Ligand photoisomerization in metalloporphyrin complexes. A possible case of photocatalysis
Ligand photoisomerization in metalloporphyrin complexes. A possible case of photocatalysis
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金属卟啉配合物中的配体光致异构化。
DOI：
10.1021/ja01040a064
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发表时间：
1969
影响因子：
15
通讯作者：
I. Lopp
中科院分区：
文献类型：
--
作者：
D. Whitten;P. Wildes;I. Lopp
其中MP=金属卟啉，L=顺式配体，L ′ =反式配体。路径A是合理的，因为光激发的金属卟啉可以作为电子供体7，因为自由基离子的烯烃，如芪进行顺反异构化和电子转移反应。8.醌可通过从MPL* 或L~中夺取电子而中断路径A。然而，离子过程，如反应1是不可能在非极性溶剂，如苯，我们看到没有证据表明，在苯-锌etio-porphyrin I-NPE溶液或甚至苯-锌etio-porphyrin I-quinone溶液的ESR腔照射后形成自由基。9溶剂效应提供了反对路径A的证据。在乙腈和乙醇等极性溶剂中，反应速度不到十分之一，这应该有利于离子过程。闪光光谱研究（表II）显示除了锌卟啉三重态之外没有瞬变。11
MPL'*+ L MPL*+ L'(5) where MP= metalloporphyrin, L= cis ligand, L'= trans ligand. Path A is reasonable since photoexcited metalloporphyrins can serve as electron donors7 and since radical ions of olefins such as stilbene undergo cis-trans isomerization and electron-transfer reactions. 8 Quinone could interrupt path A by abstracting elec-trons from MPL* or L~. However, ionic processes such as reaction 1 are unlikely in nonpolar solvents such as benzene, and we see no evidence for formation of radicals upon irradiation of benzene-zinc etio-porphyrin I-NPE solutions or even benzene-zinc etio-porphyrin I-quinone solutions in an esr cavity. 9 Solvent effects provide evidence against pathA. The reaction is less than one-tenth as fast in polar solvents such as acetonitrile and ethanol which should facilitate ionic processes. Flash spectroscopic studies (Table II) reveal no transients other than the zinc porphyrin triplet. 11