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

Abstract

Three cyanido-bridged Fe-III-Mn-II dimers, [Fe(pzcq)(CN)(3)][Mn(phen)(2)(X)]center dot MeOH [X = Cl (1), Br (2); pzcq = 8-(pyrazine2-carboxaniido)quinoline anion, phen = 1,10-phenanthroline], [Fe(mpzcq)(CN)(3)][Mn(phen)(2)(Cl)]center dot MeOH [3; mpzcq = 8-(5-methylpyrazine-2-carboxamido)quinoline anion], and one W-V-Mn-II dinuclear system, [W(bpy)(CN)(6)][Mn(phen)(2)(Cl)]center dot 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)(2)X-2. The absolute configurations of the Mn polyhedra surrounded by two bidentate phen ligands are packed in a -Delta-Delta-Delta-Delta- sequence in the crystal lattice. The aromatic rings of the coordinated phen ligands are sources of considerable interdimer pi-pi contacts, which eventually lead to the formation of two-dimensional frameworks (1-3) and a one-dimensional chain structure (4). Magnetic analyses of the Fe-III-Mn-II 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. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008.