Miguel Julve

University of Valencia, Valenza, Valencia, Spain

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Publications (541)2295.75 Total impact

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    ABSTRACT: Three palladium(II) complexes of formula (n-Bu4N)2[Pd(4-Fpma)2] (1), (n-Bu4N)2[Pd(4-Clpma)2]·4H2O (2) and (n-Bu4N)2[Pd(4-Brpma)2]·4H2O (3) [n-Bu4N+ = tetra-n-butylammonium cation, 4-Fpma = N-4-fluorophenyloxamate, 4-Clpma = N-4-chlorophenyloxamate and 4-Brpma = N-4-bromophenyloxamate] have been prepared and their structures determined by single crystal X-ray diffraction. Each palladium(II) ion in 1–3 is four-coordinate with two oxygen and two nitrogen atoms from two fully deprotonated oxamate ligands building PdO2N2 square planar surroundings, the oxamate ligands exhibiting trans (1 and 2) and cis (3) dispositions. The fluoro substituent and the organic counterion in 1 are involved in C–H⋯F type interactions whereas the anionic complex assembly is driven by C–H⋯Ooxamate interactions. The structures of 2 and 3 shed light on the effects of the different chemical nature of chloro and bromo substituents on the C–H⋯X interactions joined to hydrogen bonds involving oxamate oxygen atoms and crystallization water molecules. The complex anions in 2 are interlinked by water chains to afford a supramolecular two-dimensional network where Ow⋯Ow, Ow⋯Ooxamate and Ow⋯Cl hydrogen bonds are involved. The reduction of the polarity of C–Br bonds with respect to C–X (X = F, Cl) is very likely to be one of the key reasons allowing for the cis-arrangement of the two 4-Brpma ligands around each palladium(II) ion of the anionic complex in 3 in water. These units are interconnected by hydrogen bonds between the peripheral oxamato-oxygens and a four-membered ring of water molecules leading to supramolecular cationic chains extending along the crystallographic a axis.
    Full-text · Article · Jan 2016 · RSC Advances
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    ABSTRACT: Four new bis(oxamato)palladate(II) complexes of formula (n-Bu4N)2[Pd(2,4,6-Me3pma)2]·2CH3CN (1), (n-Bu4N)2[Pd(2,4,6-Me3pma)2]·2CH3CONH2 (2) and (n-Bu4N)4[Pd(H2O)4][Pd(4-Xpma)2]3·2CH3CONH2 with X = Br (3) and Cl (4) (2,4,6-Me3pma = N-2,4,6-trimethylphenyloxamate, 4-Brpma = N-4-bromophenyloxamate, N-4-chlorophenyloxamate and n-Bu4N+ = tetra-n-butylammonium) have been obtained and characterized by single crystal X-ray diffraction. All of them contain bis(oxamato)palladate(II) anions and bulky n-Bu4N+ cations, but compounds 3 and 4 have also the out of the ordinary [Pd(H2O)4]2+ inorganic cation. Acetonitrile and appealing acetamide are present as lattice molecules in compounds (1) and (2-4), respectively. While 1 was prepared in a neutral solution, species 2-4 were obtained in a basic medium. The acetamide molecules are the natural consequence of the acetonitrile hydration reaction during the oxamate-palladate(II) complexation. Interestingly, the use of a different oxamate ligand supports (through a molecular-recognition interaction) the structural grasping of the [Pd(H2O)4]2+ species, which can be considered as a reaction intermediate for the nitrile hydration.
