title: Efficiencies of singlet oxygen production and rate constants for oxygen quenching in the S1 state of dicyanonaphthalenes and related compounds.
abstract: The quantum yield of singlet oxygen ((1)O(2) ((1)Delta(g))) production (Phi(Delta)) in the oxygen quenching of photoexcited states for 1,2-dicyanonaphthalene (1,2-DCNN), 1,4-dicyanonaphthalene (1,4-DCNN) and 2,3-dicyanonaphthalene (2,3-DCNN) in cyclohexane, benzene, and acetonitrile was measured using a time-resolved thermal lens (TRTL) technique, in order to determine the efficiency of singlet oxygen ((1)Delta(g)) production in the first excited singlet state (S(1)), (f(Delta)(S)). The efficiencies of singlet oxygen ((1)Delta(g)) production from the lowest triplet state (T(1)), (f(Delta)(T)), were nearly unity for all DCNNs in all the solvents. The values of f(Delta)(S) were fairly large for 1,2-DCNN (0.33-0.57) and 1,4-DCNN (0.33-0.66), but were close to zero for 2,3-DCNN. Rate constants for oxygen quenching in the S(1) state (k(q)(S)) obtained for these compounds were significantly smaller than diffusion-controlled rate constants. The kinetics for processes leading to production and no production of singlet oxygen is discussed on the basis of the values of f(Delta)(S) and k(q)(S). The results obtained regarding phenanthrene (PH), 9-cyanophenanthrene (9-CNPH), pyrene (PY) and 1-cyanopyrene (1-CNPY) are also discussed.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka Prefecture University, Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan. fuji@c.s.osakafu-u.ac.jp
authors.forename: Fujio
authors.initials: F
authors.lastname: Tanaka
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Tsumura
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Furuta
authors.forename: Kenichi
authors.initials: K
authors.lastname: Iwamoto
authors.forename: Masami
authors.initials: M
authors.lastname: Okamoto