A Helical Metal−Metal Bonded Chain via the Pt→Ag Dative Bond

A Helical Metal−Metal Bonded Chain via the Pt→Ag Dative Bon

A Ferromagnetic Interaction between Cu²⁺ Centers through a [CrO₄]^2- Bridge: Crystal Structures and Magnetic Properties of [{Cu(acpa)}₂(μ-MO₄)] (M = Cr, Mo) (Hacpa = <i>N</i>-(1-Acetyl-2-propyridene)(2-pyridylmethyl)amine)

The reaction of [Cu(acpa)]+ with [MO4]2- (Hacpa = N-(1-acetyl-2-propyridene)(2-pyridylmethyl)amine and M = Cr and Mo) in water−methanol or water−acetonitrile solution affords dinuclear copper(II) complexes with metalate bridges, [{Cu(acpa)}2(μ-CrO4)]·4CH3OH·4H2O (1) and [{Cu(acpa)}2(μ-MoO4)]·4H2O (2), respectively. The crystal structures and the magnetic properties have been studied. Complexes 1 and 2 are isomorphous and the structures are made up of discrete dimers in which two copper(II) ions are bridged by the [MO4]2- anion. The coordination geometry about the copper(II) ions is square planar with a N2O chelate group from acpa and an oxygen atom from [MO4]2-. Magnetic susceptibility measurements for 1 revealed that a ferromagnetic interaction between copper(II) ions is propagated through the [CrO4]2- bridge and the coupling constant (2J) was evaluated to be 14.6(1) cm-1 (H = −2JS1·S2). In 2, two copper(II) ions bridged by [MoO4]2- anion are antiferromagnetically coupled with the 2J value of −5.1(4) cm-1. The ferromagnetic interaction in 1 is explained by means of the orbital topology of frontier orbitals. Crystal data:  1, monoclinic, space group P21/m, a = 8.349(2) Å, b = 17.616(3) Å, c = 10.473 Å, β = 107.40(2)°, Z = 2; 2, monoclinic, space group P21/m, a = 8.486(2) Å, b = 18.043(3) Å, c = 9.753(2) Å, β = 95.82(2)°, Z = 2

Superparamagnetic Behavior in an Alkoxo-Bridged Iron(II) Cube

Superparamagnetic Behavior in an Alkoxo-Bridged Iron(II) Cub

The First Examples of Platinum(II)−Cadmium(II) Bonds: The Role of Strong Field Ligands in Making Dative Pt→M Bonds

The First Examples of Platinum(II)−Cadmium(II) Bonds:  The Role of Strong Field Ligands in Making Dative Pt→M Bond

Superparamagnetic Behavior in an Alkoxo-Bridged Iron(II) Cube

Superparamagnetic Behavior in an Alkoxo-Bridged Iron(II) Cub

Cyanide-Bridged Molecular Squares with Ferromagnetically Coupled dπ, dσ, and pπ Spin System

Cyanide-bridged molecular squares of [FeII2CuII2(μ-CN)4(dmbpy)4(impy)2](ClO4)4·4CH3OH·C6H6 (1) and of [FeIII2CuII2(μ-CN)4(dmbpy)4(impy)2](ClO4)6·4CH3OH·4H2O (2) (dmbpy = 4,4‘-dimethyl-2,2‘-bipyridine; impy = 2-(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy) were prepared. In the squares of 1 and 2, the Fe(II/III) (low spin) and Cu(II) ions are alternately bridged by the cyanide groups, in which the cyanide carbon atoms coordinated to the Fe(II) ions and Cu(II) ions are coordinated by imino nitroxide. Magnetic susceptibility measurements for 1 and 2 revealed that the Cu(II) ion and imino nitroxide are ferromagnetically coupled with a fairly strong coupling constant (JCu-radical > 300 K) and act as triplet species. In 1 the Cu(II)−radical moieties are magnetically separated by the Fe(II) ions. In the square of 2, dπ (Fe(III)), dσ (Cu(II)), and pπ (imino nitroxide) spins are alternately assembled, and this situation allowed the square to have an S = 3 spin ground state. The exchange coupling constant of Fe(III) and the Cu(II)−radical moiety in 2 was estimated to be J = 4.9 cm-1 (H = −2J∑SFe·SCu-radical)

A Helical Metal−Metal Bonded Chain via the Pt→Ag Dative Bond

A Helical Metal−Metal Bonded Chain via the Pt→Ag Dative Bon

The First Examples of Platinum(II)−Cadmium(II) Bonds: The Role of Strong Field Ligands in Making Dative Pt→M Bonds

The First Examples of Platinum(II)−Cadmium(II) Bonds:  The Role of Strong Field Ligands in Making Dative Pt→M Bond

Radical Double Helicates of Silver Imino Nitroxides, [Ag₂(pyrd-im2)₂](PF₆)₂·2CH₃OH and [Ag₂(bpy-im2)₂](PF₆)₂·CH₃OH

Radical Double Helicates of Silver Imino Nitroxides, [Ag2(pyrd-im2)2](PF6)2·2CH3OH and [Ag2(bpy-im2)2](PF6)2·CH3O

Single-Molecule Magnets of Ferrous Cubes: Structurally Controlled Magnetic Anisotropy

Tetranuclear FeII cubic complexes were synthesized with Schiff base ligands bridging the FeII centers. X-ray structural analyses of six ferrous cubes, [Fe4(sap)4(MeOH)4]·2H2O (1), [Fe4(5-Br-sap)4(MeOH)4] (2), [Fe4(3-MeO-sap)4(MeOH)4]·2MeOH (3), [Fe4(sae)4(MeOH)4] (4), [Fe4(5-Br-sae)4(MeOH)4]·MeOH (5), and [Fe4(3,5-Cl2-sae)4(MeOH)4] (6) (R-sap and R-sae were prepared by condensation of salicylaldehyde derivatives with aminopropyl alcohol and aminoethyl alcohol, respectively) were performed, and their magnetic properties were studied. In 1−6, the alkoxo groups of the Schiff base ligands bridge four FeII ions in a μ3-mode forming [Fe4O4] cubic cores. The FeII ions in the cubes have tetragonally elongated octahedral coordination geometries, and the equatorial coordination bond lengths in 4−6 are shorter than those in 1−3. Dc magnetic susceptibility measurements for 1−6 revealed that intramolecular ferromagnetic interactions are operative to lead an S = 8 spin ground state. Analyses of the magnetization data at 1.8 K gave the axial zero-field splitting parameters (D) of +0.81, +0.80, +1.15, −0.64, −0.66, and −0.67 cm-1 for 1−6, respectively. Ac magnetic susceptibility measurements for 4−6 showed both frequency dependent in- and out-of-phase signals, while 1−3 did not show out-of-phase signals down to 1.8 K, meaning 4−6 are single-molecule magnets (SMMs). The energy barriers to flip the spin between up- and down-spin were estimated to 28.4, 30.5, and 26.2 K, respectively, for 4−6. The bridging ligands R-sap2- in 1−3 and R-sae2- in 4−6 form six- and five-membered chelate rings, respectively, which cause different steric strain and Jahn−Teller distortions at FeII centers. The sign of the D value was discussed by using angular overlap model (AOM) calculations for irons with different coordination geometry