Slow Magnetic Relaxation in {[CoCxAPy)] 2.15 H2O}n MOF Built from Ladder-Structured 2D Layers with Dimeric SMM Rungs.

We present the magnetic properties of the metal-organic framework {[CoCxAPy]·2.15 H2O}n (Cx = bis(carboxypropyl)tetramethyldisiloxane; APy = 4,4`-azopyridine) (1) that builds up from the stacking of 2D coordination polymers. The 2D-coordination polymer in the bc plane is formed by the adjacent bonding of [CoCxAPy] 1D two-leg ladders with Co dimer rungs, running parallel to the c-axis. The crystal packing of 2D layers shows the presence of infinite channels running along the c crystallographic axis, which accommodate the disordered solvate molecules. The Co(II) is six-coordinated in a distorted octahedral geometry, where the equatorial plane is occupied by four carboxylate oxygen atoms. Two nitrogen atoms from APy ligands are coordinated in apical positions. The single-ion magnetic anisotropy has been determined by low temperature EPR and magnetization measurements on an isostructural compound {[Zn0.8Co0.2CxAPy]·1.5 CH3OH}n (2). The results show that the Co(II) ion has orthorhombic anisotropy with the hard-axis direction in the C2V main axis, lying the easy axis in the distorted octahedron equatorial plane, as predicted by the ab initio calculations of the g-tensor. Magnetic and heat capacity properties at very low temperatures are rationalized within a S* = 1/2 magnetic dimer model with anisotropic antiferromagnetic interaction. The magnetic dimer exhibits slow relaxation of the magnetization (SMM) below 6 K in applied field, with a tlf ≈ 2 s direct process at low frequencies, and an Orbach process at higher frequencies with U/kB = 6.7 ± 0.5 K. This compound represents a singular SMM MOF built-up of Co-dimers with an anisotropic exchange interaction.

Correction: Magnetic properties of the seven-coordinated nanoporous framework material Co(bpy)1.5(NO3)2 (bpy = 4,4'-bipyridine).

Correction for 'Magnetic properties of the seven-coordinated nanoporous framework material Co(bpy)1.5(NO3)2 (bpy = 4,4'-bipyridine)' by Elena Bartolomé et al., Dalton Trans., 2012, 41, 10382-10389.

2,6-Bis(bromo-meth-yl)pyridine.

In the title mol-ecule, C7H7Br2N, the C-Br vectors of the bromo-methyl groups extend to opposite sides of the pyridine ring and are oriented nearly perpendicular to its plane. In the crystal, the mol-ecules related by a c-glide-plane operation are arranged into stacks along the c axis, with centroid-centroid distances between neighboring aromatic rings of 3.778 (2) Å. A short Br⋯Br contact of 3.6025 (11) Šis observed within a pair of inversion-related mol-ecules.

Hexanuclear and undecanuclear iron(III) carboxylates as catalyst precursors for cyclohexane oxidation.

Two multinuclear complexes [Fe6(µ3-O)2(µ4-O2)L10(OAc)2(H2O)2]·2.625Et2O·2.375H2O (1) and [Fe(III)11Cl(µ4-O)3(µ3-O)5L16(dmf)(2.5)(H2O)(0.5)]·Et2O·1.25dmf·3.8H2O (2), where HL = 3,4,5-trimethoxybenzoic acid and dmf = dimethylformamide, have been prepared from trinuclear iron(III) carboxylates via their structural rearrangement in dimethylformamide or diethyl ether-dimethylformamide 9:1, respectively, and slow vapor diffusion of diethyl ether into the reaction mixture. Both compounds have been characterized by X-ray diffraction, optical, Mössbauer spectroscopy, and magnetic measurements. Complex 1 possesses a hexanuclear ferric peroxido-dioxido {Fe6(O2)(O)2}(12+) core unit, which adopts a recliner conformation, while complex 2 contains an unprecedented {Fe11O8Cl}(16+) core, in which 9 ferric ions are six-coordinate and the remaining two are five-coordinate. Another structural feature of note of the undecanuclear core is the presence of a deformed cubane entity {Fe4(µ3-O)(µ4-O)3}(4+). Both complexes act as catalyst precursors for the oxidation of cyclohexane to cyclohexanol and cyclohexanone with aqueous H2O2, in the presence of pyrazinecarboxylic acid. Remarkable TONs and TOFs (the latter mainly for 1) with concomitant quite good yields have been achieved under mild conditions. Moreover, 1 exhibits remarkably high activity in an exceptionally short reaction time (45 min), being unprecedented for any metal catalyzed alkane oxidation by H2O2. The catalytic reactions proceed via Fenton type chemistry.