    Full-text · Article · Jan 2016
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    ABSTRACT: Two tetranuclear cubane-like nickel(II) complexes of formula [Ni4(CH3O)4(L1)4(CH3OH)4] (1) and [Ni4(CH3O)4(L2)4(CH3OH)4] (2) (HL1 = 2-hydroxybenzaldehyde and HL2 = 2-hydroxy-5-methylbenzaldehyde) have been prepared by the reaction of NiCl2 . 6H2O with methanolic solutions of HL1 and HL2 in the presence of triethylamine at room temperature. Complexes 1 and 2 have been characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. The X-ray crystal structure analysis revealed that 1 and 2 have a cubane-type structural topology with four Ni(II) ions and four methoxo-oxygen atoms regularly alternating at the corners. Each metal ion in 1 and 2 is six-coordinate in a distorted octahedral geometry defined by three bridging methoxo-oxygens, one oxygen atom from a methanol molecule and two oxygen atoms from the bidentate L1 (1)/L2 (2) ligands. The magnetic properties of 1 and 2 were investigated in the temperature range 1.9-300 K. They are indicative of an overall ferromagnetic behaviour, the decrease in the very low temperature region being due to zero-field splitting and intermolecular interactions. A detailed analysis of the magnetic data of 1 and 2 assuming an idealized D2d symmetry for the Ni4O4 unit shows the occurrence of a low-lying spin nonet and two opposite magnetic interactions, one being ferromagnetic [Ja = +12.6 (1) and +10.5 cm-1 (2)] and the other antiferromagnetic [Jb = -4.10 (1) and -2.10 cm-1 (2)]. These values fit well the linear correlation between the exchange coupling parameter (J) and the Ni-O-Ni angle () which was established for Ni4O4 cubane motifs in previous works.
    No preview · Article · Jan 2016 · RSC Advances
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    ABSTRACT: A novel series of copper(II) coordination polymers [Cu2(O2CC8H9)4(pyz)]n (1), [Cu2(O2CC8H9)4(dps)]n (2), {[Cu(O2CC8H9)2(dps)(H2O)]·H2O}n (3), {[NaCu(O2CC8H9)2(bpm)(NO3)]·H2O}n (4), and [Cu4(O2CC8H9)6(OH)2(bpp)2]n (5) [O2CC8H9− = 3-phenylpropionate anion, pyz = pyrazine, dps = di(4-pyridyl)sulfide, bpm = 2,2′-bipyrimidine, and bpp = 1,3-bis(4-pyridyl)propane] have been synthesized and magneto-structurally investigated. Compounds 1 and 2 belong to a large group of copper(II) carboxylates where bis-monodentate pyz (1) and dps (2) ligands connect the paddle-wheel [CuII2(μ-O2CC8H9)4] units leading to alternating copper(II) chains. The structure of 3 consists of uniform chains of trans-[CuII(O2CC8H9)2] units linked by the bis-monodentate dps ligand. Compound 4 consists of heterobimetallic chains where [NaI2CuII2(μ-O2CC8H9)4(NO3)2] units are doubly bridged by bis-bidentate bpm ligands. Compound 5 is also a chain compound whose structure is made up by tetranuclear [CuII4(μ3-OH)2(μ-O2CC8H9)4(O2CC8H9)2] units which are doubly bridged by bis-monodentate bpp ligands. The magnetic properties were investigated in the temperature range 1.8–300 K. Strong antiferromagnetic interactions across the quadruple syn–syn carboxylate are observed in 1 and 2 [J = −378 (1) and −348 cm−1 (2)] whereas a weak ferromagnetic coupling through the double out-of-plane oxo(carboxylate) bridge occurs in 4 [J = +2.66 cm−1], the spin Hamiltonian being defined as H = −JS1·S2 with S1 = S2 = SCu = 1/2. A quasi Curie law is observed for 3 (θ = −0.36 cm−1), the bis-monodentate dps ligand being a very poor mediator of magnetic interactions. The analysis of the magnetic properties of 5 is quite complex because of the presence of two crystallographically independent tetracopper(II) units with single-μ-hydroxo, di-μ-hydroxo, μ3-hydroxo and single-μ-hydroxo plus double syn,syn carboxylate bridges in each one. The nature and values of the magnetic couplings for 5 obtained by fitting (intermediate, strong and weak antiferromagnetic interactions for the three former exchange pathways respectively, and intermediate ferromagnetic interactions for the latter one) were substantiated by DFT type calculations.
