Unusual host–guest π-arene ⋯ H bonding in a ‘hooded’ cavitand: the first solid-state structure of a calix[4]resorcinarene with underivatised hydroxy groups

Treatment of phenylcalix[4]resorcinarene 1 with dipropylamine and paraformaldehyde leads to the formation of a deep cleft cavitand 2, in which the cavity is extended by a collar of exquisite intramolecular donor–acceptor hydrogen bonding networks which all proceed in the same direction around the upper rim imparting chirality on the individual cavitands; the amine groups involvement in intramolecular hydrogen bonding draws the N-alkyl substituents inward to form an encapsulating ‘hood’ over an included CH2Cl2 guest molecule.