Antibacterial and luminescent properties of new donor–acceptor ruthenium triphenylphosphine–bipyridinium complexes

The known compounds N-(2,4-dinitrophenyl)-4,4′-bipyridinium (2,4-DNPhQ+), N-phenyl-4,4′-bipyridinium (PhQ+) and N-(4-acetylphenyl)-4,4′-bipyridinium (4-AcPhQ+) have been used to prepare a series of ruthenium complexes of the type [RuCl(CO)(PPh3)2(L)] (where, L = 2,4-DNPhQ+ or PhQ+ or 4-AcPhQ+). The latter complexes reacted with sulphur derivative to give [RuCl(CO)(PPh3)2(L)(L′)] (where, L′ = thio-9-xanthone). These new ruthenium complexes display intense, visible metal-to-ligand charge-transfer (MLCT) absorptions, due to dπ(Ru) → π*(pyridinium) excitations. The MLCT energy decreases as the acceptor strength increases in the order PhQ+ < 4-AcPhQ+ < 2,4-DNPhQ+. The new ruthenium complexes have been characterized by using standard analytical and spectroscopic techniques. Fluorescence and antibacterial activity of the ligands and appropriate complexes has also been carried out.