Miguel Julve

University of Valencia, Valenza, Valencia, Spain

Are you Miguel Julve?

Claim your profile

Publications (493)2086 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Conspectus Metallosupramolecular complexes constitute an important advance in the emerging fields of molecular spintronics and quantum computation and a useful platform in the development of active components of spintronic circuits and quantum computers for applications in information processing and storage. The external control of chemical reactivity (electro- and photochemical) and physical properties (electronic and magnetic) in metallosupramolecular complexes is a current challenge in supramolecular coordination chemistry, which lies at the interface of several other supramolecular disciplines, including electro-, photo-, and magnetochemistry. The specific control of current flow or spin delocalization through a molecular assembly in response to one or many input signals leads to the concept of developing a molecule-based spintronics that can be viewed as a potential alternative to the classical molecule-based electronics. A great variety of factors can influence over these electronically or magnetically coupled, metallosupramolecular complexes in a reversible manner, electronic or photonic external stimuli being the most promising ones. The response ability of the metal centers and/or the organic bridging ligands to the application of an electric field or light irradiation, together with the geometrical features that allow the precise positioning in space of substituent groups, make these metal-organic systems particularly suitable to build highly integrated molecular spintronic circuits. In this Account, we describe the chemistry and physics of dinuclear copper(II) metallacyclophanes with oxamato-containing dinucleating ligands featuring redox- and photoactive aromatic spacers. Our recent works on dicopper(II) metallacyclophanes and earlier ones on related organic cyclophanes are now compared in a critical manner. Special focus is placed on the ligand design as well as in the combination of experimental and computational methods to demonstrate the multifunctionality nature of these metallosupramolecular complexes. This new class of oxamato-based dicopper(II) metallacyclophanes affords an excellent synthetic and theoretical set of models for both chemical and physical fundamental studies on redox- and photo-triggered, long-distance electron exchange phenomena, which are two major topics in molecular magnetism and molecular electronics. Apart from their use as ground tests for the fundamental research on the relative importance of the spin delocalization and spin polarization mechanisms of the electron exchange interaction through extended π-conjugated aromatic ligands in polymetallic complexes, oxamato-based dicopper(II) metallacyclophanes possessing spin-containing electro- and chromophores at the metal and/or the ligand counterparts emerge as potentially active (magnetic and electronic) molecular components to build a metal-based spintronic circuit. They are thus unique examples of multifunctional magnetic complexes to get single-molecule spintronic devices by controlling and allowing the spin communication, when serving as molecular magnetic couplers and wires, or by exhibiting bistable spin behavior, when acting as molecular magnetic rectifiers and switches. Oxamato-based dicopper(II) metallacyclophanes also emerge as potential candidates for the study of coherent electron transport through single molecules, both experimentally and theoretically. The results presented herein, which are a first step in the metallosupramolecular approach to molecular spintronics, intend to attract the attention of physicists and materials scientists with a large expertice in the manipulation and measurement of single-molecule electron transport properties, as well as in the processing and addressing of molecules on different supports.
