X-Ray Computed Tomography.

En esta ponencia se presenta una breve introducción a la técnica: Tomografía Computerizada de Rayos-X. Además, se presenta el tomógrafo ubicado en la Unidad de Difracción de Rayos-X y Tomografía Computerizada de los Servicios Centrales de Apoyo a la Investigación, SkyScan 2214 (Bruker S.L.), así como los experimentos que se están llevando a cabo (incluyendo estudios donde se combina tanto la difracción de rayos-X como la tomografía).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Synthesis and characterization of M(II) phosphonates (M = Fe, Co, Zn, Mn) as precursors for PEMFCs electrocatalysts

Metal phosphonates are promising precursors for applications such as proton conductivity [1] and catalysis [2]. Specifically, upon calcination metal polyphosphates are generated that can be used as non-noble metal alternatives [3] to the highly expensive commercial catalysts (Pt) for proton exchange membrane fuel cells (PEMFCs). In this work, we present the synthesis and characterization of metal polyphosphates obtained from transition divalent metal phosphonates (M= Fe, Mn, Co and Zn) both as monometallic and bimetallic systems (solid solutions). For the preparation of the metal phosphonate precursors, two types of organic linkers were selected, i.e. 2-R,S-hydroxiphosphonoacetic acid [HO3PCH(OH)COOH, HPAA] and nitrilotrismethylenephosphonic acid [N(CH2PO3H2)3, ATMP]. The as synthesized compounds were calcined between 700 and 1000 ºC under N2. Depending on the metal/phosphorous molar ratio in the precursor phases, different compositions were found, the corresponding metal pyrophosphate being the major component according to the crystallographic data. Interestingly, in most of cases the solid solutions were preserved in the final product, for instance Fe-Mn, Fe-Co and Fe-Zn. All calcined materials have been also characterized by XPS, SEM/EDS, FTIR-Raman.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Tunable crystal structure and proton conductivity of lanthanide nitrilotrismethylphosphonates

Metal phosphonates are multifunctional solids with remarkable stability and proton conducting properties owing to their structure is usually composed of extended hydrogen-bond networks that favor proton transfer pathways [1]. Moreover, these properties can be enhanced by appropriate modification of the synthesis conditions [2, 3]. In this communication, a new family of isostructural 2D layered compounds based on lanthanide nitrilotris-methylphosphonates is reported. These compounds have been isolated at room temperature and have the general formula Ln[N(CH2)3(PO3H2)2(PO3H)(H2O)]SO4·2H2O (Ln= Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb). The coordination environment of Ln3+ is composed by eight oxygen atoms from three different ligands and two oxygens from bound waters. This connectivity creates positive charged layers connected to sulfate ions through hydrogen-bonds. These compounds show promising proton conductivity with values ranging between 7.6·10-2 and 3.8·10-2 S·cm-1 at 80 °C and 95% RH and low activation energy corresponding to Grotthuss-type proton transfer mechanism. In addition, a structural transformation occurs at T > 70 °C accompanied by a remarkable enhanced conductivity. Studies on the structure-properties relationships will be discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO: MAT2016-77648-R Junta Andalucía: P12-FQM-1656 y FQM-11

New multifunctional sulfonato-containing metal phosphonates proton conductors

Anchoring of acidic functional groups to organic linkers acting as ligands in metal phosphonates has been demonstrate to be a valid strategy to develop new proton conductor materials, which exhibit tunable properties and are potentially applicable to proton exchange membranes, such as those used in PEMFCs [1,2]. In this work, the structural and proton conductivity properties of several families of divalent and trivalent metal amino-sulfophosphonates are presented. The chosen ligand, (H2O3PCH2)2-N-(CH2)2-SO3H, was reacted with the appropriate metal salt using highthrough-put screening and/or microwave-assisted synthesis. Different crystal structures haven been solved displaying a variety of metal ligand coordination modes, in whose frameworks acidic groups contribute to create strong H-bond networks; together with lattice and bound water molecules. Proton conductivity values oscillate between 10-4 and 10-2 S.cm-1, at 80 ºC and 95 % relative humidity, most of them showing activation energies characteristic of a Grotthuss-type proton transport mechanism.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO: MAT2016-77648-R Junta de Andalucía: P-12-FQM-1656 y FQM-11

La odisea de medir PDF con un difractómetro “convencional”

