Computational study of a photochemical reaction between an electron donor and an electron acceptor through π–π interactions.

Identifier:  TFG:9348

Handle: https://hdl.handle.net/20.500.11797/TFG9348

Authors:  Suriol Vadrí, Albert

Abstract:
This work presents a computational study of the initial steps of a photocatalytic reaction involving an electron donor and an acceptor. The model system is based on the formation of an elec- tron donor–acceptor (EDA) complex between 3-methylindole (IND) and 2,4-dinitrobenzyl bromide (BNO). Molecular dynamics simulations were carried out in polar solvents (methanol and ethanol), and complementary DFT and TD-DFT calculations were performed to analyze the formation of the EDA complex, its electronic absorption spectra, the nature of the involved frontier orbitals, and the energetic feasibility of the photoinduced electron transfer process. The results show that π−π interactions between IND and BNO do not persist spontaneously in solution, but once the complex is formed, its excitation leads to a favorable HOMO→LUMO transition consistent with a single electron transfer (SET) mechanism. Energetic analysis confirms that the complex is more stable when formed in the ground state than after photoexcitation of the individual species. Finally, a study of the C–Br bond dissociation highlights how electronic substituents modulate the antibonding character of the LUMO and promote Br departure. These findings support the proposed reaction mechanism and demonstrate the usefulness of computational methods for investigating photochemical processes.