AN INVESTIGATION OF ENERGIES AND DYNAMICS USING SPECTROSCOPIC ANALYSIS OF CHARGE TRANSFER COMPLEXES IN CRYSTALS, AND CHANGING SOLVENT POLARITIES

Abstract

A spectrum is a signature associated with the tested molecular system and contains energetic and dynamic information unique to that system. Analysis of the spectral shape, maxima, and where a spectrum begins defines traits of the associated molecular system. Spectra are influenced not only by the molecular system being tested, but by the surrounding conditions. Spectral traits of a molecular system will change with the phase, temperature, or the surrounding medium. Examination of spectral changes influenced by changing environmental conditions can be used to develop possible models describing the energies required for driving force and rearrangement, as well as the dynamics within a molecular system. Spectral analysis can be assisted by previously developed models such as the Golden Rule (GR) for electron transfer. Collected spectra can be used alongside a GR calculation to extract driving force and reorganization energies, as well as kinetic information from the collected spectra. By comparing spectra of a single molecular system through changing environmental conditions, this research describes studies of electron transfer in charge-transfer complexes in solution, and in solids at ambient and low temperatures. Solvatochromic shifts and the effects on energies and dynamics were observed in absorption and fluorescence spectra collected by testing charge-transfer complexes using different solvents across a progression of polarities. Energies and dynamics of solid state charge transfer complexes were examined using the GR together with fluorescence spectra collected by fluorometer, and accompanying decay traces using a time correlated single photon counter. The collective results across ambient temperature and 77 K were used to develop a potential model describing the elucidated charge transfer driving force, molecular rearrangement energies, and kinetics in solid state charge transfer crystals.