Lattice Solvent Engineering Improves the Stability of a Cobalt Pyrenylnitronylnitroxide Ferrimagnetic Chain.

Reaction of 2-(1'-pyrenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1-imidazole-3-oxide-1-oxyl (PyrNN) with [Co(hfac)(HO)] (hfac = hexafluoroacetylacetonate) in heptane solvent () with a small amount of bromoform (CHBr = ) gives the 1D ferrimagnetic complex [Co(hfac)PyrNN]·0.5·0.5 ().

Synthesis, Magnetic and High-Field EPR Investigation of Two Tetranuclear Ni-Based Complexes.

Two tetranuclear compounds with a cubane-like structure were synthesized from a one-pot reaction between Ni and 2,2,6,6-tetramethyl-3,5-heptanedione (Hdpm) for or 4,4,4-trifluoro-1-phenyl-1,3-butanedione (Hbta) for in the presence of sodium methoxide. The crystal structures of both compounds have been determined by single-crystal X-ray diffraction, and their magnetic properties have been studied by SQUID magnetometry as well as by high-field electron paramagnetic resonance (HFEPR) spectroscopy. For , the temperature dependence of the magnetic susceptibility can be fitted by taking into account Ni···Ni ferromagnetic interactions, which leads to an = 4 ground-state spin.

Lanthanide chains containing the naphthalenyl nitronyl nitroxide radical.

In this contribution we report the synthesis, structure and magnetic properties of a family of lanthanide-based one dimensional compounds [Ln(hfac)(NaphNN)] , where Ln = Gd (1), Dy(2), Tb(3) and NaphNN is the nitronyl nitroxide (NN) radical 2-(1'-naphthalenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1-Imidazole-3-oxide-1-oxyl. The crystal structure reveals well isolated chains with a twofold helical axis. Magnetic investigation of the gadolinium(iii) chains showed relevant intrachain interactions between Gd-NN nearest neighbors and also Gd-Gd and NN-NN next nearest neighbors.

Magnetic Cationic Copper(II) Chains and a Mononuclear Cobalt(II) Complex Containing [Ln(hfac)] Blocks as Counterions.

Four new heterospin compounds with molecular formula {[Cu(hfac)(TlTrzNIT)][Ln(hfac)]} ·CH (Ln = Gd (1), Tb (2), or Dy (3)) and [Co(hfac)(TlTrzNIT)][Dy(hfac)] (4), where hfac is hexafluoroacetylacetonato and TlTrzNIT is the nitronylnitroxide radical 1-( m-tolyl)-1 H-1,2,3-triazole-4-(4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), were obtained. All structures were determined by single-crystal X-ray diffraction. In compounds 1-3, the TlTrzNIT radical is bridge-coordinated to copper(II) ions, leading to positively charged copper(II)-radical chains containing [Ln(hfac)] as counterions.

Synthesis, Crystal Structures, and EPR Studies of First MnLn Hetero-binuclear Complexes.

A new family of binuclear complexes [MnLn(dpm)(MeO)(MeOH)] is reported (where Ln = La (1), Pr (2), and Eu(3)). These compounds were obtained from a one-pot reaction between 2,2,6,6-tetramethyl-3,5-heptanodione (Hdpm), Mn, and the respective Ln salt in the presence of sodium methoxide. The derivative containing the diamagnetic ion La has been synthesized in order to characterize the local anisotropy of the Mn ion.

Binuclear Lanthanide-Radical Complexes Featuring Two Centers with Different Magnetic and Luminescence Properties.

Binuclear complexes with general formula [Ln(hfac)(HO)(dppnTEMPO)] (Ln = Gd, Tb, and Dy) have been obtained using the paramagnetic ligand 1-piperidinyl-4-[(diphenylphosphinyl)amino]-2,2,6,6-tetramethyl (dppnTEMPO) as a bridge. One of the lanthanide ions is ferromagnetically coupled with the TEMPO moiety. Two of the complexes (Dy and Tb) show slow relaxation of the magnetization, and the non-magneto-equivalence of the two Ln ions was clearly observed.

A single-chain magnet with a very high blocking temperature and a strong coercive field.

Two isostructural 1D complexes, [M(hfac)2NaphNN]n [M = Mn(II) (1) or Co(II) (2); NaphNN = 1-naphthyl nitronylnitroxide], were synthesized and exhibit very strong antiferromagnetic metal-radical exchange coupling. Compound 2 shows slow magnetic relaxation behavior with a high blocking temperature (TB ≈ 13.2 K) and a very high coercive field of 49 kOe at 4.

Synthesis, crystal structure and magnetic properties of a novel heterobimetallic rhenium(IV)-dysprosium(III) chain.

The use of the mononuclear rhenium(IV) precursor [ReBr5 (H2 pydc)](-) (H2 pydc=3,5-pyridinedicarboxylic acid) as a metalloligand towards dysprosium(III) afforded the first heterobimetallic Re(IV) -Dy(III) complex. Crystal structures and static and dynamic magnetic properties of both rhenium-containing species are reported herein. The 5d-4f compound shows an extended 1D structure and the AC magnetic measurements reveal frequency dependence at low temperature suggesting slow relaxation of the magnetization.

