Tuning of environment-sensitive 3-hydroxychromone fluorophores based on strong donor substituents in positions 2 or 7

Abstract

We have synthesized a series of environmentally sensitive fluorophores based on 3-hydroxychromone with systematically varied aromatic groups at positions 2 and 7. The two families of 2,7-diaryl-3-hydroxychromones were synthesized using Suzuki coupling from the corresponding 2-aryl-7-bromo-3-hydroxychromones. These chromophores exhibit a dual fluorescent emission and a strong response to changes in environmental polarity in organic solvents. Both experimental determination and calculations of dipole moment changes show stronger charge transfer in compounds with an electron donor group at position 7 compared to position 2. Their emission is almost totally quenched in the aqueous medium, while the increase in quantum yield upon binding to biological molecules serves as a useful characteristic. Particularly, compounds with strong donors in position 7 are sensitive to diverse lipid environments, whereas those with strong donors in position 2 have different emission profiles for distinct protein interactions. The complex behavior of the probes was evaluated using spectral phasor analysis. Altogether, these novel families of probes may help monitor several biological processes in vitro and in cell cultures.