Synthesis, characterization and fluorescence properties of boron difluoride pyridyl-β-diketonate derivatives.

Five pyridyl-β-diketones were synthesized by Claisen condensation of ethyl nicotinate with various aryl methyl ketones in benzene in the presence of sodium amide as the base, and then reacted with boron trifluoride diethyl etherate in dichloromethane to afford some new boron difluoride pyridyl-β-diketonate derivatives. The compounds obtained were characterized using FTIR, (1)H NMR, elemental analysis and mass spectrometry. Their optical properties were studied in DMF by UV-vis absorption and fluorescence spectroscopy. The results showed that these boron complexes exhibited intense fluorescence in the blue-green region (420-490 nm) under UV radiation with a relatively high quantum yield. Especially, compounds 4b and 5b displayed much higher quantum yield as compared to compounds 1b, 2b and 3b.