Synthesis, structures, and magnetic properties of four copper compounds with 2,2'-dinitrobiphenyl-4,4'-dicarboxylate.

Four copper(II) coordination polymers of 2,2'-dinitrobiphenyl-4,4'-dicarboxylic acid (H(2)dnbpdc), with or without 4,4'-bipyridyl (bipy) as co-ligand, were synthesized under hydrothermal conditions and characterized crystallographically and magnetically. They are formulated as [Cu(2)(dnbpdc)(OH)(2)](n) (1), [Cu(Hdnbpdc)(2)(bipy)](n)·2nH(2)O (2), [Cu(2)(dnbpdc)(2)(bipy)(H(2)O)(2)](n)·2nH(2)O (3) and [Cu(3)(dnbpdc)(2)(bipy)(OH)(2)(H(2)O)](n)·nH(2)O (4). Compound 1 exhibits a 2D coordination network, in which infinite [Cu(μ-OH)(μ-COO)](n) chains are linked by the backbones of the dnbpdc(2-) ligands. Magnetic studies indicated antiferromagnetic coupling through the mixed hydroxo and carboxylate bridges between Cu(II) ions. In 2, mononuclear Cu(II) centers are linked by Hdnbpdc(-) and bipy ligands into 2D grid-like layers. Compound 3 also consists of 2D grid-like coordination layers, which however are based on aqua-bridged Cu(2)(μ-OH(2))(2) units. Magnetic studies showed that the magnetic coupling through the double aqua bridges is antiferromagnetic. Compound 4 exhibits a 3D framework in which [Cu(OH)(COO)](n) chains are linked by bipy and dnbpdc(2-) ligands. The chain has a complicated bridging network involving μ(3)-OH, μ(2)-OH and μ-COO, and magnetic studies revealed overall antiferromagnetic interactions within the chain.