Synthesis and ab initio structural determination of a new pillared nickel diphosphonate: VSB-6 or Ni_(5.4)(OH,F)_4[O_3P-(CH_2)_3-PO_3]_2(H_2O)_(1.4)·1.2H_3O

摘要

Ni_(5.4)(OH,F)_4[O_3P-(CH_2)_3-PO_3]_2(H_2O)_(1.4)·1.2H_3O or VSB-6 was prepared under hydrothermal conditions (4-6 days, 180 ℃, autogenous pressure). It was structurally characterized, ab initio, from laboratory X-ray powder diffraction data: orthorhombic, space group Pmmn (n°59), a = 17.937(1), b = 6.4299(4), c = 4.4936(3) A, V = 518.27(4) A~3, D_c = 2.694 g·cm~(-3). The structure is built up from inorganic layers, Ni_(5.4)(OH,F)_4O_(12)P_4(H_2O)_(1.4),constructed from chains of edge-sharing octahedra onto which are grafted phosphonate groups and statistically occupied nickel octahedra. The alkyl chain of the organic moiety connects the inorganic layers to form a pillared solid. VSB-6 is stable under air up to 400 ℃. On cooling to 6 K, VSB-6 orders magnetically with a canted antiferromagnetic structure.