A new class of single-molecule magnet: [Mn9O7(OAc)11(thme)(py)3(H2O)2] with an S = 17/2 ground state

The reaction of [Mn3O(OAc)6(py)3] with 1,1,1-tris(hydroxymethyl)ethane (H3thme) gives the Mn(IV)3Mn(III)4Mn(II)2 complex [Mn9O7(OAc)11(thme)(py)3(H2O)2], which has an S = 17/2 ground state and displays strong out-of-phase signals in ac susceptibility studies that establish it as a new class of single-molecule magnet.     

A candidate for a single‐chain magnet: [Mn3(OAc)6(py)2(H2O)2]n (OAc is acetate and py is pyridine)

The title complex, catena‐poly[di‐μ₃‐acetato‐κ⁶O:O:O′‐tetra‐μ₂‐acetato‐κ⁴O:O;κ⁴O:O′‐diaquabis(pyridine‐κN)trimanganese(II)], [Mn₃(CH₃COO)₆(C₆H₅N)₂(H₂O)₂]_n, is a true one‐dimensional coordination polymer, in which the Mn^II centres form a zigzag chain along [010]. The asymmetric unit contains two metal centres, one of which (Mn1) lies on an inversion centre, while the other (Mn2) is placed close to an inversion centre on a general position. Since all the acetates behave as bridging ligands, although with different μ₂‐ and μ₃‐coordination modes, a one‐dimensional polymeric structure is formed, based on trinuclear repeat units (Mn1...Mn2...Mn2′), in which the Mn2 and Mn2′ sites are related by an inversion centre. Within this monomeric block, the metal–metal separations are Mn1...Mn2 = 3.36180 (18) Å and Mn2...Mn2′ = 4.4804 (3) Å. Cation Mn1, located on an inversion centre, displays an [MnO₆] coordination sphere, while Mn2, on a general position, has a slightly stronger [MnO₅N] ligand field, as the sixth coordination site is occupied by a pyridine molecule. Both centres approximate an octahedral ligand field. The chains are parallel in the crystal structure and interact via hydrogen bonds involving coordinated water molecules. However, the shortest metal–metal separation between two chains [5.3752 (3) Å] is large compared with the intrachain interactions. These structural features are compatible with a single‐chain magnet behaviour, as confirmed by preliminary magnetic studies.     

[VO(SeO3)(H2O)2]·0.5H2O

In poly[[diaquaoxido[μ₃‐trioxidoselenato(2−)]vanadium(IV)] hemihydrate], {[VO(SeO₃)(H₂O)₂]·0.5H₂O}_n, the octahedral V(H₂O)₂O₄ and pyramidal SeO₃ building units are linked by V—O—Se bonds to generate ladder‐like chains propagating along the [010] direction. A network of O—H...O hydrogen bonds helps to consolidate the structure. The O atom of the uncoordinated water molecule lies on a crystallographic twofold axis. The title compound has a similar structure to those of the reported phases [VO(OH)(H₂O)(SeO₃)]₄·2H₂O and VO(H₂O)₂(HPO₄)·2H₂O.     

对自旋交叉化合物[Fe(dpq)(py)2(NCS)2]·H2O·py 和[Fe(dpq)(py)2(NCSe)2]·1.5H2O的研究

为了研究配体修饰对自旋交叉现象的影响,我们合成了两个Fe?自旋交叉的配合物犤Fe(dpq)(py)2(NCS)2犦·H2O·py和犤Fe(dpq)(py)2(NCSe)2犦·1.5H2O,(dpq=二吡嗪犤2,3-f:2'3'-h犦喹喔啉,py=吡啶)。通过对这两个配合物磁性质和穆斯堡尔谱的研究,发现和用邻啡咯啉配体合成的配合物比较,配体的修饰对自旋交叉性质以及其临界温度都有着显著影响。     

对自旋交叉化合物[Fe(dpq)(py)2(NCS)2]·H2O·py和[Fe(dpq)(py)2(NCSe)2]·1.5H2O的研究

为了研究配体修饰对自旋交叉现象的影响,我们合成了两个Fe(Ⅱ)自旋交叉的配合物[Fe(dpq)(py)₂(NCS)₂]·H₂O·py和[Fe(dpq)(py)₂(NCSe)₂]·1.5H₂O,(dpq=二吡嗪[2,3-f:2′3′-h]喹喔啉,py=吡啶)。通过对这两个配合物磁性质和穆斯堡尔谱的研究,发现和用邻啡咯啉配体合成的配合物比较,配体的修饰对自旋交叉性质以及其临界温度     

