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International audience; The chemical preparation, crystal structure and spectroscopic characterization of the novel noncentrosymmetric (S)nicotiniumtrichloridozincate monohydrate complex are reported. The atomic arrangement can be described as built up by chains of ZnNCl3 tetrahedra and water molecules, interconnected via O-H center dot center dot center dot Cl hydrogen bonds. The organic entities are inserted between these chains through C-H center dot center dot center dot Cl and N-H center dot center dot center dot Cl hydrogen bonds. The 3D Hirshfeld surfaces and the associated 2D fingerprint plots were investigated for intermolecular interactions. The C-13 and N-15 CP-MAS NMR spectra are in agreement with the X-ray structure. The vibrational absorption bands were identified by infrared spectroscopy. DFT calculations allowed the attribution of the NMR peaks.

The reactivity of (E)- and (Z)-1-fluorobuta-1,3-diene ((E)- and (Z)-11), 2-fluorobutadiene (12), (E)- and (Z)-1-(fluoromethylidene)-2-methylidenecyclohexane ((E)- and (Z)-13) toward SO(2) has been explored and compared with that of (Z)- and (E)-1-(fluoromethylidene)-2-methylidene-3,4-dihydronaphthalene ((Z)-8 and (E)-8). In agreement with quantum calculations, 12 is unreactive toward SO(2) (no cycloaddition, only polymerization), whereas (E)-1-fluoro-1,3-dienes react more rapidly than their (Z)-isomers to give the corresponding 6-fluorosultines following the endo (Alder rule) mode of hetero-Diels-Alder addition. No sulfolene has been observed following the cheletropic mode of addition with the fluorodienes, in contrast to other substituted dienes. In agreement with the calculations, cis-2-fluoro-3,4-oxathiabenzobicyclo[4.4.0]dec-1(6),9-diene-4-oxide (cis-9, the sultine obtained by SO(2) addition to (Z)-8 under conditions of kinetic control) adopts a sofa conformation with the oxygen atom of the ring lying in the average plane of the four carbon atoms of its sultine moiety when it is in the crystalline state at -100 degrees C. A similar sofa conformation was found for its trans-isomer, trans-9, obtained by isomerization of cis-9 or by hetero-Diels-Alder addition of SO(2) to (E)-8. Experiments (equilibrium constant for hetero-Diels-Alder additions, bond lengths, and bond angles in crystalline fluorosultines cis-9 and trans-9) and high-level quantum calculations on cis- and trans-6-fluoro-3,6-dihydro-1,2-oxathiin-2-oxide (cis- and trans-20) confirm the existence of a stabilizing, enthalpic, anomeric (gem-disubstitution by sulfinyloxy and fluoro groups) effect, which is interpreted in terms of (lone pair) n(O1)--sigma*(C-F) hyperconjugative interactions. This effect is strongest in the sofa conformers with a gauche arrangement of the sigma(O1,S2) and sigma(C6,F) bonds. The calculations suggest also that n(O1)--sigma*(S2,O2'), pi*(S=O), and n(S2)--sigma*(O1,C6) interactions intervene and affect the relative stability of the conformers (sofa, boat, pseudo-chair) found for 6-fluorosultines cis- and trans-20.

International audience; Organofluorine is a weak hydrogen-bond (HB) acceptor. Bernet et al. have demonstrated its capability to perturb OH center dot center dot center dot O intramolecular hydrogen bonds (IMHBs), using conformationally rigid carbohydrate scaffolds including levoglucosan derivatives. These investigations are supplemented here by experimental and theoretical studies involving six new levoglucosan derivatives, and complement the findings of Bernet et al. However, it is shown that conformational analysis is instrumental in interpreting the experimental data, due to the occurrence of non-intramolecular hydrogen-bonded populations which, although minor, cannot be neglected and appears surprisingly significant. The DFT conformational analysis, together with the computation of NMR parameters (coupling constants and chemical shifts) and wavefunction analyses (AIM, NBO), provides a full picture. Thus, for all compounds, the most stabilized structures show the OH groups in a conformation allowing IMHB with O5 and O6, when possible. Furthermore, the combined approach points out the occurrence of various IMHBs and the effect of the chemical modulations on their features. Thus, two-center or three-center IMHB interactions are observed in these compounds, depending on the presence or absence of additional HB acceptors, such as methoxy or fluorine.

