Open Access
Immobilization of polyoxometalates on tailored polymeric surfaces
(MDPI, 2018) Aguado-Ureta, Saioa; Rodríguez-Hernández, Juan; Campo, Adolfo del; Pérez-Álvarez, Leyre; Ruiz-Rubio, Leire; Vilas, José Luis; Artetxe, Beñat; Reinoso, Santiago; Gutiérrez Zorrilla, Juan M.; Ciencias; Zientziak
Herein we describe the preparation of hybrid polymer–inorganic interfaces by the immobilization of polyoxometalate nanoclusters on functionalized polymer surfaces. The polymeric surfaces were made of polystyrene-b-poly(acrylic acid)/polystyrene (PS-b-PAA/PS) blends by spin coating on a silicon wafer. The functionalization of the polymer film was obtained by interfacial migration of the amphiphilic block copolymer toward the interface upon water vapor annealing. The carboxylic acid functional groups contained in the PAA block were then employed to anchor the [LnIII(α-SiW11O39)]5− polyoxometalates (Ln: Ce, Er). This purpose was achieved by immersing the films in aqueous solutions of the in situ-formed inorganic nanoclusters. X-ray photoelectron and confocal Raman spectroscopies, together with atomic force microscopy, confirmed the immobilization of the inorganic species at the interface.
Open Access
Thermostructural behavior in a series of lanthanide-containing polyoxotungstate hybrids with copper(II) complexes of the tetraazamacrocycle cyclam: a single-crystal-to-single-crystal transformation study
(American Chemical Society, 2019) Martín Caballero, Jagoba; Artetxe, Beñat; Reinoso, Santiago; San Felices, Leire; Vitoria, Pablo; Larrañaga, Aitor; Vilas, José Luis; Gutiérrez Zorrilla, Juan M.; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
A series of 14 isostructural [Cu(cyclam)](2)[{Cu(cyclam)}4{(a-GeW11O39)Ln(H2O)-(OAc)(12)].18H(2)O (1-Ln, where Ln = La Lu; cyclam = 1,4,8,11-tetraazacyclotetradecane) polyoxometalate-based hybrids reported herein represent (i) the first example of a twodimensional covalent hybrid lattice involving the [{(aXWI 1039)Ln(H2O)(OAc)}2in- archetype and (ii) the first structural characterization of such a dimeric polyoxotungste for Ln = La and Pr as well as for the combination of X = Ge and Ln = Ce, Nd, Sm, or Lu. Compounds 1-Ln have been characterized by elemental analyses, infrared spectroscopy, and thermogravimetric analysis, and their thermostructural behavior has been monitored by powder and single-crystal Xray diffraction. The title compounds undergo two single-crystal-to-single-crystal transformations triggered dehydration leading to the [{Cu(cydam)}6{(alpha-GeW11O39)Ln(H2O)(OAc)}2]-4H(2)O intermediate (2-Ln, where Ln = Eu or Er) and [Cu(cyclam)]0.5[{Cu(cyclam)}55{(alpha-GeW11O39)Ln(0Ac)}2] (3-Ln, where Ln = Ce or Eu) final anhydrous phases, the latter evidencing a coordinatively unsaturated derivative of the dimeric archetype for the first time. These transitions involve formation and disruption of Cu Opom bonds that result in different {Cu(cydam)}(2+) moieties grafting onto and being released from Keggin surfaces, which reduces the dimensionality of 1-Ln to one-dimensional covalent assemblies for 2-Ln and 3-Ln. While all 3-Ln phases rehydrate fully upon exposure to air for 24 h, the kinetics governing the crystal transitions back toward 1Ln through 2-Ln depend on the nature of Ln. Under ambient moisture, the anhydrous structures fully revert back to the parent framework for Ln = La Sm, while the samples containing Eu to Lu afford mixtures of 1-Ln and 2-Ln and require immersion in water for the structural reversion to reach completion. Single-crystal X-ray diffraction analyses of the rehydrated 1R-Ln samples (Ln = Ce, Eu, and Er) support these observations.
Open Access
Thermally-triggered crystal dynamics and permanent porosity in the first heptatungstate-metalorganic three-dimensional hybrid framework
(Wiley, 2017) Martín Caballero, Jagoba; Artetxe, Beñat; Reinoso, Santiago; San Felices, Leire; Castillo, Óscar; Beobide, Garikoitz; Vilas, José Luis; Gutiérrez Zorrilla, Juan M.; Institute for Advanced Materials and Mathematics - INAMAT2
The hybrid compound [{Cu(cyclam)}3(W7O24)]⋅15.5 H2O (1) (cyclam=1,4,8,11-tetraaza-cyclotetradecane) was synthesized by reacting the {Cu(cyclam)}2+ complex with a tungstate source in water at pH 8. Compound 1 exhibits an unprecedented three-dimensional covalent structure built of heptatungstate clusters linked through metalorganic complexes in a POMOF-like framework that displays water-filled channels. This dynamic architecture undergoes two sequential single-crystal-to-single-crystal transformations upon thermal evacuation of water molecules to result in the partially dehydrated [{Cu(cyclam)}3(W7O24)]⋅12 H2O (2) and anhydrous [Cu(cyclam)]0.5[{Cu(cyclam)}2.5(W7O24)] (3) crystalline phases. These transitions are associated with cluster rotations and modifications in the CuII coordination geometries, which reduce the dimensionality of the original lattice to layered systems but preserving the porous nature. Phase 3 reverts to 2 upon exposure to ambient moisture, whereas the transition between 1 and 2 proved to be irreversible. The permanent microporosity of 3 was confirmed by gas sorption measurements (N2, CO2), which reveal a system of parallel channels made of wide cavities connected through narrow necks that limit the adsorption process. This observation is in good agreement with Grand Canonical Monte Carlo simulations.

Reinoso, Santiago

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