Synthesis and Structures of New Layered Ternary Manganese Selenides: AMnSe2 (A=Li, Na, K, Rb, Cs) and Na2Mn2Se3
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The synthesis and crystal structures of new ternary manganese selenides, AMnSe2 (A = Li, Na, K, Rb, Cs) and Na2Mn2Se3, are reported. These compounds were synthesized by solid state reaction and cation exchange techniques. The single-crystal structures of AMnSe2 (A = Li, Na, Rb) and Na2Mn2Se3 have been determined; LiMnSe2: a = 4.1905(3) Å, c = 6.619(2) Å, and P3m1 (No. 156, Z = 1); NaMnSe2: a = 4.2330(7) Å, c = 6.942(3) Å, and P3m1 (No. 156, Z = 1); RbMnSe2: a = 4.2660(4) Å, c = 14.033(2) Å, and I4̄m2 (No. 119, Z = 2); Na2Mn2Se3: a = 15.689(2) Å, b = 13.888(2) Å, c = 7.220(1) Å, β = 115.65(2)°, and C2/c (No. 15, Z = 8). The fundamental building blocks of the title compounds are MnSe4 tetrahedra. AMnSe2 (A = Li, Na) are layered compounds in which MnSe4 tetrahedra share three corners in the formation of polar 2∞[MnSe3/3Se]- layers. AMnSe2 (A = K, Rb, Cs) exhibit 2∞[MnSe4/2]- layers which are built up by four-corner-shared MnSe4 tetrahedra. Na2Mn2Se3 shows four-membered zigzag chains formed by edge-shared MnSe4 tetrahedra. These chains are fused by the remaining apices to form a two-dimensional layer, 2∞[MnSe2/3Se1/3 Se1/2]-. Magnetic susceptibility data for these compounds were fit with a modified Curie-Weiss expression. © 1999 Academic Press.
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Kim, Joonyeong||Hughbanks, Timothy