Institut für Physikalische Chemie, Universität Göttingen, Tammannstr. 6, 37077 Göttingen, Germany.
Phys Chem Chem Phys. 2011 Aug 21;13(31):14050-63. doi: 10.1039/c1cp20182d. Epub 2011 Apr 13.
The vibrational dynamics of vacuum-isolated hydrogen-bonded complexes between water and the two simplest alcohols is characterized at low temperatures by Raman and FTIR spectroscopy. Conformational preferences during adaptive aggregation, relative donor/acceptor strengths, weak secondary hydrogen bonding, tunneling processes in acceptor lone pair switching, and thermodynamic anomalies are elucidated. The ground state tunneling splitting of the methanol-water dimer is predicted to be larger than 2.5 cm(-1). Two types of alcohol-water trimers are identified from the spectra. It is shown that methanol and ethanol are better hydrogen bond donors than water, but even more so better hydrogen bond acceptors. As a consequence, hydrogen bond induced red shifts of OH modes behave non-linearly as a function of composition and the resulting cluster excess quantities correspond nicely to bulk excess enthalpies at room temperature. The effects of weak C-H···O hydrogen bonds are quantified in the case of mixed ethanol-water dimers.
采用拉曼和傅里叶变换红外光谱技术，在低温条件下对水与两种最简单的醇形成的氢键隔离复合物的振动动力学进行了研究。阐述了自适应聚集过程中的构象偏好、相对供体/受体强度、弱次级氢键、接受体孤对电子跃迁中的隧道过程以及热力学异常。预测甲醇-水二聚体的基态隧道分裂大于 2.5 cm(-1)。从光谱中鉴定出两种类型的醇-水三聚体。结果表明，甲醇和乙醇作为氢键供体优于水，但作为氢键受体则更优。因此，OH 模式的氢键诱导红移随组成呈非线性变化，所得的簇过量与室温下的体超额焓非常吻合。在混合的乙醇-水二聚体的情况下，对弱 C-H···O 氢键的影响进行了量化。
