Photophysical studies of fullerene derivatives and organic molecular nanocrystals, and, Singlet oxygen in microheterogeneous media: Direct characterization in zeolites, proteins, and immunoglobins

Chapter 1. General introduction.;Chapter 2. The photophysical properties of a novel series of non-homoconjugated fullerene derivatives are systematically investigated by time-resolved laser flash photolysis. The effect of substitution pattern of non-homoconjugated derivatized fullerenes on the ground state UV-Vis absorption, triplet state properties (lifetime, quantum yield, extinction coefficient), and singlet oxygen quantum yield are reported. A detailed discussion comparing this series of non-homoconjugated fullerenes with functionalized homoconjugated systems and with other non-homoconjugated derivatives is presented.;Chapter 3. The systematic effect on the photophysics of different size orifices created on the fullerene cage of C60 was studied. Using a series of nine open fullerene derivatives each possessing varying orifice sizes, triplet state properties (i.e. triplet energy, triplet quantum yield,) and singlet oxygen quantum are analyzed with respect to the increasing size of the opening and with respect to decreasing amount of pi-conjugation along the C60 framework.;Chapter 4. Nanocrystals suspended in water can be used to record steady state and pump-probe absorption spectra, which should be useful for the study of excited states and reactive intermediates in the solid state. The reprecipitation method for fabricating organic molecular nanocrystals of benzophenone is described in detail and studies (time-resolved transient absorption, steady state and time-resolved phosphorescence, and circular dichroism) are conducted to demonstrate that nanocrystalline suspensions can be used to study solid state photochemical reactions.;Chapter 5. Singlet oxygen quantum yields generated by excited state aromatic amino acids (tryptophan, tyrosine, phenyalanine), N-acetylated amino acids, and important proteins and immunoglobulins have been quantified by time resolved phosphorescence measurements. A small, but significant quantum yield found for proteins and immunoglobulins demonstrates that molecular oxygen can diffuse through the polypeptide matrix and can be sensitized by residues buried within the folds of protein structure.;Chapter 6. Singlet molecular oxygen (1O 2) phosphorescence generated within the cavities of NaY zeolite and porous silica gel is reported. Attempts to study the kinetics of singlet oxygen luminescence decay within the cavities of NaY zeolites in a solvent free microheterogeneous system are reported. Direct time resolved studies of singlet oxygen phosphorescence (1270 nm) using the photosensitizers xanthone, thioxanthone, thionine, and benzophenone encapsulated within NaY zeolites or within the pores of porous silica gel show that the lifetime of singlet oxygen is much shorter in this heterogeneous system than in solution. Several characteristics of the zeolite structure, including the type of exchanged cation and the Si:Al ratio of the zeolite framework may contribute to the shortened lifetime.