MnII Atom Research Articles

Single-Molecule Magnets: A Family of MnIII/CeIV Complexes with a [Mn8CeO8]12+ Core

Four heterometallic, enneanuclear Mn8Ce clusters [Mn8CeO8(O2CMe)12(H2O)4] (4), [Mn8CeO8(O2CMe)12(py)4] (5), [Mn8CeO8(O2CPh)12(MeCN)4] [Mn8CeO8(O2CPh)12(dioxane)4] (6), and [Mn8CeO8(O2CCHPh2)12(H2O)4] (7) have been prepared by various methods. Their cores are essentially isostructural and comprise a nonplanar, saddlelike [MnIII8O8]8+ loop containing a central CeIV ion attached to the eight micro3-O2- ions. Peripheral ligation around the [Mn8CeO8]12+ core is provided by eight micro- and four micro3-O2CR- groups. Terminal ligation on four MnIII atoms is provided by H2O in 4 and 7, pyridine in 5, and MeCN/dioxane in 6. Solid-state magnetic susceptibility studies, fits of dc magnetization vs field and temperature data, and in-phase ac susceptibility studies in a zero dc field have established that complexes 4, 5, and 7 possess S=16, S=4 or 5, and S=6+/-1 spin ground states, respectively, but in all cases there are very low-lying excited states. The large variation in the ground-state spins for this isostructural family is rationalized as due to a combination of weak exchange interactions between the constituent MnIII atoms, and the presence of both nearest-neighbor and next-nearest-interactions of comparable magnitudes. Magnetization vs applied dc field sweeps on single crystals of 4.4H2O and 7.4H2O.3MeCN.2CH2Cl2 down to 0.04 K have established that these two complexes are new single-molecule magnets (SMMs). The former also shows an exchange-bias, a perturbation of its single-molecule properties from very weak intermolecular interactions mediated by hydrogen-bonding interactions with lattice-water molecules of crystallization.

Poly[[bis[μ2-8-ethyl-5-oxo-2-(piperazin-1-yl)-5,8-dihydropyrido[2,3-d]pyrimidine-6-carboxylato]manganese(II)] dihydrate

In the title compound, {[Mn(C14H16N5O3)2]·2H2O}n, the MnII atom (site symmetry ) exhibits a distorted trans-MnN2O4 octa­hedral geometry defined by two monodentate N-bonded and two bidentate O,O′-bonded 8-ethyl-5-oxo-2-(piperazin-1-yl)-5,8-dihydro­pyrido[2,3-d]pyrimidine-6-carboxyl­ate anions. An N—H⋯O hydrogen bond is present in the crystal structure. The extended two-dimensional structure is a square grid and the disordered uncoordinated water mol­ecules occupy cavities within the grid.

Bis{μ-2,2′-[ethane-1,2-diylbis(nitrilomethylidyne)]diphenolato}bis[(thiocyanato)manganese(III)

The reported structure is a monoclinic polymorph of the title compound, [Mn2(C16H14N2O2)2(NCS)2], which has been characterized previously in an ortho­rhom­bic form. Each MnIII atom is chelated by a tetra­dentate 2,2′-[ethane-1,2-diylbis(nitrilo­methyl­idyne)]diphenolate ligand and by the N atom of a thio­cyanate anion, in a square-pyramidal arrangement. The complexes form centrosymmetric dimers, with an Mn—O contact of 2.557 (3) Å trans to each thio­cyanate anion, completing a distorted octa­hedral coordination geometry.

