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.