Do pentaurea calix[5]arenes form hydrogen bonded dimeric capsules?

Calix[5]arenes substituted at their wider rim by five urea residues do not form hydrogen bonded dimeric capsules in aprotic, apolar solvents, in contrast to their calix[4]arene analogs, although molecular dynamic simulations predict very similar geometrical parameters for both cases. The reason for this different behavior is most probably the higher energetic cost which must be paid to arrange the calix[5]arene skeleton in the C-5-symmetrical conformation required for the dimerization