Syntheses, Structures and Magnetic Properties of Two Mixed‐Valent Disc‐like Hepta‐nuclear Compounds of [FeIIFeIII6(tea)6](ClO4)2 and [MnII3MnIII4(nmdea)6(N3)6]·CH3OH (tea = N(CH2CH2O)33−, nmdea = CH3N(CH2CH2O)22−)

AbstractTwo mixed‐valent disc‐like hepta‐nuclear compounds of [FeIIFeIII6(tea)6](ClO4)2 (1Fe, tea = N(CH2CH2O)33−) and [MnII3MnIII4(nmdea)6(N3)6]·CH3OH (2Mn, nmdea = CH3N(CH2CH2O)22−) have been synthesized by the reaction of Fe(ClO4)2·6H2O with triethanolamine (H3tea) for the former and reaction of Mn(ClO4)2·6H2O with diethanolamine (H2nmdea) and NaN3 for the later, respectively. 1Fe has the cationic cluster with a planar [FeIIFeIII6] core consisting of one central FeII and six rim FeIII atoms in hexagonal arrangement. The Fe ions are linked by the oxo‐bridges from the alcohol arms in the manner of edge‐sharing of their coordination octahedra. 2Mn is a neutral cluster with a [MnII3MnIII4] core possessing one central MnII atom surrounded by six rim Mn ions, two MnII and four MnIII. The structure is similar to 1Fe but involves six terminal azido ligands, each coordinate one rim Mn ion. 1Fe showed dominant antiferromagnetic interaction within the cluster and long‐range ordering at 2.7 K. The cluster probably has a ground state of low spin of S = 5/2 or 4/2. The long‐range ordering is weak ferromagnetic, showing small hysteresis with a remnant magnetization of 0.3 Nβ and a coercive field of 40 Oe. Moreover, the isofield of lines 1Fe are far from superposition, indicating the presence of significant zero–field splitting. Ferromagnetic interactions are dominant in 2Mn. An intermediate spin ground state 25/2 is observed at low field. In high field of 50 kOe, the energetically lowest state is given by the ms = 31/2 component of the S = 31/2 multiplet due to the Zeeman effect. Despite of the large ground state, no single‐molecule magnet behavior was found above 2 K.

Diaquabis(4-chlorobenzoato-κO)bis(N,N-diethylnicotinamide-κN1)manganese(II)

The title compound, [Mn(C7H4ClO2)2(C10H14N2O)2(H2O)2], is a monomeric complex with the MnII atom lying on an inversion center. It contains two 4-chloro­benzoate and two diethyl­nicotinamide ligands and two water mol­ecules, all of which are monodentate. The four O atoms in the equatorial plane around the Mn atom form a slightly distorted square-planar arrangement, while the distorted octa­hedral geometry is completed by two N atoms in the axial positions. In the crystal structure, O—H⋯O hydrogen bonds link the mol­ecules into an infinite chain.

Oxalatobis(propane-1,3-diamine)manganese(II) chloride monohydrate

In the asymmetric unit of the title compound, [Mn(C2O4)(C3H10N2)2]Cl·H2O, there are two independent MnIII complexes, two Cl− anions and two uncoordinated water mol­ecules. Each MnIII atom is hexa­coordinated by four N atoms from two propane-1,3-diamine ligands and two O atoms from one oxalate ligand, resulting in a slightly distorted octa­hedral MnO2N4 geometry. Mn—O and Mn—N bond lengths are in the ranges 1.969 (2)–2.020 (3) and 2.068 (3)–2.113 (4) Å, respectively. There are weak inter­molecular O—H⋯O, O—H⋯Cl, N—H⋯O and N—H⋯Cl hydrogen bonds with D⋯A distances in the range 2.831 (4)–3.423 (3) Å.

Bis[6-(3,5-dimethyl-1H-pyrazol-1-yl)picolinato]manganese(II) trihydrate

In the title complex, [Mn(C11H10N3O2)2]·3H2O, the MnII atom is coordinated by four N atoms and two O atoms in a distorted octa­hedral geometry. The mol­ecules are linked together via hydrogen bonds involving the water molecules. One of these is disordered equally over two positions.

