四苯基卟啉衍生物质子化热力学

Study on Overall Protonation Constants of Tetraphenylporphyrin Derivatives

用光度法测得六种四苯基卟啉衍生物的表观质子化常数及质子化热力学函数，并用半经验量子化学计算方法 PM3 计算了卟啉环中两个氮原子（＝ N－）的净电荷，探讨了取代基的电子效应及空间效应对质子化常数的影响。

The overall protonation constants of six tetraphenylporphyrin derivatives were determined by spectrophotometric methods. The changes of standard molar enthalpy Delta H-r(m)circle minus and the changes of standard molar entropy Delta S-r(m)circle minus of the reactions were obtained from the plots of lnK(circle minus) vs 1/T. The porphyrin molecules were calculated by using semiempirical PM3 method. The influence of electron effect and steric hindrance of substituting group on overall protonation constants was discussed. Experimental data and theoretical discussion showed that the degree of porphyrin protonation depend on electron and steric effect. The values of the protonation constants are increased as increasing donor conjugate effect, while steric hindrance of substituting group reduces the constants.