Triarylpyrylium-based fluorescent DNA-binding dyes - facile synthesis, substituent effects, and sensing mechanism.

Novel pyrylium-based fluorescent DNA-binding dyes were developed, containing -aminoaryl groups at the positions of the pyrylium moiety. The amines are substituted with aminoalkyl groups to enhance the dye's water solubility and DNA binding affinity. With this structural modification triarylpyryliums exhibit up to 7.6 times higher fluorescence enhancement upon binding to DNA, rendering them promising candidates for fluorogenic DNA sensors. The photochemical characteristics of the dyes, including the radiationless deexcitation pathways necessary for the DNA-induced fluorogenicity were studied using both spectroscopical experiments and theoretical calculations. Particular attention was given to the possibility of twisted intramolecular charge transfer (TICT) states as a quenching pathway in the unbound state. These findings support the rational design of structurally dynamic, environment-sensitive fluorophores for nucleic acid detection and molecular diagnostics.