He Felix M C, Bernhardt Paul V
School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, 4072, Australia.
J Biol Inorg Chem. 2017 Jul;22(5):775-788. doi: 10.1007/s00775-016-1427-y. Epub 2016 Dec 28.
A selection of cobalt (III)/(II) macrobicyclic 'sarcophagine' (sar) cage complexes with NS mixed donor sets but differing in a single apical substituent has been chosen to span a redox potential range of +150 to -150 mV vs the normal hydrogen electrode and thus acts as redox buffers in protein spectroelectrochemistry and redox potentiometry. The cobalt(III) cage complexes are all based on the same parent structure [Co(XMeNSsar)], where X, the variable apical substituent, is -NO, -Cl, -OH, -NH or -NMe , and a methyl group occupies the opposite apical position. The X-ray crystal structures of selected members of this series are reported. Changes to the apical substituent X enable the Co redox potential to be tuned across a range of more than 200 mV by the inductive effects of the functional group. The pH dependence of the redox potential enabled the pK values of some functional groups to be determined. The complexes were successfully employed as electron transfer mediators in the spectroelectrochemical investigation of a variety of heme proteins.
已选择一系列钴（III）/（II）大环“肌氨酰”（sar）笼状配合物，其具有氮硫混合供体基团，但单个顶端取代基不同，相对于标准氢电极，其氧化还原电位范围为 +150 至 -150 mV，因此在蛋白质光谱电化学和氧化还原电位测定中充当氧化还原缓冲剂。钴（III）笼状配合物均基于相同的母体结构 [Co(XMeNSsar)]，其中可变的顶端取代基 X 为 -NO、-Cl、-OH、-NH 或 -NMe ，且一个甲基占据相对的顶端位置。报道了该系列中选定成员的 X 射线晶体结构。顶端取代基 X 的变化可通过官能团的诱导效应使钴的氧化还原电位在超过 200 mV 的范围内进行调节。氧化还原电位对 pH 的依赖性使得能够确定一些官能团的 pK 值。这些配合物在多种血红素蛋白的光谱电化学研究中成功用作电子转移介质。