Striking difference in antiproliferative activity of ruthenium- and osmium-nitrosyl complexes with azole heterocycles.

Ruthenium nitrosyl complexes of the general formulas (cation)(+)[cis-RuCl4(NO)(Hazole)](-), where (cation)(+) = (H2ind)(+), Hazole = 1H-indazole (Hind) (1c), (cation)(+) = (H2pz)(+), Hazole = 1H-pyrazole (Hpz) (2c), (cation)(+) = (H2bzim)(+), Hazole = 1H-benzimidazole (Hbzim) (3c), (cation)(+) = (H2im)(+), Hazole = 1H-imidazole (Him) (4c) and (cation)(+)[trans-RuCl4(NO)(Hazole)](-), where (cation)(+) = (H2ind)(+), Hazole = 1H-indazole (1t), (cation)(+) = (H2pz)(+), Hazole = 1H-pyrazole (2t), as well as osmium analogues of the general formulas (cation)(+)[cis-OsCl4(NO)(Hazole)](-), where (cation)(+) = (n-Bu4N)(+), Hazole =1H-indazole (5c), 1H-pyrazole (6c), 1H-benzimidazole (7c), 1H-imidazole (8c), (cation)(+) = Na(+); Hazole =1H-indazole (9c), 1H-benzimidazole (10c), (cation)(+) = (H2ind)(+), Hazole = 1H-indazole (11c), (cation)(+) = H2pz(+), Hazole = 1H-pyrazole (12c), (cation)(+) = (H2im)(+), Hazole = 1H-imidazole (13c), and (cation)(+)[trans-OsCl4(NO)(Hazole)](-), where (cation)(+) = n-Bu4N(+), Hazole = 1H-indazole (5t), 1H-pyrazole (6t), (cation)(+) = Na(+), Hazole = 1H-indazole (9t), (cation)(+) = (H2ind)(+), Hazole = 1H-indazole (11t), (cation)(+) = (H2pz)(+), Hazole = 1H-pyrazole (12t), have been synthesized. The compounds have been comprehensively characterized by elemental analysis, ESI mass spectrometry, spectroscopic techniques (IR, UV-vis, 1D and 2D NMR) and X-ray crystallography (1c·CHCl3, 1t·CHCl3, 2t, 3c, 6c, 6t, 8c). The antiproliferative activity of water-soluble compounds (1c, 1t, 3c, 4c and 9c, 9t, 10c, 11c, 11t, 12c, 12t, 13c) in the human cancer cell lines A549 (nonsmall cell lung carcinoma), CH1 (ovarian carcinoma), and SW480 (colon adenocarcinoma) has been assayed. The effects of metal (Ru vs Os), cis/trans isomerism, and azole heterocycle identity on cytotoxic potency and cell line selectivity have been elucidated. Ruthenium complexes (1c, 1t, 3c, and 4c) yielded IC50 values in the low micromolar concentration range. In contrast to most pairs of analogous ruthenium and osmium complexes known, they turned out to be considerably more cytotoxic than chemically related osmium complexes (9c, 9t, 10c, 11c, 11t, 12c, 12t, 13c). The IC50 values of Os/Ru homologs differ by factors (Os/Ru) of up to ~110 and ~410 in CH1 and SW480 cells, respectively. ESI-MS studies revealed that ascorbic acid may activate the ruthenium complexes leading to hydrolysis of one M-Cl bond, whereas the osmium analogues tend to be inert. The interaction with myoglobin suggests nonselective adduct formation; i.e., proteins may act as carriers for these compounds.

{Dy(α-fur)3}n: from double relaxation single-ion magnet behavior to 3D ordering.

