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Benzodiselenazoles are introduced for efficient anion binding and unprecedented non-covalent catalysis in the focal point of neutral selenium-based chalcogen-bond donors., The benzodiselenazoles (BDS) introduced in this report fulfill, for the first time, all the prerequisites for non-covalent high-precision chalcogen-bonding catalysis in the focal point of conformationally immobilized σ holes on strong selenium donors in a neutral scaffold. Rational bite-angle adjustment to the long Se–C bonds was the key for BDS design. For the unprecedented BDS motif, synthesis of 12 analogs from o-xylene, crystal structure, σ hole variation strategies, optoelectronic properties, theoretical and experimental anion binding as well as catalytic activity are reported. Chloride binding increases with the depth of the σ holes down to KD = 11 μM in THF. Catalytic activities follow the same trend and culminate in rate enhancements for transfer hydrogenation of quinolines beyond 100 000.

An empirical MM2 force-field was developed for the calculation of steric or strain energies of carbenium ions, and applied to the rationalization of the rates of solvolysis of bridgehead derivatives. The latter constitute a homogeneous series of model compounds for solvolysis, spanning a rate range of ca 20 log units. Their rate constants correlate with the calculated steric energy differences between bridgehead bromides and the corresponding carbenium ions. The rate constants of tertiary derivatives of general structure may similarly be rationalized in terms of strain changes, although the correlation exhibits more scatter than that for the bridgehead derivatives alone. In the bridgehead series, the relative free energies of activation for solvolysis correlate with the heterolytic bond dissociation energies D° (R+ - Br-) in the gas phase. However, this correlation breaks down when simple mono- and acyclic substrates are included. This is attributed in part to the proximity of the leaving group in the transition state of solvolysis, which stabilizes the developing positive charge at the cationic centre in comparison with the charge of the free ion. The significance of the force-field calculations with respect to the structure of bridgehead carbenium ions was tested by comparison of structural data obtained from ab initio calculations. The structures of cations suffering strong distortions owing to C-C hyperconjugation are poorly reproduced by the molecular mechanics calculations, the parameters of which are based on solvolytic reactivity and not on carbenium ions.

Ab initio RHF calculations with the 3–21G basis set have been carried out on cycloadditions of CF2 and CCl2 with ethylene. Although p-complex intermediates are predicted for both reactions at this level, MP2/3-21G calculations imply that there are no complexes in reactions of CCl2 or more reactive carbenes with ethylene or substituted alkenes. Nevertheless, negative activation energies can be observed, since ?G reaches a maximum due to the increase in —T?S for these bimolecular reactions. The apparent “entropy control” for reactive carbenes results from the rapid decrease in ?H. As the reactivity of the alkene increases, the transition state shifts to an earlier point on the free energy surface, where —T?S‡ is lower, but ?H‡ is higher than for less reactive alkenes. Model potentials are developed for ?H and —T?S which reproduce experimental behavior, without the assumption of intermediates.

The homo-l, 4 adduct obtained from difluorocarbene and bicyclo [2.2.1]hepta-2, 5-diene (1) was treated successively with HCl, FSO3H and SbF5 in SO2ClF at low temperature. The protic acids underwent electrophilic addition to the cyclopropane part of 1, giving the corresponding derivatives. However, in FSO3H at - 50°, protonation of the gem-difluoro grouping also occurred to give the 2-fluoro-6-fluorosulfonylbicyclo [3.2.1]oct-2-en-3-yl cation. The reaction of 1 with SbF5 at -78° led initially to the formation of the 2-fluorobicyclo [3.2.1 ]octa-2, 6-dien-4-yl cation, which rearranged to 4-fluorotricyclo [5.1.0.05,8]oct-3-en-2-yl cation at -40°. These rearrangements are discussed in the light of those expected for C8H8F square pyramidal cations.

The steric energy difference (Est) between tertiary carbenium ions (R+) and the corresponding alcohols has been calculated by MM2 for a series of tertiary nonbridgehead substrates and correlated with their rate of solvolytic reactivity. Satisfactory correlation is obtained, except for p-nitrobenzoates of highly congested substrates. The slope and intercept of the correlations remain almost unchanged if bridge-head substrates are included in the plot. However, the quality of the fit is better for bridgehead substrates alone.

Rigid p-octiphenyl rods were used to create helical tetrameric {pi}-stacks of blue, red-fluorescent naphthalene diimides that can span lipid bilayer membranes. In lipid vesicles containing quinone as electron acceptors and surrounded by ethylenediaminetetraacetic acid as hole acceptors, transmembrane proton gradients arose through quinone reduction upon excitation with visible light. Quantitative ultrafast and relatively long-lived charge separation was confirmed as the origin of photosynthetic activity by femtosecond fluorescence and transient absorption spectroscopy. Supramolecular self-organization was essential in that photoactivity was lost upon rod shortening (from p-octiphenyl to biphenyl) and chromophore expansion (from naphthalene diimide to perylene diimide). Ligand intercalation transformed the photoactive scaffolds into ion channels.

Les interactions non-covalentes telles que les liaisons hydrogène, les interactions π-π, les interactions cation/anion-π, les liaisons halogène sont à la base de la chimie supramoléculaire. Ces interactions ont permis la conception de nouveaux systèmes possédant des fonctions intéressantes dans des domaines variés comme l'électronique organique, le transport transmembranaire ou l'organocatalyse. Dans cette thèse, différents outils de la chimie computationnelle (DFT, dynamique moléculaire…) ont été utilisés pour évaluer la contribution des interactions non-covalentes assurant la cohésion et la fonction dans des systèmes bioorganiques. Ces modélisations ont permis de comprendre et d'expliquer les observations macroscopiques faites en laboratoire à l'aide des informations obtenues au niveau computationnel. Des modélisations concernant les possibles fonctions catalytiques de systèmes supramoléculaires faisant appel aux interactions de type anion-π ont également été réalisées. Les résultats issus de ces études théoriques pourront servir de base de travail pour les chimistes de synthèse quant à l'existence réelle de telles fonctions.