Key points are not available for this paper at this time.
There is more than one way to assemble the two halves of a tethered, urea-substituted calix4arene dimer (shown schematically): formation of unimolecular capsules (far left), dimers, or oligomers. By combination of NMR spectroscopy and electrospray mass spectrometry, a hexamethylene spacer was shown to be exactly right to permit the preferential formation of a unimolecular capsule under inclusion of solvent or other guest molecules.
Brody et al. (Tue,) studied this question.