CAREER: Synthetic Strategies to Optimize Luminescence and Photoredox Properties of Organometallic Complexes

University Of Houston, Houston TX

Investigators

Abstract

In this CAREER project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Thomas S. Teets of the Department of Chemistry at the University of Houston is designing new synthetic strategies to prepare luminescent and photoactive iridium complexes. The first aim of the research develops compounds that emit blue light and may function in long-lived, high-efficiency organic light-emitting diode (LED) color displays. The second aim develops compounds that emit in the near infrared (NIR) region of the spectrum. Such compounds may be useful for biological sensing and imaging. The third aim targets compounds for photocatalysts in organic synthesis, which is important for the development of new pharmaceuticals. These research directions are complemented by an education and outreach component that aims to improve general chemistry instruction, introduce K-12 students to concepts of photochemistry, and to engage the general public in scientific learning. Professor Teets is creating an online, freely available multimedia general chemistry textbook to benefit low-income students. He also develops a K-12 lab module titled "Lighting Up Molecules" that introduces young students to the interactions of light with chemical compounds. Finally, he produces a public lecture series called "The Chemistry of Color" to introduce art enthusiasts to the chemical principles behind the creation of colors in visual art. In this project, Professor Teets studies a new class of blue phosphorescent cyclometalated iridium complexes supported by acyclic diaminocarbene and other unconventional carbene ligands. These carbene moieties destabilize interfering ligand-field states and thereby improve the quantum yield and stability of these blue-emitting compounds. In the opposite extreme of the spectrum, NIR-emitting bis-cyclometalated iridium complexes supported by electron-rich, pi-donating ancillary ligands are prepared. The electron-rich ancillary ligand destabilizes the iridium-centered Highest Occupied Molecular Orbital (HOMO), which increases the excited-state metal-to-ligand charge-transfer (MLCT) character, augments radiative rates, and improves photoluminescence quantum yield. Using similar design elements, potent visible-light photoreductants are developed. These cyclometalated iridium compounds have very reducing excited states and function as photocatalysts for organic transformations that involve photoactivation of strong substrate bonds. 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.