Zeolite-based organized molecular assemblies. Photophysical characterization and documentation of donor oxidation upon photosensitized charge separation

An organized molecular assembly composed of two ruthenium polypyridine comp lexes, Ru(bpy)(2)(bpz)(2+) and Ru(bPY)(2)(H2O)(2) (2+) (where bpy = 2,2 ' - bipyridine and bpz = 2, 2 ' -bipyrazine), has been prepared in adjacent sup ercages of Y-zeolite. This material has been characterized by diffuse refle ctance, electronic absorption, electronic emission, and resonance Raman (RR ) spectroscopy, as well as lifetime measurements. The spectral results conf irm the identity of the entrapped complexes and resonance Raman measurement s show that the relative concentrations of the two complexes within the zeo lite particles are identical. A dramatic decrease in emission intensity obs erved for the adjacent cage assembly, relative to that observed for an appr opriate reference material composed of a mixture of zeolite particles conta ining the separated complexes, indicates strong interaction between the adj acent complexes which provides an additional nonradiative decay pathway. Th e excited state lifetime measurements implicate a very short-lived componen t, dominating the decay curve at early times, which is most reasonably attr ibuted to excited-state electron-transfer quenching of the adjacent cage pa ir. More importantly, analysis of diffuse reflectance spectra acquired duri ng selective (sensitizer) irradiation of a sample of this material, wherein the remaining cages are filled with a suitable acceptor (MV2+), provides d irect evidence for oxidation of the Ru(bpy)(2)(H2O)(2)(2+) donor complex, c onfirming the targeted synergy of the adjacent cage assembly.