Anchoring of copper(II) complexes onto the organically modified MCM-41: Preparation, characterization and catalytic epoxidation Original Research Article

[Cu(diamine)(NO3)2] complexes have been anchored by substituting easily replaceable nitrate ligand with the amine groups of the organic-modified MCM-41. The amine group containing organic moiety (3-aminopropyl)triethoxysilane has been first anchored on the surface of MCM-41 via silicon alkoxide route. Then the [Cu(diamine)(NO3)2] [where diamine = N,N′-dimethyl-1,2-ethanediamine (NN′dmen) N,N-dimethyl-1,2-ethanediamine (NNdmen), and N,N-diethyl-1,2-ethanediamine (NNdeten)] complex was allowed to react with the modified MCM-41 for tethering the complexes onto mesoporous silica matrix. Copper complexes containing different substituted diamine ligands viz. N,N′-dimethyl-1,2-ethanediamine, N,N-dimethyl-1,2-ethanediamine, and N,N-diethyl-1,2-ethanediamine have also been prepared to compare the catalytic efficiency. The prepared catalysts have been characterized by infrared (FT–IR) and UV–vis spectroscopic, electron paramagnetic resonance (EPR), small-angle X-ray diffraction and N2 sorption study. The catalytic efficacy in the epoxidation reaction depends on the bulkiness of the substituted group in diamine. Notably, styrene shows an impressive conversion (94%) with tert-butylhydroperoxide (tert-BuOOH) over the Cu(NNdmen)-MCM-41 catalyst. Whereas, conversion in styrene to styrene-oxide reaction were only 78% and 48% with Cu(NNdeten)-MCM-41 and Cu(NN′dmen)-MCM-41 catalysts, respectively.