Synthesis of Luminescent 2-7 Disubstituted Silafluorenes with alkynyl-carbazole, -phenanthrene, and -benzaldehyde substituents

Three new fluorescent 2,7-alkynyl(aryl)-3,6-dimethoxy-9,9-diphenylsilafluorenes have been synthesized using a Pd-catalyzed Sonogashira coupling reaction to incorporate alkynyl(aryl) groups at the 2,7-positions of the ring. The substituents include 9-ethynylcarbazole, 4-ethynylbenzaldehyde, and 3-ethynylphenanthrene. These new compounds were characterized utilizing X-ray crystallography as well as multinuclear NMR, mass spectrometry, UV-Vis, and fluorescence spectroscopic techniques. These silafluorenes, which are yellow crystals in the solid state, showed high quantum yields with moderate molar extinction coefficients in dichloromethane and strong blue emission. Key words: silafluorene, luminescence.