Caffeine and theophylline are methyl-xantine drugs, which are affected by water leading to their hydrated forms. The purpose of this work was to prepare and characterize hydrated forms of caffeine and theophylline by mechanochemistry. The obtained products were characterized by infrared spectroscopy and Xray powder diffraction. The infrared spectra and diffractograms of the ground products were similar to the reported for caffeine and theophylline hydrates.

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The cocrystal formed by diethyl N,Ń -[1,3-(2-methyl)phenyl]dioxalamate (1) and resorcinol (2), namely 1Á2 cryst (C 21 H 24 N 2 O 8 ) was prepared by mechanochemical complexation. IR spectroscopy and powder X-ray diffraction studies allowed to determine the complexation and the conformational switching of the ethyl oxalamate side arms. In the crystal structure of 1Á2 cryst , complexation occurs through O-HÁÁÁO=C hydrogen-bonding interactions with the participation of phenolic O-H as donor and amide carbonyl group as acceptor. The steric hindrance of the CH 3 group in the C-2 position of the aromatic ring leads to a meso-helical supramolecular architecture forming a C 2 2 (16) chain motif. Crystal data: monoclinic, C2/c space group, a = 34.9054(13) Å , b = 8.0434(5) Å , c = 5.1577(8) Å , b = 97.521(3)°. Graphical Abstract The cocrystal formed by diethyl N,Ń -[1,3-(2-methyl)phenyl]dioxalamate and resorcinol, prepared by mechanochemical complexation.