2,9-Dimethyl-1,10-phenanthrolin-1-ium 2,4,5-tri-carb-oxy-benzoate 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-tri-carb-oxy-benzoate anion. In the anion, the mean planes of the protonated carboxyl-ate 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 carboxyl-ate group forms a dihedral angle of 10.6 (5)° with the benzene ring. In the crystal, the anions are involved in carb-oxy-lic acid O-H⋯Ocarbox-yl 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 mol-ecules reside between the anion layers and are connected to the anions via N-H⋯Owater and Owater-H⋯Ocarbox-yl hydrogen bonds. An intra-molecular O-H⋯O hydrogen bond is also observed in the anion.