Instability of Iridium (III) Photocatalysts: A Computational Approach, André Luiz Koch Liston, UG' 23 (2185987)

Organometallic complexes are chemical compounds composed of heavy metal ions combined with organic molecules (ligands). They have a broad range of applications in chemistry, from catalysts in drug synthesis to organic LEDs in microelectronics. Of these, Iridium III complexes have a wide-spread industrial use, because they are generally stable and can activate other catalysts in a reaction by absorbing and emitting light. However, in polar solvents like water or tetrahydrofuran, the complex (Ir[dF(CF3)ppy]2(dtbpy))+ has been reported to decompose. To investigate this instability, we used Gaussian 16 (a quantum chemistry simulation software) to theoretically model the compound and predict its behavior. First, we simulated possible reaction products that fit the experimental observations (FNMR spectra). That indicated that the CF3 groups (part of the ppy ligands) could be replaced during the reaction. Then, we computed the bond dissociation energies for the carbon-carbon bond, C-CF3, under various conditions. This showed that when the compound received an extra electron (entering its reduced state) the carbon-carbon bond was weakened. With this, we proposed a reasonable process for the compound’s decomposition: after absorbing a photon of light, the Ir complex becomes excited, allowing it to capture an electron from another metal catalyst (usually Nickel)—which fragilizes certain bonds leading to the formation of byproducts. Moving forward, I intend to determine the dynamic details of this photocatalyst as it undergoes energy transitions. This would grant insight into how composition may be intentionally altered to optimize energy emission in reactions or organic LEDs.