Molecular Recognition in the Axial Ligation of Pyridines to Zinc Complexes of Tetraarylporphyrin Atropisomers

合成了（o-取代-苯基）- m-（苯基）- n -卟啉（m+n=4）型四芳基卟啉反旋异构体，并进行了色谱分离和重结晶纯化，系统地研究了旋转异构体的分子识别。在邻硝基和邻甲氧基取代基的情况下，可以进行对映异构体的分离，这表明这些取代基具有足够大的体积，可以阻止芳基环围绕卟啉平面旋转。这种情况为金属卟啉平面两侧的轴向配体提供了不对称的分子空间。在两年的研究项目中，我们获得了9种纯锌配合物m=0 ~ m=3分数的邻硝基取代化合物。本报告（日文）系统地研究了吡啶和尼古丁与这9种锌卟啉的轴向配位。光谱滴定法测定的平衡常数随阻碍硝基取代数的增加而增大。用x射线法测定了一些锌配合物的晶体结构和分子结构。配合物的立体化学结构显示5配位锌卟啉与轴向吡啶配位在卟啉平面的“受阻”侧。结果表明，周围硝基取代基包围的四芳基卟啉轴向配位空间对吡啶的连接具有亲和作用，因此配体分子能够识别卟啉平面上形成的配位空间的形状。

Various tetraarylporphyrin atropisomers of the (o-substituted-phenyl)_m-(phenyl)_nporphyrin (m+n=4) type have been synthesized, separated chromatographically, and purified by the recrystallization in order to investigate molecular recognition of the rotational isomers systematically. In the cases of o-nitro- and o-methoxo- substituents, separation of atropisomers could be performed as is showing that these substituents have large bulk enough to hinder the rotation of aryl ring around the porphyrin plane. This situation affords unsymmetrical molecular spaces for the axial ligand on each side of the metalloporphyrin plane. During two years of this research project, we obtained nine pure species of the zinc complex of m=0 to m=3 fraction of o-nitro substituent compounds. This report (in Japanese) deals with a systematic study of the axial coordination of pyridine and nicotine to these nine zincporphyrins. The equilibrium constants determined by the spectral titration methods become larger accordinng to the increase of number of the hindered nitro substitution. The crystal and molecular structures of some Zn complexes have been determined by the X-ray method.The stereochemistry of the complexes shows 5-coordinate zincporphyrins with an axial pyridine coordinating to the "hindered" side of the porphyrin plane. It is concluded that the axial coordination space surrounded with peripheral nitro substituents of tetraarylporphyrins works affinitively toward the pyridine ligation, thus the ligand molecules recognize the shape of the coordination space developed on the porphyrin plane.