Self-complementary phosphonate cavitands.

iii-Phosphorylated cavitands incorporating an N-methylpyridinium guest moiety as the fourth bridging unit form supramolecular associations by inclusion of the charged CH(3)N(+)-pyridinium head into a neighboring host cavity. The dimeric association is favored in solution and was characterized by NMR, mass spectrometry, DOSY experiments, and single crystal X-ray analysis.