El cambio climático y las condiciones ambientales en los partidos de La Plata, Berisso y Ensenada, provincia de Buenos Aires: aspectos preliminares

Se presentan las tareas iniciales realizadas en relación al proyecto Efectos del cambio climático en las condiciones ambientales de los Partidos de Berisso, Ensenada y La Plata, que es financiado por la Universidad Nacional de La Plata en el marco del programa de “Proyectos de innovación y transferencia en áreas prioritarias (PIT-AP). Con este proyecto, iniciado en 2011, se propone avanzar en el conocimiento y evaluación de la influencia que generan los cambios climáticos en las condiciones ambientales del borde sur del Río de La Plata. Estos cambios pueden producir importantes efectos en el desarrollo socioeconómico y en los riesgos a que se encuentra sometida esta región. Debido a la escasez de datos básicos y la falta de un conocimiento adecuado de las condiciones ambientales de la región, se están realizando los estudios geológicos, geomorfológicos, hidrológicos, ecológicos y topográficos necesarios para el modelado de posibles escenarios de los cambios climáticos.Facultad de Ciencias Naturales y Muse

El cambio climático y las condiciones ambientales en los partidos de La Plata, Berisso y Ensenada, provincia de Buenos Aires: aspectos preliminares

Se presentan las tareas iniciales realizadas en relación al proyecto Efectos del cambio climático en las condiciones ambientales de los Partidos de Berisso, Ensenada y La Plata, que es financiado por la Universidad Nacional de La Plata en el marco del programa de “Proyectos de innovación y transferencia en áreas prioritarias (PIT-AP). Con este proyecto, iniciado en 2011, se propone avanzar en el conocimiento y evaluación de la influencia que generan los cambios climáticos en las condiciones ambientales del borde sur del Río de La Plata. Estos cambios pueden producir importantes efectos en el desarrollo socioeconómico y en los riesgos a que se encuentra sometida esta región. Debido a la escasez de datos básicos y la falta de un conocimiento adecuado de las condiciones ambientales de la región, se están realizando los estudios geológicos, geomorfológicos, hidrológicos, ecológicos y topográficos necesarios para el modelado de posibles escenarios de los cambios climáticos.Facultad de Ciencias Naturales y Muse

The supramolecular behavior of the polycatenated double-layer coordination polymer [Cd2(isonicotinate)4(pab)(H2O)] n (pab = 1,4-di-4-pyridyl-2,3-diaza-1,3-butadiene)

The reaction mixture of pab and isonicotinate ligands with cadmium(II) nitrate under hydrothermal conditions generates a novel three-dimensional catenate framework, namely [Cd2(isonicotinate)4(pab) (H2O)]n (1) (pab = 1,4-di-4-pyridyl-2,3-diaza-1,3- butadiene). Single crystal X-ray diffraction shows that 1 possesses 2D bi-layer grids which are linked by pab pillars to give cuboidal subunits. The 2D bilayers are stacked and then concatenated to each other to form the 3D supramolecular framework. The most important interactions between the stacked layers involve the pivotal action of the water molecules through the formation of OH(water)/O(isonicotinate) H-bonds. Likewise, the concatenation produces strong H-bonding interactions that connect the entangled bilayers by using the non-aromatic CH groups of the pab pillar to give the CH(pab)/O(isonicotinate, water) arrangement. This supramolecular behavior of 1 is different from those observed in already known related cadmium complexes havin

Structural and theoretical characterization of a new twisted 4′-substituted terpyridine compound: 4′-(isoquinolin-4-yl)-2,2′:6′,2′′-terpyridine

4′-Substituted derivatives of 2,2′:6′,2′′-terpyridine with N-containing heteroaromatic substituents, such as pyridyl groups, might be able to coordinate metal centres through the extra N-donor atom, in addition to the chelating terpyridine N atoms. The incorporation of these peripheral N-donor sites would also allow for the diversification of the types of noncovalent interactions present, such as hydrogen bonding and π-π stacking. The title compound, C24H16N4, consists of a 2,2′:6′,2′′-terpyridine nucleus (tpy), with a pendant isoquinoline group (isq) bound at the central pyridine (py) ring. The tpy nucleus deviates slightly from planarity, with interplanar angles between the lateral and central py rings in the range 2.24(7)-7.90(7)°, while the isq group is rotated significantly [by 46.57(6)°] out of this planar scheme, associated with a short Htpy⋯Hisq contact of 2.32Å. There are no strong noncovalent interactions in the structure, the main ones being of the π-π and C - H⋯π types, giving rise to columnar arrays along [001], further linked by C - H⋯N hydrogen bonds into a three-dimensional supramolecular structure. An Atoms In Molecules (AIM) analysis of the noncovalent interactions provided illuminating results, and while confirming the bonding character for all those interactions unquestionable from a geometrical point of view, it also provided answers for some cases where geometric parameters are not informative, in particular, the short Htpy⋯Hisq contact of 2.32Å to which AIM ascribed an attractive character.Fil: Granifo, Juan. Universidad de La Frontera; ChileFil: Arévalo, Beatriz. Universidad de La Frontera; ChileFil: Gaviño, Rubén. Universidad Nacional Autónoma de México; MéxicoFil: Suarez, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; ArgentinaFil: Baggio, Ricardo Fortunato. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentin

A temperature-induced order-disorder phase transition in a 4-substituted 4,2′:6′,4′′-terpyridine

