甲烷与取代苯弱相互作用的从头算研究

Ab initio study on the weak interactions between methane and substituted benzene

在MP2/6-311G(d,p)和MP2/6-311++G(3d,3p)水平对CH4与C6H5CH3,C6H5OCH3,C6H5SH,C6H5NH2,C6H5OH,C6H5N(CH3)2,C6H5C(CH3)3等给电子取代苯和C6H5F,C6H5Cl,C6H5Br,C6H5I,C6H5CF3,C6H5CN,C6H5COOC2H5,C6H5CHO,C6H5COCH3,C6H5CCl3等吸电子取代苯的相互作用进行了研究。苯环上的取代除了极少数极化率很低的吸电子取代基以外,其它都能增强相互作用。苯环上的取代一般对垂直正对的C-H…π相互作用的方位没有太大的影响。电子相关效应使吸引作用较大增加表明弥散作用相当重要。

Hight- level ab initio molecular orbital calculations were carried out to investigate snbstituent effect of the C- H…π interaction between the methane with the substituted benzene by electron- donatting group： C6H5CH3,C6H5OCH3,C6H5SH.C6H5NH2,C6H5OH,C6H5N（CU3）2,C6H5C（CH3）3,and with the substituted benzene by electron - attrating group： C6H5F,C6H5Cl,C6H5Br,C6H5l,C6H5CF3,C6H5CN,C6H5COOC2H5,C6H5CHO,C6H5COCH3,C6H5CCl3.Intermolecular interaction energies were calculated at the MP2/6- 311G（d,p） and the MP2/6 -311 ＋ ＋ G（3d,3p） level in this work.A large gain of attraction by electron correlation indicates that dispersion interaction is very important. Substitution of hydrogen atoms of benzene by electron - donatting group and electron - attracting group, except the low polarizability flourine atom, increases attractive interaction. Substitution of hydrogen atoms of benzene have little effect to the orientation of C - H…π interaction.