Electronic absorption and vibrational spectra and nonlinear optical properties of 4-methoxy-2-nitroaniline.

FT-Raman, IR and UV-vis spectroscopies have been applied to investigate the potential nonlinear optical (NLO) material 4-methoxy-2-nitroaniline. A detailed interpretation of the vibrational spectra was carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. Density functional theory is applied to explore the nonlinear optical properties of the molecule. The study suggests the importance of pi-conjugated systems for nonlinear optical properties and the possibility of charge transfer interactions. Good consistency is found between the calculated results and experimental data for the electronic absorption, IR and Raman spectra. The solvent effects have been calculated using time-dependent density functional theory in combination with the polarized continuum model, and the results are in good agreement with experimental measurements. The calculations reveal that incorporation of substituents (amino, nitro and methoxy) has a strong influence on the structure and spectroscopic properties of the molecule, and the effect of electron charge transfer was examined by natural bond orbital population analysis.