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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Photodecomposition Profiles of beta-Bond Cleavage of Phenylphenacyl Derivatives in the Higher Triplet Excited States during Stepwise Two-Color Two-Laser Flash Photolysis
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Photodecomposition Profiles of beta-Bond Cleavage of Phenylphenacyl Derivatives in the Higher Triplet Excited States during Stepwise Two-Color Two-Laser Flash Photolysis

机译：逐步二色两激光闪光光解过程中高三重态激发态中苯甲酰基衍生物的β键裂解的光解曲线

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摘要

Photochemical properties of p-phenylphenacyl derivatives (PP-X) having C-halide, C-S, and C-O bonds in the lowest (T-1) and higher (T-n) triplet excited states were investigated in solution by using single-color and stepwise two-color two-laser flash photolysis techniques. PP-Xs (X = Br, SH, and SPh) undergo beta-bond dissociation in the lowest singlet excited states (S-1) while the C-X bonds of other PP-Xs are stable upon 266-nm laser photolysis. The T-1(pi,pi*) states of PP-X were efficiently produced during 355-nm laser photolysis of benzophenone as a triplet sensitizer. Triplet PP-Xs deactivate to the ground state without photochemical reactions. Upon 430-nm laser photolysis of the T-1 states of PP-X (X = Br, Cl, SH, SPh, OH, OMe, and OPh), decomposition of PP-X in the T-n states was found. On the basis of the changes in the transient absorption, quantum yields (Phi(dec)) of the decomposition of PP-X in the T-n states were deter-mined, while bond dissociation energies (BDE) of the C-X bonds were calculated by computations. According to the relationship between the Phi(dec) and BDE values, it was shown that the decomposition of PP-X in the T-n state is due to beta-cleavage of the corresponding C-X bond, and that the state energy of the reactive T-n for the C-O bond cleavage differs from that for the C-halide and C-S bond cleavage. The reaction profiles of the C-X bond cleavage of PP-X in the T-n states were discussed.
机译：使用单色和逐步两种方法研究了溶液中具有最低（T-1）和较高（Tn）三重态激发态的C-卤化物，CS和CO键的对苯苯甲酰基衍生物（PP-X）的光化学性质色两激光闪光光解技术。 PP-Xs（X = Br，SH和SPh）在最低的单线激发态（S-1）下经历β键解离，而其他PP-Xs的C-X键在266 nm激光光解后稳定。在二苯甲酮作为三重态敏化剂的355 nm激光光解过程中，PP-X的T-1（pi，pi *）状态有效产生。三重态PP-Xs会失活成基态，而不会发生光化学反应。在430 nm激光对PP-X的T-1状态（X = Br，Cl，SH，SPh，OH，OMe和OPh）进行光解后，发现PP-X在T-n状态下分解。根据瞬态吸收的变化，确定了Tn态下PP-X分解的量子产率（Phi（dec）），并通过计算计算了CX键的键解离能（BDE）。 。根据Phi（dec）和BDE值之间的关系，表明在Tn状态下PP-X的分解是由于相应CX键的β裂解，以及反应性Tn的态能CO键的裂解不同于C-卤化物和CS键的裂解。讨论了在T-n状态下PP-X的C-X键断裂的反应谱。

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