Trinuclear Manganese Research Articles

Mononuclear Manganese(III) Complexes as Building Blocks for the Design of Trinuclear Manganese Clusters: Study of the Ligand Influence on the Magnetic Properties of the [Mn3(μ3-O)]7+ Core

Mononuclear Manganese(III) Complexes as Building Blocks for the Design of Trinuclear Manganese Clusters: Study of the Ligand Influence on the Magnetic Properties of the [Mn₃(μ₃-O)]⁷⁺ Core

A [MnIII3O]7+Single-Molecule Magnet: the Anisotropy Barrier Enhanced by Structural Distortion

A trinuclear manganese complex, [Mn 3O(Me-salox) 3(2,4'-bpy) 3(ClO 4)].0.5MeCN ( 1.0.5MeCN; Me-H 2salox = 2-hydroxyphenylethanone oxime), has been synthesized and characterized structurally as a [Mn (III) 3(mu 3-O)] (7+) core. Structural distortion by the twisting of the oxime ligand dominates ferromagnetic interactions within three Mn ions to give an S = 6 ground state as well as to enhance the anisotropy barrier U eff to 37.5 K.

Structure and magnetism of a linear trimanganese (III, II, III) complex based on benzoate and Schiff-base ligands

Reaction of [Mn3O(PhCO2)6(py)2(H2O)] with a tridentate Schiff-base 2-salicylideneaminoethanol (H2sae) affords a trinuclear manganese complex [Mn3(PhCO2)4(sae)2] (1). X-ray structural analysis of 1 reveals that three manganese ions are linear with each pair bridged by two benzoate groups and one μ-alkoxo oxygen of the sae2− ligand. The central manganese has an octahedral {MnIIO6} configuration and the terminal ones are five-coordinate {MnIIINO4} with a Jahn-Teller elongation axis. The trinuclear complex shows small antiferromagnetic exchange J coupling. The magnetic susceptibility data in the temperature range 2–300 K give the best fitting parameters with J = −8.44 cm–1, g = 2.02, zJ ′ = −0.34 cm–1, and R 2 = 0.99942. The magnetization versus external magnetic field measurements at 2 K proved that the ground state is S = 3/2.

Manganese and Cadmium Benzoate Complexes Having 8-Aminoquinoline Ancillary Ligand

Simple synthetic methods for synthesis of trinuclear manganese(II) benzoate complexes having 8aminoquinoline as ancillary ligand are reported. The crystal structure of two trinuclear manganese(II) complexes, [Mn3(2NO2C6H4COO)6(AQ)2] (I) and [Mn3(3-CH3C6H4COO)6(AQ)2].NPD (II) is reported (where AQ = 8-aminoquinoline, NPD = 1,5 dihydroxynaphthalene). In solution, the degradation of trinuclear complex I leads to a dinuclear complex [Mn2(2NO2C6H4COO)4(AQ)2 (H2O)2] (III) and structure of complex III is reported. A solution phase synthetic method for the synthesis of the dinuclear manganese(II) complex III is also reported. This complex has a Mn2O2 bridge originating from the carboxylate ligand. Synthesis of a cadmium 2-nitrobenzoate co-ordination polymer [Cd(2-NO2C6H4COO)2(AQ)]n (IV) having eight co-ordination number is reported and its structure is explained as aggregation of multiple numbers of six coordinated mononuclear cadmium complexes.

Synthesis, characterization and crystal structure of a new linear trinuclear manganese(II) complex, [Mn3(PhCH=CHCO2)6(BPY)2] · H2O (BPY=2,2-bipyridine)

A new trinuclear manganese(II) complex, [Mn3(PhCH=CHCO2)6(bpy)2] · H2O (1) (bpy = 2,2-bipyridine), was synthesized by the reaction of Mn(OH)2 with cinnamate in H2O/methanolic solution and its solid state structure was determined by single crystal X-ray diffraction. Structural analyses suggest that 1 consists of a linear arrangement of three Mn(II) centers, bridged by six cinnamate carboxylate groups. Four of these carboxylates are syn–syn bidentate, and two are monodentate bridging plus bidentate chelating. Mn(2) on a crystallographic inversion center has a slightly disorted octahedral geometry; the terminal six-coordinate Mn(1) atoms are significantly distorted octahedra. Weak intermolecular interactions such as C–H ··· O hydrogen-bonding and π–π stacking are responsible for supramolecular assembly of the molecules. Compound 1 was characterized by infrared spectrum, thermogravimetric and X-ray powder diffraction analyses.

