A Nontwisted, Ferromagnetically Coupled Mn^III₃O Triangular Complex from the Use of 2,6-Bis(hydroxymethyl)-<i>p</i>-cresol

The reaction between Mn(O2CMe)2·4H2O and hmcH3 [hmcH3 = 2,6-bis(hydroxymethyl)-p-cresol] in CH2Cl2 in the presence of NEt3 affords the MnIII3 complex [NEt3(CH2Cl)]2[Mn3O(hmcH)3(hmcH2)3] (1). The anion of 1 contains a [MnIII3(μ3-O)]7+ triangular core, with the central O2− ion lying above the Mn3 plane. The complex is ferromagnetically coupled with a resulting S = 6 ground state

Synthetic Entry into Polynuclear Bismuth–Manganese Chemistry: High Oxidation State Bi^III₂Mn^IV₆ and Bi^IIIMn^III₁₀ Complexes

The first high nuclearity, mixed-metal BiIII/MnIV and BiIII/MnIII complexes are reported. The former complexes are [Bi2MnIV6O9(O2CEt)9(HO2CEt)(NO3)3] (1) and [Bi2MnIV6O9(O2CPh)9(HO2CPh)(NO3)3] (2) and were obtained from the comproportionation reaction between Mn(O2CR)2 and MnO4– in a 10:3 ratio in the presence of Bi(NO3)3 (3 equiv) in either a H2O/EtCO2H (1) or MeCN/PhCO2H (2) solvent medium. The same reaction that gives 2, but with Bi(O2CMe)3 and MeNO2 in place of Bi(NO3)3 and MeCN, gave the lower oxidation state product [BiMnIII10O8(O2CPh)17(HO2CPh)(H2O)] (3). Complexes 1 and 2 are near-isostructural and possess an unusual and high symmetry core topology consisting of a MnIV6 wheel with two central BiIII atoms capping the wheel on each side. In contrast, the [BiMnIII10O8]17+ core of 3 is low symmetry, comprising a [BiMn3(μ3-O)2]8+ butterfly unit, four [BiMn3(μ4-O)]10+ tetrahedra, and two [BiMn2(μ3-O)]7+ triangles all fused together by sharing common Mn and Bi vertices. Variable-temperature, solid-state dc and ac magnetization data on 1–3 in the 1.8–300 K range revealed that 1 and 2 possess an S = 0 ground state spin, whereas 3 possesses an S = 2 ground state. The work offers the possibility of access to molecular analogs of the multifunctional Bi/Mn/O solids that are of such great interest in materials science

{Mn₆}_<i>n</i> Single-Chain Magnet Bearing Azides and Di-2-pyridylketone-Derived Ligands

The synthesis, structure, and magnetochemical characterization of a new manganese single-chain magnet are reported. The compound is a chain of repeating Mn6 units bridged by end-on azide groups and exhibits magnetization hysteresis loops

Employment of 2,6-Diacetylpyridine Dioxime as a New Route to High Nuclearity Metal Clusters: Mn₆ and Mn₈ Complexes

