Aluminiumphosphate mit nichtzentrosymmetrischen Schicht- und Raumnetzstrukturen aus topologisch verwandten Motiven: 2. KAl 2 (PO 4 ) 2 (OH)·2H 2 O/Aluminum Phosphates with Non-Centrosymmetric Layer- and Framework-Structures of Topologically Related Motifs: 2. KAl 2 (PO 4 ) 2 (OH)·2H 2 O

• Published in: Zeitschrift für Naturforschung. B, A journal of chemical sciences Vol. 52; no. 12; pp. 1447 - 1455
• Main Authors: Dick, Stefan, Großmann, Gisbert, Ohms, Gisela, Müller, Manfred
• Format: Journal Article
• Language: English
• Published: 01.12.1997
• ISSN: 0932-0776; 1865-7117
• DOI: 10.1515/znb-1997-1202

Abstract KAl 2 (PO 4 ) 2 (OH)·2H 2 O was obtained by the reaction of gibbsite with a potassium-phosphate solution of pH = 5.5 at 373 K. A single crystal X-ray structure analysis showed that it is an ordered, F-free K-analog of the microporous compound AIPO 4 -CI 2 . Crystal data: orthorhombic space group P2 1 2 1 2 1 , a = 920.5(1), b = 970.7(2), c = 982.8(2) pm, Z = 4. The structure consists of dimeric units of AIO 6 octahedra and AIO 5 trigonal bipyramids, bridged by an OH and two bidentate phosphate groups. The dimers are linked by phosphate to form corrugated layers which are topologically related to the layers in KAl 2 (PO 4 ) 2 (OH)·4H 2 O and minyulite. The layers are connected by Al-O-P and hydrogen bonds to a three dimensional framework structure with K ions in channel-like cavities. A neutron powder scattering experiment with KAl 2 (PO 4 ) 2 (OD)·2D 2 O showed that the bridging OD group and only one D of each water molecule are involved in hydrogen bonding. 31 P MAS NMR spectra show two isotropic lines at δ iso = -6.9 and -18,7 ppm of the intensity ratio 1:1 and confirm the presence of two crystallographically independent P atoms in the unit cell. In the 1 H MAS NMR spectra the water molecules and the bridging OH group show signals at 5.9 and 1.1 ppm, respectively.