Spectroscopic, electrochemical and computational studies of rhenium(I) and ruthenium(II) complexes incorporating the novel tetradentate ligand 1,4-bis(4-(40-methyl)-2,20-bipyridyl)-2,3-diaza-1,3-butadiene (BBDB) and its derivatives

摘要

The novel tetradentate ligand 1,4-bis(4-(40-methyl)-2,20-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)], [(CH_3CN)(CO)3Re(μ-BBDB)Re-(CO)_3(CH_3CN)]~(2+), [(bpy)_2Ru-(μ-BBDB)Ru(bpy)_2]~(4+), [(NH_3)_4Ru(μ-BBDB)-Ru(NH_3)_4]~(4+) (bpy = 2,20-bipyridine) and complexes of Ru with 4-Me-40-CO_2H-bpy (=4-methyl-40-carboxylic acid-2,20-bipyridine)-the hydrolyzed derivative of BBDB-of formulae: [(Ru(4-Me-40-CO_2H-bpy)(bpy)_2]~(2+) and [Ru(4-Me-40-CO_2H-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 -C=NAN=C- 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.