Naphthalene-1,2-dione and indoline-2,3-dione as Convenient Ligands to Prepare Mixed Ligand Complexes of Mn, Cu And Cd: Synthesis, Spectroscopic Characterization, DFT Studyand Antibacterial Activity

Mixed ligand (L1L2) (where L-1=naphthalene-1,2-dione and L-2=indoline-2,3-dione) and its Mn(II), Cu(II) and Cd(II) complexes (3 a, 3 b, and 3 c, respectively) were prepared and described using analytical analysis, FT-IR, UV-Vis, magnetic measurements, XRD-diffraction and molar conductivity. Moreover, the structural properties of the mixed ligand complexes were investigated using mass spectrometry and elemental analysis. These complexes are expected to have octahedral molecular geometry depending on the electronic spectra and magnetic susceptibility tests. The two mixed ligands (L1L2) are bivalent ligands with two oxygen atoms. As an example, the quantum chemical properties, bond lengths, and bond angles were discussed for the Cu(II) complex. The Gaussian09 program was used to optimize the structural formula for the investigated ligand. The energy gaps and other essential theoretical properties were calculated using the DFT/B3LYP approach. The prepared mixed ligand complexes 3 a, 3 b, and 3 c were evaluated for their antibacterial properties. These complexes were tested against both Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) using the agar diffusion method. The organic ligands were observed to be less biologically active than the targeted complexes as antimicrobial agents. According to molecular docking, the title compounds have a positive interaction with the crystal structures of Escherichia coli (3HUM), Staphylococcus aureus (5 M18), Bacillus subtilis (5ZW4), and Pseudomonas aeruginosa (4WEL).