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Helder M. Marques - One of the best experts on this subject based on the ideXlab platform.
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Probing the nature of the Co(III) ion in Corrins: The reactions of aquacyano-5-seco-cobyrinic acid heptamethyl ester with anionic ligands
Inorganica Chimica Acta, 2019Co-Authors: Monika Nowakowska, Susan M. Chemaly, Amanda L. Rousseau, Patrick Govender, Pradeep R. Varadwaj, Arpita Varadwaj, Koichi Yamashita, Helder M. MarquesAbstract:Abstract The substitution of H2O in aquacyano-5,6-dioxo-5,6-seco-heptamethyl-cob(III)yrinate, (aquacyano-5-seco-cobester, [AC-5-seco-Cbs]+), in which the C5–C6 bond of the corrin ring of this vitamin B12 derivative is cleaved, by a variety of anionic ligands is reported. The pKa for ionization of coordinated water decreases from 9.8 ± 0.3 in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, [ACCbs]+) to 7.28 at 25 °C (ΔH = –88 ± 17 kJ mol−1 and ΔS = –434 ± 56 J K−1 mol−1) in [AC-5-seco-Cbs]+. The pKa, confirmed by determining the pH-dependence of coordination of SO32– by [AC-5-seco-Cbs]+, shows Co(III) in this complex behaves much more like Co(III) in simple hexacoordinate complexes than in intact cobalt Corrins. A comparison of log K values for coordination of CN–, SO32–, NO2–, N3– and S2O32– by [ACCbs]+ and [AC-5-seco-Cbs]+ demonstrates that cleavage of the corrin ring significantly decreases the affinity of Co(III) for the softer ligands CN–, SO32– and, more marginally, NO2–. However, [AC-5-seco-Cbs]+ has a higher affinity for N3– and S2O32– than [ACCbs]+. These trends correlate with the position of the ligands in the spectrochemical series (N3–
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Probing the Nature of the Co(III) Ion in Corrins: Comparison of Reactions of Aquacyanocobyrinic Acid Heptamethyl Ester and Aquacyano-Stable Yellow Cobyrinic Acid Hexamethyl Ester with Neutral N‑Donor Ligands
2013Co-Authors: Susan M. Chemaly, Monika Nowakowska, Louise Kendall, Dale Pon, Christopher B. Perry, Helder M. MarquesAbstract:Equilibrium constants (log K) for substitution of coordinated H2O in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, ACCbs) and aquacyano-stable yellow cobyrinic acid hexamethyl ester (aquacyano-stable yellow cobester, ACSYCbs), in which oxidation of the C5 carbon of the corrin interrupts the normal delocalized system of Corrins, by neutral N-donor ligands (ammonia, ethanolamine, 2-methoxyethylamine, N-methylimidazole, and 4-methylpyridine) have been determined spectrophotometrically as a function of temperature. Log K values increase with the basicity of the ligand, but a strong compensation effect between ΔH and ΔS values causes a leveling effect. The aliphatic amines with a harder donor atom produce ΔH values that are more negative in their reactions with ACSYCbs than with ACCbs, while the softer, aromatic N donors produce more negative ΔH values with ACCbs than with ACSYCbs. Molecular modeling (DFT, M06L/SVP, and a quantum theory of atoms in molecules analysis of the electron density) shows that complexes of the aliphatic amines with SYCbs produce shorter and stronger Co–N bonds with less ionic character than the Co–N bonds of these ligands with the cobester. Conversely, the Co–N bond to the aromatic N donors is shorter, stronger, and somewhat less ionic in the complexes of the cobester than in those of the SYCbs. Therefore, the distinction between the harder Co(III) in ACSYCbs and softer Co(III) in ACCbs, reported previously for anionic ligands, is maintained for neutral N-donor ligands
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Probing the nature of the Co(III) ion in Corrins: comparison of reactions of aquacyanocobyrinic acid heptamethyl ester and aquacyano-stable yellow cobyrinic acid hexamethyl ester with neutral N-donor ligands.