Palladium(II)-substituted tungstosilicate [Cs2K(H2O)7Pd2WO(H2O)(A--SiW9O34)2]9-

The palladium(II)-substituted tungstosilicate [Cs(2)K(H(2)O)(7)Pd(2)WO(H(2)O)(A-alpha-SiW(9)O(34))(2)](9)(-) (1) has been synthesized and characterized by IR, elemental analysis, and electrochemistry. Single-crystal X-ray analysis was carried out on Cs(3)K(2)Na(4)[Cs(2)K(H(2)O)(7)Pd(2)WO(H(2)O)(A-alpha-SiW(9)O(34))(2)].5H(2)O (1a), which crystallizes in the monoclinic system, space group P2(1)/n, with a = 16.655(3) A, b = 19.729(4) A, c = 25.995(5) A, beta = 95.46(3) degrees , and Z = 4. Polyanion 1represents the first structurally characterized palladium(II)-substituted tungstosilicate. The title polyanion consists of two (A-alpha-SiW(9)O(34)) Keggin moieties linked via a [WO(H(2)O)](4+) group and two equivalent, square-planar Pd(2+) ions leading to a sandwich-type structure with C(2)(v) symmetry. The central belt of 1 contains also one potassium and two cesium ions. Polyanion 1 was synthesized by reaction of Pd(CH(3)COO)(2) with K(10)[A-alpha-SiW(9)O(34)] in aqueous acidic medium (pH 4.8). A cyclic voltammetry study of polyanion 1 in a pH 5 medium shows a Pd(0) deposition process on the glassy carbon electrode surface. The corresponding wave and that of tungsten redox processes could be separated clearly during the first few runs before their merging into a broad composite wave. The film thickness increases with the number of potential cycles or the duration of potentiostatic electrolysis. As judged from hydrogen sorption/desorption pattern, the quality of the film deposited from polyanion 1 is better than that of a film deposited directly from Pd(2+) solutions.     

Mixed-valence MnIIIMnIV clusters [Mn7O8(O2SePh)8(O2CMe)(H2O)] and [Mn7O8(O2SePh)9(H2O)]: single-chain magnets exhibiting quantum tunneling of magnetization

The syntheses, structures, and magnetic properties of two new Mn7 complexes containing phenylseleninate ligands are reported. [Mn7O8(O2SePh)8(O2CMe)(H2O)] (1) and [Mn7O8(O2SePh)9(H2O)] (2) were both prepared by the reaction of 18 equiv of benzeneseleninic acid (PhSeO2H) with [Mn12O12(O2CMe)16(H2O)4] in MeCN. Complex 1 x 6MeCN crystallizes in the triclinic space group P, and complex 2 x 2CH2Cl2 crystallizes in the monoclinic space group P2(1)/m. Both compounds possess an unprecedented [Mn7O8]9+ core comprising a central [MnIII3(micro3-O)4]+ unit attached to [MnIV2(micro-O)2]4+ and [MnIV2(micro-O)(micro3-O)]4+ units on either side. In each cluster, the PhSeO2- groups function as bridging ligands between adjacent Mn centers. The structure reveals strong Se.O intermolecular contacts between Mn7 units to give a one-dimensional chain structure, with weak interchain interactions. Solid-state DC magnetic susceptibility measurements of complexes 1 and 2 reveal that they have very similar properties, and detailed studies on 1 by AC susceptibility measurements confirm an S = 2 ground-state spin value. In addition, out-of-phase AC signals are observed, suggesting slow magnetization relaxation. Magnetization versus DC field sweeps down to 0.04 K reveals hysteresis loops, but the temperature dependence of the coercivity is not what is expected of a single-molecule magnet. Instead, the behavior is due to single-chain magnetism, albeit with weak antiferromagnetic interactions between the chains, with the barrier to relaxation arising from a combination of molecular anisotropy and ferromagnetic intermolecular exchange interactions mediated by the Se...O contacts. An Arrhenius plot was constructed from the magnetization versus time decay data. The thermally activated region at > 0.5 K gave an effective relaxation barrier (Ueff) of 14.2 K. Below approximately 0.1 K, the relaxation is independent of temperature, which is characteristic of magnetization quantum tunneling through the anisotropy barrier. These Mn7 compounds are thus the first single-chain magnets to comprise polynuclear metal clusters and also the first for which the temperature-independent relaxation characteristic of tunneling has been identified. The work also emphasizes that out-of-phase AC signals for ostensibly molecular compounds are not sufficient proof by themselves of a single-molecule magnet.     

