对位取代四苯基卟啉铁(Ⅲ)的轴向配位快速反应动力学研究

Kinetic Study of Axial Coordination of Para-Substituted (Tetraphenylporphinato) Iron(Ⅲ) Chloride

用Union Giken RA-401停流分光光度计对丙酮溶剂中咪唑（Im）与对位取代四苯基卟啉铁（Ⅲ）（Fe（p-X）TPPCl X=Cl,H,CH3,OCH3）的轴向配位快速反应动力学进行了研究.提出了反应机理.以CA-033E微机对实验数据进行处理,得到似平衡步的平衡常数K和速控步的速率常数k,并算出了似平衡步的△H、△S以及速控步活化参数△日≠、△S≠.发现△H、△S、△H≠、AS≠、InK、Ink分别与Hammett取代常数σ呈直线关系;AH≠和△S≠存在等动力学关系.

A kinetic study is reported for the axial coordination of imidazole(Im) .with para-substituted (tetraphenylporphinato)-iron(Ⅲ) chloride [Fe(p-X)TPPCl; X=C1, H, CH3, OCH3] in acetone by means of Union Giken RA-401 stopped-folw spectrophotometer. The mechanism is postulated as follows: (1) (2)The experimental data were treated with CA-033E micro computer. The equilibrium constant (K) of the preequilibrium step(l) and the rate constant(k) of the rate determining step(2) were obtained. The standard enthalpy △H and standard entropy △S of step ( 1 ) , and the activation parameters △H and △S of step (2) were calculated. It was found that linear relationships exists between the following pairs : △H and the Hammett constant δ; △S and δ ; △H and δ ; △S and δ ; lnK and δ; lnk and 6. The isokinetic relationship between △H and △S was also found .