Azido bridge mediated catecholase activity, electrochemistry and magnetic behavior of a dinuclear copper(II) complex of a phenol based "end-off" compartmental ligand

Abstract

A dinuclear Cu(II) species [Cu2L2(H2O)(2)(N-3)](NO3)(2) (L = 2,6-bis(N-ethylpyrrolidine-iminomethyl)-4-methyl- phenolato) where two Cu centers are bridged by phenoxido and mu(1,1)-azido bridges with Cu-Cu separation of similar to 3 angstrom have been synthesized with the view to explore the role of azido bridge on catecholase activity and electrochemical property and the roles of both the bridging groups on magnetic coupling of two copper centers. The complex exhibits excellent catecholase activity in acetonitrile as well as in DMSO medium not only by oxidizing 3,5-di-tert-butylcatechol (3,5-DTBC) but also tetrachlorocatechol (TCC), a catechol which is very thorny to oxidize, under aerobic conditions and becomes the first example of its own kind. CV study reveals three quasi-reversible reductive couples which are tentatively assigned as Cu-2(II) to (CuCuI)-Cu-II and (CuCuI)-Cu-I reduction followed by reduction of (CuCuI)-Cu-I complex to (CuCu0)-Cu-0 species. Variable temperature magnetic study suggests the presence of an antiferromagnetic spin-exchange interaction between Cu(II) ions in the dimer via double bridge where the antiferromagnetic contribution of phenoxido bridge predominates over the ferromagnetic interaction of azido bridge.