Fluoride-bridged {Ln(2)Cr(2)} polynuclear complexes from semi-labile mer-[CrF(3)(py)(3)] and [Ln(hfac)(3)(H(2)O)(2)

The trifluorido complex mer-[CrF(3)(py)(3)] (py = pyridine) reacts with 1 equiv. of [Ln(hfac)(3)(H(2)O)(2)] and depending on the solvent forms the tetranuclear clusters [Cr(2)Ln(2)(μ-F)(4)(μ-OH)(2)(py)(4)(hfac)(6)], 1Ln, and [Cr(2)Ln(2)(μ-F)(4)F(2)(py)(6)(hfac)(6)], 2Ln, in acetonitrile and 1,2-dichloroethane, respectively (Ln = Y, Gd, Tb, Dy, Ho, and Er; hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone). Reaction with [Dy(hfac)(3)(H(2)O)(2)] in dichloromethane produces the dinuclear cluster [CrDy(μ-F)F(OH(2))(py)(3)(hfac)(4)], 3Dy. All the clusters feature fluoride bridges between the chromium(iii) and lanthanide(iii) centres. Fits of susceptibility data for 1Gd and 2Gd reveal the fluoride-mediated chromium(iii)-lanthanide(iii) exchange interactions to be 0.43(5) cm(-1) and 0.57(7) cm(-1), respectively (in the convention). Heat capacity measurements on 2Gd reveal a moderate magneto-caloric effect (MCE) reaching -ΔS(m)(T) = 11.4 J kg(-1) K(-1) for ΔB(0) = 9 T → 0 T at T = 4.1 K. Out-of-phase alternating-current susceptibility (χ') signals are observed for 1Dy, 2Dy and 2Tb, demonstrating slow relaxation of the magnetization.     

配合物[Mn(phendione)(PDC)(H2O)2]·2H2O的合成与晶体结构

The title compound [Mn(phendione)(PDC)(H₂O)₂]·2H₂O (H₂PDC=pyridine-2，6-dicarboxylic acid) has been prepared in aqueous solution and characterized by single X-ray diffraction structure determination， elemental analysis， IR spectroscopy， and thermal analyses. The compound crystallizes in Monoclinic system， space group C2/c， a=1.017 51(11) nm， b=1.483 25(11) nm， c=1.461 21(13) nm， β=109.86(10)°， V=2.074 1(3) nm³， Z=4， F(000)=1 028， μ=0.701 mm^-1， D_c=1.609 g·cm^-3， R₁=0.028 9， wR₂=0.078 8 [I>2σ(I)]. Crystal structure reveals that complex consists of one-dimensional chain framework bridged by hydrogen bonds that formed by uncoordinated water and oxygen atom of carboxyl group in PDC^2-. Furthermore， the complexes form a three-dimensional super-molecular structure through hydrogen bonds. CCDC: 648570.     

Synthesis and Structural Characterization of [Mn（sapn）（H2O）2]Br

1 INTRODUCTION Many of the recent advances in the coordination chemistry of manganese have been driven by the involvement of the manganese in several biological redox-active systems[1,2], of which the most important is the oxygen-evolving complex (EOC) of photosystem II (PS II) in green plants [3]. Since the preparations and structural characterizations of the complexes containing N,O-donor ligands have been studied extensively as simple active-site models for the photosystem II[4,5]…     

Two Heteroleptic Zinc(II) Complexes: [Zn(phen)(C9H15O6)2] and [Zn2(phen)2(H2O)2(C10H16O4)2] · 3H2O

