Excimers Beyond Pyrene: A Far‐Red Optical Proximity Reporter and its Application to the Label‐Free Detection of DNA

A family of organic chromophores that, like pyrene, forms emissive excimers is reported. Their chemical and photophysical properties are superior to pyrene for the design of chemo‐ and biosensors. Unlike hydrophobic pyrene, which requires excitation by cell‐damaging UV irradiation, these polar dyes absorb strongly in the visible range, and their excimers emit brightly in the red to far‐red region of the electromagnetic spectrum. The intensity of the emission signal is greatly increased upon formation of a preassociated dimer that is triggered upon aggregation or crystallization. In demonstration of the potential of this new family of excimer‐forming dyes, a probe that is capable of detecting label‐free DNA in water down to 10 p M and also doubles as a visualization agent for DNA in gel electrophoresis is reported.