One-electron Reduction and Electron Transfer Reaction Controlled by Cyclodextrin Inclusion Complexation

环糊精（CD）在水溶液中与各种有机分子形成包合物，这取决于其疏水空腔和客体分子的大小。采用预置脉冲辐解方法研究了芳香羧酸酯和芳香磺酸酯在包结络合物控制下的单电子还原反应。芳香族电解质水溶液的脉冲辐解导致溶质中芳香族部分被水合电子单电子还原，当疏水芳香族部分被包含在CD空腔中时，反应被有效地阻滞。因此，联苯-4-羧酸酯（BPC）、联苯-4-乙酸酯（BPA）和联苯-4-磺酸酯（BPS）的单电子还原的速率常数通过与β-CD的络合而明显降低，β-CD的空腔最适合联苯基。类似地，芘-1-羧酸酯（PyC）、4-芘-1-丁酸酯（PyB）和芘-1-磺酸酯（PyS）的单电子还原是r ...更多信息 用最佳拟合的γ-CD对单电子还原和电子转移反应进行了控制。BPS和PyS混合溶液的选择性还原已经通过使用β-和γ-CD实现。PyS与γ-CD的络合作用也有效地抑制了还原态BPS向PyS的电子转移。由于BPA亚甲基的空间位阻效应，BPC与α-CD之间形成了2络合物，而BPC与α-CD之间不形成2络合物。PyC、PyB和PyS与γ-CD形成2 ; 2复合物，并且PyC和PyS的复合物在客体单电子还原时发生结构变化。由脉冲辐解数据确定了BPC、BPA和BPS的1：1络合物的缔合常数。少

Cyclodextrins (CDs) form inclusion complexes with various organic molecules in aqueous solution depending on the sizes of their hydrophobic cavities and of the guest molecules. The preset pulse radiolysis study is concerned with the one-electron reduction of aromatic carboxylates and sulfonates controlled by the inclusion comlexation. The pulse radiolysis of aqueous solutions of the aromatic electrolytes results in the one-electron reduction of the aromatic moieties of the solutes by the hydrated electron. The reaction is effectively retarded when the hydrophobic aromatic moieties are included in the CD cavities. Thus, the rate constants for the one-electron reduction of biphenyl-4-carboxylate (BPC), biphenyl-4-asetate (BPA) and biphenyl-4-sulfonate (BPS) are appreciably reduced by the complexation with beta-CD,whose cavity best fits to the biphenylyl group. Similarly, the one-electron reduction of pyrene-1-carboxylate (PyC), 4-pyren-1-ylbutyrate (PyB) and pyrene-1-sulfonate (PyS) is r … More etarded by the best fitting gamma-CD.The control of the one-electron reduction and electron transfer reactions has been examined for the solutions of mixtures of the sulfonates. The selective reduction of a mixed BPS and PyS solution has been achieved by using beta-and gamma-CDs. The electron transfer from the reduced BPS to PyS is also retarded effectively by the complexation of PyS with gamma-CD.The pH dependence of the effect of the complexation has demonstrated that a 1 ; 2 complex is formed between BPC and alpha-CD but not between BPC and alpha-CD because of the steric effect of the methylene group of BPA.The apparent retarding effect of alpha-CD on the one-electron reduction of BPC is observed at much higer host concentrations compared with that of beta-CD.PyC,PyB and PyS form 2 ; 2 complexes with gamma-CD,and the complexes of PyC and PyS undergo a structural change upon the one-electron reduction of the guests. The association constants of the 1 ; 1 complexes of BPC,BPA and BPS have been determined from the pulse radiolysis data. Less