New layered hydrogenophosphate, protonic conductor: Mn(H2PO4)2.

A new hydrogenophosphate Mn(H 2PO 4) 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 MnO 5OH octahedra, sharing corners to form [MnP 2O 8H 4] infinity layers, whose cohesion is ensured through hydrogen bonds. The excitation and emission spectra of this phase are characteristic of Mn (2+) species. This phosphate is shown to be a good protonic conductor with a conductivity of 10 (-4.4) S/cm at 90 degrees C (363 K).