| Abstract
| - Two different 3D [Li2Be2F7]- networks, based on linked BeF4 and LiF4 tetrahedra, have been templated by ammonium and methylammonium cations, respectively. The orientation of the amines and hydrogen bonding to fluoride control the framework geometry.
- Two three-dimensional lithiumberyllofluoride materials, of the same framework stoichiometry but different topologies, have been synthesized using hydrothermal pressureconditions and ammonium/methylammonium cations as structure-directing species. Compound I, [Li2Be2F7][NH4], and compound II, [Li2Be2F7][CH3NH3], both crystallize in orthorhombic space groups: Pca21 for I and Cmcm for II. Single crystal analysis reveals that thematerials have slightly different 3-D framework topologies for the [Li2Be2F7] frameworkcomposed of [LiF4] and [BeF4] tetrahedra connected through doubly and triply bridgingfluorides. Both networks can be viewed as sheets formed of 3- and 4-nets that linkperpendicular to the sheet, through a bridging fluoride, to form six-membered interlayerpores. The six-membered channels contain the amine species hydrogen-bonded to frameworkfluoride ions surrounding the interior of the pore. The thermal stability, spectroscopicproperties, and both powder X-ray and neutron data of these compounds are reported, alongwith the single-crystal analysis used to solve the structures.
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