MODULATION OF VISIBLE ABSORPTION PROPERTIES IN NEW RUTHENIUM POLYPYRIDYL COMPLEXES BY INTRODUCING MIXED LIGANDS WITH STRONG ELECTRON DONOR AND STRONG ELECTRON ACCEPTOR GROUPS

CATTANEO, MAURICIO; KATZ, NÉSTOR E.; FAGALDE, FLORENCIA

Puerto Iguazú, Misiones

Simposio; 6th Latin American Symposium on Coordination and Organometallic Chemistry; 2017

CONICET-AvH Foundation

Two new ruthenium complexes, containing 2,2´- bipyridines with substituents of very different electron accepting abilities, of formula [Ru(4,4´-dmobpy)2(4,4´-dcabpy)]2+ (1) and [Ru(4,4´-dmobpy)(4,4´-dcabpy)2]2+ (2), where 4,4´-dmobpy = 4,4´-dimethoxy-2,2´-bipyridine and 4,4´-dcabpy = 2,2´-bipyridine-4,4´-dicarboxylic acid, were synthesized as PF6- salts and characterized by spectroscopic, electrochemical and photophysical techniques. In both complexes, two intense bands are observed in the visible region, which can be assigned to MLCT transitions d(Ru) → pi*(4,4´-dmobpy) and d(Ru) → pi*(4,4´-dcabpy), the latter being the lowest energy one, as expected from the strong electron accepting properties of 4,4´-dcabpy. The energy separation between both bands is higher in (1) than in (2), due to the introduction of a higher number of electron donor ligands (4,4´-dmobpy) in the former species. Base titration of the carboxylic acid groups by absorption and emission measurements shows that the excited states are stronger bases than the ground states in (1). Respect to similar complexes previously reported, further absorption and emission into the NIR is disclosed, since the energy of the lowest-lying LUMO levels decreases when introducing strong electron donor substituents in the non-protonable bipyridyl ligands. These spectral changes are relevant to improve the performance of dye-sensitized solar cells.