摘要
对胸腺嘧啶 BH3复合物分别用B3LYP/6 31G(d)和MP2/6 31G(d)进行计算,以预测该复合物的构型 及结合能,得到了5种构型,并进行了振动分析和自然键轨道分析.对各构型进行了更大基组(6 311+G(2df)和 aug cc pVDZ)的单点能量计算.结果表明,B原子与O原子直接相连的构型(a)、(b)比较稳定,其结合能为90.4 和88.0kJ/mol(B3LYP/6 31G(d),BSSE校正).N原子向B原子的空轨道提供电子形成构型(c)和(d),只找到 了一种由C原子向B原子提供π电子的构型(e).所有构型中均存在电荷授受,各构型的结合能与电荷转移量有 良好的相关性.复合物的形成,使其红外光谱均有不同程度的红移,红移幅度与复合物的稳定性相关.
Geometries and combination energies are predicated at B3LYP/6-31G(d) and MP`22/6-31G(d) level for thymine-BH3 complexes and 5 geometries have been obtained. Then single point energy calculations using larger basis sets (6-311 + G(2df) and aug-cc-pVDZ) and vibrational analysis and natural bond orbital analysis are carried out on the 5 optimized conformers. The outcome indicates that the conformers with the boron atom combined with O directly are relatively stable ones, ( a) and ( b), with the combination energies of 90. 4 and 88. 0 kJ/mol ( B3LYT/6-31G(d) BSSE corrected). The fact is that the nitrogen atom offers electron to the empty atomic orbital of boron which produces the conformers (c) and (d). Only one conformer is found which is formed because two carbon atoms offer pi, electron to the empty orbital of boron. The charge transference exists in all the conformers. The combination energies have a good line relation with their charge transference. The calculated results show that when the complex forms their 1R spectrum moved to the red side and the frequency shifts are relative to the stabilites of the complexes.
基金
ProjectsupportedbytheNationalScienceFoundationofChina(20171031)andtheFoundationforKeyTeachersinUniversityofEducationOfficeofShandongProvince
