Manganese(II) complexes of biological relevance: Synthesis and spectroscopic characterization of novel manganese(II) complexes with monobasic bidentate ligands derived from halo-substituted 1H-indole-2,3-diones

Abstract

Novel biologically significant manganese(II) complexes with four monobasic bidentate ligands L¹H [2-(5-fluoro-2-dihydro-2-oxo-1H-indol-3-ylidene)hydrazinecarboxamide], L²H [2-(5-fluoro-2-dihydro-2-oxo-1H-indol-3-ylidene)hydrazinecarbothioamide], L³H [2-(5-bromo-2-dihydro-2-oxo-1H-indol-3-ylidene)hydrazinecarboxamide] and L⁴H [2-(5-bromo-2-dihydro-2-oxo-1H-indol-3-ylidene)hydrazinecarbothioamide] were synthesized by complexation of the ligands with MnCl₂·4H₂O in 1: 1 and 1: 2 molar ratios in methanol. The Schiff base ligands and complexes were characterized by elemental analyses, melting points, molecular weights, IR, ¹H and ¹³C NMR, UV–Vis, EPR, and mass spectra, as well as X-ray powder diffraction patterns. Based on the spectral data, a tetrahedral geometry was proposed for all the synthesized metal complexes. The ligands and complexes were tested in vitro against bacteria (Escherichia coli and Staphylococcus aureus) and fungi (Fusarium semitectum and Aspergillus flavus) to show that they were active against all the microbial strains examined, and the metal complexes were more active in comparison with the ligands. DNA cleavage activity of the complexes was examined by gel electrophoresis.