摘要
锰卟啉作为仿生催化剂催化活化烃类饱和C—H键的反应中,锰卟啉高价金属氧化物和氢氧化物均有活化C—H键的能力。采用密度泛函理论对锰卟啉高价金属氧化物及氢氧化物活化甲苯α-C—H键进行研究,考察影响其活性的本质因素。结果发现,锰卟啉高价金属氧化物和氢氧化物的单重态由于没有氧自由基特征而不具备活化甲苯α-C—H键的能力。高自旋锰卟啉金属氧化物活化甲苯α-C—H键能力较强,金属氢氧化物的活化能力较弱。过渡态结构的形变能和结合能共同决定了活化能的大小,且形变能是影响其活性的关键因素。
In the catalytic oxidation of saturated C—H bond of hydrocarbons by manganese porphyrin as biomimetic catalyst,both high-valence Mn-oxo porphyrin and Mn-hydroxo porphyrin have the ability to activate C—H bond.The activation of toluene α-C—H bond by high-valence Mn-oxo porphyrin and Mn-hydroxo porphyrin were investigated using density functional theory,and the key factors affecting the activity were investigated.The results show that the singlet state structures of Mn-oxo porphyrin and Mnhydroxo porphyrin have no ability to activate the C—H bond due to the absence of oxyl radical. The high spin states of Mn-oxo porphyrin have the higher activity and Mn-hydroxo porphyrin has the lower activity to activate toluene α-C—H bond.The activation energy was determined by interaction energy and distortion energy.Distortion energy is the key factor affecting the activity of Mnoxo porphyrin and Mn-hydroxo porphyrin.
引文
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