Impact of substituents at the para position of C-Nitroso over N-Nitroso diphenylamine on static and frequency dependent nonlinear optical Properties: DFT and TD-DFT

The nonlinear optical property of N and C-nitroso diphenylamine is the focus of the current work but the D-π-A skeleton-based para substituted nitroso benzene served as the starting point for this investigation. For p-methoxy nitroso benzene, a maximum β0 of 10.47 x 10-30 esu was attained. Diphenylamine analogue was letter on chosen for further improvement. For these nitroso diphenylamines, substituent effects of electron donating groups (EDGs) at the para position have been studied for the nonlinear optical property (NLO). The NMe2 derivative of C-nitroso was found to have the highest value of hyperpolarizability (β0) of 57.46 × 10-30 esu, including 570 × 10-30 Debye.esu as molecular hyperpolarizability (µ×β0), out of these two nitroso forms with substituents Me, OMe, OEt, NH2, and NMe2 at para position. H < Me < OMe < OEt < NH2 < NMe2 is the ascending effect for the β0 in the N-nitroso whereas H < Me < OMe < NH2 < OEt < NMe2 in the C-nitroso. These β0 value shows 155.29, 73.69, 13.12 fold increment as compared to diphenylamine (DPA), urea and p-nitroaniline (PNA) respectively. Upon increasing the λmax, value of calculated βTDω also increases calculated in TD-DFT calculations (βTD1064 < βTD1340 < βTD1460 < βTD1907). These values have shown a deviation range of 7–38 % in case of N-nitroso and 11–52 % in case of C-nitroso as compared to static values. Whereas βHRSω increases with increase in the optical frequency (βHRS1064 > βHRS1340 > βHRS1460 > βHRS1907). These values have shown a deviation range of 4–91 % in case of N-nitroso and 1to > 100 in case of C-nitroso as compared to static values.