Structural chemistry and magnetic properties of copper pyromellitate coordination polymers containing pyridylnicotinamide ligands

A series of divalent copper pyromellitate (1,2,4,5-benzenetetracarboxylate, pyro) coordination polymers containing either 3-pyridylnicotinamide (3-pna) or 4-pyridylnicotinamide (4-pna) was hydrothermally prepared and structurally characterized by single-crystal X-ray diffraction. [Cu-2(pyro)(pyroH(2)) (3-pnaH)(2)(H2O)(2)](n) (1) is a 2-D coordination polymer built from {Cu2O2(OCO)(2)} dimeric units, while {[Cu(pyro)(3-pnaH)(2)(H2O)(2)]center dot 4H(2)O}(n) (2) is a simple neutral 1-D chain polymer. {[Cu(pyroH(2))(4-pnaH)(2) (H2O)(2)](pyroH(2))center dot 2H(2)O}(n) (3) possesses cationic 1-D chain motifs and unligated pyroH(2) dianions. {[Cu-2(pyroH(2))(3)(4-pnaH)(2)]center dot 6H(2)O}(n) (4) is also a 1-D coordination polymer, but built from the linkage of {Cu-2(pyroH(2))} dimeric units. {[Cu-3(pyroH)(2)(4-pna)(2)(H2O)(2)]center dot 2H(2)O}(n) (5) manifests a 3-D coordination polymer network with rare frl topology, containing embedded {Cu-3(OCO)(2)} linear trimers. Moderately strong antiferromagnetic coupling (J = -76.4(3) cm(-1)) was observed within the {Cu2O2(OCO)(2)} dimeric units in 1, while very weak ferromagnetic coupling (J = 0.8(2) cm(-1)) was observed within the {Cu-3(OCO)(2)} linear trimers in 5. Thermal degradation behavior of the five new materials is also presented. (C) 2013 Elsevier B.V. All rights reserved.