首页> 外文期刊>Journal of Molecular Structure >An ab initio study of the electronic and vibrational properties of pyrazine center dot center dot center dot HX and XH center dot center dot center dot pyrazine center dot center dot center dot HX hydrogen-bonded complexes (X = F, NC, Cl, CN and CCH)
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An ab initio study of the electronic and vibrational properties of pyrazine center dot center dot center dot HX and XH center dot center dot center dot pyrazine center dot center dot center dot HX hydrogen-bonded complexes (X = F, NC, Cl, CN and CCH)

机译:从头开始研究吡嗪中心点中心点中心点HX和XH中心点中心点中心点吡嗪中心点中心点中心点HX氢键配合物(X = F,NC,Cl,CN和CCH)

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摘要

Ab initio molecular orbital calculations have been performed at the MP2/6-31 + + G** theoretical level in order to obtain molecular properties of hydrogen-bonded complexes involving pyrazine and the HX linear acids with, X = F, NC, Cl, CN, and CCH. Both the 1: 1 and 1:2 adducts have been investigated, i.e., Pyz center dot center dot center dot HX and XH center dot center dot center dot Pyz center dot center dot center dot HX. The H-bond strength for these complexes can be interpreted in terms of the H-X stretching frequency downward displacement. This latter shows a good linear correlation with the intermolecular charge transfer and follows the order: X = F > X = NC > X = Cl > X = CN > X = CCH. As expected, the H-X stretching intensity is much enhanced upon H-bond formation. Here these effects on the HX infrared spectra are much more pronounced than those previously found in complexes with unsaturated hydrocarbons as proton acceptors. On the other hand, no important change has been verified in pyrazine, except the inhibition of the lone-pair trans effect from the lone-pair of nitrogen to the sigma* antibonding orbital of the CC chemical bond in pyrazine. The new vibrational modes arising from complexation show several interesting features, specially the bending modes of the proton-donor molecule and the intermolecular stretching mode. (c) 2005 Elsevier B.V. All rights reserved.
机译:为了获得涉及吡嗪和HX线性酸的氢键配合物的分子特性,已在MP2 / 6-31 + + G **的理论水平上进行了从头算的分子轨道计算,其中X = F,NC,Cl, CN和CCH。已经研究了1:1和1:2加合物,即Pyz中心点中心点中心点HX和XH中心点中心点中心点中心Pyz中心点中心点中心点HX。这些配合物的氢键强度可以用H-X拉伸频率向下位移来解释。后者显示出与分子间电荷转移的良好线性相关性,并遵循以下顺序:X = F> X = NC> X = Cl> X = CN> X = CCH。如所期望的,在形成H键时,H-X拉伸强度大大提高。在这里,这些对HX红外光谱的影响比以前在以不饱和烃作为质子受体的配合物中发现的影响要明显得多。另一方面,除了抑制从氮的孤对到吡嗪中CC化学键的σ*抗键轨道的孤对反式作用以外,吡嗪没有得到重要的改变。络合产生的新振动模式表现出几个有趣的特征,特别是质子给体分子的弯曲模式和分子间拉伸模式。 (c)2005 Elsevier B.V.保留所有权利。

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