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 (C 34 H 26 Br 2 O 4 , 1 ), 5,17-dibromo-26,28-dipropoxy-25,27-dipropynyloxycalix[4]arene (C 40 H 38 Br 2 O 4 , 2 ) and 25,27-bis(2-azidoethoxy)-5,17-dibromo-26,28-dihydroxycalix[4]arene (C 32 H 28 Br 2 N 6 O 4 , 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 intramolecular O—H...O hydrogen bonds, while in calixarene 2 intramolecular Br...Br interactions consolidate the 1,3-alternate molecular conformation. The dense crystal packing of the cone dialkyne 1 is a consequence of π–π, C—H...π and C—H...O interactions. In the crystal of the diazide 3 , there are large channels extending parallel to the c axis, which are filled by highly disordered CH 2 Cl 2 solvent molecules. Their contribution to the intensity data was removed by the SQUEEZE procedure that showed an accessible void volume of 585 Å 3 where there is room for 4.5 CH 2 Cl 2 solvent molecules per unit cell. Rigid molecules of the 1,3-alternate calixarene 2 form a columnar head-to-tail packing parallel to [010] via van der Waals interactions, and the resulting columns are held together by weak C—H...π contacts.