卟啉对芳烃侧链的分子识别规律及活化机制研究

Porphyrin exhibits high catalytic activity and selectivity in the oxidation reaction of aromatic side chain. Molecular recognition is one of the key links for the high efficient catalysis of porphyrin. Porphyrin can active and regulate the aromatic side chain oxidation part selectively and control the oxidation depth through molecular recognition to improve the conversion of reactants and selectivity of target products. Contraposing the problems of molecular recognition rule and activation mechanism of aromatic side chain by porphyrin unclear, this program will use quantum chemistry and molecular dynamics simulation methods to study molecular recognition and activation mechanism of aromatic side chain by porphyrin. The key research will investigate the effect of the structural characteristics of porphyrin and aromatic side chain on molecular recognition mode and driving force in the oxidation reaction of aromatic side chain catalyzed by porphyrin, explore the rule of porphyrin molecular recognition with aromatic side chain, and obtain the essential role orienting aromatic side chain and locating the porphyrin active group. On the base of molecular recognition, the activation of aromatic side chain by porphyrin will be studied and the key factors regulating the activation selectivity will be obtained. Combined computational data with experimental data, the relationship between molecular recognition and catalytic performance of porphyrin will be studied to elucidate the effect rule of molecular recognition on the catalytic activation of aromatic side chain by porphyrin and provide a theoretical basis for the design of new and high efficient catalyst.

卟啉在催化氧化芳烃侧链的反应时可同时表现出较高的催化活性和选择性。而分子识别正是卟啉发挥高效催化作用的关键环节之一。通过分子识别，卟啉可选择地活化和调控芳烃侧链的氧化部位并可控制其氧化深度，进而提高原料的转化率及目标产物的选择性。针对目前卟啉分子识别芳烃侧链的规律及活化机制尚不明确的问题，本项目采用量子化学及分子动力学模拟方法，深入研究卟啉分子识别及活化芳烃侧链的作用机制，重点考察卟啉催化氧化芳烃侧链时，卟啉及芳烃分子结构对分子识别模式及驱动力的影响，探讨卟啉分子识别芳烃侧链的规律，找到分子识别过程中调控芳烃侧链取向,合理定位卟啉活性基团的关键因素，并在此基础上研究卟啉对芳烃侧链的活化作用，得到相应活化机制及有效调控活化选择性的关键因素。同时结合实验研究，建立分子识别作用与卟啉催化性能之间的关系，阐明分子识别对卟啉催化活化芳烃侧链的影响规律，为设计新型高效的仿生催化剂提供理论基础。

卟啉作为催化剂的催化氧化反应中，卟啉对底物分子的识别与活化是卟啉起催化作用的关键环节。针对目前卟啉对芳烃侧链进行分子识别的规律及活化机制尚不明确的问题，本项目采用分子动力学模拟方法研究了卟啉催化氧化芳烃侧链过程中，卟啉对氧气分子和芳烃分子的识别作用，并结合量子化学方法研究了金属卟啉对芳烃侧链α-H原子的活化。研究结果表明，增强金属卟啉与底物之间的分子识别作用有利于金属卟啉与芳烃分子形成稳定复合物，并利于金属卟啉对芳烃侧链α-H原子的选择性活化。研究金属卟啉对氧气分子的识别发现，中心金属为易变价金属的铁卟啉，锰卟啉和钴卟啉均与氧气分子之间形成配位键，对氧气分子的活化较强。中心金属离子为不易变价金属的锌卟啉和铜卟啉与氧气分子之间未形成配位键，对氧气分子的影响较弱。卟啉环外围引入供电子基以及在轴向引入供电性较强的配体均能够增强金属卟啉与分子氧之间的相互作用，促进金属卟啉对分子氧的活化。对芳烃分子实现有效识别的是金属卟啉的高价金属氧化物。其与芳烃分子之间的分子识别作用越强，越有利于金属卟啉对芳烃侧链上的α-H原子进行选择性催化氧化。采用密度泛函理论对金属卟啉活化芳烃侧链α-H原子进行研究，结果发现，金属卟啉对芳烃侧链α-H原子的活化遵循 “反弹机制”，且金属卟啉高价金属氧化物提取芳烃侧链α-H原子是整个反应的速控步骤。活化能取决于芳烃化合物中C-H键以及金属卟啉的高价金属氧化物与提取的H原子所形成的O-H键的强弱。C-H键越弱或者O-H键越强，活化能越低，金属卟啉越容易氧化芳烃侧链上的α-H原子。提氢步骤的活化能与C-H键或O-H键键能之间呈现线性相关。把活化能分解为形变能和相互作用能发现，能垒的变化由形变能和相互作用能共同决定。