Cocrystals of indole-3-acetic acid and indole-3-butyric acid: Synthesis, structural characterization and Hirshfeld surface analysis

A series of cocrystals and a salt of the indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) (plant hormone) with 2-aminopyrimidine (2AP), 2-amino-4,6-dimethylpyrimidine (2A-4,6-DMP) and 2,4,6-triaminopyrimidine (2,4,6-TAP) were successfully prepared, with an aim to explore the robustness of acid-aminopyrimidine synthon and its behaviour, with a change in the environment at 4,6 position of the pyrimidine ring. The formation of cocrystals/salt are examined on their Delta pKa values and were characterized by powder X-ray diffraction (PXRD), fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and their structures determined by single crystal X-ray diffraction (SCXRD). Additionally, Hirshfeld surface analysis was done to investigate the strength of the interactions and the overall percentage of short contacts and their impact on the overall packing. (C) 2018 Elsevier B.V. All rights reserved.