Thermo-responsive materials, such as poly(vinylmethylether) (PVME), attract a common attention because of their unique physical properties resulted from metastable equilibrium between various types of interactions. In this work Monte Carlo (MC) and quantum-mechanical (QM) methods were used to study excluded volume and electrostatic interactions respectively. The graining procedure of PVME-water system was proposed. Its implementation to MC calculations allowed to distinguish how two water fractions differ on dynamics. The QM calculations showed that the formation of cyclic clusters leads to the lengthening of the hydrogen bonds and consequently to higher energies in comparison to linear forms, which is crucial looking at an application of QM results to MC calculation considering thermal interactions.

In order to find the particular interaction energy between cylcloguanil and the amino acids surrounding the pocket of wild type and quadruple mutant type PfDHFR enzymes, the MP2 method with basis set 6-31G(d,p) level of calculations was performed. The obtained interaction energies found that Asp54 has the strongest interaction energy to both wild type and mutant type of - 12.439 and -11.250 kcal/mol, respectively and three amino acids; Asp54, Ile164 and Ile14 formed the H-bonding with cycloguanil drug. Importantly, the mutation at Ser108Asn was the key important of cycloguanil resistant with showing repulsive interaction energy., {"references":["P. L. Olliaro, and Y. Yuthavong, \"An overview of chemotherapeutic\ntargets for antimalarial drug discovery,\" Pharmacol. Ther., vol. 81, pp.\n91-110, 1999.","Y. Yuthavong, S. Kamchonwongpaisan, U. Leartsakulpanich and P.\nChitnumsub, \"Folate Metabolism as a Source of Molecular Targets for\nAntimalarials,\" Future Microb. vol. 1, no.1, pp. 113-125, 2006.","A. Nzila, \"Inhibitors of De-novo Folate Enzymes in Plasmodium\nfalciparum,\" Drug Discov. Today, vol. 11, pp. 936-944, 2006.","K.Militello, M. Dodge, L. Bethke and D. F. Wirth, \"Identification of\nregulatory elements in the Plasmodium falciparum genome,\" Mol.\nBiochem. Parasitol, vol. 134, pp. 75-88, 2004.","T. Dasgupta, and K. S. Anderson, \"Probing the Role of Parasite-\nSpecific, Distant Structural Regions on Communication and Catalysis in\nthe Bifunctional Thymidylate Synthase- Dihydrofolate Reductase from\nPlasmodium falciparum,\" Biochemistry, vol. 47, no. 5, pp. 1336-1345,\n2008.","A. Nzila, \"The Past, Present and Future of Antifolates in the Treatment\nof Plasmodium falciparum Infection,\" J. Antimicrob Chemother, vol. 57,\npp. 1043-1054, 2006.","R.T. Delfino, O. A. Santos-Filho and J. D. Figueroa-Villar, \"Type 2\nantifolates in the chemotherapy of falciparum malaria,\" J. Braz. Chem.\nSoc. vol. 13, pp. 727-741, 2002.","Y. Yuthavong, \"Basic for antifolate action and resistance in malaria.\nMicrobes Infect,\" vol. 4, pp. 175-182, 2002.","Y. Yuthavong, J. Yuvaniyama, P. Chitnumsub, J. Vanichtanankul, S.\nChusacultanachai, B. Tarnchompoo, T. Vilaivan and S.