A new phase of 7,16-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane, and 7,16-dibenzyl-1,4,10,13-tetraoxa-7,16-diazoniacyclooctadecane bis(tetrafluoroborate) monohydrate, both determined at 123 K.

7,16-Dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane, C26H38N2O4, (I), crystallizes in space group P2(1)/c, with two independent molecules adopting different conformations. The 'free' crowns adopt a typical 'arallelogram' shape, in which two methylene groups are turned inward toward the center of the ring and the benzyl groups splay out from the ring. In 7,16-dibenzyl-1,4,10,13-tetraoxa-7,16-diazoniacyclooctadecane bis(tetrafluoroborate) monohydrate, C26H40N2O4(2+).2BF4-.H2O, (II), the macrocycle is centrosymmetric, and the protonated N atoms adopt an endo-endo orientation that is stabilized by a bifurcated N-H...O hydrogen bond, where the O atoms of the macrocycle act as hydrogen-bond acceptors. The phenyl groups of the benzyl side arms are turned above and below the macrocycle; C-H...pi interactions between the phenyl substituents and two macrocyclic methylene H atoms govern the overall conformation of the macrocycle. Bridging tetrafluoroborate anions link the macrocyclic cations via weak C-H...F hydrogen bonds into channels running along [100], which are filled by the weakly hydrogen-bonded water molecules.