New complexes of manganese (II) and copper (II) derived from the two new furopyran-3, 4-dione ligands: Synthesis, spectral characterization, ESR, DFT studies and evaluation of antimicrobial activity

A total of four new metal complex derivatives of two new ligands 2-(hydroxy(phenyl)-6-methyl-2H-furo [3,2-c]pyran-3,4-dione (L-1) and 2-(hydroxyl (2-hydroxyphenyl) -6-methyl-2H-furo [3,2-c]pyran-3,4-dione (L-2) with the metal ions Mn(II) and Cu(II) have been successfully prepared in alcoholic medium. The complexes obtained are investigated by spectral studies with the use of FT-IR and UV-vis techniques, ESR and magnetic measurements. The IR spectra suggest that the oxygen atoms of the two ligands are engaged in the bond with the central metal. The electronic spectra of the complexes and their magnetic moments provide information about geometries. The molar conductance measurements showed that the complexes are non-electrolytes. Theoretical calculations invoking geometry optimization and molecular orbital description HOMO and LUMO are done using DFT density functional theory. The experimental results and the calculated structural parameters, bond distances and angles, revealed a distorted octahedral geometries around the manganese and copper center through the oxygen of the furan ring for the synthesized complexes ([M(L)(2)(H2O)(2)]nH(2)O; M: metal; L: ligand). The antimicrobial activity of the ligands and their complexes was evaluated in vitro against different bacteria and fungi using agar diffusion method. The ligands and their complexes of manganese (II) and copper (II) exhibited a strong antifungal activity. Copper and manganese complexes have different antibacterial properties against bacteria. The ligand L-1 and there complexes were found to be more active against Gram-positive than Gram-negative bacteria. (C) 2019 Elsevier B.V. All rights reserved.