The optimized molecular structures, vibrational frequencies, corresponding vibrational assignments, thermodynamic properties, UV-vis spectra and atomic charges of 3-(5-methylthiazol-2-yldiazeny1)-2-phenyl-1H-indole molecule have been investigated using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods at 6-31G (d,p) basis set. The obtained bond lengths and bond angles have been seen to be good agreement with the experimental data. After calculated vibrational frequencies have been compared with each other, the correlation coefficient has been determined. Moreover, we have not only simulated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) but also determined the transition state and energy band gap. Infrared intensities and Raman activities have been also reported. (C) 2010 Elsevier B.V. All rights reserved.