Syntheses, structures, ionic conductivities, and magnetic properties of three new transition-metal borophosphates Na5(H3O){MII3[B3O3(OH)]3(PO4)6}•2H2O (MII = Mn, Co, NI)

Three new open-framework transition-metal borophosphates Na-5(H3O){M(II)3[B3O3(OH)](3)(PO4)(6)}(.)2H(2)O (M-II = Mn, Co, Ni) (denoted as MBPO-CJ25) have been synthesized under mild hydrothermal conditions. Single-crystal X-ray diffraction analyses reveal that the three compounds possess isostructural three-dimensional (3D) open frameworks with one-dimensional 12-ring channels along the [001] direction. Notably, the structure can also be viewed as composed of metal phosphate layers [M-II(PO4)(2)](4-) with Kagome topology, which are further connected by [13307(OH)l triborates, giving rise to a 3D open framework. The guest water molecules locate in the 12-ring channels. Partial Na+ ions reside in the 10-ring side pockets within the wall of the 12-ring channels, and the other Na+ ions and protonated water molecules locate in the 6-ring windows delimited by MO6 and PO4 polyhedra to compensate for the negative charges of the anionic framework. These compounds show a high thermal stability and are stable upon calcinations at ca. 500 degrees C. Ionic conductivities, due to the motion of Na+ ions, are measured for these three compounds. They have similar activation energies of 1.13-1.25 eV and conductivities of 2.7 x 10(-7)-9.9 x 10(-7) S cm(-1) at 300 degrees C. Magnetic measurements reveal that there are very weak antiferromagnetic interactions among the metal centers of the three compounds. Crystal data: MnBPO-CJ25, hexagonal, P6(3)/m (No. 176), a 11.9683(5) angstrom, c = 12.1303(6) angstrom, and Z = 2; CoBPO-CJ25, hexagonal, P6(3)/m (No. 176), a 11.7691(15) angstrom, c 12.112(2) angstrom, and Z = 2; NiBPO-CJ25, hexagonal, F6(3)/m (No. 176), a = 11.7171(5) angstrom, c 12.0759(7) angstrom, and Z = 2.