Phenazin-5-ium hydrogen sulfate monohydrate

The crystal structure of the title salt, C12H9N2 +·HSO4 −·H2O, comprises inversion-related pairs of phenazinium ions linked by C—H⋯N hydrogen bonds. The phenazinium N—H atoms are hydrogen bonded to the bisulfate anions. The bisulfate anions and water molecules are linked by O—H⋯O hydrogen-bonding interactions into a structural ladder motif parallel to the a axis.

The crystal structure of the title salt, C 12 H 9 N 2 + ÁHSO 4 À ÁH 2 O, comprises inversion-related pairs of phenazinium ions linked by C-HÁ Á ÁN hydrogen bonds. The phenazinium N-H atoms are hydrogen bonded to the bisulfate anions. The bisulfate anions and water molecules are linked by O-HÁ Á ÁO hydrogen-bonding interactions into a structural ladder motif parallel to the a axis.
Perhaps the most interesting aspect of the structure results from the hydrogen bonding between the bisulfate anions and the solvent water molecule. This results in the formation of a ladder motif that runs parallel to the a-axis (see Figure 3).
Each bisulfate ion serves as a hydrogen bond donor to one water molecule and a hydrogen bond acceptor from a second water molecule forming the rails of the ladder, of form C 2 2 (6). The rungs are formed via a second water-donor/bisulfateacceptor pair, which generates rings within the ladder structure (two rungs and two rail sections in each ring), R 4 4 (12). There are two chemically different rings formed in this case since one involves rail sections with water molecules serving as the hydrogen bond donor and the other involves the bisulfate ion serving as the hydrogen bond donor.

Experimental
Phenazine was dissolved methanol (90 ml) to which 40% aqueous sulfuric acid (2.5 ml) had been added. Small, prismatic, ruby red crystals formed over the course of two months of slow evaporation at room temperature.

Refinement
All H-atoms bound to carbon were refined using a riding model with d(C-H) = 0.93 Å, U iso =1.2U eq (C). Hydrogen atoms bonded to oxygen or nitrogen atoms were located in a difference map and their positions refined using fixed isotropic U values. There are two Level-B warnings in the checkCIF file for short intermolecular H···H distances. These result from the very strong hydrogen bond between the bisulfate ion and the solvent water molecule (d D···A = 2.5223 (16) Å.

Computing details
Data collection: CrysAlis PRO (Agilent, 2011); cell refinement: CrysAlis PRO (Agilent, 2011); data reduction: CrysAlis PRO (Agilent, 2011); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008)    Packing diagram showing the structure of the ladder motif formed by hydrogen bonding between the bisulfate ions and water molecules. Details of the hydrogen bonding may be found in Table 1. 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.