Supramolecular Dendriphores: Anionic Organometallic Phosphors Embedded in Polycationic Dendritic Species

Abstract

Heteroleptic iridium(III) organometallic complexes have been functionalized with sulfate tethers. These systems have been thoroughly characterized spectroscopically. Subsequently these iridium(III) complexes were reacted with polyionic dendritic materials yielding iridium(III) organometallic phosphorescent emitters supramolecularly bound in dendritic materials. The synthesized supramolecular core−shell materials were characterized using a range of standard spectroscopic and spectrometric techniques. Furthermore, a thorough analysis of the photophysical properties (UV−vis absorption/emission, quantum yield, lifetime of emission) was carried out. The tethered sulfate complexes were found to have similar photophysical properties compared to their unfunctionalized analogues. It was found that immobilization of the iridium lumiphores within the core of the dendritic material resulted in quenching of the triplet emitting state. The quenching was found to be a consequence of intramolecular triplet−triplet annihilation resulting in quenching of the emissive state of the phosphorescent organometallics. It was shown by varying the dendrimer generation, and flexibility around the core, that we could alter the extent of triplet−triplet annihilation. It was also discovered that multiple phosphorescent sites existed in a single host−guest polyionic material. All host−guest materials demonstrated this property. Lifetime decay patterns were solved using biexponential statistics, suggesting more than one type of decay. The developed host−guest materials were applied as lumiphores in OLED devices, and showed that in the solid state the observed quenching is diminished