ANR WSPLIT (2018-2021)
Project coordinator: Mario Barbatti
Consortium: Gilles Grégoire (Université Paris Sud), Christophe Jouvet (AMU)
Funding: 306.000 €
Photoinduced water splitting is the ultimate source of storable and clean energy in the form of H2. For over four decades, to optimize this process has been the grail of sustainable energy research.
The possibility of splitting water through photoinduced radical reactions enabled by a simple organic chromophore is a recent theoretical prediction, which already counts on preliminary experimental corroboration. These reactions, however, are not the ones commonly expected in water splitting processes, as they involve hydrogen radicals rather than protons. For this reason, they may represent a deep paradigm shift in the H2 photocatalysis from water, if a series of bottlenecks in terms of recombination rates can be eliminated.
At this point, not much is known about these radical reactions. The WSplit project has been set up exactly to apply state-of-the-art experimental and computational techniques to close this knowledge gap. The project joins the expertise of three research terms, two experimental and one computational, to disentangle the reactive process through a combination of a large battery of techniques, including theoretical simulations, time-resolved experiments, and laser spectroscopy coupled to mass spectrometry. This analysis will be applied to isolated microsolvated clusters. The goals of the project are:
- To develop and use advanced experimental and computational methods to characterize the radical dynamics in microsolvated pyridine-water clusters.
- To use this basic knowledge to search for ways to reduce the recombination rate in these photoreactions.
- To test the efficiency of this class of radical reactions when photoinduced by other organic chromophores.
ANR-JCJC BIOMAGNET (2017-2021):
On the quest of a biological compass: Magnetic field effects on the cryptochrome protein
Abstract: Certain migratory animals orient during their long-distance migrations by perceiving the terrestrial magnetic field. The exact molecular origin of such sense is still unknown. Recently, the cryptochrome protein has been proposed as responsible of such “biological compass”. The photochemical mechanism would be based on the radical pair creation in donor-acceptor complexes: after light absorption, an electron transfer occurs between one flavin and the tryptophans forming the active site of cryptochrome, generating in this way a localized radical pair. Such radical pair would undergo a coherent dynamics of populations of singlet and triplet excited states. Theoretical models have shown that such dynamics can be affected by low-intensity external magnetic fields, supposing that the excited states have specific magnetic and dynamical properties: long-lived radical pairs, different singlet and triplet reactivity, anisotropic hyperfine coupling, etc. To this point, there is no proof that such a mechanism can exist in a biological medium. We propose to develop a multi-scale quantum dynamical model with the objective of determining the effect of magnetic fields to the activity of the cryptochrome protein. This model is based on analytic effectiveHamiltonians, which contain the information of magnetic, electronic and vibrational properties of the excited states of the protein. Such Hamiltonians will be used subsequently to propagate wavepackets in real time under the action of external magnetic fields. The project will give a first proof of whether the cryptochrome protein can be considered as a biological compass. Furthermore, the results can constitute the first direct proof of the effect of a low-intensity magnetic field on the mechanism of a photochemical reaction taking place in a biological medium.
