A Three-Pronged Attack To Investigate the Electronic Structure of a Family of Ferromagnetic Fe4Ln2 Cyclic Coordination Clusters: A Combined Magnetic Susceptibility, High-Field/High-Frequency Electron Paramagnetic Resonance, and 57Fe Mössbauer Study.

We present the synthesis, structure, magnetic properties, as well as the Mössbauer and electron paramagnetic resonance studies of a ring-shaped [FeIII4LnIII2(Htea)4(µ-N3)4(N3)3(piv)3] (Ln = Y 1, Gd 2, Tb 3, Dy 4, Ho 5, Er, 6) coordination cluster. The Dy, Tb, and Ho analogues show blocking of the magnetization at low temperatures without applied fields. The anisotropy of the 3d ion and the exchange interaction between 3d and 4f ions in Fe4Ln2 complexes are unambiguously determined by high-field/high-frequency electron paramagnetic resonance measurements at low temperature. Ferromagnetic exchange interaction JFe-Ln is found which decreases upon variation of the Ln ions to larger atomic numbers. This dependence is similar to the behavior shown in the effective barrier values of complexes 3-5. Further information about the anisotropy of the Ln3+ ions was gathered with 57Fe Mössbauer spectroscopy, and the combination of these methods provides detailed information regarding the electronic structure of these complexes.

Developing a "highway code" to steer the structural and electronic properties of Fe(III)/Dy(III) coordination clusters.

In the recently established field of 3d/4f coordination cluster (CC) chemistry several burning questions still need to be addressed. It is clear that combining 3d and 4f metal ions within a coordination cluster core has the potential to lead to electronic structures that will be very difficult to describe but can also be extremely interesting. Furthermore, understanding why certain core topologies seem to be favored is difficult to predict. Here we show that the secondary coordination sphere provided by the ligands influences the favored product, as demonstrated for the compound [Fe4Dy2(µ3-OH)2(n-bdea)4(C6H5CO2)8]·MeCN (1), which has a 2Fe:2Dy:2Fe core and was made using [Fe(III)3O(C6H5)CO2)(L)3](+) as starting material plus Dy(NO3)3 and N-n-butyl-diethanolamine (n-bdeaH2), compared with the compound made using a methyl meta-substituent (R) on the phenyl ring of the benzoate, [Fe(III)3O(C6H4Me)CO2)(L)3](+) as starting material, which resulted in the "square-in-square" compound [Fe4Dy4(µ3-OH)4(n-bdea)4(O2CC6H4CH3)12]·MeCN (2) when using ambient conditions. Changing reaction conditions from ambient to solvothermal leads to "double-propeller" compounds [Fe4Dy4(µ4-O)3(n-bdea)3(C6H5CO2)12]·13MeCN (3) and [Fe4Dy4(µ4-O)3(n-bdea)3(O2CC6H4CH3)12]·MeCN (4) forming with this core, resulting irrespective of the substitution on the iron benzoate starting material. Furthermore, compounds 1 and 2 can be transformed into compounds 3 and 4, respectively, using a solvothermal method. Thus, compounds 3 and 4 appear to be the thermodynamically most stable species. The factors steering the reactions toward these products are discussed. The electronic structures have been investigated using magnetic and Mössbauer studies. All compounds are cooperatively coupled 3d/4f systems, with compound 1 showing single-molecule magnet behavior.

Solvent-driven fractional crystallization for atom-efficient separation of metal salts from permanent magnet leachates.

This work reports a dimethyl ether-driven fractional crystallization process for separating rare earth elements and transition metals. The process has been successfully applied in the treatment of rare earth element-bearing permanent magnet leachates as an atom-efficient, reagent-free separation method. Using ~5 bar pressure, the solvent was dissolved into the aqueous system to displace the contained metal salts as solid precipitates. Treatments at distinct temperatures ranging from 20-31 °C enable crystallization of either lanthanide-rich or transition metal-rich products, with single-stage solute recovery of up to 95.9% and a separation factor as high as 704. Separation factors increase with solution purity, suggesting feasibility for eco-friendly solution treatments in series and parallel to purify aqueous material streams. Staged treatments are demonstrated as capable of further improving the separation factor and purity of crystallized products. Upon completion of a crystallization, the solvent can be recovered with high efficiency at ambient pressure. This separation process involves low energy and reagent requirements and does not contribute to waste generation.

Rationally designed rare earth separation by selective oxalate solubilization.

A simple, environmentally benign, and efficient chemical separation of rare earth oxalates (CSEREOX) within two rare earth element (REE) subgroups has been developed. The protocol allows for selective solubilization of water-insoluble oxalates of rare earth elements, and results in efficient REE extraction even at low initial concentrations (<5%) from processed magnet wastes.

Magnetic chains of Fe3 clusters in the {Fe3YO2} butterfly molecular compound.