The synthesis and magnetostructural properties of a new low-dimensional magnetic system based on α-furoate ligands, {[Dy(α-C4H3OCOO)(µ-(α-C4H3OCOO))2(H2O)3]}n, abbreviated {Dy(α-fur)3}n, are reported. X-ray diffraction experiments results evidence the presence of two different Dy coordination environment types differing only in the position of one of the furoate ligands. The crystallographic structure is formed by polymeric chains along the c-axis, each composed of just one Dy type, coupled within the bc-plane with chains of the same Dy type. These planes, each of them containing only one Dy type, are randomly stacked along the a-axis. The magnetic behaviour was studied by magnetization, static and dynamic susceptibility, heat capacity measurements and ab initio simulations. The directions of the easy axes of magnetization, gyromagnetic values and energy level structures of the two Dy types were obtained from ab initio calculations. {Dy(α-fur)3}n exhibits slow magnetic relaxation dynamics below 10 K. The two Dy types with different coordination environments behave as single-ion magnets, with different thermal activation energies of 80.5(6) K and 32.4(5) K, until they reach, upon cooling, a quantum tunneling (QT) regime. Magnetic diluted samples, substituting Dy by Y, {Y(x)Dy(1-x)(α-fur)3}n, were prepared to study the effect of intercluster interactions. Decreasing the Dy interaction by dilution by 90-95% leaves the activation energy unchanged, but shifts the transition to the QT regime to lower temperatures. At T = 2.4 K the tunneling time constant has been shown to decrease weakly with the field in the x = 0 case, and more strongly for x = 0.9. As the external field increases, quantum tunneling is quenched and a new slow relaxation appears that is identified at high fields as caused by a direct relaxation process. As the temperature is decreased, interchain AF coupling becomes effective and gives rise to the occurrence of an antiferromagnetic 3D order transition at T(N) = 0.66 K. From all the evidence, it is concluded that within each bc-plane Dy ions arrange in chains along the c-direction, having weak uncompensated ferromagnetic spin-canted intrachain coupling and antiferromagnetic interchain coupling.

Magnetic properties of the seven-coordinated nanoporous framework material Co(bpy)1.5(NO3)2 (bpy = 4,4'-bipyridine).

The magnetic properties of the porous metal-organic complex Co(bpy)(1.5)(NO(3))(2) (bpy = 4,4'-bipyridine), investigated by SQUID magnetometry, EPR and heat capacity measurements, are reported. The tongue-and-groove structure of this complex is formed by the assembly of T-shaped building blocks, where each Co is bound to three bpy ligands. Co(II) is hepta-coordinated by three N atoms from the bpy units, and four O atoms from two nitrate groups. Experimental results showed a large crystal field effect induced anisotropy with a zero field splitting of Δ = 198 K between the ground and excited Kramers doublets, a factor of two larger than previously reported values in Co(II) hepta-coordinated complexes. EPR revealed orthorhombic crystal field anisotropy, with gyromagnetic principal values of g(1)* = 6.1, g(2)* = 4.2 and g(3)* = 2.2, in an S* = 1/2 effective spin on the ground state Kramers doublet. Ab initio simulations allowed us to assign the anisotropy easy axis of magnetization to the binary symmetry axis of the molecule, aligned with the Co-N apical direction of the T-block.

N,N'-(1,4-Phenyl-ene)bis-(4-chloro-butanamide).

The title mol-ecule, C(14)H(18)Cl(2)N(2)O(2), lies on a crystallographic inversion center and the each 4-chloro-butanamide group adopts an anti-staggered conformation. In the crystal, adjacent mol-ecules are linked through N-H⋯O contacts, forming infinite ribbons extending parallel to the a axis.

Heteronuclear (Co-Ca, Co-Ba) 2,3-pyridinedicarboxylate complexes: synthesis, structure and physico-chemical properties.

Three pyridine 2,3-dicarboxylate complexes have been synthesized and characterized by IR spectroscopy, thermal analysis and single crystal X-ray diffractometry. Their magnetic properties have also been studied by EPR and magnetisation measurements. The decomposition of such complexes in air leads to the generation of mixed metal oxides, as confirmed by powder X-ray diffraction.

