Synthesis and structure of a novel hetarylazoindole dye studied by X-ray diffraction, FT-IR, FT-Raman, UV–vis, NMR spectra and DFT calculations

A novel hetarylazoindole dye, 1,2-dimethyl-3-(pyridin-3-yldiazenyl)-1H-indole (DMPI) was synthesized by coupling 1,2-dimethylindole with diazotized 3-aminopyridine. The dye was characterized by FT-IR, FT-Raman, UV–vis, 1H NMR, 13C NMR and X-ray diffraction techniques. The structure of the dye was determined by X-ray single crystal diffraction method. The molecular geometry, Gauge including atomic orbital (GIAO) 1H- and 13C NMR chemical shift values and vibrational frequencies of DMPI molecule in the ground state were calculated by using the density functional theory (DFT). The theoretical electronic absorption spectra were calculated using time-dependent density functional theory (TD-DFT). The total energy distributions (TED) of the vibrational modes were calculated by using scaled quantum mechanical (SQM) analysis.