Large Stokes shift benzothiazolium cyanine dyes with improved intramolecular charge transfer (ICT) for cell imaging applications

Intramolecular Charge Transfer (ICT) is a crucial photophysical phenomenon that can be used to improve the Stokes' shift in fluorescent dyes. The introduction of molecular asymmetry is a promising approach to mitigate significant drawbacks of the symmetric cyanine dyes due to their narrow Stokes' shifts (Delta lambda < 20 nm). In this feature article, we discuss recent progress towards improving the Stokes' shift (Delta lambda > 100 nm) in benzothiazolium-based fluorophore systems via efficient ICT and recent discoveries related to potentially useful live cell imaging applications of these asymmetric cyanine dyes. This article explores three interesting asymmetric benzothiazolium dye designs (D-pi-A, pi-A and D-pi-2A) in detail while discussing their optical properties. The key advantage of these probes is the synthetic tunability of the probe's photophysical properties and cellular selectivity by simply modifying the donor (D) or the acceptor (A) group in the structure. These new asymmetric ICT fluorophore systems exhibit large Stokes' shifts, high biocompatibility, wash-free staining, red to NIR emission and facile excitation with commercially available laser wavelengths.

Automated summary

This article discusses the improvement of Stokes' shift in fluorescent dyes by introducing molecular asymmetry and the potential applications of these asymmetric dyes in live cell imaging. The optical properties of three asymmetric benzothiazolium dye designs are explored in detail. These new asymmetric ICT fluorophore systems exhibit large Stokes' shifts, high biocompatibility, wash-free staining, red to NIR emission, and easy excitation with commercially available laser wavelengths.