Effect of the Methanol Molecule on the Stabilization of C18H18O4 Crystal: Combined Theoretical and Structural Investigation

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• 作者：L贸ide O. Sallum ; Hamilton B. Napolitano ; Paulo de Sousa Carvalho ; Jr. ; Amanda Feitosa Cidade ; Gilberto Lucio Benedito de Aquino ; Nayara D. Coutinho ; Ademir J. Camargo ; Javier Ellena ; Heibbe C. B. de Oliveira ; Valter H. C. Silva
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：October 30, 2014
• 年：2014
• 卷：118
• 期：43
• 页码：10048-10056
• 全文大小：504K
• ISSN：1520-5215

文摘

The ability of the chalcone, C₁₈H₁₈O₄, to form solvates was theoretically and experimentally investigated. The unit cell with Z鈥?> 1, composed of two independent chalcone molecules (伪 and 尾), shows the formation of a stable molecular complex which is related with the presence of methanol in this crystal lattice. Aiming to understand the process of crystal lattice stabilization, a combination of techniques was used, including X-ray diffraction (XRD), computational molecular modeling, and an ab initio molecular dynamic. The results show that 伪 and 尾 molecules are sterically barred from forming a direct hydrogen bond with one other. In addition, the presence of the methanol molecule stabilizes the crystal structure by a bifurcated O鈥擧路路路O interaction acting as a bridge between them. The theoretical thermodynamic parameter and the rigid potential energy surface scan describe the role of methanol in the energy stabilization of the crystal. The absence of the methanol compound in the asymmetric unit destabilizes the crystalline structure, making the formation process of the asymmetric unit nonspontaneous. The energy difference between 伪 and 尾 molecules is around 0.80 kcal路mol^鈥?, indicating that both are stable and equally possible in the crystal lattice. The analysis of the energy profile of the C14鈥揙2路路路H1鈥揙3 and O2鈥揌1路路路O3鈥揅17 torsion angles in the crystal packing shows that the 伪 and 尾 molecules are confined in the stable potential region, in agreement with the two conformers in the asymmetric unit. The Molecular Electrostatic Potential (MEP) shows that the methanol has no steric effects, which prevents small motion around the torsion angles.