AMTES(3) (A=K, RB, CS M=CU, AG) - A NEW CLASS OF COMPOUNDS BASED ON A NEW POLYCHALCOGENIDE ANION, TES32-

The reaction of Cu or Ag with mixed polychalcogenide flux A(2)S(x)Te(y) (A = K, Rb, Cs) yielded RbCuTeS3 (1), CsCuTeS3(2),alpha-KAgTeS3 (3),beta-KAgTeS3(4),RbAgTeS3(5), and CsAgTeS3 (6) possessing new structure types. Compounds 1, 4, 5, and 6 are two-dimensional and isostructural. They crystallize in the monoclinic space group P2(1)/c, with a = 7.434(3)(A)ngstrom, b = 10.526(3) Angstrom c = 8.234(3) Angstrom, beta = 106.13(3)degrees, V = 619.0(7) Angstrom(3) for 1; a = 7.340(2) Angstrom, b = 10.647(2)Angstrom,c = 8.504(2)Angstrom, beta = 106.46(2)degrees, V = 637.4(3) Angstrom(3) for 4; a = 7.566(8)Angstrom, b = 10.724(8)Angstrom, c = 8.586(9) Angstrom,beta = 106.36(8)degrees,V = 668(2) Angstrom(3) for 5; and a = 7.832(6)Angstrom, 6 = 10.803(7)Angstrom, c = 8.668(8)Angstrom, beta = 106.05(6)degrees( V = 705(2) Angstrom(3) for 6. The structure consists of anionic [MTeS(3)],(n-)(n) ( (M = Cu or Ag) layers and charge-compensating alkali ions between the layers. Each layer is composed of tetrahedrally coordinated Cu+ or Ag+ centers and trigonal pyramidal TeS32- units, joined together via bridging S atoms. Compound 2 is three-dimensional and crystallizes in the cubic space group P2(1)3 with a = 9.107(3)Angstrom and V = 755.4(2) Angstrom(3). its framework is composed of trigonal planar Cu+ centers and TeS32- units. Compound 3 is two-dimensional and crystallizes in the monoclinic space group P2(1)/n with a = 6.171(2)Angstrom, b = 16.406(4)Angstrom, c = 6.318(3)Angstrom, W, S = 97.32(3)degrees, and V = 634.4(7)Angstrom(3). The structure of [AgTeS3](n-)(n) layers is different from those of 1, 4, 5, and 6, but the TeS32- units bridge Ag+ centers by the same pattern. All compounds are found to be wide band gap semiconductors with RbCuTeS3 possessing the narrowest at 1.95 eV. Thermal analysis studies show that 3, 5, and 6 are the most stable.