Electron Transfer and Energy Transfer in Silicon-Bridged Copolymers and Hybrid Materials
Date Issued
2009
Date
2009
Author(s)
Chen, Chih-Hsien
Abstract
Silylene spaced copolymers for photoinduced electron transfer studies have been designed and synthesized. The donor and acceptor chromophores in these copolymers are arranged in alternating manner separated by silylene moieties. These copolymers are prepared by rhodium catalyzed hydrosilylation reactions. The rates of photoinduced electron transfer are found to be dependent on the free energy differences of the photoinduced electron transfer reactions between the donor and acceptor. The rates of the reactions follow the Marcus theory nicely. Notably, the inverted region is observed in forward electron transfer processes. Besides, the forward and backward electron transfer processes might be governed by the same electronic coupling and reorganization energy. The confined distance between donor and acceptor chromophores via silylene spacer might avoid the diffusion control limitation of electron transfer, and maintained the intramolecular process. Moreover, dual fluorescence is observed in certain copolymers, and the solvatochromic measurements show that the dual fluorescence may consist of local emission of acceptor chromophores and emission from charge recombination. The occurrence of dual fluorescence may be governed by free energy change of electron transfer reaction and environment polarity.he hybrid materials consisting of two to three covalently bound organic chromophores at different ratios are conveniently synthesized and fabricated. The energy transfer and electron transfer processes within these hybrid materials have been studied. The fluorescence spectra reveal the occurrence of energy transfer from donor to acceptor chromophores, and the light-harvesting ability of these hybrid materials increased with increasing the molar fraction of donor chromophore. Time-resolved fluorescence experiments are employed to elucidate the average rates and efficiencies of energy transfer in these organic inorganic hybrid systems.he photoinduced electron transfer processes are also investigated in these hybrid materials. The fluorescence quenching of the acceptor chromophores is observed in the presence of the electron donor chromophores, and the fluorescence intensities are decreased with increasing molar concentration of the donor moiety. The results indicate the occurrence of photoinduced electron transfer in hybrid materials, and that is confirmed by time-resolved fluorescence spectroscopy. The hybrid materials have been shown to provide antenna effect to facilitate energy transfer and allow the occurrence of electron transfer between chromophores
Subjects
electron transfer
energy transfer
Marcus theory
polymer
hybrid materials
Type
thesis
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