{2,6-Bis[1-(phenylimino)ethyl]pyridine}dichloridomanganese(II) dichloromethane hemisolvate

The title complex, [MnCl2(C21H19N3)]·0.5CH2Cl2 or [MnCl2(Plep)]·0.5CH2Cl2 {Plep is 2,6-bis­[1-(phenyl­imino)eth­yl]pyridine, derived from the condensation of 2,6-diacetyl­pyridine and aniline in methanol} is composed of two crystallographically independent [MnCl2(Plep)] neutral units and a CH2Cl2 solvent mol­ecule. Both complex mol­ecules have similar geometries in which the MnII atom is coordinated by the N atoms of pyridine and the two imine groups of a neutral Schiff base, and by two chloride anions in a distorted trigonal–bipyramidal geometry. The structure of each [MnCl2(Plep)] unit exhibits a pseudo-mirror plane through the metal atom, two chloride anions and the pyridine ring. The crystal packing is stabilized by inter­molecular C—H⋯Cl and C—H⋯π and inter­actions.

Diaquabis[5-(1H-tetrazol-5-ylamino-κN4)tetrazolato-κN1]manganese(II) dihydrate

The title compound, [Mn(C2H2N9)2(H2O)2]·2H2O, has been prepared under hydro­thermal conditions. The MnII atom, lying on an inversion center, is coordinated in an octa­hedral geometry defined by four N atoms from two di-1H-tetra­zol-5-ylaminate ligands in the equatorial plane and two water mol­ecules in the axial positions. The complex mol­ecules are linked into a three-dimensional network through O—H⋯N, N—H⋯O and N—H⋯N hydrogen bonds.

Catena-Poly[[aqua(4,4′-bipyridine-κ2 N,N′)manganese(II)]-μ-3-(4-carboxylatophenoxy)propionato-κ3 O:O′,O′′

In the crystal structure of the polymeric title compound, [Mn(C10H8N2)(C10H8O5)(H2O)] n , the MnII atom is O,O′-chelated by the aromatic carboxylate end of the 3-(4-carboxylatophenoxy)propionate dianion and is covalently bonded (through one O atom) by the aliphatic carboxylate end of another dianion; it is also coordinated by a water molecule. The compound adopts a helical chain structure that propagates along the c axis of the orthorhombic unit cell. The coordinated water molecule engages in both intrachain and interchain hydrogen bonding; the interchain hydrogen bonds result in a honeycomb motif. The compound crystallizes as a 0.36:0.64 inversion twin.

Diaqua[N,N′-(o-phenylene)bis(pyridine-2-carboxamidato)-κ 4 N]manganese(III) perchlorate

In the MnIII complex of the title compound, [MnIII(C18H12N4O2)(H2O)2]ClO4, the MnIII atom is coordinated by four N atoms from the bpb2− [1,2-bis(pyridine-2-carboxamido)benzene] ligand located in the equatorial plane and two O atoms of water molecules at axial positions, yielding a distorted MnN4O2 octahedral coordination geometry. The bpb2− ligand is nearly planar, with a maximum deviation of 0.2311 (3) Å from the mean plane. The MnIII complex cation and the perchlorate anion, both of which are located on twofold rotation axes, are connected by O—H...O and C—H...O hydrogen bonds into a three-dimensional supramolecular network structure.

Synthesis and Characterization of a Mn22 Single-Molecule Magnet and a [Mn22]n Single-Chain Magnet

