Supramolecular porphyrin-fullerene conjugates: design, synthesis, electrochemical and photochemical studies

Thesis (Ph.D.)--Wichita State University, College of Arts and Sciences, Dept. of Chemistry.Includes bibliographic references (leaves 189-199)."May 2006."The research reported in this thesis details the synthesis, characterization, electrochemical and photochemical studies of noncovalently linked porphyrin-fullerene based donor-acceptor systems. The first chapter gives an introduction that briefly summarizes the significant events that occur in natural photosynthetic systems, the importance of artificial photosynthetic models and finally, lists new developments in model biomimetic systems of this type. The second chapter discusses synthesis of control compounds and physical methods used in later chapters. The third chapter focuses on the investigation of covalently linked porphyrin-fullerene dyads. A discussion of the role of axially ligated pyridine in decreasing charge recombination rates can also be found in this chapter. The main investigations in the fourth chapter utilize noncovalently linked porphyrin-fullerene triads with two axial coordination bonds with an emphasis on the importance of structural rigidity and the orientation of the donoracceptor entities. The fifth chapter discusses the purpose of a secondary donor and the effect it has in charge separation and charge recombination rates for self assembled supramolecular triads formed via "two-point" binding. Noncovalently linked magnesium porphyrin-fullerene dyads and triads are presented in chapter six. The compounds contained in this thesis were synthesized and characterized by proton NMR and ESI-Mass spectroscopy. Binding constants were obtained by using UV-visible, fluorescence and 1H NMR spectral data. DFT calculations were performed to gain insight into the structural aspects and orientation of the donor-acceptor groups in these supramolecular complexes. Electrochemical and emissions studies (i.e. steady state and time resolved fluorescence, transient absorption) were employed to obtain free energy changes for electron transfer, lifetimes, charge separation and charge recombination rates for photo - induced electron transfer