Inorganic chemistry, 2012Co-Authors: Susan M. Chemaly, Monika Nowakowska, Louise Kendall, Dale Pon, Christopher B. Perry, Helder M. MarquesAbstract:Equilibrium constants (log K) for substitution of coordinated H2O in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, ACCbs) and aquacyano-stable yellow cobyrinic acid hexamethyl ester (aquacyano-stable yellow cobester, ACSYCbs), in which oxidation of the C5 carbon of the corrin interrupts the normal delocalized system of Corrins, by neutral N-donor ligands (ammonia, ethanolamine, 2-methoxyethylamine, N-methylimidazole, and 4-methylpyridine) have been determined spectrophotometrically as a function of temperature. Log K values increase with the basicity of the ligand, but a strong compensation effect between ΔH and ΔS values causes a leveling effect. The aliphatic amines with a harder donor atom produce ΔH values that are more negative in their reactions with ACSYCbs than with ACCbs, while the softer, aromatic N donors produce more negative ΔH values with ACCbs than with ACSYCbs. Molecular modeling (DFT, M06L/SVP, and a quantum theory of atoms in molecules analysis of the electron density) sh...
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The cis influence of the corrin in vitamin B12 models
Chemical Physics Letters, 2012Co-Authors: Patrick Govender, Christopher B. Perry, Isabelle Navizet, Helder M. MarquesAbstract:Abstract Density Functional Theory (DFT) and Quantum Theory of Atoms in Molecules (QTAIM) calculations on [NH 3 [Co(III)(C10-X-corrin)]–CH 3 ] + , where the C10–H of corrin is replaced by electron-donating or –withdrawing groups, X, explore the cis influence in these vitamin B 12 models. As the electron donating ability of X increases, a normal trans influence is observed: the Co–NH 3 bond weakens while the Co–CH 3 bond strengthens. Surprisingly, though, the Co–CH 3 bond dissociation energy decreases monotonically as the Co–C bond strengthens. This is found to be a consequence of the extent of shortening of the Co–NH 3 during the homolysis reaction.
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Probing the nature of the Co(III) ion in Corrins: a comparison of the thermodynamics and kinetics of the ligand substitution reactions of aquacyanocobyrinic acid heptamethyl ester and stable yellow aquacyanocobyrinic acid heptamethyl ester.
Inorganic chemistry, 2011Co-Authors: Susan M. Chemaly, Melissa Florczak, Heinrich Dirr, Helder M. MarquesAbstract:Equilibrium constants (log K) for the substitution of coordinated H(2)O in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, ACCbs) and stable yellow aquacyanocobyrinic acid heptamethyl ester (stable yellow aquacyanocobester, ACSYCbs), in which oxidation of the C5 carbon of the corrin interrupts the normal delocalized system of Corrins, by ligands with soft (CN(-), SO(3)(2-), and S(2)O(3)(2-)) and hard (NO(2)(-) and N(3)(-)) donors have been determined. The ligands with a harder donor atom (N in N(3)(-) and NO(2)(-)) produce ΔH values that are more negative in their reactions with ACSYCbs than with ACCbs. If the donor atom is softer (C in CN(-) and S in SO(3)(2-)), then ΔH is less positive, or more negative, for reactions with ACCbs than with ACSYCbs. The softer metal in ACCbs has a preference for softer ligands and the harder metal in ACSYCbs for the harder ligands. A kinetics study in which CN(-) substitutes H(2)O on Co(III) shows that ACCbs is more labile than ACSYCbs; the second-order rate constant k(II) is between 4.6 (at 5 °C) and 2.6 (at 35 °C) times larger. ΔH(‡) for the reaction of CN(-) with ACCbs is smaller by some 12 kJ mol(-1) than that for the reaction with ACSYCbs, consistent with an earlier transition state in which bonding between the softer metal of ACCbs and the ligand is greater than that of ACSYCbs with its harder metal. This difference in ΔH(‡) makes ACCbs over 100 times more labile, although the effect is masked by a ΔS(‡) value that is over 30 J K(-1) mol(-1) more negative. There is a significant increase in the inertness of Co(III) upon a decrease in the extent of conjugation of the corrin ligand. Modifying the electronic structure of the equatorial ligand in the cobalt Corrins can modify the thermodynamics and kinetics of its reactions with exogenous ligands.
Susan M. Chemaly - One of the best experts on this subject based on the ideXlab platform.
