denmark, Building 206, Kgs. Lyngby DK-2800, Denmark
| | - Piotr Paneth
- Institute
of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland
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16
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Johnston RC, Zhou J, Smith JC, Parks JM. Toward Quantitatively Accurate Calculation of the Redox-Associated Acid-Base and Ligand Binding Equilibria of Aquacobalamin. J Phys Chem B 2016; 120:7307-18. [PMID: 27391132 DOI: 10.1021/acs.jpcb.6b02701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Redox processes in complex transition metal-containing species are often intimately associated with changes in ligand protonation states and metal coordination number. A major challenge is therefore to develop consistent computational approaches for computing pH-dependent redox and ligand dissociation properties of organometallic species. Reduction of the Co center in the vitamin B12 derivative aquacobalamin can be accompanied by ligand dissociation, protonation, or both, making these properties difficult to compute accurately. We examine this challenge here by using density functional theory and continuum solvation to compute Co-ligand binding equilibrium constants (Kon/off), pKas, and reduction potentials for models of aquacobalamin in aqueous solution. We consider two models for cobalamin ligand coordination: the first follows the hexa, penta, tetra coordination scheme for Co(III), Co(II), and Co(I) species, respectively, and the second model features saturation of each vacant axial coordination site on Co(II) and Co(I) species with a single, explicit water molecule to maintain six directly interacting ligands or water molecules in each oxidation state. Comparing these two coordination schemes in combination with five dispersion-corrected density functionals, we find that the accuracy of the computed properties is largely independent of the scheme used, but including only a continuum representation of the solvent yields marginally better results than saturating the first solvation shell around Co throughout. PBE performs best, displaying balanced accuracy and superior performance overall, with RMS errors of 80 mV for seven reduction potentials, 2.0 log units for five pKas and 2.3 log units for two log Kon/off values for the aquacobalamin system. Furthermore, we find that the BP86 functional commonly used in corrinoid studies suffers from erratic behavior and inaccurate descriptions of Co-axial ligand binding, leading to substantial errors in predicted pKas and Kon/off values. These findings demonstrate the effectiveness of the present approach for computing electrochemical and thermodynamic properties of a complex transition metal-containing cofactor.
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Affiliation(s)
- Ryne C Johnston
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory , 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6309, United States
| | | | | | - Jerry M Parks
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory , 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6309, United States
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17
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Garabato BD, Lodowski P, Jaworska M, Kozlowski PM. Mechanism of Co-C photodissociation in adenosylcobalamin. Phys Chem Chem Phys 2016; 18:19070-82. [PMID: 27356617 DOI: 10.1039/c6cp02136k] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A mechanism of Co-C bond photodissociation in the base-on form of adenosylcobalamin (AdoCbl) was investigated by time-dependent density functional theory (TD-DFT). The key mechanistic step involves singlet radical pair (RP) generation from the first electronically excited state (S1). To connect TD-DFT calculations with ultra-fast excited state dynamics, the potential energy surface (PES) of the S1 state was constructed using Co-C and Co-NIm axial coordinates. The S1 PES can be characterized by two minima separated by a seam resulting from the crossing of two surfaces, of metal-to-ligand charge transfer (MLCT) character near the minimum, and a shallow ligand field (LF) surface at elongated axial bond distances. Only one possible pathway for photolysis (path A) was identified based on energetic grounds. This pathway is characterized by the first elongation of the Co-C bond, followed by photolysis from an LF state where the axial base is partially detached. A new perspective on the photolysis of AdoCbl is then gained by connecting TD-DFT results with available experimental observations.
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Affiliation(s)
- Brady D Garabato
- Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, Kentucky 40202, USA.
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18
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Spataru T, Fernandez F. The Nature of the Co-C Bond Cleavage Processes in Methylcob(II)Alamin and Adenosylcob(III)Alamin. CHEMISTRY JOURNAL OF MOLDOVA 2016. [DOI: 10.19261/cjm.2016.11(1).01] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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19
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Abstract
Iron complexes are important spin crossover (SCO) systems with vital roles in oxidative metabolism and promising technological potential. The SCO tendency depends on the free energy balance of high- and low-spin states, which again depends on physical effects such as dispersion, relativistic effects, and vibrational entropy. This work studied 30 different iron SCO systems with experimentally known thermochemical data, using 12 different density functionals. Remarkably general entropy-enthalpy compensation across SCO systems was identified (R = 0.82, p = 0.002) that should be considered in rational SCO design. Iron(II) complexes displayed higher ΔH and ΔS values than iron(III) complexes and also less steep compensation effects. First-coordination sphere ΔS values computed from numerical frequencies reproduce most of the experimental entropy and should thus be included when modeling spin-state changes in inorganic chemistry (R = 0.52, p = 3.4 × 10(-3); standard error in TΔS ≈ 4.4 kJ/mol at 298 K vs 16 kJ/mol of total TΔS on average). Zero-point energies favored high-spin states by 9 kJ/mol on average. Interestingly, dispersion effects are surprisingly large for the SCO process (average: 9 kJ/mol, but up to 33 kJ/mol) and favor the more compact low-spin state. Relativistic effects favor low-spin by ∼9 kJ/mol on average, but up to 24 kJ/mol. B3LYP*, TPSSh, B2PLYP, and PW6B95 performed best for the typical calculation scheme that includes ZPE. However, if relativistic and dispersion effects are included, only B3LYP* remained accurate. On average, high-spin was favored by LYP by 11-15 kJ/mol relative to other correlation functionals, and by 4.2 kJ/mol per 1% HF exchange in hybrids. 13% HF exchange was optimal without dispersion, and 15% was optimal with all effects included for these systems.