    Full-text · Article · Dec 2015 · Dalton Transactions
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    ABSTRACT: The reaction of the starting materials [ReIIICl3(MeCN)(PPh3)2] or [ReVOCl3(PPh3)2] with 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) in acetonitrile yielded the Re(iii) complex [ReCl3(tppz)]·MeCN (1). This complex crystallizes in the monoclinic space group P21/n and its crystal structure consists of neutral mononuclear entities with meridional geometry of the chloride ligands, and the six-coordination of the Re(iii) ion being completed by the tridentate tppz ligand. Each metal centre exhibits a highly distorted octahedral coordination with Re-Cl and Re-Ntppz bond lengths covering the ranges 2.3590(9)-2.3606(8) and 1.971(2)-2.096(2) Å, respectively. The magnetic properties of 1 have been investigated in the temperature range 1.9-290 K. They are characteristic of a six-coordinate Re(iii) mononuclear complex with d4 low-spin (3T1 ground state). The magnetic data of 1 are discussed through a deep analysis of the influence of the ligand-field, spin-orbit coupling, tetragonal distortion and covalency effects. The second-order Zeeman effect between the non-magnetic ground state (MJ = 0) and higher energy levels (MJ ≠ 0) determines the magnetic susceptibility of 1, the value of the temperature-independent paramagnetic susceptibility being 3378 × 10-6 cm3 mol-1. This value compares well with those reported for other structurally characterized Re(iii) complexes.
    Full-text · Article · Nov 2015 · RSC Advances
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    ABSTRACT: The use of the cyanide-bearing complexes PPh4[CoIII(4,4′-dmbipy)(CN)4] and PPh4[CoII(dmphen)(CN)3] as metalloligands towards [Mn(salen)(H2O)]ClO4 affords one-dimensional coordination polymers with the formulas {[MnIII(salen)(μ-NC)2CoIII(4,4-dmbipy)(CN)2]·H2O}n (1) and {[MnIII(salen)(μ-NC)2CoIII(dmphen)(CN)2]}n (2) [PPh4+ = tetraphenylphosphonium cation, 4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine, dmphen = 2,9-dimethyl-1,10-phenanthroline and H2salen = N,N′-ethylenebis(salicylideneimine)]. Compounds 1 and 2 were structurally characterized. Their structures consist of neutral chains with regular alternating [Mn(salen)]+ and [CoIII(4,4′-dmbipy)(CN)4]- (1)/[CoIII(dmphen)(CN)4]- (2) moieties, the latter ones acting as bis-monodentate ligands towards the Mn(iii) units through two of their four cyanide groups. During the synthesis, the cobalt(ii) ion of the starting [CoII(dmphen)(CN)3]- metalloligand is oxidized to Co(iii) and it takes an additional cyanide ligand to transform into {CoIII(dmphen)(CN)4} in 2. Magnetic studies have been carried out on 1 and 2 in the temperature range 1.9-300 K which yielded local negative zero-field splitting parameters of -3.26 (1) and -4.38 cm-1 (2). Frequency-dependent alternating current susceptibility signals under an external applied magnetic field (dc) were clearly observed for 1 and 2 indicating slow magnetic relaxation, that is, Single Ion Magnet (SIM) behaviour. The energy barriers (Ea) to reverse the magnetization direction under an applied dc magnetic field of 2000 Oe were 12.0(2) (1) and 9.4(3) cm-1 (2), whereas the values of the pre-exponential factor (τo) were 1.40(2) × 10-8 (1) and 2.5(2) × 10-8 s (2).
