Dominikowska Justyna, Rybarczyk-Pirek Agnieszka J, Fonseca Guerra Célia
Theoretical and Structural Chemistry Group, Department of Physical Chemistry, Faculty of Chemistry, University of Lodz, Pomorska 163/165, 90-236 Łódź, Poland.
Department of Theoretical Chemistry and Amsterdam Centre for Multiscale Modelling, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
Cryst Growth Des. 2021 Jan 6;21(1):597-607. doi: 10.1021/acs.cgd.0c01410. Epub 2020 Dec 16.
We have investigated 44 crystal structures, found in the Cambridge Structural Database, containing the X synthon (where X = Cl, Br, I) in order to verify whether three type II halogen-halogen contacts forming the synthon exhibit cooperativity. A hypothesis that this triangular halogen-bonded motif is stabilized by cooperative effects is postulated on the basis of structural data. However, theoretical investigations of simplified model systems in which the X motif is present demonstrate that weak synergy occurs only in the case of the I motif. In the present paper we computationally investigate crystal structures in which the X synthon is present, including halomesitylene structures, that are usually described as being additionally stabilized by a synergic interaction. Our computations find no cooperativity for halomesitylene trimers containing the X motif. Only in the case of two other structures containing the I synthon a very weak or weak synergy, i.e. the cooperative effect being stronger than -0.40 kcal mol, is found. The crystal structure of iodoform has the most pronounced cooperativity of all investigated systems, amounting to about 10% of the total interaction energy.
我们研究了剑桥结构数据库中44个含有X合成子（其中X = Cl、Br、I）的晶体结构，以验证形成该合成子的三种II型卤素-卤素接触是否表现出协同性。基于结构数据推测出这样一个假设：这种三角形卤素键合基序是由协同效应稳定的。然而，对存在X基序的简化模型系统的理论研究表明，只有在I基序的情况下才会出现微弱的协同作用。在本文中，我们通过计算研究了存在X合成子的晶体结构，包括卤代均三甲苯结构，这些结构通常被描述为通过协同相互作用而得到额外稳定。我们的计算结果表明，含有X基序的卤代均三甲苯三聚体不存在协同性。仅在另外两个含有I合成子的结构中发现了非常微弱或微弱的协同作用，即协同效应强于-0.40 kcal/mol。在所有研究的体系中，碘仿的晶体结构具有最显著的协同性，约占总相互作用能的10%。
