ELECTRON-TRANSFER PHOTO-OXYGENATION .5. OXIDATION OF PHENYL-SUBSTITUTED ALKENES SENSITIZED BY CYANOANTHRACENES
ELECTRON-TRANSFER PHOTO-OXYGENATION .5. OXIDATION OF PHENYL-SUBSTITUTED ALKENES SENSITIZED BY CYANOANTHRACENES
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DOI：
10.1021/ja00539a018
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发表时间：
1980-01-01
影响因子：
15
通讯作者：
FOOTE, CS
中科院分区：
文献类型：
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作者：
ERIKSEN, J;FOOTE, CS
缺电子敏化剂 9, 10-二氰基蒽 (DCA) 和 9-氰基蒽 (CNA) 可敏化氧饱和极性溶剂中 1, 1-二苯乙烯 (1)、反式和间二苯乙烯 (12 和 14) 以及四苯乙烯 (18) 的光氧化。 MeCN 中的光产物包括裂解产物 Ph2CO 和 PhCHO、环氧化物，以及二苯乙烯的情况下的顺反异构化烯烃。对于 1、12、14 和 18，烯烃消失的量子产率分别为 0.8、0.5、0.2 和 0.15。在非极性溶剂中不发生光氧化作用。 MeCN 中的反应伴随着 DCA 和 CNA 荧光的猝灭。测量的猝灭速率常数与电子转移过程计算的值非常相似，并且在实验误差范围内与根据产物形成的受体浓度依赖性确定的值一致。通过添加少量氧化电位低于烯烃的化合物来猝灭光氧化，而氧化电位较高的化合物几乎没有影响。所有结果都与涉及供体自由基阳离子和敏化剂自由基阴离子的电子转移机制一致，该机制随后将氧还原成超氧化物。该数据与单线态氧机制不兼容。
The electron-deficient sensitizers 9, 10-dicyanoanthracene (DCA) and 9-cyanoanthracene (CNA) sensitize the photooxidation of 1, 1-diphenylethylene (1), trans-and m-stilbene (12 and 14), and tetraphenylethylene (18) in oxygen-saturated polar solvents. The photoproducts in MeCN include the cleavage products Ph2CO and PhCHO, the epoxides, and, in the case of the stilbenes, cis-trans isomerized olefin. Quantum yields for disappearance of the alkenes are 0.8, 0.5, 0.2, and 0.15 for 1, 12, 14, and 18, respectively. No photooxygenation takes place in nonpolar solvents. The reactions in MeCN are accompanied by quenching of the DCA and CNA fluorescence. The measured quenching rate constants closely resemble values calculated for an electron-transfer process and agree, within experimentalerror, with those determined from the acceptor concentration dependence of product formation. The photooxygenations are quenched by the addition of small amounts of compounds of lower oxidation potential than thatof the alkenes, whereas compounds of higher oxidation potential have little effect. All results are consistent with an electron-transfer mechanism involving a donor radical cation and sensitizer radical anion which subsequently reduces oxygen to superoxide. The data are not compatible with a singlet oxygen mechanism.