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Probing the nature of the Co(III) ion in Corrins: The reactions of aquacyano-5-seco-cobyrinic acid heptamethyl ester with anionic ligands
Inorganica Chimica Acta, 2019Co-Authors: Monika Nowakowska, Susan M. Chemaly, Amanda L. Rousseau, Patrick Govender, Pradeep R. Varadwaj, Arpita Varadwaj, Koichi Yamashita, Helder M. MarquesAbstract:Abstract The substitution of H2O in aquacyano-5,6-dioxo-5,6-seco-heptamethyl-cob(III)yrinate, (aquacyano-5-seco-cobester, [AC-5-seco-Cbs]+), in which the C5–C6 bond of the corrin ring of this vitamin B12 derivative is cleaved, by a variety of anionic ligands is reported. The pKa for ionization of coordinated water decreases from 9.8 ± 0.3 in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, [ACCbs]+) to 7.28 at 25 °C (ΔH = –88 ± 17 kJ mol−1 and ΔS = –434 ± 56 J K−1 mol−1) in [AC-5-seco-Cbs]+. The pKa, confirmed by determining the pH-dependence of coordination of SO32– by [AC-5-seco-Cbs]+, shows Co(III) in this complex behaves much more like Co(III) in simple hexacoordinate complexes than in intact cobalt Corrins. A comparison of log K values for coordination of CN–, SO32–, NO2–, N3– and S2O32– by [ACCbs]+ and [AC-5-seco-Cbs]+ demonstrates that cleavage of the corrin ring significantly decreases the affinity of Co(III) for the softer ligands CN–, SO32– and, more marginally, NO2–. However, [AC-5-seco-Cbs]+ has a higher affinity for N3– and S2O32– than [ACCbs]+. These trends correlate with the position of the ligands in the spectrochemical series (N3–
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Probing the Nature of the Co(III) Ion in Corrins: Comparison of Reactions of Aquacyanocobyrinic Acid Heptamethyl Ester and Aquacyano-Stable Yellow Cobyrinic Acid Hexamethyl Ester with Neutral N‑Donor Ligands
2013Co-Authors: Susan M. Chemaly, Monika Nowakowska, Louise Kendall, Dale Pon, Christopher B. Perry, Helder M. MarquesAbstract:Equilibrium constants (log K) for substitution of coordinated H2O in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, ACCbs) and aquacyano-stable yellow cobyrinic acid hexamethyl ester (aquacyano-stable yellow cobester, ACSYCbs), in which oxidation of the C5 carbon of the corrin interrupts the normal delocalized system of Corrins, by neutral N-donor ligands (ammonia, ethanolamine, 2-methoxyethylamine, N-methylimidazole, and 4-methylpyridine) have been determined spectrophotometrically as a function of temperature. Log K values increase with the basicity of the ligand, but a strong compensation effect between ΔH and ΔS values causes a leveling effect. The aliphatic amines with a harder donor atom produce ΔH values that are more negative in their reactions with ACSYCbs than with ACCbs, while the softer, aromatic N donors produce more negative ΔH values with ACCbs than with ACSYCbs. Molecular modeling (DFT, M06L/SVP, and a quantum theory of atoms in molecules analysis of the electron density) shows that complexes of the aliphatic amines with SYCbs produce shorter and stronger Co–N bonds with less ionic character than the Co–N bonds of these ligands with the cobester. Conversely, the Co–N bond to the aromatic N donors is shorter, stronger, and somewhat less ionic in the complexes of the cobester than in those of the SYCbs. Therefore, the distinction between the harder Co(III) in ACSYCbs and softer Co(III) in ACCbs, reported previously for anionic ligands, is maintained for neutral N-donor ligands
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Probing the nature of the Co(III) ion in Corrins: comparison of reactions of aquacyanocobyrinic acid heptamethyl ester and aquacyano-stable yellow cobyrinic acid hexamethyl ester with neutral N-donor ligands.
Inorganic chemistry, 2012Co-Authors: Susan M. Chemaly, Monika Nowakowska, Louise Kendall, Dale Pon, Christopher B. Perry, Helder M. MarquesAbstract:Equilibrium constants (log K) for substitution of coordinated H2O in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, ACCbs) and aquacyano-stable yellow cobyrinic acid hexamethyl ester (aquacyano-stable yellow cobester, ACSYCbs), in which oxidation of the C5 carbon of the corrin interrupts the normal delocalized system of Corrins, by neutral N-donor ligands (ammonia, ethanolamine, 2-methoxyethylamine, N-methylimidazole, and 4-methylpyridine) have been determined spectrophotometrically as a function of temperature. Log K values increase with the basicity of the ligand, but a strong compensation effect between ΔH and ΔS values causes a leveling effect. The aliphatic amines with a harder donor atom produce ΔH values that are more negative in their reactions with ACSYCbs than with ACCbs, while the softer, aromatic N donors produce more negative ΔH values with ACCbs than with ACSYCbs. Molecular modeling (DFT, M06L/SVP, and a quantum theory of atoms in molecules analysis of the electron density) sh...
