Inspecting the Antimicrobial, Bio‐Catalytic, DNA Interactions, In Vitro Cytotoxicity, and Cell Cycle Analysis Efficiency of Newly Nano‐Sized Co (II), Ni (II), Cu (II), and Zn (II) Complexes of Schiff's Base Ligand: Spectroscopic Characterization and

ABSTRACT Nano‐sized bivalent metal complexes of Cu (II) (C1) , Ni (II) (C2) , Co (II) (C3) , and Zn (II) (C4) were prepared and characterized of the form [M(L) 2 ] where L = 2‐((E)‐((4‐methyl‐2‐(((E)‐thiophen‐2‐ylmethylene)amino)phenyl)imino)methyl)benzenethiol] (C 19 H 16 N 2 S 2 ), M = Cu (II), Ni (II), Co (II), and Zn (II). Elemental analyses, molecular weight calculations, infrared, 1 H, 13 C, and 15 N NMR, electronic, mass, magnetic susceptibility, and conductivity assessments were employed to evaluate our bivalent metal complexes. DFT studies were used to study the tautomeric equilibrium of the ligand (HL), via the DFT\B3LYP technique in connection with a 6–311G* correlation consistent basis set. The metal formed four coordinated with the tridentate N 2 S donor Schiff base to form octahedral geometry complexes. The XRD analysis of the divalent metal complexes revealed sharp, intense diffraction peaks, indicating their crystalline nature with nanoscale particle sizes. Additional evidence was provided by EDX, SEM, and AFM images, which also confirmed the uniform distribution across the complex surface. Analysis of the absorption patterns for the nano‐sized complexes interaction with CT‐DNA signifies that the complexes bind via intercalation, with intrinsic binding constant ( K b ) spanning from 4.25 × 10 5 to 8.34 × 10 3 M −1 . Nano‐sized metal (II) complexes show a higher viscous nature than HL. The cytotoxicity of H‐L ligand and its complexes against HCT‐116, and M‐NFS‐60 cells was assessed by the MTT assay. Complex C3 shows greater cytotoxic effects compared to Cisplatin on MCF‐7 cells. Our flow cytometry data indicate significant levels of apoptosis and cell cycle arresting in both liver and breast cancer cell lines.