    Full-text · Article · Nov 2015 · RSC Advances
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    ABSTRACT: The self-assembly process between the binuclear [Cu2(HL)(L)]− complex and the manganese(II) ion affords a two-dimensional coordination polymer of formula [Mn{Cu2(HL)(L)}2(H2O)2]n (1) (H3L = 3-hydroxyiminomethylsalicylic acid) where parallel ladder-like motifs of defective double cubanes of bis(phenoxo)dicopper(II) units as rods and anti-syn carboxylato bridges as rungs act as ligands towards tetraaqua-manganese(II) entities through the deprotonated oxime groups. The topology of 1 is compared with the one of another compound, [Mn{Cu2(HL)(L)}2(H2O)4]·4H2O·2DMF (1′) which was obtained in different conditions by Okawa et al. (J. Chem. Soc., Dalton Trans. (2001) 3119). Magnetic susceptibility measurements of 1 in the temperature range 2.0–300 K are practically determined by the occurrence of a very large antiferromagnetic coupling between the two copper(II) ions through the double phenoxido bridge [J = −765(5) cm−1, the spin Hamiltonian being defined as H = −JSCu1·SCu2], a value which is as expected in the light of a recent magneto-structural correlation for bis(phenoxido)dicopper(II) complexes.
    No preview · Article · Nov 2015
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    ABSTRACT: We report on a novel manganese(III)-porphyrin complex with the formula [Mn(III) (TPP)(3,5-Me2 pyNO)2 ]ClO4 ⋅CH3 CN (2; 3,5-Me2 pyNO=3,5-dimethylpyridine N-oxide, H2 TPP=5,10,15,20-tetraphenylporphyrin), in which the Mn(III) ion is six-coordinate with two monodentate 3,5-Me2 pyNO molecules and a tetradentate TPP ligand to build a tetragonally elongated octahedral geometry. The environment in 2 is responsible for the large and negative axial zero-field splitting (D=-3.8 cm(-1) ), low rhombicity (E/|D|=0.04) of the high-spin Mn(III) ion, and, ultimately, for the observation of slow magnetic-relaxation effects (Ea =15.5 cm(-1) at H=1000 G) in this rare example of a manganese-based single-ion magnet (SIM). Structural, magnetic, and electronic characterizations were carried out by means of single-crystal diffraction studies, variable-temperature direct- and alternating-current measurements and high-frequency and -field EPR spectroscopic analysis followed by quantum-chemical calculations. Slow magnetic-relaxation effects were also observed in the already known analogous compound [Mn(III) (TPP)Cl] (1; Ea =10.5 cm(-1) at H=1000 G). The results obtained for 1 and 2 are compared and discussed herein.
    Full-text · Article · Oct 2015 · Chemistry - A European Journal
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    ABSTRACT: Two novel FeII–ReIV compounds of general formula [FeII(DEA)6][ReIVX6] where DEA = diethylacetamide and X = Cl (1) and Br (2) have been prepared and magnetostructurally characterised. Complexes 1 and 2 are isomorphic ionic salts that crystallise in the trigonal crystal system with space group R(−3). The rhenium(IV) ion in 1 and 2 is six-coordinate with six chloro (1) or bromo (2) ligands building a regular octahedral chromophore. The FeII ion is also six-coordinate, and bonded to six oxygen atoms from six DEA molecules. [FeII(DEA)6]2+ cations and [ReIVX6]2− anions alternate in the crystal lattice of 1 and 2 generating supramolecular structures whose magnetic properties are dominated by the high anisotropy of the six-coordinate iron(II) and rhenium(IV) ions. Variable-temperature magnetic susceptibility data of 1 and 2 are well reproduced by a model of isolated S = 2 (FeII) and S = 3/2 (ReIV) centres with high values of the local zero-field splitting. 1 and 2 are the first examples of hexahalorhenate(IV) salts incorporating FeII complex cations to have been magnetostructurally investigated.
