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

• Azido bridged di-Cu(II) complex of phenol based “end-off” compartmental ligand synthesized and characterized.
• The complex catalyzes aerobic oxidation of 3,5-DTBC as well as TCC, a substrate very hard to oxidize.
• First ever example of azido bridged di-Cu(II) as a synthetic analog of the active site of catechol oxidase.
• Variable temperature magnetic study reveals antiferromagnetic interaction between two Cu(II) centers.

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 μ1,1-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 Cu2II to CuIICuI and CuICuI 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.

An azido bridged dinuclear copper(II) complex exhibits excellent catecholase activity against 3,5-DTBC and TCC. Magnetic behavior of the complex indicates phenoxo-bridged controlled antiferromagnetic coupling dominates over the azide route.Figure optionsDownload as PowerPoint slide