Crystal structure, vibrational spectra and thermal analysis of a new centrosymmetric transition metal phosphate compound, Mn(H2PO4)2⋅4H2O

The crystal of Manganese(II) bis(aqua) bis(dihydrogen phosphate) dihydrate, Mn(H2O)2(H2PO4)2⋅2H2O (Mn(H2PO4)2⋅4H2O), was obtained for the first time. Its structure was solved by the X-ray method at room temperature. The crystal belong to the P 1 ¯ space group of the triclinic system (a = 7.788(3) Å, b = 7.881(3) Å, c = 9.322(4) Å, α = 66.90(4)°, β = 84.75(2)°, γ = 72.71(3)°, V = 502.3(3) Å3 and Z = 2). The structure is composed of Mn(O)4(Ow)2 octahedra and H 2 PO 4 2 - tetrahedra, located at C1 sites and forming octahedral-tetrahedral infinite chains which are linked by the oxygen atoms to layers and further to a three-dimensional framework. The proposed hydrogen-bonding scheme provides further linkage within the chains. IR, Raman, TGA and DSC results were interpreted on the basis of the formula of the title compound and its crystal structure.