Biomedical subjects

Lionel Beitone

Publications and source records attributed to Lionel Beitone.

5 recordsLinked to original sources

PubMed2004

Is water templating nanoporous materials?

(H(2)O)(17), a cluster with pentagonal water arrangements, squeezed in the sodalite cage of the crystal structure MIL-74 (Zn(6)Al(12)P(24)O(96).[N(CH(2)CH(2)NH(3))(3)](8).(H(2)O)(34)), has its oxygen atoms well located by X-ray powder diffraction. Positioning of hydrogen atoms has been performed by a dynamic partial atomic charges and hardnesses analysis calculation, in which partial charges are recalculated for each hydrogen sub-network modification. Hydrogen atoms are therefore positioned by energy minimization. A quantitative estimation of the hydrogen bonds energy for each H-bond and for the network in the MIL-74 nanoporous compound has been obtained. This result allows a discussion of the effect of imprinting the nanoporous structure onto water or alternatively the templating effect of the cluster onto the inorganic framework.

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PubMed2003

Order-disorder in the super-sodalite Zn3Al6(PO4)12, 4tren, 17H2O (MIL-74): a combined XRD-NMR assessment.

A new mixed zinc-aluminum phosphate Zn(3)Al(6)(PO(4))(12), 4tren, 17H(2)O (MIL-74) has been hydrothermally synthesized with the tris(2-aminoethyl)amine (tren) as a structure-directing agent (453 K, 36 h, autogenous pressure). The solid was characterized by a nonclassical method combining single-crystal X-ray diffraction and several solid-state NMR experiments, RFDR, C7 double quantum ((31)P), and 3QMAS ((27)Al). Its crystal structure is cubic, a = 16.7942(1) A, but the choice of the space group does not follow usual routes of structure determination, due to some "disorder" between Zn and Al. It can be assigned as well to I-43m or to P-43n. The open-framework is built up from an enneameric unit (T = Zn, Al) containing five TO(4) and four PO(4) tetrahedra (one of the P-O bonds is terminal). A central TO(4) tetrahedral unit shares all of the corners with four phosphates groups. Two phosphate groups are connected to two other peripheral TO(4) units. It results in the formation of a "pseudo" planar building block T(5)P(4) consisting of four square 4-rings. The connection of the T(5)P(4) units generates a three-dimensional framework, which defines a super-sodalite topology. The resulting cavities (diameter of 10 A) are bound by 12-ring windows in which are located the tren species in interaction with the phosphate groups (mainly terminal P-O bonds) through hydrogen bonds. A cluster of 17 water molecules occupies the center of the super-sodalite cage. The cationic (Zn, Al) occupancy is discussed for this specific topology.

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PubMed2003

MIL-50, an open-framework GaPO with a periodic pattern of small water ponds and dry rubidium atoms: a combined XRD, NMR, and computational study.

A new fluorinated gallium phosphate, MIL-50, has been synthesized under mild hydrothermal conditions using 1,6-diaminohexane. The chemical formula of MIL-50 is Rb(2)Ga(9)(PO(4))(8)(HPO(4))(OH)F(6).2N(2)C(6)H(18).7H(2)O. The structure is a network of hexameric units of Ga(3)(PO(4))(3)F(2) and Ga(3)(PO(4))(2)(HPO(4))F(3) via corner sharing. It creates a three-dimensional open-framework delimiting 6- and 18-ring channels running along the c axis. The diprotonated 1,6-diaminohexane and water molecules are trapped within the 18-ring pores, whereas the rubidium cations reside in the 6-ring ones. A double quantum (31)P NMR experiment and partial charge calculations indicate that water molecules are present under the form of periodic small clusters, lowering the multiplicity of one phosphorus site, P3. Though water hops within the clusters, the motion leaves the water pattern periodic. Rubidium is so tightly embedded into the framework that water moving in the large 18-ring channels does not reach it, leaving it therefore dry. The crystal framework may be ascribed to the orthorhombic space group Cmc2(1) (n degrees 36), a = 32.1510(2), b = 17.2290(3), c = 10.2120(1) A. The periodic water pattern has a different symmetry than that of the framework. A method has been devised to superpose the two sublattices that coexist in the same unit cell in order to have full occupancy of each site and to perform Madelung summations. This original method is of general interest for most zeolitic materials exhibiting a different symmetry for the framework and the template sublattices.

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PubMed2002

Hydrothermal synthesis and structural characterization of a new organically templated germanate, Ge(10)O(21)(OH).N(4)C(6)H(21).

A new open-framework germanium oxide Ge(10)O(21)(OH).N(4)C(6)H(21) has been hydrothermally synthesized at 180 degrees C for 6 days by using the tris(2-aminoethyl)amine (tren) molecule as a structure-directing agent. This compound was characterized by means of single-crystal X-ray diffraction and FTIR. It crystallizes in the noncentric monoclinic system Cm (a = 14.0495(2) A, b = 12.8058(3) A, c = 9.2637(2) A, beta = 128.406(1) degrees, Z = 4). Its three-dimensional framework is built up from GeO(4) and GeO(3)(OH) tetrahedra connected by vertexes to GeO(5) trigonal bipyramids and GeO(6) octahedra. A pseudo-cubic building unit ("4-3" subunit) consists of four GeO(4) tetrahedra, two GeO(5) trigonal bipyramids, and one GeO(6) octahedron (Ge(7)). In the "4-3" block, the GeO(5) trigonal bipyramids share a common edge. This Ge(7) entity is linked to three tetrahedral units GeO(3)X (X = O, OH), and this forms an original decameric building unit Ge(10)O(21)(OH) which is new in the germanates crystal chemistry. It results in a relatively dense open framework composed of pear-shape cavities (7(8)6(2)5(2)4(4)3(2)) encapsulating the triprotonated tren molecule. The inorganic network contains small pores delimited by 7-ring channels running along [001].

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PubMed2002

Rb(GaPO4)2(OH)(H2O).H2O: a hydrated rubidium gallium phosphate analogue of GaPO4.2H2O and leucophosphite.

Crystals of the title hydrated rubidium gallium phosphate, rubidium aqua-mu(3)-hydroxo-di-mu-phosphato-digallium hydrate, were synthesized hydrothermally at 453 K under autogenous pressure. The solid crystallizes in the monoclinic system and its structure was determined from single-crystal X-ray diffraction analysis. It is similar to dihydrated gallium phosphate, GaPO(4).2H(2)O, which is isostructural with the mineral leucophosphite. The structure is built up from a three-dimensional anionic framework composed of corner-linked octameric Ga(4)(PO(4))(4)(OH)(2)(H(2)O)(2) units. The Ga atom is in an octahedral coordination. Connection of the Ga(4)P(4) species generates eight-ring channels, in which are encapsulated the Rb(+) cations and water molecules.

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