A series of deep red fluorescent dyes: synthesis, theoretical calculations and bioimaging applications

Abstract

A series of deep red fluorescent dyes were synthesized and characterized. The optical properties, theoretical calculations, and cytotoxicity of these dyes were investigated. The practical applications of the dyes were also evaluated by fluorescence imaging in living cells. Compared to Rhodamine B (RB), the emission wavelengths of compounds 3a–e were extended to the deep red region (emission maximum ranging from 620 to 650nm) in MeOH. Furthermore, compounds 3a–e exhibited wider Stokes shifts from 100 to 150nm. We also performed time dependent density functional theory (TDDFT) theoretical calculations of 3a–e based on the density functional theory (DFT) optimized structures of the ground S0 state and the first excited S1 state. To test the application of these dyes, we constructed a new Hg2+ fluorescent probe T-2 based on 3d and evaluated its feasibility for fluorescence imaging in living cells. The results suggest that these novel deep red fluorescent dyes can be used a platform to construct fluorescent probes for bioimaging applications.