The importance of weak interactions between molecules to life and all parts of science and engineering is unquestionable and there have been an enormous interest in such interactions. Among all the weak interactions, hydrogen bonding is the most popular and it has enjoyed the most attention of the scientific community. Halogen bonding is gaining more popularity in the recent time, as its importance to biological molecules and crystal engineering has been recognized. In this work, a Pulsed Nozzle Fourier Transform Microwave spectrometer has been used to study the rotational spectra of molecules and hydrogen bonded complexes. Structural information is obtained from the rotational spectra. Ab initio electronic structure, Natural Bond Orbital (NBO) and Atoms in Molecules (AIM) theoretical methods have been used to characterize the weak intermolecular interactions, including hydrogen bonding, halogen bonding and lithium bonding. In Chapter I, introduction to weak interaction is discussed. A brief introduction of different experimental and theoretical methods is presented. Chapter II discusses in detail about the different methods used to investigate weak interaction, both experimentally and theoretically, in this work. In our lab, we use Pulsed Nozzle Fourier Transform Microwave spectrometer to determine the complexes spectra and structures. We generate MW radiation with the help of electronic devices and use Balle-Flygare cavity where molecular interaction takes place. We inject the sample inside the cavity in form of supersonic molecular beam through a pulsed nozzle, parallel to MW radiation. The detailed instrumental discussion about MW spectrometer has been done in this Chapter. We extensively use theoretical methods to probe weak bonding and characterize them. Ab initio and DFT calculations are used to optimize the structure of the complexes and predict their rotational spectra. Atoms in Molecules theory and Natural Bond Orbital theory are then used with the ab initio wave functions to understand the weak interactions in depth. Discussion about these methods and software used for the analysis will also be discussed. In Chapter III, rotational spectrum of Hexafluoroisopropanol (HFIP) monomer is presented. HFIP is an interesting molecule as it offers many possibilities as hydrogen bond donor and acceptor. It has the OH group which can both accept/donate a hydrogen bond and in addition it has a very acidic CH group. It is the only solvent that can dissolve polyethylene terephthalate, a normally difficult-to-dissolve polymer, and clearly it has unique interactions with this difficult to solve polymer. We have recorded and fitted rotational spectra of five different isotopologues of HFIP which helped us in determining its accurate structure. Though, it can exist in synclinical and antiperiplanar conformers, only the later has been detected in our molecular beam spectrometer. This happens to be the global minimum structure of HFIP. Combination of experimental observations and ab initio calculations provided many evidences which confirmed the presence of antiperiplanar conformer, experimentally. Since, the rotational constants for both conformers were very close, it was always challenging to pick up one conformer as experimentally observed structure. A prototype molecule, hexafluoroisobutene (HFIB) shows doubling of rotational transitions due to tunnelling/counter rotation of the two CF3 groups through a small barrier. Interestingly, such motion has no barrier in HFIP and hence no splitting in transitions was observed. Potential energy surface calculated for counter-rotation of the two CF3 groups is consistent with this observation. This barrier is different from eclipsed-staggered exchange barrier, observed by 60 counter rotation of both terminal CF3 groups, for which the barrier height is very large and tunnelling cannot occur. The origin/lack of the small barrier in HFIB/HFIP has been explored using Natural Bond Orbital (NBO) method which helped in understanding intramolecular bonding in these molecules. Along with HFIB, other prototype molecules were also considered for the analysis e.g. hexafluoroacetone, hexafluoroacetone imine, hexafluoroisobutane, hexafluoroisopropylamine. In the last section of this Chapter, we have discussed the generalized behaviour of molecules which have CF3-C-CF3 groups. In Chapter IV, rotational spectrum of HFIP•••H2O complex is presented. Aqueous solution of HFIP stabilizes α-helical structure of protein, a