A charge density analysis of cationic and anionic hydrogen bonds in a ''proton sponge'' complex
A charge density analysis of cationic and anionic hydrogen bonds in a ''proton sponge'' complex
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DOI：
10.1021/ja971940v
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发表时间：
1997-11-26
影响因子：
15
通讯作者：
McCormack, KL
中科院分区：
文献类型：
--
作者：
Mallinson, PR;Wozniak, K;McCormack, KL
用高分辨率x射线衍射和中子衍射在100 K下获得了由1,8-二（二甲氨基）萘（DMAN）形成的1,2-二氯马来酸氢盐晶体中的电荷密度分布。不对称的[Me2N-H…单质子化阳离子中的NMe2]（+）氢键具有非线性相互作用线的特征，受晶体对称性的约束位于DMAN分子的平面内；质子与受体氮原子之间的临界点位于电荷密度的正拉普拉斯区域。这个氮原子的孤对在氢键的方向上被极化。N-C（芳香）键路径有轻微的弯曲。在两个离子内的共价键和氢键的临界点上的电荷密度的大小与从从头算MO单点计算得到的正阴离子对的值进行了比较。弱C-H…中电荷密度的性质离子间相互作用被发现与供体-受体分离有系统的关系。一系列对甲酸离子-苯配合物模型的从头计算表明，C-H处的密度…氢键临界点系统地低于重叠部分的密度，但数量在当前实验测量的阈值上，用多极模型进行分析。
The charge density distribution in crystals of the 1,2-dichloro hydrogen maleate salt formed by 1,8-bis(dimethylamino)naphthalene (DMAN) has been obtained by high-resolution X-ray and neutron diffraction st 100 K. The asymmetric [Me2N-H ... NMe2](+) hydrogen bond in the monoprotonated cation is characterized by nonlinear interaction Lines, constrained by crystallographic symmetry to lie in the plane of the DMAN molecule; the critical point situated between the proton and the acceptor nitrogen atom lies in a region of positive Laplacian of the charge density. The lone pair of this nitrogen atom is polarized in the direction of the hydrogen bond. The N-C(aromatic) bond paths are slightly curved. Magnitudes of the charge density at critical points in covalent and hydrogen bonds within both ions are compared with values obtained from an ab initio MO single point calculation for a cation-anion pair. Properties of the charge density in a number of weak C-H ... O interionic interactions are found to be systematically related to the donor-acceptor separation. A series of ab initio calculations on a model formate ion-benzene complex shows that the density at C-H ... O hydrogen bond critical points is systematically lower than the density of the superposed moieties, but by an amount that is on the threshold of current experimental measurements analyzed with multipole-based models.