Solvatochromic, optical and dielectric behavior of an aromatic azomethine: Experimental and computational insight

The solvatochromic behavior of p-phenylbenzylidene-p’-butylaniline (PBBA) has been studied using electronic absorption spectra in solvents of varying polarities. The solvent-solute interactions were discussed by means linear solvation energy relationship involving refractive index, dielectric constant, Kamlet-Taft and Catalan models. The validity of the multiparametric methods was verified based on the linearity of the plot of calculated and experimental wavelengths of the absorption maxima. Multiparametric analysis indicated that the dispersion-induction interactions are primarily responsible in controlling the absorption spectral shifts. The origin of the solvatochromism and the electronic excitation were analyzed using the (time dependent)-density functional methods, in several implicit solvents. The experimental data were generally in agreement with the (TD)- mPW1PW91/6-311+G(d,p)/IEFPCM method. Optical properties were studied by UV-Vis absorption spectroscopy, which revealed a bandgap energy of 3.02 eV and an Urbach energy of 40.48 meV. Also, the dielectric properties of this crystalline azomethine were investigated. The values of the dielectric constant does not depend on frequency in the range ν > 10 2 Hz. At low frequencies, a significant increase of the dielectric constant occurs both in the heating and cooling regime as the temperature increases.