Computational study of on-surface catalysis induced by ligh

Project Information

PhotoSurf

Grant agreement ID: 101065707

DOI

10.3030/101065707

Project closed

EC signature date 8 August 2022

Start date 1 September 2023

End date 31 August 2025

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 165 312,96

Coordinated by

AGENCIA ESTATAL CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS
Spain

Periodic Reporting for period 1 - PhotoSurf (Computational study of on-surface catalysis induced by ligh)

Reporting period: 2023-09-01 to 2025-08-31

Summary of the context and overall objectives of the project

The main hypothesis behind this proposal is that only an adequate combination of experiments with theory can result in a description of fundamental processes leading to innovating technology. This is particularly true for interdisciplinary research, and in particular for new disciplines positioned at the cutting edge of knowledge. Photochemistry on-surfaces is a new field evolved from on-surface synthesis that combines the knowledge acquired by organic chemistry in light-mediated reactions with the world of surface-catalysis and low dimensional materials. The objective of this fellowship will be to develop computational tools and protocols for rationalizing these processes.

Objectives

Objective 1: molecular self-assembly. In on-surface photocatalysis the role of the self-assembly of the molecules play a crucial role. Self-assembly of the molecules is driven by two main interactions: molecule-molecule and surface-molecule interactions. To study this, we propose to do a screening of different molecular substituent terminal groups, with a classical Molecular Mechanics approach and a final QM/MM relaxation. We will also create a python package with all the workflow in an intuitive way and easy to use.

Objective 2: molecular light absorption on surfaces. Another objective will be the study of light absorption of these molecules on the surface. It is known that the addition of substituent can have an impact in the wavelength absorption. It is also known that the self-assembly of the molecules can play a role in the wavelength absorption spectrum. In these work packages we will use the most promising molecules found in the self-assembly. From this part we want to clarify the wavelength at which we have to illuminate the molecules to promote the reaction and increase the quantum yield.

Objective 3: molecular coupling induced by light. Another important point is understanding the mechanism of light-induced reaction on a surface. Several computational studies of photochemical reactions have been done in the gas phase or liquid environment. However, the role of the different surfaces in these reactions is not clear. We propose to study this reaction in different ways to clarify the role of the surface. We want to see the role of the surface in potential energy and also with out of equilibrium dynamics such as Non-Adiabatic Molecular Dynamics (NAMD) with electronics transitions.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Computational self-assembly study:

We have tried different computational techniques to be able to characterize the self-assembly of molecules on different surfaces. With this knowledge we were able to see which force field worked better for different surfaces (insulators and metals), molecules and the interaction between them. We also realized that there is a needed of a more refined calculation to have a god resolution for the calculation of optical properties. The results of the computational proposed self-assemblies have been compared with the experiments. With this information we developed a workflow that can be used to predict molecular self-assemblies.

Study of absorption spectra of molecules on surface:

We have characterized the optical response of several molecules on surfaces. We observed that TD-DFT technique gives good result for all the organic molecules we tested. We also realized that for insulated a semiconductor surface the use of QM/MM with the molecule in the QM region and the surface in MM region improve the description of the electronic levels. For metal surfaces the charge transfer between this molecules and surface was not possible to be considered and the simulations for the electronic levels has been realized in the gas phase. This studies have been done with 4,4’,4’’-benzene-1,3,5-triyltricinnamate molecule (TBTT)

On-surface photoreactions:

We have studied the photo reactions pathway of molecules that can have a 2+2 reaction. The results show that the 2+2 reactions need a specific orientation between the carbons of the double bond to be effective in a self-assembly of TBTT molecules. We also see that we need and insulator surface to be able to have the reaction. We observed than in mica surface the reaction was possible with two layers of TBTT molecules. With only one layer the self -assembly of this molecule cannot create the 2+2 reaction. We also observe than in metallic surfaces and semiconductor surface light can help to induce the braking of the molecule through a different process that we believe is a surface induced plasmon.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The main results of this fellowship has been understanding the key factors to be able to create homogenous 1D and 2D networks with photochemical reactions of molecules on surfaces. Also to create these networks on insulator surfaces to have a more green chemistry. This work has been performed computationally by the researcher and in a close collaboration with experimental researchers.

To be able to create homogenous networks we realized that we need to have an initial self-assembly that can promote photo reactions of molecules on surface without big movements of the molecule. To understand self-assembly of molecules at different surfaces we create a computational protocol that will allow us to find the most stable assembly, lowest energy, using classical molecular mechanics and multiscale simulation with Quantum mechanics / Molecular mechanics (QM/MM).

We have focus our interest in creating networks in the creation of a 2D network of 4,4’,4’’-benzene-1,3,5-triyltricinnamate molecules (TBTT) . These molecules have three arms that can perform a 2+2 reaction and can bond between them after light absorption through a 2+2 reaction. We studied computationally the self-assembly of these molecules on three different surfaces: Au111 surface (metallic), SnSe surface (semiconductor) and mica (insulator). We observed computationally and experimentally that the 2+2 photo reaction can only happen on a mica surface with a double layer of molecules. From the computational results we observed that the 2 layers of molecules allow the right geometry to create a thin layer of covalent bond network through a 2+2 reaction. In the case of Au surface and SnSe surface what we observe is that light absorption is not able to create a 2+2 reaction however in combination with small annealing light can promote a breaking in the molecule and a subsequent reaction creating an inhomogeneous network.

We believe that these results will push forward more research in photoreactions of molecule on surface with the goal to create new materials and molecular networks with a green chemistry.