group on the bridge have lifetimes about one-tenth those of unsubstituted compounds. These results and the variations in fluorescence maximum wavelengths are rationalized by assumptions that there is some degree of charge transfer from aromatic ring to C-X bond in the photoexcited state and that this favors decay to the ground state. When more or less complete intramolecular electron transfer to a zwitterionic
报告了各种 7-取代和 7,8-二取代二苯并双环 (2.2.2)
辛二烯和藜芦并苯并双环 (2.2.2)
辛二烯在
环己烷和/或
乙腈中的吸收最大值、荧光最大值和荧光量子产率。单线态寿命已从这些数据中计算出来。那些对光溶剂分解和/或 Wagner-Meerwin 光重排具有反应性的化合物的荧光产率(和寿命)是饱和桥上仅含氢的相应化合物的 10/sup -2/-10/sup -4/ 倍。具有光惰性但在桥上具有吸电子基团的化合物的寿命约为未取代化合物的十分之一。这些结果和荧光最大波长的变化通过假设存在一定程度的电荷从光激发态的芳环转移到 CX 键并且这有利于衰变到基态来合理化。当或多或少完全分子内电子转移到两性离子双自由基中间体时,4-80 ps 范围内的寿命就完成了。