Synthesis, characterization and antibacterial evaluation with computational study of new Schiff bases derived from 7-hydroxy-4-methyl coumarin

Abstract

New derivatives of 7-hydroxy-4-methylcoumarin were synthesized via oxidation of methyl group at C4 of parent coumarin nucleus using SeO2 as an oxidizing agent. Then the condensation with different aromatic amines and amino acids under conventional method. The structures of the title Schiff bases were elucidated by spectral analysis: FT-IR,13CNMR, and MS.All the compounds were tested in vitro for their preliminary antibacterial activity against two Gram-positive and two Gram -negative bacteria, using serial dilution method, and determining their minimum inhibitory concentrations for the title compounds. Most of the derivatives showed moderate to high antibacterial activity.Compound 7 showed a good antibacterial activity against Gram- positive Staphylococcus aureus and Micrococcus luteus also very potent antibacterial activity against Gram-negative E.coli. Density functional theory (DFT)calculations for the synthesized coumarins were performed using a molecular structure with optimized geometry. Molecular orbital calculations supported a full description of the orbitals, including spatial characteristics, nodal patterns, and the contributions of individual atoms.Highest occupied molecular orbital-lowest unoccupied molecular orbital energies and structures are demonstrated.