Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (07): 1570-1578.doi: 10.3866/PKU.WHXB201204173

• THERMODYNAMICS, KINETICS, AND STRUCTURAL CHEMISTRY • Previous Articles     Next Articles

Dynamic Structures of 2-Thiopyrimidone and 2-Thiopyridone in B-Band Absorptions

GUO Xiao-Nan1, DU Rui1, ZHAO Yan-Ying1, PEI Ke-Mei1, WANG Hui-Gang1, ZHENG Xu-Ming1,2,3   

  1. 1. Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China;
    2. Key Laboratory of Advanced Textiles Materials and Manufacturing Technology of the Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China;
    3. Engineering Research Center for Eco-dyeing and Finishing of Textiles of the Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China
  • Received:2012-02-07 Revised:2012-04-17 Published:2012-06-07
  • Contact: ZHENG Xu-Ming E-mail:zxm@zstu.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21033002) and National Key Basic Research Program of China (973) (2007CB815203).

Abstract:

The dynamic structures of 2-thiopyrimidone (2TPM) and 2-thiopyridone (2TP) in B-band absorptions were studied using the resonance Raman spectroscopy combined with quantum chemical calculations. In gas phase, 2-thiopyrimidine (2MPM, the thiol form) was more stable than 2TPM (the thione form) by ~15.1 kJ·mol-1, whereas in water and acetonitrile 2TPM was more stable than 2MPM by 29.3 and 28.0 kJ·mol-1, respectively. The transition barrier for the ground state proton transfer tautomerization reaction between 2TPM and 2MPM was ~130 kJ·mol-1 in gas phase on the basis of the B3LYP/6-311++ G(d,p) level of theory calculations. The three absorption bands of 2-thiopyrimidone were respectively assigned as πHπL*, πHπL+1*, and πH-1πL* transitions. The vibrational assignments were carried out for the B-band resonance Raman spectra of 2TPM in water and acetonitrile solvents on the basis of the measurements from the Fourier transform (FT)-Raman and Fourier transform-infrared (FT-IR) spectra of 2TPM in solid and/or in solution phases and B3LYP/6-311++G(d,p) computations. The dynamic structures of 2TPM and 2TP were obtained by analysis of the resonance Raman intensity pattern. The differences in the dynamic structures of 2TPM and 2TP reflected differences in the structures of their ππ*/πσ* conical intersection points, and therefore could be used to provide insight into the photoinduced hydrogen-atom detachment-attachment mechanism.

Key words: Thiol-thione phototautomeric reaction, Resonance Raman spectroscopy, Conical intersection, Excited-state structural dynamics, Vibrational spectrum, Density functional theory

MSC2000: 

  • O641