Studies of excited state chemistry: Part 1. Hydrogen bonding and the potential for excited state proton transfer in pyridylpyrrole alcohol complexes. Part 2. The development and application of a chemiluminescent detection method for singlet oxygen

Part 1. Hydrogen bonding and the potential for excited state proton transfer in pyridylpyrrole alcohol complexes. A homologous series of 2-(2' -pyridyl)pyrroles were studied as a possible model system for intermolecular hydrogen bonding interactions in molecules that can act as both hydrogen bond donors and acceptors. Steady-state spectroscopic methods were used to assess the importance of intermolecular hydrogen bonding interactions in dilute solutions of 2-(2'-pyridyl)pyrroles in the absence and presence of alcohols. The absorption and fluorescence properties of such solutions were investigated to determine the relevance of such hydrogen bonding interactions in the ground and excited state behavior of the 2-(2 '-pyridyl)pyrroles. It was determined that 3,5-dimethyl-2-(2 '-pyridyl)pyrrole forms weak (K ∼ 5--12 M-1) 1:1 hydrogen-bonded complexes with methanol and t-butyl alcohol in the ground state, and 3,5-di-tert-butyl-2-(2 '-pyridyl)pyrrole forms both 1:1 and 1:2 complexes with the same alcohols. Despite the formation of hydrogen-bonded 2-(2' -pyridyl)pyrrole alcohol complexes, no experimental evidence was found for excited state proton transfer in such complexes.; Part 2. The development and application of a chemiluminescent detection method for singlet oxygen. A set of highly selective chemiluminescent probes has been developed for the detection and quantitation of singlet oxygen ( 1O2), a reactive oxygen species that is known to transform organic pollutants in the environment and elicits cytotoxic effects in biological systems. In this study, a trap-and-trigger detection method is employed, based on the reaction of 1O2 with a spiroadamantyl-substituted vinyl ether probe to form the corresponding thermally stable dioxetane, which undergoes chemiluminescent decomposition upon addition of a chemical trigger. The detection method was shown to be highly selective for 1O 2 relative to superoxide anion and hydrogen peroxide. The sensitivity of this method allows for the accurate measurement of environmentally-relevant (picomolar) steady-state 1O2 concentrations in relatively short exposure tunes. The detection scheme was also used to detect and quantify non-photochemically generated 1O2 in the reactions of other reactive oxygen species, such as superoxide radical anion, hydrogen peroxide, and other organic peroxides and hydroperoxides. The detection of 1O2 in these reactions has significant implications for the non-photochemical formation of 1O2 in both environmental and biological systems.