Isophthaloylbis (Azanediyl) Dipeptide Ligand and Its Complexes: Structural Study, Spectroscopic, Molecular Orbital, Molecular Docking, and Biological Activity Properties

The ligand 2,2′-(isophthaloylbis(azanediyl))bis(3-phenylpropanoic acid; H₂L) was used to build novel metal complexes of Co(II), Ni(II), Fe(III), and Zn(II) metal ions. Elemental analyses, thermal, infrared, mass, electronic spectra, magnetic moments, X-ray diffraction analysis, and conductivity measurements were used to predict the nature of bonding and the stereochemistry of the complexes. The complexes were proposed to have the general formula [M(H₂L)(H₂O)₂]Cl<i>_n</i>, where M = Co(II), Ni(II), and Zn(II) (<i>n</i> = 2) and Fe(III) (<i>n</i> = 3), based on the elemental analyses data. All of the complexes were electrolytes, according to the molar conductivity measurements. The FT-IR spectra revealed that the dipeptide ligand is tetradentately coordinated to metal ions, with NNOO donor atoms participating in coordination with metal (II)/(III) ions, resulting in octahedral complexes. Using the recommended programme, the structural formula for the investigated ligand was optimized. Using the density-functional theory (DFT) approach, the energy gaps and other essential theoretical parameters were calculated. The agar diffusion method was used to test the <i>in vitro</i> biological characteristics of the ligand (H₂L) and its transition metal complexes against Gram(+) bacteria (<i>Bacillis subtilis</i> and <i>Staphylococcus aureus</i>) and Gram(−) bacteria (<i>Escherichia coli</i> and <i>Pseudomonas aeruginosa</i>). The title compounds were found to be more biologically active than the parent dipeptide ligand. The title compounds have a good interaction with the crystal structures of 3t88-<i>Escherichia coli</i>, 3ty7-<i>S. aureus</i>, 5h67-<i>Bacillus subtilis</i>, and 5i39-<i>Pseudomonasaeruginosa</i>, according to molecular docking study.