Papers by Corentin Poidevin
In this work, we present a quantum mechanics/ molecular mechanics (QM/MM) approach for the comput... more In this work, we present a quantum mechanics/ molecular mechanics (QM/MM) approach for the computation of solid-state nuclear magnetic resonance (SS-NMR) shielding constants (SCs) for molecular crystals. Besides applying standard-DFT functionals like GGAs (PBE), meta-GGAs (TPSS), and hybrids (B3LYP), we apply a double-hybrid (DSD-PBEP86) functional as well as MP2, using the domain-based local pair natural orbital (DLPNO) formalism, to calculate the NMR SCs of six amino acid crystals. All the electronic structure methods used exhibit good correlation of the NMR shieldings with respect to experimental chemical shifts for both 1 H and 13 C. We also find that local electronic structure is much more important than the long-range electrostatic effects for these systems, implying that cluster approaches using all-electron/Gaussian basis set methods might offer great potential for predictive computations of solid-state NMR parameters for organic solids.
Le premier chapitre de cette these concerne l'etude theorique des proprietes optiques lineair... more Le premier chapitre de cette these concerne l'etude theorique des proprietes optiques lineaire et non lineaires de cibles organiques et organometalliques experimentales de l'equipe, en particulier de derives carbo-benzeniques quadrupolaires. Les methodes de calcul et d'analyse standard des etats excites sont tout d'abord presentees, ainsi que deux outils d'analyse developpes dans ce travail concernant : (i) le caractere transfert de charge en termes de densite de " trou " et de " particule ", et (ii) la visualisation du moment dipolaire de transition a partir de la densite de transition tronquee (TTD) aux principales mono-excitations. Les premiers etats excites des chromophores calcules au niveau TD-DPT, ainsi qu'au niveau CAS-PT2 pour certains chromophores modeles, sont ensuite analyses. Les spectres d'absorption UV-visible a 1 photon des derives carbo-benzeniques s'inscrivent dans le cadre du modele de Gouterman propose pour les ...
Angewandte Chemie International Edition
Direct selective oxidation of hydrocarbons to oxygenates by O 2 is challenging.C atalysts are lim... more Direct selective oxidation of hydrocarbons to oxygenates by O 2 is challenging.C atalysts are limited by the low activity and narrowapplication scope,and the main focus is on active C À Hb onds at benzylic positions.I nt his work, stable, lead-free,Cs 3 Bi 2 Br 9 halide perovskites are integrated within the pore channels of mesoporous SBA-15 silica and demonstrate their photocatalytic potentials for CÀHb ond activation. The composite photocatalysts can effectively oxidize hydrocarbons (C 5 to C 16 including aromatic and aliphatic alkanes) with ac onversion rate up to 32900 mmol g cat À1 h À1 and excellent selectivity (> 99 %) towards aldehydes and ketones under visible-light irradiation. Isotopic labeling,insitu spectroscopic studies,a nd DFT calculations reveal that well-dispersed small perovskite nanoparticles (2-5 nm) possess enhanced electronhole separation and ac lose contact with hydrocarbons that facilitates C(sp 3) À Hbond activation by photoinduced charges.
The Journal of Chemical Physics
High Resolution Transmission Electron Microscopy (HR TEM) is used to identify the size, shape, an... more High Resolution Transmission Electron Microscopy (HR TEM) is used to identify the size, shape, and interface structure of platinum nanoparticles and carbon support of a fuel cell catalyst. Using these insights, models accessible to quantum chemical methods are designed in order to rationalize the observed features. Thus, basal plane and prism face models of the carbon black material are considered, interacting with Pt clusters of sizes up to 1 nm. Particular attention is paid to the electronic structure of the carbon support, namely, the radical character of graphene zigzag edges. The results show that a stronger interaction is found when the nanoparticle is at the zigzag edge of a basal plane due to the combination of dispersion interaction with the support structure and covalent interaction with carbon atoms at the edge. In this case, a distortion of both the Pt nanoparticle and the carbon support is observed, which corresponds to the observations from the HR TEM investigation. Furthermore, the analysis of the charge transfer upon interaction and the influence of the potential on the charge states and structure is carried out on our model systems. In all cases, a clear charge transfer is observed from the carbon support to the Pt nanoparticle. Finally, we show that changing the potential not only can change the charge state of the system but can also affect the nature of the interaction between Pt nanoparticles and carbon supports.
