Mechanistic studies of photobase generation from ammonium tetraorganyl borate salts
Mechanistic studies of photobase generation from ammonium tetraorganyl borate salts
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DOI：
10.1021/cm980618w
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发表时间：
1999-01-01
影响因子：
8.6
通讯作者：
Neckers, DC
中科院分区：
文献类型：
--
作者：
Kaneko, Y;Sarker, AM;Neckers, DC
用稳态光谱、激光闪光光解和产物分析等方法研究了N，N，N-三丁基-N-乙酰萘酮硼酸铵（1）和N，N，N-三丁基-N-乙酰苯并[B]呋喃硼酸铵（2）的光化学和光物理性质。激发前体的反应导致通过碳-氮键断裂形成叔胺。激光闪光光解和产物分析证实均裂碳-氮键断裂和相应的乙酰基自由基的形成，在乙腈中，二聚形成偶联产物。在所有的情况下，光解离发生在如此短的寿命，它不能被测量纳秒闪光光解。消失的量子产率被认为是更高的三苯基丁基硼酸盐阴离子比那些四苯基硼酸盐阴离子。一个建议的机制涉及电子从硼酸盐的激发受体作为主要的光化学步骤。激发态猝灭的速率常数与电子转移的自由能相关，如从激发态能量和受体的还原电位估计的。
The photochemistry and photophysics of N,N,N-tributyl-N-acetonaphthone ammonium borate (1) and N,N,N-tributyl-N-acetobenzo[b]furan ammonium borate (2) have been investigated by steady-state spectroscopy, laser flash photolysis, and product analysis. Reaction of excited precursors leads to formation of tertiary amines by carbon-nitrogen bond cleavage. Laser flash photolysis and product analysis confirm homolytic carbon-nitrogen bond scission and the formation of respective acetyl radicals which, in acetonitrile, dimerize to form coupled products. In all cases, photodissociation occurs with such a short lifetime that it could not be measured by nanosecond flash photolysis. The quantum yield of disappearance was found to be higher for salts of the triphenylbutyl borate anion than for those of the tetraphenyl borate anion. A proposed mechanism involves electron transfer from borate to the excited accepters as the primary photochemical step. The rate constants for excited-state quenching correlate with the free energy for electron transfer, as estimated from the excited-state energies and the reduction potentials of the acceptors.