Synthesis, characterization and catalytic oxyfunctionalization of cyclohexene with tert-butylhydroperoxide over a manganese(II) complex covalently anchored to multi-wall carbon nanotubes (MWNTs)

摘要

The chemical modification of multi-wall carbon nanotubes (MWNTs) is an emerging area in material science. In the present study, an hydroxyl functionalized manganese(II) Schiff-base has been covalently anchored on modified MWNTs. The new modified MWNTs have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron (XPS), thermal analysis, UV-Vis, diffuse reflectance (DRS), FT-IR spectroscopy and elemental analysis. The results suggest that the symmetrical Schiff-base: N,N-bis(4-hydroxysalicylidene)-ethylene-1,2-diamine: H-2[(OH)(2)-salen]; is a bivalent anion with tetradentate N2O2 donors derived from the phenolic oxygens and azomethine nitrogens. The formulae was found to be [Mn((OH)(2)-Salen)] for the 1:1 non-electrolytic complex. The multi-wall carbon nanotubes covalently anchored manganese(II) complex ([Mn((OH)(2)-salen)1@MWNTs) catalyze the oxidation of cyclohexene with TBHP. Oxidation of cyclohexene catalyzed by this complex gave 2-cyclohexene-1-ol, 2-cyclohexene-1-one and 1-(tert-butylperoxy)-2-cyclohexene as the major products. The manganese(II) complex covalently anchored on MWNTs shows significantly higher catalytic activity than [Mn((OH)(2)-salen)]. The activity of the immobilized catalyst remains nearly the same after three cycles, suggesting the true heterogeneous nature of the catalyst. This catalyst is more selective towards 2-cyclohexene-1-one. (C) 2008 Elsevier Ltd. All rights reserved.