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首页> 外文期刊>Crystal growth & design >Molecular complexes of Homologous Alkanedicarboxylic Acids with Isonicotinamide: X-ray Crystal Structures, Hydrogen bond Synthons, and Melting Point Alternation
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Molecular complexes of Homologous Alkanedicarboxylic Acids with Isonicotinamide: X-ray Crystal Structures, Hydrogen bond Synthons, and Melting Point Alternation

机译：烷烃与异烟酰胺的分子配合物：X射线晶体结构，氢键合成子和熔点变化

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摘要

Crystallization of α,ω-alkanedicarboxylic acids (HOOC-(CH_2)_(n-2)-COOH, n = 2-6) with isonicotinamide (IN) is carried out in 1:2 and 1:1 stoichiometry. five cocrystals of (diacid)·(IN)_2 composition (diacid = oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid) are characterized by X-ray diffraction at 153(2) K. Tapes of acid-Pyridine O-H…N and amide-amide N-H…O hydrogen bond synthons stabilize these five crystal structures as predicted by the hierarchic model: the best donor (COOH) and best acceptor group (pyridine N) hydrogen bond as acid-pyridine and the second best donor-acceptor group (CONH_2) aggregates as an amide dimer. Glutaric acid and adipic acid cocrystallize in 1:1 stoichiometry also, (diacid)·(IN), with acid-pyridine and acid-amide hydrogen bonds. Synthon energy calculations (ΔE_(synthon), RHF/6-31G~(**)) explain the observed hydrogen bond preferences in 1:2 (five examples) and 1:1 (two examples) cocrystals. The acid-pyridine hydrogen bond is favored over the acid-amide dimer for strong carboxylic acids because the difference between ΔE_(acid-pyridine) and ΔE_(acid-amide) (-2.21 kcal mol~(-1)) is greater than the difference for weak acids (-0.77 kcal mol~(-1)), which cocrystallize with both of these hydrogen bond synthons. We suggest ΔE_(synthon) as a semiquantitative parameter to rank hydrogen bond preferences and better understand supramolecular organization in the multifunctional acid-IN system. Melting point alternation in five homologous (diacid)·(IN)_2 cocrystals is correlated with changes in crystal density and packing fraction.
机译：用异烟酰胺（IN）以1：2和1：1的化学计量进行α，ω-链烷二羧酸（HOOC-（CH_2）_（n-2）-COOH，n = 2-6）的结晶。通过在153（2）K处进行X射线衍射表征五个（二酸）·（IN）_2组成的共晶体（二酸=草酸，丙二酸，丁二酸，戊二酸和己二酸）。 OH…N和酰胺-酰胺NH…O氢键合成子稳定了这五个晶体结构，这是由层次模型预测的：最佳供体（COOH）和最佳受体基团（吡啶N）氢键作为酸吡啶和次佳供体-受体基团（CONH_2）聚集为酰胺二聚体。戊二酸和己二酸也以1：1的化学计量共结晶（二酸）·（IN），具有酸-吡啶和酸-酰胺氢键。 Synthon能量计算（ΔE_（synthon），RHF / 6-31G〜（**））解释了在1：2（五个示例）和1：1（两个示例）共晶中观察到的氢键偏好。对于强羧酸，酸-吡啶氢键优于酸-酰胺二聚体，因为ΔE_（酸-吡啶）和ΔE_（酸-酰胺）之间的差（-2.21 kcal mol〜（-1））大于与这两个氢键合成子共结晶的弱酸（-0.77 kcal mol〜（-1））的差异。我们建议使用ΔE_（synthon）作为半定量参数来对氢键的优先级进行排序，并更好地了解多功能酸-IN系统中的超分子组织。五个同源（二酸）·（IN）_2共晶体的熔点变化与晶体密度和堆积分数的变化相关。

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