Modulating optical and electrochemical properties of perylene dyes by twisting aromatic π-system structures

Abstract Three highly fluorescent perylene bisimide dyes were synthesized, where aromatic π-system structures are twisted to different degree by steric hindrance of two or four substitution groups at bay position. Light-emitting colours of these dye solutions can be modulated from green, yellow to red, and their fluorescence quantum yields increase up to approximate 100% with increasing the π-system twisting, which can be considered for new class of wavelength-tunable dye lasers. π-Twisted dyes are more sensitive to microenvironment changes. Thus, they are better fluorescence probe and sensory materials than planar dyes. Electrochemical cyclic voltammetry measurements revealed that these dyes are suitable for n-type optoelectrical devices and materials. These dye solids display near infra-red emission at 600-850 nm. Owing to strong π-π stacking interaction, planar dye solid loses its outstanding optical properties compared to its solution. In contrast, π-twisted dye solids retain their excellent optical properties including narrow emission bands and relatively high fluorescence quantum yields due to the suppression of π-π stacking interaction. Exceptional fluorescence polarization phenomena were observed for these π-twisted dye solids. These optical results revealed that π-twisted perylene bisimide dyes are more excellent optical materials than planar dyes.