Angewandte Chemie, 2016
A ring carbo-mer of naphthalene, C32Ar8 (Ar=p-n-pentylphenyl), has been obtained as a stable blue... more A ring carbo-mer of naphthalene, C32Ar8 (Ar=p-n-pentylphenyl), has been obtained as a stable blue chromophore, after a 19-step synthetic route involving methods inspired from those used in the synthesis of carbo-benzenes, or specifically devised for the present target, like a double Sonogashira-type coupling reaction. The last step is a SnCl2/HCl-mediated reduction of a decaoxy-carbo-decalin, which is prepared through successive [8+10] macrocyclization steps. Two carbo-benzene references are also described, C18Ar6 and o-C18Ar4(C C-SiiPr(3))(2). The carbo-naphthalene bicycle is locally aromatic according to structural and magnetic criteria, as revealed by strong diatropic ring current effects on the deshielding of H-1 nuclei of the Ar groups and on the negative value of the DFT-calculated NICS at the center of the C-18 rings (-12.8 ppm). The stability and aromaticity of this smallest fused molecular fragment of alpha-graphyne allows prediction of the same properties for the carbon allotrope itself.
Journal of chemical theory and computation, Jan 22, 2016
The optical properties of several quadrupolar carbo-benzene derivatives are investigated at vario... more The optical properties of several quadrupolar carbo-benzene derivatives are investigated at various levels of calculation (TDDFT and CASPT2) and analyzed using a new theoretical tool here disclosed: The "visualization" of the transition dipole moment from the transition density truncated to the main monoexcitations involved in the electronic transition (TTD). The experimental or calculated one-photon UV-visible absorption spectra of the carbo-benzene derivatives fit with the Gouterman model originally proposed for porphyrins, where the first four excited states involve linear combinations of monoexcitations of the same four frontier molecular orbitals. The relative intensities of the absorption bands are analyzed from the transition dipole moments calculated from the TTDs and an analogy between porphyrins and carbo-benzenes is argued. The two-photon absorption (TPA) cross section related to the third-order nonlinear optical response is calculated for each two-photon-allowe...
Chemistry - A European Journal, 2016
Numerous studies have underlined the putative diradical character of π-conjugated molecules that ... more Numerous studies have underlined the putative diradical character of π-conjugated molecules that can be described by closed-shell Lewis structures, for instance, p-dimethylene p-n phenylenes, or long polyacenes. In the latter compounds, the only way to save the aromaticity of the six-membered rings is to give up the Lewis electron pairing in the singlet biradical ground state. The present work considers the possibility of doing the same by using the basic C2 units of carbo-meric architectures. A series of acyclic and cyclic carbo-meric architectures is studied by using UB3LYP DFT broken-symmetry calculations, including spin decontaminations and subsequent geometry optimization of the singlet diradical. The C2 units are shown to stabilize the singlet biradical by spin delocalization, two of them playing approximately the same role as one radical-insulating 1,4 phenylene moiety. The results are generalized to the investigation of open-shell polyradical singlet states of rigid hydrocarbon structures, the symmetry and rigidity of which can assist cooperativity and self spin polarization effect. Several synthesis targets with challenging magnetic/spin properties are suggested in the carbo-mer series.
European Journal of Inorganic Chemistry, 2015
Invited for the cover of this issue is the group of Remi Chauvin from the Laboratoire de Chimie d... more Invited for the cover of this issue is the group of Remi Chauvin from the Laboratoire de Chimie de Coordination, Toulouse, France. The cover image shows the polarization of a neutral PdII complex in three steps presented on three levels of the marine background.
Angewandte Chemie International Edition, 2015
The carbo-mer of the para-quinodimethane core is stable within in a bis(9-fluorenylidene) derivat... more The carbo-mer of the para-quinodimethane core is stable within in a bis(9-fluorenylidene) derivative. Oxidation of this carbo-quinoid with MnO2 in the presence of SnCl2 and ethanol affords the corresponding p-bis(9-ethoxy-fluoren-9-yl)-carbo-benzene. The latter can be in turn converted back into the carbo-quinoid by reduction with SnCl2 , thus evidencing a chemical reversibility of the interconversion between a pro-aromatic carbo-quinoid and an aromatic carbo-benzene, and is reminiscent of the behavior of the benzoquinone/hydroquinone redox couple (in the red-ox opposite sense).
