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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Discrimination of Rotational Isomers of 2-Phenylethanol by Dispersed Fluorescence Spectroscopy
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Discrimination of Rotational Isomers of 2-Phenylethanol by Dispersed Fluorescence Spectroscopy

机译：分散荧光光谱法鉴别2-苯基乙醇的旋转异构体

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摘要

Laser-induced dispersed fluorescence (DF) spectra for excitations of several low-energy bands near the S_1 origin (0_0~0) of 2-phenylethanol have been measured in a supersonic free jet expansion. The spectrum measured for excitation of a weak band at 0_0~0+48 cm~(-1) has been found to resemble the 0_0~0-excited emission spectrum. This weak band has been assigned to the S_1 ← S_0 origin of a higher energy conformer. Spectral analyses with the aid of ab initio (DFT/B3LYP/6-311++G~(**)) calculations reveal that the frequencies of the benzenoid 6a and a few other ring vibrational modes are sensitive to molecular shape. Comparisons of these frequencies with those obtained by theoretical calculations suggest that the higher energy species is the anti conformer of the molecule. This conformational assignment based on vibronic analysis agrees with the quantum chemistry predictions at the MP2/cc-pVTZ level of theory that the anti is the second preferred conformational isomer having 7.03 kJ/mol more energy than the most stable gauche form. No spectral feature corresponding to emission from an excited 1:1 water complex of the molecule was apparent in the dispersed fluorescence when the exciting laser was tuned across the 0_0~0+48 cm~(-1) band. This behavior is in contrast to conclusions of two previous studies that the 48 cm~(-1) band in the LIF excitation spectrum is due to a 1:1 water complex.
机译：在超音速自由射流扩展中已测量了激光诱导的分散荧光（DF）光谱，用于激发2-苯基乙醇的S_1起源（0_0〜0）附近的几个低能带。已发现在0_0〜0 + 48 cm〜（-1）处激发弱带所测得的光谱类似于0_0〜0激发的发射光谱。该弱带已分配给更高能量构象体的S_1←S_0起源。借助从头算（DFT / B3LYP / 6-311 ++ G〜（**））进行的频谱分析表明，苯并合物6a的频率和其他一些环振动模式对分子形状敏感。这些频率与通过理论计算获得的频率的比较表明，较高能的物种是分子的反构象体。这种基于振动电子分析的构象分配与理论上MP2 / cc-pVTZ水平上的量子化学预测相符，该反义是第二种优选的构象异构体，其能量比最稳定的薄纱形式高7.03 kJ / mol。当在0_0〜0 + 48 cm〜（-1）波段上调谐激发激光时，在分散的荧光中没有明显的与分子1：1的水复合物的发射对应的光谱特征。这种行为与先前两项研究得出的结论相反：LIF激发光谱中的48 cm〜（-1）谱带是由1：1水络合物引起的。

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