Spectroscopic, electrochemical and computational studies of rhenium(I) and ruthenium(II) complexes incorporating the novel tetradentate ligand 1,4-bis(4-(4′-methyl)-2,2′-bipyridyl)-2,3-diaza-1,3-butadiene (BBDB) and its derivatives

The novel tetradentate ligand 1,4-bis(4-(4′-methyl)-2,2′-bipyridyl)-2,3-diaza-1,3-butadiene (BBDB) was synthesized and characterized by spectroscopic techniques. New complexes of Re and Ru of formulae: [Re(BBDB)(CO)3(Cl)], [(CH3CN)(CO)3Re(μ-BBDB)Re–(CO)3(CH3CN)]2+, [(bpy)2Ru-(μ-BBDB)Ru(bpy)2]4+, [(NH3)4Ru(μ-BBDB)–Ru(NH3)4]4+ (bpy = 2,2′-bipyridine) and complexes of Ru with 4-Me-4′-CO2H-bpy (=4-methyl-4′-carboxylic acid-2,2′-bipyridine) – the hydrolyzed derivative of BBDB – of formulae: [(Ru(4-Me-4′-CO2H-bpy)(bpy)2]2+ and [Ru(4-Me-4′-CO2H-bpy)(CN)4]2− were prepared and characterized by spectroscopic, electrochemical and computational techniques. The disclosed enhanced electronic coupling in the mixed-valent complex with ruthenium ammines can be explained by the electronic delocalization imposed by the CNNC backbone. DFT and TD-DFT calculations can predict the optical properties and electronic structures of the reported complexes and comparisons with calculations performed on previously reported complexes with 4-pyridinaldazine can account for their photophysical behaviour.

Graphical abstractA new bridging ligand, 1,4-bis(4-(4′-methyl)-2,2′-bipyridyl)-2,3-diaza-1,3-butadiene (BBDB), and novel complexes of rhenium tricarbonyls, ruthenium polypyridines and ruthenium ammines containing BBDB and its hydrolysis derivatives have been synthetized and characterized by spectroscopic, electrochemical and computational techniques.Figure optionsDownload full-size imageDownload as PowerPoint slide