    Accounts of Chemical Research 02/2015; · 24.35 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The use of the [Fe(III) (AA)(CN)4 ](-) complex anion as metalloligand towards the preformed [Cu(II) (valpn)Ln(III) ](3+) or [Ni(II) (valpn)Ln(III) ](3+) heterometallic complex cations (AA=2,2'-bipyridine (bipy) and 1,10-phenathroline (phen); H2 valpn=1,3-propanediyl-bis(2-iminomethylene-6-methoxyphenol)) allowed the preparation of two families of heterotrimetallic complexes: three isostructural 1D coordination polymers of general formula {[Cu(II) (valpn)Ln(III) (H2 O)3 (μ-NC)2 Fe(III) (phen)(CN)2 {(μ-NC)Fe(III) (phen)(CN)3 }]NO3 ⋅7 H2 O}n (Ln=Gd (1), Tb (2), and Dy (3)) and the trinuclear complex [Cu(II) (valpn)La(III) (OH2 )3 (O2 NO)(μ-NC)Fe(III) (phen)(CN)3 ]⋅NO3 ⋅H2 O⋅CH3 CN (4) were obtained with the [Cu(II) (valpn)Ln(III) ](3+) assembling unit, whereas three isostructural heterotrimetallic 2D networks, {[Ni(II) (valpn)Ln(III) (ONO2 )2 (H2 O)(μ-NC)3 Fe(III) (bipy)(CN)]⋅2 H2 O⋅2 CH3 CN}n (Ln=Gd (5), Tb (6), and Dy (7)) resulted with the related [Ni(II) (valpn)Ln(III) ](3+) precursor. The crystal structure of compound 4 consists of discrete heterotrimetallic complex cations, [Cu(II) (valpn)La(III) (OH2 )3 (O2 NO)(μ-NC)Fe(III) (phen)(CN)3 ](+) , nitrate counterions, and non-coordinate water and acetonitrile molecules. The heteroleptic {Fe(III) (bipy)(CN)4 } moiety in 5-7 acts as a tris-monodentate ligand towards three {Ni(II) (valpn)Ln(III) } binuclear nodes leading to heterotrimetallic 2D networks. The ferromagnetic interaction through the diphenoxo bridge in the Cu(II) Ln(III) (1-3) and Ni(II) Ln(III) (5-7) units, as well as through the single cyanide bridge between the Fe(III) and either Ni(II) (5-7) or Cu(II) (4) account for the overall ferromagnetic behavior observed in 1-7. DFT-type calculations were performed to substantiate the magnetic interactions in 1, 4, and 5. Interestingly, compound 6 exhibits slow relaxation of the magnetization with maxima of the out-of-phase ac signals below 4.0 K in the lack of a dc field, the values of the pre-exponential factor (τo ) and energy barrier (Ea ) through the Arrhenius equation being 2.0×10(-12) s and 29.1 cm(-1) , respectively. In the case of 7, the ferromagnetic interactions through the double phenoxo (Ni(II) -Dy(III) ) and single cyanide (Fe(III) -Ni(II) ) pathways are masked by the depopulation of the Stark levels of the Dy(III) ion, this feature most likely accounting for the continuous decrease of χM T upon cooling observed for this last compound. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Chemistry - A European Journal 02/2015; · 5.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Five new complexes of formula K4[Pd2(mpba)2] • 4H2O (1), {[K4(H2O)(dmso)][Pd2(mpba)2]} (2), {[Cu(bpca)]4[Pd2(mpba)2]} • 6H2O (3), {[Cu(bpca)]2[Pd(opba)]} • 1.75dmso • 0.25H2O (4), {[Cu(bpca)]2[Pd(opba)]}n • n dmso (5) [H4mpba = 1,3-phenylenebis(oxamic acid), H4opba = 1,2-phenylenebis(oxamic acid), Hbpca = bis(2-pyridylcarbonyl)amide and dmso = dimethylsulfoxide] have been prepared investigated by infrared spectroscopy, thermal analysis, single crystal X-ray diffraction and magnetic susceptibility techniques. The structure of 2 consists of a [Pd2(mpba)2]4− anionic entity where the palladium(II) cations are coordinated by two mpba ligands resulting in a dipalladium(II) unit which acts as a ligand towards potassium(I) cations leading to a neutral three-dimensional network. Compound 3 is a neutral hexanuclear complex where the dinuclear [Pd2(mpba)2]4- unit adopts a tetrakis(bidentate) coordination mode towards four [Cu(bpca)]+ end-cap entities. This compound can be viewed as a ‘dimer of trimers’ in which two CuII-PdII-CuII trinuclear units are connected by two mpba ligands. Compounds 4 and 5 have in common the presence of a [Pd(opba)]2− unit which acts as a bis(bidentate) ligand towards two [Cu(bpca)]+ entities to afford neutral heterotrinuclear CuII-PdII-CuII motifs that are interlinked through weak double (4) and single (5) out-of-plane copper(II) to carbonyl(bpca)-oxygen atoms leading to uniform linear (4) and zigzag (5) chains of heterobimetallic trinuclear units. The investigation of the magnetic properties of 3-5 in 1.9-300 K temperature range reveals the presence of very weak antiferromagnetic interactions between the copper(II) ions. The nature and magnitude of these magnetic interactions are discussed on terms of orbital symmetry considerations.
