In this essay, three novel nonlinear optical (NLO) azo-materials containing indole and sulfonyl based chromophores were studied in-depth by using Fourier transform (FT) IR, FT-Raman spectra and density functional theory (DFT). The scaled theoretical results were shown to be in good agreement with the experimental data. In addition, the computed 1H nuclear magnetic resonance (NMR) and UV–vis absorption wavelengths were also discussed compared with experimental data. The large β values calculated by the DFT methods showed that the studied molecules were good NLO materials, and the molecule which owned a larger substituent group on the indole chromophore moieties had a larger value. Furthermore, simultaneous infrared and Raman activity suggested that intramolecular charges might transfer through the conjugated framework from the electronic donor group to electronic acceptor group. The HOMO–LUMO gap analysis and molecular electrostatic potential (MEP) maps also supported this viewpoint.Graphical abstractThe simultaneous strong Raman and infrared activity of some vibrations suggests that the charge transfer through the conjugated framework from the donor to acceptor group and the HOMO–LUMO analysis gives the supported information.Highlights► FT-IR, FT-Raman, 1H NMR and UV spectra of three novel NLO materials. ► The relationship between structure, β value and NLO properties is discussed. ► The donor and acceptor groups are discussed by vibrational analysis.