The synthesis, characterisation and molecular structure of a new hetarylazoindole dye studied by X-ray diffraction, spectral analysis and density functional theory calculation

1,2-Dimethyl-3-(5-methylisoxazol-3-yldiazenyl)-1H-indole was obtained by coupling 3-amino-5-methylisoxazole with diazotised 1,2-dimethylindole. It was characterised by proton and carbon nuclear magentic resonance, ultraviolet-visible, infrared and Raman spectra, and the X-ray single crystal diffraction method. On the theoretical side, the molecular geometry, chemical shifts and the fundamental vibrational frequencies were evaluated using density functional theory. Time-dependent density functional theory was used to evaluate the electronic excitation spectra. In addition, the scaled quantum mechanical approach was used to study the total energy distributions of the vibrational modes of the molecule. The results showed that the general agreement between experimental and calculated geometric parameters, chemical shifts and lambda(max) values are good. Excellent agreement was found between the calculated and experimental vibrational frequencies.