A series of new mixed ligand metal complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) have been synthesized by the reaction of norfloxacin (NOR) with 3‐(bromoacetyl)coumarin (BAC) in 1:1:1 (Mn+:NOR:BAC) molar ratio, which characterized by elemental analysis, spectroscopic measurements (FT‐IR, UV–Vis) molar conductance, effective magnetic moments, and thermogravimetric analysis (TG) and (DTG). All the complexes soluble in DMSO and the conductivity measurement indicate that the complexes are electrolyte with ratio 1:1 for Mn(II), Fe(II), and Zn(II) and 1:2 for Co(II), Ni(II), and Cu(II). Electronic and magnetic data elucidated the octahedral structure for all complexes. Assorted thermodynamic factors are calculated, and the results are explicated. Molecular modeling calculations (bond angles, dihedral angles, total energy, heat of formation, and dipole moment) confirm the structural geometry of the complexes and indicate the very good agreement between the computed and experimental geometrical parameters. The calculated data for the hardness (η) and absolute softness (σ) showed that all complexes are soft with respect to ligands. The two ligands and their metal complexes have also been screened for their antibacterial and antifungal activity against some selected species; the data showed that the complexes have remarkable potency as compared with the parent ligands.

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The synthesis and characterization of Mn (II), Fe (II), Co (II), Ni (II), Cu (II) and Zn (II) complexes with 3-(bromoacetyl)coumarin (BAC) in presence of 1,10-phenanthroline (Phen) were reported and described by elemental analysis, molar conductivity, FT-IR, UV-Vis and effective magnetic moments. TG and DTG have been applied to study the decomposition mechanisms for BAC, Phen and their complexes. The analytical results and spectral studies showed that BAC and Phen act as bidentate ligands via oxygen of α, β-unsaturated ketone and oxygen of lactone carbonyl of coumarin and two pyridyl nitrogen atoms of Phen. Octahedral geometries have been proposed for all complexes and the kinetic parameter (E*, ΔH*, ΔS* and ΔG*) were calculated using Coats-Redfern (CR) and Horowitz-Metzeger (HM) methods. DFT calculations (bond lengths, bond angles, total energy, heat of formation, dipole moment and the lowest energy model structures) have been determined. The antibacterial activities for synthesized complexes were assayed against some selected bacterial and the complexes displayed a very highly significant against L. monocytogens.

The interaction of Mn(II) (1), Fe(II) (2), Co(II) (3), Ni(II) (4), Cu(II) (5), and Zn(II) (6) with lomefloxacin (LFX) in the existence of 3‐(bromoacetyl)coumarin (BAC) and NaOH in a 1 : 1 : 1 : 1 molar ratio resulted in the formation of unique mixed ligand metal complexes. The ability of two ligands to chelate metal ions was investigated by elemental analysis, molar conductance, effective magnetic moments FT‐IR, ultraviolet‐visible (UV‐Vis), 1H NMR spectra and thermogravimetric analyses (TG‐DTG). FT‐IR spectra of the complexes suggest that LFX reacted with metal ions as bi‐dentate through pyridone oxygen and carboxylate oxygen. BAC also interacts as bi‐dentate through oxygen of α,β‐unsaturated ketone and oxygen of lactone carbonyl of coumarin. These chelates are electrolytes, according to conductivity experiments, with a 1 : 1 ratio for Mn(II), Fe(II), and Zn(II) and a 1 : 2 ratio for Co(II), Ni(II), and Cu(II). Electronic and magnetic data revealed an octahedral shape for all compounds. The thermodynamic parameters of thermal breakdown processes such as Ea, ΔH*, ΔS* and ΔG* were determined from TG and DTG curves using Coats‐Redfern (CR) and Horowitz‐Metzeger (HM) techniques for LFX, BAC and their metal complexes. The structural geometry of the complexes is confirmed by molecular modeling studies. The findings show that the complexes are soft with regard to ligands, with values ranging from 0.058 eV for Fe(II) complex to 0.090 eV for Zn(II) complex and 11.11 to 17.24 eV for LFX and BAC, respectively, and 0.121, 8.26 eV and 0.111, 9.009 eV for LFX and BAC. The ligands and their complexes were tested in vitro for antibacterial activity against a variety of bacterial and fungal strains, and the results revealed that the complexes had significantly higher potency than the parent drug.