    Crystal Growth & Design 02/2015; · 4.56 Impact Factor
  • Chemistry - A European Journal 02/2015; · 5.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: One novel two-dimensional coordination polymer of formula [Co(dca)2(atz)2]n (1) resulted from assembling trans-bis(2-amino-1,3,5-triazine)cobalt(II) motifs by dicyanamide spacers. Variable-temperature dc and ac magnetic susceptibility measurements of 1 show that the high-spin cobalt(II) ions act as Single Ion Magnets (SIMs).
    Dalton Transactions 01/2015; 44(7). · 4.10 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Two novel bidimensional coordination polymers, [Co(azbbpy)(4,4'-bipy)0.5(DMF)(NCS)2]·MeOH (1) and [Co(azbbpy)(bpe)0.5(DMF)(NCS)2]·0.25H2O (2), resulted from the assembling of cobalt(II) ions by 1,3-bis(4-pyridyl)azulene, using either 4,4'-bipyridyl or 1,2-bis(4-pyridyl)ethylene as neutral spacers. The cobalt(II) nodes in 1 and 2 act as single-ion magnets (SIMs).
    Inorganic Chemistry 12/2014; · 4.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A new copper(II) complex of formula {[Cu2(H2btc)2(dmf)2]·4dmf}n (1) [H4btc = 1,2,4,5-benzenetetracarboxylic acid, dmf = dimethylformamide] has been synthesised and its structure determined by X-ray diffraction. The structure displays a new square grid of “paddle-wheel” tetracarboxylate-bridged dicopper(II) units with an intradimer copper-copper separation of 2.619(2) Å. The dmf molecules are retained through weak axial coordinative bonds and hydrogen bonding interactions with the carboxylic groups of the porous neutral network of 44 net topology. The magnetic behaviour of 1 corresponds to a strong antiferromagnetic coupling within each dicopper(II) unit (J = –343 cm-1 with the Hamiltonian being defined by H = -JS1·S2). Complex 1 does not adsorb N2 but it exhibits certain absorption of CO2 with a hysteretic desorption behaviour typical of flexible MOFs.
    Polyhedron 12/2014; 87:220-225. · 2.05 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The molecular-programmed approach based on the use as ligands of tailor-made metalloligands containing stable six-coordinate rhenium(IV) as paramagnetic centers is presented in this review article. A relatively large amount of spin density is covalent-delocalized away from the rhenium to the peripheral atoms of the ligands in the case of the Re(IV) metalloligands, as shown by polarized neutron diffraction experiments and density functional theory calculations. This feature accounts for the significant through space-magnetic interactions that occur in most of its mononuclear species and more interestingly it also explains the strengthening of the magnetic interactions in the heterometallic Re(IV)-X-3d units respect to the 3d’-X-3d ones, X being a mono- or polyatomic bridging ligand. The complexing ability of the mononuclear Re(IV) species having halo- and pseudohalogeno, cyanide and dicarboxylate groups as peripheral ligands towards either fully solvated metal ion or partially blocked metal complexes allowed the rational preparation of heterometallic compounds with controlled dimensionality and interesting magnetic properties. The variety and a priori easy functionalization of the peripheral donors of these stable Re(IV) precursors, together with their potential bridging ability make them very promising candidates to create multifunctional molecule-based magnetic materials in a very near future.
