Abstract
The novel borophosphate Rb2.3(H2O)0.8Mn3[B4P6O24(O,OH)2] was prepared under hydrothermal conditions at 553 K. Its crystal structure was determined using single-crystal X-ray diffraction data obtained from a non-merohedral twin and refined against F2 to R = 0.057. The compound crystallizes in the orthorhombic space group Pbcn, with unit-cell parameters a = 20.076(2) Å, b = 9.151(1) Å, c = 12.257(1) Å, V = 2251.8(2) Å3, and Z = 4. The title compound is the first example of a borophosphate with manganese ions adopting both octahedral and tetrahedral coordinations. Its unique crystal structure is formed by borophosphate slabs and chains of Mn2+-centered polyhedra sharing edges and vertices. These 2D and 1D fragments interconnect into a framework with open channels that accommodate Rb+ cations and water molecules. Topological relationships between borophosphates built from three-membered rings of two borate and one phosphate tetrahedra sharing oxygen vertices, amended by additional PO4 and HPO4 tetrahedra, are discussed. The temperature dependence of the magnetic susceptibility of Rb2.3(H2O)0.8Mn3[B4P6O24(O,OH)2] reveals predominant antiferromagnetic exchange interactions and the high-temperature effective magnetic moment corresponding to the high-spin S = 5/2 state of Mn2+ ions. At 12.5 K, a magnetic transition is evidenced by ac-susceptibility and specific heat measurements. A spin-trimer model with the leading exchange interaction J ∼ 3.2 K is derived from density-functional band-structure calculations and accounts for all experimental observations.
Highlights
The chemical class of borophosphates comprises compounds with crystal structures built by PO4 and BO4/BO3 oxocomplexes sharing oxygen vertices
We present here its crystal structure and magnetic properties in comparison with related compounds featuring borophosphate slabs of similar topology
The Mn–O distances are in the range of 2.117(4)–2.260(6) Å for Mn1; the Mn2 atoms are on the twofold axis and surrounded by four O atoms forming tetrahedra with the Mn2–O bond lengths of 2.079(6) and 2.107(5) Å
Summary
The chemical class of borophosphates comprises compounds with crystal structures built by PO4 and BO4/BO3 oxocomplexes sharing oxygen vertices. The first such cobalt borophosphate with organic molecules filling structural channels was reported by Sevov.[20] In the (C2H10N2)Co [B2P3O12(OH)] crystal structure, the borophosphate slabs with three- and nine-membered rings share oxygen vertices with 2960 | Dalton Trans., 2017, 46, 2957–2965 K2(H2O)Co[B2P3O12(OH)] Borophosphate slabs and CoO6 octahedra form a 3D mixed anionic framework with K atoms and water molecules in channels
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have