This work deals with the optimized molecular structure, vibrational spectra, nonlinear optic (NLO) and frontier molecule orbital (FMO) properties of 1-Methy1-2-pheny1-3-(1,3,4-thiadiazol-2-yldiazeny1)-1Hindole (MPI) by quantum chemical calculations. The Fourier transform infrared (Fr-MIR and Fr-FIR) and Raman spectra of 1-Methyl-2-phenyl-3-(1,3,4-thiadiazol-2-yldiazenyl)-1H-indole (MPI) were recorded in the region (4000-400 cm(-1) and 400-30 cm(-1)) and (3200-92 cm(-1)), respectively. The analysis and complete vibrational assignments of the fundamental modes of the MPI molecule were carried out by using the observed Fr-IR and Fr-Raman data and calculated Total Energy Distribution (TED) according to Scaled Quantum Mechanics procedure. The calculated geometrical parameters of the MPI molecule are in agreement with the obtained values from XRD studies. On the other hand, the difference between the scaled and observed wavenumber values of the most of the fundamentals are very sma11.1H NMR and 13C NMR chemical shift values, and energy gap between LUMO-HOMO and molecular electrostatic potential (MEP) were investigated by using density functional theory (B3LYP) methods. UV/Visible spectra and X maximum absorption values, the oscillator strengths in the chloroform, methanol and DMSO solvation in combination with different basis sets were calculated by using the time-dependent density functional theory (1D-DFT). Additionally, the predicted nonlinear optical (NLO) properties of the MPI are quite greater than that of urea at the B3LYP/6-31++G(d,p) level. (C) 2016 Elsevier B.V. All rights reserved.