\nKamchonwongpaisan, \"Malarial (Plasmodium falciparum) dihydrofolate\nreductase-thymidylate synthase: structural basis for antifolate resistance\nand development of effective inhibitors,\" Parasitology, vol. 130, pp.\n249-259, 2005.\n[10] L. K. Basco, P. E. Pecoulas, C. M. Wilson, J. L. Bras and A. Mazabraud,\n\"Point mutations in the dihydrofolate reductase-thymidylate synthase\ngene and pyrimethamine and cycloguanil resistance in Plasmodium\nfalciparum,\" Mol. Biochem. Parasitol, vol. 69, pp. 135-138, 1995.\n[11] D. S. Peterson, W. K. Milhous and T. E. Wellems, \"Molecular basis of\ndifferential resistance to cycloguanil and pyrimethamine in Plasmodium\nfalciparum malaria,\" Proc. Natl. Acad. Sci. U.S.A., vol. 87, pp. 3018-\n3022, 1990.\n[12] A. Gregson, and C.V. Plowe, \"Mechanisms of Resistance of Malaria\nParasites to Antifolates,\" Pharmacol. Rev. vol. 57, pp. 117-145, 2005.\n[13] I. M. Hastings, and M. J. Donnelly, \"The impact of antimalarial drug\nresistance mutations on parasite fitness, and its implications for the\nevolution of resistance,\" Drug Resist. Updat, vol. 8, pp. 43-50, 2005.\n[14] G.Rastelli, S. Sirawaraporn, P. Sompornpisut, T. Vilaivan, S.\nKamchonwongpaisan, R. Quarrell, G. Lowe, Y. Thebtaranonth and Y.\nYuthavong, \"Interaction of pyrimethamine, cycloguanil, WR99210 and\ntheir analogues with Plasmodium falciparum dihydrofolate reductase:\nstructural basis of antifolate resistance,\" Bioorg. Med. Chem. vol. 8, pp.\n1117-1128, 2000.\n[15] W. Sirawaraporn, T. Sathitkul, R. Sirawaraporn, Y. Yuthavong and\nD.V. Santi, \"Antifolate-resistant mutants of plasmodium falciparum\ndihydrofolate reductase,\" Proc. Natl. Acad. Sci. vol. 94, pp. 1124-1129,\n1997.\n[16] J. Yuvaniyama, P. Chitnumsub, S. Kamchonwongpaisan, J.\nVanichtanankul, S. Sirawaraporn, P. Taylor, M. D. Walkinshaw and Y.\nYuthavong, \"Insights into antifolate resistance from malarial DHFR-TS\nstructures,\" Nat. Struct. Bio,. vol. 10, pp. 357-365, 2003.\n[17] G. B. Fogel, M. Cheung, E. Pittman and D. Hecht, \"Modeling the\ninhibition of quadruple mutant Plasmodium falciparum dihydrofolate\nreductase by pyrimethamine derivatives,\" J. Comput Aided Mol Des,\nvol. 22, pp. 29-38, 2008.\n[18] S. Kamchonwongpaisan, R. Quarrell, N. Charoensetakul, R. Ponsinet, T.\nVilaivan, J. Vanichtanankul, B. Tarnchompoo, W. Sirawaraporn, G.\nLowe and Y. Yuthavong, \"Inhibitors of multiple mutants of plasmodium\nfalciparum dihydrofolate reductase and their antimalarial activities,\" J.\nMed. Chem, vol. 47, pp. 673-680, 2004.\n[19] M. D. Parenti, S. Pacchioni, A. M. Ferrari, and G. Rastelli, \"Three-\nDimensional Quantitative Structure-Activity Relationship Analysis of a\nSet of Plasmodium falciparum Dihydrofolate Reductase Inhibitors Using\na Pharmacophore Generation Approach,\" J. Med. Chem, vol. 47, pp.\n4258-4267, 2004.\n[20] P. Maitarad, P. Saparpakorn, , S. Hannongbua, S. Kamchonwongpaisan,\nB. Tarnchompoo, Y. Yuthavong, \"Particular Interaction between\nPyrimethamine Derivatives and Quadruple Mutant Type Dihydrofolate\nReductase of Plasmodium falciparum: CoMFA and Quantum Chemical\nCalculations Studies,\" J. Enzyme. Inhibition and Medicinal Chemistry,\n2008, in press."]}

