Matousek Jirí, Cajan Michal, Kulhánek Petr, Koca Jaroslav
National Centre for Biomolecular Research, Masaryk University, CZ-611 37 Brno, Czech Republic.
J Phys Chem A. 2008 Feb 7;112(5):1076-84. doi: 10.1021/jp710236g. Epub 2008 Jan 9.
Possible rearrangement mechanisms of hydrogen-bond arrays formed at the lower rim of tetrahydroxycalix[4]arene and tetrahydroxythiacalix[4]arene were studied by means of density functional theory and the resolution identity approximation modification of Møller-Plesset perturbation theory (RI-MP2). Influence of solvent to height of energy barriers was quantified by use of the conductorlike screening model (COSMO) of implicit solvent (chloroform). Generally, two types of mechanisms were investigated. The first is represented by a synchronous single-step jump of all four hydroxyl protons. Pathways of the second mechanism include the rotation of one or more hydroxyl groups around the CAr-O bond. Theoretical results, in agreement with recently published experimental data (Lang et al. J. Chem. Phys. 2005, 122, 044056), prefer a jump mechanism for the methylene-bridged calix[4]arene. Concerning the thiacalix[4]arene, results obtained by COSMO as well as RI-MP2 calculations show that the rotational mechanism is very competitive and it could even be more favorable.
利用密度泛函理论以及对莫勒-普莱塞特微扰理论（RI-MP2）的分辨率恒等式近似修正，研究了在四羟基杯[4]芳烃和四羟基硫杂杯[4]芳烃下缘形成的氢键阵列可能的重排机制。使用隐式溶剂（氯仿）的类导体屏蔽模型（COSMO）来量化溶剂对能垒高度的影响。一般来说，研究了两种类型的机制。第一种机制表现为所有四个羟基质子同步单步跳跃。第二种机制的途径包括一个或多个羟基围绕CAr-O键的旋转。理论结果与最近发表的实验数据（Lang等人，《化学物理杂志》，2005年，122卷，044056期）一致，支持亚甲基桥连杯[4]芳烃的跳跃机制。关于硫杂杯[4]芳烃，通过COSMO以及RI-MP2计算得到的结果表明，旋转机制非常有竞争力，甚至可能更有利。
