Photo-absorption et diffusion Raman dans des complexes de dihalogènes avec l'eau : relation avec des expériences dans l'eau liquide, la glace et les clathrates

Cette thèse présente la simulation des spectres de photo-absorption et de diffusion Raman de complexes formés d'une molécule de dihalogène (Cl2, Br2) avec une molécule d'eau, dans le cadre d'un modèle à 2 dimensions des complexes qui tenait compte des deux coordonnées dissociatives dans les états excités: distance inter-halogènes et distance intermoléculaire. La simulation par propagation de paquets d'ondes a été effectuée à partir de surfaces de potentiel des états fondamentaux et premiers états excités de valence (B et C) ab initio avec inclusion du couplage spin-orbite. Les résultats montrent une dissociation inter-halogènes très rapide, ce qui a permis de valider un modèle de molécule d'eau spectatrice qui ouvre des perspectives très intéressantes pour des simulations en phase d'eau condensée. De plus, ils permettent d'établir des comparaisons avec les résultats expérimentaux existants, notamment en phase d'eau condensée: clathrates, glace, liquide, et de donner des critères pour établir la présence ou non de ces complexes dans ce type d'environnements.This thesis presents the simulation of photoabsorption and Raman diffusion spectra of complexes built with a dihalogen (Cl2, Br2) molecule bound to a water molecule, within the framework of a two-dimension model of the complexes which included the two coordinates that are dissociative in the excited states: the interhalogen and the intermolecular distances. The wave packet propagation simulation was performed on ab initio potential energy surfaces for the ground and first valence excited (B and C) electronic states of the dihalogen with inclusion of the spin-orbit coupling. The results show a very fast inter-halogen dissociation, which validated a model where the water molecule acts as a spectator. This model opens very interesting perspectives for simulations in condensed water phases. In addition, they can be compared to existing experimental results, in particular in condensed water phases: clathrates, ice, liquid, and provide criteria to detect the presence or absence of these complexes in this type of environment

Electronic Energy Relaxation in a Photoexcited Fully Fused Edge-Sharing Carbon Nanobelt

Carbon nanobelts are cylindrical molecules composed of fully fused edge-sharing arene rings. Because of their aesthetically appealing structures, they acquire unusual optoelectronic properties that are potentially suitable for a range of applications in nanoelectronics and photonics. Nevertheless, the very limited success of their synthesis has led to their photophysical properties remaining largely unknown. Compared to that of carbon nanorings (arenes linked by single bonds), the strong structural rigidity of nanobelts prevents significant deformations away from the original high-symmetry conformation and, therefore, impacts their photophysical properties. Herein, we study the photoinduced dynamics of a successfully synthesized belt segment of (6,6)CNT (carbon nanotube). Modeling this process with nonadiabatic excited state molecular dynamics simulations uncovers the critical role played by the changes in excited state wave function localization on the different types of carbon atoms. This allows a detailed description of the excited state dynamics and spatial exciton evolution throughout the nanobelt scaffold. Our results provide detailed information about the excited state electronic properties and internal conversion rates that is potentially useful for designing nanobelts for nanoelectronic and photonic applications.Fil: Freixas Lemus, Victor Manuel. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Oldani, Andres Nicolas. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Franklin Mergarejo, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; ArgentinaFil: Tretiak, S.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Fernández Alberti, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentin

A theoretical simulation of the resonant Raman spectroscopy of the H2O⋯Cl2 and H2O⋯Br2 halogen-bonded complexes

The resonant Raman spectra of the H2O⋯Cl2 and H2O⋯Br2 halogen-bonded complexes have been studied in the framework of a 2-dimensional model previously used in the simulation of their UV-visible absorption spectra using time-dependent techniques. In addition to the vibrational progression along the dihalogen mode, a progression is observed along the intermolecular mode and its combination with the intramolecular one. The relative intensity of the inter to intramolecular vibrational progressions is about 15% for H2O⋯Cl2 and 33% for H2O⋯Br2. These results make resonant Raman spectra a potential tool for detecting the presence of halogen bonded complexes in condensed phase media such as clathrates and ice.Fil: Franklin Mergarejo, Ricardo. Université Paris Sud; Francia. Centre National de la Recherche Scientifique; Francia. InSTEC; Cuba. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rubayo Soneira, Jesús. InSTEC; CubaFil: Halberstadt, Nadine. Université Paris Sud; Francia. Centre National de la Recherche Scientifique; FranciaFil: Janda, Kenneth C.. University of California at Irvine; Estados UnidosFil: Apkarian, V. Ara. University of California at Irvine; Estados Unido

Photo-absorption et diffusion Raman dans des complexes de dihalogènes avec l'eau (relation avec des expériences dans l'eau liquide, la glace et les clathrates)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Phonon Bottleneck and Long-Lived Excited States in pi-Conjugated Pyrene Hoop

