Raman spectroscopic and density functional theory studies on a benzothiazole-2-thione derivative

The two tautomers of 7H-[1,3]dioxolo[4′,5′,4,5]benzo[1,2-d]thiazole-6-thione (DBTT) have been investigated by FT-IR and FT-Raman combined with density functional theory (DFT) calculations at the B3LYP level and 6-311+G** basis sets. On the basis of optimized structures, the harmonic force fields, vibrational frequencies and Raman intensities were calculated and scaled. The assignment of the fundamental vibrations for this molecule in its thione form was performed according to the potential energy distribution (PED) analysis. We have also discussed the adsorption behavior of DBTT on gold by means of SERS and DFT calculations at the same level. It revealed that the DBTT exhibited stable conformation of benzothiazole-2-thione (BTT) form both in solid and on gold surfaces; in addition, DBTT molecule is chemisorbed to the gold through both N and the exocyclic S atoms in its thione form and its molecular plane is perpendicular to the surface as BTT. The results show that the substituted groups in the phenyl ring have changed the characters such as the charge density in heterocyclic atoms and so on, but have little influence on the tautomeric preference of the BTT molecule and adsorption orientation on gold.