The "butterfly" molecule [Fe3Y(µ3-O)2(CCl3COO)8(H2O)(THF)3] (in brief {Fe3YO2}) includes three Fe3+ ions which build a robust Fe3 cluster with a strong intracluster antiferromagnetic exchange and a total spin S = 5/2. It represents the starting magnetic system to study further interactions with magnetic rare earths when Y is replaced with lanthanides. We present heat capacity and equilibrium susceptibility measurements below 2 K, which show that each cluster has a sizeable magnetic anisotropy pointing to the existence of intercluster interactions. However, no phase transition to a long-range magnetically ordered phase is observed down to 20 mK. The intercluster interaction is analysed in the framework of the one-dimensional Blume-Capel model with an antiferromagnetic chain interaction constant J/kB = -40(2) mK between Fe3 cluster spins, and a uniaxial anisotropy with parameter D/kB = -0.56(3) K. This is associated to single chains of Fe3 clusters oriented along the shortest intercluster distances displayed by the crystal structure of {Fe3YO2}. Ac susceptibility measurements reveal that the magnetic relaxation is dominated by a quantum tunnelling process below 0.2 K, and by thermally activated processes above this temperature. The experimental activation energy of this single chain magnet, Ea/kB = 3.4(6) K, can be accounted for by the combination of contributions arising from single-molecule magnetic anisotropy and spin-spin correlations along the chains.

Synthesis, structural characterization and luminescence properties of 1-carboxymethyl-3-ethylimidazolium chloride.

A microcrystalline carboxyl-functionalized imidazolium chloride, namely 1-carboxymethyl-3-ethylimidazolium chloride, C7H11N2O2+·Cl-, has been synthesized and characterized by elemental analysis, attenuated total reflectance Fourier transform IR spectroscopy (ATR-FT-IR), single-crystal X-ray diffraction, thermal analysis (TGA/DSC), and photoluminescence spectroscopy. In the crystal structure, cations and anions are linked by C-H...Cl and C-H...O hydrogen bonds to create a helix along the [010] direction. Adjacent helical chains are further interconnected through O-H...Cl and C-H...O hydrogen bonds to form a (10-1) layer. Finally, neighboring layers are joined together via C-H...Cl contacts to generate a three-dimensional supramolecular architecture. Thermal analyses reveal that the compound melts at 449.7 K and is stable up to 560.0 K under a dynamic air atmosphere. Photoluminescence measurements show that the compound exhibits a blue fluorescence and a green phosphorescence associated with spin-allowed (1π←1π*) and spin-forbidden (1π←3π*) transitions, respectively. The average luminescence lifetime was determined to be 1.40 ns for the short-lived (1π←1π*) transition and 105 ms for the long-lived (1π←3π*) transition.

Ectonucleotidase Inhibitory and Redox Activity of Imidazole-Based Organic Salts and Ionic Liquids.

Cytotoxicity against cancer and normal cells, inhibition of ectonucleotidase, and redox properties of a new group of imidazole-based organic salts and ionic liquids were studied. The tetrachloroferrate salt of a 1-methylimidazole derivative of salicylic aldehyde had most prominent inhibitory activity against ectonucleotidase as well as a higher cytotoxicity against HeLa cells and lower cytotoxicity against BHK-21 cells than the reference compound carboplatin. The studied compounds exhibited a moderate level of antioxidant activity with better results for the salicylic aldehyde derivatives than for spiropyrans. Moreover, these compounds did not generate singlet oxygen.

A novel example of double 6-exo-trig heterocyclization: nitrile conversion to new anticancer active (HeLa cells) primary amine ionic liquids.

Conversion of nitriles under mild conditions leads to a new class of primary amines, including room temperature ionic liquids, acting as efficient anticancer agents.

Unprecedented chemical transformation: crystallographic evidence for 1,1,2,2-tetrahydroxyethane captured within an Fe(6)Dy(3) single molecule magnet.

A nonanuclear {Fe(6)Dy(3)} coordination cluster displaying SMM behaviour in which an unprecedented chemical transformation provides structural information for the existence of 1,1,2,2-tetrahydroxyethane is reported.

Evidence of slow relaxation of magnetization in dysprosium-based ionic liquids.

Dysprosium based ionic liquids displaying slow relaxation of magnetization at low temperatures are reported.

{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.

Catalytic "triangles": binding of iron in task-specific ionic liquids.

A new class of task-specific ionic liquids (ILs) which contain septuply positively charged {Fe(3)(III)O(RCOO)(6)L(3)}(7+) triangles has been synthesized and structurally characterized. Such metal-containing ILs can be repeatedly used as alternative catalysts in the synthesis of 2-pyrrolo-3'-yloxindole or the condensation of indoles with various aldehydes.

Ferromagnetic heteronuclear {Fe4(Er,Lu)2} cyclic coordination clusters based on ferric wheels.

A new family of hexanuclear ferric-lanthanide [Fe(III)(4)Ln(III)(2)(Htea)(4)(Piv)(6)(N(3))(4)] clusters, where Ln(III) = Er(1) and Lu(2) is reported. Variable temperature solid-state magnetic susceptibility studies of 1 and 2 reveal the presence of ferromagnetic (1) or competing anti- and ferromagnetic exchange interactions (2) between the constituent Fe(III) ions.

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.

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.