A comparative study of the structural, electrochemical and magnetic properties of Copper(II)-squarate coordination frameworks

Three new copper(II)-squarate coordination polymers, 1-D double-chain {Cu(C4O4)(H2O)(2)(DMF)}(n) (1) (=dianion of 3,4-dihydroxy-3-cyclobuten-1,2-dione), 3-D network {[Cu(C4O4)(H2O)(2)]0.33H(2)O}(n) (2), and 3-D network {[Cu(C4O4)(H2O)(2)]0.33CH(3)OH}(n) (3), have been synthesized and characterized structurally. The complexes show altered assembly behavior in different solvent systems, which can further affect the physical properties of the frameworks. Cyclic voltammetry experiments show that 1, 2, and 3 have rich redox activities and both Cu(II) ions and squaric acid ligands are involved in redox process. Magnetic characterization on 3 shows the effect of weak antiferromagnetic exchange.