The employment of the anion of 2,6-diacetylpyridine dioxime (dapdoH2) as a pentadentate chelate in transition metal cluster chemistry is reported. The syntheses, crystal structures, and magnetochemical characterization are described for [Mn6O2(OMe)2(dapdo)2(dapdoH)4](ClO4)2 (1), [Mn6O2(OMe)2(dapdo)2(dapdoH)4][Ca(NO3)4] (2), and [Mn8O4(OH)4(OMe)2(N3)2(dapdo)2(dapdoH)2(H2O)2] (3). The reaction of [Mn3O(O2CMe)6(py)3](ClO4) with 3 equiv of dapdoH2 (with or without 2 equiv of NEt3) in MeOH gave 1. The same cation, but with a [Ca(NO3)4]2- anion, was found in complex 2, which was obtained from the reaction in MeOH between Mn(NO3)2, Ca(NO3)2, and dapdoH2 in the presence of NEt3. In contrast, addition of NaN3 to several reactions comprising MnCl2, dapdoH2, and NEt3 in MeOH gave the octanuclear complex 3. Complexes 1−3 all possess rare topologies and are mixed-valence:  2MnII, 4MnIII for 1 and 2, and 2MnII, 6MnIII for 3. The core of the cation of 1 and 2 consists of two edge-sharing Mn4 tetrahedra at the center of each of which is a μ4-O2- ion. Peripheral ligation is provided by two μ-OMe-, four μ-dapdoH-, and two μ3-dapdo2- groups. The core of 3 consists of two [MnIIMnIII3(μ3-O)2]7+ “butterfly” units linked together by one of the μ3-O2- ions, which thus becomes μ4. Peripheral ligation is provided by four μ-OMe-, two μ-OH-, two μ-dapdoH-, and two μ4-dapdo2- groups. Variable-temperature, solid-state dc and ac magnetization studies were carried out on complexes 1−3 in the 5.0−300 K range; the data for 1 and 2 are identical. Fitting of the obtained magnetization versus field (H) and temperature (T) data by matrix diagonalization and including only axial anisotropy (zero-field splitting, D) established that 1 possesses an S = 5 ground state with D = −0.24 cm-1. For 3, low-lying excited states precluded obtaining a good fit from the magnetization data, and the ground state was instead determined from the ac data, which indicated an S = 1 ground state for 3. The combined work demonstrates the ligating flexibility of pyridyl-dioxime chelates and their usefulness in the synthesis of new polynuclear Mnx clusters without requiring the co-presence of carboxylate ligands

Employment of 2,6-Diacetylpyridine Dioxime as a New Route to High Nuclearity Metal Clusters: Mn₆ and Mn₈ Complexes

The employment of the anion of 2,6-diacetylpyridine dioxime (dapdoH2) as a pentadentate chelate in transition metal cluster chemistry is reported. The syntheses, crystal structures, and magnetochemical characterization are described for [Mn6O2(OMe)2(dapdo)2(dapdoH)4](ClO4)2 (1), [Mn6O2(OMe)2(dapdo)2(dapdoH)4][Ca(NO3)4] (2), and [Mn8O4(OH)4(OMe)2(N3)2(dapdo)2(dapdoH)2(H2O)2] (3). The reaction of [Mn3O(O2CMe)6(py)3](ClO4) with 3 equiv of dapdoH2 (with or without 2 equiv of NEt3) in MeOH gave 1. The same cation, but with a [Ca(NO3)4]2- anion, was found in complex 2, which was obtained from the reaction in MeOH between Mn(NO3)2, Ca(NO3)2, and dapdoH2 in the presence of NEt3. In contrast, addition of NaN3 to several reactions comprising MnCl2, dapdoH2, and NEt3 in MeOH gave the octanuclear complex 3. Complexes 1−3 all possess rare topologies and are mixed-valence:  2MnII, 4MnIII for 1 and 2, and 2MnII, 6MnIII for 3. The core of the cation of 1 and 2 consists of two edge-sharing Mn4 tetrahedra at the center of each of which is a μ4-O2- ion. Peripheral ligation is provided by two μ-OMe-, four μ-dapdoH-, and two μ3-dapdo2- groups. The core of 3 consists of two [MnIIMnIII3(μ3-O)2]7+ “butterfly” units linked together by one of the μ3-O2- ions, which thus becomes μ4. Peripheral ligation is provided by four μ-OMe-, two μ-OH-, two μ-dapdoH-, and two μ4-dapdo2- groups. Variable-temperature, solid-state dc and ac magnetization studies were carried out on complexes 1−3 in the 5.0−300 K range; the data for 1 and 2 are identical. Fitting of the obtained magnetization versus field (H) and temperature (T) data by matrix diagonalization and including only axial anisotropy (zero-field splitting, D) established that 1 possesses an S = 5 ground state with D = −0.24 cm-1. For 3, low-lying excited states precluded obtaining a good fit from the magnetization data, and the ground state was instead determined from the ac data, which indicated an S = 1 ground state for 3. The combined work demonstrates the ligating flexibility of pyridyl-dioxime chelates and their usefulness in the synthesis of new polynuclear Mnx clusters without requiring the co-presence of carboxylate ligands