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Probing the nature of the Co(III) ion in Corrins: a comparison of the thermodynamics and kinetics of the ligand substitution reactions of aquacyanocobyrinic acid heptamethyl ester and stable yellow aquacyanocobyrinic acid heptamethyl ester.
Inorganic chemistry, 2011Co-Authors: Susan M. Chemaly, Melissa Florczak, Heinrich Dirr, Helder M. MarquesAbstract:Equilibrium constants (log K) for the substitution of coordinated H(2)O in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, ACCbs) and stable yellow aquacyanocobyrinic acid heptamethyl ester (stable yellow aquacyanocobester, ACSYCbs), in which oxidation of the C5 carbon of the corrin interrupts the normal delocalized system of Corrins, by ligands with soft (CN(-), SO(3)(2-), and S(2)O(3)(2-)) and hard (NO(2)(-) and N(3)(-)) donors have been determined. The ligands with a harder donor atom (N in N(3)(-) and NO(2)(-)) produce ΔH values that are more negative in their reactions with ACSYCbs than with ACCbs. If the donor atom is softer (C in CN(-) and S in SO(3)(2-)), then ΔH is less positive, or more negative, for reactions with ACCbs than with ACSYCbs. The softer metal in ACCbs has a preference for softer ligands and the harder metal in ACSYCbs for the harder ligands. A kinetics study in which CN(-) substitutes H(2)O on Co(III) shows that ACCbs is more labile than ACSYCbs; the second-order rate constant k(II) is between 4.6 (at 5 °C) and 2.6 (at 35 °C) times larger. ΔH(‡) for the reaction of CN(-) with ACCbs is smaller by some 12 kJ mol(-1) than that for the reaction with ACSYCbs, consistent with an earlier transition state in which bonding between the softer metal of ACCbs and the ligand is greater than that of ACSYCbs with its harder metal. This difference in ΔH(‡) makes ACCbs over 100 times more labile, although the effect is masked by a ΔS(‡) value that is over 30 J K(-1) mol(-1) more negative. There is a significant increase in the inertness of Co(III) upon a decrease in the extent of conjugation of the corrin ligand. Modifying the electronic structure of the equatorial ligand in the cobalt Corrins can modify the thermodynamics and kinetics of its reactions with exogenous ligands.
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Probing the nature of the Co(III) ion in Corrins: the structural and electronic properties of dicyano- and aquacyanocobyrinic acid heptamethyl ester and a stable yellow dicyano- and aquacyanocobyrinic acid heptamethyl ester.
Inorganic chemistry, 2011Co-Authors: Susan M. Chemaly, Kenneth L Brown, Manuel A. Fernandes, Orde Q. Munro, Craig D. Grimmer, Helder M. MarquesAbstract:A stable yellow derivative of cobyrinic acid heptamethyl ester, (5R,6R)-Coα,Coβ-dicyano-5,6-dihydro-5-hydroxy-heptamethylcob(III)yrinate-c,6-lactone (DCSYCbs), was prepared from dicyanocobyrinic acid heptamethyl ester (DCCbs). The C5 carbon is oxidized and the c side chain cyclized to form a lactone at C6; the 13 atom, 14 π-e(-) delocalized system of Corrins is interrupted, giving a triazamethine system with four conjugated double bonds between N22 and N24 and an isolated double bond between N21 and C4. Stable yellow aquacyanocobyrinic acid heptamethyl ester (ACSYCbs) was prepared by driving off HCN with N(2) in a methanol/acetic acid solution. The electronic spectra of DCCbs and DCSYCbs appear similar except that the bands in DCSYCbs are shifted to shorter wavelengths and the γ-band is much less intense. The experimental spectra were adequately modeled using TD-DFT at the PBE1PBE/6-311G(d,p) level of theory. DCSYCbs crystallizes in the space group P2(1)2(1)2(1) (R(1) = 6.08%) with Z = 4, including one methanol solvent molecule and one water molecule per cobester. The addition of a hydroxyl group at C5 causes loss of the double bond between C5 and C6 and elongation of the C5-C6 bond. From a combination of two-dimensional (1)H TOCSY and ROESY NMR spectra and (1)H/(13)C HSQC and HMBC data, the complete (1)H and (13)C NMR assignments of DCSYCbs were possible, except for two of the ester methyl groups and the (13)C resonances of the two axial cyanide ligands. The latter were assigned using relative chemical shifts calculated by GIAO-DFT methods. The (59)Co resonance of DCCbs was observed at 4074 ppm while that of DCSYCbs is shifted downfield to 4298 ppm. Comparison with available (59)Co data of analogous systems suggests that the more π-conjugated corrin of DCCbs interacts more strongly with the metal than the less extensively conjugated macrocycle of DCSYCbs. As the strength of the interaction between Co(III) and an equatorial macrocycle increases, ν(CN) of axially coordinated CN(-) shifts to lower frequency; in DCSYCbs and DCCbs ν(CN) occurs at 2138 and 2123 cm(-1), respectively. Hence the corrin ligand in DCCbs interacts more strongly with the metal than the stable yellow corrin ligand, with its diminished conjugation. The UV-vis spectral data and DFT-calculated MOs are consistent with greater overlap between the corrin and the metal orbitals in DCCbs relative to DCSYCbs, which gives the metal in the former a softer, more covalent character.
