Pau Díaz-Gallifa

Dryness sensitive porous 3d–4f metal–organic framework with unusual dynamic behaviour

A new three-dimensional heteronuclear metal–organic framework has been synthesized using the 1,2,4,5-benzenetetracarboxylate ligand as a linker and Pr(III)–Cu(II) dinuclear units as nodes. The resulting structure shows an unexpected dynamic behaviour, where the volume of the crystal structure is shrunk by 11.5% in a dryness atmosphere.

Two-dimensional 3d-4f heterometallic coordination polymers: Syntheses, crystal structures, and magnetic properties of six new Co(II)-Ln(III) compounds

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.

Synthesis, crystal structure, and magnetic characterization of the three-dimensional compound [Co2(cbut)(H2O)3]n (H4cbut = 1,2,3,4-cyclobutanetetracarboxylic acid).

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 [011] 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).

Influence of the coligand in the magnetic properties of a series of copper(II)–phenylmalonate complexes

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.

Neutron Diffraction Studies of the Molecular Compound [Co2(bta)]n (H4bta =1,2,4,5-Benzenetetracarboxylic Acid): In the Quest of Canted Ferromagnetism

The exchange mechanism and magnetic structure of the organic-inorganic layered molecule-based magnet [Co2(bta)]n (1) (H4bta =1,2,4,5-benzenetetracarboxylic acid) have been investigated through variable-temperature magnetic susceptibility measurements and supported with a series of neutron diffraction experiments. Cryomagnetic studies have shown an antiferromagnetic ordering at a transition temperature of 16 K that is followed by the appearance of a weak ferromagnetism below 11 K. The weak antiferromagnetic interlayer interaction plays an important role in this system in spite of the long interlayer separation. A ferromagnetic ordering is induced by applied magnetic fields greater than 1800 G (metamagnetic behavior), and a slow magnetic relaxation from this ferromagnetic phase to the antiferromagnetic one is observed. The magnetic structure of 1 has been elucidated at low temperatures in zero field by neutron powder diffraction measurements and was found to be of antiferromagnetic nature with the local cobalt(II) spins (magnetic moments) being aligned ferromagnetically in the ac plane and antiferromagnetically coupled along the crystallographic b axis. No evidence for a long-range spontaneous ferromagnetic component below 11 K was observed in the neutron experiment.

Three new europium(III) methanetriacetate metal‐organic frameworks: the influence of synthesis on the product topology

Three new metal-organic framework structures containing Eu(III) and the little explored methanetriacetate (C7H7O6(3-), mta(3-)) ligand have been synthesized. Gel synthesis yields a two-dimensional framework with the formula [Eu(mta)(H2O)3]n·2nH2O, (I), while two polymorphs of the three-dimensional framework material [Eu(mta)(H2O)]n·nH2O, (II) and (III), are obtained through hydrothermal synthesis at either 423 or 443 K. Compounds (I) and (II) are isomorphous with previously reported Gd(III) compounds, but compound (III) constitutes a new phase. Compound (I) can be described in terms of dinuclear [Eu2(H2O)4](6+) units bonded through mta(3-) ligands to form a two-dimensional framework with topology corresponding to a (6,3)-connected binodal (4(3))(4(6)6(6)8(3))-kgd net, where the dinuclear [Eu2(H2O)4](6+) units are considered as a single node. Compounds (II) and (III) have distinct three-dimensional topologies, namely a (4(12)6(3))(4(9)6(6))-nia net for (II) and a (4(10)6(5))(4(11)6(4))-K2O2; 36641 net for (III). The crystal density of (III) is greater than that of (II), consistent with the increase of temperature, and thereby autogeneous pressure, in the hydrothermal synthesis.

Synthesis and structural characterization of six Cu(II)-based coordination polymers using the thermally tunable 1,2,3,4-cyclobutanetetracarboxylic acid

