Photochemical and photophysical studies of some copper(I) and ruthenium(II) systems
Abstract
Solutions of Cu(dmp)$\sb2\sp{+}$ (dmp = 2,9-dimethyl-1,10-phenanthroline) in methylene chloride were observed to bleach upon exposure to high intensity 354.7 nm pulsed-laser irradiation. The intensity dependence of the observed bleaching indicates a biphotonic process in which the second photon is absorbed by a relatively long-lived charge transfer to ligand excited state. Cu(dmp)$\sb2\sp{2+}$ and Cl$\sp{-}$ are formed with 1:1 stoichiometry as a result of an outer-sphere electron transfer reaction between a high-lying excited state of the complex and a methylene chloride molecule that is presumably located in the secondary solvation shell. Bleaching, albeit less efficient, is also observed in acetonitrile, but the complex appears to be photoinert in methanol. Spectroelectrochemical studies of some mixed ligand Ru(II) complexes of the type Ru(trpy)(bpy)(py)$\sp{2+}$ and Ru(trpy)($\phi\sb2$-bpy)(py)$\sp{2+}$ as well as the homoleptic polypyridine complexes have been carried out. A linear correlation between the difference of the oxidation and first reduction potentials of the complexes versus the emission energies demonstrates that the redox and spectroscopic orbitals in these complexes are the same. Spectroelectrochemical and EPR results show that the site of the first reduction in these complexes is at the trpy ligand and therefore, the excited states also involve trpy localization. Studies of the luminescence of Cu(I)-containing yeast metallothionein and two truncates have been carried out. The wild type protein and a 48 residue truncate containing two fewer cysteine residues have very similar lifetimes and quantum yields, while those of the 35 residue truncate containing four fewer cysteine residues are significantly smaller. Time-resolved resonance Raman spectroscopy carried out on Ru(bpy)$\sb3\sp{2+}$ in a rigid ethanol methanol glass at 92 K indicates that the transferred electron in the lowest MLCT excited state is localized on a single bipyridine ligand on the nanosecond time scale. The results indicate that solvent reorganization is not a prerequisite to localization.
Degree
Ph.D.
Advisors
McMillin, Purdue University.
Subject Area
Chemistry
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