unique property of this solvent. The main objective of this Chapter is understanding the interaction between HFIP and H2O. Microwave spectrum of HFIP•••H2O was predicted and recorded. Three isotopologues were investigated. Though, this complex could in principle have several structural conformers, detailed ab initio calculations predicted two conformers and only one was observed. Though, the rotational constants for both structures were somewhat similar, lack of a dipole transitions, larger intensity of b-dipole transitions over c-dipole transitions and isotopic substitution analysis positively confirm the structure in which HFIP acts as the hydrogen bond donor. The linear O-H•••O hydrogen bond in HFIP-H2O complex is significantly stronger than that in water dimer with the H•••O distance of 1.8 Å. The other structure for this complex, not found in experiment is cyclic with both C-H•••O and O-H•••O hydrogen bonds, both of which are bent with H•••O distances in the range 2.2-2.3 Å. Both AIM and NBO calculations have been used to characterize the hydrogen bond in this complex. In Chapter V, a comprehensive study on hydrogen bonding, chlorine bonding and lithium bonding have been done. A typical hydrogen bonded complex can be represented as A•••H-D, where A is the acceptor unit and H-D is the hydrogen bond donor unit. Many examples are known in literature, both experimentally and theoretically, in which the A-H-D bond angles are not linear. Deviation from linearity also results in the increase in A•••H bond lengths, as noted above for the two structures of HFIP•••H2O complex. Though this has been known for long, the distance between A and D being less than the sum of their van der Waals ‘radii’ is still used as a criterion for hydrogen bonding by many. Our group has recently shown the inappropriateness of van der Waals ‘radii’ and defined hydrogen bond ‘radii’ for various donors, DH and A. A strong correlation of DH hydrogen bond ‘radii’ with the dipole moment was noted. In this Chapter, we explored in detail the angular dependence of hydrogen bond ‘radii’. Electron density topology around DH (D = F, Cl and OH) has been analyzed in detail and shown to be elliptical. For these molecules, the two constants for H atom treated as an ellipse have been determined. It is hoped that these two constants will be used widely in analyzing and interpreting H•••A distances, as a function of D-H•••A angles, rather than one ‘radius’ for H and acceptor atoms. In Chapter VI, Detailed analysis and comparisons among hydrogen bond, chlorine bond and lithium bond, have been done. Hydrogen can be placed in group 1 as well as group 17 of the periodic table. Naturally, lithium bonding and halogen bonding have been proposed and investigated. There have been numerous investigations on the nature of hydrogen bonding and the physical forces contributing to it. In this Chapter, a total of one hundred complexes having H/Cl/Li bonding have been investigated using ab initio, AIM and NBO theoretical methods. Various criteria proposed in the literature have been examined. A new criterion has been proposed for the characterization of closed shell (ionic/electrostatic) and open shell (covalent) interactions. It has been well known that the D-H bond weakens on the D-H•••A hydrogen bond formation and H•••A bond acquires a fractional covalency. This Chapter shows that for D-Li•••A complexes, the ionicity in D-Li is reduced as the Li•••A bond is formed This comprehensive investigation of H/Cl/Li bonding has led us to propose a conservation of bond order, considering both ionic and covalent contributions to both D-X and X•••A bonds, where DX is the X-bond donor and A is the acceptor with X = H/Cl/Li. Hydrogen bond is well understood and its definition has been recently revised [Arunan et al. Pure Appl. Chem., Vol. 83, pp. 1619–1636, 2011]. It states “The X–H•••Y hydrogen bond angle tends toward 180° and should preferably be above 110°”. Using AIM theory and other methods, this fact is examined and presented in Appendix A. In second part of appendix A, a discussion about calling H3¯ complex as trihydrogen bond and its comparison with FHF¯ complex, is presented. In Appendix B, there is tentative prediction and discussion about the HFIP dimer. Condense phase studies show that HFIP have strong aggregation power to form dimer, trimer etc. During, HFIP monomer study, we have unassigned lines which are suspected to be from HFIP dimer. These are tabulated in the Appendix B as well.

