Effects of chalcogen atom variation in chalcogenadiazole fused indolo[2,3-a]carbazoles

Abstract

A series of chalcogenadiazole fused indolo[2,3-a]carbazoles 1–3 were prepared, wherein a chalcogen atom was varied from oxygen (O) to sulphur (S) to selenium (Se) in the chalcogenadiazole unit. A Cadogan ring closing reaction was used as the key synthetic step for the preparation of 1–3. The chalcogen alteration (O, S and Se) led to a significant change in the structural, optical and electrochemical properties of 1–3, indicating a subsequent change in their HOMO–LUMO energy levels. Density functional theory (DFT) calculations were performed to further support the experimentally observed trend.