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Evaluating the Energetic Driving Force for Cocrystal Formation.
Crystal Growth & Design ( IF 3.2 ) Pub Date : 2017-12-13 , DOI: 10.1021/acs.cgd.7b01375
Christopher R Taylor 1 , Graeme M Day 1
Affiliation  

We present a periodic density functional theory study of the stability of 350 organic cocrystals relative to their pure single-component structures, the largest study of cocrystals yet performed with high-level computational methods. Our calculations demonstrate that cocrystals are on average 8 kJ mol-1 more stable than their constituent single-component structures and are very rarely (<5% of cases) less stable; cocrystallization is almost always a thermodynamically favorable process. We consider the variation in stability between different categories of systems-hydrogen-bonded, halogen-bonded, and weakly bound cocrystals-finding that, contrary to chemical intuition, the presence of hydrogen or halogen bond interactions is not necessarily a good predictor of stability. Finally, we investigate the correlation of the relative stability with simple chemical descriptors: changes in packing efficiency and hydrogen bond strength. We find some broad qualitative agreement with chemical intuition-more densely packed cocrystals with stronger hydrogen bonding tend to be more stable-but the relationship is weak, suggesting that such simple descriptors do not capture the complex balance of interactions driving cocrystallization. Our conclusions suggest that while cocrystallization is often a thermodynamically favorable process, it remains difficult to formulate general rules to guide synthesis, highlighting the continued importance of high-level computation in predicting and rationalizing such systems.

中文翻译:

评估共晶形成的能量驱动力。

我们对 350 种有机共晶相对于其纯单组分结构的稳定性进行了周期性密度泛函理论研究,这是迄今为止使用高级计算方法对共晶进行的最大研究。我们的计算表明,共晶平均比其组成的单组分结构稳定 8 kJ mol-1,并且很少(<5% 的情况)不太稳定;共结晶几乎总是一个热力学有利的过程。我们考虑了不同类别系统之间的稳定性变化——氢键、卤素键和弱键共晶——发现与化学直觉相反,氢键或卤素键相互作用的存在不一定是稳定性的良好预测指标。最后,我们研究了相对稳定性与简单化学描述符的相关性:填充效率和氢键强度的变化。我们发现与化学直觉有一些广泛的定性一致——具有更强氢键的更密集堆积的共晶体往往更稳定——但这种关系很弱,这表明这种简单的描述符不能捕捉驱动共结晶的相互作用的复杂平衡。我们的结论表明,虽然共结晶通常是一个热力学有利的过程,但仍然难以制定指导合成的一般规则,突出了高级计算在预测和合理化此类系统中的持续重要性。我们发现与化学直觉有一些广泛的定性一致——具有更强氢键的更密集堆积的共晶体往往更稳定——但这种关系很弱,这表明这种简单的描述符不能捕捉驱动共结晶的相互作用的复杂平衡。我们的结论表明,虽然共结晶通常是热力学有利的过程,但仍然难以制定指导合成的一般规则,突出了高级计算在预测和合理化此类系统方面的持续重要性。我们发现与化学直觉有一些广泛的定性一致——具有更强氢键的更密集堆积的共晶体往往更稳定——但这种关系很弱,这表明这种简单的描述符不能捕捉驱动共结晶的相互作用的复杂平衡。我们的结论表明,虽然共结晶通常是热力学有利的过程,但仍然难以制定指导合成的一般规则,突出了高级计算在预测和合理化此类系统方面的持续重要性。
更新日期:2017-12-28
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