No description available.

Les alpha oléfines linéaires courtes sont des molécules de base en pétrochimie donc le marché est en constante augmentation notamment pour les oléfines légères (butène-1, hexène-1, octène-1). Ces oléfines, utilisées massivement dans l’industrie des plastiques, sont produites par la réaction catalytique d’oligomerisation de l’éthylène. IFPEN a contribué à développer plusieurs procédés homogènes d’oligomérisation de l’éthylène (AlphaButol, AlphaHexol, AlphaSelect) à base des complexes de titane, chrome ou zirconium. A travers une collaboration avec l’Université d’Amsterdam de nouvelles stratégies de développement de ligands ont été entreprises afin de rendre les catalyseurs à base de nickel sélectifs pour cette transformation. Ainsi, une approche supramoléculaire basée sur des interactions par liaison hydrogène, jusqu’alors décrite pour les métaux nobles, a été développée et appliquée aux complexes de nickel. Des complexes organométalliques originaux ont pu être générés et les interactions supramoléculaires ont été caractérisées par diffraction aux rayons X notamment. Ces complexes se présentent sous forme zwitterionique et sont formés par la combinaison de deux ligands simples donneurs et/ou accepteurs d’hydrogène. Ces complexes se sont avérés très actifs vis-à-vis de l’éthylène et ne nécessite pas l’ajout d’activateur du fait de la présence d’une liaison nickel-carbone réactive. Ils ont permis d’accéder à des sélectivités très importantes en butène-1. Appuyé par des expériences in situ et l’évaluation en catalyse de plusieurs complexes aux propriétés électroniques et stériques variées, cette approche a permis d’identifier l’espèce active et de mesurer l’impact de plusieurs descripteurs permettant de moduler la sélectivité et l’activité de la réaction catalytique en profondeur. / The demand for short linear alpha olefins is constantly increasing and motivates the development of robust and selective catalysts. In this thesis, several libraries of phosphorus ligands with the capacity to form dissymmetric or supramolecular assemblies were synthesized. The variability observed within the aminophosphine libraries, clearly reflected by the various tautomeric equilibrium of the ligand, was also observed in the nickel complexes as a single ligand could generate several complexes with different structures. Sulphonyliminobisphosphine were then introduced as a new class of ligands. These precursors rearrange in the presence of nickel to generate diphosphinamine nickel complexes. Activated by MAO, these complexes are active in the reaction of ethylene oligomerisation and produce short chain olefins. A new approach that forms stable supramolecular nickel complexes was developed by combining two phosphorus ligands with Ni(0). These complexes stabilised by hydrogen bonding are directly active in the reaction of ethylene oligomerisation with some catalysts leading to high selectivity to 1-butene (up to 84%). To understand the origin of that selectivity, the scope of complexes was extended to ligands with different steric and electronic properties. Their evaluation in the reaction of ethylene oligomerisation evidenced a relation between the catalyst structure and the selectivity of the reaction. Mechanistic studies, under an ethylene atmosphere, reveals that cationic complexes rearrange to neutral complexes, which are likely, the active species.

