Synthesis, crystal structure and characterization of AP2DAO, a new layeredaluminophosphate templated by 1,8-diaminooctane molecules

The first example of a 2D-layered aluminophosphate with P:Al = 18:13 has be en synthesized hydrothermally in the presence of 1,8-diaminooctane (DAO) as templating molecule, and its structure has been solved using single crysta l X-ray diffraction data. It has the composition (C8N2H22)(8)[Al13P18O72]. 6H(2)O and crystallizes in space group R (no. 148) with a = 16.508(10) Angs trom and c = 48.715(75) Angstrom. The structure consists of layers built up mainly from tetrahedrally coordinated Al and P atoms. separated by and hyd rogen bonded to doubly protonated DAO molecules. One of the 13 aluminum ato ms is octahedrally coordinated and connected to six P tetrahedra, thus form ing Al(OP)(6) units. These units are responsible for the unusual layer stoi chiometry. never observed previously in 2D-layered aluminophosphates, Two c rystallographically different DAO molecules were located, one in a general position and one in a special position on the 3-fold axis. For the latter, only the head of the molecule (NH3-CH2-group) was located. The other atoms are off the 3-fold axis, and the chain appears to be disordered. The compou nd was characterized by multi-dimensional solid state NMR. All Al-27 and P- 31 NMR signals have been assigned to the crystallographically non-equivalen t Al and P atoms of the structure. (C) 2001 Elsevier Science B.V. All right s reserved.