Multi-Center Redox-Active System: Amine–Amine Electronic Coupling through a Cyclometalated Bisruthenium Segment

A multicenter redox-active
system with a linear N–Ru–Ru–N
array, where two distal triarylamine sites are bridged by a cyclometalated
bisruthenium segment, has been synthesized and characterized with
single-crystal X-ray analysis. This system displays four consecutive
and separate anodic redox waves at low potentials, indicating the
presence of amine–amine electronic coupling with a distance
of 19.16 Å through the cyclometalated bisruthenium segment. In
contrast, when a noncyclometalated bisruthenium bridge is used, no
amine–amine coupling is present. Upon stepwise oxidation by
chemical or electrochemical methods, four-step absorption spectral
changes occur in the visible to near-infrared region. In addition,
the EPR studies and DFT and TDDFT calculations of the singly oxidized
state are presented.

本研究合成了一种具有线性N–Ru–Ru–N阵列结构的多中心氧化还原活性体系，该体系的两个远端三芳胺位点由环金属化双钌片段桥联，并通过单晶X射线分析对其进行了结构表征。该体系在低电位区间展现出四个连续且独立的阳极氧化还原峰，表明通过环金属化双钌片段可实现间距为19.16 Å的三芳胺之间的电子耦合作用。与之相对，当采用非环金属化双钌桥联结构时，则未观察到三芳胺间的电子耦合现象。通过化学或电化学方法进行逐步氧化时，该体系在可见光至近红外区域呈现出四阶段的吸收光谱变化。此外，本文还报道了单氧化态下的电子顺磁共振（EPR）研究以及密度泛函理论（DFT）和含时密度泛函理论（TDDFT）的计算结果。