Reinvigorate the synthesis, spectroscopic findings, SEM morphology investigation, and antimicrobial silhouette of contemporary Salen ligands: A comprehensive DFT landscape

Abstract

This article has serendipitously synthesized three trendy Salen ligands (H2L1/H2L2/H2L3) prepared from Salicylaldehyde/ortho-vanillin and the corresponding diamines backbone. The synthesized compounds were characterized vividly by different spectroscopic techniques. Further, the SEM examined the morphology of the ligands. B3LYP, HF, and M062X methods with 6–31++g (d, p) basis sets optimized the molecular geometry. The divergent DFT-based analysis considered the chemical and biological activities of the studied molecules. The global chemical reactivity parameters, HOMO-LUMO energy gap, and ESP ensure the same. However, it is seen that the activity of the H2L3 molecule is higher than the other molecules to the ΔE energy gap value. The cardinal information about the NLO properties of the molecules has been studied where the nonlinear hyperpolarizability (β) of the three studied molecules was fortunately compared. The numerical values of H2L1 and H2L2 were very close, but the value of H2L3 was 1.5 times. Beyond the bounds, the first two molecules had lower dipole moments than H2L3. Theoretical IR/NMR calculations explore important assignments. Molecular docking (MD) examines the activities of molecules against biological materials that are breast cancer protein (PDB ID: 1A52), liver cancer protein (PDB ID: 2JW2), and prostate cancer protein (PDB ID: 3A99). The theoretical drug properties have been investigated in-depth so they can be used as drugs by ADME/T analysis. The prepared compounds were screened in vitro against two grams + ve and two-gram −ve bacterial strains using the agar well diffusion method. MIC determines the good antibacterial activity of the compounds. The MIC values ​​for H2L1 range from 15.62 to 125 g/mL, while for H2L2, 31.25–500 g/mL, and for H2L3, 31.25–500 g/mL. Based on the MIC values, the tested compounds' potency order was H2L1 > H2L3 > H2L2. Eventually, the time-kill kinetics study led to promising bactericidal activities.