Three new cocrystals derived from liquid pyrazine spices: X-ray structures and Hirshfeld surface analyses.

Cocrystal modification strategy has been applied to 3,5-dichlorosalicylic acid (DCA) through the addition of various liquid pyrazine derivatives: 2,3-dimethylpyrazine (2,3-DMP); 2,5-dimethylpyrazine (2,5-DMP); and 2,3,5-trimethylpyrazine (TMP). Three new cocrystals (2,3-DMP-DCA = 1:2 for 1; 2,5-DMP-DCA = 1:2 for 2; and TMP-DCA = 1:1 for 3) have been obtained, all of which were characterized by X-ray diffraction analysis, infrared spectroscopy, thermogravimetric analyses and UV–Vis spectroscopy. The Hirshfeld surface analysis has been performed to illustrate the intermolecular interactions. The results revealed that hydrogen bonding and other weaker interactions such as halogen bonding contacts and π···π stacking participated in a cooperative way to stabilize the supramolecular structures and different methyl substitutions changed the bonding mode and intermolecular force of pyrazine derivative cocrystals. Thermodynamic results showed that the stability of liquid pyrazine spices can be improved and the decomposition temperature for cocrystal 3 is higher than the other cocrystals. This work provides an approach to solidification of liquid pyrazine spices for more applications. [ABSTRACT FROM AUTHOR]