摘要
通过对Mn(TPP)Cl/NaOCl单加氧酶模拟体系中加入不同轴向配体其电子吸收光谱变化的考察,对影响轴向配体助催化性能的作用因素加以研究,实验表明,具有高位阻效应、较强配位能力的轴向配体表现出优良的助催化性能,轴向配配体本身的pKa数值与其助催化性能并无必然的联系。同时通过对该模型体系催化丙烯环氧化的原位电子吸收谱考察,表明在该催化循环中形成了活性中间络合物:高价的锰氧络合物[Mn(Ⅴ)=O(TPP)Cl]。并根据实验结果提出了该模拟体系催化丙烯环氧化的反应机制。
Factors affecting the promoting effect of the axial ligand on Mn (TPP) Cl/NaOCl mono-oxygenase model for propylene epoxidation under mild conditions was investigated by in-situ UV-Vis spectroscopy for detecting the E ( V/VI ) variation of Mn ( TPP ) Cl in 1, 2-dichloroe-thanl solvent when different axial ligand was added. The result showed that the better promoting effect of the axial ligand depended on its steric hinderance effect due to its big size, there existed little relation between the yield of propylene oxide with the pKa value of the axial ligand. For 4-benzylpyridine as the axial ligand of Mn(TPP) Cl/NaOCl mono-oxygenase model system, the π electron-cloud interaction of 4 -benzylpyridine with the conjugative macrocycle of the met-alloporphyrin stabilizing the active intermediate of a high valent metal-OXO complex was another factor for its better promoting effect on the catalytic activity of propylene epoxidation.The formation of the catalytic active complex of a high valent manganese ( V )-OXO species in the Mn ( TPP ) Cl/NaOCl model system for propylene epoxidation was also characterized by in-situ UV-Vis spectra.Based on the above results and those reported in the literatures, the catalytic cycle of the propylene epoxidation catalyzed by Mn(TPP)Cl /NaOCl was proposed.
出处
《分子催化》
EI
CAS
CSCD
1991年第3期202-208,共7页
Journal of Molecular Catalysis(China)
