Hexameric and Pentameric Slipped-Cofacial Dimers: Toward an Artificial Light-Harvesting Complex

Abstract

[structure: see text] We prepared a zinc complex of bis(1-methylimidazolyl)-m-gable porphyrin. The automatically assembled coordinate species showed a complex mixture of wide molecular weight distributions accompanied with assemblies of specific assembly numbers. When this zinc complex was once dissociated by the addition of methanol and reorganized again by elimination of the methanol under high-dilution conditions in chloroform to facilitate intramolecular coordinate structure formation, two convergent assemblies were obtained through analysis by gel permeation chromatography. These assemblies gave round-shaped particles on solid substrates by probe microscopies (atomic force and scanning tunneling microscopies). These two components were separated by GPC and evidence from small-angle X-ray scattering measurements in solution with synchrotron radiation was consistent with hexameric and pentameric macrorings of the gable porphyrin. The porphyrin macrorings did not show any fluorescence quenching by assembly formation, and we anticipate that the macrorings of gable porphyrins represent a good model for an artificial light-harvesting complex.