Mn(HPO3): A new manganese (II) phosphite with a condensed structure

A new manganese (II) phosphite with the formula Mn(HPO₃) has been synthesised under mild hydrothermal conditions and autogenous pressure. Large pink coloured single crystals were obtained, allowing the resolution of the structure by x-ray diffraction. Mn(HPO₃) crystallises in the P2₁/c monoclinic space group with a=8.036(3) Å, b=8.240(3) Å, c=10.410(3) Å, β=124.73(3)° and Z=8. The structure consists of a three-dimensional, compact framework of edge sharing MnO₆ octahedra linked to phosphite groups via oxygens. The presence of the phosphite anion has been confirmed by IR spectroscopy. Mn(HPO₃) presents a high thermal stability limit of 580 °C, before rapid transformation to Mn₂P₂O₇ occurs. Photoluminescence and diffuse reflectance spectroscopy studies show the presence of high spin Mn(II) in significantly distorted octahedral coordination with Dq and Racah parameters of Dq=820, B=910 and C=3135 cm⁻¹. The ESR spectra, performed at different temperatures, are isotropic with a g-value of 2.00(1). Magnetic measurements indicate global antiferromagnetic interactions with a ferromagnetic transition at 15 K, attributed to a canting of the antiferromagneticaly aligned spins.