Four new hydroxymonophosphates with closely related intersecting tunnels structures: The series AMIII(PO3(OH))2 with A=Rb, Cs; M=Fe, Al, Ga, In

The family of hydroxymonophosphates of generic formula AMIII(PO3(OH))2 has been revisited using hydrothermal techniques. Four new phases have been synthesized: CsIn(PO3(OH))2, RbFe(PO3(OH))2, RbGa(PO3(OH))2 and RbAl(PO3(OH))2. Single crystal diffraction studies show that they exhibit two different structural types from previously observed other phases with A=H3O, NH4, Rb and M  =Al, V, Fe. The “Cs–In” and “Rb–Fe” phosphates crystallize in the triclinic space group P1¯, with the cell parameters a=7.4146(3) Å, b=9.0915(3) Å, c=9.7849(3) Å, α=65.525(3)°, β=70.201(3)°, γ=69.556(3)° and V=547.77(4) Å3 (Z=3) for CsIn(PO3(OH))2 and a=7.2025(4) Å, b=8.8329(8) Å, c=9.4540(8) Å, α=65.149(8)°, β=70.045(6)°, γ=69.591(6)° and V=497.44(8) Å3 (Z=3) for α-RbFe(PO3(OH))2. The “Rb–Al” and “Rb–Ga” phosphates crystallize in the R3¯c space group, with a=8.0581(18) Å and c=51.081(12) Å (V=2872.5(11) Å3 and Z=18) for RbAl(PO3(OH))2 and a=8.1188(15) Å and c=51.943(4) Å (V=2965(8) Å and Z=18) for RbGa(PO3(OH))2. These two structural types are closely related. Both are built up from MIIIO6 octahedra sharing their apices with PO3(OH) tetrahedra to form [M3(PO3OH)6] units, but the latter exhibits a different configuration of their tetrahedra. The three-dimensional host-lattices result from the connection of the [M3(PO3OH)6] units and they present numerous intersecting tunnels containing the monovalent cations.

Four new phases in the AMIII(PO3(OH))2 series have been synthesized using hydrothermal techniques. Single crystals XRD studies show that they correspond to two different structural types presenting close relationships. Both three-dimensional host-lattices result indeed from the connection of similar [M3(PO3OH)6] structural units and they present numerous intersecting tunnels containing the monovalent cations. The influence of the size of the A and M cations on the resulting structure type adopted by the compounds of the AMIII(PO3(OH))2 series is examined.The M3O6[PO3(OH)]6 structural basic units encountered in the two studied structure types.Figure optionsDownload as PowerPoint slide