Complexos dinucleares de Cu(II) multifuncionais: síntese, estruturas cristalinas, propriedades magnéticas e catalíticas

Abstract

In this work, it has been described the synthesis and characterization of the novel and flexible proligand, N,N-2,2-ethylenediphenylenebis(oxamate) (Et2H2L). This proligand has been used in the synthesis of two novel dinuclear CuII coordination compounds: [Cu2(H2Lanti)2(EtOH)2]2EtOH (1) and [Bu4N]4[Cu2(Lsin)2] (2), being both unpublished and having their crystal structures elucidated by X-ray diffraction. The analysis of their magnetic properties showed that compound 1 presents a weak ferromagnetic coupling between the CuII ions (J = +2,93 cm-1), while in 2 the CuII ions are practically isolated due to the structural conformation (J ~ 0 cm-1). Studies performed in solution showed that a reversible interconversion between the structures 1 and 2 takes place by changing the pH of the medium, where 1 is obtained in acid media while 2 in basic media. ESI()-MS spectra suggest the existence of the compounds in the dinuclear form in solution, as well as the cyclic voltammetry studies, indicating that complex 1 probably keeps its dinuclear form, and can suffer oxi-redox according to the CuII-CuIII pair. Furthermore, compound 1 presented surfactant properties in the formation of water-oil emulsion, being also a hydrogen peroxide activator for Copper Fenton reactions. These properties were studied in oxidation tests of a molecule type (quinoline) in organic phase. Two cocrystals of complex 2 with ethylenedianiline (EDA) were also obtained, resulting in different supramolecular polymers arrays: [Bu4N]4[Cu2(Lsin)2]4H2O2(Me2CO)EDA (3) (linear) and [Bu4N]4[Cu2(Lsin)2]5H2O1,5EDA (4) (zig-zag). In these two structures, hydrogen bond networks are responsible for the supramolecular arrays evidenced in the crystal structures.