Date of Award

1986

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Abstract

Stern-Volmer plots for the quenching of luminescence and for the photosubstitution reaction of tris-bipyridylruthenium(II) at 298 K were obtained. The two Stern-Volmer plots were found to be similar; this result is different from that of a previous report, but it agrees well with a general model postulated to represent the photophysical processes of the excited states of polypyridine ruthenium(II) complexes. The temperature dependence of the emission intensities and of the lifetimes of tris-bipyridylruthenium(II), cis-ibspyridyl bis-2,2'bipyridylruthenium(II), and 4,5-diazafluorenyl-bis-2,2'bipyridylruthenium(II) were reinvestigated in order to evaluate the difference in energy between the triplet metal to ligand charge transfer and ligand field excited states. The activation energies of these complexes were found to be well correlated with the respective ligand field strengths. The 77 K emission properties and the temperature dependence of the emission intensities of two series of polypyridine ruthenium(II) complexes Ru(bipy)(,2)L ('+2) were examined. Their photochemistries at 298 K were also investigated. The main goal was to determine the effect of chelate ring size on their photosubstitution reactions in different solvents. The first series included methylene-linked pyridine ligands, and the second involved methylene-linked diamine ligands. In the case of the pyridine series there was an increase in quantum yield of the photosubstitution reactions as the chelate ring size increased. In contrast, significantly lower quantum yields were observed for complexes of the diamine series in which the two chelating N atoms of the bidentate ligands do not belong to an aromatic ring. It was also established that the Ag('+)cation has a catalytic effect on the photosubstitution reaction of the complex ethylenediamine bis-2,2'bipyridylruthenium(II) dissolved in CH(,3)CN. Results of the photolyses of this complex and of 1,3-propylenediamine bis-2,2'bipyridylruthenium(II) suggested that under certain conditions oxidation of the methylene-linked ligand occurs. The temperature dependence of the quantum yields of the photosubstitution reactions of these complexes in 0.01 M tetraethylammoniumchloride solutions in CH(,2)Cl(,2) showed small apparent activation energies.

Pages

357

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