The synthesis and structural characterization of new six Cu(II) coordination polymers of formulae {[Cu2(ctc-cbut)(H2O)4]·2(H2O)}n (1), {[Cu5(ctc-cbut)2(OH)2(H2O)8]·7(H2O)}n (2), {[Cu2(ctc-Hcbut)(OH)(H2O)2]·4(H2O)}n (3), [Cu2(ttt-cbut)(H2O)4]n (4), {[Cu2(ttt-cbut)(H2O)4]·4(H2O)}n (5) and {[Cu4(ttt-cbut)2(H2O)2]·3(H2O)}n (6) (ctc-H4cbut = cis,trans,cis-1,2,3,4-cyclobutanetetracarboxylic acid and ttt-H4cbut = trans,trans,trans-1,2,3,4-cyclobutanetetracarboxylic acid), have been carried out, together with a computational study of the electronic and thermal free energies of the four isomers of the given ligand. The compounds 1–3 exhibit the ligand in its commercial cis,trans,cis conformation while 4–6 were synthesized with the trans,trans,trans isomer, after thermal treatment of the ctc-isomer. The topology of the six complexes synthesized have differences in dimensionality: compound 4 shows a one-dimensional topology, compound 3 presents a 2D-topology with a three nodal 4,4,4-c network, while 1, 2, 5 and 6 exhibit a 3D-topology with a binodal network 3,6-c for 1 and [412·612·84] [46]-flu for 2. Compound 5 presents a triply interpenetrated [66]-dia network while 6 exhibits a three-nodal network with [43][44·62][47·610·84] point symbol.

Synthesis, crystal structures and tautomerism in novel oximes based on hydroxyalkylpyrazolones

Two novel hydroxyethyl pyrazolones were obtained by condensation of 2-hydroxyethylhydrazine with ethyl acetoacetate or ethyl benzoylacetate, later nitrosation of the C4 carbon atom in the heterocyclic moiety, afforded two novel oxime-derivatives. The 1H and 13C NMR data show that 1-(2-hydroxyethyl)-3-methyl-5-pyrazolone (1) is largely present together with a very small amount of the 5-one tautomer in DMSO-d6; in contrast, 1-(2-hydroxyethyl)-3-phenyl-5-pyrazolone (2) is found as a single tautomer in CDCl3. Two diastereomers occur in DMSO-d6 in 1-(2-hydroxyethyl)-3-methyl-4-hydroxyimino-5-pyrazolone (3) while in 1-(2-hydroxyethyl)-3-phenyl-4-hydroxyimino-5-pyrazolone (4), a single species is present in CDCl3. Despite the polarity differences in the solvents used, remarkably the oxime tautomers proved to be more stable in both cases and DMSO-d6 only allows the equilibrium between E/Z diastereomers. Single crystal X-ray diffraction data of 1, 3 and 4 are presented, they show that 1 occurs as a keto-enamine tautomer, in clear contrast with the situation in solution; in the case of 3 and 4, the tautomeric equilibrium remains shifted to the oximes in the solid phase as the Z-diastereomer, exclusively. This finding is the opposite of what was described in a previous report for 1-alkyl-3-methyl-4-hydroximino-5-pyrazolone, where the E-diastereomer was present. Besides, the data show that the oxime motif is not affected by the substitution changes described in C3. IR data in the solid phase supports the crystal structures and suggest that 2 occurs as a similar tautomer as 1.

Dynamic behavior in a dryness sensitive 3d-4fmetal–organic framework

Dynamic behavior in a dryness sensitive 3d-4f metal–organic framework Oscar Fabelo,a,b,c Pau Díaz-Gallifa,c Laura Cañadillas-Delgado,a,b,c Jorge Pasán,c Carla Martinez-Benito,c Mariadel Déniz,c Diego Lozano,c Ana Labrador,d Catalina Ruiz-Pérez,c aInstituto de Ciencia de Materiales de Aragón. CSIC-Universidad de Zaragoza. (Spain). bInstitute Laue Langevin. Grenoble (France). cLaboratorio de Rayos X y Materiales Moleculares, Depto. Física Fundamental II, Universidad de La Laguna. Tenerife. (Spain). dBM16 – LLS. European Synchrotron Radiation Facility. Grenoble (France). E-mail: fabelo@ill.fr

Discrete and polymeric metal-organic systems based on the methanetriacetic acid

Discrete and Polymeric Metal-Organic Systems Based on the Methanetriacetic Acid Carla Martínez-Benitoa, Pau Diaz-Gallifa, Ana B. Lagob, Ander C. Arias, Irene Hernández-Rodríguez, Jorge Pasán, Catalina Ruiz-Pérez, aLaboratorio de Rayos X y Materiales Molecualres (MATMOL), Departamento de Física Fundamental II, Faultad de Física, Universidad de La Laguna, Tenerife, Spain. bDepartamento de Química Inorgánica, Universidad de Vigo, Spain. Email: cmarben@ ull.es