Magnetostructural Correlations in CuII-NC-WV Linkage: The Case of [CuII(diimine)]2+-[WV(CN)8]3- 0D Assemblies

We report on the syntheses, crystal structures, and magnetic properties of two cyano-bridged molecular assemblies: [Cu-II(phen)(3)](2){[Cu-II(phen)(2)](2)[W-V(CN)(8)](2)}(ClO4)(2) center dot 10H(2)O (phen = 1,10-phenanthroline) (1) and {[Cu-II(bpy)(2)](2)[W-V(CN)(8)]} {[Cu-II(bpy)(2)][W-V(CN)8]} center dot 4H(2)O (bpy = 2,2'-bipyridyl) (2). Compound 1 consists of cyano-bridged [(Cu2W2V)-W-II](2-) molecular rectangles and isolated [Cu-II(phen)(3)](2+) complexes. The molecular structure of 2 reveals cyano-bridged trinuclear [(Cu2WV)-W-II](+) and dinuclear [(CuWV)-W-II]- ions. Magnetic interactions in 1 are interpreted in terms of the model of a tetranuclear moiety consisting of two ferromagnetic Cu-II-NC-W-V units (J(1) = +39(4) cm(-1)) interacting antiferromagnetically (J(2) = -1.6(4) cm(-1)). The analysis of the magnetic response of 2 reveals ferromagnetic interaction within the [Cu-II-NC-W-V-CN-Cu-II](+) and [Cu-II-NC-W-V]- isolated units, characterized by J = +35(7) cm(-1) and antiferromagnetic coupling between them (4J = -0.30(8) cm(-1)). The discussion of the magnetic behavior and the correlation of the J(CuW) parameters with the geometry of cyano bridges at copper(II) centers of 1 and 2 is based on the DFT calculations, which yield J(av) = +13.2 cm(-1) for 1 and J = +31 cm(-1) for 2. The domination of the ferromagnetic Cu-II-NC-W-V interaction in 1 and 2 originates from the mutual orthogonality of natural magnetic orbitals in the case of coordination of cyano bridges at the equatorial sites of Cu(II) moieties.