Synthesis, crystal feature and spectral characterization of paeonol derived Schiff base ligands and their Cu(II) complexes with antimicrobial activity

Four novel Schiff bases PNL-4OMe, PNL-4Br, PNL-4F, PNL-3,4-F2, and their copper(II) complex with [M(L)2(H2O)2] arrangement was synthesized using Paeonol and various aromatic substituted amines. Characterization has been done through FT-IR, ESI Mass, TG-DTA, DFT, magnetic measurements, elemental analysis, and Thermogravimetric analysis. Paeonol derived new bond formation in Schiff bases and changes in frequencies during complexation have been confirmed through FT-IR spectra. All complexes are thermally stable, paramagnetic, and have non-electrolytic behavior. The antimicrobial activity was also tested against Gram-positive bacteria; S. aureus, B. subtilis, and Gram-negative bacteria; E. coli, P. aeruginosa. Single-crystal X-ray data provide evidence that PNL-3,4-F2 is recrystallizing in a triclinic system with P-1(2) space group and confirms the intramolecular H-bonding and short Vander Waal type interactions. Non-covalent interactions and π … π stacking surface interactions in PNL-3,4-F2 were studied with Hirshfeld analysis. H-atoms have the highest interactions with other atoms of neighbouring molecules compared to all other atoms. DFT calculations were performed on the electronic structure of ligand PNL-3,4-F2 and its copper(II) complex and discussed. Paeonol derived Schiff base Ligands and their Cu(II) complexes with Antimicrobial Activity. [Display omitted] •Paeonol based four novel ligands were synthesized via Schiff base reaction.•Using these ligands and Copper(II) nitrate hexahydrate solution, four novel complexes with [M(L)2(H2O)2] geometry were synthesized and characterized using FT-IR, ESI-Mass, TG-DTA, DFT, magnetic measurements, elemental analysis, and Thermogravimetric analysis.•PNL-3,4F ligand crystallizes in the triclinic system showing intramolecular hydrogen bonding was analyzed using single-crystal X-ray data and Hirshfeld analysis was performed to examine its surface interaction.•The antimicrobial activity of all ligands and complexes was also tested against Gram-positive bacteria; S. aureus, B. subtilis, and Gram-negative bacteria; E. coli, P. aeruginosa.•DFT calculations were performed on the electronic structure of ligand PNL-3,4-F2 and its copper(II) complex and discussed.