Design, Synthesis, and Characterization of Functionalized Silepins: High Quantum Yield Blue Emitters
文摘
The synthesis of a family of 1,1-dimethyldibenzo[b,f]silepin derivatives, substituted with donor groups of various donor strength and conjugation length in the positions meta or para to the silepin silicon, is presented. The compounds were characterized by NMR, UV鈭抳is, and fluorescence spectroscopy, as well as with cyclic voltammetry and DFT computations. One of the meta series was characterized by X-ray crystallography. All compounds show red-shifts in onset absorption and emission maxima compared to the parent 1,1-dimethyldibenzo[b,f]silepin, but all exhibit blue fluorescence with quantum yields ranging from 0.46 to 0.93 for the meta series and from 0.09 to 0.46 for the para derivatives. The data suggest that, for the meta series, the primary absorption is of 蟺鈭捪€* character, while in the para series, for strongly donating groups, transitions from low-lying 蟺 orbitals to the LUMO+1 orbital, which has contributions from the C鈭扴i鈭扖 蟽* orbitals, are charge-transfer in character. The phenyl-substituted derivatives can be converted to borepins via transmetalation with BBr3, but other strategies are necessary to prepare borepins with other donor groups.