Tripodal Trimanganese(III) Complexes of New Unsymmetrical Pentadentate Ligands Derived from 2‐(Salicylideneamino)phenol: Syntheses, Crystal Structures and Properties

AbstractTrinuclear manganese(III) complexes of new unsymmetrical pentadentate ligands, 6‐hydroxy‐2‐(2‐hydroxyphenyl)‐5‐(salicylideneamino)benzoxazole (H3L1) and 5‐(5,6‐benzosalicylideneamino)‐6‐hydroxy‐2‐(2‐hydroxynaphthyl)benzoxazole (H3L2), [Mn3(L1)3(CH3OH)3] (1) and [Mn3(L2)3(dmf)(CH3OH)(H2O)] (2) (dmf = N,N‐dimethylformamide), have been prepared. The structures of the ligands H3L1, H3L2 and complex 1 were determined by X‐ray crystallography, which revealed that the ligands have two distant chelating sites. The molecular structure of 1 is regarded as a tripodal pyramid with a cavity of about 3 Å diameter. Each MnIII ion is coordinated by ONO atoms from a tridentate Schiff base site and ON atoms from a benzoxazole site of two respective H3L1 ligands. The intramolecular Mn···Mn distances for 1 are in the range 8.0683–8.1791 Å, and the nearest intermolecular Mn···Mn distance, 5.7824(15) Å, is shorter than theintramolecular values. Magnetic measurements of 1 indicate that weak antiferromagnetic interactions (J = –0.2 cm–1, g = 2.0) are dominant in the trinuclear manganese(III) core. Cyclic voltammogram of 1 in dmf showed obscure redox couples assigned to two single‐electron transfer processes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Synthesis, solid-state and in-solution structures of a new seven coordinated manganese(II) complex via X-ray diffraction and electrospray ionization mass spectrometry

The structure of the [Mn(HPClNOL)(η 1-NO 3)(η 2-NO 3)] 1 complex [HPClNOL = 1-(bis-pyridin-2-ylmethyl-amino)-3-chloropropan-2-ol] in the solid-state and in H 2O/MeOH solution was investigated by monocrystal X-ray diffraction and ESI(+)–MS/MS. X-ray reveals that 1 is a seven-coordinated complex with a discrete mononuclear structure in which the manganese(II) ion is coordinated by the tripodal HPClNOL ligand and two nitrate ions, one monodentate and the other bidentate. ESI(+)–MS/MS shows that mononuclear, dinuclear and trinuclear manganese cationic species are present in solution, probably in equilibrium with neutral 1. This contrasting scenario illustrates for 1 the importance of both solid-state and in-solution characterizations of coordination compounds with potential bioinorganic interest.

The first trinuclear manganese triplesalen complex: Synthesis, structural, and magnetic characterization of [(talenNO2){MnIII(DMSO)2}3](ClO4)3

The reaction of the nitro-substituted triplesalen ligand H(6)talen(NO2) with Mn(ClO4)(2)center dot 6H(2)O in CH3CN in the presence of Et3N and DMSO results in the formation of [(talen(NO2)){Mn-III(DMSO)(2)}(3)](ClO4)(3) (1) which has been characterized by elemental analysis, FTIR, UV-vis-NIR, ESI-MS, single-crystal X-ray diffraction, and magnetic measurements. The triplesalen ligand (talen(NO2))(6-) provides three salen-like coordination environments bridged in a meta-phenylene arrangement by a phloroglucinol backbone. The coordination environment of each Mn-III ion is completed by two O-bonded DMSO molecules. The folding of the triplesaten ligand results in an overall dish-like geometry for the trication in 1. The magnetic characterization has been performed by temperature dependent magnetic susceptibility measurements and variable temperature-variable field (VTVH) magnetization data in order to determine both the exchange couplings J between the S-i = 2 ion and the local zero-field splittings D-i. Simulations to the appropriate spin-Hamiltonian using a full-matrix diagonalization approach provided a weak antiferromagnetic interaction J = -0.30 +/- 0.05 cm(-1) but a strong magnetic anisotropy expressed by D = -4.0 +/- 0.4 cm(-1). The potential applications of 1 and forthcoming members of this new family of trinuclear manganese triplesalen complexes in molecule-based magnetism and homogenous catalysis are discussed.

