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首页> 外文期刊>Chemistry: A European journal >Electron distribution and molecular motion in crystalline benzene: an accurate experimental study combining CCD X-ray data on C_6H_6 with multitemperature neutron-diffraction results on C_6D_6
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Electron distribution and molecular motion in crystalline benzene: an accurate experimental study combining CCD X-ray data on C_6H_6 with multitemperature neutron-diffraction results on C_6D_6

机译：结晶苯中的电子分布和分子运动：结合C_6H_6的CCD X射线数据和C_6D_6的多温度中子衍射结果的精确实验研究

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摘要

The electronic properties of the benzene molecule, for example its quadrupole moment and the electric field gradients (EFG's) at the H nuclei, are of fundamental importance in theoretical and experimental chemistry. With this in mind, single-crystal X-ray diffraction data on C_6H_6 were collected with a charge-coupled device detector at T approx= 110 K. As accurate modelling of the thermal motion in the crystal was regarded as vital, especially for the hydrogen atoms, anisotropic-displacement parameters (ADP's) for the C and H atoms in C_6H_6 were derived in a stralight-forward fashion from analysis of the temperature dependence of ADP's for the C and D atoms in C_6D_6 at 15 K and 123 K obtained by neutron diffraction. Agreement between C-atom ADP's derived from thermal-motion analysis of neutro data and those obtained from multipole refinement by using the X-ray data is extraordinarily good; this gives confidence in the modelling of vibrational motion for the H atoms. The molecular quadrupole moment derived from the total charge density of the molecule in the crystal is (-29.7 +- 2.4) X 10~(-40) Cm~2, in excellent agreement with measurements made in the gas phase and in solution. The average deuterium nuclear quadrupole coupling constant (DQCC) derived from EFG tensors at H atoms is 182 +- 17 kHz, also in excellent agreement with independent measurements. The strategy employed in this work may be of more general applicability for future accurate electron density studies.
机译：苯分子的电子性质，例如其四极矩和H原子核处的电场梯度（EFG's）在理论和实验化学中都至关重要。考虑到这一点，使用电荷耦合器件检测器在T大约= 110 K时收集了C_6H_6的单晶X射线衍射数据。准确地模拟晶体中的热运动被认为是至关重要的，特别是对于氢通过分析中子在15 K和123 K下分析C_6D_6中C和D原子在15 K和123 K时ADP对C和D原子的温度依赖性，以顺势方式得出C_6H_6中C和H原子的各向异性位移参数（ADP）。衍射。通过对中子数据进行热运动分析得出的C原子ADP与通过使用X射线数据进行多极精细化获得的原子之间的一致性非常好;这为H原子的振动运动建模提供了信心。由晶体中分子的总电荷密度得出的分子四极矩为（-29.7 +-2.4）X 10〜（-40）Cm〜2，与在气相和溶液中进行的测量非常吻合。在H原子上由EFG张量导出的平均氘核四极耦合常数（DQCC）为182±17 kHz，与独立测量也非常吻合。在这项工作中采用的策略可能更广泛地适用于未来的精确电子密度研究。

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