Synthesis, Characterization, and Multifaceted Biological Applications of Novel Binuclear Mn(II), Fe(III), and Co(II) Malonohydrazone Schiff-Base Complexes.

Novel Mn-(II), Fe-(III) and Co-(II) binuclear complexes of 2-benzyl-N'3-((2-hydroxynaphthalen-1-yl)-methylene)-N'1-((E)-(2-hydroxynaphthalen-yl)-methylene)-malonohydrazide (H4L2) were synthesized. Full structural characterization of the studied compounds was accomplished through an integrated approach employing FT-IR spectroscopy, NMR, EI-MS, PXRD, UV-vis spectroscopy, magnetic susceptibility, and thermogravimetric analysis. Geometry optimization was performed by employing the DMol3 module within the framework of density functional theory. The spectroscopic analysis discovered the H4L2 functions as a dianionic hexadentate Schiff base (O4N2) coordinating each Mn-(II) center through the oxygen of carbonyl groups, (CN)az nitrogen atoms, and the deprotonated naphthalic (OH) oxygen atoms in the [Mn2(H2L2)-Cl2]·H2O complex. In the infrared spectra of the [Co2(L2)-(H2O)2]·2H2O and [Fe2(L2)-(H2O)4Cl2]·2H2O complexes, the ligand behaves as a tetra-anionic hexadentate (O4N2), bonding the metal center through the enolized carbonyl group, the naphthalic OH, and the azomethine nitrogen atoms, as depicted in the proposed coordination structure. The cytotoxicity screening data reveal that the investigated compounds demonstrate selective anticancer activity, with distinct growth inhibitory effects against specific human cancer cell lines, including WI-38, HePG-2, HeLa, HEP-2, PC-3, MCF-7, and HCT-116. The [Mn2(H2L2)-Cl2]·H2O and [Co2(L2)-(H2O)2]·2H2O complexes displayed strong degradation, indicative of potent DNA interaction and cleavage capability. The electrophoretic profile demonstrates a complete protein degradation effect for the [Mn2(H2L2)-Cl2]·H2O complex. In particular, the [Co2(L2)-(H2O)2]·2H2O complex displayed the highest antioxidant potency with an IC50 of 0.0231 μM. The antimicrobial results demonstrated that the [Mn2(H2L2)-Cl2]·H2O complex exhibited the most potent activity against Escherichia coli, Klebsiella pneumonia, Staphylococcus aureus, Bacillus subtilis, Candida albicans, and Aspergillus flavus with inhibition zones of 17, 14, 11, 12, 9, and 10 nm, respectively. Molecular docking simulations against HePG-2 (PDB ID: 5EQG) and MCF-7 receptors (PDB ID: 6NM0) indicated favorable binding affinities for the investigated compounds.