Reassessment of large dipole moment enhancements in crystals: a detailed experimental and theoretical charge density analysis of 2-methyl-4-nitroaniline.
Reassessment of large dipole moment enhancements in crystals: a detailed experimental and theoretical charge density analysis of 2-methyl-4-nitroaniline.
复制标题
晶体中大偶极矩增强的重新评估：2-甲基-4-硝基苯胺的详细实验和理论电荷密度分析。
DOI：
10.1021/jp061830n
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
M. Spackman
中科院分区：
文献类型：
--
作者：
A. Whitten;P. Turner;W. Klooster;R. Piltz;M. Spackman
MNA在晶体中的分子偶极矩已被严格重新检查，以测试从早期的实验电荷密度分析的结论，它是大大增强由于强分子间相互作用和晶体场效应的组合。X射线和中子衍射数据已仔细测量在100 K，并补充从头计算晶体Hartree-Fock计算。在测量和减少实验数据中采取了相当多的照顾排除了大多数系统误差，误差的来源和它们对实验电子密度的影响进行了仔细的研究。电子密度来自一个适合的理论结构因素，协助确定的规模和热运动模型。晶体中MNA的偶极矩增强比以前报道的要小得多，仅为30-40%（约2.5 D）。除了偶极矩，实验变形电子密度图，键临界点数据，电场梯度在氢核，原子和基团电荷都同意与理论结果和趋势。氢原子运动的各向异性建模，周期性从头计算的积分使用，以及提高数据质量是本研究的所有方面，代表了比以前的工作有相当大的进步。
The molecular dipole moment of MNA in the crystal has been critically reexamined, to test the conclusion from an earlier experimental charge density analysis that it was substantially enhanced due to a combination of strong intermolecular interactions and crystal field effects. X-ray and neutron diffraction data have been carefully measured at 100 K and supplemented with ab initio crystal Hartree-Fock calculations. Considerable care taken in the measurement and reduction of the experimental data excluded most systematic errors, and sources of error and their effects on the experimental electron density have been carefully investigated. The electron density derived from a fit to theoretical structure factors assisted in the determination of the scale and thermal motion model. The dipole moment enhancement for MNA in the crystal is much less than that reported previously and only on the order of 30-40% (approximately 2.5 D). In addition to the dipole moment, experimental deformation electron density maps, bond critical point data, electric field gradients at hydrogen nuclei, and atomic and group charges all agree well with theoretical results and trends. Anisotropic modeling of the motion of hydrogen atoms, integral use of periodic ab initio calculations, and improved data quality are all aspects of this study that represent a considerable advance over previous work.