    Coordination Chemistry Reviews 11/2014; · 12.10 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: New bis(oxamato)palladate(II) complexes, [Pd(H2O)4][Pd(2,6-Me2pma)2]·2H2O (1), (n-Bu4N)2[Pd(2,6-Me2pma)2]·2H2O (2a), and (n-Bu4N)2[Pd(2,6-Me2pma)2]·2CHCl3 (2b) (2,6-Me2pma = N-2,6-dimethylphenyoxamate and n-Bu4N+ = tetra-n-butylammonium), have been synthesized and the structures of 1 and 2b characterized by single-crystal X-ray diffraction. Complex 1 is a double salt constituted by tetraaquapalladium(II) cations and bis(oxamato)palladate(II) anions interlinked by hydrogen bonds. The palladium(II) ions in 1 are four-coordinate with two oxygens and two nitrogens from two fully deprotonated oxamate ligands (anion), and four water molecules (cation) building centrosymmetric square-planar surroundings. Centrosymmetric bis(oxamato)palladate(II) anions occur in 2b as in 1, the charge balance in this compound being ensured by the bulky n-Bu4N+. The catalytic role of 1 and 2a for the Suzuki reaction has been investigated by using a series of aryl iodide/bromide derivatives in the conventional organic medium dimethylformamide. The tetraaquapalladium(II) unit in 1 appears to be active in the catalytic Suzuki cross-coupling reactions, but it readily decomposes to inactive palladium black.
    Journal of Coordination Chemistry 11/2014; 67(23-24). · 2.22 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Graphical abstract The complex formation of Co(II) and Cu(II) ions with the monoethyl ester derivative of the N-(4-carboxyphenyl)oxamic acid yielded different coordination polymers whose structures and variable-temperature magnetic study are presented here.
    Polyhedron 10/2014; 81:105–114. · 2.05 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Two new dinuclear copper(II) metallacyclophanes with 1,4-disubstituted 9,10-anthraquinonebis(oxamate) bridging ligands are reported that can reversibly take and release electrons at the redox-active ligand and metal sites, respectively, to give the corresponding mono- and bis(semiquinonate and/or catecholate) CuII2 species and mixed-valent CuII/CuIII and high-valent CuIII2 ones. Density functional calculations allow us to give further insights on the dual ligand- and metal-based character of the redox processes in this novel family of antiferromagnetically coupled di- copper(II) anthraquinophanes. This unique ability for charge storage could be the basis for the development of new kinds of molecular spintronic devices, referred to as molecular magnetic capacitors (MMCs).
    Chemistry - A European Journal 09/2014; · 5.93 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The six-coordinate cobalt(II) complex of formula [Co(tppz)2](tcm)2 exhibits a thermally induced spin-crossover behavior from a high spin (S = (3)/2) at higher temperatures to a low spin (S = (1)/2) at lower temperatures, with the low-spin phase being achieved at T ≤ 200 K.
    Inorganic Chemistry 09/2014; · 4.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Single crystals of the mononuclear bis-oxamate nickel(II) complex [Ni(bipy)(H 2 edpba)]·dmso (1) are obtained by reacting [Ni(bipy)Cl 2 ]·H 2 O and the flexible K 2 (H 2 edpba) ligand [ b i p y = 2 , 2 ′ -b i p y r i d i n e ; H 4 e d p b a = N , N ′ -2 , 2 ′ -ethylenediphenylenebis(oxamic acid)]. The reaction of 1 with copper(II) ions resulted in two products in which the replacement of the nickel(II) ion by copper(II) took place: the chain compound [Cu(bipy)(H 2 edpba)] n ·3nH 2 O·ndmso [dmso = dimethyl sulfoxide] (2) and the analogous chain compound without dmso crystallization molecules [Cu(bipy)(H 2 edpba)] n ·1.5nH 2 O (3a) in its polycrystal-line form. The reaction of [Cu(bipy)Cl 2 ] and K 2 (H 2 edpba) yielded single crystals of [Cu(bipy)(H 2 edpba)] n ·1.5nH 2 O (3b). The H 2 edpba 2− ligand exhibits the anti conformation in 1, 2, and 3b, but it adopts different coordination modes: terminal bis-bidentate (1) and bridging bis-bidentate (2 and 3b) through the two pairs of carbonyl-oxygen atoms of the two oxamate arms. Magnetic susceptibility measurements carried out on a polycrystalline sample of 3b in the temperature range 1.9−295 K showed the occurrence of very weak intrachain antiferromagnetic interactions [J = −0.40 cm −1 , the Hamiltonian being defined as H = −J ∑ i S i ·S i+1 ], in agreement with the large values of the copper−copper separation [8.308(3) Å]. ■ INTRODUCTION The control of supramolecular architectures by handling the molecules in the solid state is one of the major challenges faced by chemists working with crystal engineering. Because the single crystal is a supramolecular structure by design, 1−4 the control of several parameters that lead to the crystallization of the desired product involves clever strategies and many trials, ranging from the choice of the appropriate building blocks to the control of the conditions for synthesis. 