Mesostructured metal germanium sulfide and selenide materials based on thetetrahedral [Ge4S10](4-) and [Ge4Se10](4-) units: Surfactant templated three-dimensional disordered frameworks perforated with worm holes

The polymerization of [Ge4S10](4-) and [Ge4Se10](4-) unit clusters with the divalent metal ions Zn2+, Cd2+, Hg2+, Ni2+, and Co2+ in the presence of va rious surfactant cations leads to novel mesostructured phases. The surfacta nts are the quaternary ammonium salts C12H25NMe3Br, C14H29NMe3Br, C16H33NMe 3Br, and C18H37NMe3Br, which play the role of templates, helping to assembl e a three-dimensional mesostructured metal-germanium chalcogenide framework , These materials are stoichiometric in nature and have the formula of (R-N Me3)(2)[MGe(4)Q(10)] (Q = S, Se). The local atomic structure was probed by X-ray diffuse scattering and pair distribution function analysis methods an d indicates that the adamantane clusters stay intact while the linking meta l atoms possess a tetrahedral coordination environment. A model can be deri ved, from the comparison of measured and simulated X-ray powder diffraction patterns, describing the structure as an amorphous three-dimensional frame work consisting of adamantane [Ge(4)Q(10)](4-) units that are bridged by te trahedral coordinated M2+ cations, The network structures used in the simul ations were derived from corresponding disordered structures developed for amorphous silicon. The frameworks in (R-NMe3)(2)[MGe(4)Q(10)] are perforate d with worm hole-like tunnels, occupied by the surfactant cations, which sh ow no long-range order. This motif is supported by transmission electron mi croscopy images of these materials. The pore sizes of these channels mere e stimated to lie in the range of 20-30 Angstrom, depending on the appointed surfactant cation length. The framework wall thickness of ca, 10 Angstrom i s thereby independent from the surfactant molecules used. Up to 80% of the surfactant molecules can be removed by thermal degradation under vacuum wit hout loss of mesostructural integrity. Physical, chemical, and spectroscopi c properties of these materials are discussed. (C) 2000 Academic Press.