Abstract:

The replacement of phosphate with phosphite in the transition metal phosphates has attracted more and more research efforts. To date, only a few phosphite materials containing Fe cation have been reported. Our group has developed the hydrothermal synthesis of many novel metal phosphites. Here we reported another three-dimensional iron phosphites (H₃O)₂·[FeⅡ₅(HPO₃)₆]synthesized under mild hydrothermal conditions and characterized by single crystal X-ray diffraction. The title compound crystallized in the trigonal space group P3c1, with unit cell parameters, a=1.026 9(5) nm, b=1.026 9(5) nm, c=0.929 5(6) nm, and Z=2. The compound formed three-dimensional frameworks with six-membered channels along the c axis. The Fe centers in the frameworks adopt slightly distorted octahedral coordination geometry and were bridged by the pseudo-pyramidal phosphites. The temperature dependence of magnetic susceptibility measurements for the title compound indicates the occurrence of antimagnetic interaction between Fe ions. Neel′s temperature for Title compound is 6.43 K. Above Neel′s temperature materials have paramagnetic behavior which obeys to Curie-Weiss equation. The Curie constants is 23.4 emu\5K^-1\5mol^-1. The effective magnetic moment of the compound  at 300 K is 4.25μB per Fe ²⁺ .