Tuning of the Reorganization Energies by Innocent Co-ligands in Novel Mixed-Valent Dinuclear Ruthenium Complexes

GARCÍA POSSE, MÓNICA E.; VERGARA, MÓNICA M.; FAGALDE, FLORENCIA; KATZ, NÉSTOR E.

POLYHEDRON

Elsevier Science Ltd.

Lugar: Amsterdam; Año: 2003 vol. 22 p. 465 - 471

0277-5387

Two novel mixed-valent ruthenium complexes, of formulae [(tpy)(bpy)RuII(pz)RuIII(edta)]+ and [(CN)4RuII(bpz)RuIII(edta)]3- (where tpy = 2,2':6',2"-terpyridine, bpy = 2,2'-bipyridine, pz = pyrazine, bpz = 2,2'-bipyrazine, edta = ethylenediaminetetraacetate)   , were prepared and spectroscopically characterized in aqueous solutions and as solid salts with suitable counterions.  For comparison purposes, two new ruthenium complexes:  a dinuclear species, of formula [(CN)4RuII(bpz)RuII(NH3)5] , and a trinuclear species, of formula {(CN)4RuII(bpz)[RuII(NH3)5]2}2+  , were also prepared and characterized in aqueous solutions. From spectral data of metal-to-metal charge transfer absorption bands, a Hush analysis was made, and the reorganization energies for the intramolecular electron transfers were calculated. A dramatic change in these values was disclosed when comparing both mixed-valent species, which can be explained on the basis of the influence exerted by the innocent co-ligands  (polypyridines or cyanides) bonded  to the ruthenium centers. This tuning is an important factor in devising molecular devices for energy conversion.