ANR-PRC BIOLUM (2017-2020):
Molecular Origin and Modulation of the Color in Firefly Bioluminescence
Abstract: Vision and other light-based signaling processes are ubiquitous in Nature. Among all the molecular mechanisms responsible for light emission (eg fluorescence, phosphorescence …), chemiluminescence and its corresponding process in living organisms, bioluminescence, are interesting because of their molecular origin: chemical energy converted to light. It is noteworthy that the emitted light is a signature of the underlying chemical reaction. Hence bioluminescence has inspired the development of many analytical toolboxes in biomedical applications (eg imaging) using analogues of typical light emitters (fireflies, beetles, jellyfishes, …) Because these analogues exhibit photochemical properties similar to their natural counterparts (luminophores), they usually emit blue and green colors, i.e. synthetic yellow or red light emitters remain scarce. The design of bio-inspired light emitters requires a deeper understanding of the factors responsible at the molecular level for the tuning of the emitted color. As exemplified by the design of Green Fluorescent Protein (GFP, 2008 Nobel Prize in Chemistry)-like systems with optimum photophysical properties, it is of paramount importance to deeply understand the interactions between the light-active species and their protein binding pocket. Similar achievement is needed for the development of bioluminescence-based highly sensitive analytical techniques in environmental, medical, food analysis to cite just a few. The BIOLUM project aims to combine state-of-the-art theoretical and experimental fundamental researches to assess the effect of two major color tuning factors: 1) the luminophore + protein structures and interactions, 2) pH. Crossing the informations accumulated for both native and modified luciferin luminophores in the paradigmatic firefly luciferase enzyme, we envision an improved picture of the mechanisms at work in color modulation, with focus on 1) structures of native and modified luciferins in the luciferase binding pocket, 2) relevant photochemical steps in light emission, 3) key proton transfers between oxyluciferin (denoting the very last luciferin structure before light emission) and various donors and acceptors and 4) amino acids of the protein binding pocket that are crucial to control light emission color. Finally, the gained knowledge will help to suggest new directions for the rational design of man-taylored chemi- and bio-luminescent systems with selected colors.
ANR-DFG FEMTO-ASR (2015-2019):
Project coordinator: S. Haacke, IPCMS (Strasbourg)
Consortium: V. Ledentu, N. Ferré (AMU), IPCMS (Strasbourg), Univ Heidelberg (Germany)
Funding: 185.432 €
Anabaena Sensory Rhodopsin: A biological model system to decipher the quantum mechanics of photochemical reactions through conical intersections
The ultrafast photo-induced isomerization of retinal, present in its Schiff base form in photoactive proteins (rhodopsins), is among the most important photo-reactions in Nature as it enables higher and lower living organisms to transform photons into chemical energy. In spite of a sustained and intensive research, only a partial understanding of the reaction mechanism and the role of the protein environment to it are available. One of the major open puzzles is the dramatic differences in the efficiency and time constants of the reaction observed for visual and microbial retinal proteins. In this project, we will investigate the retinal’s photophysics and -chemistry in Anabaena Sensory Rhodopsin (ASR) by exploiting new ultrafast coherent non-linear spectroscopy combined with quantum mechanical calculations. ASR offers the ideal experimental and theoretical test ground to clarify this puzzle, since it is possible to compare the photodynamics of two biologically active retinal configurations, cis and trans, within the same protein surroundings. We will focus on a combined experimental and theoretical investigation of the interplay between electronic and vibrational dynamics along the photoreaction. To that end, we will develop and apply state-of-the- art ultrafast spectroscopies based on time-resolved Vibrational Coherence Spectroscopy and 2D Electronic Spectroscopy. Since these methods are highly sensitive to different molecular degrees of freedom, they will allow a complete mapping of the evolution of populations and coherences (electronic and vibrational) during the non-adiabatic photoisomerization of ASR. Quantum chemical simulations based on innovative excited state trajectory computations will be developed and applied to quantitatively understand the molecular reaction, including the identification of the vibrational modes contributing to the reaction coordinate and the mechanisms that control the reaction yields.
