{(mu-L)[Ru-II(acac)(2)](2)}'', n = 2+, +, 0, -, 2-, with L=3,3 ', 4,4 '-tetraimino-3,3 ',4,4 '-tetrahydrobiphenyl. EPR- supported assignment of NIR absorptions for the paramagnetic intermediates

Abstract

A complete EPR and UV-Vis-NIR spectroelectrochemical characterisation has been carried out for the series 1(2+/+/0/-/2-) where 1 is the new complex {(mu-L)[Ru-II(acac)(2)](2)}, L = 3,3',4,4'-tetraimino-3,3',4,4'-tetrahydrobiphenyl. The paramagnetic intermediates are identified as the anion radical (L.-) complex 1(.-) with a long-wavelength intra-ligand transition at 2160 nm and as the weakly coupled diruthenium(II,III) species 1(.-) (K-c = 10(3)) with a low-intensity intervalence charge transfer (IVCT) band at 1570 nm. DFT calculations using ADF and Gaussian 03 programs support these assignments.