Department of Chemistry / PhD (Chemistry) / This thesis is concerned with the computational study of naphthylisoquinoline alkaloids having antimalarial properties. The study was considered interesting because of the importance of gathering information on antimalarial molecules and because these molecules had not yet been studied computationally. The alkaloids considered in this study had been isolated from tropical lianas belonging to the Dioncophyllaceae and Ancistrodaceae families. They comprise alkaloids with both monomeric and dimeric structures. The monomeric structures consist of one unit and the dimeric ones of two units, with each unit containing a naphthalene moiety and an isoquinoline moiety. 33 monomeric molecules were studied, which represent a large portion of all the monomeric naphthylisoquinoline alkaloids isolated so far. Two dimeric molecules with antimalarial activity were investigated, namely, jozimine A2 and mbandakamine A. A third dimeric molecule, with a structure close to that of jozimine A2 but different activity (michellamine A, anti-HIV) was also calculated for comparison purposes. This work utilised electronic structures methods and involved the conformational study of all the molecules selected to identify the stabilising factors in vacuo and in solution. Two levels of theory (HF/ 6-31G (d,p) and DFT/B3LYP/ 6-31+G(d,p)) were utilised to compare their performance for compounds of this type, also in view of a future study extending to other compounds of the same class. The molecules were firstly studied in vacuo and secondly in three different solvents – chloroform, acetonitrile and water – characterized by different polarities and different H-bonding abilities. Quantum chemical calculations in solution were carried out using the Polarisable Continuum Model (PCM). The main stabilizing factors are the presence and types of intramolecular hydrogen bonds (IHBs), which are the dominant factors, and also the mutual orientation of the moieties. The possible IHBs comprise OH⋯O (or OH⋯N and NH⋯O for mbandakamine A) and other H-bond types interactions such as OH⋯ and CH⋯O (or CH⋯O and CH⋯N for mbandakamine A). The moieties prefer to be perpendicular one to another, which is a common tendency of aromatic vii systems. In monomeric structures, there may be only one OH⋯O and possibly also one of each of the other two types of IHBs interactions. In dimeric structures, there may be up to four (five in mbandakamine A) OH⋯O IHBs simultaneously and also other H-bond type interactions. The results provide a comprehensive picture of the molecular properties of these compounds, such as conformational preferences, dipole moments, HOMO-LUMO energy gaps, harmonic vibrational frequencies, solvent effect and influence of the solvent on molecular properties which respond to polarisation by the solvent. Altogether, these results may contribute to a better understanding of their biological activity and to the design of molecular structures with enhanced biological activity. This is the reason of focusing the efforts on the investigation of chemical and physical properties of these alkaloids molecules. / NRF

No description available.

The title compound, C20H18O3, crystallizes in the space group P21/c with one mol­ecule in the asymmetric unit of the cell. The fluorene skeleton is nearly planar and the crystal structure is composed of mol­ecular layers extending parallel to the (302) plane. Within a layer, one formyl oxygen atom participates in the formation of a Carene—H...O bond, which is responsible for the formation of an inversion symmetric supra­molecular motif of graph set R22(10). A second oxygen atom is involved in an intra­molecular Carene—H...O hydrogen bond and is further connected with a formyl hydrogen atom of an adjacent mol­ecule. A Hirshfeld surface analysis indicated that the most important contributions to the overall surface are from H...H (46.9%), O...H (27.9%) and C...H (17.8%) inter­actions.

