New layered hydrogenophosphate, protonic conductor: Mn(H<inf>2</inf>PO <inf>4</inf>)<inf>2</inf>

A new hydrogenophosphate Mn(H2PO4)2 has been synthesized from an aqueous solution. Its ab initio structure resolution shows that the original layered structure of this phase consists of PO 2(OH)2 tetrahedra and MnO5OH octahedra, sharing corners to form [MnP2O8H4]∞ layers, whose cohesion is ensured through hydrogen bonds. The excitation and emission spectra of this phase are characteristic of Mn2+ species. This phosphate is shown to be a good protonic conductor with a conductivity of 10-4.4 S/cm at 90°C (363 K). © 2008 American Chemical Society.