Catecholase activity, electrochemistry and magnetic behavior of a azido bridged dinuclear copper(II) complex of a phenol based‘‘end-off” compartmental ligand

A dinuclear Cu(II) species [Cu₂L₂(H₂O)₂(N₃)](NO₃)₂ (L = 2,6-bis(N-ethylpyrrolidine-iminomethyl)-4-methyl-phenolato) where two Cu centers are bridged by phenoxido and l1,1-azido bridges with Cu–Cu separation of  3 Å 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 Cu₂ ^II to Cu^IICu^I and Cu^ICu^I reduction followed by reduction of CuICuI complex to Cu0Cu0 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.