Physical and Theoretical Chemistry, University of Saarland, 66123 Saarbrücken, Germany.
J Phys Chem A. 2010 May 13;114(18):5823-9. doi: 10.1021/jp9102096.
Different isomers and tautomers of methylphosphino- and phenylphosphino-substituted cyclic imidazoline, oxazoline, and thiazoline have been investigated theoretically in gas and aqueous phases. Special emphasis is put on the relative total energies and on the changes in the structure due to substitution or solvation. The calculations were carried through using the B3LYP/6-31+G(d,p) method. To include the effects of the solvent, we used the polarizable-continuum approach both without and with the inclusion of explicit water molecules. Lacking experimental information on the systems, the results were compared with those for nitrogen-containing compounds. In gas phase the cyclic moiety of these molecules show clear deviations from planarity. Only moderate changes in the structure due to solvation were found. On the other hand, the solvent affects strongly the relative stability of different tautomers and isomers. The inclusion of explicit water molecules changes the order of stability due to the presence of intermolecular hydrogen bonds. On the basis of the Bader theory of atoms in molecules, we identify the critical points of the hydrogen bonds as well as properties of the electron density at those points. Thereby, we can quantify the strength of the hydrogen bonds. Finally, we report energies of solvation for the systems of our study.
不同的亚甲基膦基和苯基膦基取代的环状咪唑啉、噁唑啉和噻唑啉的异构体和互变异构体已在气相和水相条件下进行了理论研究。特别强调了相对总能量以及取代或溶剂化引起的结构变化。使用 B3LYP/6-31+G(d,p)方法进行了计算。为了包括溶剂的影响，我们使用了无和包含显式水分子的极化连续体方法。由于缺乏对这些系统的实验信息，将结果与含氮化合物的结果进行了比较。在气相中，这些分子的环状部分明显偏离平面。仅发现由于溶剂化而导致的结构的适度变化。另一方面，溶剂强烈影响不同互变异构体和异构体的相对稳定性。由于存在分子间氢键，包含显式水分子会改变稳定性顺序。基于分子中原子的 Bader 理论，我们确定了氢键的临界点以及这些点处电子密度的性质。由此，我们可以量化氢键的强度。最后，我们报告了我们研究的系统的溶剂化能。