International audience; The present paper deals with a fine physico-chemical analysis of some hybrid materials combining an inorganic layered double hydroxide phase (LDH) with an organic benzene derivative entity R′-C6H4-R with R = -SO3-, -CO2- and R′ = -H, -OH. The main topic of this work is, in a nanoscale, to propose a way to approach the understanding of the interactions between inorganic and organic sub-systems. The role of the anionic headgroup R is discussed in term of reactivity with the mineral support. The classical expertise of materials via the PXRD technique puts into light an effective LDH interlayer space enlargement with the organics incorporation and a minimum angle of inclination for every organics within the LDH matrix. The originality of this study is to use the X-Ray Photoelectron spectroscopy (XPS) as a local probe of the chemical environments of the headgroup of the organic entities. In a parallel way, some quantum calculations (by using molecular and periodical codes) are carried out to best appreciate the electronic and structural evolutions before and after the intercalation step. A specific reactivity of the -SO3- group compared with the -CO2- one is evidenced. Moreover, a correlation at the first order is then set up between the net charges of atoms and the XPS binding energies of their core levels.

This thesis concerns the theoretical study of the interaction mechanisms of carbon-based nanostructures with cell membranes, being the essential compound of living cells. This very complex study of the multidisciplinary nature was essentially done using numerical simulations. We have voluntarily spitted this work in two distinct parts. First, we studied the membrane ion channels using molecular dynamics and ab initio approaches. These channel proteins being essential for cell function are also common therapeutic targets for new drugs design. Second, we studied the behavior of pristine and functionalized carbon species such as fullerenes (C60) and nanotubes (CNT) in the presence of the cell membrane. The results focus mainly on passive uptake phenomenon of these potential drugs vectors by biological membranes. The molecular dynamics studies on a very long time scale (sub-1 microseconds) and on very large systems were also the challenge of the IT perspective. To solve the given problematic in the limited time of a single PhD the development of high performance parallel computing CPU/GPU had to be put in place. The obtained results tempt to highlight the toxic role of nanostructures versus previously studied membrane proteins. This thesis naturally opens the way for the study of biocompatible nanocarriers for drug delivery.; Ce travail de thèse concerne l'étude théorique des mécanismes d'interaction de nanostructures à base de carbone avec les membranes cellulaires, constituant l'essentiel des cellules vivantes. Ce sujet très complexe compte tenu de la pluridisciplinarité de la thématique a été essentiellement réalisé à l'aide de simulations numériques. Nous avons volontairement partagé ce travail en deux parties distinctes. Nous avons d'abord étudié le fonctionnement des canaux ioniques à l'aide de la dynamique moléculaire et des études ab-initio. Ces canaux sont d'une part des protéines membranaires essentielles pour la fonction cellulaire, et d'autre part, elles constituent aussi des cibles thérapeutiques fréquentes dans la recherche des nouveaux médicaments. Dans une seconde partie, nous avons étudié le comportement d'espèces carbonées nus et fonctionnalisés tels que les fullerènes (C60) et les nanotubes (CNT) en présence de la membrane cellulaire en analysant finement le mécanisme d'ingestion (ang. uptake) de ces vecteurs de médicaments potentiels par les membranes biologiques. Ces études en dynamique moléculaire sur des temps très longs (sub-1 μs) et sur des systèmes très vastes étaient aussi le challenge du point de vue informatique. Pour palier la problématique dans le temps limitée d'une thèse le développement des calculs parallèles de haute performance CPU/GPU a du être mis en place. Les résultats obtenus tentent de mettre en évidence le rôle toxique que peuvent présentées certaines nanostructures vis-à-vis des protéines membranaires précédemment étudiées. Ce travail de thèse ouvre naturellement la voie à l'étude des nanovecteurs biocompatibles pour la délivrance des médicaments.

By assuming that not only counter-ions but DNA molecules as well are thermally distributed according to a Boltzmann law, we propose a modified Poisson-Boltzmann equation at the classical level as starting point to compute the effects of quantum fluctuations of the electric field on the interaction among DNA-cation complexes. The latter are modeled here as infinite one-dimensional wires ($\delta$-functions). Our goal is to single out such quantum-vacuum-driven interaction from the counterion-induced and water-related interactions. We obtain a universal, frustration-free Casimir-like (codimension 2) interaction that extensive numerical analysis show to be a good candidate to explain the formation and stability of DNA aggregates. Such Casimir energy is computed for a variety of configurations of up to 19 DNA strands in a hexagonal array. It is found to be strongly many-body., Comment: 8 figures

The experimental section in this thesis was based on the work of Kanan, M.W, et al reported in Science in December of 2008. A catalyst containing cobalt and phosphate was synthesized and used to decompose water into oxygen and hydrogen. This was done at nearly neutral pH. Cyclic voltammetry was performed to analyze the catalyst’s efficiency. Some surfaces were analyzed in a scanning electron microscope and the elemental composition was determined using energy-dispersive X-ray spectroscopy. A catalytic effect was observed at a potential of about 1,3 V. EDX showed Co at some of the surfaces. Quantum calculations were used to develop a model for the catalyst material. Molecular orbitals, interaction energies and vibrational frequencies were calculated for two different complexes of Co and phosphate. Patrik Larses was responsible for the electrochemical evaluation and synthesis in the experimental section of this thesis and Lina Tegesjö for the computational part.

