Abstract The small organic molecule pyridine-2,6-dicarboxamide, although known in the literature for some time, exhibits interesting and previously unexplored intermolecular and intramolecular hydrogen bonding both in solid state and in solution. With the aid of X-ray crystallography and variable-temperature NMR spectroscopy, we here demonstrate the presence of a very strong hydrogen bonding network for this molecule both in condensed state and solution. Furthermore, a novel extended hydrogen bonding graph-set has been derived for this molecule in crystalline state. Comparison of pyridine-2,6-dicarboxamide with 1,3-benzenedicarboxamide, where the intramolecular hydrogen bonding to the pyridine ring in the former has been removed, yields a different intermolecular hydrogen bonded structure in the solid state. A new graph-set has been determined for the extended structure of 1,3-benzenedicarboxamide in the solid state. In solution, 1,3-benzenedicarboxamide is shown to maintain a hydrogen bonding pattern that is weaker than that observed with pyridine-2,6-dicarboxamide. Replacement of one hydrogen on each carboxamide nitrogen of pyridine-2,6-dicarboxamide by a methyl group also alters the extended structure to a significant extent. In N , N ′-dimethyl-2,6-pyridinedicarboxamide, the three-dimensional hydrogen bonding pattern observed with pyridine-2,6-dicarboxamide all but collapses to one-dimensional chains.

中文翻译：

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由分子内和分子间氢键控制的扩展结构：吡啶-2,6-二甲酰胺、1,3-苯二甲酰胺和 N , N '-二甲基-2,6-吡啶二甲酰胺的案例研究

摘要 有机小分子吡啶-2,6-二甲酰胺虽然在文献中已有一段时间已知，但在固态和溶液中都表现出有趣且以前未探索过的分子间和分子内氢键。借助 X 射线晶体学和变温 NMR 光谱，我们在这里证明了该分子在凝聚态和溶液中都存在非常强的氢键网络。此外，已经为这种处于结晶状态的分子推导出了一种新的扩展氢键图集。吡啶-2,6-二甲酰胺与1,3-苯二甲酰胺的比较，前者中与吡啶环的分子内氢键已被去除，在固态下产生不同的分子间氢键结构。已为固态 1,3-苯二甲酰胺的扩展结构确定了新的图集。在溶液中，1,3-苯二甲酰胺显示出保持比用吡啶-2,6-二甲酰胺观察到的更弱的氢键模式。用甲基取代吡啶-2,6-二甲酰胺的每个甲酰胺氮上的一个氢也会在很大程度上改变扩展结构。在 N , N '-二甲基-2,6-吡啶二甲酰胺中，用吡啶-2,6-二甲酰胺观察到的三维氢键模式几乎都坍塌为一维链。用甲基取代吡啶-2,6-二甲酰胺的每个甲酰胺氮上的一个氢也会在很大程度上改变扩展结构。在 N , N '-二甲基-2,6-吡啶二甲酰胺中，用吡啶-2,6-二甲酰胺观察到的三维氢键模式几乎都坍塌为一维链。用甲基取代吡啶-2,6-二甲酰胺的每个甲酰胺氮上的一个氢也会在很大程度上改变扩展结构。在 N , N '-二甲基-2,6-吡啶二甲酰胺中，用吡啶-2,6-二甲酰胺观察到的三维氢键模式几乎都坍塌为一维链。