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

Abstract

A novel 1-D coordination polymer, formulated as [Cu2(L)(N3)3]·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 [Cu2(L)(N3)3]2 units bearing a central double asymmetric μ1,1-N3 bridge and terminal mixed µ1,1-N3/phenoxido bridges that are linked via a double µ1,1,3-N3 bridge forming a 1-D network. The magnetic properties of 1 show the presence of ferromagnetic Cu···Cu interactions through the central double μ1,1-N3 bridge (J1 = 81.7(3) cm−1) coexisting with antiferromagnetic Cu···Cu interactions through the double µ1,1-N3/phenoxido bridge (J2 = –62.3(4)cm−1). Additionally, there is a very weak antiferromagnetic interaction (zJ = –0.12(2) cm−1) through the asymmetric µ1,1,3-N3 bridge connecting the tetranuclear units. Using o-aminophenol (OAP) as a substrate, the phenoxazinone synthase-like catalytic activity of the CuII coordination polymer 1 has been studied. The compound efficiently catalyzes the aerobic oxidation of o-aminophenol in DMF medium with a turnover number Kcat = 31.69 h−1. Moreover, 1 has been used as an active catalyst for the epoxidation of cis-cyclooctene, 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.