Acta Chimica Sinica ›› 2004, Vol. 62 ›› Issue (19): 1963-1967. Previous Articles     Next Articles

7-硫代鸟嘌呤互变异构体的密度泛函理论计算

李宝宗   

  1. 苏州大学化学化工学院, 苏州, 215006
  • 投稿日期:2004-02-26 修回日期:2004-06-03 发布日期:2014-02-17
  • 通讯作者: 李宝宗,E-mail:Ymguo@suda.edu.cn E-mail:Ymguo@suda.edu.cn
  • 基金资助:
    国家自然科学基金(No.20171034)资助项目.

Density Functional Theory Calculations on 7-Thioguanine Tautomers

LI Bao-Zong   

  1. School of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215006
  • Received:2004-02-26 Revised:2004-06-03 Published:2014-02-17

Molecular structures of fourteen 7-thioguanine tautomers were calculated by the B3LYP/6-311G** method, both in the gas and aqueous phases, with full geometry optimization. The Onsager solvate theory model was employed for aqueous solution calculations. The structures, total energy, standard enthalpy, standard entropy and standard free energy were obtained. The calculations show that 7-thioguanine existing as the thione form is the predominant isomers in the gas and aqueous phases. The thione-N(6)(H) isomer is more stable than the thione- N(4)(H) isomer in the gas phase whereas the thione-N(4)(H) isomer is more stable than the thione-N(6)(H) isomer in the aqueous phase. The results are in good agreement with available experimental results. The entropy effect on the Gibbs free energy of 7-thioguanine base is very small and there is little significance for the tautomeric equilibria of the base. The enthalpic term is dominant in the determination of tautomeric equilibria. The free energy of solvation is well correlated with the dipole moments of 7-thioguanine tautomers.

Key words: 7-thioguanine, tautomer, DFT method, SCRF method, dipole moment