Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (05): 903-910.doi: 10.3866/PKU.WHXB201302272


A-Band Structural Dynamics of 1-Methylthymine

LI Ming-Juan, LIU Ming-Xia, ZHENG Xu-Ming   

  1. Key Laboratory of Advanced Textiles Materials and Manufacturing Technology of the Ministry of Education, and Engineering Research Center for Eco-dyeing and Finishing of Textiles of the Ministry of Education, Department of Chemistry, Zhenjiang Sci-Tech University, Hangzhou 310018, P. R. China
  • Received:2012-12-18 Revised:2013-02-27 Published:2013-04-24
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21033002) and National Key Basic Research Program of China (973) (2013CB834604).


Resonance Raman spectra at five excitations covering the A- and B-band absorptions of 1-methylthymine (MT) were acquired. The Franck-Condon region structural dynamics and electronic transitions of MT were studied in conjunction with density functional theory calculations. The A- and B-band absorptions are assigned as πHπL*/πH-2πL+2* and πHπL+2*/πH-2πL* transitions, respectively, using the B3LYP/6-311 + G(d,p) level of theory. The hyper-conjugation interaction between the CH3 group and pyrimidine ring leads to a noticeable red-shift in λmax of the A-band absorption for MT, relative to that for thymine. It also significantly affects the Franck-Condon region structural dynamics of MT. The A- and B-band resonance Raman spectra are respectively assigned as the 14 and 11 fundamentals, their overtones and combination bands.The A-band resonance Raman intensities of MT are dominated by the v9 (C5=C6 stretching + C6H12 in-plane bending), v16(ring deformation) and v18 (N3C2N1 asymmetric stretching+C4C5C10 asymmetric stretching) modes. This indicates that the structural dynamics of MT are mainly along these reaction coordinates. The effect of solvent on the structural dynamics was examined. The Raman activity of the v8(C4=O9 stretching+N3H11 in-plane bending) vibrational mode is tuned by solvent, and the dependence of the normal mode displacement of v8 on solvent is similar to that for thymine.

Key words: 1-Methylthymine, Structural dynamics, Resonance Raman spectrum, Density functional theory, Vibrational spectrum, Electronic spectrum