Etude en luminescence UV—visible de la p-nitroaniline

The modification spectra of p-nitroaniline were evidenced by dipolar interaction effects and hydrogen bond complexes. This complexation was obtained either with the water traces present as impurity in aprotic solvents at low temperature, or by direct associations with OH groups in protic solvents. It conferred on the molecule a twisted conformation in the ground state due to the rotation of the NH₂ group around the CNH₂ bond. This important result agrees with an anomalous result obtained in emission data which shows dependence of fluorescence/phosphorescence intensity ratio (I_f/I_pn) on excitation energy. It is explained by mixed rotamers that exhibit this molecule in the ground state. The calculated geometry characteristics for this molecule show the ability of some theoretical methods to reproduce accurately the experimental data.