1,1'-[(1,3-Dihydroxypropane-2,2-diyl)dimethylene]dipyridinium bis-(hexa-fluoro-phosphate).

The title compound, C(15)H(20)N(2)O(2) (2+)·2PF(6) (-), was prepared by anion exchange of two bromide ions in the ionic liquid 2,2'-bis-(pyridinium-1-ylmeth-yl)-propane-1,3-diol dibromide with potassium hexa-fluoro-phosphate. The two pyridine rings are planar (r.m.s. deviations = 0.008 and 0.00440 Å) and make a dihedral angle of 44.0 (2)°. Intermolecular O-H⋯F and C-H⋯F interactions occur. The four F atoms in each anion were refined as disordered over two sets of sites with an occupancy ration of 0.700 (19):0.300 (19).

3,3'-Dimethyl-1,1'-(butane-1,4-di-yl)diimidazolium bis-(tetra-fluoro-borate).

The title compound, C(12)H(20)N(4) (2+)·2BF(4) (-), was prepared by the anion exchange of a dibromide ionic liquid with sodium tetra-fluoro-borate. The asymmetric unit contains one half of the imidazolium cation, which lies about an inversion centre at the mid-point of the central C-C bond of the linking butyl chain. The two planar imidazole rings (r.m.s. deviation = 0.0013 Å) are strictly parallel and separated by 2.625 (7) Š[vertical distance between the centroids of two imidazole rings], giving the mol-ecule a stepped appearance. In the crystal structure, inter-molecular C-H⋯F hydrogen bonds link the cations and anions, generating a three-dimensional network.

3,3'-Dimethyl-1,1'-[(1,3-dihy-droxy-propane-2,2-di-yl)dimethyl-idene]diimidazolium bis-(hexa-fluoro-phosphate).

The title compound, C(13)H(22)N(4)O(2) (2+)·2PF(6) (-), was prepared by the anion exchange of the dibromide ionic liquid with potassium hexa-fluoro-phosphate. The two imidazole rings are each planar (r.m.s. deviations = 0.0016 and 0.0060 Å) and make a dihedral angle of 45.3 (18)°. Intra-molecular O-H⋯F hydrogen bonds occur. Inter-molecular C-H⋯F, O-H⋯O and C-H⋯O hydrogen bonds stabilize the crystal structure.

3,3-Dimethyl-1,1-(propane-1,3-di-yl)diimidazol-1-ium tetra-bromido-cadmate(II).

The title compound, (C(11)H(18)N(4))[CdBr(4)], was prepared by an anion exchange. The dihedral angle between the two planar imidazolium rings in the cation is 74.4 (4)°. The crystal packing is stabilized by weak inter-molecular C-H⋯Br hydrogen bonds between the cation and the tetrahedral anion, building up a three-dimensionnal network.

N-(2-Hydroxy-ethyl)-1,8-naphthalimide.

In the mol-ecule of the title compound, C(14)H(11)NO(3), the naphthalimide ring system is nearly planar (r.m.s. deviation 0.0139 Å). In the crystal structure, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules into centrosymmetric dimers forming R(2) (2)(14) ring motifs. π-π contacts between the naphthalimide rings [centroid-centroid distances = 3.648 (3), 3.783 (3), 3.635 (3), 3.722 (3) and 3.755 (3) Å] may further stabilize the structure.