近红外染料抗对称性破缺的构效关系研究

Rational design of high-performance near-infrared (NIR) dyes for deep-tissue in vivo fluorescence imaging represents a frontier in dye chemistry. Due to large transition dipole moments, NIR dyes are prone to solvent-induced symmetry breaking (Peierls transition) in polar solvents, leading to a significant reduction in molar extinction coefficients. Inhibiting symmetry breaking remains a critical challenge in this field. Our previous studies revealed that EC5 dyes exhibit superior resistance to symmetry breaking compared to cyanine, maintaining excellent molar extinction coefficients in both polar and non-polar solvents. We hypothesize that the two double bonds above the conjugated chain (clavicular double bonds) in EC5 dyes are key to this resistance. To test this hypothesis, we synthesized ES5 molecules with saturated carbon chains for parallel comparison. Analysis of photophysical properties, spectral deconvolution data, and crystal structures confirmed that these double bonds enhance the dye’s resistance to symmetry breaking, enabling high brightness even in polar solutions. This work provides novel insights into the structure-property relationship governing symmetry-breaking resistance, offering guidance for designing next-generation high-performance NIR dyes.