SCIIPT · Shaping Conical Intersections for Intramolecular Proton Transfer
FP7 — People (Marie Curie Actions)
- Duration
- 2010-09-20 → 2012-09-19
- EU contribution
- €172,741
- Participants
- 1
- Scheme
- MC-IEF
Lines connect the coordinator with its partners.
Results in brief
Shaping Conical Intersections for Intramolecular Proton Transfer
Project context and objectives The objective of the project was to analyse the role of conical intersection (CI) seams in photochemical processes. As we have already highlighted in the mid-term report, we decided to postpone the study of intramolecular proton transfer because it is now known that there are three states involved in the mechanism (and hence a three-state conical intersection). Instead, we decided to focus on a problem in which there are just two states involved, but multiple coordinates, to test and experiment with a new code developed by our group to analyse conical intersection seams at the second order (F. Sicilia et al., J Chem Theory Comput., 2008, 4, 257). Such a problem is, indeed, very important in industry for chemical synthesis: photocycloadditions, specifically ethene+ethene and benzene+ethene, and to investigate substituent effects. Project tasks During the project, first we have analysed the ethene+ethane model system as a benchmark and for training on how to use the new code (now published in J.J. Serrano-Perez, DOI: 10.1080/00268976.2012.698757).In addition, the use of valence-bond (VB) theory helped us to understand the origin of the crossing seam that promotes decay of the excited state in this system. This knowledge proved invaluable for addressing the more complex benzene+ethene system, in which not only the seam proved to be important, but also the connections among multiple structures in both the excited and ground states. Specifically, we were forced to use non-standard techniques in order to obtain a picture of the photochemical panorama of this transformation (paper accepted by J. Org. Chem.) and to understand the origin of the products obtained experimentally. Finally, a study on the photocycloaddition of benzene with substituted alkenes is ongoing. Project results and outcomes These photochemical studies have enlightened the role of CI seams in photochemical mechanisms. Interaction of light with tissues or, in general, living or non-living entities, is a complex phenomenon which lies on the borders of physics, chemistry and biology and leads to many developments: understanding the effects of electromagnetic radiation on living tissues (DNA alteration, phototherapy, etc.), designing light-harvesting systems for clean and sustainable energy generation, photocatalysis and the design of efficient light-driven molecular devices for data storage and processing, and photoactive materials with particular chemical, biological, energy or information storage properties. Analysing spectroscopic phenomena at the molecular level provides information that may well be the source of interesting advances in the future. By learning how to design molecules that interact with light predictably, work of this type provides essential knowledge for the development of chemical engineering, nanotechnology, materials science and/or photobiology. Following the grant application, the fellow has been involved in additional research projects, teaching duties, courses to develop the skills needed to become a senior researcher in the future, and supervision of visiting students.
Data: CORDIS, © European Union
Project objective
Excited-state intramolecular proton transfer (ESIPT) - where proton transfer occurs after the absorption of a photon - is an important topic for the understanding of photoreactions in organic systems. The central aim of this proposal is to apply a unique combination of novel computational tools to understand such processes. We will study methyl salicylate (MS), a ‘floppy’ molecule with a slow proton transfer. Computationally, our first objective will be to map out the reaction paths and conical intersection seams accessible to excited states, characterised as critical points linked by minimum energy paths that preserve the degeneracy of the two states. Having determined the molecular geometries at which decay to S0 takes place, we will be able to suggest strategies to control the dynamics on the excited state. Multiple decay pathways make MS and related systems suitable for coherent control investigations; experiments which are planned by the experimental group of Prof. Fielding at University College London. MS is a challenge for quantum methods in which the dynamic electron correlation is cruzial for obtaining accurate excitation energies and realistic barrier heights. Our second objective is to compare the CASPT2 approach - which the applicant knows from his PhD- with the RASSCF one. Calculating CASPT2 energies at CASSCF geometries is a state-dependent approximation: there is the potential with RASSCF to go beyond this. There is scope to develop the projects further including environmental effects (QM/MM), or to study quantum dynamics. This fellowship proposal combines the experience of excited state calculations developed by the applicant with the complementary experience in computational methods of the host group. It will lead to new insights into the mechanism of ESIPT and greater experience in crossing seam mapping. Furthermore, there is scope for developing long-term collaborations between both computational & experimental groups in the UK & Spain.
Original text from CORDIS.
Participants
- IMPERIAL COLLEGE OF SCIENCE TECHNOLOGY AND MEDICINE · LondonCoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union