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Non-Innocence of 1,4-Dicyanamidobenzene Bridging Ligands in Dinuclear Ruthenium Complexes.

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journal contribution
posted on 18.02.2016, 17:38 by Mohommad M. R. Choudhuri, Wolfgang Kaim, Biprajit Sarkar, Robert J. Crutchley
Four dinuclear complexes, [{RuII(ttpy)­(bpy)}2(μ-L)]­[PF6]2, where bpy is 2,2′-bipyridine, ttpy is 4-(tert-butylphenyl)-2,2′:6′,2″-terpyridine, and L is 2,5-dimethyl-, 2,5-dichloro-, 2,3,4,5-tetrachloro- and unsubstituted 1,4-dicyanamidebenzene dianion have been synthesized and characterized. Electron paramagnetic resonance (EPR) spectroscopy of electrogenerated [{Ru­(ttpy)­(bpy)}2(μ-L)]3+ ions shows largely ligand centered spin and thus the complexes’ oxidation states are best formulated as [Ru­(II), L•–, Ru­(II)]3+. Visible-NIR and IR spectra of [{Ru­(ttpy)­(bpy)}2(μ-L)]3+,4+ ions were also obtained by spectroelectrochemical methods. For the [{Ru­(ttpy)­(bpy)}2(μ-L)]3+ ions, the significant variations in the spectra were rationalized in terms of an increased ruthenium contribution to the singly occupied molecular orbital with increasing number of chloro substituents on the bridging ligand L.