金属卟啉自氧化反应研究

金属卟啉能在温和条件下催化PhIO、H_2O_2和NaClO等氧化剂对烷烃和烯烃的单充氧反应,但在这些氧化剂存在下,金属卟啉本身存在自毁灭现象而失去催化活性,关于金属卟啉的自毁灭现象,尚无文献详细报道,我们发现,这一现象实际上是金属卟啉在氧化剂作用下发生的自氧化反应,为了系统地研究并控制金属卟啉的自氧化反应,我们合成了9种不同结构的金属卟啉(图1),从动力学上对它们的自氧化反应进行了考察,研究发现,铁和铬卟琳的自氧化反应在动力学上为二级反应,锰卟啉为一级反应;卟啉环上的取代基,无论是吸电子基还是供电子基都使反应速度加快;但在反应体系中加入中性有机配体,能抑制金属卟啉的自氧化速度,氧化剂的能力越强,反应速度越快;溶剂的极性越小,反应速度越慢。

Studies on the Self-Oxidation of Metal loporphyrins

We synthesized 9 kinds of metalloporphyrins and studied systematically the kinetic properties of their self-oxidation during the biomimetic oxidation of hydrocarbons. It has been proved that the kinetic properties of the self-oxidation of the metalloporphyrins depend on the metal ions bonded with the porphyrins. The reaction is second order for ironporphyrins or chro-moporphyrins, and first order for manganoporphyrins. It is shown from the results that the rateof the reaction is much related to the structure of the porphyrins--the substituents on the por-phyrin ring and the axial ligandsr the properties of the oxidants and the reaction mediums, and is abated by adding some neutral organic ligands to the reaction system.