Indolo[3,2-b]carbazole derivatives with high fluorescent emission both in solution and aggregated states and mechanical-induced emission enhancement characteristic

Abstract

Four novel indolo[3,2-b]carbazole derivatives (F-ICZ, 2F-ICZ, F-ICZ-Ben and 2F-ICZ-Ben) with A-π-D-π-A structure were designed and synthesized via Knoevenagel and Suzuki-Miyaura reactions. The photophysical properties of indolo[3,2-b]carbazole derivatives in different solvents, aggregates emission behaviors and solid state were investigated systematically. The compounds exhibited an obvious solvatochromic effect. Compounds F-ICZ and 2F-ICZ showed AIEE property in tetrahydrofuran-water mixture solution, and compounds F-ICZ-Ben and 2F-ICZ-Ben exhibited high fluorescent emission both in solution and aggregated states. The significant reasons may be the increase of conjugate degree in solution and no obviously π-π stacking in aggregated state. Furthermore, compound F-ICZ possessed mechanofluorochromic property, and F-ICZ-Ben exhibited mechanical-induced emission enhancement characteristics. The reasons for mechanofluorochromic property are the changes in molecular packing patterns. This work further provided an efficient strategy for designing more mechanofluorochromic materials with high fluorescent emission both in solution and aggregated states.