En esta ponencia se presenta la puesta a punto del difractómetro D8 Advance (Bruker S.L.) para la adquisición de datos de laboratorio de PDF (Pair Distribution Function) junto con los resultados obtenidos.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Zinc(II), cobalt(II) and manganese(II) networks with phosphoserine ligand: Synthesis, crystal structures magnetic and conduction properties

A series of zinc(II), cobalt(II) and manganese(II) coordination networks with the phosphoserine ligand (Pser) is synthesized and characterized. Whereas in compounds 1 and 2 with the general formula [M(Pser)]n [M = Zn (1) and Co(2)], the metal(II) ion presents a tetrahedral geometry, in [Co(Pser)(H2O)2]n (3) and [Mn(Pser)(H2O)]n (4)], the metal(II) ions are in a distorted octahedral geometry. The 3D frameworks are formed by inorganic layers built up from MO4 or MO6 polyhedra and phosphate groups. These layers are linked by the carboxylate groups of the phosphoserine ligand. The presence of extended hydrogen bonding stabilizes the 3D network and favors the proton transfer leading to moderate proton conductors. The highest proton conductivity, 2.70·10−5 S cm−1 (at 80 ºC and 95% RH), is obtained for compound 3. Temperature dependent magnetic susceptibility measurements for 2−4 reveal predominant antiferromagnetic interactions between the paramagnetic metal(II) ions.Proyectos MAT2013-41836-R y MAT2016-77648-R del MINECO, y proyecto (P12-FQM-1656) de la Junta de Andalucía

Synthesis and properties of novel lanthanide carboxyphosphonates

Metal phosphonates are essentially acidic solids featured by groups such as P-OH, -COOH, etc. The presence of bound and lattice water favors the formation of H-bond networks, which make these compounds appropriate as proton conductors, attractive for proton exchange membranes (PEMs) of Fuel Cells. Moreover, these properties can be enhanced by appropriate modification of the synthesis conditions. We report here, general characteristics of three new series of isostructural compounds resulting from the combination of the polyfunctional 5-(dihydroxyphosphoryl) isophthalate acid with lanthanide ions. All compounds were synthesized under hydrothermal conditions and their crystal structures were solved from powder X-ray diffraction data using synchrotron radiation. In contrast with Series III compounds, which exhibit a layered structure, Series I and II present pillared frameworks. All these compounds contain water molecules that contribute to the formation of H-bond networks. Upon exposure to ammonia vapour, from an aqueous solution, solid state transformations are observed which are accompanied of an enhancement of their proton conductivity properties.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Phosphonate Decomposition-Induced Polyoxomolybdate Dumbbell-Type Cluster Formation: Structural Analysis, Proton Conduction, and Catalytic Sulfoxide Reduction

The reaction of MoO4^2− with a number of phosphonic acids [bis-(phosphonomethyl)glycine, R,S-hydroxyphosphonoacetic acid, 1-hydroxyethane-1,1-diphosphonic acid, phenylphosphonic acid, aminotris(methylene phosphonic acid), and 1,2- ethylenediphosphonic acid] under oxidizing (H2O2) hydrothermal conditions at low pH leads to rupture of the P−C bond, release of orthophosphate ions, and generation of the octanuclear, phosphate-bridged, polyoxometalate molybdenum cluster (NH4)5[Mo8(OH)2O24(μ8-PO4)](H2O)2 (POMPhos). This cluster has been fully characterized and its structure determined. It was studied as a proton conductor, giving moderate values of σ = 2.13 × 10−5 S·cm−1 (25 °C) and 1.17 × 10−4 S·cm−1 (80 °C) at 95% relative humidity, with Ea = 0.27 eV. The POMPhos cluster was then thermally treated at 310 °C, yielding (NH4)2.6(H3O)0.4(PO4Mo12O36) together with an amorphous impurity containing phosphate and molybdenum oxide. This product was also studied for its proton conductivity properties, giving rise to an impressively high value of σ = 2.43 × 10−3 S· cm−1 (25 °C) and 6.67 × 10−3 S·cm−1 (80 °C) at 95% relative humidity, 2 orders of magnitude higher than those corresponding to the “as-synthesized” solid. The utilization of POMPhos in catalytic reduction of different sulfoxides was also evaluated. POMPhos acts as an efficient homogeneous catalyst for the reduction of diphenyl sulfoxide to diphenyl sulfide, as a model reaction. Pinacol was used as a low-cost, environmentally friendly, and highly efficient reducing agent. The effects of different reaction parameters were investigated, namely the type of solvent and reducing agent, presence of acid promoter, reaction time and temperature, loading of catalyst and pinacol, allowing to achieve up to 84−99% yields of sulfide products under optimized conditions. Substrate scope was tested on the examples of diaryl, alkylaryl, dibenzyl, and dialkyl sulfoxides and excellent product yields were obtained.Proyecto MAT2016-77648-R del MINECO y proyectos P12-FQM-1656 y FQM-113 de la Junta de Andalucí

