83651-28-9Relevant articles and documents
Tunable fluorophores based on 2-(N-Arylimino)pyrrolyl chelates of diphenylboron: Synthesis, structure, photophysical characterization, and application in OLEDs
Suresh,Lopes, Patricia S.,Ferreira, Bruno,Figueira, Claudia A.,Gomes, Clara S. B.,Gomes, Pedro T.,Di Paolo, Roberto E.,MacAnita, Antonio L.,Duarte, M. Teresa,Charas, Ana,Morgado, Jorge,Calhorda, Maria Jose
, p. 4126 - 4140 (2014/04/17)
Reactions of 2-(N-arylimino)pyrroles (HNC4H3C(H)=N- Ar) with triphenylboron (BPh3) in boiling toluene afford the respective highly emissive N,N-boron chelate complexes, [BPh2{κ 2N,N-NC4H3C(H)=N-Ar}] (Ar=C6H 5 (12), 2,6-Me2-C6H3 (13), 2,6-iPr2-C6H3 (14), 4-OMe-C6H 4 (15), 3,4-Me2-C6H3 (16), 4-F-C6H4 (17), 4-NO2-C6H4 (18), 4-CN-C6H4 (19), 3,4,5-F3-C 6H2 (20), and C6F5 (21)) in moderate to high yields. The photophysical properties of these new boron complexes largely depend on the substituents present on the aryl rings of their N-arylimino moieties. The complexes bearing electron-withdrawing aniline substituents 17-20 show more intense (e.g., φf=0.71 for Ar=4-CN-C6H4 (19) in THF), higher-energy (blue) fluorescent emission compared to those bearing electron-donating substituents, for which the emission is redshifted at the expense of lower quantum yields (φf=0.13 and 0.14 for Ar=4-OMe-C6H4 (15) and 3,4-Me2-C6H3 (16), respectively, in THF). The presence of substituents bulkier than a hydrogen atom at the 2,6-positions of the aryl groups strongly restricts rotation of this moiety towards coplanarity with the iminopyrrolyl ligand framework, inducing a shift in the emission to the violet region (λmax=410-465-nm) and a significant decrease in quantum yield (φf=0.005, 0.023, and 0.20 for Ar=2,6-Me2-C6H3 (13), 2,6-iPr 2-C6H3 (14), and C6F5 (21), respectively, in THF), even when electron-withdrawing groups are also present. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have indicated that the excited singlet state has a planar aryliminopyrrolyl ligand, except when prevented by steric hindrance (ortho substituents). Calculated absorption maxima reproduce the experimental values, but the error is higher for the emission wavelengths. Organic light-emitting diodes (OLEDs) have been fabricated with the new boron complexes, with luminances of the order of 3000-cdm-2 being achieved for a green-emitting device. Fluorescent N,N-boron chelate complexes: Mononuclear boron complexes of 2-(N-arylimino)pyrrolyl emit violet to bluish-green colors in solution (see figure, ITO=indium tin oxide, PEDOT:PSS=poly(3,4- ethylenedioxythiophene):poly(styrene sulfonic acid)), depending on the substituents on the N-aryl group. Organic light-emitting diodes have been successfully fabricated with the new boron complexes, achieving luminances of the order of 3000-cdm-2.
