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.