Synthesis of a New Hydrazone-based Schiff Base: Spectroscopy, Single Crystal, DNA Binding and Theoretical Studies

A new thiosemicarbazide-based Schiff base (TSDHB) was synthesized from thiosemicarbazide and 2,3-dihydroxybenzaldehyde. The prepared thiosemicarbazone was characterized by elemental (CHN), FT-IR, 1H and 13C NMR techniques. Furthermore, the molecular structure was probed using the single-crystal X-ray diffraction (SC-XRD) technique, which confirmed the enol tautomeric form with two independent molecules in asymmetric unit. The dissimilarity between the molecular units was determined by molecular overlay plots. The various intermolecular interactions and solid-state assembly stabilization were explored by Hirshfeld surface analysis. Void analysis was executed to examine the mechanical stability of crystalline units. The bioactivity of thiosemicarbazone was probed with the help of its binding capacity with salmon sperm DNA (SS-DNA) by means of the absorption interaction method. Accompanied by biological activity, optoelectronic properties such as nonlinear optical properties of yielded crystal were also explored through the DFT approach at M06/6-311G (d,p). For this, various kinds of investigations such as frontier molecular orbital (FMO), UV-Vis, global reactivity parameters (GRPs), transition density matrix (TDM), density of states (DOS), natural population analysis (NPA), and natural bond orbital analysis (NBO) were executed at M06 functional. A good agreement was examined between XRD and DFT findings of molecular geometric parameters. Notably, in comparison with urea, TSDHB demonstrated enhanced nonlinear optical properties (linear polarizability=4.766 × 10−23 esu and third-order hyperpolarizability=5.939 × 10−35 esu). These findings position TSDHB as a promising candidate for DNA binding as well as for photonic materials due to its unique molecular characteristics and enhanced nonlinear optical behavior.