New mononuclear Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) complexes incorporating 4-{[(2 hydroxyphenyl)imino]methyl}phenyl-4-methylbenzenesulfonate (HL): Synthesis, characterization, theoretical, anti-inflammatory, and molecular docking investigation

Herein, new Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) complexes incorporating 4-{[(2-hydroxyphenyl)imino]methyl}phenyl 4-methylbenzenesulfonate Schiff-base ligand (HL) were designed, synthesized, and characterized. The structure of the new compounds was elucidated based on spectroscopic techniques (nuclear magnetic resonance [NMR], ultraviolet-visible [UV-vis], infrared [IR], mass), magnetic, conductivity, thermal analysis (thermogravimetric analysis [TGA], differential thermal analysis [DTA]) measurements, in addition to complex stoichiometry determination using molar ratio and Job's methods. The new complexes showed an interesting structural variation: square-planar (in the case of NiL), tetrahedral (in the case of CuL), and octahedral (in the case of FeL2, CoL2, and ZnL2). Furthermore, density functional theory (DFT) calculations were performed to obtain deep insights into the structural features, orbital interactions, and electronic chemical descriptors evaluation. Moreover, the anti-inflammatory behavior of the titled compounds was in vitro investigated. Interestingly, the ZnL2 complex showed the highest activity, whereas the CuL complex showed the lowest activity compared with the other compounds. In order to ascertain the bioactivity of the present compounds, their efficacy was compared with previously reported compounds showing high activity. The anti-inflammatory activity was supported by molecular docking analysis against cyclooxygenase-2 (COX-2) enzyme (PDB ID: 5IKT), which confirms the bioactivity behavior. The obtained results indicated that the titled compounds could be promising anti-inflammatory candidates.