Hetero-and homo-leptic Ru(II) catalyzed synthesis of cyclic carbonates from CO₂; synthesis, spectroscopic characterization and electrochemical properties

Based on the a ligand BDPPZ [(9a,13a-dihydro-4,5,9,14-tetraaza-benzo[b] triphenylene-11-yl)-phenyl-methanone] (1) and its polypyridyl hetero- and homoleptic Ru(II) metal complexes, [Ru(bpy)₂L](PF₆) ₂ (2), [Ru(phen)₂L](PF₆)₂ (3), [Ru(dafo)₂L](PF₆)₂ (4), [Ru(dcbpy) ₂L](PF₆)₂ (5) and [RuL₃](PF ₆)₂ (6) (where, L = ligand, bpy = 2,2'-bipyridine, phen = 1,10-phenantroline, dafo = 4,5-diazafluoren-9-one and dcbpy = 3,3'-dicarboxy-2,2'-bipyridine), have been synthesized and characterized by elemental analysis, UV-vis, FT-IR, ¹H and ¹³C-NMR spectra (for ligand), molar conductivity measurements and X-ray powder techniques. The electrochemical parameters of the substituted ligand and its polypyridyl hetero- and homoleptic Ru(II) metal complexes are reported by cyclic voltammetry.UV-vis spectroscopy is used to compare the differences between the conjugated π systems in this ligand and its Ru(II) metal complexes. The polypyridyl hetero- and homoleptic Ru(II) metal complexes also tested as catalysts for the formation of cyclic organic carbonates from carbon dioxide and liquid epoxides which served as both reactant and solvent. The results showed that the [Ru(L) ₃](PF₆)₂ (6) complex is more efficient than the other Ru(II) complexes for the formation of cyclic organic carbonates from carbon dioxide.