Structures with Tunable Strong Ferromagnetic Coupling: from Unordered (1D) to Ordered (Discrete)

The X-ray crystal structures, magnetic susceptibilities from 2 to 300 K, and theoretical analyses of the magnetism for 1D and trinuclear azido Cu(II) carboxylate complexes [Cu(1.5)(hnta)(N(3))(2)(H(2)O)](n) (1) and [Cu(3)(hnta)(4)(N(3))(2)(H(2)O)(3)] (2), respectively, where hnta is 6-hydroxynicotinate, are described. Although both exhibit strong ferromagnetic coupling, discrete complex 2 exhibits long-range ferromagnetic ordering, while the very similar 1D system 1 does not. Density functional calculations provided accurate J values and allowed rationalization of the ferromagnetic coupling in terms of the magnetic orbitals and spin densities.