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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Experimental and Theoretical Charge Density Study of Polymorphic Isonicotinamide-Oxalic Acid Molecular Complexes with Strong O· · ·H· · ·N Hydrogen Bonds
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Experimental and Theoretical Charge Density Study of Polymorphic Isonicotinamide-Oxalic Acid Molecular Complexes with Strong O· · ·H· · ·N Hydrogen Bonds

机译：具有强O···H···N氢键的多晶型异烟酰胺-草酸分子配合物的实验和理论电荷密度研究

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摘要

Two polymorphs of the 2:1 molecular complex of isonicotinamide and oxalic acid have been characterized by combined X-ray charge density and single-crystal neutron diffraction studies at 100 K. Both polymorphs show strong O-H· · ·N intermolecular hydrogen bonding between the acid and the pyridine base. As is typical of short, strong hydrogen bonds (SSHBs), the covalent O-H bonds are considerably elongated to 1.161(3) and 1.235(5) A, and the H· · ·N interactions are correspondingly short at 1.398(3) and 1.313(6) A in Forms I and II, respectively. The neutron diffraction data indicate no pronounced H dynamics in the SSHBs, and in the case of Form II the SSHB can be described as quasicentered. In addition to the experimental charge densities, theoretical charge densities have been determined from ab initio calculations within the full periodic environment of the crystalline state. The SSHBs are found to be covalent in nature according to the topological analysis of the experimental and theoretical charge densities and application of the source function. Aside from the SSHBs, moderate N-H· · ·O and weak C-H· · ·O interactions are also present in the molecular complexes, for which hydrogen bond energies are estimated from energy densities and independent ab initio calculations. Finally, an attempt is made to evaluate the intermolecular interactions governing the manifestation of polymorphism in this compound.
机译：结合X射线电荷密度和100 K单晶中子衍射研究了异烟酰胺和草酸2：1分子复合物的两个多晶型物。两个多晶型物显示酸之间的强OH···N分子间氢键和吡啶碱。正如典型的短而强的氢键（SSHBs）一样，共价OH键显着延长至1.161（3）和1.235（5）A，H···N相互作用也相应地短于1.398（3）和1.313。 （6）分别为表格I和II的A。中子衍射数据表明在SSHB中没有明显的H动力学，在晶型II的情况下，SSHB可描述为准中心。除了实验电荷密度外，还从晶态的整个周期性环境中的从头算中确定了理论电荷密度。根据实验和理论电荷密度的拓扑分析以及源函数的应用，发现SSHB在本质上是共价的。除了SSHB外，分子复合物中还存在适度的N-H··O和弱的C-H···O相互作用，可根据能量密度和独立的从头算来估算氢键能。最后，尝试评估控制该化合物中多态性表现的分子间相互作用。

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