取代金属卟啉催化剂的构效关系及催化氧化机理

The QSAR Between the Structure and Catalytic Activity for Metalloporphyrin and Mechanism of Catalytic Oxidation

设计、合成了15种取代四苯基(铁、钴、锰)卟啉仿生催化剂,并用红外光谱、紫外光谱等进行了结构表征.在温和条件下,将其用于催化氧气液相氧化对硝基甲苯制取对硝基苯甲酸,考察了各种金属卟啉催化剂的活性,发现其催化活性随着环外取代基吸电子能力的增强而增大.进一步采用量子化学半经验PM3计算法对上述金属卟啉催化剂进行了计算,与其催化活性对比,发现金属卟啉分子微观结构参数与其催化活性具有很大的相关性.从理论上阐述了金属卟啉催化剂催化活性强弱的原因.

15 metalloporphyrin compounds were designed, synthesized, and characterized by element analysis,IR, UV-Vis. These metalloporphyrins compounds were used to catalyze the oxidation of p-nitrotoluene （PNT） to p-nitrobenzoic acid （PNBA） in the presence of molecular oxygen under mild conditions. Their catalytic activities were characterized by oxidation of PNT. The experimental results showed that the catalytic activities increased with increase of the electron-deficient degree of peripheral substituent on the porphyrin ring. Their molecular frontier orbital energies EHOMO etc were calculated by using PM3 semi-empirical molecular orbital method. The QSAR between structure parameter （EHOMO） and catalytic activity of metalloporphyrin was investigated by combining activity （yield of PNBA） with EHOMO of 15 catalysts. It was found that there was excellent linear correlation between the catalytic activity and frontier orbital energy. Through linear regression the following equations were obtained. The catalytic activities order of metalloporphyrins was explained in theory.