Solvothermal Synthesis of [C6H17N3]Sb10S16: A New Thioantimonate(III) with an in-situ Formed Organic Amine Cation

Abstract

Abstract The new thioantimonate(III) [C6H17N3][Sb10S16] (C6H17N3 = 2-piperazine-N-ethylamine cation) was obtained under solvothermal conditions showing a unique anionic framework. The compound crystallizes in the monoclinic space group P21/c with four formula units in the unit cell. The lattice parameters are a=11.530(2), b=25.042(5), c = 13.709(3)Å, β =111.25(3)◦,V = 3689(2) Å3. The thioantimonate(III) anion is formed by interconnection of nine trigonal pyramidal SbS3 units and one SbS4 moiety. These primary building units share common corners and edges yielding Sb3S3 and Sb2S2 hetero-rings. Further condensation leads to strong undulated two atoms thick layers extending in the [010] direction, with a modulation period of about 14 Å. Very large Sb31S31 rings within the layers show a ‘double-ellipsoidal’ shape with approximate dimensions of 8.9 ・ 9.3 Å. The cations are located at the inflexion points of the layers and act as pillars between successive layers. The layers are stacked onto each other in a way that channels parallel to [001] are formed accommodating the organic cations. A remarkable observation is that the 2-piperazine-N-ethylamine cation is formed by cyclization of tren molecules (tren = tris(2-aminoethyl)amine) under in-situ conditions.