Solvent control of the soft angular potential in hydroxyl-pi hydrogen bonds: inertial orientational dynamics.
Solvent control of the soft angular potential in hydroxyl-pi hydrogen bonds: inertial orientational dynamics.
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DOI：
10.1021/jp907616x
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发表时间：
2009-10-08
期刊：
影响因子：
--
通讯作者：
Fayer MD
中科院分区：
文献类型：
--
作者：
Rosenfeld DE;Gengeliczki Z;Fayer MD
利用超快偏振和波长选择红外泵浦-探测光谱技术研究了π-氢键复合物的惯性和长时间取向动力学。惯性取向弛豫对与氢键相关的角势敏感。所研究的配合物由苯酚-OD（氘代羟基氢）和具有不同供电子或吸电子取代基的各种π碱溶剂（氯苯、溴苯、苯、甲苯、对二甲苯、均三甲苯、1-戊炔）组成。不同的取代基提供了氢键强度的实验控制。在每条线的中心频率处测量的复合物的惯性取向弛豫与氢键强度无关，表明OD惯性动力学以及因此氢键角势对氢键强度的不敏感性。通过与溶剂的相互作用，OD拉伸吸收带不均匀地加宽。氢键复合物都有类似的波长依赖的惯性取向弛豫跨越其不均匀加宽的OD拉伸吸收线。由于局部溶剂结构和角势之间的相关性，每条线上的惯性重取向的波长依赖性出现。这两个结果表明，局部溶剂结构作为控制的影响，在确定惯性取向弛豫的程度，因此角势，和π-氢键强度的变化是次要的。
Ultrafast polarization and wavelength selective IR pump-probe spectroscopy is used to measure the inertial and long time orientational dynamics of π-hydrogen bonding complexes. Inertial orientational relaxation is sensitive to the angular potential associated with the hydrogen bond. The complexes studied are composed of phenol-OD (hydroxyl hydrogen replaced by deuterium) and various π-base solvents with different electron donating or withdrawing substituents (chlorobenzene, bromobenzene, benzene, toluene, p-xylene, mesitylene, 1-pentyne). The different substituents provide experimental control of the hydrogen bond strength. The inertial orientational relaxation of the complexes, measured at the center frequency of each line, is independent of the hydrogen bond strength, demonstrating the insensitivity of the OD inertial dynamics, and therefore the H-bond angular potential, to the hydrogen bond strength. OD stretch absorption bands are inhomogeneously broadened through interactions with the solvent. The hydrogen bonding complexes all have similar wavelength dependent inertial orientational relaxation across their inhomogeneously broadened OD stretch absorption lines. The wavelength dependence of the inertial reorientation across each line arises because of a correlation between local solvent structure and the angular potential. These two results imply that local solvent structure acts as the controlling influence in determining the extent of inertial orientational relaxation, and therefore the angular potential, and that variation in the π-hydrogen bond strength is of secondary importance.
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