Monika Nowakowska - One of the best experts on this subject based on the ideXlab platform.
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Probing the nature of the Co(III) ion in Corrins: The reactions of aquacyano-5-seco-cobyrinic acid heptamethyl ester with anionic ligands
Inorganica Chimica Acta, 2019Co-Authors: Monika Nowakowska, Susan M. Chemaly, Amanda L. Rousseau, Patrick Govender, Pradeep R. Varadwaj, Arpita Varadwaj, Koichi Yamashita, Helder M. MarquesAbstract:Abstract The substitution of H2O in aquacyano-5,6-dioxo-5,6-seco-heptamethyl-cob(III)yrinate, (aquacyano-5-seco-cobester, [AC-5-seco-Cbs]+), in which the C5–C6 bond of the corrin ring of this vitamin B12 derivative is cleaved, by a variety of anionic ligands is reported. The pKa for ionization of coordinated water decreases from 9.8 ± 0.3 in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, [ACCbs]+) to 7.28 at 25 °C (ΔH = –88 ± 17 kJ mol−1 and ΔS = –434 ± 56 J K−1 mol−1) in [AC-5-seco-Cbs]+. The pKa, confirmed by determining the pH-dependence of coordination of SO32– by [AC-5-seco-Cbs]+, shows Co(III) in this complex behaves much more like Co(III) in simple hexacoordinate complexes than in intact cobalt Corrins. A comparison of log K values for coordination of CN–, SO32–, NO2–, N3– and S2O32– by [ACCbs]+ and [AC-5-seco-Cbs]+ demonstrates that cleavage of the corrin ring significantly decreases the affinity of Co(III) for the softer ligands CN–, SO32– and, more marginally, NO2–. However, [AC-5-seco-Cbs]+ has a higher affinity for N3– and S2O32– than [ACCbs]+. These trends correlate with the position of the ligands in the spectrochemical series (N3–
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Probing the Nature of the Co(III) Ion in Corrins: Comparison of Reactions of Aquacyanocobyrinic Acid Heptamethyl Ester and Aquacyano-Stable Yellow Cobyrinic Acid Hexamethyl Ester with Neutral N‑Donor Ligands
2013Co-Authors: Susan M. Chemaly, Monika Nowakowska, Louise Kendall, Dale Pon, Christopher B. Perry, Helder M. MarquesAbstract:Equilibrium constants (log K) for substitution of coordinated H2O in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, ACCbs) and aquacyano-stable yellow cobyrinic acid hexamethyl ester (aquacyano-stable yellow cobester, ACSYCbs), in which oxidation of the C5 carbon of the corrin interrupts the normal delocalized system of Corrins, by neutral N-donor ligands (ammonia, ethanolamine, 2-methoxyethylamine, N-methylimidazole, and 4-methylpyridine) have been determined spectrophotometrically as a function of temperature. Log K values increase with the basicity of the ligand, but a strong compensation effect between ΔH and ΔS values causes a leveling effect. The aliphatic amines with a harder donor atom produce ΔH values that are more negative in their reactions with ACSYCbs than with ACCbs, while the softer, aromatic N donors produce more negative ΔH values with ACCbs than with ACSYCbs. Molecular modeling (DFT, M06L/SVP, and a quantum theory of atoms in molecules analysis of the electron density) shows that complexes of the aliphatic amines with SYCbs produce shorter and stronger Co–N bonds with less ionic character than the Co–N bonds of these ligands with the cobester. Conversely, the Co–N bond to the aromatic N donors is shorter, stronger, and somewhat less ionic in the complexes of the cobester than in those of the SYCbs. Therefore, the distinction between the harder Co(III) in ACSYCbs and softer Co(III) in ACCbs, reported previously for anionic ligands, is maintained for neutral N-donor ligands
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Probing the nature of the Co(III) ion in Corrins: comparison of reactions of aquacyanocobyrinic acid heptamethyl ester and aquacyano-stable yellow cobyrinic acid hexamethyl ester with neutral N-donor ligands.
