Analysis of superexchange coupling in metallocene-metallocenium redox pairs
Analysis of superexchange coupling in metallocene-metallocenium redox pairs
复制标题
茂金属-茂金属氧化还原对中的超交换耦合分析
DOI：
10.1021/j100159a039
复制
发表时间：
1991
期刊：
影响因子：
--
通讯作者：
E. Zhong
中科院分区：
文献类型：
--
作者：
M. Newton;K. Ohta;E. Zhong
Using a corresponding orbital approach implemented computational with the INDO method of Zerner et al, the authors have evaluated and analyzed the electron-transfer matrix elements (H{sub if}) for the ferrocene/ferrocenium and cobaltocene/cobaltocenium (Cp{sub 2}M/(Cp{sub 2}M){sup +}) electron exchange processes. Taking due account of the relative energies of different orientations of the reactants, they obtain good agreement with estimates of H{sub if} inferred from experimental kinetic data, as well as a detailed interpretation of the coupling based on a fully specified effective one-electron model. This model reveals distinct electronic mechanisms for the M = Fe and M = Co cases, corresponding, respectively, to superexchange of the 'electron' and 'hole' type. Variationally defined effective donor and acceptor orbitals are shown to be essentially equivalent to appropriately selected canonical molecular orbitals of the Cp{sub 2}M/(Cp{sub 2}M){sup +} transition-state complex. Departures from a simple one-electron model affect the calculated H{sub if} values by less than 10% (i.e., the many-electron core overlap integral is {approx gt} 0.9) even though the wave functions properly reflect the appreciable degree of electronic relaxation which is known to accompany the oxidation of the Cp{sub 2}M molecules. {sigma} as well as {pi}-type orbitals of the Cp rings are shown tomore » play a significant role in facilitating the electronic coupling between reactants.« less
Using a corresponding orbital approach implemented computational with the INDO method of Zerner et al, the authors have evaluated and analyzed the electron-transfer matrix elements (H{sub if}) for the ferrocene/ferrocenium and cobaltocene/cobaltocenium (Cp{sub 2}M/(Cp{sub 2}M){sup +}) electron exchange processes. Taking due account of the relative energies of different orientations of the reactants, they obtain good agreement with estimates of H{sub if} inferred from experimental kinetic data, as well as a detailed interpretation of the coupling based on a fully specified effective one-electron model. This model reveals distinct electronic mechanisms for the M = Fe and M = Co cases, corresponding, respectively, to superexchange of the 'electron' and 'hole' type. Variationally defined effective donor and acceptor orbitals are shown to be essentially equivalent to appropriately selected canonical molecular orbitals of the Cp{sub 2}M/(Cp{sub 2}M){sup +} transition-state complex. Departures from a simple one-electron model affect the calculated H{sub if} values by less than 10% (i.e., the many-electron core overlap integral is {approx gt} 0.9) even though the wave functions properly reflect the appreciable degree of electronic relaxation which is known to accompany the oxidation of the Cp{sub 2}M molecules. {sigma} as well as {pi}-type orbitals of the Cp rings are shown tomore » play a significant role in facilitating the electronic coupling between reactants.« less