Synthesis, Characterization and Biological Activity of (Phenylthio)Acetic Acid:Theophylline Cocrystal

A reaction between theophylline and (phenylthio)acetic acid in methanol results in the formation of organic cocrystal (phenylthio)acetic acid:theophylline. The characterization of the resulting cocrystal is performed using IR and 1 H NMR spectroscopy, TGA/DTA and X-ray crystallography. The crystal system of the cocrystal is monoclinic with space group P21/c and (Z = 8; Zʹ = 2). The unit cell parameters are a = 15.248(4) Å, b = 13.156(4) Å, c = 16.002(5) Å, and β = 106.059(4)°. The imidazole-carboxylic acid synthon is observed in the cocrystal. Intermolecular O–H…N hydrogen bonds and π–π interactions together play a vital role in the formation of the cocrystal and in the stabilization of the structure. Computational optimizations of the molecule were performed by density functional theory (DFT) using the B3LYP functional and Hartree–Fock (HF) level with a 6–311+ +G(d,p) basis set. In-vitro anti-microbial activities against some bacterial and fungal strains were investigated. Graphic Abstract The bandgap of the cocrystal is 3.5 times smaller than the starting compound.