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In bis(2-carboxypyridinium) hexafluorosilicate, 2C(6)H(6)NO(2)+.SiF6(2-), (I), and bis(2-carboxyquinolinium) hexafluorosilicate dihydrate, 2C(10)H(8)NO(2)+.SiF6(2-).2H2O, (II), the Si atoms of the anions reside on crystallographic centres of inversion. Primary inter-ion interactions in (I) occur via strong N-H...F and O-H...F hydrogen bonds, generating corrugated layers incorporating [SiF6](2-) anions as four-connected net nodes and organic cations as simple links in between. In (II), a set of strong N-H...F, O-H...O and O-H...F hydrogen bonds, involving water molecules, gives a three-dimensional heterocoordinated rutile-like framework that integrates [SiF6](2-) anions as six-connected and water molecules as three-connected nodes. The carboxyl groups of the cation are hydrogen bonded to the water molecule [O...O = 2.5533 (13) A], while the N-H group supports direct bonding to the anion [N...F = 2.7061 (12) A].

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.

X-ray data were obtained for the monoclinic polymorph of rac-5,7,7,12,12,14-hexamethyl-1,4,8,11-tetraazoniacyclotetradecane bis(hexafluorogermanate) tetrahydrate, (C(16)H(40)N(4))[GeF(6)](2).4H(2)O. The tetraaza-macrocyclic cations lie across inversion centers in space group P2(1)/c. Water molecules and [GeF(6)](2-) anions form zigzag chains, which alternate in a three-dimensional network with the macrocyclic cations. The structure is sustained by multiple hydrogen bonds.