3-溴咔唑-9-乙酸晶体中的分叉型氢键及其理论分析

Bifurcated hydrogen-bond in 3-Br-carbazole-9-yl-acetic acid crystal and its theoretical analysis

用半经验量子化学AM1方法分析了化合物3-溴咔唑-9-乙酸的分子构象.结果表明,化合物3-溴咔唑-9-乙酸晶体存在分子间非对称分叉型氢键;该非对称分叉型氢键支配化合物的堆积结构.与此同时,同咔唑环氮原子相连的羧甲基易在一定范围内摆动,分叉型氢键是晶体状态下和真空中羧甲基位置变化的原因之一;非对称分叉型氢键使分子体系得到4.97kJ/mol的额外稳定作用能.

Semiempirical quantum chemistry AM1 method was adopted to analyze the molecular conformation of 3-Br-carbazole-9-yl-acetic acid. Results indicate that there exist asymmetrical bifurcated hydrogen bonds in 3-Br-carbazole-9-yl-acetic acid crystal, and the stacking structure of the crystal is dominated by the asymmetrical bifurcated hydrogen bonds. In the meantime, the caboxymethyl group connected with the carbazole nitrogen atom readily flaps within a certain range, and the varying locations of the caboxymethyl groups in the solid state and structure in vacuo of the compound can be partly attributed to the bifurcated hydrogen-bond. Besides, the asymmetric bifurcated hydrogen bond adds 4.97 kJ/mol of additional stabilization energy to the molecular system.