5−10 The effective manipulation of the solid state covalent interactions and supramolecular forces into the crystal (i.e., van der Waals interactions, hydrogen bonds, and π−π stacking) is desired by synthetic chemists dealing with crystal engineering. The literature is enriched by several publications full of notable examples in this field to guide synthetic chemists. 11−15
    Crystal Growth & Design 09/2014; 14(11). · 4.56 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Two new trinuclear copper(ii) complexes without end-capping ligands, (Bu4N)2[Cu(dmso)2{Cu(dnopba)(dmso)}2] () and (Bu4N)2[Cu(dmso)2{Cu(dcopba)(dmso)}2] () [dnopba = 4,5-dinitro-ortho-phenylenebis(oxamate), dcopba = 4,5-dichloro-ortho-phenylenebis(oxamate), Bu4N(+) = tetra-n-butylammonium and dmso = dimethylsulfoxide], were synthesized and their structures were determined by single crystal X-ray diffraction. The crystal structures of and consist of two outer bis(oxamato)(dmso)cuprate(ii) units which act as bidentate ligands toward a trans-bis(dmso)copper(ii) inner entity leading to centrosymmetric tricopper(ii) complexes with copper-copper separations across the oxamate bridges of 5.1916(3) () and 5.1776(3) Å (). The peripheral copper(ii) ions in and are five-coordinate in somewhat distorted square pyramidal environments with a dmso molecule filling the apical position whereas the inner copper(ii) ion is six-coordinate in an elongated octahedral environment with two dmso molecules in the axial sites. The investigation of their magnetic properties in the temperature range 2.0-300 K shows the occurrence of a strong intramolecular antiferromagnetic coupling between the copper(ii) ions through the oxamate bridges [J1 = -296(1) () and -334(1) cm(-1) (), the Hamiltonian being defined as Ĥ = -J1(ŜCu2·ŜCu1 + ŜCu2·ŜCu1')], which leads to a low-lying spin doublet at low temperatures. Density functional theory calculations (DFT) have been used to substantiate these magnetic couplings and also to analyse the influence exerted on these interactions by the type of substituent at the 4,5-positions from the phenylene ring of the bis(oxamate) ligand.
    Dalton Transactions 08/2014; · 4.10 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This work presents a series of layered systems based on phenylmalonate-containing copper(II) complexes and different coligands. Eight compounds [Cu(L)(Phmal)]n where L = pyrimidine (pym, 1) pyrazine (pyz, 2), 3-cyanopyridine (3-CNpy, 3), 4-cyanopyridine (4-CNpy, 4), 3-fluoropyridine (3-Fpy, 5), 3-chloropyridine (3-Clpy, 6), 3-bromopyridine (3-Brpy, 7) and 3-iodopyridine (3-Ipy, 8), have been synthesized and magneto-structurally characterized. The coligands selected not only modify the coordination environment of the metal ion, blocking or extending the polymerization, but also interact with the phenyl ring of the phenylmalonate ligand and dramatically affect the crystal packing through weak interactions. The crystallographic analysis reveals that compounds 1–8 present a corrugated square grid of carboxylate bridged copper(II) atoms where the pyridine ligands are alternatively located above and below each layer and, at the same time, inversely to the position of the phenyl group of the Phmal ligand. It is important to note that the pym and pyz ligands in 1 and 2 do not act as bridges between two copper atoms, whereas weak interactions between the cyano groups are also present in the structures of the complexes 3 and 4. The increase of the Van der Waals radius of the halogen along the series 5–8 accounts for the increase of the interlayer separation. Variable-temperature magnetic susceptibility measurements show the occurrence of different magnetic behaviours. Weak interactions are expected for the anti–syn carboxylate bridge in the out-of-plane configuration, that can be either ferro- or antiferromagnetic. Therefore, in this manuscript we shed light on the influence of the magneto-structural relationship in these square grid layered Cu(II) complexes.
