Structures and magnetism of two copper(II) compounds with mixed hydroxido-carboxylate bridges derived from isomeric pyridylbenzoate N-oxide ligands

Two Cu(II) coordination polymers with two isomeric pyridylbenzoate N-oxide ligands, 4-(4-pyridyl)benzoic acid N-oxide (4,4-Hopybz) or 4-(3-pyridyl)benzoic acid N-oxide (4,3-Hopybz), were synthesized and structurally and magnetically characterized. They are formulated as [Cu(4,4-opybz)(OH)]_n (1) and [Cu(4,3-opybz)(OH)]_n (2). The two compounds show similar layer structures, in which 1D coordination chains with uniform [(μ-OH)(μ-COO)] double bridges are linked by the 4,4-opybz or 4,3-opybz ligands. Magnetic studies revealed that the mixed double bridges transmit ferromagnetic coupling in the compound 1, and the antiferromagnetic interactions exist in the compound 2. The magnetic differences can be related to the Cu-O-Cu angles influenced by isomeric pyridylbenzoate N-oxide ligands.