Facile synthesis, structural elucidation, non-linear optical properties and biological evaluation of some novel tetra-dentate azomethine complexes supported by DFT calculation and molecular docking approach

• Synthesis of new tetra-dentate metal complexes and their structural elucidation. • Geometry optimization for structural verification as well as non-linear optical properties. • Intensive biological applications against microbes, free radicals and carcinoma cell lines. • Molecular docking studies for the investigated compounds. The synthesis and structural analysis of complexes derived from (2-Ethoxy-6-({2-[(3-ethoxy-2-hydroxy-benzylidene)-amino]-5-nitro-phenylimino})-phenol (ESNP ligand) were checked using various physicochemical, spectroscopic and analytical techniques. These techniques included decomposition point determination, elemental analysis (CHN), spectroscopic (IR, NMR, mass spectrometry), magnetic susceptibility, conductivity, as well UV–Vis spectrum analysis, along with theoretical studies. Molar conductance values indicated that the Fe(III), Zn(II), Cu(II), and Ru(III) complexes are non-electrolytes in fresh DMSO solutions, with conductance values ranging from 10.45 to 15.14 Ω -1 cm 2 mol -1 except ESNPRu complex is mono electrolyte. IR spectra suggested which the ligand coordinates through the metal ions in a tetra-dentate fashion, utilizing the (N & O) donor sites from the (C=N & C-O) groups in the ligand moiety. Analytical data from solution complexation, job`s method suggested a 1:1 (metal: ligand) molar ratio. The stability order of the complexes was determined as ESNPFe > ESNPRu > ESNPCu >ESNPZn, consistent with the stability constant (Kf) values. The pH profile indicated that the studied complexes exhibit stability upon a wide pH scale, typically between (pH= 4:10). Magnetic and electronic spectral analyses helped deduce the ligand coordination abilities and the geometric structures of the complexes. The electronic structures of the investigated ligand and its complexes are analyzed using quantum chemical calculations via the DFT approach. The [B3LYP] level, [B3LYP/6/311G**] degree of the unbound ligand, In the density function theory (DFT) computations, the complexes' and [B3LYP/6/311G**/LANL2DZ] functional categories were employed. The findings demonstrated that the DFT calculations are consistent with the experimental ones. Natural bond orbital (NBO) analysis investigated hyper conjugative interactions, molecular stability, bond strength, and intramolecular charge transfer. The resulting nonlinear optical properties were examined by calculating the hyperpolarizability (β) and molecular polarizability (α) parameters, which gave rise to several unexpected optical properties for the synthesized compounds. Using the agar well diffusion method, the anti-pathogenic activity of the produced materials was experimentally confirmed against a subset of gram (+) and gram (-) bacteria and some fungi. Moreover, the cytotoxic activity of ESNP ligand and its metal chelates were examined against Hepatic Cellular Carcinoma, Breast Carcinoma, and Colon Carcinoma cells. Additionally, the activity of the inspected compounds to inhibit DPPH radical was checked. Furthermore, docking of molecule simulations were completed to determine how the obtained compounds bonded to the targeted binding sites of protein.