Chiral open-framework uranyl molybdates. 1. Topological diversity: synthesis and crystal structure of [(C2H5)2NH2]2[(UO2)4(MoO4)5(H2O)](H2O)

Krivovichev, Sergey V., Cahill, Christopher L., Nazarchuk, Evgeniy V., Burns, Peter C., Armbruster, Th and Depmeier, Wulf (2005) Chiral open-framework uranyl molybdates. 1. Topological diversity: synthesis and crystal structure of [(C2H5)2NH2]2[(UO2)4(MoO4)5(H2O)](H2O) Microporous and Mesoporous Materials, 78 (2-3). pp. 209-215. DOI 10.1016/j.micromeso.2004.10.018.

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Abstract

Crystals of a new framework uranyl molybdate, [(C2H5)2NH2]2[(UO2)4(MoO4)5(H2O)](H2O), were synthesized from a solution of UO2(CH3COO)2 · 2H2O, MoO3, diethylamine and HCl in H2O at 220 °C. The structure was studied at -127 °C. The compound is hexagonal, space group P6522, a = 11.3612(13), c = 52.698(8) A, V = 5890.7(13) A3, Z = 3. The structure has been refined to R1 = 0.050 (wR2 = 0.100; S = 0.985) on the basis of 3103 unique observed reflections. The structure consists of a three-dimensional framework of composition [(UO2)4(MoO4)5(H2O)]2- that consists of UO7 pentagonal bipyramids that share equatorial corners with MoO4 tetrahedra. The framework contains a three-dimensional system of channels. The first system of channels is parallel to [0 0 1] and has the dimensions 7.0 × 7.0 A, which result in a crystallographic free diameter (effective pore width) of 4.3 × 4.3 A (based on an oxygen radius of 1.35 A). Other channels run parallel to [1 0 0], [1 1 0] and [0 1 0] and have dimensions 5.2 × 7.1 A (giving an effective pore width of 2.5 × 4.4 A). One symmetrically unique [(C2H5)2NH2]+ cation and H2O molecule reside in the framework cavities. The channels parallel to [0 0 1] are chiral and are centered about a 65 screw axis. The uranyl framework with U:Mo = 4:5 in the structure of [(C2H5)2NH2]2[(UO2)4(MoO4)5(H2O)](H2O) represents the third known type of chiral uranyl molybdate framework. Its relationships to the frameworks with U:Mo = 5:7 and 6:7 can be understood in terms of fundamental chains that have related but yet different topological structure.

Document Type: Article
Keywords: Uranyl molybdates Open framework Crystal structure Chiral Nodal representation
Research affiliation: Kiel University
DOI etc.: 10.1016/j.micromeso.2004.10.018
ISSN: 1387-1811
Date Deposited: 02 Feb 2012 08:59
Last Modified: 08 Oct 2012 10:26
URI: http://eprints.uni-kiel.de/id/eprint/16071

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