Quantum chemical investigation of excited state of lignin units
Title: Quantum chemical investigation of excited state of lignin units
DNr: NAISS 2024/22-79
Project Type: NAISS Small Compute
Principal Investigator: Leandro Cid Gomes <leandroc@chalmers.se>
Affiliation: Chalmers tekniska högskola
Duration: 2024-01-26 – 2025-02-01
Classification: 10405


The project focus is to investigate the excited state of lignin monomers (p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol) and other units present in the lignin structure, such as cinnamyl alcohol, coumarates and quinones. It is expected that this study will be useful to explain experimental observations made when lignin is irradiated with UV/visible light. Ultimately, we seek to use UV/visible light to assist on the depolymerization of lignin, affording building blocks of a sustainable source to be used in other synthetic routes. Despite being vastly available as an aromatic biopolymer, lignin has a heterogeneous chemical structure which depends on its source and the method used for its extraction. Therefore, what is called "lignin" can vary to a large extent in terms of chemical groups. When irradiated under UV and visible light, lignin undergo chemical changes that involves hydrogen atom transfers, bond cleavage and repolymerization. Considering the variety of chemical groups and their inherent excited state differences, we plan to use (TD)DFT methods to assess these differences and use the information to predict or explain the photochemical changes in lignin. Underlying pathways might involve an excited state H-atom transfer from the Aryl-OH groups. In that regard, the investigation of the different Aryl-OH groups in lignin as photoacids and information on their pKa in the excited state will likely be part of this project, which overlaps with the topics of the previous project for which this one is presented as continuation.