Synthesis and photophysical properties of multi-branched ethynyl fluorene-labeled molecules

Two kinds of emissive multi-branched molecule based on an ethynyl fluorene were synthesized by cyclotrimerization method. An ethynyl fluorene-labeled three-armed molecule, DBFP was prepared and the other one, CzDBFP has carbazole terminal groups tethered to DBFP. Their absorption and photoluminescent properties were investigated. The spectral analyses indicate that the molecules bearing ethynyl fluorene moieties as a peripheral group can exhibit highly isolated photophysical properties. The multi-branched molecule, CzDBFP was mixed with 2-{2-[2-(4-diethylamino-phenyl)-vinyl]-6-methyl-pyran-4-ylidene}-malononitrile (DCM1) with an optimum concentration. At the low concentration (0.3 wt%) of DCM1, white emission was observed by incomplete energy transfer process from an excited CzDBFP. At the high concentration (3.0 wt%), red emission was predominantly observed, which was attributed to an efficient Förster energy transfer process.