Constructing octa- and hexadecanuclear manganese clusters from tetrahedral MnIII3MnII cores bridged by quinquedentate Schiff base and versatile azide groups

Chiral Versus Non-Chiral [MnIII 6 MnII NaI ], [MnIII 6 MnII 2 NaI 2 ] and [MnIII 3 MnII NaI ] Clusters Derived from Schiff Bases or the Fight for Symmetry

The reaction in basic media of manganese chloride with Schiff bases derived from the condensation of o-vanillin with different chiral/racemic aminoalcohols yielded in a family of complexes in which the nuclearity, symmetry and magnetic behavior is controlled by changing the position of the chiral carbon. Chiral and racemic clusters with [Mn^III ₆ Mn^II Na^I ], [Mn^III ₆ Mn^II ₂ Na^I ₂ ] and [Mn^III ₃ Mn^II Na^I ] metallic core have been structurally and magnetically characterized. The racemic clusters with an odd number of chiral ligands exhibit the anomalous mixing of ligands with different conformation. Related racemic compounds have been reviewed.

Hexadecanuclear MnII2MnIII14 Molecular Torus Built from in Situ Tandem Ligand Transformations

A mixed-valent hexadecanuclear manganese cluster, [Mn^II₂Mn^III₁₄(trz)₁₄(thetach)₄(μ₃-O)₈(H₂O)₁₀](ClO₄)₆ (Mn16), containing two Mn^II and 14 Mn^III ions, is constructed from mixed in situ generated ligands, 1,2,3-triazole (Htrz) and 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane (H₃thetach). Remarkably, both ligands were not initially added into the reaction system, and their formations involve the in situ ligand decomposition and subsequent condensation reactions. The core of Mn16 is an elongated torus comprised of eight Mn atoms and four [Mn₂O₂] subunits bridged by oxo or alkoxide. The high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) of Mn16 dissolved in CH₃CN indicates its structure remains intact as +3 and +4 species. Temperature and field dependent magnetization revealed predominantly antiferromagnetic exchange interactions within the cluster. The work provides one-pot synthesis of high-nuclearity manganese clusters using the ligands generated by in situ reactions in a tandem fashion.

A family of planar hexanuclear CoLn clusters with lucanidae-like arrangement and single-molecule magnet behavior

A family of planar hexanuclear CoLn clusters with the hydroxyl and nitrogen rich ligand 2-[bis(pyridin-2-ylmethyl) amino]-2-(hydroxymethyl)propane-1,3-diol (H₃L), formulated as [Co₄Ln₂(μ₃-O)₂(μ-N₃)₂(OH)₂(H₂O)₂(HL)₄]·(CH₃CO₂)₂·20H₂O [Ln = Dy (1), Gd (2), Tb (3), Eu (4) and Ho (5)], have been synthesized and structurally characterized. They are isomorphous and feature a lucanidae-like arrangement. They are the first examples of 3d-4f clusters with the H₃L ligand. In addition, the magnetic properties of 1-5 have been investigated and the single-molecule magnet (SMM) behaviour is observed for 1.

Tetramer Compound of Manganese Ions with Mixed Valence [MnII MnIII MnIV] and Its Spatial, Electronic, Magnetic, and Theoretical Studies

Using different spectroscopic techniques and computational calculations, we describe the structural and electromagnetic relationship that causes many interesting phenomena within a novel coordination compound with mixed valence manganese (II, III and IV) in its crystal and powder state. The novel compound [MnII MnIII MnIV(HL)2(H2L)2(H2O)4](NO3)2(H2O) 1 was obtained with the Schiff base (E)-2-((2-hydroxybenzylidene)amine)-2-(hydroximethyl)propane-1,3-diol, (H4L), and Mn(NO3)2.4H2O. The coordination reaction was promoted by the deprotonation of the ligand by the soft base triethylamine. The paper’s main contribution is the integration of the experimental and computational studies to explain the interesting magnetic behavior that the mixed valence manganese multimetallic core shows. The results presented herein, which are rarely found for Mn(II), (III) and (IV) complexes, will contribute to the understanding of the magnetic communication generated by the valence electrons and its repercussion in the local geometry and in the overall crystalline structure.

Solvent dependent reactivities of di-, tetra- and hexanuclear manganese complexes: syntheses, structures and magnetic properties

An unusual solvent effect on the synthesis of five manganese complexes [Mn2(L1)2(Py)4](), [Mn2(L1)2(DMSO)4](), [Mn4(L2)4(OH)4](), [Mn4(L3)2(DMSO)7(H2O)](), and [Mn6O2(L4)4(OAc)2(OMe)2(DMSO)4]·MeOH] (), (H3L1 = 5-(2-oxyphenyl)-pyrazole-3-carboxylic acid; H2L2 = 5-(2-oxyphenyl)-pyrazole-3-carboxylic acid amide; H4L3 = di-[5-(2-oxyphenyl)-pyrazole]-3-hydroxamic ether; and H2L4 = 5-(2-oxyphenyl)-pyrazole-3-carboxylic acid methyl ester) has been reported. Five complexes have been characterized by X-ray single crystal diffraction, IR, element analysis, thermogravimetric analysis and UV-vis spectra. The analysis reveals that complexes and are isostructural with a bimetallic six-membered ring and L1 from the decomposition of the original H4ppha (H4ppha = 5-(2-hydroxyphenyl)-pyrazole-3-hydroxamic acid) ligand. Complexes and are two tetranuclear clusters, and possesses an aza12-metallacrown-4 core with L2 from the amide functionalization of the decomposition L1; while represents a novel linear [Mn4N8O2] core with L3 from the condensation of L1 and H4ppha. Complex is the first Mn6 cluster linked by two stacked, off-set 8-azametallacrown-3 subunits with [M-N-N-M-N-N-M-O] connectivity, and L4 derived from the esterification of L1. The magnetic behaviour of complexes show the dominant antiferromagnetic interactions between metal centers, whereas complex further reveals the coexistence of antiferromagnetic and ferromagnetic interactions, and slow magnetic relaxation at T < 6 K with S = 4 ground state, as well as field induced magnetization saturation.

