Quinolinium 8-hydroxy-7-iodoquinoline-5-sulfonate 0.8-hydrate

In the crystal structure of the title hydrated quinolinium salt of ferron (8-hydroxy-7-iodoquinoline-5-sulfonic acid), C9H7N+·C9H5INO4S−·0.8H2O, the quinolinium cation is fully disordered over two sites (occupancy factors fixed at 0.63 and 0.37) lying essentially within a common plane and with the ferron anions forming π–π-associated stacks down the b axis [minimum ring centroid separation = 3.462 (6) Å]. The cations and anions are linked into chains extending along c through hydroxy O—H⋯O and quinolinium N—H⋯O hydrogen bonds to sulfonate O-atom acceptors which are also involved in water O—H⋯O hydrogen-bonding interactions along b, giving a two-dimensional network.

In the crystal structure of the title hydrated quinolinium salt of ferron (8-hydroxy-7-iodoquinoline-5-sulfonic acid), C 9 H 7 N + Á-C 9 H 5 INO 4 S À Á0.8H 2 O, the quinolinium cation is fully disordered over two sites (occupancy factors fixed at 0.63 and 0.37) lying essentially within a common plane and with the ferron anions forming --associated stacks down the b axis [minimum ring centroid separation = 3.462 (6) Å ]. The cations and anions are linked into chains extending along c through hydroxy O-HÁ Á ÁO and quinolinium N-HÁ Á ÁO hydrogen bonds to sulfonate O-atom acceptors which are also involved in water O-HÁ Á ÁO hydrogen-bonding interactions along b, giving a two-dimensional network.

Experimental
The title compound was synthesized by heating a solution containing 1 mmol of 8-hydroxy-7-iodoquinoline-5-sulfonic acid (ferron) and 1 mmol of quinoline in 50 ml of 50% ethanol-water for 10 min under reflux. After concentration to ca. 40 ml, partial room temperature evaporation of the hot-filtered solution gave yellow flat prisms of the title compound (m.p. 460.6-462.3 K) from which a specimen was cleaved for the X-ray analysis.

Refinement
Hydrogen atoms on the water molecule and the hydroxyl group were located in a difference-Fourier synthesis but were subsequently allowed to ride in the refinement with U iso (H) = 1.5U eq (O). Other H-atoms were included in the refinement in calculated positions with N-H = 0.86 Å or C-H = 0.93 Å and were also treated as riding, with U iso (H) = 1.2U eq (C).
The site occupancy of the water molecule was determined as 0.801 (12) and was subsequently fixed as 0.80. The supplementary materials sup-2 . E68, o3349 quinolinium cation was completely disordered laterally within a common plane and the minor component (B) was subsequently located and its occupancy determined as 0.373 (14). Because of the instability in the anisotropic displacement parameters for both components, these were refined isotropically. The maximum difference peak was 0.64 e Å -3 1.07 Å from I7.

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles 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 R-factors(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.