The efficiency of [2+2] photocycloadduct formation was examined by measuring fluorescence lifetimes and the quantum yields of fluorescence and product formation in two series of p-methoxyphenylalkenyl 9-phenanthrenecarboxylates (A-nE and B-nE). In (E)-3-(p-methoxyphenyl)-3-pentenyl, (E)-4-(p-methoxyphenyl)-4-hexenyl, and (E)-5-(p-methoxyphenyl)-5-heptenyl 9-phenanthrenecarboxylates (B-2E, B-3E, and B-4E, respectively) the intramolecular quenching leads to product (cyclobutane+oxetane) formation in almost unit efficiency, while in (E)-4-(p-methoxyphenyl)-3-butenyl and (E)-5-(p-methoxyphenyl)-4-pentenyl 9-phenanthrenecarboxylates (A-2E and A-3E, respectively) exciplex→product efficiency is a half to three quarters. Intermediacy of plural exciplex intermediates is suggested in the present bichromophoric systems on the basis of exciplex quenching results.
通过测量荧光寿命以及两个系列对
甲氧基苯烯基9-
菲羧酸酯(A-nE和B-nE)的荧光量子产率和产物形成,研究了[2+2]光环加成形成的效率。在(E)-3-(对
甲氧基苯基)-3-
戊烯基、(E)-4-(对
甲氧基苯基)-4-己烯基和(E)-5-(对
甲氧基苯基)-5-庚烯基9-
菲羧酸酯(分别为B-2E、B-3E和B-4E)中,分子内猝灭导致产物(
环丁烷+氧杂
环丁烷)形成几乎单位效率,