A novel mixed azido/phenoxido bridged 1D CuII coordination polymer containing o-vanillin-based compartmental ligand: Synthesis, magnetism, phenoxazinone synthase and catalytic activity in epoxidation of alkenes

A novel 1-D coordination polymer, formulated as [Cu-2(L)(N-3)(3)]center dot H2O (1), has been synthesized by reacting the Schiff base ligand, 2-methoxy-6-((2-(2-hydroxyethylamino)ethylimino) methyl)-phenol (HL), with copper(II) chloride dihydrate in the presence of sodium azide. The X-ray structural analysis shows that compound 1 consists of tetranuclear [Cu-2(L)(N-3)(3)](2) units bearing a central double asymmetric mu(1,1)-N-3 bridge and terminal mixed mu(1,1)-N-3/phenoxido bridges that are linked via a double mu(1,1,3)-N-3 bridge forming a 1-D network. The magnetic properties of 1 show the presence of ferromagnetic Cu center dot center dot center dot Cu interactions through the central double mu(1,1)-N-3 bridge (J(1) = 81.7(3) cm(-1)) coexisting with antiferromagnetic Cu center dot center dot center dot Cu interactions through the double mu(1,1)-N-3/phenoxido bridge (J(2) = -62.3(4) cm(-1)). Additionally, there is a very weak antiferromagnetic interaction (zJ = -0.12 (2) cm(-1)) through the asymmetric mu(1,1,3)-N-3 bridge connecting the tetranuclear units. Using o-aminophenol (OAP) as a substrate, the phenoxazinone synthase-like catalytic activity of the Cu-II coordination polymer 1 has been studied. The compound efficiently catalyzes the aerobic oxidation of o-aminophenol in DMF medium with a turnover number K-cat = 31.69 h(-1). Moreover, 1 has been used as an active catalyst for the epoxidation of ciscyclooctene, as a model alkene, with tert-butyl hydroperoxide (TBHP), showing an excellent epoxide yield and selectivity in CHCl3 under reflux conditions. To enlarge the scope of the reaction, the efficacy of the catalytic method has also been investigated in the epoxidation of some other substituted alkenes.