Metal diphosphonates with double-layer and pillared layered structures based on N-cyclohexylaminomethanediphosphonate

Abstract

Based on N-cyclohexylaminomethanediphosphonic acid (cmdpH 4), four new metal diphosphonate compounds with formula M 3(cmdpH) 2(H 2O) 2 [ M=Zn( 1), Co( 2)] and M 2(cmdpH 2) 2(4,4′-bipy) 0.5(H 2O) [ M=Co( 3), Mn( 4)] have been obtained and structurally determined. Compounds 1 and 2 are isostructural. Within the structure, the M(2)O 6 octahedra are each corner-shared with four PO 3C tetrahedra to form a single layer containing 3- and 7-member rings. Neighboring single layers are pillared by M(1)O 4 tetrahedra, resulting in a novel double-layer structure. The organic moieties of cmdpH 3− are grafted on the two sides of the double layer. Compounds 3 and 4 are also isostructural, displaying a pillared layered structure. Within the inorganic layer, the M(1)O 5 tetragonal pyramids and M(2)NO 5 octahedra are each linked by PO 3C tetrahedra through corner-sharing, forming a layer in the ab plane which contains 3- and 10-member rings. These layers are pillared by 4,4′-bipyridine via coordination with the M(2) atoms from the adjacent layers, leading to a three-dimensional open framework structure with channels generated along the a-axis. The organic groups of cmdpH 2 2− locate within the channels. Magnetic studies show that antiferromagnetic interactions are dominant in compounds 2–4. Field dependent magnetization reveals a spin flop behavior for 2.