This paper is dedicated to Prof. H. Ila on her 80th birthday for her significant contributions to the field of heterocyclic chemistry.
Abstract
A new series of N-phenyl-carbazole (N-phCbz) appended pyranones were designed and synthesized using α-oxo-ketene-S,S-acetal under mild reaction conditions in good yields. The reactivity of donor-acceptor (D-A)-based 2H-pyranones was utilized to develop their ring-transformed benzene-cored N-phenyl-carbazole derivatives. All the synthesized carbazole-based pyranones showed aggregation-induced emission (AIE) characteristics in 80–99% water fraction (f
w) in DMSO. Among all the synthesized compounds, 6-(4-(9H-carbazol-9-yl)phenyl)-4-(methylthio)-2-oxo-2H-pyran-3-carbonitrile exhibited excellent AIE behavior with ca. 70-fold increase in fluorescence in 80% fw
at 550nm. Furthermore, this compound showed exceptionally high fluorescence in nonpolar solvent (THF) as compared to polar solvents such as DMSO (ca. 200-fold increase in fluorescence). The DFT, DSC, and TGA analyses of the synthesized D-π-A compounds suggested the strong electron-donor ability of N-phCbz, with good thermal stability in the range of 231–393 °C. These N-phenyl-carbazole-appended pyranones with interesting AIE properties have great potential as probes for bioimaging applications as well as for optoelectronic materials.
Key words
carbazole - donor-acceptor - 2
H-pyranones - AIE - fluorescent probes - bioimaging