Emilio Escrivá

Synthesis, crystal structure, spectroscopic characterisation and magnetic properties of [Cu2(BIBM)2(C2O4)2]·4H2O (BIBM=bis(2-imidazolyl)bis(methoxycarbonyl)methylmethane)

Abstract The structure and spectroscopic and magnetic properties of bis(μ-1,2,3-oxalato)bis[bis(2-imidazolyl)bis(methoxycarbonyl)methylmethane]dicopper(II) tetrahydrate are described. The compound is built of centrosymmetric neutral dimeric [Cu2(BIBM)2(C2O4)2] entities linked through hydrogen bonds involving water molecules and oxalate groups. In the dimeric unit the two centrosymmetrically related copper — which are involved in CuN2O2O2′ chromophores lying in an elongated octahedral environment — are bridged through the oxalate group which acts in a bidentate–monodentate (μ-1,2,3) fashion. Both electronic and EPR spectra are indicative of an essentially dx2−y2 ground state for the copper(II) ions. Magnetic susceptibility measurements in the range 1.8–200 K show very weak antiferromagnetic exchange between the copper(II) ions (2J=−0.35 cm−1). This feature is discussed on the basis of the relative orientation of the coordination polyhedron around the metal atom and the bridging network.

Ferrimagnetic-like coupling in ordered one-dimensional systems. Homo- and hetero-metallic chains in EDTA complexes

We report on the magnetic behaviour of one-dimensional exchange-coupled systems MM′EDTA·6H2O, where M and M′ are two host sites for first-row transition metals (Co, Ni, Cu).The isolated complexes are either homometallic chains with one kind of magnetic cation or heterometallic chains with two distinct cations in the regular sequence ⋯A—B—A—B⋯.

Crystal and molecular structure and electronic properties of [Cu(bbimpy)(H2O)2(ONO2)](NO3)· H2O (bbimpy = 2,6-bis(2-benzimidazolyl)pyridine)

Abstract The crystal structure of the complex [Cu(bbimpy)(H2O)2(ONO2)](NO3)·H2O(bbimpy = 2,6-bis(2-benzimidazolyl)pyridine) has been determined by X-ray diffraction methods. It crystallises in the monoclinic space group P2 1 n , with Z = 4 in a cell of dimensions a = 13.350(1), b = 7.820(1), c = 21.484(1) A , β = 92.26(1)° . The structure is built up of [Cu(bbimpy)(H2O)2(ONO2)]+ cations, NO3− anions and crystal lattice water molecules, with a 4 + 1 + 1 pseudo-octahedral geometry for the CuN3OO′O″ chromophores. In the EPR spectrum exchange coupling between Cu(II) chromophores of different orientation is observed, and molecular g values, compatible with the crystallographic data, could be calculated.

Crystal structure, magnetic and spectroscopic properties of the bis(dimethyl sulfoxide) adduct of tetra-μ-formato-dicopper(II), a new tetracarboxylato-bridged copper(II) dimer

Abstract The crystal and molecular structure of a new tetracarboxylato-bridged copper(II) dimer, the bis(dimethyl sulfoxide)tetrakis(μ-formato)dicopper(II) has been determined by X-ray diffraction methods. It crystatlizes in the tetragonal space group I41/a, with Z=8 in a cell of dimensions a=17.688(2), c=10.408(1) A. The structure is built up of centrosymmetric neutral dimers [Cu2(HCOO)4(dmso)2], where four bidentate carboxylate anions form syn-syn bridges between the metal atoms which are in a 4 + 1 environment. Magnetic susceptibility data show that the copper atoms are strongly antiferromagnetically coupled with J=−434 cm−1. The obtained triplet-singlet energy gap is compared with those reported for a series of related dimers. Finally, the ESR spectrum shows characteristic features of a triplet state with a non-negligible zero field splitting, being typical of the copper(II) dimeric tetracarboxylates.