    No preview · Article · Sep 2015 · Polyhedron
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    ABSTRACT: Five bis(oxamato)palladate(II) complexes of the formulae (n-Bu4N)2[Pd(4-Fpma)2] (1), (n-Bu4N)2[Pd(4-Clpma)2] (2), (n-Bu4N)2[Pd(4-Brpma)2] (3), (n-Bu4N)2[Pd(4-Brpma)2]·H2O (3a), (n-Bu4N)2[Pd(4-MeOpma)2] (4) and (n-Bu4N)2[Pd(4-Isopma)2] (5) (n-Bu4N+ = tetra-n-butylammonium, 4-Fpma = N-4-fluorophenyloxamate, 4-Clpma = N-4-chlorophenyloxamate, 4-Brpma = N-4-bromophenyloxamate, 4-MeOpma = N-4-methoxyphenyloxamate and 4-isopma = N-4-isopropylphenyloxamate) have been easily prepared and characterized by spectroscopic methods and the crystal structures of two of them (3a and 4) have been determined by single crystal X-ray diffraction. Each palladium(II) ion in 3a and 4 is four-coordinate with two oxygen and two nitrogen atoms from two fully deprotonated oxamate ligands building a centrosymmetric square planar PdN2O2 surrounding. The values of the Pd–N and Pd–O bond lengths vary in the ranges 2.034(3)–2.043(4) and 1.999(4)–2.013(3) Å, respectively. The reduced bite of the chelating oxamate ligands [81.3(2)–81.7(1) (3a) and 81.61(7)° (4)] is at the origin of the mean distortion of the ideal square environment. The catalytic role of compounds 1–5 as structurally well-defined precatalysts for the Heck-vinylation of a series of aryl iodide/bromide derivatives in n-Bu4NBr as a benign nonaqueous ionic liquid (i.d. molten salt) has been examined and compared with some commercially available palladium(II/0) complexes. From this study, it appears that the oxamate-containing precatalysts 1–5 are not just ecologically benign, but also highly efficient, easily recoverable and reusable at least eight times without any relevant loss of catalytic activity or leaching from the ionic liquid medium.
    Full-text · Article · Sep 2015
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    ABSTRACT: Two new Re(iv) compounds of formulae H2tppz[ReCl6] () and [Cu(bpzm)2(μ-Cl)ReCl3(μ-ox)Cu(bpzm)2(μ-ox)ReCl3(μ-Cl)]n () [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and bpzm = bis(pyrazolyl-1-yl)methane] have been prepared and their crystal structures determined by X-ray diffraction on single crystals. Compound is a mononuclear species whose structure consists of octahedral hexachlororhenate(iv) anions and diprotonated H2tppz(2+) cations which are arranged in the unit cell as alternating anionic and cationic layers, held together by electrostatic forces. The structure of is made up of alternating [Cu(1)(bpzm)2](2+) and [(ox)ReCl3(μ-Cl)Cu(2)(bpzm)2(μ-Cl)ReCl3(ox)](2-) entities interlinked by oxalate bridges to afford a neutral heterobimetallic chain. The oxalate group adopts the didentate (at Re)/monodentate (at Cu) bridging mode. The magnetic behavior of and has been investigated over the temperature range 1.9-295 K. is a magnetically diluted Re(iv) complex, the relatively large value of the zero-field splitting of the ground level [D = -15.8(2) cm(-1)] accounting for the variation of χMT in the low temperature range. Weak intrachain ferromagnetic interactions between Re(iv) and Cu(ii) through oxalate (J1 = +0.15 cm(-1)) and single chloro (J2 = +4.9 cm(-1)) bridges occur in which are obscured by the large zero-field splitting of the Re(iv) ion (DRe = 42 cm(-1)). In addition, interchain antiferromagnetic interactions are also involved in which are responsible for the metamagnetic behavior observed, the value of the critical dc magnetic field (Hc) being 20 kOe.
    Full-text · Article · Aug 2015 · Dalton Transactions
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    ABSTRACT: Three isostructural compounds of the formula {[M(bipy)(H2O)(H2P2O7)]2·2H2O} [bipy = 2,2'-bipyridine; M = Ni (1), Co (2), Mn (3)] have been isolated from aqueous solutions containing the corresponding metal(II) chloride hydrate with a bipy and sodium pyrophosphate solution in a 1:1:2 molar ratio, and their structures were determined by single-crystal X-ray diffraction. The structures of 1-3 consist of neutral aqua(2,2'-bipyridine)metal(II) dinuclear units bridged by two dihydrogenpyrophosphate groups adopting a bidentate/monodentate mode. Each metal ion in 1-3 is six-coordinate in a distorted octahedral geometry, with the reduced value of the angle subtended by the chelating bipy at the metal ion [79.6(1)° (1), 77.32(7)° (2), and 72.9(1)° (3)] being the main source of this distortion. The values of the intramolecular metal-metal separation are 5.271(1) Å (1), 5.3065(8) Å (2), and 5.371(1) Å (3). Magnetic susceptibility measurements on polycrystalline samples of 1-3 in the temperature range 1.9-300 K shows weak intramolecular ferromagnetic [J = +1.86(2) cm(-1) (1) and +0.25(1) cm(-1) (2)] and antiferromagnetic [J = -0.48(1) cm(-1) (3)] coupling, with the spin Hamiltonian being defined as H = -JSM1·SM1a. This rarely observed coordination mode for dihydrogenpyrophosphate leads to ferromagnetic coupling in complexes of nickel(II) or cobalt(II).
