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

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-buiyl, 4,4′-di-/e/7-butyl-2,2′-bipyridine, tbbpy, X = CI^- 3; Hjbibzim = l,l′-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]₂ 6 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.