Comprehension of Photocatalytic Processes

Over the past few years, visible-light-mediated photoredox catalysis has emerged as a powerful reaction platform for chemical synthesis.[1] In these processes, the photoredox catalyst absorbs light and promotes an electron from a lower-energy orbital to a higher-energy one, typically from the highest occupied molecular orbital to the lowest unoccupied molecular orbital (a HOMO → LUMO transition). The excited electron can be readily abstracted, while the resulting low-lying vacancy can be filled by an external electron. As a consequence, excited photoredox catalysts can function as both strong oxidants and strong reductants.

Upon irradiation with light of an appropriate wavelength, these catalysts can also enable the photoactivation of electron donor–acceptor (EDA) complexes.[2] In such systems, noncovalent interactions—particularly π–π interactions—play a crucial role. Significant electronic redistribution occurs upon EDA complex formation relative to the isolated components, as well as during the excitation process. These effects often manifest as non-negligible redshifts in the UV–Vis spectra and substantial changes in electronic properties, e.g. aromaticity. Temperature may also play a relevant role in modulating these phenomena.

During this internship, the candidate will learn how to investigate photoinduced radical-mediated organic reactions from a computational perspective, with special emphasis on EDA complexes. This will include the study of UV–Vis spectra and aromaticity in both the ground state and the lowest excited singlet and triplet states, within a density functional theory (DFT) framework.

The ideal candidate should have a basic background in quantum chemistry (typically acquired in undergraduate programs in chemistry or physics) and a strong motivation to learn the fundamentals of electronic structure theory and DFT.

[1] a) Prier, C. K.; Rankic, D. A.; MacMillan, D. W. C. Chem. Rev. 2013, 113, 5322; b) Shaw, M. H.; Twilton, J.; MacMillan, D. W. C. J. Org. Chem. 2016, 81, 6898; c) Twilton, J.; Le, C. C.; Zhang, P.; Shaw, M. H.; Evans, R. W.; MacMillan, D. W.C. Nat. Rev. Chem. 2017, 1, 0052.
[2] a) Foster, R. J. Phys. Chem. 1980, 84, 2135; b) Crisenza, G. E. M.; Mazzarella, D.; Melchiorre, P. J. Am. Chem. Soc. 2020, 142, 12, 5461–5476.