Synthesis and photophysical properties of difluoroboronated β-diketones with the fluorene moiety that have high fluorescence quantum yields

Difluoroboronate β-diketones, compounds 1 having the fluorene moiety and the phenyl groups as well as the ligating precursors of the corresponding β-diketones, compounds 2 were synthesized. The photophysical features of compounds 1 were investigated based on the measurements of fluorescence yields and lifetimes, and transient absorption. Compounds 1 are significantly fluorescent with quantum yields of ca. 0.95 in acetonitrile and ca. 0.90 in chloroform. Fluorescence from compounds 1 was observed also in the solid state. Observation of extremely weak triplet-triplet absorption spectra of compounds 1 verifies the large fluorescence quantum yields.