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Affiliation(s)
- Kasper P Kepp
- DTU Chemistry, Technical University of Denmark , Building 206, Lyngby DK-2800, Denmark
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20
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Kozlowski PM, Garabato BD, Lodowski P, Jaworska M. Photolytic properties of cobalamins: a theoretical perspective. Dalton Trans 2016; 45:4457-70. [PMID: 26865262 DOI: 10.1039/c5dt04286k] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
This Perspective Article highlights recent theoretical developments, and summarizes the current understanding of the photolytic properties of cobalamins from a computational point of view. The primary focus is on two alkyl cobalamins, methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl), as well as two non-alkyl cobalamins, cyanocobalamin (CNCbl) and hydroxocobalamin (HOCbl). Photolysis of alkyl cobalamins involves low-lying singlet excited states where photodissociation of the Co-C bond leads to formation of singlet-born alkyl/cob(ii)alamin radical pairs (RPs). Potential energy surfaces (PESs) associated with cobalamin low-lying excited states as functions of both axial bonds, provide the most reliable tool for initial analysis of their photochemical and photophysical properties. Due to the complexity, and size limitations associated with the cobalamins, the primary method for calculating ground state properties is density functional theory (DFT), while time-dependent DFT (TD-DFT) is used for electronically excited states. For alkyl cobalamins, energy pathways on the lowest singlet surface, connecting metal-to-ligand charge transfer (MLCT) and ligand field (LF) minima, can be associated with photo-homolysis of the Co-C bond observed experimentally. Additionally, energy pathways between minima and seams associated with crossing of S1/S0 surfaces, are the most efficient for internal conversion (IC) to the ground state. Depending on the specific cobalamin, such IC may involve simultaneous elongation of both axial bonds (CNCbl), or detachment of axial base followed by corrin ring distortion (MeCbl). The possibility of intersystem crossing, and the formation of triplet RPs is also discussed based on Landau-Zener theory.
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Affiliation(s)
- Pawel M Kozlowski
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, USA.
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Lodowski P, Jaworska M, Garabato BD, Kozlowski PM. Mechanism of Co–C Bond Photolysis in Methylcobalamin: Influence of Axial Base. J Phys Chem A 2015; 119:3913-28. [DOI: 10.1021/jp5120674] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Piotr Lodowski
- Department
of Theoretical Chemistry, Institute of Chemistry, University of Silesia, Szkolna 9, PL-40 006 Katowice, Poland
| | - Maria Jaworska
- Department
of Theoretical Chemistry, Institute of Chemistry, University of Silesia, Szkolna 9, PL-40 006 Katowice, Poland
| | - Brady D. Garabato
- Department
of Chemistry, University of Louisville, Louisville, Kentucky 40292, United States
| | - Pawel M. Kozlowski
- Department
of Chemistry, University of Louisville, Louisville, Kentucky 40292, United States
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Grimme S, Hansen A. A Practicable Real-Space Measure and Visualization of Static Electron-Correlation Effects. Angew Chem Int Ed Engl 2015; 54:12308-13. [DOI: 10.1002/anie.201501887] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Indexed: 11/10/2022]
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Grimme S, Hansen A. Ein praktikables räumliches Maß für Effekte statischer Elektronenkorrelation und deren Visualisierung. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201501887] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Qu ZW, Hansen A, Grimme S. Co–C Bond Dissociation Energies in Cobalamin Derivatives and Dispersion Effects: Anomaly or Just Challenging? J Chem Theory Comput 2015; 11:1037-45. [DOI: 10.1021/acs.jctc.5b00007] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Zheng-wang Qu
- Mulliken
Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie der Universität Bonn, Beringstraße
4, 53115 Bonn, North Rhine-Westphalia, Germany
| | - Andreas Hansen
- Mulliken
Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie der Universität Bonn, Beringstraße
4, 53115 Bonn, North Rhine-Westphalia, Germany
| | - Stefan Grimme
- Mulliken
Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie der Universität Bonn, Beringstraße
4, 53115 Bonn, North Rhine-Westphalia, Germany
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