Theoretical study of the stability and reactivity of nitro-coumarins and amino-coumarins by DFT method

Abstract

The nitration reaction was applied to synthesize new substituted coumarin derivatives which undergo a reduction reaction to give the corresponding amino-coumarins. The structures of the nitro-coumarins and amino-coumarins were elucidated by ¹H, ¹³C NMR and infrared spectroscopy. The reactivity indices of the target molecules were computed with conceptual density functional theory framework using DFT/B3PW91/6-31G(d, p). The computed data in terms of ¹H NMR and IR of all the synthesized nitro-coumarins (N1–N3) and amino-coumarins (A1–A3) were compared to the experimental data. Nitro-coumarin (N1) is the least hyperpolarizable of the compound among understudied compounds, making it the most stable and least responsive to nonlinear optics (NLO), while (A1) has the highest hyperpolarizability, making it the least stable and most NLO responsive. Every synthesized compound shows a significant three-dimensional delocalization of the pi-electron, which is crucial for explaining responses to nonlinear optics.