Studies on electron and energy transfer in porphyrin and fullerene based systems

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Smith, Phillip M.
D'Souza, Francis

The research presented in this thesis deals with the synthesis, optical and photochemical studies of various porphyrin and/or fullerene based systems. The second chapter deals with the study of fullerene based molecules composed of C60 covalently linked to ferrocene and various nitroaromatic entities. Chapter three involves the study of molecules composed of zinc porphyrin covalently linked with ferrocene(s) self-assembled into supramolecular triads by axial ligation of imidazole bearing fulleropyrrolidine. The triad studied in Chapter four is composed of zinc porphyrin covalently linked to boron-dipyrrin which was selfassembled into a supramolecular complex by axial ligation of imidazole appended fulleropyrrolidine. Chapter five deals with the formation of a dyad complex composed of Zinc N-confused porphyrin axially coordinated to imidazole bearing fulleropyrrolidine. The compounds discussed in this thesis were studied by optical absorbance and emission, electrochemical, and time-resolved photochemical methods. These compounds were mainly characterized by 1H NMR, UV-vis absorbance, and ESI-mass. Binding constants for the supramolecular complexes were arrived using UV-vis spectroscopic methods. Also, B3LYP/3-21G(*) computational method was used to probe the geometric and electronic structure of the compounds studied. The triads studied in Chapter two revealed efficient photoinduced chargeseparation. Interestingly, the computed site of electron transfer using DFT methods was found to track the electrochemical results observed in the cyclic voltammetric experiments. The self-assembled triads in Chapter three revealed efficient charge-separation from the excited zinc porphyrin to the fullerene (C60) entity. Also, the triads revealed efficient charge stabilization due to the presence of ferrocene(s). The self-assembled triad in Chapter four revealed efficient energy transfer from the boron-dipyrrin entity to zinc porphyrin. The selfassembled triad exhibited energy transfer followed by electron transfer to the fullerene (C60) entity. In Chapter five the construction of a dyad composed of zinc N-confused porphyrin and fullerene (C60) was confirmed. Spectro- and photochemical experiments revealed efficient electron transfer from the porphyrin to the fullerene entity.

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Thesis (Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry.
"May 2006."
Includes bibliographic references (leaves 147-155).