Hydro­gen‐bonding adducts of benzene­poly­carboxyl­ic acids with N , N ‐di­methyl­form­amide: benzene‐1,4‐di­carboxyl­ic acid N , N ‐di­methyl­form­amide disolvate, benzene‐1,2,4,5‐tetra­carboxyl­ic acid N , N ‐di­methyl­form­amide 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 (C 8 H 6 O 6 ·2C 3 H 7 NO), pyromellitic acid, H 4 PMA·4DMF (C 10 H 6 O 8 ·4C 3 H 7 NO), and hemimellitic acid, H 3 HMA·2DMF·H 2 O (C 9 H 6 O 6 ·2C 3 H 7 NO·H 2 O), 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 (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 (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 non‐centrosymmetric and includes a mol­ecule of water per formula unit. Both DMF mol­ecules form an (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 (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.