Departament d'Enginyeria Química, E. T. S. d'Enginyeria Industrial de Barcelona, Universitat Politècnica de Catalunya, Diagonal 647, Barcelona 08028, Spain.
J Comput Chem. 2010 Jun;31(8):1741-51. doi: 10.1002/jcc.21463.
Three different strategies have been followed to develop the torsional force-field parameters of the inter-ring dihedral angles for calix[4]arene-substituted poly(thiophene)s, a family of highly sensitive ion receptors. These procedures, which are based on the rotational profiles calculated using quantum mechanical methods, differ in the complexity of the model compounds and the processing applied to the quantum mechanical energies before the fitting. The performance of the three sets of developed parameters, which are essentially compatible with the General Amber Force Field, has been evaluated by computing the potential of mean forces for the inter-ring rotation of 2,2'-bithiophene, and its substituted analog bearing a calix[4]arene group in different environments. Finally, the ability of the new sets of torsional parameters to describe a calix[4]arene-substituted poly(thiophene) in tetrahydrofuran solution has been checked using Molecular Dynamics simulations. Specifically, the molecular shape, the polymer conformation, and the effects of the Na(+) ions trapped in the cavity of the receptor have been examined. Although the potential derived from unsubstituted 2,2'-bithiophene is able to reproduce the experimental free energies of the minima, the overall results indicate that the parameters derived from the analog bearing a calix[4]arene group provide the best description of the systems under study. This should be attributed to the strong constraints found in complex substituted poly(thiophene)s, which require parameterization strategies able to capture all the interactions and phenomena involved in their inter-ring rotations.
为了开发杯[4]芳烃取代聚噻吩这类高灵敏度离子受体中环间二面角的扭转力场参数，我们采用了三种不同的策略。这些方法基于量子力学方法计算的旋转分布曲线，其不同之处在于模型化合物的复杂程度和拟合前应用于量子力学能的处理方式。三套开发参数的性能通过计算 2,2'-联噻吩及其在不同环境下带有杯[4]芳烃基团的取代类似物中环间旋转的平均力势来进行评估。最后，通过分子动力学模拟检查了新的扭转参数集在四氢呋喃溶液中描述杯[4]芳烃取代聚噻吩的能力。具体来说，研究了分子形状、聚合物构象以及被困在受体空腔中的 Na(+)离子的影响。尽管未取代的 2,2'-联噻吩的势能能够重现实验得到的最小自由能，但总体结果表明，带有杯[4]芳烃基团的类似物的参数提供了对所研究体系的最佳描述。这归因于复杂取代聚噻吩中存在的强约束，这些约束需要能够捕获其环间旋转所涉及的所有相互作用和现象的参数化策略。
