Donor–Acceptor–Acceptor-Conjugated Dual-State Emissive Acrylonitriles: Investigating the Effect of Acceptor Unit Order and Biological Imaging

The effect of acceptor unit order on the photophysical properties of two distinct donor–acceptor–acceptor conjugated fluorescent acrylonitriles, TPA-AN-PhBT and TPA-BT-ANPh, was systematically investigated. Compared with faintly emissive TPA-AN-PhBT in solution, TPA-BT-ANPh showed strong red-shifted fluorescence. TPA-AN-PhBT and TPA-BT-ANPh exhibited enhanced green and deep red emissions with remarkable fluorescence quantum yields up to 44% in the solid state. In addition, TPA-BT-ANPh possessed stronger two-photon absorption than TPA-AN-PhBT. Furthermore, these biocompatible dyes served as excellent fluorescent markers for specific lipid droplet imaging.