甲醛与乙腈相互作用的理论研究

Theoretical Study on the Interaction between Formaldehyde and Acetonitril

在HF/ 6 311G(d ,p)、MP2 / 6 311G(d ,p)和B3LYP/ 6 311G(d ,p)水平上 ,对H2 CO和CH3 CN以及设计的 4种结构H2 CO…CH3 CN复合物等进行几何全优化和振动频率计算 ,排除振动频率为负值的非局域极小点结构 ,并对稳定的环状构型复合物结合能进行基组重叠误差校正和零点振动能校正 .分子间相互作用的能量分解分析显示 ,静电能在H2 CO…CH3 CN相互作用能量中占主导地位 ,电荷转移能居第二位 .

The optimization geometries and vibrational frequencies of H2CO, CH3CN and 4 complexes acquired between H,CO and CH3CN have been calculated by using the ab initio method and density functional method at the HF/6-311G(d,p), MP2/6-311G(d,p) and B3LYP/6-311G(d,p) levels. The non-minimum structures with negative vibrational frequencies are excluded. The lowest energy conformer of these complexes is cyclic structure with C-(HO)-O-... and C-(HN)-N-... hydrogen bonds on a common plane. No significant changes are observed in the geometries of the monomers in their complexed state. The most characteristic geometrical properties of the complex are the lengthening of the contacting C- (X = O, N) bonds by 0.1 similar to 0.4 pm and the general shortening of the contacting C-H bonds by 0.1 similar to 0.4 pm with respect to the monomers. The interaction energies of cyclic structure have been corrected by the basis set super-position error (BSSE) using the full Boys-Bernardi counterpoise correction scheme and zero point energy (ZPE). The corrected complex interaction energies of cyclic structure at HF/6-311G(d, p), MP2/6-311G(d, p) and B3LYP/6-311G(d, p) levels are - 8.98, -8.33 and -7.84 kJ/mol, respectively. The interaction energy at the MP2 level is more accurate and the inclusion of correlation effects is important for the description of hydrogen-bonding systems. Nevertheless, for the cases considered here, B3LYP calculations that give a good description of geometric, energetic and electronic properties as compared with MP2 calculation data can be used for investigations of hydrogen-bonded complexes where the MP2 level is not available. The interaction energy indicates that C-(HO)-O-... and C-H-N are weak hydrogen bonds. Although different methods lead to different populations, one might expect that the changes of population both in the uncomplex and complex states would be similar In different methods. The results of Mulliken population analysis and natural bond orbital population analysis reveal that there is only a small charge-transfer in the process of forming the complex. The results of molecular interaction energy decomposition analysis show that the electrostatic interaction plays an essential role in stabilizing the (H2COCH3CN)-C-... complex.