| Summary: | The assignments structures of the four 1:1 pipemidic acid (pipH)–magnesium(II), calcium(II), zinc(II), and iron(III) complexes, [Mg(pip)(H<sub>2</sub>O)<sub>3</sub>(Cl)].6H<sub>2</sub>O, [Ca(pip)(H<sub>2</sub>O)<sub>3</sub>(Cl)].2H<sub>2</sub>O, [Zn(pip)(H<sub>2</sub>O)<sub>3</sub>(Cl)].4H<sub>2</sub>O, and [Fe(pip)(H<sub>2</sub>O)<sub>2</sub>(Cl)<sub>2</sub>].6H<sub>2</sub>O, (where pip = deprotonated pipemidic), were synthesized through the chemical reactions of MgCl<sub>2</sub>.6H<sub>2</sub>O, CaCl<sub>2</sub>.2H<sub>2</sub>O, ZnCl<sub>2</sub>, and FeCl<sub>3</sub>.6H<sub>2</sub>O metal salt chlorides with pipH chemotherapeutic agent ligand in a methanolic solvent. The microanalytical analysis CHN, conductance, (infrared (FTIR) and electronic (UV–Vis.)) spectra, and thermogravimetric measurements (TG) have been utilized to discuss the solid isolated complexes. The X-ray powder diffraction (XRD) analysis and the transmission electron microscopy (TEM) confirm the nanostructured form of the synthesized pip complexes. The deprotonated pipH ligand is coordinated to Mg(II), Ca(II), Zn(II), and Fe(III) metal ions through the two oxygen atoms of the carbonyl (quinolone group) and carboxylic group. The thermodynamic parameters (energy, E*), (entropy, ΔS*), (enthalpy, ΔH*), and (Gibbs free energy, ΔG*) of activation have been estimated based on thermogravimetric curves using “Coats–Redfern and Horowitz–Metzeger non–isothermal” methods.
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