Synthesis, Spectroscopic, and Electrochemical Properties of Three Tetranuclear Ruthenium(II) Polypyridyl Complexes Based on 4,5‐Diazafluorene

Abstract

AbstractThree tetrapodal ligands 1,2,4,5‐tetrakis[4‐(4,5‐diazafluoren‐9‐ylimino)phenoxymethyl]benzene (L1), 1,2,4,5‐tetrakis[2‐(4,5‐diazafluoren‐9‐ylimino)phenoxymethyl]benzene (L2), and 1,2,4,5‐tetrakis[(4,5‐diazafluoren‐9‐ylimino)methyl]benzene (L3), and their corresponding RuII polypyridyl complexes [{Ru(bpy)2}4(μ4‐L1–3)](PF6)8 (bpy = 2,2′‐bipyridine) were synthesized and characterized. The spectroscopic behavior of the three complexes was investigated by UV/Vis absorption and emission spectroscopy. They display metal‐to‐ligand charge transfer (MLCT) absorptions at around 443 nm in CH3CN solution at room temperature, and emission at around 575 nm in EtOH/MeOH (4:1, v/v) glassy matrix at 77 K. Electrochemical studies of the three complexes show one RuII‐based oxidation at around 1.35 V and three ligand‐based reductions.