Different computational methods are employed to evaluate elastic (rotationally summed) integral and differential cross sections for low energy (below about 10 eV) positron scattering off gas-phase C 2 H 2 molecules. The computations are carried out at the static and static-plus-polarization levels for describing the interaction forces and the correlation–polarization contributions are found to be an essential component for the correct description of low-energy cross section behavior. The local model potentials derived from density functional theory (DFT) and from the distributed positron model (DPM) are found to produce very high-quality agreement with existing measurements. On the other hand, the less satisfactory agreement between the R-matrix (RM) results and measured data shows the effects of the slow convergence rate of configuration-interaction (CI) expansion methods with respect to the size of the CI-expansion. To contrast the positron scattering findings, results for electron–C 2 H 2 integral and differential cross sections, calculated with both a DFT model potential and the R-matrix method, are compared and analysed around the shape resonance energy region and found to produce better internal agreement.

International audience; The new European regulation of chemicals named REACH (for "Registration, Evaluation and Authorization of CHemicals", published by the European Commission in December 2006) implies that a tremendous number of substances (up to 30000) may require a new assessment of hazardous properties. Therefore, there is a growing interest in evaluating capabilities of predictive methods for assessing hazardous properties of chemical substances as a screening process. If Quantitative Structure-Property Relationship (QSPR) type methods have been up to now mainly devoted to screening toxic properties, their use to establish relationships between the explosibility of dangerous substances and structural, energetic or physicochemical descriptors could lead to new perspectives. This contribution focuses on the case of a series of nitroaromatic compounds, which are all expected to present more or less severe explosive properties due to the presence of the nitro group. In particular, this paper shows that a multilinear regression model links correctly adequate molecular descriptors of nitroaromatic compounds with thermal stability (taken as a macroscopic property related to explosibility). The descriptors are mostly obtained by ab initio quantum chemical calculations. Moreover, we present a detailed theoretical investigation on the decomposition pathways of substituted nitrobenzenes using quantum chemical methods that provide pertinent information for the use of descriptors in relation with energetic aspects to access to more robust QSPR models

The humic substances (HS) result from the degradation of organic residues and represent the greatest part of the organic matter of the natural systems. The HS are able to trap many pollutants like heavy metals and play a major role in the metal ions retention. Their chelating properties are due mainly to some recurring functions: carboxylic and phenolic groups.In a 1st part, the study of the complexation of model molecules involving similar sites to those met in the natural biopolymers makes it possible to know the chelating capacities of the most widespread functions (catechol, hydroxy-carbonyl and carboxylic acid). Spectroscopic techniques combined with quantum chemical calculations provides us the chelating capacities classification of the mono-site compounds toward the metallic ions Al(III), Pb(II) and Zn(II). We show whereas that this type of classification is preserved when the sites are in competition within the same structure.In a 2nd part, the examination by synchronous fluorescence of the 3 polluting metals complexation by a standard humic acid (HA) made it possible to highlight different behaviors for each one of them, reflecting distinct fixing mechanisms and a specificity of the metal-humic interactions. We have established a classification of the chelating powers of HA towards the 3 cations in agreement with those obtained by the models. Lastly, the competition between HA and two organic molecules of low molecular size have shown that the percentages of pollutants extracted to the humic acid are weak and this one remains a "toxic reservoir" in the natural environments.; Les substances humiques (SH) sont issues de la dégradation de résidus organiques et représentent la partie la plus importante de la matière organique des systèmes naturels. Les SH sont capables de piéger de nombreux polluants comme les métaux lourds et jouent donc un rôle majeur dans la rétention des ions métalliques. Leurs propriétés complexantes sont dues principalement à certaines fonctions récurrentes : les groupements carboxyliques et phénoliques.Dans une 1ère partie, l'étude de la complexation de molécules modèles possédant des sites similaires à ceux rencontrés dans les biopolymères naturels a permis d'évaluer les capacités complexantes des fonctions les plus répandues (catéchol, hydroxy-carbonyle et acide carboxylique). L'association de techniques spectroscopiques et de calculs de chimie quantique a permis d'établir un classement des pouvoirs chélatants des composés mono-sites vis-à-vis des ions métalliques Al(III), Pb(II) et Zn(II)), et a montré que ce type de classement est conservé lorsque les sites sont en compétition au sein d'une même structure.Dans une 2nde partie, l'examen par fluorescence synchrone de la complexation des 3 métaux polluants par un acide humique standard (AH) a mis en évidence des comportements différents pour chacun d'eux, reflétant des mécanismes de fixation distincts et une spécificité des interactions métallo-humiques. Nous avons ainsi pu établir un classement du pouvoir complexant de AH vis à vis des 3 cations, en accord avec celui obtenu pour les modèles. Enfin, la compétition entre AH et deux molécules organiques de faible poids moléculaires a montré que les pourcentages de polluants extraits de l'acide humique sont faibles et que celui-ci reste un véritable « réservoir toxique » au sein des milieux naturels.

