Methodologies for computing UV–VIS spectra and nonlinear properties of azo-azulene derivatives

Theoretical calculation of UV–VIS spectra and second order molecular hyperpolarizability the azo-azulene derivatives was calculated. Analysis of the theoretical spectra shows a substantial sensitivity to the backside groups. The theoretically calculated absorption spectral positions are blue shifted in comparison to the experimental spectra. Adjunction of functional methyl group to the seven-membered unsaturated ring in the investigated molecule (4-aminofenilazo-1-guaiazulena) decreases the HOMO–LUMO energy splitting gap and the ground state dipole moment resulting the substantial increase of nonlinear optical (NLO) coefficient in this system comparing to the other samples.

► We report calculation of UV–VIS spectra and NLO properties of azo-azulenes.
► The sum-over-state (SOS) method were used to estimate the NLO properties.
► The electronic properties of isolated molecules were calculated using PM3 method.
► The electronic contribution playing dominant role in the observed NLO properties.
► Methyl group in the seven-membered unsaturated ring increase the NLO coefficient.