Synthesis, crystal structures and fluorescence properties of 3-(2-pyridyl)coumarin derivatives

Two new coumarin derivatives, 7-(diethylamino)-3-(pyridin-2-yl)coumarin (DAPC) and 3-(pyridin-2-yl)-benzo[5,6]coumarin (PBC), were synthesized and characterized by elemental analysis, 1H NMR, FT-IR and UV–vis absorption spectra. Their structures were determined by X-ray crystallography single crystal analysis. The fluorescence behaviors of the compounds in dichloromethane solutions were observed. The results show that the compound DAPC exhibits high fluorescence quantum yield (0.84) and they exhibit strong blue emissions under ultraviolet light excitation. The energy levels of the HOMO and LUMO of the compounds have been calculated with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) at B3LYP/6-31G(d) level.