Inorganic chemistry, 2012Co-Authors: Susan M. Chemaly, Monika Nowakowska, Louise Kendall, Dale Pon, Christopher B. Perry, Helder M. MarquesAbstract:Equilibrium constants (log K) for substitution of coordinated H2O in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, ACCbs) and aquacyano-stable yellow cobyrinic acid hexamethyl ester (aquacyano-stable yellow cobester, ACSYCbs), in which oxidation of the C5 carbon of the corrin interrupts the normal delocalized system of Corrins, by neutral N-donor ligands (ammonia, ethanolamine, 2-methoxyethylamine, N-methylimidazole, and 4-methylpyridine) have been determined spectrophotometrically as a function of temperature. Log K values increase with the basicity of the ligand, but a strong compensation effect between ΔH and ΔS values causes a leveling effect. The aliphatic amines with a harder donor atom produce ΔH values that are more negative in their reactions with ACSYCbs than with ACCbs, while the softer, aromatic N donors produce more negative ΔH values with ACCbs than with ACSYCbs. Molecular modeling (DFT, M06L/SVP, and a quantum theory of atoms in molecules analysis of the electron density) sh...
Warren, Martin J. - One of the best experts on this subject based on the ideXlab platform.
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The requirement for cobalt in vitamin B12: A paradigm for protein metalation
'Elsevier BV', 2021Co-Authors: Osman Deenah, Deery Evelyne, Cooke Anastasia, Young, Tessa R., Robinson, Nigel J., Warren, Martin J.Abstract:Vitamin B12, cobalamin, is a cobalt-containing ring-contracted modified tetrapyrrole that represents one of the most complex small molecules made by nature. In prokaryotes it is utilised as a cofactor, coenzyme, light sensor and gene regulator yet has a restricted role in assisting only two enzymes within specific eukaryotes including mammals. This deployment disparity is reflected in another unique attribute of vitamin B12 in that its biosynthesis is limited to only certain prokaryotes, with synthesisers pivotal in establishing mutualistic microbial communities. The core component of cobalamin is the corrin macrocycle that acts as the main ligand for the cobalt. Within this review we investigate why cobalt is paired specifically with the corrin ring, how cobalt is inserted during the biosynthetic process, how cobalt is made available within the cell and explore the cellular control of cobalt and cobalamin levels. The partitioning of cobalt for cobalamin biosynthesis exemplifies how cells assist metalation
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Replacement of the Cobalt Center of Vitamin B 12 by Nickel: Nibalamin and Nibyric Acid Prepared from Metal‐Free B 12 Ligands Hydrogenobalamin and Hydrogenobyric Acid
'Wiley', 2020Co-Authors: Kieninger Christoph, Podewitz Maren, Wurst Klaus, Lawrence, Andrew D., Deery Evelyne, Liedl, Klaus R., Warren, Martin J., Stanley Maria, Kräutler BernhardAbstract:The (formal) replacement of Co in cobalamin (Cbl) by NiII generates nibalamin (Nibl), a new transition‐metal analogue of vitamin B12. Described here is Nibl, synthesized by incorporation of a NiII ion into the metal‐free B12 ligand hydrogenobalamin (Hbl), itself prepared from hydrogenobyric acid (Hby). The related NiII corrin nibyric acid (Niby) was similarly synthesized from Hby, the metal‐free cobyric acid ligand. The solution structures of Hbl, and Niby and Nibl, were characterized by spectroscopic studies. Hbl features two inner protons bound at N2 and N4 of the corrin ligand, as discovered in Hby. X‐ray analysis of Niby shows the structural adaptation of the corrin ligand to NiII ions and the coordination behavior of NiII. The diamagnetic Niby and Nibl, and corresponding isoelectronic CoI Corrins, were deduced to be isostructural. Nibl is a structural mimic of four‐coordinate base‐off Cbls, as verified by its ability to act as a strong inhibitor of bacterial adenosyltransferase
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Zinc substitution of cobalt in vitamin B12: Zincobyric acid and zincobalamin as luminescent structural B12‐mimics
