DFT , MP2 and G3B3 methods were used to compute the adiabatic and vertical ionization potential for some benzaldehydes. The computed results were compared with the experimental data. Validation of the methods were performed using several error metrics and statistical analysis. Results of G3B3 and DFT method showed an excellent agreement with experimental ones. Substitution effect was also studied. Geometrical structure changes of the examined benzaldehydes upon ionization were followed and analyzed.

long-range charge transfer organic compounds are remarkable for having very large hyperpolarizabilities and thus improved nonlinear optical (NLO) properties. p-nitroaniline (pNA) is known as a prototypical NLO organic material. The question answered in this work is the NLO properties of pNA will be improved by introducing an extended π-conjugation chain between the phenyl ring and the two NH2/NO2 terminal? By means of sophisticated ab initio/MP2 calculations, new derivatives of pNA with an extended π-conjugation have been designed by introducing –(CH=CH)nNH2 or –(CH=CH)nNO2 (n = 1–5) chain into pNA. The results indicate that introducing such chains results in smaller energy gaps and transition energies, which lead to a significant improvement in the hyperpolarizability (β_0). The novel pNA derivatives exhibit larger β_0 amplitudes up to 4.67 x 104 au, which is 27-fold greater than that of pNA. Moreover, with increasing the β_0 amplitude, the –(CH=CH)nNO2 chain beats the –(CH=CH)nNH2 chain. It is hoped that this study can provide a help for designing higher performance NLO materials based on pNA.