Characterization of the Localized Excited State of Monosubstituted Ruthenium (ii) Complexes, and Thermodynamic and Structural Investigations on Langmuir Monolayers and Built-Up Multilayers.

This dissertation consists of two parts. The first part is contained in chapter one, which describes an Electron Spin Resonance (ESR) investigation of the metal -ligand charge transfer (MLCT) excited state of monodiimine complexes of ruthenium (II). Specifically, the electrochemically reduced mono-substituted diimine complexes [ {rm Ru(bpy)(CN)}_4]^ {2-}, [{rm Ru(bpm)(CN)}_4]^{2- }, and [{rm Ru(bpz)(CN) }_4]^{2-}, where bpy = 2,2^'-bipyridine, bpm = 2,2^'-bipyrimidine, and bpz = 2,2^'-bipyrazine, were characterized by ESR spectroscopy. Well-resolved hyperfine structure (hfs) was observed in all three complexes, and coupling constants were calculated from the observed spectra. The hyperfine coupling constants derived from the ESR spectra indicate that the electronic spin density is largely localized within the pi* orbitals of the reduced species. Emission spectra, solvatochromic absorption spectra, and cyclic voltammetry data are also presented and discussed. The second part of this dissertation constitutes the remaining chapters, and details a comprehensive series of investigations on a monolayer fatty acid film system prepared by the classical Langmuir technique. Specifically, monolayer and multilayer films composed of mixtures of behenic acid and platinum bis(2-(2-thienyl)-pyridine were prepared by the Langmuir-Blodgett and Langmuir-Schaefer techniques, and characterized by FTIR transmission and reflectance-absorbance spectroscopy, visible dichroism, emission spectroscopy, transmission electron microscopy and electron diffraction. Langmuir film properties were investigated as a function of subphase temperature to elucidate the phase changes observed in the pressure-area isotherms for these mixtures. Chromatographic analysis of phenacyl derivatives of the fatty acids coupled with luminescence measurements on the platinum complex was performed to elucidate the composition and structure of the multilayer films. The results suggest that the platinum complex assumes a vertical orientation relative to the substrate in the multilayer films, and retains this relative orientation after expulsion from the fatty acid matrix, which occurs at and below 45 mN/m in the film at the air-water interface.