title: Defective dicubane-like tetranuclear nickel(II) cyanate and azide nanoscale magnets.
abstract: Four tetrameric nickel(II) pseudohalide complexes have been synthesized and structurally, spectroscopically, and magnetically characterized. Compounds 1-3 are isostructural and exhibit the general formula [Ni(2)(dpk·OH)(dpk·CH(3)O)(L)(H(2)O)](2)A(2)·2H(2)O, where dpk = di-2-pyridylketone; L = N(3)(-), and A = ClO(4)(-) for 1, L = NCO(-) and A = ClO(4)(-) for 2, and L = NCO(-) and A = NO(3)(-) for 3. The formula for 4 is [Ni(4)(dpk·OH)(3) (dpk·CH(3)O)(2)(NCO)](BF(4))(2)·3H(2)O. The ligands dpk·OH(-) and dpk·CH(3)O(-) result from solvolysis and ulterior deprotonation of dpk in water and methanol, respectively. The four tetramers exhibit a dicubane-like core with two missing vertexes where the Ni(II) ions are connected through end-on pseudohalide and oxo bridges. Magnetic measurements showed that compounds 1-4 are ferromagnetic. The values of the exchange constants were determined by means of a theoretical model based on three different types of coupling. Thus, the calculated J values (J(1) = J(2), J(3), and D) were 5.6, 11.8, and 5.6 cm(-1) for 1, 5.5, 12.0, and 5.6 cm(-1) for 2, 6.3, 4.9, and 6.2 cm(-1) for 3, and (J(1), J(2), J(3), and D) 6.9, 7.0, 15.2, and 4.8 cm(-1) for 4.
authors.affiliation: Departamento de Química Inorgánica, Universidad del Paı´s Vasco, Apartado 644, 48080 Bilbao,Spain.
authors.forename: Zurine
authors.initials: Z
authors.lastname: Serna
authors.forename: Noelia
authors.initials: N
authors.lastname: De la Pinta
authors.forename: M Karmele
authors.initials: MK
authors.lastname: Urtiaga
authors.forename: Luis
authors.initials: L
authors.lastname: Lezama
authors.forename: Gotzon
authors.initials: G
authors.lastname: Madariaga
authors.forename: J Modesto
authors.initials: JM
authors.lastname: Clemente-Juan
authors.forename: Eugenio
authors.initials: E
authors.lastname: Coronado
authors.forename: Roberto
authors.initials: R
authors.lastname: Cortés