Studies on clathrasils VIII. Nonasils-[4158], 88SiO2 · 8M8 · 8M9 · 4M20: Synthesis,thermal properties,and crystal structure |
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Authors: | B Marler N Dehnbostel H -H Eulert H Gies F Liebau |
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Institution: | (1) Mineralogisches Institut, Universität Kiel, Kiel, F.R.G. |
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Abstract: | Nonasils-4158], 88SiO2·8M8·8M9·4M20, have been synthesized with 2-methylpyrrolidine, hexamethyleneimine, 2-(aminomethyl)-tetrahydrofuran, 1,2-diaminocyclohexane, 2-methylpiperidine, 2-methylpiperazine, 1-aminobutane, 2-aminobutane, and 2-aminopentane as guest molecules, M20. The samples have been prepared from aqueous silicate solutions which were sealed in silica tubes and heated at about 200°C for several weeks. These clathrasils crystallize in space groupFmmm. For the nonasil with 2-aminopentane as the guest molecule and the unit cell dimensionsa
o=22.232(6) Å,b
0=15.058(4) Å, andc
o=13.627(4) Å, the structure has been refined using 550 non-equivalent single crystal reflexions to a reliability factorR
w
=0.125. The 3-dimensional 4-connected silica host framework has three types of cage-like voids, 5464], 4158], and 58612], the latter housing the structure-controlling guest molecules, M20. The non-spherical shape of the guest molecules is the most important factor for the formation of nonasils-4158]. On heating nonasils-4158] up to 950°C the organic guest species are driven out and the pure silica form of nonasil is obtained.Part of this study was presented at the 24th Jahrestagung der AGKr, Cologne, 1985 1]. For part VII see 4]. |
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Keywords: | Clathrasil nonasil synthesis crystal structure porous silica |
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