Heterogenization of a Functionalized Copper(II) Schiff Base Complex by Direct Immobilization onto an Oxidized Activated Carbon

Abstract

A copper(II) Schiff base complex bearing hydroxyl groups [bis(4-hydroxysalicylaldehyde)ethylenediaminate] copper(II), [Cu(4-HOsalen)], was directly anchored onto an air-oxidized activated carbon. Oxidation of the activated carbon was done with a mixture of air and N2 (with 5% O2) to increase the oxygenated surface functional groups, and complex immobilization was made by attachment of the metal complex hydroxyl groups to carbon surface groups. The adsorption/desorption of the metal complexes onto the oxidized activated carbon was monitored by UV-vis spectroscopy. Carbon-based materials were characterized by elemental analysis, surface techniques (scanning electron microscopy and X-ray photoelectron microscopy), nitrogen adsorption isotherms, and thermal analysis (temperature-programmed desorption and thermogravimetry). EPR spectra of both free and carbon-supported [Cu(4-HOsalen)] complexes were recorded. A comparative study with the unfunctionalized copper complex, [Cu(salen)], was also performed to assess the role of the hydroxyl groups in copper complex anchorage. Data from all the techniques have provided evidence that copper complexes with the hydroxyl functionalized Schiff base are chemically bound to carbon surface groups through the ligand substituent, whereas the unfunctionalized complex, [Cu(salen)], was only physically adsorbed onto the activated carbon and was leached during Soxhlet extraction.

A novel iron(iii)-based heterogeneous catalyst for aqueous oxidation of alcohols using molecular oxygen

“…5a) the high resolution spectrum exhibits two peaks at 398.0 eV and 400.2 attributable to amine and imine group respectively. 16 The Fe(2p) band (Fig. 5b) splits into two peaks, 2p 3/2 and 2p 5/2, with corresponding binding energies at 711.1 eV and 724.8 eV respectively and the values are very much close to the Fe2p binding energies of reported iron(III) compounds.…”

Amine‐Functionalised Hexagonal Mesoporous Silica as Support for Copper(II) Acetylacetonate Catalyst

“…[17] Furthermore, the spectroscopic characterisation by DRIFT and UV spectroscopy of the new carbon-based heterogeneous catalysts proved to be difficult and impossible, respectively, due to the highly absorbing carbon matrix, which limited the gathering of information about the copper() complex formed on the surface of the amine-functionalised activated carbon. Immobilisation on several porous supports of (Schiff base)copper() complexes previously synthesised [18] or prepared in situ on the porous structure, [19,20] have also been reported in the literature.…”

Catalytic Oxidation of Cyclohexene with Hydrogen Peroxide over Cu(II)-Cyclam-SBA-16 Catalyst

“…Various strategies such as encapsulation in zeolites, 1,2 immobilization in porous alumina, 3 immobilization in mesoporous silica 4 and grafting on polymers or porous carbon 5,6 have been developed in terms of heterogenization of homogeneous catalysts. Among various kinds of the reported heterogeneous supports, ordered mesoporous silicas have applied for many applications in the field of heterogeneous catalysis due to their well-defined and highly accessible pore sizes and large surface areas.…”

“…[8][9][10] Copper-ion based catalysts have received much attention because of wide use in many catalytic reactions. 4,6,[11][12][13][14] However, up to now, only a few studies have been reported on the utilization of copper cyclam complex immobilized mesoporous silica. The cyclam has been well known as macrocyclic ligand that can accommodate and stabilize various high oxidation state transition metal cations.…”