In vorliegender Arbeit wurden Synthese, Kristallstruktur und thermisches Verhalten von sauren und basischen Monofluorophosphate untersucht. Es wurden Salze mit Alkalimetall- und N-haltigen Kationen dargestellt und kristallographisch charakterisiert. Die Strukturen dieser Verbindungen wurden dann mit denen der isoelektronischen Hydrogensulfate verglichen. Mit Hilfe des Kationenaustausches und der Gefriertrocknung konnte ein erfolgreicher Syntheseweg fuer diese Verbindungen entwickelt werden. Die Gefriertrocknung hinderte die Abspaltung von HF und Kondensation des Phosphats und ermöglichte die Isolierung der Rohprodukte. Auf diesem Weg gelang die Darstellung der reinen Verbindungen in höherer Ausbeute, so daß es möglich wurde, die Substanzen mit unterschiedlichen Methoden zu untersuchen. Hergestellt und kristallographisch untersucht wurden folgende Verbindungen: - Hydrogenmonofluorophosphate mit × Alkalimetallkationen: Na, K, Rb, Cs × N-haltigen Kationen: NH4, NMe4, NH2Et2, NHEt3, [C(NH2)3], {HOC[NH(CH3)]2}, [H2N(CH2CH2)NH2], - basische Monofluorophosphate: Na2PO3F·10H2O und [C(NH2)3]2PO3F - gemischte Salze: Cs3(NH4)2(HPO3F)3(PO3F)2 und Na5[NMe4](PO3F)3·18H2O. Die Kristallstrukturen zeigen eine Vielzahl an Strukturtypen, definiert durch die Verknüpfung der verzerrten HPO3F Tetraeder über kurze O-H···O Wasserstoffbrückenbindungen zu Ketten, Dimere oder Tetramere. Diese sind ihrerseits über längere N-H···O und Ow-H···O Wasserstoffbrückenbindungen verknüpft. Kompliziertere Strukturmotive sind in den Strukturen der basischen Monofluorophosphate und der gemischten Salze zu finden. Allgemein werden nur Wasserstoffbrückenbindungen des Typs N-H...O und O-H...O gefunden, dagegen werden keine N-H···F Bindungen in den Strukturen beobachtet. Auch ist mehrheitlich keine Isotypie zwischen sauren und basischen Monofluorophosphaten einerseits und den entsprechenden Sulfaten andererseits zu finden. Isotyp sind nur die Strukturen [NMe4]HPO3F·H2O mit [NMe4]HSO4·H2O und Na2PO3F·10H2O mit Na2SO4·10H2O. Interessanterweise wurden genau in einer dieser isotypen Strukturen, nämlich der des Na2PO3F×10H2O, als Ausnahme zwei O-H···F Bindungen gefunden. Die O···F Abstände liegen im Bereich der Abstände der Ow···O Bindungen in der Struktur. Eine Erklärung für das seltene Auftreten von H-Brücken mit Fluor als Akzeptor ist eine fast vollständige Valenz des Fluors durch seine Bindung zum Phosphor. Mehrere Strukturen widerspiegeln diese Tatsache mit der Orientierung der P-F Bindung. Die Bindung wird nach inerten Stellen, wo kein Metall- oder Wasserstoffatom in der Struktur vorhanden ist, ausgerichtet, um ein weiteres Binden des Fluors (Metallkoordination, Wasserstoffbrückenbindung) zu vermeiden. Weiterhin wurde das thermische Verhalten der Verbindungen NaHPO3F, NaHPO3F·2.5H2O, CsHPO3F und [NHEt3]HPO3F untersucht. Dies erfolgte mit dem Ziel, Information über mögliche Phasenübergänge und die unterschiedlichen Zersetzungstypen zu bekommen. Sowohl der Kation wie auch die Anwesenheit von Kristallwasser haben Einfluß auf den thermischen Abbau. Die Na-Verbindungen zeigen eine Zersetzung über mehrere Schritte, die zu unterschiedlichen Endprodukten führt (Na3P3O9 für NaHPO3F und (NaPO3)n für das Hydrat). Im Vergleich dazu zersetzt sich CsHPO3F nach dem Schmelzen direkt zum Endprodukt, ohne stabile Zwischenprodukte zu bilden. Ähnlich verläuft der thermische Abbau der [NHEt3] Verbindung, die sich allerdings mit einem Masseverlust von 92,27%, also ohne Bildung eines signifikanten Endproduktes, vollständig zersetzt. Während des thermischen Abbaus wurde die Freisetzung von HF und H2O bei allen Verbindungen beobachtet, die sich aber bezüglich der Zersetzungstemperatur und -menge zwischen den Substanzen unterscheiden. Es wurden keine Phasenübergänge erster Ordnung beobachtet. Dies war insbesondere für CsHPO3F überraschend, da das isoelektronische Hydrogensulfat mehrere Phasenübergänge aufweist [2]. Das Ausbleiben von Phasenübergängen allgemein und auch für CsHPO3F wird folgendermassen erklärt. Während das Sulfat Bindungsmöglichkeiten an allen vier Ecken des SO4-Tetraeders hat, besitzt der (H)PO3F-Tetraeder nur eine begrenzte Flexibilität wegen der Anwesenheit von Fluor an einer Ecke. Fluor