Manganese(III) complexes of N2O2 donor 5-bromosalicylideneimine ligands: Combined effects of electron withdrawing substituents and chelate ring size variations on electrochemical properties |
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Authors: | Kamala Mitra C Robert Lucas |
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Institution: | a Department of Chemistry, Bengal Engineering and Science University, Shibpur, Botanic Garden, Howrah, West Bengal 711 103, India b Murshidabad College of Engineering and Technology, Cossimbazar, Murshidabad 742 102, India c Department of Chemistry, Memorial University of Newfoundland, St. John’s, Nfld, Canada A1B 3X7 |
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Abstract: | A series of mononuclear manganese(III) complexes of formulae Mn(L)(X)(H2O)] (1-13) and Mn(L)(X)] (14-17) (X = ClO4, F, Cl, Br, I, NCS, N3), derived from the Schiff bases of 5-bromosalicylaldehyde and different types of diamine (1,2-diaminoethane, 1,2-diaminopropane, 1,3-diaminopropane and 1,4-diaminobutane), have been synthesized and characterized by the combination of IR, UV-Vis spectroscopies, cyclic voltammetry and by X-ray crystallography. The redox properties of all the manganese(III) complexes show grossly identical features consisting of a reversible or quasireversible MnIII/MnII reduction. Besides MnIII/MnII reduction, the complexes 4, 5, 10, 13 and 16 also show reversible or quasireversible MnIII/MnIV oxidation. A linear correlation has been found for the complexes 5, 7, 11 and 13 Mn(L2)(X)(H2O)] (X = F, Cl, Br, I) when E1/2 MnIII/MnII] is plotted against Mulliken electronegativities (χM). The effect of the flexibility of the ligand on redox potential has been studied. It has been observed that the manganese(II) state is stabilized with increasing flexibility of the ligand environment. The crystal structure of 6 shows an octahedral geometry. |
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Keywords: | Manganese(III) complexes Phenolate Schiff bases N2O2 donors Electronic spectra X-ray structure Electrochemistry |
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