    No preview · Article · Jun 2015 · Inorganic Chemistry
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    ABSTRACT: A relatively large antiferromagnetic interaction between the two chromium(III) ions from the molecular square [{Cr(dmso)3}2{Nb(Cr-O)2(C2O4)2}2] (1) (J = -12.0 cm-1) is mediated by the diamagnetic oxo-Nb(V)-oxo pathway, its nature and magnitude being substantiated by DFT type theoretical calculations
    Full-text · Article · Jun 2015
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    ABSTRACT: The work presented in this review constitutes a successful extension of our group's research on the chemistry and physics of dinuclear copper(II) metallacyclophanes with aromatic polyoxalamide ligands. The design and synthesis of metallacyclic complexes that contain multiple electro- and photoactive (either metal- or ligand-based) spin carriers and the study of their spectroscopic and magnetic properties as well as their redox and photochemical activity are of large interest in the multidisciplinary field of metallosupramolecular chemistry. In doing this, a ligand design approach has been followed which is based on the copper(II)-mediated self-assembly of bis(oxamato) bridging ligands possessing potentially electro- and photoactive, extended π-conjugated aromatic spacers. This strategy benefits from the inherent physical and chemical properties of aromatic organic molecules by functionalizing them with two oxamato donor groups to get dinucleating ligands that are then able to self-assemble with square planar CuII ions affording the targeted oxamato-based dicopper(II) metallacyclophanes. The organic functionalization in this new class of metallacyclic systems constitutes a unique example of ligand design for the supramolecular control of the structure and magnetic properties, as well as the electro- and photochemical activities. This novel class of oxamato-based dicopper(II) metallacyclophanes provides excellent models for the fundamental study on through-ligand long-distance and redox- or photo-triggered electron exchange phenomena, which are two central topics in molecular magnetism and molecular electronics. Using these simple dinuclear metallacyclic complexes as dynamic chemical systems to perform specific and selective tasks under the control of an external (electro- and/or photochemical) stimulus that switches “ON” and “OFF” their electronic (optical and/or magnetic) properties may have an enormous impact in several domains of molecular nanoscience. Hence, oxamato-based dicopper(II) metallacyclophanes appear as very promising candidates to get multifunctional magnetic devices controlling and facilitating the spin communication (“molecular magnetic couplers” and “molecular magnetic wires”) or exhibiting charge storage (“molecular magnetic capacitors”) and bistable spin behavior (“molecular magnetic rectifiers” and “molecular magnetic switches”) for potential applications in information processing and storage in the emerging areas of molecular spintronics and quantum computing. Moreover, because of the potential high affinity for a variety of metal surfaces through the free carbonyl-oxygen atoms of the oxamate groups, they are very appealing candidates for the study of coherent electron transport through single molecules.
