Two WV–MnIII bimetallic assemblies built by octacyanotungstate(v) and MnIIISchiff bases: molecular structures and a spin-flop transition

Abstract

Two W^V–Mn^III bimetallic compounds, [Mn(Cl-salmen)(H₂O)₂]{[Mn(5-Clsalmen)(H₂O)]₂[W(CN)₈]·2H₂O (1·2H₂O) [5-Clsalmen = N,N′-(1-methylethylene)bis(5-chlorosalicylideneiminato) dianion], which contains trinuclear Mn₂W and isolated Mn^III moieties, and [Mn(3-MeOsalcy)(H₂O)₂]₃[W(CN)₈]·2H₂O (2·2H₂O) [3-MeOsalcy = N,N′-(trans-1,2-cyclohexanediylethylene)bis(3-methoxysalicylideneiminato) dianion] molecules were prepared in redox processes and characterized using X-ray analysis and magnetic measurements. Compound 1 is composed of the {[Mn(5-Clsalmen)(H₂O)]₂[W(CN)₈]}⁻ trimer, in which two CN groups among eight in [W(CN)₈]³⁻ bridge W⁵⁺ and two Mn³⁺ ions and the remaining CN ligands are hydrogen-bonded to water molecules or unbound, and the [Mn(Cl-salmen)(H₂O)₂]⁺ cation. Subsequently, two water molecules of the isolated cation are subject to hydrogen bonds. For 2, there are no covalent bonds among the subunits and six serial stacks of [Mn(3-MeOsalcy)(H₂O)₂]⁺ units are all hydrogen-bonded. The many hydrogen bonds found in both complexes eventually lead to three-dimensional networks. The magnetic studies for 1 reveal that antiferromagnetic interactions (J = −5.4 cm⁻¹) between W^V and Mn^III centers within the trimer are transmitted via the bridging CN groups. Intermolecular antiferromagnetic couplings (zJ′ = −0.2 cm⁻¹) are also observed. The static and dynamic magnetic data of 1 demonstrate the existence of a field-induced spin-flop transition occurring among the clusters and monomeric molecules.