Ligand-directed assembly of cyanide-bridged bimetallic (MnFeIII)-Fe-II coordination polymers based on the pentacyanoferrite(III) building blocks

Rarely investigated pentacyanoferrate(III) building blocks, [Fe(CN)(5)(L)](2-) (L = 1-methylimdazole (1-CH(3)im), imidazole (imH)), have been used to prepare cyanide-bridged bimetallic polymeric Mn(II)-Fe(III) complexes {[Mn(bpy)(H2O)(2)Fe(CN)(5)(1-CH(3)im)]center dot H2O}(n) (1), {[Mn(bpy)Fe(CN)(5)(imH)]center dot H2O}(n) (2) and {[Mn(CH3OH)(2)Fe(CN)(5)(imH)]}(n) (3) (bpy 2,2'-bipyridine). Complexes 1 and 2 were obtained via the reactions of Mn(bpy)(2)Cl-2 center dot EtOH with [Fe(CN)(5)(L)](2-) (L = 1-CH(3)im and imH, respectively), and complex 3 via the reaction between MnCl2 center dot 2H(2)O and [Fe(CN)(5)(imH)](2-) in absolute methanol. Complex 1 is a one-dimensional alternate Mn(II)-Fe(III) chain, while complexes 2 and 3 are two-dimensional comprised of Fe2Mn2 squares. Complexes 2 and 3 show interesting intra- or interlayer pi-pi interactions between imidazole and pyridine rings of bpy. Partial loss of the bpy ligand and the pi-pi contacts has a direct effect on the molecular structures of complexes 1-3. Antiferromagnetic interaction between high-spin Mn( II), and low-spin Fe( III) has been observed in complexes 1-3, and the layered complexes 2 and 3 display long-range magnetic ordering at the critical temperature of 4.4 K (T-N) for 2 and 5.0 K (T-c) for 3. A best-fit to the magnetic susceptibility of the 1D complex 1 has given the magnetic coupling constant of J(MnFe) = -6.16(9) cm(-1) based on an antiferromagnetic chain model of alternate S-Fe = 1/2 and S-Mn = 5/2 spins.National Natural Science Foundation of China [20671055, 20771065

Supramolecular metallomacrocycles based on trans-dicyanoferrite(III) building blocks: synthesis, crystal structure and magnetic properties

The reaction of trans-[Fe(R-bpb)(CN)(2)](-) (R-bpb(2-)= R-substituted-1,2-bis(pyridine-2-carboxamido)benzenate) with trans-Mn(III) Schiff base complexes [Mn(5-X-saltn)]ClO4 (5-X-saltn(2-) = N,N'-propanolbis(5-X-substituted-salcylideneiminato) dianion) gave rise to cyanide-bridged neutral binuclear [MnFe] compounds [Mn(saltn)(MeOH)][Fe(bpb)(CN)(2)]center dot 3H(2)O ( 1), [Mn(saltn)(H2O)Fe(bpmb)(CN)(2)] center dot H2O (2), [Mn(saltn)(MeOH)Fe(bpClb)(CN)(2)]center dot 2H(2)O ( 3), and ionic [Mn2Fe](+)-[Fe](-) complexes [Mn-2(5-Br-saltn)(2)(H2O)(EtOH)Fe(bpb)(CN)(2)][Fe(bpb)(CN)(2)]center dot 6H(2)O ( 4) and [Mn-2(5-Cl-saltn)(2)(CH3OH)(EtOH)Fe(bpb)(CN)(2)][Fe(bpb)(CN)(2)]center dot 5H(2)O center dot MeCN (5). Four binuclear units of complexes 1-3 assemble in a head-to-tail way via hydrogen bonding giving rise to a metallo-supramolecular [MnFe](4) square, while two [Mn2Fe](+)-[Fe](-) units of complexes 4-5 form a metallo-supramolecular macrocyclic structure. Magnetic studies reveal that complexes 1-3 and 5 exhibit intermetallic ferromagnetic coupling, while complex 4 displays antiferromagnetic interaction between low-spin Fe(III) and high-spin Mn(III) through the cyanide bridges. Complexes 1, 4 and 5 display frequency dependent of current-alternating (ac) magnetic susceptibility, typical of the presence of slow magnetization relaxation. Because of the existence of intermolecular magnetic interaction, complex 4 shows an exchange-biased single-molecule magnet (SMM) behavior below 0.5 K.Natural Science Foundation of China [20671055, 50873053]; Program for New Century Excellent Talents in Universit

One-Dimensional Mn(III) Coordination Polymer Exhibiting Ferromagnetic Coupling

Mn(III) complexes of 1-(2-hydroxybenzamido)-2-((2-hydroxy-3-methoxybenzylidene)amino)ethane (H3L), mononuclear [Mn(L)(MeOH)(H2O)] (1) and amido-bridged one-dimensional [Mn(L)(H2O)](infinity) (2), have been synthesized by the reaction of MnAc3-2H20 with H3L. Magnetic studies revealed that complex 2 exhibits intermetallic ferromagnetic coupling, which is the first one-dimensional highspin Mn(III) complex with ferromagnetic behavior.National Natural Science Foundation of China [20771065]; Fok Ying Tong Education Foundation [91016