    CrystEngComm 08/2014; 16(35). · 3.86 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Six new heterometallic cobalt(II)-lanthanide(III) complexes of formulas [Ln(bta)(H2O)2]2[Co(H2O)6]·10H2O [Ln = Nd(III) (1) and Eu(III) (2)] and [Ln2Co(bta)2(H2O)8]n·6nH2O [Ln = Eu(III) (3), Sm(III) (4), Gd(III) (5), and Tb(III) (6)] (H4bta = 1,2,4,5-benzenetretracaboxylic acid) have been synthesized and characterized via single-crystal X-ray diffraction. 1 and 2 are isostructural compounds with a structure composed of anionic layers of [Ln(bta)(H2O)2]n(n-) sandwiching mononuclear [Co(H2O)6](2+) cations plus crystallization water molecules, which are interlinked by electrostatic forces and hydrogen bonds, leading to a supramolecular three-dimensional network. 3-6 are also isostructural compounds, and their structure consists of neutral layers of formula [Ln2Co(bta)2(H2O)8]n and crystallization water molecules, which are connected through hydrogen bonds to afford a supramolecular three-dimensional network. Heterometallic chains formed by the regular alternation of two nine-coordinate lanthanide(III) polyhedra [Ln(III)O9] and one compressed cobalt(II) octahedron [Co(II)O6] along the crystallographic c-axis are cross-linked by bta ligands within each layer of 3-6. Magnetic susceptibility measurements on polycrystalline samples for 3-6 have been carried out in the temperature range of 2.0-300 K. The magnetic behavior of these types of Ln(III)-Co(II) complexes, which have been modeled by using matrix dagonalization techniques, reveals the lack of magnetic coupling for 3 and 4, and the occurrence of weak antiferromagnetic interactions within the Gd(III)-Gd(III) (5) and Tb(III)-Tb(III) (6) dinuclear units through the exchange pathway provided by the double oxo(carboxylate) and double syn-syn carboxylate bridges.
    Inorganic Chemistry 06/2014; · 4.79 Impact Factor
  • CrystEngComm 05/2014; · 3.86 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel cobalt(II) complex of formula [Co2(cbut)(H2O)3]n (1) (H4cbut = 1,2,3,4-cyclobutanetetracarboxylic acid) has been synthesized under hydrothermal conditions and its crystal structure has been determined by means of synchrotron radiation and neutron powder diffraction. The crystal structure of 1 consists of layers of cobalt(II) ions extending in the bc-plane which are pillared along the crystallographic a-axis through the skeleton of the cbut(4-) ligand. Three crystallographically independent cobalt(II) ions [Co(1), Co(2), and Co(3)] occur in 1. They are all six-coordinate with four carboxylate-oxygens [Co(1)-Co(3)] and two cis-[Co(1)] or trans-water molecules [Co(2) and Co(3)] building distorted octahedral surroundings. Regular alternating double oxo(carboxylate) [between Co(1) and Co(1a)] and oxo(carboxylate) plus one aqua and a syn-syn carboxylate bridges [between Co(1) and Co(2)] occur along the crystallographic b-axis, the values of the cobalt-cobalt separation being 3.1259(8) and 3.1555(6) Å, respectively. These chains are connected to the Co(3) atoms through the OCO carboxylate along the [01̅1] direction leading to the organic-inorganic bc-layers with Co(1)-OCO(anti-syn)-Co(3) and Co(2)-OCO(anti-anti)-Co(3) distances of 5.750(2) and 4.872(1) Å. The shortest interlayer cobalt-cobalt separation through the cbut(4-) skeleton along the crystallographic a-axis is 7.028(2) Å. Variable-temperature magnetic susceptibility measurements show the occurrence of antiferromagnetic ordering with a Néel temperature of 5.0 K, followed by a field-induced ferromagnetic transition under applied dc fields larger than 1500 Oe. The magnetic structure of 1 has been elucidated at low temperatures in zero field by neutron powder diffraction measurements and was found to be formed by ferromagnetic chains running along the b-axis which are antiferromagnetically coupled with the Co(3) ions through the c-axis giving rise to noncompensated magnetic moments within each bc-layer (ferrimagnetic plane). The occurrence of an antitranslation operation between these layers produces a weak interlayer antiferromagnetic coupling along the a-axis which is overcome by dc fields greater than 1500 Oe resulting in a phase transition toward a ferromagnetic state (metamagnetic behavior).