Solving the nuclei motion Schrodinger equation with only Born-Oppenhiemer approximation remains a great challenge, due to the exponential scaling of the computation. A full-dimensional basis set method utilizing phase space optimized (PSO) discrete variable representations (DVRs), designed to efficiently compute the rovibrational states of triatomic systems with long-range interactions, has been applied to the benchmark Li-(H2) ion-molecule system and the He(H2) van der Waals complex system. These applications are very challenging due to the long range nature of the interaction and the narrow level spacings near dissociation. All of the rovibrational bound states and a number of resonance states are computed to very high accuracy (one ten-thousandth of a wavenumber or better). For Li-(H2) several new bound levels are reported. The resonances exhibit a clear-cut separation into shape and Feshbach varieties, with the latter characterized by extremely long lifetimes (microseconds or longer). For He(H2) three different isotopologues are considered, all of which are found to have a single bound state with a very low binding energy. Several extremely long-lived Feshbach resonances are also reported. In order to beat the exponential scaling of basis set methods, a DVR matrix dynamics formulation of the path integral Monte Carlo (PIMC) method is proposed as a means of computing ground state quantum wavefunctions. A key advantage of the DVR-PIMC approach is that customized marginal potentials may be employed, leading to significantly larger PIMC time step sizes, and substantial reductions in computational (CPU) effort. An additional key advantage of the present implementation is that the DVR provides a natural set of interpolant functions that can be used for accurate interpolation and extrapolation of function and tensor quantities away from the predefined grid points. This new method is applied to H2O, Ne3 and Ne4, which showed nearly linear scaling for both CPU and memory usage. Owing to the direct simulation of wavefunctions, statistical error of PIMC for energy calculations is reduced greatly, and extrapolation can be used to further speed PIMC convergence.

There exists, today, many and effective methods of three-dimensional structural characterization of biological compounds in the condensed phase (NMR, X-ray diffraction or circular dichroism). In the last ten years, this field has extended to the gas phase. This work falls in this context and considers the structuring role of Na+ on the ! amino acids Gly and Pro and on oligo-peptides of Gly and Ala, ! by combi ning theoretical calculations and infra-red spectroscopy of gaseous ions by multiphoton dissociation (IRMPD), coupled to mass spectrometry. Experimental IRMPD spectra of the sodiated amino acid complexes, enabled us to identify the exclusive presence of the zwitterionic form in the case of Pro-Na+ and the presence of the non-zwitterionic form in the case of Gly-Na+, in accordance with quantum chemical results. Thus we provided the first direct demonstration of the presence of a zwitterion of an amino acid in gas phase. These were the first infra-red spectra of biological ions in the gas phase. The theoretical study of the Glyn-Na+ and Alan-Na+ complexes showed that for n