    Full-text · Article · Jun 2015 · Coordination Chemistry Reviews
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    ABSTRACT: The novel Re(II) complex NBu4[Re(NO)Br4(Hnic)] (1) and the heterodinuclear compounds [Re(NO)Br4(µ-nic)Ni(dmphen)2]•½CH3CN (2), [Re(NO)Br4(µ-nic)Co(dmphen)2]•½MeOH (3), [Re(NO)Br4(µ-nic)Mn(dmphen)(H2O)2]•dmphen (4), [Re(NO)Br4(µ-nic)Cu(bipy)2] (5) [Re(NO)Br4(µ-nic)Cu(dmphen)2] (5’) (NBu4+ = tetra-n-butylammonium cation, Hnic = 3-pyridinecarboxylic acid, dmphen = 2,9-dimethyl-1,10-phenanthroline, bipy = 2,2’-bipyridine) have been prepared and the structures of 1-5 determined by single crystal X-ray diffraction. The structure of 1 consists of [Re(NO)Br4(Hnic)]- anions and NBu4+ cations. Each Re(II) is six-coordinate with four bromide ligands, a linear nitrosyl group and a nitrogen atom from the Hnic molecule, in a distorted octahedral surrounding. The structures of 2-5 are made up of discrete heterodinuclear Re(II)M(II) units where the fully deprotonated [Re(NO)Br4(nic)]2- entity acts as a didentate ligand through the carboxylate group towards the [Ni(dmphen)2]2+ (2), [Co(dmphen)2]2+ (3), [Mn(dmphen)(H2O)2]2+ (4) and [Cu(bipy)2]2+ (5) fragments, the Re-M separation across the nic bridge being 7.8736(8) (2), 7.9632(10) (3), 7.7600(6) (4) and 8.2148(7) Å (5). The environment of the Re(II) ion in 2-5 is the same as in 1 and all M(II) are six-coordinate in highly distorted octahedral surroundings, the main source of the distortion being due to the reduced bite of the chelating carboxylate. The magnetic properties of 1-5’ were investigated in the temperature range 1,9-300 K. 1 behaves as a quasi magnetically isolated spin doublet with very weak antiferromagnetic interactions through space Br…Br contacts. Its magnetic susceptibility data were successfully modeled through a deep analysis of the influence of the ligand field, spin-orbit coupling, tetragonal distortion and covalence effects as variable parameters. Compounds 2-5’ exhibit weak antiferromagnetic interactions. The intramolecular exchange pathway in this family being discarded because of the symmetry of magnetic orbital of the Re(II) ion (dxy) precludes any spin delocalization on the bridging nic orbitals, the observed magnetic interactions are most likely mediated by - type interactions between the peripheral ligands which occur in them. Only in the case of 4, short through space Br…Br contacts of ca. 4.03 Å (values larger than 5.5 Å in 2, 3 and 5) could be involved in the exchange coupling.
    Full-text · Article · May 2015 · Dalton Transactions
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    ABSTRACT: Two novel ReIV compounds of formula (Hbpym)2[ReIVBr6]·4H2O (1) and (H4biim)[ReIVBr6]·4H2O (2) [Hbpym+ = 2,2′-bipyrimidinium cation and H4biim2+ = 2,2′-biimidazolium dication] have been prepared and magnetostructurally characterized. 1 and 2 exhibit distinct crystal packing, and the presence of weak intermolecular contacts, such as Re-Br···Br-Re (1 and 2), Re-Br···(H2O)···Br-Re (1 and 2), and Re-Br···π···Br-Re (2), lead to different magnetic behaviors. While 1 is antiferromagnetic, 2 is a ferromagnetic compound and indeed the first example of ferromagnetic salt based on the hexabromorhenate(IV) anion. These results suggest a straightforward synthetic route to the preparation of new ferromagnetically coupled ReIV compounds.
    No preview · Article · May 2015 · Crystal Growth & Design
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    ABSTRACT: The synthesis, crystal structure and preliminary magnetic characterization of a new heterobimetallic [MnII5CuII5] wheel containing a flexible bis-oxamate type ligand are described. This decanuclear compound exhibits a relatively strong intra-wheel antiferromagnetic interaction leading to a ground spin state S = 10.
    Full-text · Article · May 2015 · Dalton Transactions
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    ABSTRACT: The synthesis, crystal structure and preliminary magnetic characterization of a new heterobimetallic [MnII5CuII5] wheel containing a flexible bis-oxamate type ligand are described. This decanuclear compound exhibits a relatively strong intra-wheel antiferromagnetic interaction leading to a ground spin state S = 10.
