Cu(ii) complexes of N-rich aroylhydrazone: magnetism and catalytic activity towards microwave-assisted oxidation of xylenes

Abstract

The new aroylhydrazone N′-(di(pyridin-2-yl)methylene)pyrazine-2-carbohydrazide (HL) species, rich in N-donor sites, has been used to synthesize Cu(II) compounds with different nuclearities, viz. the binuclear [Cu₂(μ-1κN³,2κN²O-L)(Cl)₃(MeOH)] (1), the octanuclear [Cu₄(μ-1κN³,2κN²O-L)₂(μ-Cl)₃(Cl)₃]₂ (2) and the 1D coordination polymer [Cu₃(μ₃-1κN³,2κN²O,3κN-L)(μ-NO₃)(NO₃)₃(H₂O)₃]_n·nNO₃ (3). They have been characterized by elemental analysis, FT-IR and single crystal X-ray diffraction. The magnetic properties of 2 and 3 have been explored using variable temperature magnetic measurements. The catalytic performances of the compounds were evaluated towards the peroxidative oxidation of o-, p- and m-xylenes under microwave irradiation, leading to the formation of the corresponding methyl benzyl alcohol, tolualdehyde and toluic acid as the major products. Complex 3 exhibits the best catalytic activity towards the oxidation of p-xylene with a total yield of 37% (4-methylbenzyl alcohol + p-tolualdehyde + p-toluic acid).