Synthesis, structural characterization, catalase-like function and epoxidation activity of a mononuclear manganese(II) complex

Abstract

In this work we have prepared a manganese(II) complex using the tridentate ligand N, N-bis(2-pyridylmethyl)amine (bpma). The manganese complex was characterized by elemental analysis, conductivity measurements and infrared, electronic (UV–vis) and EPR spectroscopic techniques. The analysis of the complex obtained has shown that the formula is [Mn(bpma) 2](ClO 4) 2 ( 1), which was confirmed by the X-ray structure. The structure shows two different conformers with pseudo-octahedral geometry. The synthesized manganese complex displays efficiency in disproportion reactions of hydrogen peroxide producing water and dioxygen in catalase-like activity. Compound 1 has shown a high reactivity with initial velocity for generation of dioxygen of 1.34 × 10 −5 mol s −1 in the absence of heterocyclic base, and 4.46 × 10 −5 mol s −1 in basic medium. Oxidation of cyclohexene by oxygen donor iodosylbenzene (PhIO), using the complex in homogeneous and heterogeneous media as catalyst, has also been investigated. In homogeneous catalysis it was observed that the major product was the epoxide. However, in heterogeneous media the reaction becomes more selective towards alcohol formation. Oxidation reactions using H 2O 2 as oxidant have shown low yields probably due the hydrogen peroxide decomposition promoted by complex 1.