Tris(2,2'-bipyridine)ruthenium(II) complexes, Ru(bpy)32+, were covalently linked to viologen units to afford a model of man-made photoreaction centers. The emission from the ruthenium complex in the photoreaction centers was almost completely quenched by the linked viologen units. The relative quantum yields ( " ) of the photoinduced reduction of viologen units in the presence of the electron donor EDTA were 1-2% of those for the free Ru(bpy)32+-methyl viologen system in aqueous solutions. The ß values, however, remarkably increased in the combined system which consisted of the photoreaction center and the electron relay systems of aligned viologen units (micelle, polymer, and polysoap). The effect was attributed to the enhancement of charge separation of the photoproduced primary ion pair due to electron injection from the photoreaction centers into the electron relay system and the succeeding electron migration.

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The reaction between viologen polymer radicals(PV\underset.+) and Ru(NH3)63+ via zwitterionic viologen as excellent mediator, has been studied using the pulse radiolysis technique. Kinetic analysis provided quantitative measurement of the rate of electron transfer between the viologen radicals of zwitterionic viologens and PV2+ and vice versa. These also allowed determination of the redox potential of the polymer system. Implications to the photochemical charge separation system are discussed.

Photoinduced electron transfer from excited tris(2,2'-bipyridine)ruthenium(II) complex, Ru(bpy)?+, to viologen polymer via zwitterionic viologen (ZV), as an electron mediator, was investigated by the use. of three violcgen polymers and two zwitterionic viologens. The quantum yields of reduced viologen (I#++.) in the presence of triethanolamine (TEOA) were strongly affected by the structure of the zwitterionic viologens. The lifetime of photoreduced viologen, as observed in flash photolysis, was extended up to 1.2 s. All of the reduced zwitterionic viologen (ZV--), which excaped from primary cage recombination, was perfectly trapped by the viologen polymer and extremely long-lived reduced viologens were generated by the electron transfer from ZV-. to the viologen polymer. Argonne National Laboratory, for discussions. A Grant-in-Aid TEOA.The overtone absorption spectrum of propylene in the region 10 300-19 900 cm-' is analyzed in terms of local-mode (LM) stretching excitations centered on individual C-H bonds. A molecular-orbital analysis suggests that *-orbital delocalization is responsible for the appearance of two methyl C-H absorption bands at each overtone and that a-framework orbitals are responsible for the terminal olefinic C-H splitting. Calculated C-H potential energy binding curves are consistent with the five-peak absorption spectrum even if the rotational conformation of the methyl group is not rigidly fixed.

Viologen polymers were successfully used to collect photoliberated electron from polypyridineruthenium(II) complexes by the use of a zwitterionic viologen as an electron mediator. The collected electrons were successively trapped by platinum colloid supported on the viologen polymers. The viologen polymer thus proved to be an efficient electron transporting system from photoredox reaction center to multi-electron redox catalyst for chemical solar energy conversion.