Chair of Excellence A*MIDEX (2015-2019)
Project coordinator: Mario Barbatti
Funding: 730.000 €
Computational Simulations of Organic Materials with Optical Activity: Method developments for effective experiment-theory integration
Motivated by the advances in computational capabilities and algorithms, computational research on dynamics simulations of electronically-excited molecular systems have been quickly developing in the last decade. The progress of this field faces, however, different challenges, including the development of new and more general functionalities, better integration with experimental analysis, and reduction of the computational costs. The COMOA project (for Computations of Organic Materials with Optical Activity), tailored for a two-years execution, intends to address many aspects of these challenges. It aims at 1) the development of new computational tools for excited-state simulations; 2) the integration of simulation tools into experimental analysis; and 3) the high-level investigations of photoactivated processes in organic materials. Specifically, the methodological developments in the COMOA project are grouped in four points: 1) transition couplings for linear-response methods; 2) new algorithms for surface hopping dynamics; 3) new algorithms for spectrum simulations; 4) new research protocols for dynamics. Together with the Newton-X program (www.newtonx.org), which I have been developing in the last years, these developments will lay the foundations for theoretical investigations of photopolymerization and photoinduced charge/energy transport in organic polymers. The COMOA project focus on a critical area, the investigation of organic materials with optical activity, in agreement with the aim of excellence of the Fondation Universitaire A*MIDEX. It is designed to be executed in the Institut de Chimie Radicalaire of the Aix-Marseille Université having myself, Mario Barbatti, as principal investigator, working in close collaboration with other members of the Institute, especially professors Nicolas Ferré and Didier Gigmes. From an institutional standpoint, the project aims at 1) strengthening the Theoretical Chemistry group and 2) reinforcing the experimental-theoretical collaborations in Marseille.
Project coordinator: Emmanuel Beyou, IMP (Lyon)
Funding: 669.900 €
High temperature chemical modification of polycondensates in presence of aminyl-based radicals
In the last decades, great interest has been devoted to the field of polymer chemical modification in the absence of solvent thus reducing or eliminating the emission of Volatile Organic Compounds. From this point of view, one way is to work in the polymer melt state allowing the production of materials with new chemical and physical characteristics. Most of the earlier works were carried out by using an economic route via free radical-initiated processes. The free radical addition of monomers such as maleic anhydride and vinyltrialkoxysilanes to saturated polymer chains yields functional derivatives that are valued for blend compatibilization and filler reinforcement applications. To reach this goal, one must be able to abstract hydrogen onto the polymer backbone at high temperature (T>160°C to reach convenient viscosity of the polymer under shearing) while creating radical sites on the polymer backbone that may initiate the graft copolymerization of a second monomer. For example, current methods of chemical modification of polyolefins are based on the use of conventional-type reactive radical polymerization initiators (usually peroxides). The extension of radical functionalization to polycondensates-based polymers such as polyamides, polyesters is a great challenge and could represent an innovative tool to modify their macromolecular structure inducing new properties. Conventional reagents such as peroxide molecules initiate monomer polymerization and produce either carbon or oxygen-centered free radical species that are well known for their H-abstraction ability. Nevertheless, low functionalization (i. e. grafting ratio), cross-linking, homopolymerization as well as degradative pathways are observed in the radical modification of polycondensates using peroxides in presence of monomer.
Recently, a new family of radical initiators based on the N-acetoxyphtalimide (NAPI) was developed. These compounds are supposed to produce acyl and α , α’-dione-cycloaminylradicals upon heating at high temperature (T > 190 °C) and the latter species are claimed to be a good alternative to peroxides molecules. In particular, we have shown that NAPI was a better hydrogen abstractor than di-cumyl-peroxide in presence of polyolefins at 200°C. Several inherent disadvantages of the peroxide process such as discoloration, odor or smoke are eliminated or considerably reduced by using such H-abstractors combining the advantages of high grafting yield and low degradation in the extrusion grafting process. Herein, the main purpose of this project is to understand how the substitution of peroxide based molecules by new hydrogen abstractor molecules could ensure the melt functionalization of polycondensates by a radical grafting way while minimizing the occurrence of side reactions. The production of highly reactive ,’-dione-cycloaminyl radicals should remove the technological barrier that impedes the industrial synthesis of new grafted copolymers based on polycondensates grafted with vinylic and (meth)acrylic polymers. The ultimate objective is to improve the dimensional stability and thermal properties of polycondensates-based blends by controlling the effect of the grafted copolymer on the morphology and crystallinity of the blends. By an appropriate choice of the molecular parameters of the functionalized polymer, it will be possible to obtain nanostructured micellar or co-continuous morphologies having high potential applications if enough graft copolymer chains are formed.