Crystal Structures of S‑Shaped Phenylenediurea Dibenzoic Acids and Their Cocrystals with Melamine: Unusual Zigzag Tape of H‑Bonded Melamine Network

Phenylenediurea
dibenzoic acid derivatives 1, 2, 3, and 5 and an amide derivative 4 were
synthesized, and their molecular structures were elucidated
to be an S-shape by single crystal X-ray analysis. Crystals of 1 were obtained as a DMF solvate, while those of 2 and 3 were not. Sheet and ladder structures were created
in the crystal packing of 1 and 3, and 2, respectively. Unlike the para-substituted diureas 1–3 which possessed meso-conformation,
the meta-substituted diurea 5 exhibited helical-conformation
in its crystal structure. The way of crystal packing of 4 is analogous to that of the corresponding dicarboxylic acid derivative 2. A water cluster of a chair-shaped hexagonal array of water
molecules was created in the crystal structure of 4.
Diureas 1 and 2 gave cocrystals with melamine
recrystallized from DMF/ethyl acetate and DMF/H2O, respectively.
Unusual zigzag tapes of a H-bonding network of melamine were created
in both cocrystals. The zigzag tapes were connected with S-shaped
diureas by H-bonding to furnish an interpenetrated fishnet-type crystal
structure.