The interstellar ices are mainly composed of CO, H2O, NH3, .... Under a luminous flow coming from stars (λ > 120 nm) these ices are subjected to photochemical processing and can evolve to the formation of new and more complex products. Among them, the isocyanic acid (HNCO) is found which we have studied the reactivity with H2O, NH3 and NH3/H2O ices. We have shown that it was been at the origin of the OCN- formation. This ion can be characterised by ISO spectra of protostellar sources, from its band at 4,62 μm (2167 cm-1). A spontaneous production of OCN-, in agreement with the temperature range (10 - 100 K) which ices evolve, is produced when HNCO and NH3 in excess are codeposed at 10 K. A salt analogous at NH4+OCN- is formed at above 160 K. Quantum calculations have shown that solvation of NH3 molecule in direct interaction with HNCO by three other NH3 molecules, plays an important role into the NH4+ and OCN- formation process and confirm the spontaneous character of this reaction. The UV irradiation (λ > 120 nm) of solid HNCO leads to the OCN- formation but also carbonyl compounds as formaldehyde, formamide, and urea. The comparison of the primary photoproducts spectrum with ISO spectrum of NGC7538 IRS9 or W33A ices, could give a tentative attribution for the bands located at 1700 cm-1 and 1470 cm-1., Les glaces interstellaires sont composées de CO, H2O, NH3, .... Soumis à un flux lumineux émanant des étoiles (λ > 120 nm) ces glaces peuvent évoluer vers la formation de molécules plus complexes. Parmi celles-ci, on trouve l'acide isocyanique (HNCO) dont nous avons étudié la réactivité avec des glaces de H2O, de NH3, de NH3/H2O. Nous avons montré qu'il pouvait être à l'origine de la formation de l'ion OCN-. Cet ion peut être caractérisé sur les spectres ISO de sources protostellaires, par sa bande dite "XCN" à 4,62 μm (2167 cm-1). Une production spontanée de l'ion OCN- cohérente avec le domaine de température (10 - 100 K) dans lequel évoluent ces glaces, se produit entre HNCO et NH3 en excès codéposés à 10 K. Un sel analogue à NH4+OCN- est formé au-delà de 160 K. Des calculs quantiques ont montré que la solvatation d'une molécule de NH3 directement liée à HNCO par trois autres molécules de NH3, joue un rôle important dans le processus de formation de NH4+ et OCN- et confirment le caractère spontané de cette réaction. L'irradiation UV (λ > 120 nm) de HNCO solide a conduit à la formation de OCN- mais aussi de composés carbonylés tels que le formaldéhyde, le formamide, et l'urée. La comparaison du spectre des photoproduits primaires avec le spectre ISO des glaces NGC7538 IRS9 ou W33A, permet de donner une tentative d'attribution pour les bandes situées à 1700 cm-1 et 1470 cm-1.

Even unsubstituted butadiene adds to sulfur dioxide in the hetero-Diels-Alder mode more rapidly than in the chelotropic mode. The sultine can be observed in equilibrium with the diene and the sulfur dioxide only at low temperature and in the presence of CF(3)COOH. Crystals of 4,5-dialkyl-sultine resulting from the SO(2) addition to 1,2-dimethylidenecyclohexane have been obtained at -100 degrees C and analyzed by X-ray diffraction. Quantum chemical calculations have shown that hyperconjugative interactions within the sulfinyl moiety are responsible for the anomeric effects observed in sultines that prefer pseudo-chair conformations with pseudo-axial Sdbond;O bonds.

Background Disordered compounds are crucially important for fundamental science and industrial applications. Yet most available methods to explore solid-state material properties require ideal periodicity, which, strictly speaking, does not exist in this type of materials. The supercell approximation is a way to imply periodicity to disordered systems while preserving “disordered” properties at the local level. Although this approach is very common, most of the reported research still uses supercells that are constructed “by hand” and ad-hoc. Results This paper describes a software named supercell, which has been designed to facilitate the construction of structural models for the description of vacancy or substitution defects in otherwise periodically-ordered (crystalline) materials. The presented software allows to apply the supercell approximation systematically with an all-in-one implementation of algorithms for structure manipulation, supercell generation, permutations of atoms and vacancies, charge balancing, detecting symmetry-equivalent structures, Coulomb energy calculations and sampling output configurations. The mathematical and physical backgrounds of the program are presented, along with an explanation of the main algorithms and relevant technical details of their implementation. Practical applications of the program to different types of solid-state materials are given to illustrate some of its potential fields of application. Comparisons of the various algorithms implemented within supercell with similar solutions are presented where possible. Conclusions The all-in-one approach to process point disordered structures, powerful command line interface, excellent performance, flexibility and GNU GPL license make the supercell program a versatile set of tools for disordered structures manipulations. Electronic supplementary material The online version of this article (doi:10.1186/s13321-016-0129-3) contains supplementary material, which is available to authorized users.