BaM(BS(3))S (M = Sb, Bi): two new thioborate compounds with one-dimensional polymeric chain structure.

Two new quaternary thioborate compounds with strongly one-dimensional growth, BaSb(BS(3))S and BaBi(BS(3))S, have been synthesized using the conventional solid state reaction method in closed tubes at 1100 K. The single crystal X-ray diffraction analysis has shown that compound BaSb(BS(3))S crystallizes in space group Pnma of the orthorhombic system with unit cell parameters of a = 9.6898(15) A, b = 6.2293(13) A, c = 11.670(2) A, V = 704.4(2) A(3), and Z = 4, while compound BaBi(BS(3))S crystallizes in space group C2/m with unit cell parameters of a = 14.9890(17) A, b = 6.2457(6) A, c = 7.5591(9) A, beta = 101.604(5) degrees , V = 693.19(13) A(3), and Z = 4. The two compounds both crystallize in the structure of infinite one-dimensional chains with BS(3) trigonal plane coordination alternately bridged by MS(3) (M = Sb, Bi) trigonal pyramids through sharing two sulfur atoms along the crystallographic b axis. First-principles electronic structure calculations performed with the density functional theory (DFT) method show that the calculated band gaps of BaSb(BS(3))S and BaBi(BS(3))S are 2.29 and 2.16 eV, respectively, which are in good agreement with the experimental values estimated from UV-vis absorption spectra using the Kubelka-Munk equation, and the observed absorption peak is assigned as charge transfers from S-3p states to Sb-5p (Bi6p) states.