In the last decade, recent synthetic advances have launched carbon-based π-conjugated hoops to the forefront of theoretical and experimental nvestigation not only for their potential use as bottom-up templates for carbon nanotube (CNT) growth, but also for the interesting excitoniceffects arising from the cyclic geometry, unique pi-system orientation, and unusual electronic interactions and couplings. In particular, cyclic materials based on pyrene, a common component in organic electronics, are popular candidates for the future design of pi-conjugated nanorings foroptoelectronic applications. Understanding the photophysical response in cyclic oligopyrenes can be achieved using Non-Adiabatic Excited State molecular Dynamics (NA-ESMD). Through NA-ESMD modeling, we reveal details of the nonradiative relaxation processes in the circular pyrenetetramer [4]cyclo-2,7-pyrenylene ([4]CPY) where we find that the strong non-adiabatic coupling combined with the dense manifold of excited states creates an internal conversion mechanism dominated by ultrafast sequential quantum transitions. However, we observe two long-lived electronic excited states that introduce a phonon bottleneck in the electronic relaxation process. In fact, the timescale for the electronic relaxation is almost exclusively dominated by the lifetimes of the long-lived states. We find that the states associated with the phonon bottleneck are separatedfrom lower energy states by large energy gaps and are characterized by localization on a single pyrene unit resulting in a spatial mismatch with strongly delocalized neighboring states.Fil: Franklin Mergarejo, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Nelson, Tammie. Los Alamos National Laboratory; Estados UnidosFil: Tretiak, Sergei. Los Alamos National Laboratory; Estados UnidosFil: Fernández Alberti, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; Argentin

Phospholipids dock SARS-CoV-2 spike protein via hydrophobic interactions: a minimal in-silico study of lecithin nasal spray therapy

Understanding the physical and chemical properties of viral infections at molecular scales is a major challenge for the scientific community more so with the outbreak of global pandemics. There is currently a lot of effort being placed in identifying molecules that could act as putative drugs or blockers of viral molecules. In this work, we computationally explore the importance in antiviral activity of a less studied class of molecules, namely surfactants. We employ all-atoms molecular dynamics simulations to study the interaction between the receptor-binding domain of the SARS-CoV-2 spike protein and the phospholipid lecithin (POPC), in water. Our microsecond simulations show a preferential binding of lecithin to the receptor-binding motif of SARS-CoV-2 with binding free energies significantly larger than $$k_\mathrm{B}T$$. Furthermore, hydrophobic interactions involving lecithin non-polar tails dominate these binding events, which are also accompanied by dewetting of the receptor binding motif. Through an analysis of fluctuations in the radius of gyration of the receptor-binding domain, its contact maps with lecithin molecules, and distributions of water molecules near the binding region, we elucidate molecular interactions that may play an important role in interactions involving surfactant-type molecules and viruses. We discuss our minimal computational model in the context of lecithin-based liposomal nasal sprays as putative mitigating therapies for COVID-19

Emergence of Electric Fields at the Water-C12E6 Surfactant Interface

We study the properties of the interface of water and the surfactant hexaethylene glycol monododecyl ether (C12E6) with a combination of heterodyne-detected vibrational sum frequency generation (HD-VSFG), Kelvin-probe measurements, and molecular dynamics (MD) simulations. We observe that the addition of the hydrogen-bonding surfactant C12E6, close to the critical micelle concentration (CMC), induces a drastic enhancement in the hydrogen bond strength of the water molecules close to the interface, as well as a flip in their net orientation. The mutual orientation of the water and C12E6 molecules leads to the emergence of a broad (∼3 nm) interface with a large electric field of ∼1 V/nm, as evidenced by the Kelvin-probe measurements and MD simulations. Our findings may open the door for the design of novel electric-field-tuned catalytic and light-harvesting systems anchored at the water-surfactant-air interface.Fil: Gera, Rahul. Fom Institute For Atomic And Molecular Physics; Países Bajos. Dutch Research Council; Países BajosFil: Bakker, Huib J.. Fom Institute For Atomic And Molecular Physics; Países Bajos. Dutch Research Council; Países BajosFil: Franklin Mergarejo, Ricardo. The Abdus Salam. International Centre for Theoretical Physics; Italia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Morzan, Uriel. The Abdus Salam. International Centre for Theoretical Physics; Italia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Falciani, Gabriele. Politecnico di Torino; ItaliaFil: Bergamasco, Luca. Politecnico di Torino; ItaliaFil: Versluis, Jan. Fom Institute For Atomic And Molecular Physics; Países BajosFil: Sen, Indraneel. Uppsala Universitet; SueciaFil: Dante, Silvia. Istituto Italiano Di Tecnologia; ItaliaFil: Chiavazzo, Eliodoro. Politecnico di Torino; ItaliaFil: Hassanali, Ali A.. The Abdus Salam. International Centre for Theoretical Physics; Itali