四吡啶基卟啉质子化结构变化研究Ⅱ.m-甲基吡啶基的取代基效应

Studies on the Structural Change of the N-Protonated Tetrapyridylporphine Ⅱ.The Effects of the Substituting Group meso-(p-Methylpyridyl)

卟啉衍生物对嵌入并堆积在DNA螺旋中具有高选择性 .为考察m -甲基吡啶取代基对质子化卟啉结构的影响 ,在m -四吡啶基卟啉研究的基础上 ,用半经验的AM1MO方法 ,并进行合理的对称性限制 ,计算了m -四甲基吡啶卟啉 (TmPyPH2 4 +)及其质子化二酸 (TmPyPH4 6 +)的几种可能的构型 .结果表明 ,由于m -甲基吡啶的影响 ,在质子化过程中结构和键电荷布居有明显变化 ;前沿分子轨道具有与四吡啶基情形相反的变化趋势 。

Porphyrin derivatives have sensitive selectivity to molecular intercalation and aggregation in DNA helix. On the basis of the study of tetrapyridylporphine, in order to investigate the effects of meso-(p-methylpyridyl) to the structure of N-protonated porphyrin, the geometries of meso-tetrakis(p-methylpyridyl)porphyrin (TmPyPH_2 4+)and its diacid(TmPyPH_4 6+) were calculated by using AM1 MO method under certain symmetry restriction. The results show that in the protonation process, because of the effect of meso-(p-methylpyridyl), the changes of the structure and bond charge population are obvious; the frontier molecular orbitals have opposite change trend with the case of meso-yridyl,the rapid exchanges of inner hydrogens of the protonated diacid with solvent protons become more difficult.