2,9-Dimethyl-1,10-phenanthrolin-1-ium 2,4,5-tricarboxybenzoate monohydrate

In the preparation of the title hydrated salt, C14H13N2 +·C10H5O8 −·H2O, a proton has been transfered to the 2,9-dimethyl-1,10-phenanthrolinium cation, forming a 2,4,5-tricarboxybenzoate anion. In the anion, the mean planes of the protonated carboxylate groups form dihedral angles of 11.0 (5), 4.4 (5) and 80.3 (4)° with the benzene ring to which they are attached. The mean plane of the deprotonated carboxylate group forms a dihedral angle of 10.6 (5)° with the benzene ring. In the crystal, the anions are involved in carboxylic acid O—H⋯Ocarboxyl hydrogen bonds, generating a two-dimensional network parallel to (001) containing R 4 4(28) and R 4 4(32) motifs. The 2,9-dimethyl-1,10-phenanthrolinium cations and water molecules reside between the anion layers and are connected to the anions via N—H⋯Owater and Owater—H⋯Ocarboxyl hydrogen bonds. An intramolecular O—H⋯O hydrogen bond is also observed in the anion.

In the preparation of the title hydrated salt, C 14 H 13 N 2 + Á-C 10 H 5 O 8 À ÁH 2 O, a proton has been transfered to the 2,9dimethyl-1,10-phenanthrolinium cation, forming a 2,4,5-tricarboxybenzoate anion. In the anion, the mean planes of the protonated carboxylate groups form dihedral angles of 11.0 (5), 4.4 (5) and 80.3 (4) with the benzene ring to which they are attached. The mean plane of the deprotonated carboxylate group forms a dihedral angle of 10.6 (5) with the benzene ring. In the crystal, the anions are involved in carboxylic acid O-HÁ Á ÁO carboxyl hydrogen bonds, generating a two-dimensional network parallel to (001) containing R 4 4 (28) and R 4 4 (32) motifs. The 2,9-dimethyl-1,10-phenanthrolinium cations and water molecules reside between the anion layers and are connected to the anions via N-HÁ Á ÁO water and O water -HÁ Á ÁO carboxyl hydrogen bonds. An intramolecular O-HÁ Á ÁO hydrogen bond is also observed in the anion.
This work was supported by the Scientific Research Foundation of Nanjing College of Chemical Technology (grant No. NHKY-2013-10).

Refinement
The H atoms bonded to C atoms were were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.93, 0.96 Å; U iso (H) = 1.2U eq (C) or 1.5U eq (C methyl )). The H atoms bound to N and O were placed in calculated positions with N-H = 0.86 Å, O-H = 0.82 Å and refined with U iso (H) = 1.2U eq (N) and U iso (H) = 1.5U eq (O). The precision of the structure is slightly lower than normal as reflected in the R-factors. We attempted to use serveral crystals but the crystal used to collect the data herein was the best quality avaiable.

Figure 1
The asymmetric unit of (I), showing displacement ellipsoids drawn at the 30% probability level. An intramolecular hydrogen bond is shown as a dashed line.  Part of the crystal structure of (I) showing layers parallel to (0 0 1). Hydrogen bonds are represented by dashed lines. The 2,9-dimethyl-1,10-phenanthrolinium cations and the water molecules have been omitted for clarity.

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 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.