SYNTHESIS, STRUCTURE, AND CHARACTERIZATION OF NA2CUSBS3, A NEW SULFOSALT DERIVATIVE FROM SUPERCRITICAL ETHYLENEDIAMINE

Single crystals of disodium copper(I)trisulfidoantimonate(III), Na2CuS bS3, were synthesized from a reaction of Na2CO3, Cu, Sb2S3, and S in s upercritical ethylenediamine (350 degrees C, 6d) as dark orange bars. Na2CuSbS3 was analyzed by single crystal and powder X-ray diffraction, differential scanning calorimetry, SEM/EDAX, and far-IR spectroscopy. Cell parameters as determined by single crystal X-ray diffraction are : monoclinic, space groups P2(1)/n (no. 14), a= 5.847(2)Angstrom, b= 1 7.146(5)Angstrom, c= 6.776(2)Angstrom, beta= 113.21(2)degrees, V= 624. 3(3)Angstrom(3), Z=4, R= 0.0256, R(W)= 0.0292. The compound has a two- dimensional structure with the layers stacking along the y axis. The a nionic CuSbS32- layers are formed by SbS33- trigonal pyramids corner-s hared to trigonal planar Cu(I) centers, as is characteristic of many s ulfosalts. Each Sb(III) center has one terminal sulfide pointing into the interlayer spaces, but all other S atoms in the compound function as either mu(2) or mu(3) bridging units. The Na+ ions provide charge s eparation between the anionic layers with a minimum Na-S contact dista nce of 2.801(4)Angstrom. Assignment of formal oxidation states to the metal atoms was confirmed by bond valence sum calculation. Analysis of Na2CuSbS3 by solid state optical reflectance spectroscopy indicates a n indirect band gap, E(g), of 1.84 eV, suggesting that the compound is a semiconductor.