Synthesis and crystal structure of tetramethylammonium fluoride octadecasil

摘要: Abstract Octadecasil, a clathrate-type inclusion compound, has been synthesized hydrothermally at 453 K with gel having the composition 1.0SiO2:0.53tetramethylammonium (TMA+):0.54fluoride:86H2O. The crystal structure determined based on powder X-ray diffraction data taken 298 K, and refined using Rietveld method. result confirms AST-type, all-silica framework model developed by Caullet et al. [P. Caullet, J.L. Guth, J. Hazm, J.M. Lamblin, H. Gies, Eur. Solid State Inorg. Chem. 28 (1991) 345]. Furthermore, rigid body position orientation of occluded TMA+ cation in rhombododecahedral [46612] cage can be determined; F− anion located hexahedral [46] cage. unit cell parameters, tetragonal space group I4/m, have as: a = b = 9.07 A, c = 13.44 A, volume = 1104.97 A3. is |[N(CH3)4+]2.0F−1.9|[Si20O40], i.e., both ions possess near full occupancies, compensate each other's electronic charges. crystallization AST cooperative structure-directing effect ions.