Conformation-Directed Hydrogen-Bonding in meta-Substituted Aromatic Ureadicarboxylic Acid: A Conformationally Flexible U-Shaped Building Block.

Crystalstructures of U-shaped aromatic ureadicarboxylic acid possessing twocarboxy moieties at meta-positions of phenyl ringswere investigated. It afforded cocrystals with dipyridyl derivatives.In addition to the U-shaped conformation obtained by recrystallizationfrom methanol, another three types of U-shaped conformations werefound in the crystal structure of the cocrystals. The direction ofH-bonding was fixed based on the relative geometry of two carboxymoieties in the resulting conformations. Depending on these conformations,triple helices with one-dimensional water channels, infinite cross-belt,and step-like structures were generated via H-bonding between thecarboxy and the pyridyl moieties. Methanol solvate was obtained forthe cocrystal with 1,4-di(pyridine-4-yl)benzene which showed differentU-shaped conformation of urea dicarboxylic acid from that involvedin the cocrystal free of methanol. [ABSTRACT FROM AUTHOR]