Naphthalene-2,3-diol–imidazole (1/1)

In the title cocrystal, C10H8O2·C3H4N2, intermolecular O—H⋯O and N—H⋯O hydrogen bonds connect the naphthalene-2,3-diol and imidazole molecules into a two-dimensional supramolecular framework.


Comment
During past decade, the field of molecular co-crystals have received considerable attention, for example, the design, construction, properties and the definition of molecular co-crystals, partly because co-crystallization reactions offer unique opportunities for examining the balance between and structural influence of intermolecular interactions. Recently, a lot of co-crystals containing some organic acids and bases, have been successfully synthesized and characterized by our research group. Especially, co-crystals containing naphthalene-2,7-diol with some organic bases have been prepared and reported (Wang & Tang, 2006;Wang, Tang & Ng, 2006;Wang, Tang & Wan, 2006). A series of supramolecular structures of selfassembly with different motifs have been obtained. There are a few co-crystals about naphthalene-2,3-diol (ndo) as organic acid; some interesting structures have been generated through supramolecular self-assemblies (Fritchie & Johnston, 1975;Wells, et al., 1974). To study a series of co-crystals containing ndo and to further explore its properties, we have selected the structure of the co-crystal, (I), of ndo and imidazole.
A view of the title structure is shown in Fig. 1. The asymmetric unit consists of one independent ndo molecule and one independent molecule of imidazole. In the crystal structure of the title compound, intermolecular O-H···O and N-H···O hydrogen bonds connect naphthalene-2,3-diol molecules and imidazole molecules into a linear ribbon motif, which are further extended to two-dimensional supramolecular framwork through N-H···O hydrogen bonds (Table 1, Fig. 2).

Refinement
All H atoms were located in a difference Fourier map. Carbon-bound hydrogen atoms were positioned geometrically (C-H = 0.93 A °), and were included in the refinement in the riding-model approximation, with U iso (H) = 1.2Ueq(C). Oxygen-and nitrogen-bound hydrogen atoms were restrained and refined independently, with isotropic displacement parameters, giving final O-H and N-H distances in the range 0.895 (5)-0.911 (9), 0.897 (10) A °, respectively.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.