Dong Shuichao, Tao Yaqiu, Shen Xiaodong, Pan Zhigang
College of Materials Science and Engineering, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing, People's Republic of China.
Acta Crystallogr C. 2013 Aug;69(Pt 8):896-900. doi: 10.1107/S0108270113017423. Epub 2013 Jul 13.
A new polymorph of bis(2-aminopyridinium) fumarate-fumaric acid (1/1), 2C₅H₇N₂⁺∙C₄H₂O₄²⁻-·C₄H₄O₄, was obtained and its crystal structure determined by powder X-ray diffraction. The new polymorph (form II) crystallizes in the triclinic system (space group P-1), while the previous reported polymorph [form I; Ballabh, Trivedi, Dastidar & Suresh (2002). CrystEngComm, 4, 135-142; Büyükgüngör, Odabaşoğlu, Albayrak & Lönnecke (2004). Acta Cryst. C60, o470-o472] is monoclinic (space group P2₁/c). In both forms I and II, the asymmetric unit consists of one 2-aminopyridinium cation, half a fumaric acid molecule and half a fumarate dianion. The fumarate dianion is involved in hydrogen bonding with two neighbouring 2-aminopyridinium cations to form a hydrogen-bonded trimer in both forms. In form II, the hydrogen-bonded trimers are interlinked across centres of inversion via pairs of N-H∙∙∙O hydrogen bonds, whereas such trimers are joined via single N-H∙∙∙O hydrogen bonds in form I, leading to different packing modes for forms I and II. The results demonstrate the relevance and application of the powder diffraction method in the study of polymorphism of organic molecular materials.
获得了富马酸双（2 - 氨基吡啶鎓）-富马酸（1/1），即2C₅H₇N₂⁺∙C₄H₂O₄²⁻·C₄H₄O₄的一种新多晶型物，并通过粉末X射线衍射确定了其晶体结构。新的多晶型物（晶型II）结晶于三斜晶系（空间群P-1），而先前报道的多晶型物[晶型I；Ballabh, Trivedi, Dastidar & Suresh (2002). CrystEngComm, 4, 135 - 142；Büyükgüngör, Odabaşoğlu, Albayrak & Lönnecke (2004). Acta Cryst. C60, o470 - o472]为单斜晶系（空间群P2₁/c）。在晶型I和II中，不对称单元均由一个2 - 氨基吡啶鎓阳离子、半个富马酸分子和半个富马酸二阴离子组成。富马酸二阴离子在两种晶型中均通过氢键与两个相邻的2 - 氨基吡啶鎓阳离子相连，形成氢键三聚体。在晶型II中，氢键三聚体通过N - H∙∙∙O氢键对在反演中心处相互连接，而在晶型I中，此类三聚体通过单个N - H∙∙∙O氢键相连，导致晶型I和II具有不同的堆积模式。结果表明粉末衍射法在有机分子材料多晶型研究中的相关性和应用。
