共还原剂在架通金属卟啉仿生催化与酶催化桥梁中的作用规律及机制研究

Low catalytic efficiency and poor selectivity toward object product could be observed in the direct metalloporphyrin-catalyzed biomimetic oxidation system. Our previous studies have shown that co-reductant can bridge biomimetic catalysis and enzymatic catalysis, in which biomimetic catalytic oxidation presents the genuine features of enzymatic catalysis, that is, high efficiency, specificity, and mild conditions. In our further studies, the specific substrate recognition of the different structural co-reductant was observed in the biomimetic catalytic oxidation. The possibility of promoting dioxygen activation in the presence of co-reductant was proposed based on our original results. But the detail mechanism of co-reductant in the biomimetic catalytic oxidation, mechanism of the specific substrate recognition is not clear. On the basis of metalloporphyrins-catalyzed oxidations in the presence of co-reductant, this project devotes to obtain the concrete evidences of the interaction between co-reducant and metalloporphyrins, promoting dioxygen activation, the generation of oxo-metal species and oxygen transfer by in situ IR, UV-vis, EPR, isotope mass and quantum chemical calculation. Further to obtain the mechanism of the specific substrate recognition of co-reductant. Through the structure-activity relationship studies, the project also aims to achieve molecular design of the co-reductant for biomimetic catalytic oxidtion. The project is expected to reveal the mechanism of co-reductant on increasing the biomimetic catalytic efficiency and selectivity, and to provide more adequate scientific rules for theoretical studies of biomimetic catalysis.The project is also expected to provide solidder foundation for the application of biomimetic catalysis.

在金属卟啉仿生催化氧气直接氧化体系中，存在催化效率低、选择性不高等问题。我们前期研究表明了共还原剂可架通仿生催化与酶催化的桥梁，使仿生催化氧化真正具有酶催化的特性，即高效、专一及条件温和。进一步研究发现不同结构的共还原剂在仿生催化中还存在对底物的识别过程。通过研究我们初步提出了共还原剂可促进分子氧活化的可能性。但共还原剂在仿生催化过程中的作用机制、对底物的识别机制还尚不明确。 本项目拟在共还原剂-金属卟啉仿生催化底物氧化的基础上，采用原位红外、紫外及电子自旋共振、同位素、量化计算等方法，旨在获得共还原剂与金属卟啉的相互作用、促进分子氧活化、高价金属氧代物形成和传递氧的可靠证据，在此基础上获得共还原剂的底物识别机制，实现在仿生催化氧化中对共还原剂的分子设计。本项目有望揭示共还原剂在提高仿生催化效率及选择性方面的作用机制，为仿生催化的理论研究提供更充分的依据，为仿生催化的应用奠定更扎实的基础。

本项目围绕共还原剂与金属卟啉相互作用机制、共还原剂对分子氧的活化机制，以及高价金属氧代物形成及传递氧的机制等三方面的科学问题，选择金属卟啉仿生催化烷烃羟基化、芳烃侧链氧化、烯烃环氧化、酮类化合物B-V氧化、碳四烷烃氧化为模型反应，阐述共还原剂促进自由基引发及活化分子氧的机制，阐明仿生催化过程中共还原剂对底物的识别机制及传递氧的规律，根据项目预定的方案、路线开展了相关的研究。主要研究情况如下：.（1）针对共还原剂与金属卟啉相互作用机制，以具有-氢的化合物为共还原剂，将仿生催化剂和共还原剂按一定的比例加入烷烃羟基化、丙烯环氧化、环己酮氧化制己内酯等反应体系中，用原位紫外实时检测了金属卟啉特征峰的变化情况，通过原位EPR手段证实了金属卟啉催化剂与共还原剂的作用过程，阐明了金属卟啉促进共还原剂形成自由基的机理和规律。.（2）针对共还原剂对分子氧的活化机制，根据生物氧化中酶催化的作用机制和结构特征，探究了不同共还原剂对氧气的活化过程，采用环己烯、乙酰乙酸乙酯、亚油酸、松香酸和胆固醇等生物质原料为共还原剂，探索了其在仿生催化过程中的作用机理和规律。通过原位紫外、原位红外证实了氧气的活化经历了过氧化物的形成阶段，通过原位表征和实验证实了金属高价活性物种的生成，阐明了共还原剂对分子氧的活化机制。.（3）针对高价金属氧代物形成及传递氧的机制，以仿生催化烯烃环氧化、环己酮B-V氧化制备己内酯的反应为模型，在基于原位紫外和获得高价活性物种的直接证据基础上，重点研究了金属氧代物的形成机理。同时，构建了反应动力学模型，掌握了氧气在氧化中的传递规律以及对反应速率的控制过程。