Jelsch Christian, Bibila Mayaya Bisseyou Yvon
CRM2, UMR CNRS 7036, Université de Lorraine, Nancy 54500, France.
Laboratoire des Sciences de la Matière, de l'Environnement et de l'Energie Solaire, UFR SSMT, Université Félix Houphouët-Boigny, 22 BP 582 Abidjan 22, Cote d'Ivoire.
IUCrJ. 2023 Sep 1;10(Pt 5):557-567. doi: 10.1107/S2052252523005675.
Hirshfeld surface analysis is a widely used tool for identifying the types of intermolecular contacts that contribute most significantly to crystal packing stabilization. One useful metric for analyzing these contacts is the contact enrichment descriptor, which indicates the types of contacts that are over- or under-represented. In this statistical study, enrichment ratios were combined with electrostatic energy (E) data for a variety of compound families. To compute the electrostatic interaction energy between atoms, charge density models from the ELMAM2 database of multipolar atoms were used. As expected, strong hydrogen bonds such as O/N-H...N and O/N-H...O typically display large enrichment values and have the most negative (i.e. favorable) electrostatic energies. Conversely, contacts that are repulsive from an electrostatic perspective are usually the most under-represented. Analyzing the enrichment ratio and electrostatic energy indicators was shown to help identify which favorable contacts are the most competitive with each other. For weaker interactions, such as hydrophobic contacts, the behavior is less clear cut and can depend on other factors such as the chemical content of the molecule. The anticorrelation between contact enrichment and E is generally lost for weaker contacts. However, we observed that C...C contacts are often enriched in crystal structures containing heterocycles, despite the low electrostatic attraction. For molecules with only weak hydrogen bond donors/acceptors and hydrophobic groups, the correlation between contact enrichment and E is still evident for the strongest of these interactions. However, there are some exceptions where the most favorable contacts from an electrostatic perspective are not the most over-represented. This can occur in cases where the shape of the molecule is complex or elongated, favoring dispersion forces and shape complementarity in the packing.
Hirshfeld表面分析是一种广泛使用的工具,用于识别对晶体堆积稳定性贡献最为显著的分子间接触类型。分析这些接触的一个有用指标是接触富集描述符,它表明了接触类型的富集或贫化情况。在这项统计研究中,将富集比率与多种化合物家族的静电能(E)数据相结合。为了计算原子间的静电相互作用能,使用了来自多极原子ELMAM2数据库的电荷密度模型。正如预期的那样,诸如O/N-H...N和O/N-H...O等强氢键通常显示出较大的富集值,并且具有最负的(即有利的)静电能。相反,从静电角度来看具有排斥性的接触通常是最不富集的。结果表明,分析富集比率和静电能指标有助于确定哪些有利接触相互之间最具竞争力。对于较弱的相互作用,如疏水接触,其行为不太明确,可能取决于其他因素,如分子的化学组成。对于较弱的接触,接触富集与E之间的反相关性通常会消失。然而,我们观察到,尽管静电吸引力较低,但在含有杂环的晶体结构中,C...C接触往往会富集。对于仅具有弱氢键供体/受体和疏水基团的分子,在这些相互作用中最强的那些相互作用中,接触富集与E之间的相关性仍然很明显。然而,也有一些例外情况,即从静电角度来看最有利的接触并非最富集的。这种情况可能发生在分子形状复杂或细长的情况下,有利于堆积中的色散力和形状互补性。