The mechanism of singlet oxygen sensitized-luminescence of tetra-tert-butylphthalocyanine and the photooxidation of a new antidiabetic drug, troglitazone

Chapter one introduces the generation of singlet oxygen, the mechanism of photooxidation, and the characterization of singlet oxygen.; Chapter two to six describe the study of the delayed fluorescence of tetra-tert-butyl phthalocyanine (Pc). Delayed fluorescence (700 nm) of tetra-tert-butyl phthalocyanine can be sensitized by singlet oxygen generated by thermolysis of 1,4-dimethylnaphthalene endoperoxide. The initial intensity is proportional to the square of the initial concentration of the endoperoxide, and the apparent rate constants of its decay are twice those for singlet oxygen monomol emission. Time-resolved measurements show that the dimol-sensitized Pc luminescence is much more intense than that of the monomol at Pc concentrations above 10{dollar}sp{lcub}-7{rcub}{dollar} M and laser powers above 0.5 mJ per flash. The dependence of phthalocyanine luminescence yield on the phthalocyanine concentration was linear up to 10{dollar}sp{lcub}-4{rcub}{dollar} M, but above this concentration begins to saturate. Dimol-sensitized luminescence of phthalocyanine may prove to be a much more sensitive method for singlet oxygen detection than infrared luminescence at 1270 nm. Kinetic studies demonstrate that the decay of singlet oxygen monomol emission is not a first order exponential as we normally expected. However, when the time t is sufficiently large, the 1270 nm emission becomes exponential. From the kinetic parameters, we estimated the lower limit of dimol lifetime to be 1.7 {dollar}pm{dollar} 0.2 ns ({dollar}pm{dollar}10% error). Effects of quenchers on singlet oxygen-sensitized luminescence has been studied. Five singlet quenchers including trans-{dollar}beta{dollar}-carotene, lauric acid, 2,6-di-tert-butyl-4-methylphenol, {dollar}alpha{dollar}-tocopherol, and DABCO were studied. The results show that the 700 nm luminescence can be used to measure the rate of quenching in different solvents.; Chapter seven details the study of the photooxidation of troglitazone. Photooxidation of troglitazone gave the quinone and quinone epoxide as the major final stable products. An intermediate observed with NMR spectroscopy was shown to be the hydroperoxydienone.