QUATERNARY RB2CU2SNS4, A2CU2SN2S6 (A = NA, K, RB, CS), A2CU2SN2SE6 (A = K, RB), K2AU2SNS4, AND K2AU2SN2S6 - SYNTHESES, STRUCTURES, AND PROPERTIES OF NEW SOLID-STATE CHALCOGENIDES BASED ON TETRAHEDRAL [SNS4]4-UNITS

Rb2Cu2SnS4 (I) and Rb2Cu2Sn2S6 (II) were synthesized by heating a mixture of Sn, Cu, Rb2S, and S in the ratios of 1:4:4:16 and 1:1-2:4:16, respectively, at 400-degrees-C for 4 days. K2Au2SnS4 (III) and K2Au2Sn2S6 (IV) were synthesized by heating mixtures of Sn, Au, K2S, and S in the ratios of 1:2:4:16 and 1:1.5:2:16, respectively, at 350-degrees-C for 4 days. The structures were characterized by single-crystal X-ray diffraction techniques, infrared spectroscopy and UV-vis-near-IR reflectance spectroscopy. Crystal data for I: space group Ibam (No. 72); a = 5.528(4) angstrom, b = 11.418(6) angstrom, c = 13.700(6) angstrom; Z = 4; V = 865(2) angstrom3; d(calc) = 4.185 g/CM3; number of data collected 468; number of data observed (I > 3sigma(I)) 221; number of variables 23; final R/R(W) = 6.9/8.1. Crystal data for II: space group C2/c (No. 15); a = 11.026(2) angstrom, b = 11.019(3) angstrom, c = 20.299(4) angstrom, beta = 97.79(2)-degrees; Z = 8; V = 2444(1) angstrom3; d(calc) = 3.956 g/cm3; number of data collected 11 691; number of data observed (I > 3sigma(I)) 1756; number of variables 111; final R/R(W) = 6.3/6.4. Crystal data for III: space group P1 (No. 2); a = 8.212(4) angstrom, b = 9.110(4) angstrom, c = 7.314(2) angstrom, alpha = 97.82(3)-degrees, beta = 111.72(2)-degrees, gamma = 72.00(2)-degrees, V = 483.2(7) angstrom3; Z = 2; d(calc) = 4.941 g/CM3; number of data collected: 1832; number of data observed (I > 3sigma(I)) 1447; number of variables 83; final R/R(W) = 4.8/6.0. Crystal data for IV: space group P4/mcc (No. 124); a = b = 7.968(2) angstrom, c = 19.200(6) angstrom, V = 1219(1) angstrom3, z = 4; d(calc) = 4.914 g/CM3; number of data collected 911; number of data observed (I > 3sigma(I)) 459; number of variables 34; final R/R(W) = 4.1/3.9. 1 has a two-dimensional structure which contains CuS4 and SnS4 tetrahedra in the ratio of 2:1 as building blocks. The [Cu2SnS4]2- layers are best described as an ordered defect anti-PbO type structure. The rubidium cations are found between the layers. II is a layered structure which contains corner-sharing SnS4 and CUS4 tetrahedra and can be viewed as a derivative of adamantine type structure. Both III and IV have one-dimensional structures. The anionic chains of III contain linear AuS2 and SnS4 tetrahedra in the ratio of 2:1, while IV contains linear AuS2 and Sn2S6 edge-sharing bitetrahedra also in the ratio of 2:1. The charges are balanced by potassium cations located between the chains. Infrared spectra for I-IV are reported. I-IV are semiconductors with optical bandgaps of 2.08, 1.44, 2.75, and 2.30 eV, respectively.