Novel Trinuclear MnII/MnII/MnII Complexes – Crystal Structures and Catalytic Properties

AbstractThe trinuclear manganese(II) complexes [Mn3(L1)2(μ‐OAc)4]·2Et2O {HL1 = (1‐hydroxy‐4‐nitrobenzyl)((2‐pyridyl)methyl)((1‐methylimidazol‐2‐yl)methyl)amine} (1·2EtOH), [Mn3(L2)2(μ‐OAc)4] {HL2 = ((1‐methylimidazol‐2‐yl)methyl)(1‐hydroxybenzyl)amine} (2) and [Mn3(L3)2(μ‐OAc)6] {L3 = bis(1‐methylimidazol‐2‐yl)methanone} (3) were synthesized. The compounds were characterized by X‐ray crystallography, mass spectrometry, IR, UV‐vis spectroscopy, and elemental analysis. The manganese atoms in 1 and 2 are bridged by phenol moieties of the ligands and acetates. In 3 they are only bridged by acetates in a mono‐ and bi‐dentate way. The resulting Mn···Mn distances are 3.233(1) Å (1), 3.364(1) Å (2) and 3.643(7) Å (3). In the present compounds different limiting cases for the phenomenon of the carboxylate shift are realized. Besides symmetric mono‐ and bi‐dentate bridging an unusual intermediate is also observed. 1·2EtOH is the first example of a trinuclear model for the OEC that shows catalase activity. Furthermore it was characterized by temperature dependent magnetic susceptibility measurements and a total spin ground state of St = 5/2 was found. The results for 1 reveals antiferromagnetic coupling between the central and the terminal manganese ions, with J = −1.2 cm−1, g = 2.00 (fixed), χTIP = 150×10−6 cm3mol−1.

Synthesis, Structure and Properties of a Linear Trinuclear Manganese(III/II/III) Complex

A new mixed‐valence trinuclear manganese(III/II/III) complex was synthesized by ethanolamine and paeonol in the presence of Mn(acetato)2·4H2O. The crystal of the complex was characterized by X‐ray diffraction, IR, UV spectroscopy, molar conductivity and elemental analyses. The structurally characterized mixed‐valence complex has strictly 180° MnIII‐ MnII‐ MnIII angle as required by crystallographic inversion symmetry. The Mn(1) … Mn(2)#1 separation is 3.0500(8) Å. Antimicrobial activity study found that the complex was active against Salmonella species, Staphylococcus aureus, Bacillus pumilus and Eschierichia coli.

Trimanganese Complexes Bearing Bidentate Nitrogen Ligands as a Highly Efficient Catalyst Precursor in the Epoxidation of Alkenes

A series of trinuclear manganese complexes coordinated with neutral bidentate nitrogen ligands, [Mn3L2(OAc)6], were prepared from manganese acetate and the corresponding ligands. Using peracetic acid as the oxidant, the air- and moisture-stable manganese clusters exhibited excellent catalytic activity and selectivity in the epoxidation of olefins under mild conditions. The highest activity was observed with a trinuclear complex containing a 2-pyridylimino ligand, [Mn3(ppei)2(OAc)6] (ppei = 2-pyridinal-1-phenylethylimine). With this system, the substrate scope was extremely wide to include terminal and electron-deficient double bonds of both aliphatic and aromatic alkenes. The high activity was undiminished under the reaction conditions even directly using a mixture of the pyridylimino ligands and manganese acetates, making this process more convenient. It was also observed that analogous trinuclear complexes, such as [Mn3(bipy)2(OAc)6] and [Mn3(phen)2(OAc)6], displayed excellent activities. While radical intermediacy was inferred from the product distribution, kinetic data revealed that the epoxidation is roughly first-order in manganese cluster precursor and oxidant, respectively, and zero-order in olefin. These results led us to propose that the trinuclear complexes [Mn3L2(OAc)6] serve as catalyst precursors that dissociate into monomeric species with the formulation of [MnL2(OAc)2] under the reaction conditions.

