Faculty of Pharmacy, University of Coimbra, 3004-295, Coimbra, Portugal.
J Phys Chem A. 2008 May 22;112(20):4669-78. doi: 10.1021/jp7116196.
Theoretical calculations at the MP2 level, NBO and AIM analysis, and matrix-isolation infrared spectroscopy have been used to investigate the structure of the isolated molecule of 1,4-butanediol (1,4-BDO). Sixty-five structures were found to be minima on the potential energy surface, and the three most stable forms are characterized by a folded backbone conformation leading to the formation of an intramolecular H-bond. To better characterize the intramolecular interactions and particularly the hydrogen bonds, natural bond orbital analysis (NBO) was performed for the four most stable conformers, and was further complemented with an atoms-in-molecules (AIM) topological analysis. Infrared spectra of 1,4-BDO isolated in low-temperature argon and xenon matrixes show a good agreement with a population-weighted mean theoretical spectrum, and the spectral features of the conformers expected to be trapped in the matrixes were observed experimentally. Annealing the xenon matrix from 20 to 60 K resulted in significant spectral changes, which were interpreted based on the barriers to intramolecular rotation. An estimation of the intramolecular hydrogen bond energy was carried out following three different methodologies.
采用 MP2 理论计算、自然键轨道（NBO）分析和 AIM 分析以及矩阵隔离红外光谱法研究了 1,4-丁二醇（1,4-BDO）的孤立分子结构。在势能表面上发现了 65 个稳定结构，其中三种最稳定的形式的特征是折叠的骨架构象，导致形成分子内氢键。为了更好地描述分子内相互作用，特别是氢键，对四个最稳定构象进行了自然键轨道（NBO）分析，并进一步用分子中的原子（AIM）拓扑分析进行了补充。在低温氩气和氙气基质中分离的 1,4-BDO 的红外光谱与加权平均理论光谱吻合较好，实验观察到了预期被困在基质中的构象的光谱特征。从 20 到 60 K 退火氙气基质导致光谱发生显著变化，根据分子内旋转的势垒对其进行了解释。采用三种不同的方法估算了分子内氢键的能量。