Crystals of 4′-(isoquinolin-4-yl)-4,2′:6′,4′′-terpyridine (iqtp), C24H16N4, grown from an ethanol solution, undergo a reversible first-order single-crystal to single-crystal phase transition at T c in the range 273-275K, from a disordered higher-temperature phase [form (I)] in the space group P21/c, with one single molecule in the asymmetric unit, to an ordered lower-temperature one [form (II)] in the space group P21/n, with two independent molecules in the asymmetric unit. There is a group-subgroup relationship linking (I)-(II), due to cell doubling and the disappearance of a number of symmetry operations. In addition to X-ray diffraction, the transition has been monitored by Raman spectroscopy and differential scanning calorimetry, the latter disclosing an enthalpy change of 0.72(6)kJmol-1. Variations of the unit-cell parameters with temperature between 170 and 293K are presented. The evolution of diffraction spots in the vicinity of the transition temperature shows the coexistence of both phases, confirming the first-order character of the transition. Structural details of both phases are analyzed and intermolecular interactions compared in order to investigate the mechanism of the phase transition. A three-dimensional Hirshfeld surface analysis was performed to corroborate the significant changes in the intermolecular features.Fil: Granifo, Juan. Universidad de La Frontera; ChileFil: Westermeyer, Marleen. Universidad de La Frontera; ChileFil: Riquelme, Maricel. Universidad de La Frontera; ChileFil: Gaviño, Rubén. Universidad Nacional Autónoma de México; MéxicoFil: Suarez, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; ArgentinaFil: Halac, Emilia Beatriz. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Universidad Nacional de San Martín; ArgentinaFil: Baggio, Ricardo Fortunato. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentin

Synthesis and ionic transport of sulfonated ring-opened polynorbornene based copolymers

The N-pentafluorophenyl-exo-endo-norbornene-5,6-dicarboximide (1a) and N-phenyl-exo-endo-norbornene- 5,6-dicarboximide (1b)monomers were synthesized and copolymerized via ring opening metathesis polymerization (ROMP) using bis(tricyclohexylphosphine)benzylidene ruthenium(IV) dichloride (I) and tricyclohexylphosphine[1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidene] rutheniumdichloride (II). Experiments, at distinct monomer molar ratios, were carried out using catalyst I in order to determine the copolymerization reactivity constants by applying theMayo-Lewis and Fineman- Ross methods. Moreover, both catalysts were used to produce random and block high molecular weight copolymers of 1a with 1b and 1a with norbornene (NB) which were further hydrogenated using a Wilkinson’s catalyst. Then, the saturated copolymers underwent a nucleophilic aromatic substitution by reacting with sodium 4-hydroxybenzenesulfonate dihydrate to generate new polynorbornene ionomers bearing fluorinated pendant benzenesulfonate groups. A thorough study on the electrochemical characteristics involving electromotive forces of concentration cells and proton conductivity of cation-exchange membranes based on a block copolymer of norbornene dicarboximides containing structural units with phenyl and fluorinated pendant benzenesulfonate moieties is reported. The study of electromotive forces (emf) of concentration cells with the sulfonated membrane of copolymer 8 separating electrolyte solutions of different concentration indicate that the membranes exhibit high permselectivity to protons and sodium ions at moderately low concentrations. In principle, these results suggest that the membranes can be considered candidates for ionic separation applicationsFinancial support from National Council for Science and Technology of Mexico (CONACYT) (PhD Scholarship to A.A.S.) is gratefully acknowledged. J. Vargas acknowledges CONACYT for a Posdoctoral Fellowship. We thank CONACYT-SEMARNAT and ICyTDF for generous support with contracts 23432 and 4312. We are grateful to Alejandrina Acosta, Salvador López Morales, Miguel Ángel Canseco and Carlos Flores Morales for their assistance in NMR, GPC, thermal properties and AFM, respectively. This work was also supported by the CICYT through the project MAT2008- 06725-C03-01.Peer reviewe

Sulfonated polynorbornene dicarboximide:candidate for proton exchange membrane fuel cells

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Gas transport and ionic transport in membranes based on polynorbornenes with functionalized imide side groups

This work reports the synthesis and hydrogenation of polynorbornenes with functionalized imide side groups, specifically, poly(N-phenyl-exo,endo-norbornene-5,6-dicarboximide), as well as the sulfonation of the hydrogenated polymer. The gas transport characteristics and permselectivity of membranes prepared from the three separated polymers were thoroughly investigated. The results show that hydrogenation of the starting polymer promotes packaging efficiency, which is even enhanced by further sulfonation of the hydrogenated chains. The economy of free volume is reflected in the permeation and permselectivity coefficients of membranes prepared from the polymers. The study of electromotive forces of concentration cells with the sulfonated membrane separating hydrochloric solutions of different concentration suggests that the membranes exhibit high permselectivity to protons that decreases as concentration increases. However, a sharp increase in the electromotive force occurs at high concentrations. The fact that this increase is not observed in the electromotive forces of concentration cells with sodium chloride in the compartment cells suggests the formation of pair ions between protonated imide groups and chloride ions at high concentration that restrains co-ions mobility in the membrane. The membranes exhibit pretty good permselectivity to protons and sodium ions which makes them useful for ionic separation applications, such as electrodialysis. However, owing to the low water uptake, the protonic conductivity of the membranes equilibrated with water is nearly 2 orders of magnitude below that reported for Nafion membranesWe thank Dr. T. Ezquerra (Instituto de Estructura de la Materia, CSIC) for the membranes conductivitymeasurements. This work was supported by the Comunidad de Madrid (CAM) through the Program Interfases (S-0505/ MAT-0227), Fondo Europeo de Desarrollo Regional (F.E.D- .E.R.), and Fondo Social Europeo (F.S.E.). Support by the Dirección General de Investigación Científica y Técnica (DGICYT), Grant MAT-2005-05648-C02-01, is gratefully acknowledgedPeer reviewe