Synthesis, crystal structures and magnetic properties of trinuclear oxo-centered homo- and mixed-valence manganese pivalate complexes with imidazole (Im) and 1-methylimidazole (1-MeIm): [formula omitted] and [formula omitted

Two new μ 3-oxo-centered trinuclear manganese complexes, one of them a homo-valence [ Mn 3 III O ( O 2 CCMe 3 ) 6 ( Im ) 3 ] ( Me 3 CCO 2 ) · 0.5 Me 3 CCO 2 H ( 1) pivalate complex and the other a mixed-valence [ Mn 2 III Mn II O ( O 2 CCMe 3 ) 6 ( 1 -MeIm ) 3 ] ( 2) pivalate complex (where Im = imidazole, 1-MeIm = 1-methylimidazole), have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, X-ray crystallography and magnetochemistry. Complexes 1 and 2 are μ 3-oxo-trinuclear compounds with the three manganese atoms bridged by six pivalate groups. At each axial position there is an Im ( 1) or 1-MeIm ( 2) molecule. In both compounds, the manganese coordination geometry is slightly distorted octahedral, consisting of the oxygen of the central triangle, four oxygen atoms from bridging pivalate ligands, and a terminal Im or 1-MeIm nitrogen atom. The crystal packing of 1 involves hydrogen bonding between complex cations [Mn 3O(Piv) 6(Im) 3] + and outersphere pivalate ions, whereas in compound 2 interactions of the C–H⋯π type, formed by both the aromatic and methyl C–H groups of 1-MeIm molecules, are present. Magnetic studies reveal that both compounds represent antiferromagnetically coupled, spin-frustrated triangular systems exhibiting weak to moderate exchange coupling constants.

Linear trinuclear manganese(II) complexes: crystal structures and magnetic properties

Two new trinuclear manganese(II) complexes, [Mn 3(O 2CCH(CH 3) 2) 6(N–N) 2] (N–N is 1,10′-phenanthroline ( 1) and 2,2′-bipyridine ( 2)) have been prepared and fully characterized. Single crystal X-ray diffraction analysis confirmed a linear arrangement of three Mn(II) centers bridged by six isobutyric carboxylate groups. The magnetic measurements showed that both complexes exhibit an S T = 5/2 spin ground state induced by antiferromagnetic interactions between the Mn(II) sites: J/k B = −2.31(2) and −2.67(2) K for 1 and 2, respectively.

Antiferromagnetic order in a supramolecular assembly of manganese trimers based on imidazole and Schiff-base ligands

A new trinuclear manganese cluster, [Mn 3(O 2CCH 3) 4(sae) 2(HIm) 2] ( 1) (H 2sae = 2-salicylideneaminoethanol, HIm = imidazole), has been prepared. Single crystal X-ray diffraction analysis reveals an interesting one-dimensional supramolecular arrangement of the [Mn 3(O 2CCH 3) 4(sae) 2(HIm) 2] trimers induced by HIm axial ligands and hydrogen bonding interactions. The magnetic measurements show that trimer units in 1 exhibit an S T = 3/2 ground state and order antiferromagnetically below 0.37 K.

A Novel One‐Dimensional Chain Complex Composed of Oxo‐Centered Trinuclear Manganese Clusters

AbstractA new linear chain complex of oxo‐centered trinuclear manganese clusters, [{MnIII2MnIIO(O2CCHCl2)6(H2O)}{Mn(O2CCHCl2)2(H2O)4}]n (1), has been synthesized by treatment of a mixture of Mn(OAc)2·4H2O and dichloroacetic acid in dichloromethane with KMnO4. In this complex chains are formed by hydrogen bonding between carboxylate oxygens and coordinated water molecules, forming a two‐dimensional structure. Antiferromagnetic coupling was observed by variable‐temperature magnetic measurements. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Magnetic properties and spin dynamics in magnetic molecule {Mn3}

We report dc magnetization and nuclear magnetic resonance (NMR) measurements in a trinuclear manganese compound, {Mn3}, with formula [Mn3O(O2CCH3)6(C5H5N)3]⋅C5H5N. The magnetic properties are characterized by two antiferromagnetic (AF) coupling constants, J=−7.9 K and J′=−27.6 K. H1 NMR linewidth strongly depends on both the magnetic field and temperature, and is quantitatively explained by the dipolar interaction between proton nuclei and Mn ion spins. The strong enhancement of T1−1 at low temperatures is ascribed to the slowing down of magnetic fluctuations resulting from building up of AF correlations. From the T dependence of T1−1 at low T, we obtained the gap ΔNMR=19 K, in qualitative agreement with the gap Δ≅12 K obtained from susceptibility χ.