Synthesis, crystal structures and magnetic behaviour of four coordination compounds constructed with a phosphinic amide-TEMPO radical and [M(hfac)2] (M = Cu(II), Co(II) and Mn(II)).

In the present work we describe the synthesis, crystal structures and magnetic properties of four coordination compounds obtained by assembling a new phosphinic amide containing the TEMPO moiety, 1-piperidinyloxy-4-[(diphenylphosphinyl)amino]-2,2,6,6-tetramethyl radical (dppnTEMPO), with [M(hfac)2] building blocks (M = Cu(II), Co(II), Mn(II)). The crystal structures of the coordination compounds revealed the usefulness of the functionalized radical to provide discrete or extended architectures. In the copper compound () the ligand is coordinated through the oxygen atom of the NP[double bond, length as m-dash]O linkage to the metal, which exists in a square pyramidal or octahedral geometry.

New families of hetero-tri-spin 2p-3d-4f complexes: synthesis, crystal structures, and magnetic properties.

In this work we report the synthesis, crystal structures, and magnetic behavior of 2p-3d-4f heterospin systems containing the nitroxide radical 4-azido-2,2,6,6-tetramethylpiperidine-1-oxyl radical (N3tempo). These compounds were synthesized through a one-pot reaction by using [Cu(hfac)2], [Ln(hfac)3] (hfac = hexafluoroacetylacetonate, Ln = Dy(III), Tb(III) or Gd(III)), and the N3tempo radical. Depending on the stoichiometric ratio used, the synthesis leads to penta- or trimetallic compounds, with molecular formulas [Cu3Ln2(hfac)8(OH)4(N3tempo)] (Ln = Gd, Tb, Dy) and [CuLn2(hfac)8(N3tempo)2(H2O)2] (Ln = Gd, Dy).

A cobalt pyrenylnitronylnitroxide single-chain magnet with high coercivity and record blocking temperature.

Coordination of a [Co(hfac)2] moiety (hfac = hexafluoroacetylacetonate) with a nitronylnitroxide radical linked to bulky, rigid pyrene (PyrNN) gives a helical 1:1 chain complex, in which both oxygen atoms of the radical NO(·) groups are bonded to Co(II) ions with strong antiferromagnetic exchange. The complex shows single-chain magnet (SCM) behavior with frequency-dependent magnetic susceptibility, field-cooled and zero-field-cooled susceptibility divergence with a high blocking temperature of around 14 K (a record among SCMs), and hysteresis with a very large coercivity of 32 kOe at 8 K. The magnetic behavior is partly related to good chain isolation induced by the large pyrene units.

Controlled synthesis of Mn3O4 nanoparticles in ionic liquids.

This work describes a simple one-step synthesis of Mn3O4 nanoparticles by thermal decomposition of [Mn(acac)2] (acac = acetylacetonate) using imidazolium ionic liquids (ILs) and a conventional solvent, oleylamine, for comparison. The Mn3O4 nanoparticles were characterized by XRD, ATR-FTIR, TEM, Raman, UV/VIS and magnetometry techniques. The addition of 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide IL (BMI·NTf2) yielded a smaller particle size (9.

New synthetic route toward heterometallic 3d-3d' and 3d-4f single-molecule magnets. The first Co(II)-Mn(III) heterometallic complex.

Four tetranuclear heterometallic complexes, [Co(II)2Mn2(III)(dpm)4(MeO)6] (1) and [Ln(III)2Mn(III)2(dpm)6(MeO)6(MeOH)n], where Ln = Gd (2, n = 2), Tb (3, n = 2), and Dy (4, n = 0), have been obtained following the same general synthetic route, namely, the one-pot reaction between 2,2,6,6-tetrametil-3,5-heptanodione (Hdpm), MnCl2 and CoCl2 or Ln(NO3)3 in the presence of sodium methoxide. Within the four compounds, the metal ions bridged by methoxide ligands display a defect-diheterocubane core. Compounds 1, 3, and 4 show slow relaxation of the magnetization below 4 K.

Tuning of magnetic dipolar interactions of maghemite nanoparticles embedded in polyelectrolyte layer-by-layer films.

In this study we report an experimental approach capable of tuning dipolar interactions in hybrid magnetic nanofilms produced via layer-by-layer assembly of positively-charged maghemite nanoparticles and sodium sulfonated polystyrene onto glass and silicon substrates. Morphological and magnetic properties of the as prepared nanofilms were determined by Raman spectroscopy, atomic force microscopy, conventional and SQUID magnetometry. Maghemite nanoparticles form densely packed layers with voids between particles being filled by polymeric material as observed in atomic force microscopy images.

Magnetic Mn and Co complexes with a large polycyclic aromatic substituted nitronylnitroxide.

