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运用量子化学从头算方法研究了复合物C5H5N…CHX3(X=F,Cl,Br,I)分子间C—H…N和C—H…π氢键.研究表明,在MP2/SDD水平下,分子间C—H…N氢键的形成均使CHX3分子中C—H键伸长,伸缩振动频率减小,形成红移氢键;分子间C—H…π氢键的形成均使CHX3分子中C—H键收缩,伸缩振动频率增大,形成蓝移氢键.振动光谱分析表明,不能根据质子供体分子CHX3的固有偶极矩对C—H键长的导数来判断红移氢键和蓝移氢键.NBO分析表明,超共轭效应占优势,因此形成C—H…N红移氢键;重杂化效应占优势,因此形成C—H…π蓝移氢键.
The C-H ... N and C-H ... π hydrogen bonds between the molecules C5H5N ... CHX3 (X = F, Cl, Br, I) have been studied ab initio using quantum chemistry method. The formation of C-H ... N hydrogen bonds in molecules all make the C-H bonds in CHX3 molecules elongate and the stretching vibration frequency decreases, forming red-shifted hydrogen bonds; the formation of intermolecular C-H ... π hydrogen bonds all make CHX3 molecules The C-H bond shrinks and the stretching frequency increases to form a blue-shift hydrogen bond. Vibrational spectrum analysis shows that the red shift hydrogen bond can not be judged according to the derivative of the intrinsic dipole moment of the proton donor molecule CH- And blue-shifted hydrogen bonds. The analysis of the NBO shows that the hyperconjugation effect predominates, thus forming a C-H ... N redshift hydrogen bond; the heavy-hybrid effect predominates, thus forming a C-H ... π blue shift hydrogen bond.