Oxygen-Bridged Triphenylamine Units Tuning The Photophysical Properties Of Classical Phosphorescent Iridium(Iii) Complex

A new yellow phosphorescent iridium(III) complex Ir(ppybop)(2)acac with two oxygen-bridged triphenylamine units were prepared and investigated. The cyclometalating ligand ppybop was synthesized by the efficient Suzuki-Miyaura cross-coupling reaction of oxygen-bridged triarylamine unit based boron reagent 1-a and 2-(4-Bromophenyl)pyridine, and the acetylacetone (acac) was used as an auxiliary ligand. Notably, the complex Ir(ppybop)(2)acac measured with a fluorescence spectrophotometer can show a larger redshift emission (lambda(em)=568 nm), a narrower full width at half maximum (FWHM=59 nm), a longer emission lifetime (tau([b])=3127 ns) and a better solubility in comparison with the classical green complex Ir(ppy)(2)acac (lambda(em)=520 nm, FWHM=70 nm, tau([b])=1206 ns). In addition, the DFT calculation results indicate that the strong electron-donating ability of the unit can lead to the unusual ligand-to-metal charge transfer ((LMCT)-L-3) excited state characteristics of Ir(ppybop)(2)acac, which is completely different from the metal-to-ligand charge transfer ((MLCT)-M-3) in Ir(ppy)(2)acac. This result can provide a new strategy for the design of new phosphorescent iridium(III) complexes.