2-(1'-Pyrenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (PyrNN) was reacted with M(hfac)(2) (M = Mn(II) and Co(II), hfac = hexafluoracetylacetonate) to give two isostructural ML(2) stoichiometry M(hfac)(2)(PyrNN)(2) complexes and a ML stoichiometry one-dimensional (1-D) polymer chain complex [Mn(hfac)(2)(PyrNN)]. The ML(2) complexes have similar crystal structures with monoclinic unit cells, in which one NO unit from each PyrNN ligand is bonded to the transition metal on cis vertices of a distorted octahedron. The major magnetic interactions are intracomplex metal-to-radical exchange (J), and intermolecular exchange across a close contact between the uncoordinated NO units (J').

Catalytic properties of thioredoxin immobilized on superparamagnetic nanoparticles.

Thioredoxin (Trx1), a very important protein for regulating intracellular redox reactions, was immobilized on iron oxide superparamagnetic nanoparticles previously coated with 3-aminopropyltriethoxysilane (APTS) via covalent coupling using the EDC (1-ethyl-3-{3-dimethylaminopropyl}carbodiimide) method. The system was extensively characterized by atomic force microscopy, vibrational and magnetic techniques. In addition, gold nanoparticles were also employed to probe the exposed groups in the immobilized enzyme based on the SERS (surface enhanced Raman scattering) effect, confirming the accessibility of the cysteines residues at the catalytic site.

Structure and morphology of spinel MFe2O4 (M=Fe, Co, Ni) nanoparticles chemically synthesized from heterometallic complexes.

We synthesized magnetic spinel ferrites from trimetallic single-source precursors. Fe(II), Co(II), and Ni(II) ferrite nanoparticles in the range of 9-25 nm were synthesized by solvothermal decomposition of trimetallic acetate complex precursors in benzyl ether in the presence of oleic acid and oleylamine, using 1,2-dodecanediol as the reducing agent. For comparison, spinel ferrite nanoparticles were synthesized by stoichiometric mixtures of metal acetate or acetylacetonate salts.

Design of 1D and 2D molecule-based magnets with the ligand 4,5-dimethyl-1,2-phenylenebis(oxamato).

Three new bimetallic oxamato-based magnets with the proligand 4,5-dimethyl-1,2-phenylenebis(oxamato) (dmopba) were synthesized using water or dimethylsulfoxide (DMSO) as solvents. Single crystal X-ray diffraction provided structures for two of them: [MnCu(dmopba)(H(2)O)(3)](n)·4nH(2)O (1) and [MnCu(dmopba)(DMSO)(3)](n)·nDMSO (2). The crystalline structures for both 1 and 2 consist of linearly ordered oxamato-bridged Mn(II)Cu(II) bimetallic chains.

A new family of oxime-based hexanuclear manganese(III) single molecule magnets with high anisotropy energy barriers.

A magneto-structural study of two salicylamidoxime-based {Mn(6)} single-molecule magnets revealed that their anisotropy energy barriers, which can reach the current record for d-transition metal complexes, are strongly dependent upon the precise arrangement of ligands and the solvation state.

Magnetic nanocomposites fabricated via the layer-by-layer approach.

In this study we describe the fabrication and characterization of nanocomposites consisting of layer-by-layer assembled polyaniline, sulfonated polystyrene, and maghemite nanoparticle layers. In order to assemble the starting components via electrostatic interaction, stable magnetic fluid containing maghemite nanoparticles (d approximately = 7 nm) with either positive or negative surface charges was used as source of nanoparticles for the layer-by-layer assembly. The structure, morphology, electrical and magnetic properties of such nanocomposite films were investigated by UV-Vis spectroscopy, atomic force microscopy, electrical, and magnetic measurements.

Mononuclear and polynuclear copper(II) complexes derived from pyridylalkylaminomethylphenol polypodal ligands.

Four mononuclear complexes [Cu(HL(1))Cl]PF(6).CH(3)OH (1), [Cu(HSL(1))Cl]PF(6).0.

New copper(II)-radical one dimensional chain: Synthesis, crystal structure, EPR, magnetic properties and DFT calculations.

The novel chain compound [Cu(Phtfac)(2)(NITpPy)](n) (where NITpPy = 4-pyridyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and Phtfac = 4,4,4-trifluoro-1-phenylbutane-1,3-dione) was synthesized and characterized structurally, magnetically and by EPR. The compound contains two non equivalent Cu(II) ions, Cu1 and Cu2, located at inversion centers and bridged by a NITpPy ligand coordinating Cu1 through the pyridine donor atom, and Cu2 through a N-O group, resulting in a head-to-head chain structure. The chain exhibits an unusual spin topology with two alternating pairs of magnetic coupling constants.

Crystal structure and magnetic properties of a new chiral manganese(II) three-dimensional framework: Na(3)[Mn(3)(HCOO)(9)].

A structural and magnetic characterization of a trinuclear chiral Mn(II) formate three-dimensional framework exhibiting a triangular arrangement is presented. Compound Na(3)[Mn(3)(HCOO)(9)] was obtained by solvothermal synthesis and crystallizes in the chiral cubic space group P2(1)3 and is well described by a Delta conformation. The structure displays triangular Mn(3) building blocks, in which the metal centers are bonded by formate ligands in a syn-anti mode (Mn-Mn 5.