A new series of cyanide-bridged heterobimetallic FeIII–FeIII/MnIII/CuII one-dimensional complexes: synthesis, crystal structures, and magnetic properties†
Abstract
The trans-dicyanide-containing precursor K[Fe(bpdBrb)(CN)2]·2H2O (1) (bpdBrb2− = 1,2-bis(pyridine-2-carboxamido)-4,5-dibromobenzenate) and four transition metal compounds containing FeIII, MnIII or CuII have been employed as building blocks to assemble cyanide-bridged systems, resulting in a series of new cyanide-bridged single chain complexes [Fe(bpdBrb)(CN)]n·nCH3OH (2), {[Mn(L1)][Fe(bpdBrb)(CN)2]}n·nCH3CN (3), {[Mn(L2)][Fe(bpdBrb)(CN)2]}n·2nH2O (4) and {[Cu(cyclam)][Fe(bpdBrb)(CN)2] ClO4}n·nCH3OH (5) (L1 = 5-Brsalpn and L2 = 5-Clsaltn). Single crystal X-ray diffraction analysis reveals the rare one-dimensional “shish-kebab” neutral structure of complex 2 with bpdBrb2− as the equatorial ligand and single cyanide ligands as axial bridges. The other three cyanide-bridged complexes can be structurally characterized as the neutral one-dimensional chains (2 and 3) consisting of alternating units of [Mn(L)]+ (L = L1 or L2) and [Fe(bpdBrb)(CN)2]− and a cationic one-dimensional single chain (4) consisting of the repeating units {NC-[Fe(bpdBrb)]-CN-Cu(cyclam)+} with free ClO4− as the counter-anion. Investigation of the magnetic properties of the four 1D chain complexes reveals the antiferromagnetic coupling between neighbouring low spin Fe(III) ions in complex 2 and the ferromagnetic interaction between the cyanide-bridged Fe(III)–Mn(III)/Cu(II) ions in complexes 3–5. By employing infinite chain models or a MAGPACK program, the magnetic susceptibilities of these complexes were simulated, leading to the magnetic coupling constants J = −1.98(2) cm−1 for 2, J1 = 0.56(1), J2 = 0.45(2) cm−1 for 3, J1 = 0.59(3), J2 = 0.43(8) cm−1 for 4, and J = 1.77(5) cm−1 for 5.