基于氢键合成子的竞争与预测

【作者】 张致慧；

【导师】 杜淼；

【作者基本信息】 天津师范大学 ， 有机化学， 2005， 硕士

【副题名】羧酸—联吡啶有机二元共晶超分子体系的构筑

【摘要】 利用2,5-双（3-吡啶基）-1,3,4-噁二唑（3-bpo）及其四位异构体2,5-双（4-吡啶基）-1,3,4-噁二唑（4-bpo）与各种羧酸（包括刚性芳香酸及柔性脂肪酸）反应制备了一系列二元有机共晶化合物。与经典的线性联吡啶建筑块相比,具有弯曲骨架的此类化合物含有多个氢键联结点,可以同有机酸形成更加稳定且多样的超分子合成子,从而用于高产率制备二元超分子共晶。 合成了六个基于bpo和芳香二酸的超分子化合物,包括[phthalic acid]·[3-bpo]（1）,[phthalic acid]·[4-bpo]（2）,[isophthalic acid]·[3-bpo]（3）,[isophthalic acid]·[4-bpo]（4）,[terephthalic acid]·[3-bpo]（5） 和[terephthalic acid]·[4-bpo]（6）,并利用x-射线单晶衍射技术确定了它们的晶体结构。合成子I[R₂²（7）]由经典的强O-H…N和弱C-H…O氢键构成,该合成子通常出现在有机酸与杂环碱所形成的共晶中,对构筑新型超分子氢键网络起到了关键性的作用。化合物1-6的熔点主要同酸本身的性质及晶体堆积方式有关,热重（TGA）结果表明其热稳定性与晶体中氢键的强度以及强氢键的数目密切相关。 Bpo与trimesic酸（H₃TMA）和pyromellitic酸（H₄BTA）在室温下反应得到超分子化合物[（H₃TMA）·（3-bpo）]·DMF（7）,[（H₃TMA）·（4-bpo）]（8）和[（H₄BTA）·（3-bpo）]·2H₂O（9）,及电荷转移盐[（H₂BTA）_1/2·（H-4-bpo）·（H₄BTA）_1/2]·H₂O（10）。4-Bpo和H₄BTA在水热条件下反应意外得到化合物Pyromellitic dihydrazide（11）。X射线晶体结构表明7-10的二元氢键网络均含有超分子合成子I[R₂²（7）]。此外通过TGA技术研究了此系列化合物的热稳定性。 合成和表征了bpo与柔性酸所形成的六个共晶[fumaric acid]·[3-bpo]（12）,[fumaricacid]·[4-bpo]（13）,[suberic acid]·[3-bpo]（14）,[suberic acid]·[4-bph]（15）,[benzene-1,4-dioxyacetate acid]·[3-bpo]（16）以及[benzene-1,4-dioxyacetate acid]·[4-bpo]（17）。晶体结构分析表明,化合物13-17中酸-碱基元之间均通过羧酸-吡啶合成子连接而形成带状或之字型一维氢键结构。并进一步探讨了此类柔性羧酸和刚性芳香酸与bpo所形成共晶的各种超分子结构的异同,丰富了相关晶体工程研究。更多还原

【Abstract】 2,5-Bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo) and its 4-N-donor analogue 2,5-bis(4-pyridyl) -1,3,4-oxadiazole (4-bpo), are introduced to synthesize a series of binary cocrystals with different carboxylic acids from rigid aromatic to flexible aliphatic species. In contrary to classical linear dipyridyl building blocks, the bent bpo bases can form robust hydrogen-bonding syn-thons with these organic acids and produce well-defined cocrystallizing supramolecular compounds in considerable high yields.The preparation and X-ray structures of six 1:1 molecular cocrystals including [phthalic acid]- [3-bpo] (1), [phthalic acid]-[4-bpo] (2), [isophthalic acid]-[3-bpo] (3), [isophthalic acid]-[4-bpo] (4), [terephthalic acid]-[3-bpo] (5) and [terephthalic acid]-[4-bpo] (6), are described. A supramolecular synthon I [R22(7)] containing classical O-H…N and weak C-H…O interactions, usually observed in organic cocrystals of carboxylic acids with other heterocyclic bases, is again shown to be involved in constructing most of these hydrogen-bonding networks. Melting points of cocrystals 1-6 are mainly correlated with the nature of acid component and crystal packing. Thermogravimetric analysis (TGA) of mass loss for six compounds has been shown to correlate with the strength of hydrogen bonds in the packing fraction.Bpos were applied to crystallize with trimesic and pyromellitic acid (H3TMA and H4BTA), affording three new cocrystals [(H3TMA)(3-bpo)]-DMF (7), [(H3TMA)-(4-bpo)] (8), [(H4BTA)-(3-bpo)]-2H2O (9) and apartly charge-transfer salt [(H2BTA)./3-(H-4-bpo)-(H4BTA)1/2] H2O (10) under general conditions. Pyromellitic dihydrazide (11) was obtained during the attempt of attaining a cocrystal of 4-bpo and H4BTA by hydrothermal synthesis. X-ray single-crystal diffraction studies reveal that supramolecular synthon I [R22 (7)] is again testified to be involved in constructing the binary hydrogen-bonding networks of 7-10, in which the het-eromeric intermolecular interactions are often utilized as effective synthetic tools to provide a significant portion of the stabilization energy of molecular crystals. Thermal stability of cocrystals 7-10 has been investigated by TGA of mass loss.The preparation and X-ray structures of six 1:1 stoichiometric cocrystals were discussed in更多还原