Crystal and molecular structure and properties of the first characterized copper(II) one-dimensional polymer containing mepirizole [4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6-methylpyrimidine]

The crystal and molecular structure of the complex [Cu(mpym)(H2O)(C4O4)]·2H2O [mpym = mepirizole = 4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6-methylpyrimidine] has been determined by X-ray methods. It crystallizes in the orthorhombic space group Pbcn, with Z= 8, a= 18.592(3), b= 14.723(2) and c= 13.755(3)A, R= 0.053 and R′= 0.070 for 2697 reflections. The structure comprises infinite chains parallel to [001] built up of 1-bis(monodentate) squarate-O1O3 C4O4 anions bridging [Cu(mpym)(H2O)]2+ units. The copper(II) ions display distorted trigonal-bipyramidal geometry. Both electronic and ESR spectra are indicative of an essentially dz2 ground state for the CuII. No exchange coupling has been detected down to 4.2 K by means of magnetic susceptibility measurements. This feature is discussed on the basis of the relative orientation of the co-ordination polyhedron around the metallic atom and the bridging ligand.

Procedures for synthesis of single-phase 2212 bismuth material☆

Abstract Benefiting from the features of the Bi2O3-CuO binary system, it is possible to isolate a single-phase Bi2Sr2CaCu2O8 high-Tc superconducting material starting from Bi2CuO4. The existence of (BiO2)n chains in the channel-containing open structure of this cuprate, which melts at relatively low temperature, makes it a suitable solid state precursor of the 2212 material.

Crystal structure, spectroscopic characterisation and magnetic properties of [Cu(BIP)(N3)]·H2O (BIP=3,3-bis(2-imidazolyl)propionate), a copper(II) polymeric compound with asymmetrical μ-1,3-azido bridges

Abstract The structure and the spectroscopic and magnetic properties of [3,3-bis(2-imidazolyl)propionato]azidocopper(II) monohydrate are described. The compound is built of [Cu(BIP)N3] entities which are connected through carboxylate groups from the BIP molecules —which act as a tridentate ligand—and asymmetrical μ-1,3-azido bridges, leading to a polymeric sheet-like structure. The copper atom is involved in a CuN3ON′ chromophore and lies in a distorted square-pyramidal environment. Both electronic and EPR spectra are indicative of an essentially dx2−y2 ground state for the copper(II) ions. Magnetic susceptibility measurements in the range 1.8–200 K show very weak antiferromagnetic exchange between the copper(II) ions (2J=−0.48 cm−1). This feature is discussed on the basis of the relative orientation of the coordination polyhedron around the metal atom and the bridging network.

X-ray crystal structure and electronic properties of chlorobis(mepirizole)copper(II) tetrafluoroborate (mepirizole = 4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6-methylpyrimidine)

Abstract The crystal structure of [Cu(mep)2Cl](BF4)[mep = 4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6-methylpyrimidine] has been determined by X-ray diffraction. The crystal structure is built up of [Cu(mep)2Cl]+ cations and BF4− anions. The structure of the cation involves a five-coordinated CuN4Cl chromophore, with a stereochemistry near to a compressed trigonal bypyramid (TBP) but with a significant degree of distortion towards the square pyramidal (SP) topology. The EPR spectrum is indicative of a mixed dz2/dx2 − y2 ground state for the copper(II) ions, in agreement with the structural data.

Thermal study of mepirizol complexes with Co(II), Ni(II), Cu(II) and Zn(II)

Abstract A study of the thermal behaviour of mepirizol complexes, M(mepirizol) n (ClO 4 ) 2 · x H 2 O and M(mepirizol)SO 4 · y H 2 O, is reported. All the compounds decompose in two general processes: dehydration and pyrolytic decomposition. A non-isothermal kinetic study of the dehydration process was carried out. Possible mechanisms of decomposition for the sulphate complexes are discussed.

Order and disorder in mixed metal linear chains: The homo and heterobimetallic EDTA (M(H2O)4OIOII)[M′(EDTA)] · 6H2O complexes (M = Mg, Mn, Co, Zn and Ni; M′ = Co, Ni, Cu and Zn)

SummaryPolymetallic solid solutions of the ethylenediaminetetracetic acid (EDTA) and six divalent metal ions exist in the range: MgαMnβCoγZnδNiεCuτ(EDTA) · 6H2O where α + β + γ + δ + ε + τ=2, 0⩽τ⩽1, 0⩽γ,ε,δ⩽2, 0⩽α, β⩽1.This type of structure is characterized by the presence of two different octahedral carboxylate-bridged coordination sites forming infinite zig-zag chains. Visible and i.r. spectra and t.g.a. analysis show that there is occupational preference for the two coordination sites in the crystalline structure.Due to this preference, and also to the structural features, the heterobimetallic MM′(EDTA) · 6H2O compounds constitute a structurally new class of materials which can be described as ordered alternating-heterobimetallic polymeric coordination complexes.