以八乙基卟啉及其锌螯合物为反应中心电子转移模型的光引发离子形成。
Photo-initiated ion formation from octaethyl-porphyrin and its zinc chelate as a model for electron transfer in reaction centers.
作者信息
Ballard S G, Mauzerall D
出版信息
Biophys J. 1978 Oct;24(1):335-45. doi: 10.1016/S0006-3495(78)85381-8.
Ion formation from the reaction of triplet (T) and ground state (P) octaethyl-porphyrin (OEP) and zinc octaethyl porphyrin (ZnOEP) and the corresponding cross-reactions have been measured in dry acetonitrile. A uniquely sensitive and fast conductance apparatus and a pulsed dye laser allowed the measurements to be made at the necessarily very low concentrations of T. The hemogeneous reaction of T (ZnOEP) and P (ZnOEP) occurs with rat constant k(1) = 2.0 x 10(8) M(-1)s(-1) and an ion yield of 67%. The similar homogeneous reaction of OEP has k(2) = 1.3 x 10(8)M(-1)s(-1) but an ion yield of only 3%. The cross-reaction of T (OEP) with P (ZnOEP) has k(3) = 1.5 x 10(8) M(-1)s(-1) and an ion yield of 27%, while the inverse cross-reaction of T (ZnOEP) with P (OEP) has k(4) = 3 x 10(8) M(-1)s(-1) and an ion yield of 20%. Thus, the rate constants are only slightly affected but the yields are sensitive to the porphyrin. The possible formation of the heterogeneous ions ZnOEP+ + OEP-, thermodynamically favored by 0.3 V over the homogeneous ions, has little influence on the observed yields. The data are explained by electron transfer and Coulomb field-electon spin-controlled escape of the initial ion-pair.
在干燥乙腈中，已测量了三重态（T）与基态（P）八乙基卟啉（OEP）、八乙基锌卟啉（ZnOEP）反应形成离子的过程以及相应的交叉反应。一种独特灵敏且快速的电导装置和一台脉冲染料激光器使得能够在必然非常低的T浓度下进行测量。T（ZnOEP）与P（ZnOEP）的均相反应以速率常数k(1)=2.0×10⁸M⁻¹s⁻¹发生，离子产率为67%。OEP的类似均相反应k(2)=1.3×10⁸M⁻¹s⁻¹，但离子产率仅为3%。T（OEP）与P（ZnOEP）的交叉反应k(3)=1.5×10⁸M⁻¹s⁻¹，离子产率为27%，而T（ZnOEP）与P（OEP）的反向交叉反应k(4)=3×10⁸M⁻¹s⁻¹，离子产率为20%。因此，速率常数仅受到轻微影响，但产率对卟啉敏感。异质离子ZnOEP⁺ + OEP⁻的可能形成在热力学上比均相离子更有利0.3V，但对观察到的产率影响很小。数据通过电子转移和初始离子对的库仑场 - 电子自旋控制逃逸来解释。
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