Conformations of 2-thiouracil in the aqueous solution and its adsorption behavior on the gold substrates explored by DFT calculations and experimental methods

作者：Yang Wenpeng; Hu Yongjun^*

来源：Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy , 2015, 134: 399-405.

DOI：10.1016/j.saa.2014.06.119

• 2-Thiouracil
• Adsorption
• Gold substrates
• Surface-enhanced Raman spectroscopy
• Density functional theory

2-Thiouracil, a thio-derivative of uracil, may appear in various tautomeric forms due to the different positions of protons. In this paper, the adsorption behavior and conformations of 2-thiouracil on the gold substrates are inspected by means of surface-enhanced Raman scattering (SEAS) and density functional theory (DFT) calculations. The results indicate that all the enhanced bands are assigned to in-plane vibration modes. Besides, most of the bands related to N and S atoms are significantly enhanced and have obvious shifts in the SEAS spectra. Furthermore, the C=O stretching band at 1695 cm(-1) also appears in the SEAS spectra. The theoretical SERS spectra of 2TU-Au-4 and 2TU2-Au-4 complexes agree well with the experimental SEAS spectra of 2-thiouracil at 0.04 mM. Meanwhile, We calculate that the binding energies for 2TU2-Au4 and 2TU-Au4 are ca. 70 and 50 kcal/mol, respectively. Those results above imply that the 2TU and 2TU2 conformers can exist stably in the aqueous solution and both of them are vertically chemisorbed on the gold surfaces. For the 2TU, it is adsorbed on the gold surfaces through N1H position and the sulfur atom. While the 2TU2 adsorbed on the gold substrates through the N1 site and its deprotonated sulfur atom.

• 单位
  华南师范大学