Photophysical and nonlinear optical properties of para-substituted nitrobenzofurazan: A comprehensive DFT investigation

We investigate the ability of the 4-chloro-7-nitrobenzofurazan (NBD-Cl) to append Pyrrolidine (Pyrr), a secondary amine, acting as a nucleophile group in SNAr reactions resulting in the fluorescent NBD-Pyrr compound. Their electrochemical and photo-physical responses have been thoroughly investigated using Cyclic Voltammetry (CV), UV–Visible, photoluminescence (cw-PL) and time resolved photoluminescence (TR-PL) spectroscopies. The intra-molecular charge transfer associated to nonlinear optical (NLO) properties of NBD-Pyrr molecule has reported, for the first time. Important NLO parameters such as dipole moment (μ), polarizability (α), anisotropy of polarizability (Δα) and first and second order hyperpolarizabilities (β and γ) are calculated at the B3LYP/6–31 + g(d,p) level of theory as well. Additionally, natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM), Hirshfeld surface (HS), Electron Localization Function (ELF), and Localized orbital locator (LOL) analyses have been used to illustrate structure and bonding in the NBD-Pyrr molecule.