Synthesis, crystal structure and properties of Na3Zn4O(AsO4)(3) center dot 6H(2)O, a new framework zincoarsenate

Synthetic Na3Zn4O(AsO4)(3).6H(2)O is built up from a three- dimensional network of vertex sharing ZnO4 and AsO4 tetrahedra with extra-framework sodium cations and water molecules completing the structure. Dehydration of Na3Zn4O(AsO4)(3).6H(2)O results in a facile, irreversible, framework transformation to hexagonal NaZnAsO4. The title compound is a new member of the M3Zn4O(XO4)(3).nH(2)O (M = univalent cation; X = P or As; n = 3.5-6) family of open-framework phases. It is isostructural with its phosphate congener but the sodium coordination is subtly different for the two phases. Crystal data: Na3Zn4O(AsO4)(3).6H(2)O, M-r = 871.31, trigonal, R3c (No. 161), a = 10.9493 (5), c = 26.7099 (13) Angstrom, V = 2773.2 (2) Angstrom(3), Z = 6, R(F) = 0.021, wR(F-2) = 0.042.