bevorzugt eine "isolierte" Position am Phosphor. Anhand der vorliegenden Ergebnisse kann die Schlußfolgerung gezogen werden, daß Fluor auf Grund seiner niedrigeren Valenz im Vergleich zu Sauerstoff andere strukturelle und funktionelle Charakteristika aufweist. Die Valenzunterschiede zwischen Sauerstoff und Fluor haben einen starken Einfluß auf das Wasserstoffbrückenbindungssystem in den Kristallstrukturen der Hydrogenmonofluorophosphate und folglich auf die "Nicht-Isotypie" zu den Hydrogensulfaten. / In this thesis, the crystal structures and thermal behavior of hydrogen monofluorophosphates and basic monofluorophosphates with alkali metal and N-containing cations were studied. A comparison to the analogous hydrogen sulfates showed interesting structural variations and differences in thermal behavior. Synthesis of the studied monofluorophosphates involved cation exchange and freeze drying. Freeze drying enabled the isolation of raw products by avoiding the escape of HF and consequent phosphate condensation. This method of preparation led to the synthesis of the hydrogen monofluorophosphates with the following cations: - the alkali metals: Na+, K+, Rb+, and Cs+, - N-containing cations: NH4+, [NMe4]+, [NH2Et2]+, [NHEt3]+, [C(NH2)3]+, {HOC[NH(CH3)]2}+, and [H2N(CH2CH2)NH2]2+, and the basic monofluorophoshates, Na2PO3F·10H2O and [C(NH2)3]2PO3F. The following mixed salts were also obtained with partial cation exchange: - Cs3(NH4)2(HPO3F)3(PO3F)2 - Na5[NMe4](PO3F)3·18H2O. In the crystal structures, the HPO3F tetrahedra were hydrogen-bonded to chains, dimers, and tetramers in the structures of the hydrogen monofluorophosphates. Extensive hydrogen bonding in the basic monofluorophosphates due to high amounts of crystal water led to more complicated structural motifs. Limitations on the bonding of fluorine were observed in each of the structures, whether it be metal coordination or hydrogen bonding. The valency of fluorine is filled by its bond to phosphorus and thus, generally, the fluorine atom does not participate in additional bonds. This explains why, for the most part, the hydrogen monofluorophosphates are not isostructural with the hydrogen sulfates. Only three atoms of the tetrahedron instead of four atoms are available for hydrogen bonding, which influences the crystal structure. This was further confirmed by the comparison of the decahydrates, Na2PO3F×10H2O and Na2SO4×10H2O, which are consequently isostructural based on two O-H×××F bonds formed in Na2PO3F·10H2O. These were the only hydrogen bonds found that involved fluorine as an hydrogen acceptor or donor. The investigations on the thermal behavior of NaHPO3F, NaHPO3F·2.5H2O, CsHPO3F, and [NHEt3]HPO3F found no first-order phase transitions. Stepwise decompositions were observed for the sodium salts, which was attributed to the formation of stable intermediates identified with simulated experiments. The Cs and [NHEt3] compounds demonstrated a direct decomposition postmelting. In general, the release of H2O from the melt occured at lower temperatures, while HF escaped at higher temperatures. The temperatures, at which this initially occured, and the first maximum observed were dependent on the cation and the presence of crystal water. The immediate decomposition of CsHPO3F after melting differs from that of the hydrogen sulfate, CsHSO4, which undergoes several phase transitions before decompositon. This suggests that the sulfate has more structural flexibility on the basis of the four oxygen corners of the tetrahedra. In comparison, the monofluorophosphate is limited in its bonding mobility due to the presence of fluorine on one of the tetrahedral vertices. Therefore, phase transitions are not observed prior to decomposition. It was concluded that fluorine functions differently in the crystal structures on the basis of its lower valency. Thus, the difference in valency between fluorine and oxygen affects the hydrogen bonding of the hydrogen monofluorophosphates and thus pervents the expected isotypy of the isoelectronic hydrogen monofluorophosphates and hydrogen sulfates.

