| Research Abstract |
The photochemical and photophysical properties of tris(bipyridine)ruthenium(II) containing vinyl polymer 1 have been studied. The luminescence properties of 1 showed the close resemblance to its component monomer 2, that is, 4,4'-dimethyl-2,2'-bipyridine-bis(bipyridine)ruthenium(II) complex. In contrast to polyvinylaromatics, there was no evidence for the energy migration and electron exchange between ruthenium complexes on the polymer chain. In order to gain a better understanding of events which take place in the polymer, it is necessary to work on tris(bipyridine)ruthenium complex dimer.
Covalently linked dimers of Ru(bpy)_3 ^<2+> (3 and 4) were synthesized as a model for Ru(byp)_3 ^<2+>-containing vinyl polymer (1). The luminescence properties of 3 and 4 were compared with those of 2. In excited 3 and 4, the intramolecular interaction leading to the enhanced quenching was not observed. The electron transfer quenching of the excited dimer with methyl viologen (MV^<2+>) and the zwitte
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rionic viologen, 1,1'-bis(3-sulfopropyl)-4,4'-bipyridinium (SPV) was studied and compared with those of 1 and 2. The low quenching efficiency in 1, 3, and 4 systems can be ascribed to the steric hindrance of unexcited ruthenium complex. Energy migration between ruthenium complexes in the excited 1, 3, and 4 can be ruled out from the kinetical evidence.
We have found a rather different photophysical behavior of 1, 3, and 4 in comparison with those of aromatic hydrocarbon- and porphyrin-dimers. In excited 1, the intramolecular interaction leading to the enhanced quenching between the excited and ground states was not found. However, the efficient intramolecular triplettriplet annihilation process was found under the high intensity irradiation of laser light. These findings aroused our interest in the heterobinuclear system. We synthesized novel polypyridine-ruthenium(II) and -osmium(II) heterobinuclear complexes 5, Ru(II)bpy_2Mebpy-(CH_2)_n-MebpyOs(II)bpy_2 (n=2,3,5), and studied their luminescence preperties. The luminescence properties of 5 were compared with those of its component complex. In 5, the efficient intramolecular energy transfer from excited Ru(II) to Os(II) complex was observed and interpreted by Foerster mechanism. Less
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