ELECTRON-TRANSFER REACTIONS INVOLVING PORPHYRINS AND CHLOROPHYLL-A

被引:50
作者
NETA, P [1 ]
SCHERZ, A [1 ]
LEVANON, H [1 ]
机构
[1] HEBREW UNIV JERUSALEM,JERUSALEM 91000,ISRAEL
关键词
D O I
10.1021/ja00507a031
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Electron transfer reactions involving porphyrins (P) and quinories (Q) have been studied by pulse radiolysis. The porphyrins used were tetraphenylporphyrin (H2TPP), its tetracarboxy derivative (H2TCPP), the sodium and zinc compounds (Na2TPP and ZnTPP), and chlorophyll a (Chla). These compounds were found to be rapidly reduced by electron transfer from (CH3)2C0-. Reduction by (CH3)2COH was rapid in aqueous solutions but relatively slow in i-PrOH solutions. Transient spectra of the anion radicals were determined and, in the case of H2TCPP-, a pK = 9.7 was derived for its protonation. Electron-transfer reactions from the anion radical of H2TCPP to benzoquinone, duroquinone, 9,10-anthraquinone 2-sulfonate, and methylviologen occur in aqueous solutions with rate constants~107-109 M-1 s-1 which depend on the pH and the quinone reduction potential. Reactions of Na2TPP-, ZnTPP-, and Chi a- with anthraquinone in basic i-PrOH solutions occur with rate constants ~109 M-1 s-1. The spectral changes associated with these electron-transfer reactions as observed over a period of ~1 ms indicated, in some cases, the formation of an intermediate complex [P…Q-]. © 1979, American Chemical Society. All rights reserved.
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页码:3624 / 3629
页数:6
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