The crystal structures of the title compounds, methyl 3,5-di­methyl­benzoate (C10H12O2; 1), 3,5-bis­(bromo­meth­yl)phenyl acetate (C10H10Br2O2; 2) and 5-hy­droxy­benzene-1,3-dicarbaldehyde (C8H6O3; 3) were determined by single-crystal X-ray analysis. The crystals of 1 are composed of strands of C—H⋯O=C bonded mol­ecules, which are further arranged into layers. As a result of the presence of two bromo­methyl substituents in compound 2, mol­ecular dimers formed by crystallographically non-equivalent mol­ecules are connected to structurally different two-dimensional aggregates in which the bromine atoms participate in Br⋯Br bonds of type I and type II. In the case of compound 3, which possesses three donor/acceptor substituents, the mol­ecular association in the crystal creates a close three-dimensional network comprising Car­yl—H⋯Ohy­droxy, Cform­yl—H⋯Oform­yl and O—H⋯Oform­yl bonds.

La compréhension et le contrôle des interactions intermoléculaires est d'une importance fondamentale dans les domaines de la reconnaissance moléculaire et de l'ingénierie cristalline, ainsi que dans les systèmes biologiques. Parmi les contacts faibles les plus fréquents qui lient les molécules dans les solides organiques nous trouvons la liaison halogène, la liaison chalcogène, et la liaison hydrogène faible. Dans cette thèse, des études expérimentales et théoriques de densité de charge rhô(r) basées sur la méthodologie QTAIM ont été effectuées pour l'analyse des liaisons halogènes et chalcogènes, et pour leur comparaison avec les liaisons hydrogène faibles. Pour ce faire, nous avons réalisé l'affinement multipolaire de la densité électronique obtenue à partir de la diffraction des rayons-X sur monocristal, ainsi qu'à partir des calculs périodiques DFT. A l'issue de nos résultats, nous avons définie la nature de ces interactions faibles (électrophile-nucléophile) et caractérisé leur intensité et directionnalité. Basé sur la topologie de L(r) = ¬rhô delta inversé2 rhô(r), le descripteur électrostatique (delta(L/rhô)) nous a permis d'évaluer quantitativement l'interaction électrostatique entre les régions de concentration (CC) et de dilution (CD) de charge de la couche de valence des atomes. L'énergie d'interaction (Eint) a été décrite à partir de descripteurs topologiques de rhô(r). Nous nous sommes intéressés également à la formation de fragments structuraux récurrents, appelés synthons. Il a été prouvé que le synthon peut être créé non seulement par des groupements d'atomes similaires, mais aussi par des ensembles de sites CC et CD qui sont impliqués de façon similaire dans la formation de contact / Understanding and control of intermolecular interactions play a crucial role in molecular recognition, crystal engineering, and biological systems. Three very frequent weak contacts linking the molecules in organic solids are halogen, chalcogen, and weak hydrogen bondings. In this thesis, we perform experimental and theoretical charge density rho(r) studies based on the QTAIM methodology for analyzing halogen and chalcogen bonding, and for comparing them with weak hydrogen bonding, as derived from the high-resolution single crystal X-ray diffraction multipole-refined electron density and from density functional theory (DFT) calculations. Defining the nature of these weak interactions as electrophilic-nucleophilic, we particularly focus on their strength and directionality. Based on the topology of L(r) = ¬rho inverted delta2 rho(r), a proposed electrostatic descriptor (delta(L/rho)) permitted us to evaluate quantitatively the electrostatic intensity between charge concentration (CC) and charge depletion (CD) regions belonging to the valence shell of the interacting atoms. The interaction energy (Eint) was described from the topological properties of rho(r). The attention has been also paid to the formation of recurrent structural fragments, called synthons. By the developed approach, it is proved that the synthon arrangement can be created not only by groups of atoms, but also by sets of CC and CD sites similarly involved in the contact formation

