Synthesis and characterization of three new layered phosphates, Na2MnP2O7, NaCsMnP2O7, and NaCsMn0.35Cu0.65P2O7

Three new layered phosphates were isolated by employing high-temperature, solid-state reactions. These compounds belong to the A(2)(I)B(II)P(2)O(7) family. Na2MnP2O7, 1, crystallizes in the triclinic space group <P(1)over bar> (No. 2) with a = 5.316(2) Angstrom, b = 6.580(2) Angstrom, c = 9.409(3) Angstrom, alpha = 109.65(3)degrees, beta = 95.25(3)degrees, gamma = 106.38(3)degrees, and Z = 2; NaCsMnP2O7, 2, crystallizes in the orthorhombic space group Cmc2(1) (No. 36) with a = 5.332(2) Angstrom, b = 15.009(2) Angstrom, c = 9.808(2) Angstrom, and Z = 4; NaCsMn0.35Cs0.65P2O7, 3, also crystallizes in the orthorhombic space group Cmc2(1) (No. 36) with a = 5.208(2) Angstrom, b = 15.073(5) Angstrom, c = 9.708(3) Angstrom, and Z = 4. 1 possesses a new structure type composed of slabs of fused Mn4P4O26 cages, and 2 and 3 are isostructural with K2CuP2O7. The unique cage structure found in 1 is made of two edge-sharing Mn2O10 dimers and two P2O7 pyrophosphate groups. These units, arranged in parallel with respect to Mn-Mn and P-P vectors, are linked in an alternating fashion through corner-sharing oxygen atoms. Incorporation of larger Cs+ cations leads to a different structure in 2 and 3, while substituting similarly sized Cu2+ for Mn2+ cations in 3 does not alter the structure type. Magnetic susceptibility measurements as well as bond valence sum calculations confirm the valence states of cations, including the high-spin, d(5) Mn2+ cation. UV-vis and IR spectra of 1 and 2 are presented. In this report, the discrete nature of the manganese oxide lattices is discussed.