    Inorganic Chemistry 05/2014; · 4.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel series of heteroleptic copper(II) compounds of formulas {[Cu2(μ-H2O)(μ-pz)2(μ-bpm)(ClO4)(H2O)]ClO4·2H2O}n (1), {[Cu2(μ-H2O)(μ-3-Mepz)2(μ-bpm)](ClO4)2·2H2O}n (2), and {[Cu2(μ-OH)(μ-3,5-Me2pz)(μ-bpm)(H-3,5-Me2pz)2](ClO4)2}n (3) [bpm = 2,2'-bipyrimidine, Hpz = pyrazole, H-3-Mepz = 3-methylpyrazole, and H-3,5-Me2pz = 3,5-dimethylpyrazole] have been synthesized and structurally characterized by X-ray diffraction methods. The crystal structures of 1 and 2 consist of copper(II) chains with regular alternating bpm and bis(pyrazolate)(aqua) bridges, whereas that of 3 is made up of copper(II) chains with regular alternating bpm and (pyrazolate)(hydroxo) bridges. The copper centers are six- (1) or five-coordinate (2) in axially elongated, octahedral (1) or square-pyramidal (2) environments in 1 and 2, whereas they are five-coordinate in distorted trigonal-bipyramidal surroundings in 3. The values of the copper-copper separations across the bpm/pyrazolate bridges are 5.5442(7)/3.3131(6) (1), 5.538(1)/3.235(1) (2), and 5.7673(7)/3.3220(6) Å (3). The magnetic properties of 1-3 have been investigated in the temperature range of 25-300 K. The analysis of their magnetic susceptibility data through the isotropic Hamiltonian for an alternating antiferromagnetic copper(II) chain model [H = -J∑i=1-n/2 (S2i·S2i-1 + αS2i·S2i+1), with α = J'/J and Si = SCu = 1/2] reveals the presence of a strong to moderate antiferromagnetic coupling through the bis(pyrazolate)(aqua) [-J = 217 (1) and 215 cm(-1) (2)] and (pyrazolate)(hydroxo) bridges [-J = 153 cm(-1) (3)], respectively, whereas a strong to weak antiferromagnetic coupling occurs through the bis-bidentate bpm [-J' = 211 (1), 213 (2), and 44 cm(-1) (3)]. A simple orbital analysis of the magnetic exchange interaction within the bpm- and pyrazolate-bridged dicopper(II) fragments of 1-3 visualizes the σ-type pathways involving the (dx(2)-y(2)) (1 and 2) or d(z(2)) (3) magnetic orbitals on each metal ion, which account for the variation of the magnetic properties in these three novel examples of one-dimensional copper(II) compounds with regular alternating intrachain antiferromagnetic interactions.