Synthesis and Characterization of [Mn3(ppi)2(μ‐OAc)4(H2O)2] · 2MeOH — Unusual Structural Properties of a Trinuclear Oxygen‐Rich Manganese Complex

AbstractThe trinuclear manganese(II) complex [Mn3(ppi)2(μ‐OAc)4(H2O)2]·2MeOH (1) (Hppi = 2‐pyridylmethyl‐2‐hydroxyphenylimine) is prepared by dissolving two equivalents of Hppi (from the Schiff Base reaction of aminophenol and pyridine‐2‐carboxaldehyde) in acetonitrile and three equivalents of Mn(OAc)2·4H2O in methanol and combining both solutions. The resulting red precipitate was recrystallized to yield red crystals suitable for single crystal X‐ray diffraction. Compound 1 crystallizes in the triclinic space group P1¯ (no. 2), with a = 9.691(2), b = 10.683(2), c = 11.541(2)Å, α = 63.19(3)°, β = 67.47(3)°, γ = 69.11(3)°, V = 960.2(3)Å3, and Z = 1. The binding mode of carboxylate in 1 represents a model for a transition state between symmetric syn, syn, anti‐μ2‐carboxolato‐O‐ and syn, anti‐μ2‐carboxylato‐O, O′‐coordination. Therefore a rare binding mode for the phenomenon of the carboxylate shift is realized. Furthermore the complex is stabilized by a distinctive hydrogen bonding pathway.

Preparation and structures of trinuclear manganese(II) complexes with N-2-pyridiylmethylidene-2-hydroxy-5-substituted-phenylamine

The trinuclear manganese(II) complexes, [Mn II 3(OAc) 4(pap) 2(H 2O) 2] and [Mn II 3(OAc) 4(5-Cl-pap) 2(MeOH) 2] were prepared by the reaction of tridentate Schiff base ligands X-papH (X=H, Cl), [ N-2-pyridiylmethylidene-2-hydroxy-5-substituted-phenylamine], and Mn II(OAc) 2·2H 2O. In the molecular structures of these complexes, two terminal manganese ions are coordinated with one oxygen and two nitrogen atoms of X-pap, two oxygen atoms of OAc − and a solvent molecule, to form a distorted octahedral structure where the central manganese ion resides on a center of symmetry and is surrounded by an O 6 donor set of four oxygen atoms from four bridging OAc − and two phenolic oxygen atoms of two X-pap ligands.

Cobalt(II) and manganese(II) complexes of unsymmetric compartmental ligands bearing adjacent {N 2O} and {N,S,O} donor sets

The crystal structures of the dinuclear cobalt(II) complex, [ Co 2( L 5)( OAc)( NCS) 2( CH 3 OH) ], and the trinuclear manganese(II) complex, [ Mn 3( L 7) 2( OAc) 2( NCS) 2 ], are reported.

Novel Mixed-Valence μ-Oxo-Bridged Trinuclear Manganese Complexes [Mn3O(O2CR)6L3] (R=4-Cl-C6H4OCH2, 3-Cl-C6H5, BrCH2, L=3-Methylpyridine or Water): Structures and Magnetic Properties

Preparation of three new mixed-valence oxo-centered trinuclear manganese complexes [Mn3O(O2CR)6L3] (R=4-Cl-C6H4OCH2, 1, 3-Cl-C6H5, 2, BrCH2, 3; L=3-methylpyridine or water), by reaction of N-n-Bu4MnO4 with appropriate reagents in ethanol and 3-methelpyridine is reported. The crystal structure of 1 has shown to have an oxo-centered Mn3O unit with peripheral ligands provided by bridging carboxylate and terminal 3-methylpyridine groups, and with an approximate 3-fold symmetry axis for the whole cluster. Variable temperature magnetic susceptibilities of the complexes in the range 1.5-300 K have been measured and are interpreted in terms of the Kambe vector-coupling method and Van Vleck equation; J (cm−1), J' (cm−1), g, and R parameters obtained are -8.2, -10.9, 2.04, 2.15 x 10−3 (1); -7.3, -11.1, 2.20, 3.32 x 10−3 (2); -2.1, -4.1, 1.97, 2.34 x 10−3 (3). There is weak antiferromagnetic exchange between manganese ions. Effects of bridging and terminal ligands on the J, J' values and spin ground state are discussed.