'Wiley', 2019Co-Authors: Kieninger Christoph, Baker, Joseph A., Podewitz Maren, Wurst Klaus, Jockusch Steffen, Lawrence, Andrew D., Deery Evelyne, Gruber Karl, Liedl, Klaus R., Warren, Martin J.Abstract:Replacing the central cobalt ion of vitamin B12 by other metals has been a long‐held aspiration within the B12‐field. Herein, we describe the synthesis from hydrogenobyric acid of zincobyric acid (Znby) and zincobalamin (Znbl), the Zn‐analogues of the natural cobalt‐Corrins cobyric acid and vitamin B12, respectively. The solution structures of Znby and Znbl were studied by NMR‐spectroscopy. Single crystals of Znby were produced, providing the first X‐ray crystallographic structure of a zinc corrin. The structures of Znby and of computationally generated Znbl were found to resemble the corresponding CoII‐Corrins, making such Zn‐Corrins potentially useful for investigations of B12‐dependent processes. The singlet excited state of Znby had a short life‐time, limited by rapid intersystem crossing to the triplet state. Znby allowed the unprecedented observation of a corrin triplet (ET=190 kJ mol−1) and was found to be an excellent photo‐sensitizer for 1O2 (ΦΔ=0.70)
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Zinc Substitution of Cobalt in Vitamin B12: Zincobyric acid and Zincobalamin as Luminescent Structural B12-Mimics
'Wiley', 2019Co-Authors: Kieninger Christoph, Baker, Joseph A., Podewitz Maren, Wurst Klaus, Jockusch Steffen, Lawrence, Andrew D., Deery Evelyne, Gruber Karl, Liedl, Klaus R., Warren, Martin J.Abstract:Replacing the central cobalt ion of vitamin B12 by other metals has been a long‐held aspiration within the B12‐field. Herein, we describe the synthesis from hydrogenobyric acid of zincobyric acid (Znby) and zincobalamin (Znbl), the Zn‐analogues of the natural cobalt‐Corrins cobyric acid and vitamin B12, respectively. The solution structures of Znby and Znbl were studied by NMR‐spectroscopy. Single crystals of Znby were produced, providing the first X‐ray crystallographic structure of a zinc corrin. The structures of Znby and of computationally generated Znbl were found to resemble the corresponding CoII‐Corrins, making such Zn‐Corrins potentially useful for investigations of B12‐dependent processes. The singlet excited state of Znby had a short life‐time, limited by rapid intersystem crossing to the triplet state. Znby allowed the unprecedented observation of a corrin triplet (ET=190 kJ mol−1) and was found to be an excellent photo‐sensitizer for 1O2 (ΦΔ=0.70)
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Total Synthesis, Structure, and Biological Activity of Adenosylrhodibalamin, the Non‐Natural Rhodium Homologue of Coenzyme B12
'Wiley', 2016Co-Authors: Widner, Florian J., Wurst Klaus, Lawrence, Andrew D., Deery Evelyne, Gruber Karl, Warren, Martin J., Heldt Dana, Frank Stefanie, Kräutler BernhardAbstract:B12 is unique among the vitamins as it is biosynthesized only by certain prokaryotes. The complexity of its synthesis relates to its distinctive cobalt corrin structure, which is essential for B12 biochemistry and renders coenzyme B12 (AdoCbl) so intriguingly suitable for enzymatic radical reactions. However, why is cobalt so fit for its role in B12‐dependent enzymes? To address this question, we considered the substitution of cobalt in AdoCbl with rhodium to generate the rhodium analogue 5′‐deoxy‐5′‐adenosylrhodibalamin (AdoRbl). AdoRbl was prepared by de novo total synthesis involving both biological and chemical steps. AdoRbl was found to be inactive in vivo in microbial bioassays for methionine synthase and acted as an in vitro inhibitor of an AdoCbl‐dependent diol dehydratase. Solution NMR studies of AdoRbl revealed a structure similar to that of AdoCbl. However, the crystal structure of AdoRbl revealed a conspicuously better fit of the corrin ligand for RhIII than for CoIII, challenging the current views concerning the evolution of Corrins
Christopher B. Perry - One of the best experts on this subject based on the ideXlab platform.
