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<p>The analysis of single crystal diffraction data for acetonitrile CH<sub>3</sub>CN and acetone (CH<sub>3</sub>)<sub>2</sub>CO molecules, both as pure substances and solvates, retrieved from Cambridge Crystal Structure Database, confirmed the existence of previously identified area of uncertainty in geometric parameters given by single crystal X-ray diffraction. In our study, bond lengths and bond angles of two small molecules in crystals were compared to gas-phase data for the individual molecules and high-level quantum chemical calculations of both individual molecules and their small clusters. The data analysis showed that experimental points of good crystal structures tightly fill the area of 0.02–0.03 Å in bond lengths and 1-2<sup>o</sup> in bond angles respectively. The average X-ray bond lengths are systematically shortened by ca. 0.02 Å as compared to gas phase and quantum chemical data and diminished with an increase in the temperature of X-ray study. Possible reasons for the observed trends including intramolecular dynamics and intermolecular interactions, are discussed basing on quantum chemistry calculations.</p>

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On the actual accuracy of structural parameters in single crystal diffraction studies and possible origins of their systematic errors

  • 期刊论文

  • 发表日期：

    2026年5月30日

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  • Yuri L. Slovokhotov,
  • Igor F. Shishkov,
  • Ekaterina P. Altova,
  • Yulia V. Novakovskaya

摘要

The analysis of single crystal diffraction data for acetonitrile CH3CN and acetone (CH3)2CO molecules, both as pure substances and solvates, retrieved from Cambridge Crystal Structure Database, confirmed the existence of previously identified area of uncertainty in geometric parameters given by single crystal X-ray diffraction. In our study, bond lengths and bond angles of two small molecules in crystals were compared to gas-phase data for the individual molecules and high-level quantum chemical calculations of both individual molecules and their small clusters. The data analysis showed that experimental points of good crystal structures tightly fill the area of 0.02–0.03 Å in bond lengths and 1-2o in bond angles respectively. The average X-ray bond lengths are systematically shortened by ca. 0.02 Å as compared to gas phase and quantum chemical data and diminished with an increase in the temperature of X-ray study. Possible reasons for the observed trends including intramolecular dynamics and intermolecular interactions, are discussed basing on quantum chemistry calculations.