Two new members of the mero-plesiotype rhodesite series (Sr2Na2[Si8O19]4H2O, abbreviated as TR09, a 22.7681, b 6.9352, c 13.5789 Å, β 92.58, space group C2/c; SrNa4[Si8O19]4H2O, TR10, a 22.4102, b 7.0292, c 13.3140 Å, β 92.54°, space group Pc) have been hydrothermally synthesized in Teflon-lined autoclaves at 230°C and structurally characterized using X-ray diffraction single-crystal data. The crystal structures were solved by direct methods and refined to R 0.021 [TR09; 3317 reflections with Io > 2σ(Io)] and R 0.033 [TR10; 7247 reflections with Io > 2σ(Io)]. Both structures are based on a rhodesite-type microporous heteropolyhedral framework, where two types of channels are within the double silicate layer. The large Sr2+ cation constrains to a roughly ellipsoidal shape the cross section of the channels and in TR09 leads to a new type of the "octahedral" (O) sheet that in all members of the series alternates with the silicate layer. The H2O molecules are hosted both in the O sheet and in the channels, where they are loosely hydrogen bonded. The crystal-chemical features that allow flexibility to the rhodesite-type microporous heteropolyhedral framework and make it interesting for possible technological applications are discussed.
Two new silicate structures based on a rhodesite-type heteropolyhedral microporous framework.
CADONI, MARCELLA;FERRARIS, Giovanni
2010-01-01
Abstract
Two new members of the mero-plesiotype rhodesite series (Sr2Na2[Si8O19]4H2O, abbreviated as TR09, a 22.7681, b 6.9352, c 13.5789 Å, β 92.58, space group C2/c; SrNa4[Si8O19]4H2O, TR10, a 22.4102, b 7.0292, c 13.3140 Å, β 92.54°, space group Pc) have been hydrothermally synthesized in Teflon-lined autoclaves at 230°C and structurally characterized using X-ray diffraction single-crystal data. The crystal structures were solved by direct methods and refined to R 0.021 [TR09; 3317 reflections with Io > 2σ(Io)] and R 0.033 [TR10; 7247 reflections with Io > 2σ(Io)]. Both structures are based on a rhodesite-type microporous heteropolyhedral framework, where two types of channels are within the double silicate layer. The large Sr2+ cation constrains to a roughly ellipsoidal shape the cross section of the channels and in TR09 leads to a new type of the "octahedral" (O) sheet that in all members of the series alternates with the silicate layer. The H2O molecules are hosted both in the O sheet and in the channels, where they are loosely hydrogen bonded. The crystal-chemical features that allow flexibility to the rhodesite-type microporous heteropolyhedral framework and make it interesting for possible technological applications are discussed.
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