Luminescent Organometallic Complexes with Fast Radiative Rates

University Of Houston, Houston TX

Investigators

Abstract

WIth support from the Chemical Structure, Dynamics & Mechanisms-B (CSDM-B) Program of the Chemistry Division, Thomas Teets of the Department of Chemistry at University of Houston is investigating strategies to increase the radiative decay rates in phosphorescent metal complexes. Phosphorescent metal complexes have been used in a variety of optoelectronic applications, most notably organic light-emitting diodes (OLEDs), a lighting technology that is widely used in color displays and other consumer products. The goal of this project is to use complementary molecular design strategies in a few different classes of phosphorescent compounds to increase their radiative rates, with long-term implications of producing OLEDs with improved efficiency and durability. The work combines innovative synthetic chemistry to make new molecules and in-depth photophysical characterization to measure the color profile, efficiency, and timescale of light emission. Standing at the interface of organometallic chemistry and photochemistry, this research aims to produce insightful structure-property relationships that lead to the discovery of top-performing phosphorescent metal complexes. Another part of this project will develop a publicly available web database of photochemically active compounds, allowing researchers at all levels to search and sort the database for compounds that have specific properties of interest. Finally, this research project will serve as a training ground for undergraduate and graduate researchers in experimental physical inorganic chemistry research to contribute to the future science and technology workforce. Under this award, the Tests research team will pursues three complementary strategies for increasing the radiative rates and photoluminescence quantum yields of organometallic phosphors. The first two focus on blue phosphorescence, which remains one of the most significant technical challenges in the optoelectronic field. Platinum acetylide compounds are a promising class of blue-phosphorescent compounds, but their slow radiative rates have hindered their widespread deployment in OLEDs. This project will introduce the “secondary heavy-metal effect” as a strategy to increase radiative rates, by decorating the periphery of platinum aryl acetylide compounds with other heavy metals. These approaches center on pyridyl-substituted acetylides which can coordinate to a variety of heavy metal additives, binding of coinage metals directly to the acetylide π-electrons, and covalent gold-carbon bond formation on the aryl acetylide ligands. Although organoplatinum complexes are the major focus of this work, a second strategy for blue phosphorescence with fast radiative rates will involve a new class of cyclometalated iridium acetylide compounds. These compounds will combine the advantageous sharp blue phosphorescence originating from aryl acetylides with the inherently larger spin-orbit coupling and faster radiative rates that iridium engenders. Finally, the last major thrust of this project centers on cyclometalated platinum complexes, with an emphasis on luminescence in the lower-energy regions (red to near-infrared) of the spectrum. These compounds will feature electron-rich ancillary ligands that can stabilize charge-transfer states, increase excited-state spin-orbit coupling, and augment radiative rate constants. Steric effects on both the cyclometalating and ancillary ligand will also be investigated and are important for minimizing aggregation and suppressing nonradiative rates. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.