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Abstract

There is an intense interest in designing molecular systems which will absorb visible sunlight, initiate an electron transfer process, and ultimately convert the solar energy to useful chemical energy of fuels such as hydrogen produced from water. The zeolite-entrapped polypyridine complexes of divalent ruthenium hold promise as efficient photocatalysts for net charge separation and such efficiencies are further enhanced by organized incorporation of donor and acceptor components. This paper deals with the synthesis and spectroscopic investigation of zeolite-entrapped ruthenium polypyridine complexes which may be useful in the development of solar energy conversion schemes. The sensitizer molecules, such as Ru(bpy)3 2+ (bpy = 2,2-bipyridine), are entrapped within the supercages of structurally well-defined zeolite Y by the so called "ship in a bottle" synthesis, which eliminates the undesirable diffusion of the complex and inhibits the wasteful back-electron transfer reaction. This complex has a dimension of ~12A, which is too large to introduce through a 7.4 A window opening. Once the complex is formed in the supercage, it cannot escape through the windows and is effectively entrapped within the supercage. The zeolite-entrapped ruthenium complexes are characterized by diffuse reflectance, electronic absorption, electronic emission, and resonance Raman (RR) spectroscopy, as well as excited state lifetime measurements. A brief summary of the synthetic and characterization procedure of the zeolite-entrapped ruthenium polypyridine complexes is presented here. Emphasis is given on the author's work, although a discussion of some of the important contributions made by other workers is also included. This study clearly demonstrates that entrapment of ruthenium complex within the supercage of Y-zeolite can alter inherent photophysical properties of the complex in an advantageous manner.

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