Synthesis and structural characterisation of transition metal fluoride sulfates

Eleven first row transition metal fluoride sulfates synthesised in hydrofluorothermal conditions have been structurally characterised by single crystal X-ray diffraction and exhibit a wide variety of structural motifs. The polyionic structures containing Ti, V, Mn and Fe vary from discrete polyhedral units in Na4TiF4(SO4)2 and [N2C10H12] TiF4SO4, through one dimensional chains in (K2FeF3SO4, Li3FeF2(SO4)2·H2O, Li1.87Ti1.13O0.39F1.61(SO4)2, [N2C10H12]TiF2(SO4)2, [N2C6H16]Fe(SO4)2F and [N2C6H16]V(SO4)2F), and to two dimensional layers in ([N2C6H16](2+)Mn2F2(SO4)2, Na2VF3SO4 and Na3CrF2(SO4)2).

Manganese(III) fluorophosphate frameworks

Nine new manganese(III) fluorophosphates have been synthesised hydrothermally in a fluoride-rich medium, through the use of MnF(3), HPF(6) and monovalent metal fluorides as reactants. Products have been structurally characterised using single crystal X-ray diffraction. Reaction in fluoride-rich conditions produces chain, layer and three dimensional framework structures containing new and unusual structural features based on the linking of PO(3)F, PO(2)(OH,F)(2) and Mn(O(6-n),F(n)) octahedra, with n averaging 2.8 over the family of compounds. The Mn(III), d(4), oxidation state is stabilised under these reaction conditions and products frequently show Jahn-Teller distorted Mn(O,F)(6) units with axially elongated Mn-O or, less commonly, Mn-F distances. Structures exhibiting inter-layer spaces and channels frequently have these lined by terminal fluoride anions of the PO(3)F, PO(2)(OH,F)(2) and Mn(O,F)(6) octahedra.

The role of polar, lamdba (Λ)-shaped building units in noncentrosymmetric inorganic structures

A methodology for the design of polar, inorganic structures is demonstrated here with the packing of lambda (Λ)-shaped basic building units (BBUs). Noncentrosymmetric (NCS) solids with interesting physical properties can be created with BBUs that lack an inversion center and are likely to pack into a polar configuration; previous methods to construct these solids have used NCS octahedra as BBUs. Using this methodology to synthesize NCS solids, one must increase the coordination of the NCS octahedra with maintenance of the noncentrosymmetry of the bulk. The first step in this progression from an NCS octahedron to an inorganic NCS solid is the formation of a bimetallic BBU. This step is exemplified with the compound CuVOF(4)(H(2)O)(7): this compound, presented here, crystallizes in an NCS structure with ordered, isolated [Cu(H(2)O)(5)](2+) cations and [VOF(4)(H(2)O)](2-) anions into Λ-shaped, bimetallic BBUs to form CuVOF(4)(H(2)O)(6)·H(2)O, owing to the Jahn-Teller distortion of Cu(2+). Conversely, the centrosymmetric heterotypes with the same formula MVOF(4)(H(2)O)(7) (M(II) = Co, Ni, and Zn) exhibit ordered, isolated [VOF(4)(H(2)O)](2-) and [M(H(2)O)(6)](2+) ionic species in a hydrogen bond network. CuVOF(4)(H(2)O)(7) exhibits a net polar moment while the heterotypes do not; this demonstrates that Λ-shaped BBUs give a greater probability for and, in this case, lead to NCS structures.