Hydrogen-bonding adducts of benzenepolycarboxylic acids with N,N-dimethylformamide:: benzene-1,4-dicarboxylic acid N,N-dimethylformarnide disolvate, benzene-1,2,4,5-tetracarboxylic acid N,N-dimethylformarnide tetrasolvate and benzene-1,2,3-tricarboxylic acid N,N-dimethylformamide disolvate monohydrate

The N,N-dimethylformamide (DMF) solvates of terephthalic acid, H(2)TA.2DMF (C8H6O6.2C(3)H(7)NO), pyromellitic acid, H(4)PMA.4DMF (C10H6O8.4C(3)H(7)NO), and hemimellitic acid, H(3)HMA.2DMF.H2O (C9H6O6.2C(3)H(7)NO.H2O), are reported. The DMF solvate of terephthalic acid is centrosymmetric, containing one complete formula unit in the asymmetric unit. Both carboxylic acid groups hydrogen bond to a DMF molecule via an R-2(2)(7) O-H...O/C-H...O motif. Discrete H(2)TA.2DMF units are observed. The DMF solvate of pyromellitic acid is centrosymmetric and the asymmetric unit contains half a formula unit. One of the unique carboxylic acid groups forms an R-2(2)(7) motif with a DMF molecule, while the other forms a linear O-H...O hydrogen bond to the second unique DMF molecule. Discrete H(4)PMA.4DMF units are observed. The DMF solvate of hemimellitic acid is noncentrosymmetric and includes a molecule of water per formula unit. Both DMF molecules form an R-2(2)(7) motif with the two outer carboxylic acid groups of HMA. A one-dimensional ladder structure is formed via hydrogen bonding between the central carboxylic acid group and the water molecules. The carboxylic acid R-2(2)(8) head-to-tail motif is not observed in any of these examples. The inclusion of DMF thereby has the effect of limiting the dimensionality of the structures.