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Probing the Nature of the Co(III) Ion in Corrins: Comparison of Reactions of Aquacyanocobyrinic Acid Heptamethyl Ester and Aquacyano-Stable Yellow Cobyrinic Acid Hexamethyl Ester with Neutral N‑Donor Ligands
2013Co-Authors: Susan M. Chemaly, Monika Nowakowska, Louise Kendall, Dale Pon, Christopher B. Perry, Helder M. MarquesAbstract:Equilibrium constants (log K) for substitution of coordinated H2O in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, ACCbs) and aquacyano-stable yellow cobyrinic acid hexamethyl ester (aquacyano-stable yellow cobester, ACSYCbs), in which oxidation of the C5 carbon of the corrin interrupts the normal delocalized system of Corrins, by neutral N-donor ligands (ammonia, ethanolamine, 2-methoxyethylamine, N-methylimidazole, and 4-methylpyridine) have been determined spectrophotometrically as a function of temperature. Log K values increase with the basicity of the ligand, but a strong compensation effect between ΔH and ΔS values causes a leveling effect. The aliphatic amines with a harder donor atom produce ΔH values that are more negative in their reactions with ACSYCbs than with ACCbs, while the softer, aromatic N donors produce more negative ΔH values with ACCbs than with ACSYCbs. Molecular modeling (DFT, M06L/SVP, and a quantum theory of atoms in molecules analysis of the electron density) shows that complexes of the aliphatic amines with SYCbs produce shorter and stronger Co–N bonds with less ionic character than the Co–N bonds of these ligands with the cobester. Conversely, the Co–N bond to the aromatic N donors is shorter, stronger, and somewhat less ionic in the complexes of the cobester than in those of the SYCbs. Therefore, the distinction between the harder Co(III) in ACSYCbs and softer Co(III) in ACCbs, reported previously for anionic ligands, is maintained for neutral N-donor ligands
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Probing the nature of the Co(III) ion in Corrins: comparison of reactions of aquacyanocobyrinic acid heptamethyl ester and aquacyano-stable yellow cobyrinic acid hexamethyl ester with neutral N-donor ligands.
Inorganic chemistry, 2012Co-Authors: Susan M. Chemaly, Monika Nowakowska, Louise Kendall, Dale Pon, Christopher B. Perry, Helder M. MarquesAbstract:Equilibrium constants (log K) for substitution of coordinated H2O in aquacyanocobyrinic acid heptamethyl ester (aquacyanocobester, ACCbs) and aquacyano-stable yellow cobyrinic acid hexamethyl ester (aquacyano-stable yellow cobester, ACSYCbs), in which oxidation of the C5 carbon of the corrin interrupts the normal delocalized system of Corrins, by neutral N-donor ligands (ammonia, ethanolamine, 2-methoxyethylamine, N-methylimidazole, and 4-methylpyridine) have been determined spectrophotometrically as a function of temperature. Log K values increase with the basicity of the ligand, but a strong compensation effect between ΔH and ΔS values causes a leveling effect. The aliphatic amines with a harder donor atom produce ΔH values that are more negative in their reactions with ACSYCbs than with ACCbs, while the softer, aromatic N donors produce more negative ΔH values with ACCbs than with ACSYCbs. Molecular modeling (DFT, M06L/SVP, and a quantum theory of atoms in molecules analysis of the electron density) sh...
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The cis influence of the corrin in vitamin B12 models
Chemical Physics Letters, 2012Co-Authors: Patrick Govender, Christopher B. Perry, Isabelle Navizet, Helder M. MarquesAbstract:Abstract Density Functional Theory (DFT) and Quantum Theory of Atoms in Molecules (QTAIM) calculations on [NH 3 [Co(III)(C10-X-corrin)]–CH 3 ] + , where the C10–H of corrin is replaced by electron-donating or –withdrawing groups, X, explore the cis influence in these vitamin B 12 models. As the electron donating ability of X increases, a normal trans influence is observed: the Co–NH 3 bond weakens while the Co–CH 3 bond strengthens. Surprisingly, though, the Co–CH 3 bond dissociation energy decreases monotonically as the Co–C bond strengthens. This is found to be a consequence of the extent of shortening of the Co–NH 3 during the homolysis reaction.
