[Gallium(III) protoporphyrin IX]2: A Soluble Diamagnetic Model for Malaria Pigment

Gallium­(III) protoporphyrin IX forms a dimeric propionate-bridged dimer, 2, that is a soluble diamagnetic analogue of hematin anhydride. The single-crystal structure of 2 corresponds to a nondisordered inversion-symmetric dimer similar to malaria pigment but, unlike it, has a six-coordinate metal and an intraporphyrin rather than an interporphyrin hydrogen bond. NMR NOE correlations demonstrate the presence of the propionate linkage in solutions with pyridine. Taken together, this is the first single-crystal X-ray diffraction study of a propionate-linked dimer as found in malaria pigment and the first evidence for its presence in solution.

镓(III)原卟啉IX（Gallium(III) protoporphyrin IX）可形成丙酸桥联二聚体2，该化合物为无水血红素（hematin anhydride）的可溶性抗磁性类似物。二聚体2的单晶结构为无无序的反演对称二聚体，其结构与疟色素（malaria pigment）相似，但二者存在差异：该二聚体拥有六配位金属中心，且其氢键为卟啉环内氢键（intraporphyrin hydrogen bond）而非卟啉环间氢键（interporphyrin hydrogen bond）。核磁共振核Overhauser效应（NMR NOE）相关性实验证实，在含吡啶（pyridine）的溶液中存在该丙酸桥联结构。综上，本研究首次针对疟色素中存在的丙酸桥联二聚体开展单晶X射线衍射（single-crystal X-ray diffraction）研究，同时首次为该结构在溶液中的存在提供了实验证据。