Spectral investigation, TD-DFT study, Hirshfeld surface analysis, NCI-RDG, HOMO-LUMO, chemical reactivity and NLO properties of 1-(4-fluorobenzyl)-5-bromolindolin-2,3‑dione

Abstract

In a previous study, the 1-(4-fluorobenzyl)-5-bromolindolin-2,3‑dione (FBID) molecule was synthesized by adding isatin and K2CO3 to acetonitrile, followed by the addition of 4-fluorobenzyl chloride. The resulting mixture was filtered, concentrated, then solidified with n-hexane, and recrystallized in water. In the present study, a combination of theoretical and experimental methods is employed to evaluate and understand the structural and vibrational properties of FBID: FT-IR, UV–Vis as well as 1H and 13C NMR chemical shifts using GIAO approach. All calculations were performed applying the DFT method, with B3LYP functional and 6–311G(d,p) basis set. The HOMO-LUMO energy gap revealed a good charge transfer interaction in FBID molecule. Also, the HOMO and LUMO energies have been exploited to describe the global chemical reactivity. At the same method and level, it has been demonstrated that the studied compound has NLO properties. The estimated NBO, atomic charges and the molecular electrostatic potential map indicated that the sites around the oxygen atoms of the FBID molecule are the most reactive. The contribution of intermolecular interactions was analysed via Hirshfeld surface analysis. In order to identify the different types of all possible interactions in our system, the reduced density gradient (RDG) method was used to characterize and evaluate the nature of these interactions as strong repulsion (steric effect), strong attraction (hydrogen bond), or weak interaction (Van der Waals).