Intermatrix synthesis of polymer stabilized inorganic nanocatalyst with maximum accessibility for reactants.

In this paper we report a comparative study of different procedures for the inter-matrix synthesis (IMS) of monometallic Pd-Polymer-Stabilized Metal NanoParticles (PSMNPs) in sulfonated polyetherether ketone (SPEEK) as stabilizing polymeric matrix. The IMS technique consists in consecutive metal loading-reduction cycles and can be realized by using two different versions: (i) in situ and (ii) ex situ. For in situ IMS the bare polymeric material is first deposited onto the electrode surface followed by metal loading and reduction. The last step (reduction of metal ions to PSMNPs) can be done either chemically or electrochemically. Pd-PSMNPs were synthesized by varying both the Pd concentration in the loading solution and the IMS procedure. MNPs were characterized by TEM, XRD, ICP-OES and EDS techniques and the main differences found are related to MNPs size and their spatial distribution inside the polymeric matrix. The catalytic activity of Pd-PSMNPs synthesized by different versions of the IMS technique was evaluated by using PSMNPs modified electrodes as amperometric sensors.

Synthesis and anti-tuberculosis activity of new hetero(Mn, Co, Ni)trinuclear iron(III) furoates.

New hetero(micro(3)-oxo)trinuclear iron(III) furoates with the general formulas [Fe(2)MO(alpha-Fur)(6)(L)(H(2)O)(2)], where L = THF (1-3), DMF (4-5), M = Mn(2+) (1, 4), Co(2+) (2, 5), Ni(2+) (3, 6) and [Fe(2)MO(alpha-Fur)(6)(3Cl-Py)(3)], where M = Mn(2+) (7), Co(2+) (8), Ni(2+) (9); have been synthesised and investigated by Mössbauer and IR spectroscopies. The X-ray crystal structure has been determined for the 4 and 8 complexes, indicating that they are related to the monoclinic crystal system (P2(1)/n) and have a structure typical of mu(3)-O-bridged trinuclear iron (III) compounds. The (57)Fe Mössbauer spectra of microcrystalline samples of the compounds indicate the presence of high-spin iron (III) (S = 5/2) with a near symmetrical environments. The iron(III)-cobalt(II) containing compounds 2, 5 and 8 displayed MIC values between 0.83 / 4.00 microg/mL.

Donnan-exclusion-driven distribution of catalytic ferromagnetic nanoparticles synthesized in polymeric fibers.

One of the routes to overcome the high instability of metal nanoparticles (MNPs) lies in the use of polymeric materials for their synthesis and stabilization. Besides, one of the most serious concerns associated with the growing production and use of MNPs is the possibility of their uncontrollable escape into the medium under treatment and the environment. A possible solution to this problem could be the synthesis of ferromagnetic MNPs with desired functionality, that might not only prevent their escape by using simple magnetic traps but also allow their recovery and reuse. In our work we report the results obtained by the development of environmentally-safe polymer-metal nanocomposite materials containing polymer-stabilized MNPs (PSMNPs) with properties. This material consists of a functional polymer with immobilized Pd@Co core-shell PSMNPs distributed mainly near the surface of the polymer which makes PSMNPs maximally accessible for reagents in catalytic applications. The material was characterized by different techniques to evaluate the total metal content, the size and the magnetic properties of MNPs and their distribution inside the polymer. All nanocomposites were tested as catalysts in Suzuki cross-coupling reactions between arylboronic acids and aryl halides to produce biphenyls as a reference reaction.

A new hexaferrocene complex with a [M3(mu3-O)]7+ core.

The new hexaferrocene complex 1 has been synthesized and characterized by X-ray diffraction. Its magnetization data were fitted to a detailed theoretical model that considers nonequivalent exchange parameters between Fe ions to yield the magnetic exchange coupling values of J1/kB = -31.5 K and J2/kB = -25.8 K. Moreover, the cyclic voltammogram of complex 1 confirmed its redox activity associated with the presence of ferrocene units, with very small or negligible electronic interactions between them.