Mercury Bismuth Chalcohalides, Hg3Q2Bi2Cl8 (Q = S, Se, Te): Syntheses, Crystal Structures, Band Structures, and Optical Properties

Three quaternary mercury bismuth chalcohalides, Hg(3)Q(2)Bi(2)Cl(8) (Q = S, Se, Te), are reported along with their syntheses, crystal structures, electronic band structures, and optical properties. The compounds are structurally similar with a layer comprised of a hole perforated sheet network of [Hg(3)Q(2)](2+) (Q = S and Te) that forms by fused cyclohexane, chairlike Hg(6)Q(6) rings. The cationic charge in the network is balanced by edge-sharing monocapped trigonal-prismatic anions of [Bi2Cl8](2-) that form a two-dimensional network located between layers. Compound 1, Hg(3)Q(2)Bi(2)Cl(8), crystallizes in the monoclinic space group C12/m1 with a = 12.9381(9) angstrom, b = 7.3828(6) angstrom, c = 9.2606(6) angstrom, and beta = 116.641(5)degrees. Compound 2, Hg(3)Q(2)Bi(2)Cl(8), crystallizes in the monoclinic space group C12/c1 with a = 17.483(4) angstrom, b = 7.684(2) angstrom, c = 13.415(3) angstrom, and beta = 104.72(3)degrees. The crystals of the Hg(3)Q(2)Bi(2)Cl(8) analogue exhibit complex modulations and structural disorder, which complicated its structural refinement. Compounds 1 and 2 melt incongruently and show band gaps of 3.26 and 2.80 eV, respectively, which are in a good agreement with those from band-structure density functional theory calculations.