    Inorganic Chemistry 05/2014; · 4.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: New examples of cyanido-bearing cobalt(III/II) complexes have been obtained by treatment of CoCl2·6H2O with bidentate nitrogen donors and potassium cyanide in a methanol/water mixture. Depending on the chelating ligand, the cobalt(III) complexes PPh4[Co(en)(CN)4] (1, en = ethylenediamine), PPh4[Co(ampy)(CN)4]·1.5H2O [2, ampy = 2-(aminomethyl)pyridine], and PPh4[Co(phen)(CN)4]·CH3OH·0.25H2O (3, phen = 1,10-phenanthroline) and the cobalt(II) complex PPh4[Co(dmphen)(CN)3]·3H2O (4, dmphen = 2,9-dimethyl-1,10-phenanthroline) were obtained. The complexes were characterized by single-crystal X-ray diffraction and variable-temperature magnetic measurements. They are all mononuclear species with six-coordinate cobalt(III) (1–3) and five-coordinate cobalt(II) centers (4), and two nitrogen atoms from each bidentate ligand (1–4) and four (1–3) or three cyanide carbon atoms (4) build somewhat distorted octahedral (1–3) or square-pyramidal (4) surroundings. Complexes 1–3 are diamagnetic cobalt(III) compounds, whereas 4 is a low-spin cobalt(II) complex that exhibits Curie behavior in the temperature range 10–300 K. The g values of the X-band electron paramagnetic resonance (EPR) spectrum of 4 both in the solid state and in dichloromethane solution at 4.0 K (g⟂ = 2.28 > g∥ = 2.0) reveal that its unpaired electron is defined by a d-type orbital. Complexes 1–4 can be viewed as new metalloligands for metal assemblies.
    Berichte der deutschen chemischen Gesellschaft 05/2014; · 2.97 Impact Factor

Publication Stats

12k Citations
2,086.00 Total Impact Points

Institutions

  • 1980–2014
    • University of Valencia
      • • Instituto de Ciencia Molecular (ICMol)
      • • Inorganic Chemistry
      • • Facultad de Química
      Valenza, Valencia, Spain
  • 2013
    • Federal University of Minas Gerais
      • Departamento de Química
      Belo Horizonte, Estado de Minas Gerais, Brazil
  • 1994–2013
    • Pierre and Marie Curie University - Paris 6
      • Institut Parisien de Chimie Moléculaire (IPCM)
      Lutetia Parisorum, Île-de-France, France
  • 2001–2012
    • University of the Republic, Uruguay
      • Facultad de Química
      Montevideo, Departamento de Montevideo, Uruguay
  • 2000–2012
    • Universidad de La Laguna
      • • Department of Basic Physics II
      • • Facultad de Física
      San Cristóbal de La Laguna, Canary Islands, Spain
  • 2011
    • Syracuse University
      • Department of Chemistry
      Syracuse, NY, United States
  • 2010
    • Polytech Paris-UPMC
      Lutetia Parisorum, Île-de-France, France
  • 2004–2010
    • University of Bucharest
      • Faculty of Chemistry
      Bucharest, Bucuresti, Romania
  • 2008
    • Justus-Liebig-Universität Gießen
      • Institut für Anorganische und Analytische Chemie
      Gießen, Hesse, Germany
  • 1996–2008
    • Università della Calabria
      • Dipartimento di Chimica e Tecnologie Chimiche - CTC
      Rende, Calabria, Italy
  • 2007
    • University of Concepción
      • Facultad de Ciencias Químicas
      Concepción, Region del Biobio, Chile
  • 2006
    • Nottingham Trent University
      Nottigham, England, United Kingdom
  • 2001–2004
    • Università degli Studi della Basilicata
      Potenza, Basilicate, Italy
  • 1991–2001
    • University of Barcelona
      • • Departament de Química Inorgànica
      • • Department of Crystallography, Mineralogy and Mineral Deposits
      Barcelona, Catalonia, Spain
  • 1999
    • Philipps University of Marburg
      Marburg, Hesse, Germany
  • 1983–1984
    • Université Paris-Sud 11
      • Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO)
      Orsay, Île-de-France, France