Synthesis and characterization of new fluoride-containing manganese vanadates A2Mn2V2O7F2 (A=Rb, Cs) and Mn2VO4F

Abstract

Large single crystals of A 2 Mn 2 V 2 O 7 F 2 (A = Rb, Cs) and Mn 2 VO 4 F were grown using a hightemperature (~600˚C) hydrothermal technique. Single crystal X-ray diffraction and powder Xray diffraction were utilized to characterize the structures, which both possess MnO 4 F 2 building blocks. The A 2 Mn 2 V 2 O 7 F 2 series crystallizes as a new structure type in space group Pbcn (no. 60), Z = 4 (Rb 2 Mn 2 V 2 O 7 F 2 : a = 7.4389(17) Å, b = 11.574(3) Å, c = 10.914(2) Å; Cs 2 Mn 2 V 2 O 7 F 2 : a = 7.5615(15) Å, b = 11.745(2) Å, c = 11.127(2) Å). The structure is composed of zigzag chains of edge-sharing MnO 4 F 2 units running along the a-axis, and interconnected through V 2 O 7 pyrovanadate groups. Temperature dependent magnetic susceptibility measurements on this interesting one-dimensional structural feature based on Mn 2+ indicated that Cs 2 Mn 2 V 2 O 7 F 2 is antiferromagnetic with a Neél temperature, T N = ~ 3 K a Weiss constant, θ, of-11.7(1) K. Raman and infrared spectra were also analyzed to identify the fundamental V-O vibrational modes in Cs 2 Mn 2 V 2 O 7 F 2. Mn 2 (VO 4)F crystalizes in the monoclinic space group of C2/c (no. 15), Z = 8 with unit cell parameters of a = 13.559(2) Å, b = 6.8036(7) Å, c = 10.1408(13) Å and β = 116.16(3)°. The structure is associated with those of triplite and wagnerite. Dynamic fluorine disorder gives rise to complex alternating chains of five-and sixcoordinate Mn 2+. These interpenetrating chains are additionally connected through isolated VO 4 tetrahedra to form the condensed structure.

Low temperature synthesis, structure and magnetic properties of Mn2[VO4]F

“…The structure consists of a 3D-framework built up of VO 4 tetrahedra, and manganese (II) polyhedra which form chains running along the [101] and [010] directions. Although the crystal structure is very similar to that of earlier report [12], fluoride atomic positions are slightly different (Fig. S3).…”

Sodium Transition Metal Vanadates from Hydrothermal Brines: Synthesis and Characterization of NaMn4(VO4)3, Na2Mn3(VO4)3, and Na2Co3(VO4)2(OH)2

“…This rich chemistry makes the vanadates an almost ideal testbed for the study of brine fluids on new material formation. Thus far we have investigated rubidium‐, cesium‐, strontium‐, and barium‐based halide brines with transition metal vanadates under hydrothermal conditions , , . In some cases we have observed halide incorporation into the lattice, such as in Ba 5 Mn 3 (V 2 O 7 ) 3 (OH,Cl)Cl 3 , Ba 2 Mn(V 2 O 7 )(OH)Cl, and Cs 3 Mn(VO 3 ) 4 Cl .…”

“…Finally, it is obvious that the chemistry of these fluids and the ultimate final products are highly sensitive to the composition of the brines and these formulations provide yet another chemical knob to adjust, leading to an almost infinite array of new solids. Thus far, we investigated vanadate synthesis from hydrothermal brines based on the hydroxides, carbonates, fluorides, and chlorides of cesium, barium, and strontium , , . We now extend our study to the use of mixed sodium chloride/sodium hydroxide brines as the mineralizer in reactions with transition metals and vanadate building blocks.…”

“…These materials are generally synthesized at relatively high temperatures using traditional solid‐state techniques, such as melts or fluxes , . Alternatively, our group found that high temperature (500–700 °C) hydrothermal synthesis leads to a wide range of unusual new transition metal vanadates, often in the form of large, high‐quality single crystals , . In addition to their new structure types, many of these materials have interesting magnetic properties.…”

Alkali Transition‐Metal Molybdates: A Stepwise Approach to Geometrically Frustrated Systems

“…Vanadate oxyanions, (VO 4 ) 3À ,a re particularly versatile buildingb locks for complex magnetic structures containing divalent andt rivalent transition metals. [14][15][16][17][18] The presence of empty d-orbitals in the oxyanion bridging units can also have as ignificant effect on the value and sign of the coupling constant. With its similar size, tetrahedral structure, and empty dorbitals, the molybdate oxyanion, (MoO 4 ) 2À ,c an be expected to adopt many of the same structural roles as (VO 4 ) 3À .The crystal chemical substitutions of additional constituent elements (e.g.…”