The reactions of [Mn12O12(O2CEt)16(H2O)4] with phenylphosphinic acid (PhHPO2H) in MeCN and MeCN/CH2Cl2 have led to isolation of [Mn22O12(O2CEt)22(O3PPh)8(H2O)8] (2) and [Mn22O12(O2CEt)20(O3PPh)8(O2PPhH)2(H2O)8]n (3), respectively, both containing PhPO3(2-) groups from in situ oxidation of PhHPO(2)(-). Complex 2 is molecular and consists of two Mn9 subunits linked by four additional Mn atoms. Complex 3 contains almost identical Mn22 units as 2, but they are linked into a one-dimensional chain structure. The Mn22 unit in both compounds is mixed-valence Mn(III)18, Mn(II)4. Solid-state, variable-temperature dc magnetic susceptibility and magnetization measurements were performed on vacuum-dried samples of 2 and 3, indicating dominant antiferromagnetic interactions. A good fit of low-temperature magnetization data for 2 could not be obtained because of problems associated with low-lying excited states, as expected for a high nuclearity complex containing Mn(II) atoms. An approximate fit using only data collected in small applied fields indicated an S = 7 or 8 ground state for 2. Solid-state ac susceptibility data established that the true ground state of 2 is S = 7 and that the connected Mn22 units of 3 are ferromagnetically coupled. Both 2 and 3 displayed weak out-of-phase ac signals indicative of slow magnetization relaxation. Single-crystal magnetization versus applied dc field scans exhibited hysteresis loops for both compounds, establishing them as new single-molecule and single-chain magnets, respectively. Complex 2 also showed steps in its hysteresis loops characteristic of quantum tunneling of magnetization, the highest nuclearity molecule to show such QTM steps. Arrhenius plots constructed from dc magnetization versus time decay plots gave effective barriers to magnetization relaxation (U(eff)) of 6 and 11 cm(-1) for 2 and 3, respectively.

Poly[[hexaaquabis(μ3-trans-propene-1,2,3-tricarboxylato)trimanganese(II)] 0.2-hydrate

The title compound, {[Mn-3( C6H3O6)center dot 0.2(H2O)(6)]center dot 0.2H(2)O}(n), contains a three- dimensional open framework formed by each organic ligand mu(3)-bridging three six-coordinated Mn-II atoms (one of which resides on a twofold crystallographic axis). Uncoordinated water molecules are located in the channels of the framework along the c-axis direction. The primary O-H center dot center dot center dot O intermolecular interactions have O center dot center dot center dot O distances ranging from 2.680 (4) to 3.020 ( 13) angstrom and O-H center dot center dot center dot O angles ranging from 125 (4) to 179 (4)

Poly[diaqua-di-μ3-malonato-μ-pyrazine-dimanganese(II)

The title compound, [Mn2(C3H2O4)2(C4H4N2)(H2O)2]n, is isostructural with its CoII, NiII, ZnII and CdII analogues, and the complex resides on a crystallographic centre of inversion (at the pyrazine ring centroid). The MnII atoms are linked via coordinated malonates, forming a two-dimensional network with cavities. These sheets are further connected into a three-dimensional network by bridging pyrazine ligands which have inversion symmetry. The coordination geometry around the MnII atom is a tetra­gonally elongated octa­hedron, with pyrazine N and aqua O atoms at the axial positions.

Diacetato(1,4,8,11-tetraazacyclotetradecane)manganese(III) perchlorate monohydrate

The title compound, [Mn(CH3COO)2(C10H24N4)]ClO4·H2O, contains two crystallographically independent cationic complexes, each located with their central MnIII atom on a centre of inversion. Each MnIII atom is six-coordinated in a distorted octa­hedral geometry by two O atoms from acetate anions occupying axial positions and four N atoms from 1,4,8,11-tetra­azacyclo­tetra­decane (cyclam) occupying equatorial positions. The compound displays intra- and inter­molecular N—H⋯O and O—H⋯O hydrogen bonding.

Double interpenetrated structure of poly[tetra-μ2-cyanido-bis(μ2-1,2-di-4-pyridylethane)manganese(II)disilver(I)

In the title compound, [Ag2Mn(CN)4(C12H12N2)2], the Mn atom is located on an inversion center and is linked to adjacent Mn atoms by four μ-[Ag(CN)2]− units. Each [Ag(CN)2]− unit connects two Mn atoms, defining the edges of a large {Mn4[Ag(CN)2]4} mesh. The MnII atom is further coordinated by two 1,2-di-4-pyridylethane ligands in a trans arrangement to attain an MnN6 octa­hedral coordination. The AgI atoms are three-coordinate, with two C atoms from CN− and one N atom from a 1,2-di-4-pyridylethane ligand. The doubly inter­penetrating three-dimensional framework structure is built by the stacking of {Mn[Ag(CN)2]2} network sheets and 1,2-di-4-pyridylethane bridges from an Mn atom in one network, penetrating through the {Mn4[Ag(CN)2]4} meshes of the adjacent networks, to two Ag atoms in adjacent networks.

