| Abstract |
A combination of advanced powder diffraction and NMR techniques have allowed the structure of the novel microporous aluminophosphate IST-1 (\(CH3NH2)(4)(CH3NH3+)(4)(OH-)(4)\[Al12P 12O48] to be elucidated. The framework structure was determined in the non-centrosymmetric space group Pca2(1) (a = 9.61523(1) Angstrom, b = 8.67024(1) Angstrom, c = 16.21957(2) Angstrom) from high-resolution synchrotron powder diffraction data using the program FOCUS. Extra framework species were then located on difference electron density maps. A hydroxyl group was found to bridge between two of the framework Al atoms, and one methylamine species, presumably protonated, could be located in the channels where it H-bonds to three framework oxygens. The most unusual feature of the structure is the second methylamine molecule, which bonds directly to a framework Al atom. The structure is entirely consistent with P-31 and Al-27 MAS NMR studies, which showed there to be three P (all 4-coordinate) and three At (one 4-, one 5- and one 6-coordinate) sites, and with C-13 MAS NMR, which showed there to be two different types of methylamine species in equal amounts. Assignment of the P-31, Al-27 and C-13 MAS NMR signals could be deduced from the crystallographic data, P-31-Al-27 HETCOR spectra and ab initio calculations. (C) 2003 Elsevier Inc. All rights reserved. |
