Anti-solvatochromic and highly emissive twisted D-A structure with intramolecular hydrogen bond

Electron donor-acceptor (D-A) structures are the most common strategy to develop fluorescent dyes with high quantum yields in solution and the solid state. However, most D-A-type fluorescent dyes are confronted with the problem of a decrease in quantum yield (phi) with an increase in solvent polarity. To solve this problem, we construct a D-A-type fluorescent dye via modification of its structural engineering, introducing a core unit of the intramolecular H-bond with a highly rotational barrier to limit energy loss through molecular vibration and rotation. Our results exhibit almost the same quantum yields (phi > 96%) with the increase of solvent polarity from toluene to DMSO. Furthermore, our fluorescent dyes show good emission efficiency with an absolute quantum yield up to 51.5 +/- 0.3% in the solid state. Efficient bioimaging in EJ cells has been well realized after incubation with low to high concentrations of fluorescent dye as the probe. The strategy of structural engineering will provide chemical versatility to obtain molecular structures with unique photophysical features.

Automated summary

Electron donor-acceptor (D-A) structures are commonly used to develop fluorescent dyes with high quantum yields, but most D-A-type dyes experience a decrease in quantum yield with increasing solvent polarity. By modifying the structural engineering and introducing an intramolecular H-bond core unit with a rotational barrier, we have created a D-A-type fluorescent dye that maintains almost the same quantum yields across a range of solvent polarities.