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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Vibrational and Quantum Chemical Studies of 1,2-Difluoroethylenes: Spectra of 1,2-~(13)C_2H_2F_2 Species, Scaled Force Fields, and Dipole Derivatives
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Vibrational and Quantum Chemical Studies of 1,2-Difluoroethylenes: Spectra of 1,2-~(13)C_2H_2F_2 Species, Scaled Force Fields, and Dipole Derivatives

机译：1,2-二氟乙烯的振动和量子化学研究：1,2-〜（13）C_2H_2F_2种类，标定力场和偶极子衍生物的光谱

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摘要

Infrared and Raman spectra are reported for cis and trans 1,2-~(13)C_2H_2F_2. Quantum chemical calculations at B3LYP and MP2 levels have been made for cis and trans 1,2-difluoroethylenes, using 6-311G~(**) and 6-311++G~(**) bases. The resulting harmonic force fields for each compound were scaled with nine independent factors, using frequency data corrected, where necessary, for Fermi resonances and for liquid/gas shifts. The previously accepted assignments for v_7 and v_(12) in the trans isomer are interchanged. Several scale factors for bending motions differ markedly between the cis and trans compounds. Centrifugal distortion constants observed with significant accuracy are predicted within 6%. Harmonic contributions to the vibrational dependence of the rotational constants and perpendicular amplitudes are calculated. The C=C and C-H bonds in the cis and trans isomers are essentially identical in respect to length, force constant, and isolated CH stretching frequency. However, the C-F bond is slightly stronger in the cis compound. A revised allocation of observed infrared intensity between the overlapping trans v_7 and v_(12) bands is needed. Directions of (partial deriv)p/(partial deriv)Q for the trans B_u bands are given, which differ from those reported earlier. Magnitudes and directions of the bond dipole derivatives (partial deriv)μ/(partial deriv)r for the CH and CF bonds are obtained from calculated atomic polar tensors. In both cis and trans isomers, the vector (partial deriv)μ/(partial deriv)r_(CF) lies within 17°of the bond direction, but for the CH bond, (partial deriv)μ/(partial deriv)r is roughly perpendicular to the CH direction.
机译：报道了顺式和反式1,2-〜（13）C_2H_2F_2的红外和拉曼光谱。使用6-311G〜（**）和6-311 ++ G〜（**）碱，对顺式和反式1,2-二氟乙烯进行了B3LYP和MP2含量的量子化学计算。使用费米共振和液/气位移，在必要时使用校正的频率数据，使用九个独立因子来缩放每种化合物所产生的谐波力场。反式异构体中先前接受的v_7和v_（12）分配是互换的。顺式和反式化合物之间的几种弯曲运动比例因子明显不同。预计以非常高的精度观察到的离心变形常数在6％以内。计算出谐波对旋转常数和垂直振幅的振动依赖性的影响。顺式和反式异构体中的C ＝ C和C-H键在长度，力常数和孤立的CH拉伸频率方面基本相同。但是，顺式化合物中的C-F键略强。需要在重叠的跨v_7和v_（12）波段之间修改观察到的红外强度的分配。给出了反B_u波段的（偏导数）p /（偏导数）Q的方向，与先前报道的方向不同。 CH和CF键的键偶极导数（偏导数）μ/（偏导数）r的大小和方向是从计算出的原子极性张量获得的。在顺式和反式异构体中，矢量（偏导数）μ/（偏导数）r_（CF）位于键方向的17°内，但对于CH键，（偏导数）μ/（偏导数）r为大致垂直于CH方向。

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