New aroyl heterocyclic (E)-N′-((2-hydroxynaphthalen-1-yl)methylene)-4-oxopiperidine-1-carbohydrazide and its metal complexes: synthesis, spectroscopic, thermal, DFT, molecular docking and antimicrobial studies

In order to resist the growth of human pathogenic microorganisms, a new N-heterocyclic ligand of ( E )- N ′-((2-hydroxynaphthalen-1-yl)methylene)-4-oxopiperidine-1-carbohydrazide was synthesised from the condensation reaction of 4-oxopiperidine-1-carbohydrazide and 2-hydroxynaphthalene-1-carbaldehyde in ethanol. Reaction of metal salt of (M(II/III)·Cl 2 )·nH 2 O M = Cr(III), Fe(III), Mn(II), Co(II), Ni(II) and Cu(II) with ligand resulted in the formation the two types of complexes [M(III)C 17 H 19 N 3 O 5 Cl] and [M(II)C 17 H 20 N 3 O 5 Cl] which adopted octahedral geometry. The ligand was thoroughly characterized by elemental analysis, FT-IR, UV–Vis, NMR ( 1 H, 13 C) and HR-mass spectroscopy while the structure of metal complexes was confirmed on the basis of elemental analysis, UV–Vis spectra, molar conductivity, magnetic susceptibility, and TGA-DTA analysis. The ligand behaves as dibasic tridentate, linkages via phenolic-O, azomethine-N, enolic-O atoms in metal (III) complexes and as monobasic tridentate in metal (II) complexes. The decomposition pattern were ascertained by TG analysis, and kinetics accountability from Coats–Redfern relation. The compounds were excited at λ ex = 380 nm and observed intense emission intensity at λ em = λ 527–533 nm. SEM analysis was performed to observe their surface analysis. The molecular geometry optimization and quantum chemical properties have been retrieved from DFT. ADMET score have been predicted as a drug-likeness prospect from admetSAR. The molecular docking outcomes revealed the good binding score of ligand with Adenylate kinase, Peptide deformylase (bacterial enzymes) and DNA polymerase (fungal enzyme). The in vitro antimicrobial potency of ligand and its metal complexes were carried against the bacterial species ( Escherichia coli , Salmonella typhi , Staphylococcus aureus, Bacillus substilis ), and fungal species ( Candida albicans , Aspergillus niger ) and showed their promising activity. Graphical abstract