Supramolecular Design Strategies for Color Tuning of Iridium(III) Complexes Using a Common Framework of Cyclometalating Ligands

Abstract

Organic light emitters have shown potential for the application in a variety of optoelectronic devices. However, the quenching of luminescence in the solid state severely restricts the lighting applications. The rational supramolecular design strategy of the luminescent organic emitters in solid state remains challenging. Here, supramolecular assemblies of a series of iridium(III) complexes are designed on a water surface to realize solid state tunable luminescence in the visible region. Large area two-dimensional supramolecular platelets and disks, yet with monomolecular thickness, are formed depending on the cyclometalating ligands. Controlled supramolecular aggregates of iridium(III) complexes enhances the aggregation-induced-emission phenomenon by restricting monodentate triphenylphosphine and cyclometalating ligands at the water surface. As a consequence, a large enhancement of luminescence comparable to the solid powder is obtained from the supramolecular assemblies of iridium(III) complexes. Supramolecular assemblies display fine-tuning of the luminescence color from green to red in solid state depending on the cyclometalating ligand. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) reveal phosphorescence origin of the luminescence. These findings emphasize the importance of controlled organization of organic emitters to explore optimal luminescence properties for efficient lighting applications.