8-Hydroxyquinolin-1-ium nitrate

In the title salt, C9H8NO+·NO3 −, the quinoline ring system is essentially planar with a maximum deviation of 0.043 (1) Å. In the crystal, an R 2 2(7) ring motif is formed by intermolecular N—H⋯O and C—H⋯O hydrogen bonds between the cation and the anion. In addition, intermolecular O—H⋯O and C—H⋯O hydrogen bonds link the two ions, generating an R 2 2(8) ring motif. These sets of ring motifs are further linked into a ribbon along the a axis via intermolecular C—H⋯O hydrogen bonds.

In the title salt, C 9 H 8 NO + ÁNO 3 À , the quinoline ring system is essentially planar with a maximum deviation of 0.043 (1) Å . In the crystal, an R 2 2 (7) ring motif is formed by intermolecular N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds between the cation and the anion. In addition, intermolecular O-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds link the two ions, generating an R 2 2 (8) ring motif. These sets of ring motifs are further linked into a ribbon along the a axis via intermolecular C-HÁ Á ÁO hydrogen bonds.
Quinolines and their derivatives are very important compounds because of their wide occurrence in natural products (Morimoto et al., 1991;Michael, 1997) and biologically active compounds (Markees et al., 1970;Campbell et al., 1988). Herein we report the synthesis of 8-hydroxyquinolin-1-ium nitrate.
The asymmetric unit of the title compound ( Fig. 1) consists of one 8-hydroxyquinolin-1-ium cation (C1-C10/N1/N2) and one nitrate anion (O2-O4/N2). One proton is transferred from the hydroxyl group of nitric acid to the atom N1 of 8-hydroxyquinoline during the crystallization, resulting in the formation of salt. The quinoline ring system (C1-C9/N1) is approximately planar with a maximum deviation of 0.043 (1) Å at atom C4. Bond lengths (Allen et al., 1987) and angles are within the normal ranges and are comparable to the related structures (Loh et al., 2010a,b,c,d).

Experimental
A few drops of nitric acid were added to a hot methanol solution (20 ml) of 8-hydroxyquinoline (29 mg, Merck) which had been warmed over a magnetic stirrer hotplate for a few minutes. The resulting solution was allowed to cool slowly to room temperature. Crystals of the title compound appeared after a few days.

Refinement
Atoms H1N1 and H1O1 were located from the difference Fourier map and were refined freely [N-H = 0.874 (18)

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. 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.