Electron-, Proton- and Photon-Induced Spectroscopic Changes in Chromophore-Quencher Tricarbonyl(2,2’-bipyridine)rhenium(I) Complexes with 4,4’-azobis(pyridine)

POURRIEUX, GASTON; FAGALDE, FLORENCIA; ROMERO, ISABEL; FONTRODONA, XAVIER; PARELLA, TEODOR; KATZ, NÉSTOR E.

INORGANIC CHEMISTRY

AMER CHEMICAL SOC

Lugar: Washington, DC; Año: 2010 vol. 49 p. 4084 - 4091

0020-1669

We report in this work the synthesis and characterization of new mono- and dinuclear complexes of formulae: [Re(bpy)(CO)3(4,4’-azpy)](CF3SO3), 1  (bpy = 2,2’-bipyridine, 4,4’-azpy = 4,4’-azobis(pyridine));  [(bpy)(CO)3Re(4,4’-azpy)Ru(NH3)5](PF6)3. CH3CN.6H2O, 2 and the mixed-valent species [(bpy)(CO)3Re(4,4’-azpy)Ru(NH3)5]4+ , 3  (obtained in situ by electrochemical oxidation of 2). The molecular structure of 1 has been determined by X-ray diffraction. We also report the effect of controlled potential electrolysis, protonation and light excitation over the absorption and emission properties of these complexes, and their possible application as “molecular switches”. In particular, complex 1, which is almost non-emissive at room temperature, recovers luminescence either by reduction of coordinated 4,4’-azpy or by trans- to cis-photoisomerization. The detected emission of 1 at 77 K is due to decay from a Re® bpy MLCT excited state. TDDFT calculations support the interpretation of the photophysical changes induced by external stimuli.