New Asymmetric N-heterocyclic-bridged Mixed-Valent Dinuclear Complexes of Rhenium and Ruthenium

MELLACE, MARÍA G.; FAGALDE, FLORENCIA; KATZ, NÉSTOR E.

POLYHEDRON

Elsevier Science Ltd.

Lugar: Amsterdam; Año: 2003 vol. 22 p. 369 - 374

0277-5387

Two new mixed-metal mixed-valent complexes, of formulae: [(CO)3(bpy)ReI(bpe)RuIII(NH3)5]4+ and [(CO)3(bpy)ReI(4-CNpy)RuIII(NH3)5]4+ (where bpy=/2,2?-bipyridine, bpe =/trans -1,2-bis(4-pyridil)ethene, 4-CNpy=/4-cyanopyridine), were prepared and characterized as solids and in acetonitrile solutions. From their spectroscopic, electrochemical and photophysical properties, the values for the reorganization energies l and electronic coupling elements HAB for the metal-to-metal intramolecular electron transfers mediated by the N-heterocyclic bridges were calculated, using the Marcus-Hush formalism. For the 4-CNpy derivative, the reverse ruthenium-to-rhenium charge recombination -/that should follow light excitation -/is expected to be in the normal region, while for the bpe derivative this reaction is predicted to lie in the inverted region. The differences in redox potentials and in l for both species account for these changes, which are relevant in the design of efficient photoconverters.