Ferrocene-based Schiff bases copper (II) complexes: Synthesis, characterization, biological and electrochemical analysis

[Display omitted] •Synthesis of ferrocene based Schiff base copper (II) complexes in good yields.•Single crystal X-ray analysis of Schiff bases revealed intramolecular & intermolecular hydrogen bonding.•Biological studies explored that copper (II) complexes were more bioactive than free ligands.•Voltammetry showed reversible one ET diffusion controlled process for all the compounds.•The strong compound-DNA affinity was ascribed to electrostatic mode of interaction. Three ferrocene based Schiff bases copper (II) complexes i.e. bis(N-(2-hydroxybenzylidene)-4-ferrocenylaniline)copper(II)(Cu(L1)2), bis(N-(2,3-dihydroxybenzylidene)-4-ferrocenylaniline)copper(II)(Cu(L2)2), and bis(N-(5-chloro-2-hydroxybenzylidene)-4-ferrocenylaniline)copper(II)(Cu(L3)2), were prepared from Schiff bases N-(2-hydroxybenzylidene)-4-ferrocenylaniline(HL1), N-(2,3-dihydroxybenzylidene)-4-ferrocenylaniline (HL2) and N-(5-chloro-2-hydroxybenzylidene)-4-ferrocenylaniline (HL3). Schiff bases and their corresponding copper complexes were characterized by various spectroscopic, analytical and electro-analytical techniques. Single crystal X-ray diffraction analysis of Schiff base (HL2) revealed three molecules in the asymmetric unit having same molecular conformation. The molecules are connected by intermolecular OH…O as well as intramolecular NH…O hydrogen bonds. All the synthesized compounds were evaluated for their anti-bacterial, cytotoxicity, antitumor, DPPH, DNA protection and DNA-drug interaction studies. The copper complexes exhibited antibacterial activity against all tested strains. All the compounds showed significant activity in brine shrimps cytotoxicity and antitumor assays with IC50 values ranging from 2.32–69.61µg/ml. The copper complexes were found to be more active than Schiff bases with lower IC50 values. The DNA-drug interaction study through voltammetry revealed their binding nature which complemented antitumor behaviour evaluated from biological studies. Moreover, Schiff bases showed prominent antioxidant activity in DPPH assay along with DNA protection activity against hydroxyl free radicals.