Proton Conductivity in Sulfate-Containing Lanthanide Nitrilotris-methylphosphonates

Multifunctional metal phosphonates are coordination polymers (CPs) whose structures are usually composed of extended hydrogen-bond networks and thus making them potential candidates as proton conductors [1]. Moreover, these properties can be enhanced by appropriate modification of the synthesis conditions [2, 3]. In this communication, isostructural 2D layered compounds based on lanthanide nitrilotrismethylphosphonates are studied. In series 1 compounds, Ln[(ATMP)(H2O)2]HSO4·2H2O (Ln= Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Yb3+), uncoordinated HSO4- acts as the counterion of positively charged layers creating an extended hydrogen-bond networks together with the lattice water molecules, while the lanthanide ions are octacoordinated by two water molecules and six oxygen from four different ligands. This phase transforms to other structures by dehydration or by exposing the samples at 80 ºC and 95% relative humidity. Under wet conditions, the solids experience partial (Ln= Pr3+, Eu3+, Tb3+) or full loss (Ln= Yb3+) of HSO4-, accompanied by a structural reorganization that influence the proton conductivity properties. In series 2, Ln[(ATMP)(H2O)](SO4)·H2O (Ln= Pr3+, Eu3+, Gd3+ and Tb3+), the octacoordinated environment of lanthanide ions in the layer structure is composed of six phosphonate oxygen atoms and two oxygen from two sulfate ions which acts as a bridge ligands. This structural variability allows obtaining solids with conductivities ranging between 3.5·10-2 and 1.0·10-3 S·cm-1 (80 ºC and 95% RH) and activation energies corresponding to a Grotthuss-type proton transfer mechanism.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MAT2016-77648-R, Junta de Andalucía-FQM-11

Three-Component Copper-Phosphonate-Auxiliary Ligand Systems: Proton Conductors and Efficient Catalysts in Mild Oxidative Functionalization of Cycloalkanes

The synthesis, structural characterization, topological analysis, proton conductivity, and catalytic properties are reported of two Cu(II)-based compounds, namely a dinuclear Cu(II) complex [Cu2(μ-VPA)2(phen)2(H2O)2]· 8H2O (1) (H2VPA = vinylphosphonic acid, phen = 1,10- phenanthroline) and a 1D coordination polymer [Cu(μ- SO4)(phen)(H2O)2]∞ (2). Their structural features and Hbonding interactions were investigated in detail, showing that the metal−organic structures of 1 and 2 are extended by multiple hydrogen bonds to more complex 2D or 1D Hbonded architectures with the kgd [Shubnikov plane net (3.6.3.6)/dual] and SP 1-periodic net (4,4)(0,2) topology, respectively. These nets are primarily driven by the H-bonding interactions involving water ligands and H2O molecules of crystallization; besides, the (H2O)4/(H2O)5 clusters were identified in 1. Both 1 and 2 are moderate proton conductors, with proton conductivity values, σ = 3.65 × 10−6 and 3.94 × 10−6 S·cm−1, respectively (measured at 80 °C and 95% relative humidity). Compounds 1 and 2 are also efficient homogeneous catalysts for the mild oxidative functionalization of C5−C8 cycloalkanes (cyclopentane, cyclohexane, cycloheptane, and cyclooctane), namely for the oxidation by H2O2 to give cyclic alcohols and ketones and the hydrocarboxylation by CO/H2O and S2O82− to the corresponding cycloalkanecarboxylic acids as major products. The catalytic reactions proceed under mild conditions (50−60 °C) in aqueous acetonitrile medium, resulting in up to 34% product yields based on cycloalkane substrate.Proyecto MAT2016-77648-R del MINECO y proyecto FQM-1656 de la Junta de Andalucí