Rational Design and Assembly of a New Series of Cyanide-Bridged FeIII−MnIIOne-Dimensional Single Chain Complexes: Synthesis, Crystal Structures, and Magnetic Properties

Abstract

Two mononuclear seven-coordinated macrocycle manganese(II) compounds and three dicyanide-containing precursors have been employed as building blocks to assemble cyanide-bridged heterobimetallic complexes, resulting in five new cyanide-bridged single chain complexes {[Mn(L(1))][Fe(bpb)(CN)(2)]}ClO(4) x 0.5 H(2)O (2), {[Mn(L(2))][Fe(bpb)(CN)(2)]}ClO(4) x 0.5 H(2)O (3), {[Mn(L(1))][Fe(bpClb)(CN)(2)]}ClO(4) x H(2)O (4), {[Mn(L(2))][Fe(bpClb)(CN)(2)]}ClO(4) x 0.5 H(2)O (5), and {[Mn(L(1))][Fe(bpdBrb)(CN)(2)]}ClO(4) x H(2)O (6). Single X-ray diffraction analysis reveals their one-dimensional (1D) single cyanide-bridged cationic polymeric chain structure consisting of alternating units of [Mn(L)](2+) (L = L(1) or L(2)) and [Fe(L')(CN)(2)](-) (L' = bpb(2-), bpClb(2-) or bpdBrb(2-)) with free ClO(4)(-) as balanced anion. Similar to the mononuclear macrocyclic manganese(II) precursor {[Mn(L(2))(H(2)O)Cl]ClO(4)}.CH(3)OH (1), the coordination geometry of manganese(II) ion in all the 1D complexes is a slightly distorted pentagonal-bipyrimidal with two cyanide nitrogen atoms at the trans positions and N(5) or N(3)O(2) coordinating mode at the equatorial plane from ligand L(1) or L(2). Investigation of the magnetic properties of these five 1D single chain cyanide-bridged Fe(III)-Mn(II) complexes reveals the antiferromagnetic magnetic coupling between neighboring Fe(III) and Mn(II) ions through the bridging cyanide group. A best-fit to the magnetic susceptibilities of these complexes based on the 1D alternating chain model leads to the magnetic coupling constants J(1) = -1.16(2) and J(2) = -0.10(3) cm(-1) for 2, J(1) = -3.10(1) and J(2) = -0.25(1) cm(-1) for 3, J(1) = -1.10(1) and J(2) = -0.139(8) cm(-1) for 4, J(1) = -1.99(6) and J(2) = -0.57(1) cm(-1) for 5, and J(1) = -1.23(1) and J(2) = -0.13(5) cm(-1) for 6, respectively. This work will provide valuable information for the rational design and synthesis of low-dimensional, in particular, single chain, cyanide-bridged magnetic complexes.