    Full-text · Article · May 2015 · Dalton Transactions
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    ABSTRACT: A new heteroleptic 1D Cu(I)-Re(IV) coordination polymer of the formula {Cu(I)Re(IV)Cl4(μ-Cl)(μ-pyz)[Re(IV)Cl4(μ-bpym)]}n·nMeNO2 (1; pyz = pyrazine, bpym = 2,2'-bipyrimidine) has been prepared through the Cu(I)-mediated self-assembly of two different Re(IV) metalloligands, namely, [ReCl5(pyz)](-) and [ReCl4(bpym)]. 1 consists of chiral branched chains with an overall rack-type architecture displaying photoemission and magnetic ordering. These results constitute a first step toward making new multifunctional magnetic materials based on mixed 3d-5d molecular systems.
    Full-text · Article · May 2015 · Inorganic Chemistry
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    ABSTRACT: The preparation, spectroscopic characterization and X-ray crystal structure of two novel one-dimensional compounds of formula [MII(tppz)(NCS)(μ-1,3-NCS)]n [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and M = Co(1) and Ni (2)] are reported. 1 and 2 are isomorphous compounds and they crystallize in the P21/n space group. Their structures are made up of zig-zag chains of cobalt(II) (1) and nickel(II) ions (2) bridged by single end-to-end thiocyanate groups with a tridentate tppz molecule and a terminally bound thiocyanate-N ligand achieving distorted MN5S octahedral surroundings around each metal center. The main source of the distortion of the ideal octahedron is due to the geometrical constraints issued from the occurrence of two fused five-member chelate rings of the tridentate tppz ligand, the values of the N-M-N bond angles covering the range 75.58(9)-78.66(9)º. The M-N bond lengths vary in the range 2.025(3)-2.116(29 (1) and 2.001(2)-2.079(2) Å (2) and they are shorter than the M-S bond distance [2.6395(10) (1) and 2.5225(9) Å (2)]. The values of the intrachain metal-metal separation are 6.4197(7) (1) and 6.3257(5) Å (2). The magnetic properties of 1 and 2 have been investigated in the temperature range 1.9-300 K. Both compounds exhibit intrachain ferromagnetic interactions with values of the magnetic coupling (J) of +4.60 (1) and +7.82 cm-1 (2) [the spin Hamiltonian being defined as H ̂=- J∑_(i=1)^(n-1)▒〖S ̂_i S ̂_(i+1) 〗].
    No preview · Article · May 2015 · Crystal Growth & Design

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Institutions

  • 1987-2016
    • University of Valencia
      • • Inorganic Chemistry
      • • Facultad de Química
      Valenza, Valencia, Spain
  • 1992-2013
    • Pierre and Marie Curie University - Paris 6
      • Institut Parisien de Chimie Moléculaire (IPCM)
      Lutetia Parisorum, Île-de-France, France
    • University of Barcelona
      Barcino, Catalonia, Spain
  • 1998-2012
    • Universidad de La Laguna
      • • Department of Basic Physics II
      • • Department of Basic Physics
      • • Department of Inorganic Chemistry
      • • Faculty of Physics
      San Cristóbal de La Laguna, Canary Islands, Spain
  • 2005-2010
    • Università della Calabria
      • Dipartimento di Chimica e Tecnologie Chimiche - CTC
      Rende, Calabria, Italy
  • 2006
    • Nottingham Trent University
      Nottigham, England, United Kingdom
  • 2001-2002
    • University of Bergen
      • Department of Chemistry
      Bergen, Hordaland, Norway
    • Università degli Studi della Basilicata
      Potenza, Basilicate, Italy
  • 1999
    • Philipps University of Marburg
      • Institut für Pharmazeutische Chemie
      Marburg, Hesse, Germany
  • 1988
    • Università degli Studi di Messina
      Messina, Sicily, Italy
  • 1983
    • Université Paris-Sud 11
      Orsay, Île-de-France, France