Scholarlink

<p>The barrier to rotation of the unsubstituted cyclopentadienyl (Cp) ring in the crystal of <i>rac-N</i>,<i> N</i>-dimethyl-1-ferrocenylethylamine (Ugi’s amine) hydrobenzoate was investigated using a combination of density functional theory (DFT) calculations and variable-temperature single-crystal X-ray diffraction (SC XRD). The gas-phase rotational barrier was determined to be 4.2&#xa0;kJ/mol, which is comparable to that of unsubstituted ferrocene, indicating a negligible effect of the <i>N</i>,<i> N</i>-dimethyl-1-ferrocenylethylammonium substituent on the intramolecular barrier. In contrast, the experimental barrier in the crystalline state, derived from TLS analysis of anisotropic displacement parameters over a temperature range of 150–300&#xa0;K, was significantly higher, ranging from 8.8 to 10.8&#xa0;kJ/mol. This increase provides direct evidence for the dominant role of intermolecular interactions, specifically C–H···O and C–H···π contacts, in restricting Cp-ring rotation in the solid state. The obtained barrier values are consistent with those classified as Case <b>I</b> (molecules in general positions), and this study underscores the efficacy of variable-temperature SC XRD coupled with TLS analysis for quantifying molecular dynamics, such as ligand rotation, in molecular crystals.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Barrier to rotation of the unsubstituted Cp-ring in the crystal of rac-N,N-dimethyl-1-ferrocenylethylamine hydrobenzoate

  • 期刊论文

  • 发表日期：

    2025年11月10日

查看全文
  • Daut R. Islamov,
  • Daria P. Gerasimova,
  • Vladimir E. Volkov,
  • Almaz A. Zagidullin,
  • Konstantin S. Usachev

摘要

The barrier to rotation of the unsubstituted cyclopentadienyl (Cp) ring in the crystal of rac-N, N-dimethyl-1-ferrocenylethylamine (Ugi’s amine) hydrobenzoate was investigated using a combination of density functional theory (DFT) calculations and variable-temperature single-crystal X-ray diffraction (SC XRD). The gas-phase rotational barrier was determined to be 4.2 kJ/mol, which is comparable to that of unsubstituted ferrocene, indicating a negligible effect of the N, N-dimethyl-1-ferrocenylethylammonium substituent on the intramolecular barrier. In contrast, the experimental barrier in the crystalline state, derived from TLS analysis of anisotropic displacement parameters over a temperature range of 150–300 K, was significantly higher, ranging from 8.8 to 10.8 kJ/mol. This increase provides direct evidence for the dominant role of intermolecular interactions, specifically C–H···O and C–H···π contacts, in restricting Cp-ring rotation in the solid state. The obtained barrier values are consistent with those classified as Case I (molecules in general positions), and this study underscores the efficacy of variable-temperature SC XRD coupled with TLS analysis for quantifying molecular dynamics, such as ligand rotation, in molecular crystals.