Synthesis, crystal structure, vibrational and optical properties of new Bi(III) halide complex (tris(2-amino-5-(methylthio)-1,3,4-thiadiazol-3-ium) hexachlorobismuthate(III)): [C3H6N3S2]3BiCl6

The new organic–inorganic hybrid zero-dimensional bismuth-chloride based compound: (C3H6N3S2)3BiCl6, was synthesized by slow evaporation at room temperature. Single-crystal X-ray diffraction analysis indicates that the compound belongs to the triclinic crystal system with the centrosymmetric space group P-1. The asymmetric unit contains one octahedral geometry of [BiCl6]3- and three protonated cations (C3H6N3S2)+. In the crystal structure, the isolated [BiCl6]3- anions are linked to organic cations via N–H⋯Cl and C–H⋯Cl hydrogen bonds. Vibrational assignments of (C3H6N3S2)3BiCl6 are interpreted by FT-IR and Raman spectroscopic studies. The optimized molecular structure and vibrational frequencies were calculated by the Density Functional Theory (DFT) method using the B3LYP function with the LanL2DZ basis set. It shows a good agreement between the calculated and the experimental vibrational frequencies. The crystal packing is stabilized by N/C–H⋯Cl interactions whereas the van der Waals contacts play a key role in the consolidation of the 3D packing as verified by Hirshfeld surface analysis in combination with 2D fingerprint plots. The two-dimensional fingerprint plots reveal that the structure is dominated by Cl⋯H/H⋯Cl, H⋯N/N⋯H and H⋯H contacts. The crystal exhibits the thermal stability up to 270 °C using thermal analysis. The proton affinity (PA) values of the protonated AMT have been theoretically estimated on the basis of DFT calculations. The fluorescence measurements show two blue peaks which are attributed to band to band and excitonic emissions within the chlorobismuthate octahedron.