DFT exploration of the solvent-dependent electronic and nonlinear optical properties of naphthyridine-stilbene dyads

This article presents a series of push-pull chromophores (NS1-NS10) based on naphthyridine-stilbene dyad, designed for nonlinear optical (NLO) applications in photonics and optoelectronics. The study utilizes density functional theory (DFT) and time dependent-DFT (TD-DFT) to assess the influence of solvent polarity on first, second, and third-order static and dynamic polarizabilities, natural transition orbitals, and UV-Visible absorption spectra of these compounds. For the parent naphthyridine-stilbene compound (NS), it was found that the NLO properties improve with different acceptor group substitutions. The reduction in the energy gap between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) has promoted effective intramolecular charge transfer in the designed compounds. The NLO analysis revealed that NS3, NS4, and NS10 exhibit first, second, and third-order NLO behaviors, while NS1, NS2, NS5, and NS6 show second-order NLO activity. NS8 and NS9 display both first and third-order NLO responses, with NS6 also exhibiting first-order NLO behavior and NS2 displaying third-order NLO properties. The solvent effects on the dipolar and octupolar contributions to the first-order hyperpolarizabilities highlight the dominant dipolar character of the designed compounds. The computed NLO parameters for the designed structures, which are comparable to those of structurally similar compounds known for their NLO performance, highlight their potential as promising candidates for photonic and optoelectronic applications.