中文摘要：

使用MP2方法研究了N—H…O=C氢键二聚体的氢键强度，探讨了不同取代基对N—H…O=C氢键强度的影响．研究发现，可以通过改变取代基的供电性或吸电性来调控氢键强度：乙基等供电子基团对N—H…O=C氢键强度的调节作用不大；-NO2等强吸电子基团可极大地改变N—H…O=C氢键强度；质子受体分子中的强吸电子基团如-NO2可使N-H…O=C氢键强度减弱多达2．6kcal／m01．自然键轨道（NBO）分析表明，N-H…O=C氢键强度越强，参与形成氢键的氢原子电荷越正，氧原子电荷越负，单体分子间电荷转移越多，N-H…O=C氢键中氧原子孤对电子n（O）对N—H反键轨道σ＊（N—H）的二阶稳定化能越大．

英文摘要：

Theoretical calculations on a series of the N-H…O=C hydrogen-bonded dimers were carried out using the MP2 method with 6-31＋G^＊＊ , 6-311＋＋G（d,p）, 6-311＋＋G（3df,2p） and aug-cc-pVTZ basis sets, and the effects of substituents on the hydrogen bonding energies were therefore explored. Calculated results indicate that both electron donating groups and electron withdrawing groups can regulate the strength of the N-H…O=C hydrogen bond. We found that the electron donating groups, such as -Et, have little effect on the N-H…O=C hydrogen bond whereas the strong electron withdrawing groups, such as -NO2 on the proton acceptor molecules, can weaken the hydrogen bond as much as 2. 6 kcal/mol. The natural bond orbital analysis （NBO） demonstrates that the stronger the N-H…O=C hydrogen bond, the larger the positive charge of the H atom and the negative charge of the O atom of N-H…O=C hydrogen bond, the more the charge transfer between the two monomers. NBO analysis also shows that the stronger the N-H…O=C hydrogen bond, the stronger the second-order stabilization energies between the oxygen lone pair n（O） and the antibonding σ＊ （N-H） orbital.