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

本文合成了邻取代苯基间苯基n卟啉（m+n=4）型四芳基卟啉阻转异构体，用色谱分离和重结晶纯化，系统地研究了它们的分子识别。在邻硝基-和邻甲氧基-取代基的情况下，阻转异构体的分离可以进行，因为这表明这些取代基具有足够大的体积来阻碍芳基环围绕卟啉平面的旋转。这种情况提供了不对称的分子空间的轴向配体上的金属卟啉平面的每一侧。经过两年的研究，我们获得了9种纯的邻硝基取代化合物的m=0至m=3级分的锌配合物。本文系统地研究了吡啶和烟碱与这九种锌卟啉的轴向配位作用。用光谱滴定法测定的平衡常数随受阻硝基取代数的增加而增大。用X射线衍射法测定了几种锌配合物的晶体和分子结构，其立体化学为5配位的锌卟啉，轴向吡啶配位在卟啉平面的“受阻”侧。结果表明，四芳基卟啉的轴向配位空间被周边硝基取代基所包围，对吡啶连接反应具有亲合力，因此配体分子能够识别卟啉平面上的配位空间的形状。

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.