Synthesis and photophysical properties of donor-acceptor flavone-based derivatives with good aggregation-induced emission characteristics.

Four novel compounds (1 – 4) were synthesized using 2-phenyl-4H-1-benzopyran-4-one (flavone) moiety as an acceptor and phenoxazine, phenothiazine, 9,9-dimethyl-9,10-dihydroacridine, diphenylamine as donors. Their photophysical properties were studied with spectroscopic and theoretical methods. The results show that 1 and 2 exhibit good aggregation-induced emission (AIE) properties in tetrahydrofuran (THF)/water mixtures, whose maximum photoluminescence (PL) intensities are 156- and 187-fold higher than those in pure THF solutions, and can reach 256- and 506-fold higher than those in the mixtures at water fractions of 50%, respectively. 3 displays similar PL property except for obvious emission in pure THF solution. However, PL intensity of 4 decreases with an increase in water fraction, and then is enhanced with further increase in water fraction. Moreover, 4 shows high quantum yields both in toluene solution (0.61) and in solid state (0.83). It exhibits a positive solvatochromism. In addition, 2 possesses mechanofluorochromic transition from sky blue to yellow after grinding. It can also be applied in live-cell imaging. Image 1 • 1 – 4 with rich photophysical properties were synthesized using flavone unit as an acceptor and conjugated amines as donors. • PL intensities of 1 and 2 in THF/water mixturescan reach 156- and 187-fold higher than those in THF solutions, respectively. • 4 has quite high quantum yields both in toluene solution (0.61) and in solid state (0.83). It exhibits a positive solvatochromism. • 2 exhibits reversible mechanofluorochromic transition between sky blue and yellow. It could be applied in L929 cell imaging. [ABSTRACT FROM AUTHOR]