Water Oxidation by Mononuclear Ruthenium Complex with a Pentadentate Isoquinoline–Bipyridyl Ligand

Mononuclear ruthenium complexes with a pentadentate ligand, N , N ‐bis[(isoquinolin‐1‐yl)methyl][6‐(pyridin‐2‐yl)pyridin‐2‐yl]methanamine (DIQ‐Bpy), were synthesized and characterized by 1 H NMR spectroscopy, elemental analysis, electrochemistry, and theoretical calculations. The oxidation of water by [Ru(DIQ‐Bpy)(H 2 O)] 2+ was observed in the presence of excess amounts of Ce IV . Relative to [Ru(DPA‐Bpy)(H 2 O)] 2+ [DPA‐Bpy = N , N ‐bis(2‐pyridinylmethyl)‐2,2′‐bipyridine‐6‐methanamine], the substitution of pyridine groups in DPA‐Bpy with electron‐withdrawing isoquinolines results in higher redox potential and lower activity for the oxidation of water by [Ru(DIQ‐Bpy)(H 2 O)] 2+ . A kinetic study of water oxidation by [Ru(DPA‐Bpy)(H 2 O)] 2+ suggests a mononuclear pathway for the oxidation of water. The noncovalent interaction between isoquinoline groups in [Ru(DIQ‐Bpy)(H 2 O)] 2+ , which favors the formation of dinuclear species, might account for the lower activity for water oxidation by [Ru(DIQ‐Bpy)(H 2 O)] 2+ .