Synthesis and crystal structures of 5,17-dibromo-26,28-dihydroxy-25,27-dipropynyloxycalix[4]-arene, 5,17-dibromo-26,28-dipropoxy-25,27-dipropynyloxycalix[4]arene and 25,27-bis(2-azidoethoxy)-5,17-dibromo-26,28-dihydroxycalix[4]arene.

The calixarenes, 5,17-dibromo-26,28-dihydroxy-25,27-dipropynyloxycalix[4]- arene (C₃₄H₂₆Br₂O₄, 1), 5,17-dibromo-26,28-dipropoxy-25,27-dipropynyloxycalix[4]arene (C₄₀H₃₈Br₂O₄, 2) and 25,27-bis(2-azidoethoxy)-5,17-dibromo-26,28-dihydroxycalix[4]arene (C₃₂H₂₈Br₂N₆O₄, 3) possess a pinched cone molecular shape for 1 and 3, and a 1,3-alternate shape for compound 2. In calixarenes 1 and 3, the cone conformations are additionally stabilized by intra-molecular O-H⋯O hydrogen bonds, while in calixarene 2 intra-molecular Br⋯Br inter-actions consolidate the 1,3-alternate mol-ecular conformation. The dense crystal packing of the cone dialkyne 1 is a consequence of π-π, C-H⋯π and C-H⋯O inter-actions. In the crystal of the diazide 3, there are large channels extending parallel to the c axis, which are filled by highly disordered CH₂Cl₂ solvent mol-ecules. Their contribution to the intensity data was removed by the SQUEEZE procedure that showed an accessible void volume of 585 Å3 where there is room for 4.5 CH₂Cl₂ solvent mol-ecules per unit cell. Rigid mol-ecules of the 1,3-alternate calixarene 2 form a columnar head-to-tail packing parallel to [010] via van der Waals inter-actions, and the resulting columns are held together by weak C-H⋯π contacts. [ABSTRACT FROM AUTHOR]