Initial Use of Dioximate Ligands in 3d/4f Cluster Chemistry: Synthesis, Structure, and Magnetic Studies of an Unusual [Gd^III₂Mn^IVO]⁸⁺ Complex

An unusual [MnIVGdIII2(μ3-O2−)]8+ triangular complex has been prepared from the initial use of 2,6-diacetylpyridine dioxime (dapdoH2) in 3d/4f cluster chemistry. The complex has an S = 13/2 ground state, with exchange parameters J = +0.49 cm−1 and J′ = −0.12 cm−1 [ℋ = −2J(Ŝi·Ŝj) convention] for the GdIII···MnIV and GdIII···GdIII interactions, respectively. The origin of this ground state has been rationalized by consideration of the spin frustration occurring within the complex as a function of the relative magnitude of the competing interactions

{Mn₆}_<i>n</i> Single-Chain Magnet Bearing Azides and Di-2-pyridylketone-Derived Ligands

The synthesis, structure, and magnetochemical characterization of a new manganese single-chain magnet are reported. The compound is a chain of repeating Mn6 units bridged by end-on azide groups and exhibits magnetization hysteresis loops

A Nontwisted, Ferromagnetically Coupled Mn^III₃O Triangular Complex from the Use of 2,6-Bis(hydroxymethyl)-<i>p</i>-cresol

The reaction between Mn(O2CMe)2·4H2O and hmcH3 [hmcH3 = 2,6-bis(hydroxymethyl)-p-cresol] in CH2Cl2 in the presence of NEt3 affords the MnIII3 complex [NEt3(CH2Cl)]2[Mn3O(hmcH)3(hmcH2)3] (1). The anion of 1 contains a [MnIII3(μ3-O)]7+ triangular core, with the central O2− ion lying above the Mn3 plane. The complex is ferromagnetically coupled with a resulting S = 6 ground state

Molecular Wheels as Nanoporous Materials: Differing Modes of Gas Diffusion through Ga₁₀ and Ga₁₈ Wheels Probed by Hyperpolarized ¹²⁹Xe NMR Spectroscopy

The study of crystals of molecular wheels as nanoporous materials is reported. Hyperpolarized 129Xe NMR spectroscopy has been used to characterize the mode of molecular diffusion and Xe interactions within the supramolecular nanochannels formed upon crystallization of the molecular wheels [Ga10(OMe)20(O2CMe)10] and [Ga18(pd)12(pdH)12(O2CMe)6(NO3)6](NO3)6. In agreement with expectations based on the collision diameter of the Xe atom relative to the differing internal diameters of the two types of gallium wheels, single-file diffusion occurs in the Ga10 channels, whereas in the Ga18 system the data are consistent with normal, Fickian diffusion. Information about the electronic environment inside the channels was probed by the Xe chemical shift. The interaction of the gas with the channel walls is found to be substantially stronger than the interaction in organic nanotubes and zeolites. The results establish the ability of crystals of molecular wheel compounds to function as a new class of porous nanotubular materials, and ones of a known and variable diameter, for studying the channel diameter dependence of molecular exchange and unidirectional diffusion on the micrometer length scale

Initial Use of Dioximate Ligands in 3d/4f Cluster Chemistry: Synthesis, Structure, and Magnetic Studies of an Unusual [Gd^III₂Mn^IVO]⁸⁺ Complex

An unusual [MnIVGdIII2(μ3-O2−)]8+ triangular complex has been prepared from the initial use of 2,6-diacetylpyridine dioxime (dapdoH2) in 3d/4f cluster chemistry. The complex has an S = 13/2 ground state, with exchange parameters J = +0.49 cm−1 and J′ = −0.12 cm−1 [ℋ = −2J(Ŝi·Ŝj) convention] for the GdIII···MnIV and GdIII···GdIII interactions, respectively. The origin of this ground state has been rationalized by consideration of the spin frustration occurring within the complex as a function of the relative magnitude of the competing interactions