氮氧自由基对苯甲酮三重激发态猝灭反应的 TR-EPR 研究

摘要

利用 TR-EPR 技术并结合瞬态吸收光谱方法研究了乙二醇（EG）均相溶液中稳态自由基TEMPO 对光诱导苯甲酮三重激发态3BP *的猝灭反应，分析了其中的光化学反应中间体，讨论光解自由基的 CIDEP 机理，测量了 TEMPO 对3BP *的猝灭速率常数．结果表明，EG 均相溶液中 BP *与溶剂分子 EG 之间存在氢原子转移反应，生成苯甲酮中性自由基 BPH・和乙二醇羰自由基 Egl[-H]・．E ＋ E/A 的 CIDEP 信号说明 TM 机理是体系 CIDEP 的主要机理．另外，TEMPO 对3BP *也有明显的猝灭作用，猝灭速率常数为1．40×107 L ．mol -1・s -1．%The quenching reaction of photo-induced excited triplet of benzophenone (3BP * ) by stable radical TEMPO in ethylene glycol (EG ) homogeneous solution have been studied by using time-resoled electron paramagnanetic resonance (TR-EPR ) technique and transient absorptive spectrum method . The transient reaction intermediates and chemical induced dynamic electron polarization (CIDEP ) mechanism have been analyzed . The quenching rate constant of 3 BP * by TEMPO has been measured . The experimental results indicate that there is hydrogen atom transfer reaction from EG to 3 BP * ,and the neutral semiquinone radical and ketyl radical are generated .The E + E/A pattern CIDEP means that triplet mechanism (TM ) is the main mechanism .TEMPO is an effective quencher to 3 BP * and the quenching rate constant is 1 .40 × 107 L・mol - 1・s - 1 .