Bis(R-bipyridyl)ruthenium bibenzimidazole complexes (R = H, Me or But ): supramolecular arrangement via hydrogen bonds, photo- and electro-chemical properties and reactivity towards carbon dioxide

Abstract

Complexes of the type [Ru(H2bibzim)(R-bpy)2X2·nH2O (R = H, 2,2′-bipyridine, bpy, X = CF3SO3−1; R = Me, 4,4′-dimethyl-2,2′-bipyridine, dmbpy, X = PF6−2; R = tert-butyl, 4,4′-di-tert-butyl-2,2′-bipyridine, tbbpy, X = Cl−3; H2bibzim = 1,1′-bibenzimidazole) containing two NH functions acting as hydrogen bond donors formed different spatially highly organised supramolecular assemblies with water. X-Ray investigation revealed that the nature of the counter ion influences the hydrogen bonding pattern and extent of spatial organisation. In 2 one dimensional chains of hydrogen bonded water could be found. In the deprotonated complex [Ru(bibzim)(tbbpy)2] 4 water molecules serve as hydrogen bond donors. The diastereomeric forms 5a/5b of the homodinuclear ruthenium complex [{Ru(tbbpy)2}2(bibzim)][PF6]2 could be separated. No differences in their photophysical properties could be detected. The X-ray investigation of 5a and [{Ru(bpy)2}2(bibzim)][PF6]26 showed little influence of peripheral substitution on structural properties. Complexes 3–5 exhibit activity in electrochemical CO2 reduction which can be tuned by variation of the degree of protonation of the bibenzimidazole.