Les nucléolipides sont des molécules amphiphiles dont la structure bio-inspirée dérive de celle des acides nucléiques. Leur auto-assemblage en milieu aqueux aboutit à la formation d’objets supramoléculaires de morphologies et structures très diverses. La morphologie a été caractérisée par des techniques complémentaires de microscopie optique et de diffusion de la lumière, tandis que leur structure a été déterminée par la diffusion des rayons X. Il a ainsi été mis en évidence l’existence et le rôle fondamental des interactions faibles entre têtes polaires, au sein des auto-assemblages. La nature de ces interactions faibles a été déterminée par des techniques de spectroscopies IR et UV. Un premier objectif a été de mettre en évidence l’importance de ces interactions, ainsi que leur corrélation avec d’autres facteurs qui régissent le mécanisme d’auto-assemblage, tels que la nature chimique des amphiphiles, ou la morphologie et la structure des objets supramoléculaires en présence.Par ailleurs, la tête polaire nucléotide permet également d’imaginer la formation d’interactions faibles entre les auto-assemblages et un monobrin d’acide nucléique, à l’image des interactions spécifiques entre bases azotées présentes dans l’ADN. Lors de ce travail, nous nous sommes intéressés à une méthode de vectorisation d’acides nucléiques par des objets eux aussi chargés négativement. Contrairement aux approches classiques, l’interaction électrostatique est ici défavorable et l’association repose alors uniquement sur des interactions faibles spécifiques, estimées en spectroscopie. De façon surprenante, la formation des complexes a pu être mise en évidence par des expériences de diffraction des rayons X et un modèle approprié a permis de proposer des mécanismes de formation des complexes. Les propriétés thermodynamiques des différents complexes formés ont été évaluées par la technique de Calorimétrie à Titration Isotherme (ITC). Un point remarquable a été la mise en évidence systématique de trois types de comportements sur l’ensemble des complexes étudiés en fonction de la nature et de la spécificité des interactions mises en jeu. Ceci nous a ainsi permis de proposer différents mécanismes de formation pour chaque type de complexe observé. / Nucleolipids are amphiphilic molecules which bio-inspired structure derives from nucleic acid structure. Their self-assembling behaviour in aqueous medium leads to the formation of supramolecular objects of very different morphologies and structures. The morphology has been characterized with optical microscopy and light scattering complementary techniques, whereas their structure has been determined with X-ray scattering. Thus the existence and the fondamental role of weak interactions between polar heads inside the self-assemblies have been highlighted. The nature of these weak interactions has been determined with IR and UV spectroscopies techniques. A first objectif has been to highlight the importance of these interactions, as well as the their correlation with other factors which drive the mechanism of self-assembly, such as the chemical nature of amphiphiles or the morphology and structure of the supramolecular objects.Moreover the nucleotide polar hear also allows to imagine the formation of weak interactions between the self-assemblies and a single-stranded nucleic acid, such as those highlighted in DNA. In this work, we found interest in a nucleic acid vectorisation method with negatively charged objects as well. On the contrary of classic approaches, electrostatic interaction was here defavorable and assembling relies only on specific weak interactions, estimated with spectroscopy methods. Surprisingly, complexes formation could be highlighted with X-ray scattering experiments, and an appropriate model has allowed the proposal of mechanisms for the formation of complexes. Thermodynamic properties of the different complexes formed have been evaluated with Isothermal Titration Calorimetry (ITC) technique. A remarkable point was the systematic highlighting of three types of behaviour on the whole set of complexes studied, depending of the nature and the specificity of the weak interactions implied. This led us to different proposals for the mechanism of formation of each type of complex studied.