Crystallographic and magnetic studies of the 2-pyridone/copper halide system

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• The syntheses of [(2-pyridone)2CuX2]2 (X = Cl, Br), [(2-pyridone)CuCl2]2, (2-pyridone)3CuCl2, and (2-pyridone)2 [CuCl2(H2O)2] are reported.
• The [(2-pyridone)2CuX2]2 (X = Cl, Br) complexes crystallize as O-bridged dimers and show significant antiferromagnetic exchange (J = −38.2(1), −41.7(1) K).
• [(2-pyridone)CuCl2]2 exhibits ferromagnetic exchange (J = +9(1) K) via a bichloride bridge. The dimers interact antiferromagnetically.
• In spite of a similar bichloride bridge, (2-pyridone)2 [CuCl2(H2O)2] exhibits only weak ferromagnetic exchange.

A series of copper halide complexes have been prepared employing 2-pyridone as a ligand. The compounds [CuBr2(2-pyridone)2]2 (1), [CuCl2(2-pyridone)2]2 (2), [CuCl2(2-pyridone)]2 (3), [CuCl2(2-pyridone)3] (4), and [CuCl2·2H2O]2[(2-pyridone)2] (5) were prepared and their structures and magnetic properties studied. Compounds 1 and 2 are dimeric species with the Cu(II) ions bridged by a pair of O-atoms from 2-pyridone molecules. Compound 3 is also a dimer, but in this case bridged by a pair of chloride ions. Only compound 4 is monomeric with fairly well isolated copper(II) ions, while compound 5 is a coordination polymer with the Cu(II) ions linked into chains via pairs of bridging chloride ions. Analysis of the magnetic data reveals that 1 and 2 exhibit significant antiferromagnetic interactions, while 4 is very weakly antiferromagnetic. Compounds 3 and 5 show weak ferromagnetic interactions. Data for 1 and 2 were fit to the antiferromagnetic dimer model with a Curie–Weiss correction to account for interdimer interactions: 1, J = −41.7(1) K, θ = −0.8(1) K; 2, J = −38.2(1) K, θ = −0.7(1) K. Data for 3 were fit to the ferromagnetic dimer model with a Curie–Weiss correction for interdimer interactions:); 2, J = 9.4(6), θ = −3.2(3). Interactions in both 4 and 5 were sufficiently weak that data were fit only to the Curie–Weiss expression resulting in θ-values of −0.50(7) and 0.58(4) K respectively.

Copper(II) bromide and chloride complexes of 2-pyridone of the formula CuX2(2-pyridone)n(H2O)m (X = Cl, Br; n = 1, 2,3; m = 0, 2) have been prepared and studied magnetically and crystallographically. Three of the complexes form dimers linked either via bichloride bridges, or via bridging 2-pyridone O-atoms, while one forms an isolated species and one forms a chloride bibridged coordination polymer. The complexes exhibit a mixture of ferromagnetic and antiferromagnetic interactions.Figure optionsDownload as PowerPoint slide