Computational studies on optoelectronic and nonlinear optical properties of para-substituted nitrobenzofurazan compound

The activated chlorine atom on 4-chloro-7-nitrobenzofurazan (NBD-chloride, NBD-Cl) by piperidine, secondary amine, yields a product of the nucleophilic aromatic substitution (SNAr) in acetonitrile (thereafter named, NBD-Pip). The NBD-Pip was analyzed by stationary photoluminescence (cw-PL) and its time-resolved version (TR-PL) spectroscopy techniques. The Cw-PL spectrum shows the most intense peaks in the range of 700–750 nm. The decay time has been determined from a mono-exponential fit of the experimental data, and it is about 0.75 ns and decreases down to 0.62 ns at room temperature, with increasing the wavelength emission λEm. The interaction of NBD with piperidine was surveyed at the B3LYP/6–31 g+ (d,p) level of DFT, in acetonitrile. From the optimized geometry, the reduced density gradient (RDG), the quantum theory atom in molecule (QTAIM) and the electron localized function (ELF) analyses have been calculated and discussed. To quantify the intramolecular interactions within the investigated compound, Hirshfeld surface analysis was carried out. The NLO characteristics of the NBD-Pip molecule have also been examined. It has been showed that first and second hyperpolarizability (β and γ) are associated with the ICT.