K3BiAs6Se12: A two-dimensional bismuth selenoarsenate containing crown-shaped anions [As3Se6]3−

Single crystals of K3BiAs6Se12 were obtained from the reaction of Bi, with in situ formed fluxes of K2Se3, As2Se3, and Se at 500 °C. The compound crystallizes in the trigonal space group P  3¯ (No. 147) with a = 9.7478(7), c = 7.6525(6) Å, V = 629.72(8) Å3, Z = 1. The [Bi(As3Se6)2]3− anion possesses a two-dimensional layered structure with trigonal symmetry consisting of [BiSe6] octahedra and crown-like cyclic [As3Se6]3− units formed by three corner-sharing trigonal pyramidal [AsSe3]3− anions. The [As3Se6]3− fragment is located on a 3-fold axis with three As atoms and three Se atoms forming a six-membered ring in chair conformation. The Bi3+ ion is in an almost perfect octahedral geometry. The overall arrangement of the Bi3+ cations and the [As3Se6]3− anions is related to the CdI2-type structure with the cations situated on the Cd2+ and the anions on the I− sites, respectively.The K+ cations are located between the [Bi(As3Se6)2]3− layers. The K(1)+ cation is coordinated by 9 Se2− anions from four [As3Se6]3− units, one above and three below, in an irregular geometry, whereas the K(2)+ cation is surrounded by six Se2− anions from four [As3Se6]3− units, two above and two below, in a perfect octahedral fashion. The title compound is characterized with UV/vis diffuse reflectance spectroscopy, IR and Raman spectra.

Research highlights▶ The first quaternary bismuth selenoarsenate K3BiAs6Se12 was obtained in an in-situ formed reactive flux. ▶ The unique structure features [BiSe6] octahedra and crown-shaped [As3Se6]3− rings joined via Se2− anions to form a two-dimensional [Bi(As3Se6)2]3− anionic layer.