A cocrystal strategy for the precipitation of liquid 2,3-dimethyl pyrazine with hydroxyl substituted benzoic acid and a Hirshfeld surfaces analysis of them
writer：Yang-Hui Luo, Chen-Guang Zhang, Bing Xu, Bai-Wang Sun*
keywords：cocrystal strategy, Hirshfeld surfaces
source：期刊
specific source：CrystEngComm
Issue time：2012年
We here report the cocrystal strategy for the precipitation of liquid 2,3-dimethyl pyrazine (2,3-DMP) with the hydroxyl substituted benzoic acids: salicylic acid (SA), m-hydroxybenzoic acid (MHBA) and p-hydroxybenzoic acid (PHBA) under identical conditions, and obtained three cocrystals (cocrystal 1–3), respectively. Their crystal structures were characterized by single-crystal X-ray diffraction, IR spectra, differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), hot stage microscopy (HSM) and X-ray powder diffraction (XRPD). Wherein, 1 forms a 1 : 2 2,3-DMP : SA cocrystal; 2 forms a 1 : 1 2,3-DMP : MPHA cocrystal and 3 forms a 1 : 1 : 1 2,3-DMP : PHBA : H2O cocrystal. The structure determination shows that the three cocrystals are all primarily stabilized by a strong O–H…N hydrogen bonding interaction between 2,3-DMP and the hydroxyl substituted benzoic acid. We also prepared and analysed Hirshfeld surfaces and fingerprint plots of the reported cocrystals and reveal that the structures are stabilized by H…H, O–H…N, O–H…N, C–H…p, p…p and lone-pair…p intermolecular interactions. Additionally, what is interesting is that cocrystal 2 sublimes half the 2,3-DMP at about 110 uC during the heating procedure, while the other half sublimes at about 226 uC, which was confirmed by the XRPD measurement. This may be developed for the controlled release of 2,3-DMP.