Journal of Organometallic Chemistry, 2014
ABSTRACT The electronic spectra of 4 cyclometalated ruthenium compounds built up from cycloruthen... more ABSTRACT The electronic spectra of 4 cyclometalated ruthenium compounds built up from cycloruthenated 2-phenylpyridine with monodentate and bidentate ligands, namely 1 [Ru(MeCN) 2 (phen)(PhPy)] 1þ (RDC11), 2 [Ru(phen) 2 (PhPy)] 1þ (RDC34), 3 [Ru(MeCN) 2 (PhPy)(dppz)] 1þ (RDC11Z), 4 [Ru(bpy) (PhPy)(dppz)] 1þ (RDCbpZ), the last two being newly synthesized, have been recorded and calculated together with that of 5 [Ru(bpy) 2 (dppz)] 2þ (RDNbpZ). Recently synthesized variants of RDC34 where the phenylpyridine ligand is substituted with an electro-attractor or an electro-donor group, 6 [Ru(phen) 2 (NO 2 PhPy)] 1þ RDC40 and 7 [Ru(phen) 2 (NH 2 PhPy)] 1þ RDC41 respectively, and the dicationic reference complex [Ru (phen) 2 (bpy)] 2þ (RDN34) have been investigated as well for comparison. The global structures of RDC34 and RDN34 are very similar despite of the substitution of one N atom by one C atom. As expected a shortening of the RueC bond as compared to the RueN bond is observed. The calculated structures of the investigated complexes point to a rather rigid structure whatever their environment. The introduction of a strong RueC bond has a minor effect on the coordination sphere around the metal atom keeping the other RueN bonds and bond angles similar, the only noticeable alteration being an increase of the RueN bond trans to the RueC bond. The experimental spectra are characterized by an intense band in the UV domain centered at 270 nm and corresponding to a strong intra-ligand (IL) absorption. Low-lying MLCT states contribute to a weak shoulder around 370 nm and to a large band between 550 nm and 400 nm. The tail of this band, towards 650 nm, is a characteristic of the cyclometalated complexes. This series of molecules, as other polypyridyl complexes, are characterized by a high density of excited states in the vis/UV energy domain, a large mixing between MLCT/IL and LLCT states in the upper part of the spectrum, and a significant sensitivity to the environment of the IL state localized on the dppz ligands.
In this work, we employ electronic structure methods to investigate the structure and reactivity ... more In this work, we employ electronic structure methods to investigate the structure and reactivity of IrO x nanoparticle models as catalysts for the oxygen evolution reaction (OER). Based on the explicit inclusion of the potential and pH in a constant potential framework, a computational approach is applied to investigate the thermodynamics of the proton and electron transfer process of IrO x cluster models. We address structural changes of the clusters under electrochemical conditions by constructing potential−pH diagrams from our computational results. Comparison of two IrO x cluster structures suggests that the charge transport to the clusters strongly depends on the pH. As a result, structures with a maximum number of on-top hydroxyl (OH μ1) species are stable at low potentials and deprotonation becomes favorable with increasing potential. An assessment of the Ir oxidation states in our models shows that mixed oxidation states, i.e., Ir IV and Ir V , occur around the OER onset potential and increase to higher oxidation states (Ir VI) in the high potential regime. Furthermore, an investigation of the water adsorption mechanism is carried out at different potentials.The results suggest that the potential controls the energetics of intermediates as well as transition states during the OER.
Chemistry - A European Journal, 2015
The synthesis, crystal and electronic structures, and one-and two-photon absorption properties of... more The synthesis, crystal and electronic structures, and one-and two-photon absorption properties of two quadrupolar fluorenyl-substituted tetraphenyl carbo-benzenes are described. These all-hydrocarbon chromophores, differing in the nature of the linkers between the fluorenyl substituents and the carbo-benzene core (CÀC bonds for 3 a, CÀCCÀC expanders for 3 b), exhibit quasi-superimposable one-photon absorption (1PA) spectra but different twophoton absorption (2PA) cross-sections s 2PA . Z-scan measurements (under NIR femtosecond excitation) indeed showed that the CC expansion results in an approximately twofold increase in the s 2PA value, from 336 to 656 GM (1 GM = 10 À50 cm 4 s molecule À1 photon À1 ) at l = 800 nm. The first excited states of A u and A g symmetry accounting for 1PA and 2PA, respectively, were calculated at the TDDFT level of theory and used for sum-over-state estimations of s 2PA (l i ), in which l i = 2 hc/E i , h is Planck's constant, c is the speed of light, and E i is the energy of the 2PA-allowed transition. The calculated s 2PA values of 227 GM at 687 nm for 3 a and 349 GM at 708 nm for 3 b are in agreement with the Z-scan results. . It contains the synthetic principle of 5 b, photoluminescence spectra of 3 a and 3 b, the normalized transmittance curve of 3 b from Z-scan measurements, the near-frontier molecular orbitals of 3 a and 3 b, characteristics of the first singlet excited states of 3 a and 3 b (in vacuo and chloroform continuum), the contribution of intermediate 1PA-allowed states in the SOS expansion of the 2PA cross-section associated with the 4A g excited state of 3 a and 3 b, and copies of 1 H and 13 C NMR spectra, MS analyses, and voltammograms of 3 a and 3 b.
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Papers by Corentin Poidevin