Catena-Poly[[aqua(pyrazine-2-carboxylato-κ2N1,O)manganese(II)]-μ-pyrazine-2-carboxylato-κ3N1,O:N4

The title compound, [Mn(C5H3N2O2)2(H2O)]n, prepared by hydro­thermal synthesis, is isostructural with its FeII, CoII, NiII and CuII analogues. The asymmetric unit contains two bidendate pyrazine-2-carboxyl­ate anions coordinated to MnII in the equatorial plane through one N and one O atom. The MnII atoms are linked into chains by the second N atom of one of the pyrazine-2-carboxyl­ate anions coordinating to an axial site of a neighbouring MnII atom. The slightly distorted octa­hedral coordination around MnII is completed by a water mol­ecule, which forms hydrogen bonds to link the chains into a three-dimensional structure. The investigated crystal was an inversion twin.

Aquabis(2,4-dichloro-6-formylphenolato-κ2O,O′)(N,N′-dimethylformamide-κO)manganese(II)

In the title compound, [Mn(C7H3Cl2O2)2(C3H7NO)(H2O)], the MnII atom is octa­hedrally coordinated by four O atoms from two bidentate 2,4-dichloro-6-formyl­phenolate ligands forming the equatorial plane, and by one O atom from a water mol­ecule and one O atom from N,N-dimethyl­formamide trans in axial positions. A pseudo-dimer is constructed through O—H⋯O, O—H⋯Cl and slipped π–π stacking (with a centroid-to-centroid distance of 3.692 A and inter­planar distance of 3.47 A, giving an offset angle of 20°) inter­actions. Short Cl⋯Cl inter­actions may help in stabilizing the packing.

Poly[chlorido(μ3-1,2,4-triazolato)manganese(II)

The title compound, [Mn(C2H2N3)Cl]n, has been prepared by the hydro­thermal reaction of manganese(II) chloride and 1,2,4-triazole. The MnII cation is surrounded by three N atoms belonging to three different triazolate ligands and a Cl atom, and exhibits a slightly distorted tetra­hedral coordination geometry. A polymeric layer is formed by the triply bridging nature of the 1,2,4-triazolate ligand bonded to three different MnII atoms through its three N atoms. The layer contains both binuclear units and tetra­nuclear macrocyclic units. In the binuclear unit, two Mn atoms are bridged by two nearly coplanar triazolate groups through the 1,2-positions, affording a six-membered ring around an inversion center. Each binuclear unit is further connected to four parallel units through the other four N atoms of the triazolate groups. Four adjacent units, which are pairwise parallel, afford 16-membered tetra­nuclear macrocyclic units. In each of these, the two nearest-neighbor Mn atoms are bridged by a single triazolate group through the 1,4-positions.

Diaquabis[1-ethyl-6-fluoro-7-(4-methylpiperazin-4-ium-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylato-κ2O3,O4]manganese(II) benzene-1,4-dicarboxylate tetradecahydrate

In the title compound, [Mn(C17H20FN3O3)2(H2O)2](C8H4O4).14H2O, the MnII atom (site symmetry \overline{1}) exhibits a distorted MnO6 octa­hedral geometry defined by two neutral bidentate O,O-bonded 1-ethyl-6-fluoro-7-(4-methyl­piperazin-4-ium-1-yl)-4-oxo-1,4-dihydro­quinoline-3-carboxyl­ate (Hpef) zwitterions and two water mol­ecules. The charge-balancing benzene-1,4-dicarboxyl­ate (1,4-bdc) anion is also centrosymmetric. An extensive network of O—H⋯O and O—H⋯N hydrogen bonds helps to establish the crystal packing.