Switching nuclearity and Co(ii) content through stoichiometry adjustment: {CoII6CoIII3} and {CoIICo4III} mixed valent complexes and a study of their magnetic properties

Controlling the Co^II content in polynuclear systems: {Co^II₆Co^III₃} and {Co^IICo₄^III} mixed valent complexes with distinct magnetic behaviours is reported.

22-Azametallacrown-8 complex with a triazole-bridged ligand: synthesis, structure and magnetic properties

Reaction of Mn(OAc)2·4H2O with the H2L ligand affords a new manganese 22-MC-8 azametallacrown [Mn8(μ3-O)2(μ3-OH)2(μ2-OH)2(L)6(OAc)2(OH2)4]·2DMF (H2L = 3-(2-oxyphenyl)-5-(pyrazin-2-yl)-1,2,4-triazole). The structural analysis of the complex reveals that the azaMC ring possesses -[Mn-O-Mn-N-N-Mn-N-N-Mn-N-N]- connectivity. The magnetic behavior of the complex shows the dominant antiferromagnetic interactions between the manganese ions with S = 4 and the frequency-dependent out-of-phase signal.

Comproportionation reactions to manganese(III/IV) pivalate clusters: a new half-integer spin single-molecule magnet

The comproportionation reaction between Mn(II) and Mn(VII) reagents under acidic conditions has been investigated in the presence of pivalic acid as a route to new high oxidation state manganese pivalate clusters containing some Mn(IV). The reaction of Mn(O(2)CBu(t))(2) and NBu(n)(4)MnO(4) with an excess of pivalic acid in the presence of Mn(ClO(4))(2) and NBu(n)(4)Cl in hot MeCN led to the isolation of [Mn(8)O(6)(OH)(O(2)CBu(t))(9)Cl(3)(Bu(t)CO(2)H)(0.5)(MeCN)(0.5)] (1). In contrast, the reaction of Mn(NO(3))(2) and NBu(n)(4)MnO(4) in hot MeCN with an excess of pivalic acid gave a different octanuclear complex, [Mn(8)O(9)(O(2)CBu(t))(12)] (2). The latter reaction but with Mn(O(2)CBu(t))(2) in place of Mn(NO(3))(2), and in a MeCN/THF solvent medium, gave [Mn(9)O(7)(O(2)CBu(t))(13)(THF)(2)] (3). Complexes 1-3 possess rare or unprecedented Mn(x) topologies: 1 possesses a [Mn(III)(7)Mn(IV)(μ(3)-O)(4)(μ(4)-O)(2)(μ(3)-OH)(μ(4)-Cl)(μ(2)-Cl)](8+) core consisting of two body-fused Mn(4) butterfly units attached to the remaining Mn atoms via bridging O(2-), OH(-), and Cl(-) ions. In contrast, 2 possesses a [Mn(6)(IV)Mn(2)(III)(μ(3)-O)(6)(μ-O)(3)](12+) core consisting of two [Mn(3)O(4)] incomplete cubanes linked by their O(2-) ions to two Mn(III) atoms. The cores of 1 and 2 are unprecedented in Mn chemistry. The [Mn(III)(9)(μ(3)-O)(7)](13+) core of 3 also contains two body-fused Mn(4) butterfly units, but they are linked to the remaining Mn atoms in a different manner than in 1. Solid-state direct current (dc) and/or alternating current (ac) magnetic susceptibility data established S = (15)/(2), S = 2, and S = 1 ground states for 1·MeCN, 2·(1)/(4)MeCN, and 3, respectively. The ac susceptibility data also revealed nonzero, frequency-dependent out-of-phase (χ″(M)) signals for 1·MeCN at temperatures below 3 K, suggesting possible single-molecule magnet behavior, which was confirmed by single-crystal magnetization vs dc field scans that exhibited hysteresis loops. The combined work thus demonstrates the continuing potential of comproportionation reactions for isolating high oxidation state Mn(x) clusters, and the sensitivity of the product identity to minor changes in the reaction conditions.

Tetra-μ(2)-acetato-diaqua-bis-(μ(2)-2-{[1,3-dihy-droxy-2-(oxidometh-yl)propan-2-yl]imino-meth-yl}phenolato)trimanganese(II,III) acetonitrile disolvate dihydrate

In the title complex, [Mn^IIMn^III₂(C₁₁H₁₃NO₄)₂(CH₃CO₂)₄(H₂O)₂]·2CH₃CN·2H₂O, there are two Mn^III and one Mn^II atoms. The Mn^II atom lies on an inversion center and the Mn^III—Mn^II—Mn^III angle is therefore 180°, as required by crystallographic symmetry. The Mn^III and Mn^II atoms are six-coordinated in a distorted octa­hedral geometry. In the crystal, complex mol­ecules and solvent mol­ecules are linked into a three-dimensional network by O—H⋯O and O—H⋯N hydrogen-bonding inter­actions.