Hydrophobic Molecules Slow Down the Hydrogen-Bond Dynamics of Water
Hydrophobic Molecules Slow Down the Hydrogen-Bond Dynamics of Water
复制标题
DOI：
10.1021/jp107881j
复制
发表时间：
2011-03-17
影响因子：
2.9
通讯作者：
Petersen, Christian
中科院分区：
文献类型：
--
作者：
Bakulin, Artem A.;Pshenichnikov, Maxim S.;Petersen, Christian
我们研究了HDO分子在叔丁醇(TBA)、三甲胺氧化物(TMAO)和四甲基尿素(TMU)等稀水溶液(HDO：D2O和HDO：H2O)中的光谱和取向动力学。用飞秒二维红外光谱研究了光谱动力学，用飞秒偏振分辨振动泵浦探测光谱研究了定向动力学。我们观察到随着溶质浓度的增加，吸收谱线中心部分附近的光谱扩散明显减慢。在低浓度下，随着甲基数目的增加，水分呈现缓慢的光谱动力学，这表明这种影响是由于溶质分子中甲基的水化壳层中氢键动力学的缓慢所致。振动频率动力学的减慢与水分子取向迁移率的减慢密切相关。这种关联表明，疏水分子基团对水的氢键动力学的影响具有共同的根源。
We study the spectral and orientational dynamics of HDO molecules in solutions of tertiarybutyl-alcohol (TBA), trimethyl-amine-oxide (TMAO), and tetramethylurea (TMU) in isotopically diluted water (HDO:D2O and HDO:H2O). The spectral dynamics are studied with femtosecond two-dimensional infrared spectroscopy and the orientational dynamics with femtosecond polarization-resolved vibrational pump probe spectroscopy. We observe a strong slowing down of the spectral diffusion around the central part of the absorption line that increases with increasing solute concentration. At low concentrations, the fraction of water showing slow spectral dynamics is observed to scale with the number of methyl groups, indicating that this effect is due to slow hydrogen-bond dynamics in the hydration shell of the methyl groups of the solute molecules. The slowing down of the vibrational frequency dynamics is strongly correlated with the slowing down of the orientational mobility of the water molecules. This correlation indicates that these effects have a common origin in the effect of hydrophobic molecular groups on the hydrogen-bond dynamics of water.