Reactions of a freshly prepared Zn(OH)_2‐2x(CO₃)x · yH₂O precipitate, phenanthroline with azelaic and sebacic acid in CH₃OH/H₂O afforded [Zn(phen)(C₉H₁₅O₄)₂] ( 1 ) and [Zn₂(phen)₂(H₂O)₂(C₁₀H₁₆O₄)₂] · 3H₂O ( 2 ), respectively. They were structurally characterized by X‐ray diffraction methods. Compound 1 consists of complex molecules [Zn(phen)(C₉H₁₅O₄)₂] in which the Zn atoms are tetrahedrally coordinated by two N atoms of one phen ligand and two O atoms of different monodentate hydrogen azelaato groups. Intermolecular C(alkyl)‐H···π interactions and the intermolecular C(aryl)‐H···O and O‐H···O hydrogen bonds are responsible for the supramolecular assembly of the [Zn(phen)(C₉H₁₅O₄)₂] complexes. Compound 2 is built up from crystal H₂O molecules and the centrosymmetric binuclear [Zn₂(phen)₂(H₂O)₂(C₁₀H₁₆O₄)₂] complex, in which two [Zn(phen)(H₂O)]²⁺ moieties are bridged by two sebacato ligands. Through the intermolecular C(alkyl)‐H···O hydrogen bonds and π‐π stacking interactions, the binuclear complex molecules are assembled into layers, between which the lattice H₂O molecules are sandwiched. Crystal data: ( 1 ) C2/c (no. 15), a = 13.887(2), b = 9.790(2), c = 22.887(3)Å, β = 107.05(1)°, U = 2974.8(8)ų, Z = 4; ( 2 ) P1¯ (no. 2), a = 8.414(1), b = 10.679(1), c = 14.076(2)Å, α = 106.52(1)°, β = 91.56(1)°, γ = 99.09(1)°, U = 1193.9(2)ų, Z = 1.     

Electrochemical and Biological Studies on Reactivity of [VO(oda)(H2O)2], [Co(oda)(H2O)2]·H2O,and [Ni(oda)­(H2O)3]·1.5H2O Towards Superoxide Free Radicals

The reactivity of superoxide free radicals (O₂ ^{· –}) generated electrochemically towards the oxydiacetate metal complexes, namely [VO(oda)(H₂O)₂], [Co(oda)(H₂O)₂] · H₂O, and [Ni(oda)(H₂O)₃] · 1.5H₂O (oda = oxydiacetate) was examined by cyclic voltammetry. The measurements were carried out in DMSO solution using a platinum electrode. Based on the height of the anodic peak E_a that corresponds to electrochemical oxidation O₂ ^{· –} → O₂ + e, in the absence and in the presence of the compounds in the mixture, their O₂ ^{· –} scavenge ability was assessed. The influence of the type of the complex was briefly discussed. H₂O₂ was used to induce cellular injury in a mouse hippocampal cell line (HT22). The cytoprotection of chemical compounds was tested at the mitochondrial (MTT test) and plasma membrane level (LDH leakage). Dose‐dependent effect (10 and 100 μM of the complex) of investigated compounds was observed.     

Synthesis and Structural Characterization of [Mn（phen）2（H2O）2]（OAc）2.6H2O

1 INTRODUCTION Water oxidation to oxygen gas by photo- synthetic apparatus of green plants and cyano- bacteria is the origin of this gas in the atmosphere. The water oxidation center is a tetranuclear, oxide- bridged manganese cluster with O,N-based peri- pheral ligation by amino acid side-chain group[1, 2]. The binding of aqua to the Mn site may be impor- tant to the oxidation of aqua for producing dioxygen. 1,10-Phenanthroline has been adopted to simulate coordination sphere of manga…     

Direct determination of the anisotropy and exchange splittings in the dimeric single-molecule magnet [Mn4O3Cl4(O2CEt)3(py)3]2.8MeCN by inelastic neutron scattering

Energy splittings resulting from anisotropy and exchange interactions in the dimer of single-molecule magnets [Mn4O3Cl4(O2CEt)3(py)3]2.8MeCN are determined for both an undeuterated and a partially deuterated sample using inelastic neutron scattering. The antiferromagnetic (AF) exchange coupling between the two Mn4 subunits strongly depends on their separation. The Cl...Cl distance between the two subunits can be modified either by exchanging the solvent of crystallization or by deuteration of the C-H...Cl hydrogen bonds. The exchange of acetonitrile for n-hexane leads to a five times greater shortening of the Cl...Cl separation than does full deuteration of all the hydrogen bonds. As a result, the AF exchange coupling constants between the subunits are 0.0073(4) and 0.0103(9) meV in the samples with acetonitrile and n-hexane solvent molecules, respectively, in the crystal structure. On the other hand, the effect of C-H...Cl deuteration on the AF exchange coupling is not detectable within the experimental accuracy of INS.