Manganese(III) Complexes with Decolourization Ability

Abstract

Some novel mixed ligand complexes of Mn(III) with glycine ligand, namely [Mn(gly)₂Cl(en)],  [Mn(gly)₂Br(en)], [Mn(gly)₂N₃(en)] and [Mn(gly)₂NCS(en)] have been synthesized, from starting from Mn(gly)₂Cl, Mn(gly)₂Br, Mn(gly)₂N₃ and Mn(gly)₂NCS respectively. These complexes have been characterized by UV/Visible, FT-IR and Mass spectrometry. The spectroscopic data suggest distorted octahedral geometry for all these novel complexes. The \(\lambda\)max values for these complexes (⁵T₂g \(\longrightarrow\)⁵Eg transitions) are 482 nm [Mn(gly)₂N₃(en)], 488 nm [Mn(gly)₂NCS(en)], 486 nm [Mn(gly)₂Br(en)] and 484 nm [Mn(gly)₂Cl(en)], all these transitions show red shift in comparison to the parent complex. The ligand field parameters such as 10 Dq, B and \(\beta\)

have also been calculated and suggest a covalent metal ligand bonding. One peculiar finding in the FT-IR spectra of these complexes is that it shows stretching frequencies for both the free and coordinated NH₂ group in all complexes indicating ethylenediamine ligand non bridging. The mass spectrometry results show molecular ion peaks at m/z  300, 345, 307 and 323 for [Mn(gly)₂Cl(en)],  [Mn(gly)₂Br(en)], [Mn(gly)₂N₃(en)] and [Mn(gly)₂NCS(en)] respectively. The coordination of ethylenediamine to Mn(III) enhances its efficiency towards decolourization of methyl red dye. The main objective of this study is to explore the catalytic properties of these complexes.