Application of diffuse reflectance laser-flash photolysis to the study of aromatic probes in beta-cyclodextrin solid complexes

Time-resolved diffuse reflectance laser-flash photolysis techniques were employed to study the photochemistry of benzil, naphthalene, and pyrene within beta-cyclodextrin solid complexes. The photochemistry of benzil and naphthalene is dominated by their triplet state. In the case of pyrene, the formation of radical cations and radical anions is observed, in addition to the signals due to the triplet state. In all three cases triplet excited states exhibit non-exponential (multi-component) kinetics. Analysis of triplet decays by means of lifetime distributions shows that quenching by oxygen is significantly restricted within beta-cyclodextrin solid complexes. This result is attributed to the protection offered by the cyclodextrin cavity, which limits the space available for diffusion and contact of reactants. (C) 1997 Elsevier Science S.A.