Synthesis, spectroscopy and biological investigations of manganese(III) Schiff base complexes derived from heterocyclic β-diketone with various primary amine and 2,2′-bipyridyl

The mixed ligand mononuclear complex [Mn(bipy)(HPMFP)(OAc)]ClO4 was synthesized by reaction of Mn(OAc)3·2H2O with HPMFP and 2,2′-bipyridyl. The corresponding Schiff base complexes were prepared by condensation of [Mn(bipy)(HPMFP)(OAc)]ClO4 with ethylenediamine, ethanolamine and glycine (where HPMFP = 1-phenyl-3methyl-4-formyl-2-pyrazolin-5one, bipy = 2,2′-bipyridyl). All the compounds have been characterized by elemental analysis, magnetic susceptibility, conductometry measurements and 1H and 13C NMR, FT-IR, mass spectrometry. Electronic spectral and magnetic susceptibility measurements indicate square pyramidal geometry around manganese(III) ion. The thermal stabilities, activation energy E*, entropy change ΔS*, enthalpy change ΔH* and heat capacity of thermal degradation for these complexes were determined by TGA and DSC. The in vitro antibacterial and antifungal activity of four coordination compounds and ligand HPMFP were investigated. In vitro activates of Bacillus subtillis (MTCC-619), Staphylococcus aureus (MTCC-96), Escherichia coli (MTCC-722) and Klebsiella pneumonia (MTCC-109) bacteria and the fungus Candida albicans (ATCC-90028) were determined. All the compounds showed good antimicrobial activity. The antimicrobial activities increased as formation of Schiff base.

Graphical abstractAll the compounds have been characterized by elemental analysis, magnetic susceptibility, conductometry measurements and 1H and 13C NMR, FT-IR, mass spectrometry. The in vitro antibacterial and antifungal activity of four coordination compounds and ligand HPMFP were investigated. All the compounds showed good antimicrobial activity. The antimicrobial activities increased as formation of Schiff base.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis of novel Schiff base complexes of manganese(III) ► The Schiff base complexes having square pyramidal geometry with N, O as donor site from β-diketone, N,N contributed from the neutral ligand 2,2′-bipyridyl and monodentate nature of anion OAc. ► Electronic spectra, magnetic moment and conductance study evidence the fact of square pyramidal geometry of complexes. ► Schiff base complexes enhance the activity against the bacteria and fungi due to Schiff base complexes bear polar and nonpolar properties together; this makes them suitable for permeation to the cells and tissues.