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.

Automated summary

The new yellow phosphorescent iridium(III) complex Ir(ppybop)(2)acac showed improved emission characteristics and solubility compared to the classical green complex Ir(ppy)(2)acac. The strong electron-donating ability of the unit led to unusual ligand-to-metal charge transfer excited state characteristics, providing a new strategy for designing phosphorescent iridium(III) complexes.