Studies on Donor-Acceptor Substituted with Triphenylamine-Core Fluorescent Derivatives

A series of donor-acceptor (D-A) substituted with triphenylamine-core fluorescent derivatives have been synthesized via nucleophilic addition of Grignard reagent to 2,7-dibromo-9-fluorenone, CF3SO3H-promoted Friedel-Crafts reaction, Ullmann coupling reaction, and Pd-catalyzed Suzuki cross-coupling reaction in turn. Aromatic imide (N-phthalimide) group was firstly introduced as electron acceptor in the donor-π-acceptor (D-π-A) opto-electronic materials. Hole-injection capability of the fluorene derivatives were promoted by introducing 4-methyl-triphenylamine (MTPA) group at the 9-position. All these compounds present excellent solubility and thermal stability (with glass transition temperature of 191-279 °C), thermo gravimetric analysis (TGA) indicated that 5% or 10% weight losses occurred at about 415-463 °C or 427-498 °C respectively. The relationship of the solvent polarity or the conjugation length of the D-A structure with the luminescent properties has been studied by the UV-vis spectra and the fluorescent spectra. The CV data revealed that these fluorescent derivatives are possessed low-lying HOMO energy levels ranging from -5.19 to -5.37 eV and are exhibited strong blue-green luminance around 448-546 nm.