Crystal Structures and Magnetic Behaviors of Cyanido‐Bridged Dinuclear Dimetallic Systems Involving 3d–3d or 3d–5d Metal Centers

Three cyanido‐bridged Fe III –Mn II 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 W V –Mn II 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) 2 X 2 . 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 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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)