Porphyrin–Polyyne [3]- and [5]Rotaxanes

Porphyrin–polyyne [3]- and [5]­rotaxanes have been synthesized by condensing aldehyde–rotaxanes with pyrrole or dipyrromethane. The crystal structure of a [3]­rotaxane shows that the macrocycles adopt compact conformations, holding the hexaynes near the porphyrin core, and that the phenanthroline units form intermolecular π-stacked dimers in the solid. Fluorescence spectra reveal singlet excited-state energy transfer from the threaded hexayne to the porphyrin, from the phenanthroline to the porphyrin, and from the phenanthroline to the hexayne.