Redox-active dihydrazone and its manganese(IV) complexes: Synthesis, characterization, electrochemical and antimicrobial studies
Mahanta, P; Sarma, P; Basumatary, D; Medhi, C
The +4 oxidation state of manganese has sparsely been documented so far. Few studies have reported deriving the high valent state of metals from dihydrazones. In this study, the synthesis and structure elucidation coupled with the study of electron transfer and biological properties of the polyfunctional ligand, bis(2-hydroxy-1-naphthaldehyde)fumaryldihydrazone (napfhH4) and its manganese(IV) complexes ([MnIV(napfh)](A)2].2H2O and [MnIV(napfh)(NN)], where A= H2O, (1); pyridine, (py, 2); 2-picoline, (2-pic, 3); 3-picoline, (3-pic, 4); 4-picoline, (4-pic, 5) and NN = 2, 2’-bipyridine, (bpy, 6) and 1, 10-phenanthroline, (phen, 7)) were undertaken. IR spectral studies revealed that napfhH4 coordinates to manganese center in a tetradentate manner arranged in anti-cis configurations in these complexes and in keto-enol form in the complexes (1), (2), (6) and (7) while in complexes (3)-(5), it exists in keto form. The magnetic moment, electronic and electron paramagnetic resonance spectral studies corresponded to Mn(IV) center within six-coordinate octahedral geometry around the manganese center. Molar conductances in DMSO indicated their non-electrolytic nature. The redox activity of the ligand and one electron transfer of Mn(IV)/Mn(III) in complexes were evaluated. Further, the increased antimicrobial efficacies against different pathogenic gram-positive and gram-negative bacteria suggest these complexes as good candidates for other biological studies such as antitumour activity. © 2021 World Research Association. All rights reserved.