Search

• New Fe complexes based on Schiff-base & N-heterocyclic ring have been assembled. • DFT calculations were performed to estimate the electronic properties. • The complexes showed a promising antibacterial and antifungal activity. • Phenoxazinone synthase mimicking activity was explored. • Structure activity relationship (SAR) for these complexes had been derived. New Fe(III) complexes with mixed ligands based on 1-{(E)-[(4-methylphenyl)imino]methyl}-2-naphthol (HN) as primary ligand and secondary co-ligand of O-hydroxy quinolone (HQ), 2-(1H-benzimidazol-2-yl)phenol (HB) and 2-(4,5-diphenyl-1H-imidazol-2-yl)phenol (HI) had been isolated and characterized. The isolated complexes had 1:1:1 ratio for Fe(III):ligand:co-ligand with one chloride and one water molecule coordinated to the Fe-centre, suggesting octahedral structure around the Fe-center with the formula [Fe(Ligand)(co-ligand)(Cl)(H 2 O)]. Theoretical calculations using density functional theory by B3LYP with LANL2DZ basis set had been done for two possible orientations of the ligand moieties around the Fe-center, to find out the most reliable coordination modes. Calculations include geometry optimization, molecular orbital description, and energy evaluation of trans- and cis-coordination modes of the chloride and water around the Fe-center. In-vitro antibacterial and antifungal properties of the isolated complexes have also been examined against pathogenic bacteria, E. coli (G−), B. cereus (G+), and A. fumigatus fungi, by using broth microdilution and disc diffusion methods. The target compounds exhibited considerable growth inhibition against selected pathogenic microorganisms as antimicrobial candidates with low minimum inhibitory concentration (MIC). The complexes showed biomimetic phenoxazinone synthase-like activity for the aerial coupling oxidation of o-aminophenol (OAP) to phenoxazine-2-one (Phz), in acetonitrile (ACN) solution, with high turnover number (K cat). Structure Activity Relationship (SAR) model was derived, using Multi-Linear Regression analysis, by correlation the practical biological (MIC) data with calculated chemical descriptors. [ABSTRACT FROM AUTHOR]