Optical properties of two bismuth(III) halide hybrids with pyridyl sulfide derivative counter cations

Abstract Low dimensional organic-inorganic hybrid Bi(III) halides, especially those containing organic N, S-heterocycles are amazing as solid state photoluminescent materials, but remain less explored. Herein, two bismuth(III) halide compounds, (Etmp)4Bi2X10 (X = Cl for 1, Br for 2, Etmp = 4-(ethylthio)pyridin-1-ium), are obtained by employing pyridyl sulfide derivative as counter cations. They are determined as zero-dimensional (0D) ionic structures, featuring binuclear bismuth halide anions charge-compensated by (Etmp)+ counter cations. Solid-state UV–Vis diffuse reflectance spectra reveal the wide optical band gaps of 3.20 eV for 1 and 2.67 eV for 2. Notably, 1 exhibits a strong green photoluminescence emission with a quantum yield of 20%, and a CIE chromaticity coordinate of (0.27, 0.36) when irradiated by a 394-nm light. Theoretical calculations suggest that the charge transition between Cl-3p and p-π* anti-bonding orbital of (Etmp)+ is responsible for the emission.