Crystal structures and magnetic behaviors of cyanido-bridged dinuclear dimetallic systems involving 3d-3d or 3d-5d metal centers

Three cyanido-bridged FeIII–MnII dimers, [Fe(pzcq)(CN)3][Mn(phen)2(X)]·MeOH [X = Cl (1), Br (2); pzcq = 8-(pyrazine-2-carboxamido)quinoline anion, phen = 1,10-phenanthroline], [Fe(mpzcq)(CN)3][Mn(phen)2(Cl)]·MeOH [3; mpzcq = 8-(5-methylpyrazine-2-carboxamido)quinoline anion], and one WV–MnII dinuclear system, [W(bpy)(CN)6][Mn(phen)2(Cl)]·MeOH (4; bpy = 2,2′-bipyridine), were prepared by assembling molecular precursors, [Fe(pzcq)(CN)3]–, [Fe(mpzcq)(CN)3]–, and [W(bpy)(CN)6]–, with Mn(phen)2X2. The absolute configurations of the Mn polyhedra surrounded by two bidentate phen ligands are packed in a –Δ–Λ–Δ–Λ– sequence in the crystal lattice. The aromatic rings of the coordinated phen ligands are sources of considerable interdimer π–π contacts, which eventually lead to the formation of two-dimensional frameworks (1–3) and a one-dimensional chain structure (4). Magnetic analyses of the FeIII–MnII dinuclear systems (1–3) reveal that a shorter Mn–N(cyanide) bond and a more linear Mn–N–C(cyanide) angle allow for stronger magnetic exchange coupling. Moreover, it is manifested that the 3d–5d magnetic coupling in 4 is stronger than the 3d–3d coupling in 1–3 under the given structural environments, which is due to the fact that the 5d orbital is more diffuse than the 3d orbital. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)