The new isocyanide complexes Ru(bpy)2(CN)(CNMe)+, Ru(bpy)2(CNMe)22+, and Ru(bpy)(CNMe)42+have been synthesized, and their photophysical and redox behavior has been studied in detail. With respect to the cyanide analogues, the strong electron-withdrawing effect of the methyl isocyanide ligands causes (i) large blue shifts in the Ru-> bpy MLCT transitions and (ii) large anodic shifts in the potentials for oxidation of Ru(II). The excited-state behavior of Ru(bpy)(CNMe)42+appears quite exceptional with respect to that of common Ru(II) bipyridine complexes. In fact (i) its lowest excited state is a long lived (τ = 8.8 μs in water at 298 K) bpy-centered π-π* state and (ii) the complex is a strong excited-state oxidant (E1/2(*Ru(III)/Ru(II)) = +1.49 V vs SCE in MeCN). This constitutes a rather extreme example of tuning of excited-state properties by nonchromophoric ligands.
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Indelli et al. (1988) studied this question.