Magnetostructural correlations in Cu^II−NC−W^V linkage: the case of [Cu^II(diimine)]²⁺−[W^V(CN)₈]³⁻ 0D assemblies

Tomasz Koznekiak (1) , Cédric Desplanches (2) , Robert Podgajny (1) , Carlos Giménez-Saiz (3) , Michal Rams (4) , Barbara Sieklucka (1)

1 Faculty of Chemistry
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
3 Institute for Material Science
4 M. Smoluchowski Institute of Physics

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)₂·10H₂O (phen = 1,10-phenanthroline) (1) and {[Cu^II(bpy)₂]₂[W^V(CN)₈]} {[Cu^II(bpy)₂][W^V(CN)₈]}·4H₂O (bpy = 2,2′-bipyridyl) (2). Compound 1 consists of cyano-bridged [Cu^II₂W^V₂]²⁻ molecular rectangles and isolated [Cu^II(phen)₃]²⁺ complexes. The molecular structure of 2 reveals cyano-bridged trinuclear [Cu^II₂W^V]⁺ and dinuclear [Cu^IIW^V]⁻ 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 (J₁ = +39(4) cm⁻¹) interacting antiferromagnetically (J₂ = −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.

Mots clés: Chemical synthesis; Crystal structure; Magnetic properties; Cyano bridged molecular assemblies

Domaines: Matériaux

Tomasz Koznekiak, Cédric Desplanches, Robert Podgajny, Carlos Giménez-Saiz, Michal Rams, et al.. Magnetostructural correlations in Cu^II−NC−W^V linkage: the case of [Cu^II(diimine)]²⁺−[W^V(CN)₈]³⁻ 0D assemblies. Inorganic Chemistry, 2009, 48 (7), pp.2865-2872. ⟨10.1021/ic801989b⟩. ⟨hal-00374044⟩