Near blue light emitting benzimidazol-2-thione

Abstract

The discrete organosulfur molecule possessing a high quantum yield with blue luminescence properties has significant potential as an optically active material for future applications. In this context, the sulfoxide or sulfone-based fused heterocyclic materials are known as the new generation of luminogens. The first sulfur-fused heterocyclic thioketone luminogen consisting of a donor–acceptor structure has been reported in this work, with benzimidazole and sulfur acting as the donor, whereas anthracene and pyridine moieties act as the acceptor. Herewith, we report the synthesis of 1-(9-methyl anthracene)-2-(2-methyl pyridine)-benzimidazol-2-thione (APBT). The donor and acceptor are connected through a methyl linker. Molecule APBT emits at λ_em = 494 nm in the crystalline state and λ_em = 410 nm in the solution state. Besides, molecule APBT showed an aggregation-induced emission due to its molecular packing in the crystalline state. The molecule emits in the near blue region in the crystalline state with a quantum yield of 17.82% and a luminescent lifetime of 47.19 ns. The light-emitting behaviour of crystalline APBT is comparable with APBT-coated LED. DFT calculations were performed to determine the energy of frontier molecular orbitals, and the HOMO–LUMO gap (HLG) was found to be 3.45 eV.