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Alcohol oxidation and self-assembly: the in situ oxidation of hydroxyl functional groups to quinone groups promotes the formation of enhanced hydrogen bonds and allows reorganization of the resulting supramolecular self-assemblies, which evolve from a weakly bound dense phase to a strongly bound nanoporous open structure (see picture).

Claudine Katan ‘s present address : CNRS UMR6082 FOTON, INSA de Rennes, 20 avenue des Buttes de Coësmes, CS 70839, 35708 RENNES cedex 7, FranceInternational audienceInteGriTy is a software package that performs topological analysis following the AIM (atoms in molecules) approach on electron densities given on three-dimensional grids. Tricubic interpolation is used to obtain the density, its gradient and the Hessian matrix at any required position. Critical points and integrated atomic properties have been derived from theoretical densities calculated for the compounds NaCl and TTF-(2,5)Cl(2)BQ (tetrathiafulvalene-2,5-dichlorobenzoquinone), thus covering the different kinds of chemical bonds: ionic, covalent, hydrogen bonds and other intermolecular contacts

The self-assemblies of half-halogenated ͑ZnPcCl 8 and ZnPcF 8 ͒ and nonhalogenated zinc phthalocyanine ͑ZnPc͒ molecules on an Ag͑111͒ surface are studied by means of a combined experimental and theoretical study. The experiments involve scanning tunneling microscopy ͑STM͒ and the theoretical study is based on the topology of electron density obtained from density-functional ͑DFT͒ calculations. STM experiments reveal different structures due to the presence or not of halogen atoms at the periphery of the molecule, but the main differences are observed comparing ZnPcCl 8 and ZnPcF 8 deposits. In the case of ZnPcCl 8 , some faults are found periodically at the end of a ripening process that are not observed in the case of ZnPcF 8 . DFT calculations on the corresponding 2D molecular networks show differences in the nature of the H¯F and H¯Cl hydrogen bonds but also differences in the equilibrium molecular lattice parameter. We demonstrate that the intermolecular interaction can be tuned by chemical substitution and that the substrate-imposed stress can have a significant influence on the molecular self-assembly.

Carbon atoms are always present in Fe-based materials, either as impurities even in high purity samples or as an intrinsic constituent in steels. Density Functional Theory calculations have been performed to study the interaction between C atoms and vacancies (V) in α-Fe. We find that the formation of VCn complexes is energetically favourable for n ≤ 3, with VC2 being the most stable one. The energy gain corresponding to the clustering reaction VCn-1 + C → VCn depends mainly on the strength of C-C covalent bonds. The vacancy diffusivity is shown to be significantly modified by the formation of vacancy-carbon complexes, exhibiting non-Arrhenius behaviour. Effective vacancy diffusion coefficients in α-Fe are calculated as a function of temperature and carbon content using a simplified thermodynamic model. The results are discussed in detail in the limiting case of excess of C with respect to vacancies.

[a] Supramolecular structures formed by the self-assembly of functional molecular building blocks are a promising class of materials for future technologies. [1][2][3] Hydrogen bonding is a key ingredient in their fabrication, as it provides high selectivity and directionality. Hydrogen bonding has recently been used to prepare both two-dimensional (2D) and linear nanostructures at surfaces by molecular beam epitaxy. [4][5][6][7][8] Herein, we show that molecular films can evolve with time into a close-packed arrangement induced by the activation of an original 2D hydrogen-bond network consisting of H···Cl bonds. Scanning tunneling microscopy (STM) experiments combined with density functional calculations were performed on chlorine-zincphthalocyanines (ZnPcCl 8 ; see Figure 1 for structure) adsorbed onto Ag(111). We demonstrate that the location of the chlorine atoms on the phenyl rings predetermines the final 2D molecular network.The adsorption of large, flat metal-phthalocyanine (MPc) molecules on both metallic and semiconductor surfaces is well documented. [9][10][11][12][13] For this class of molecules, self-assembly is governed by the subtle balance between molecule-molecule and molecule-surface interactions, which can be tuned by the modification of the surrounding atoms of the phthalocyanine. [14] A large variety of arrangements at surfaces, depending on the nature of the central atom and the surrounding atoms of the molecule, has been reported. Intermolecular interactions influence the way molecules organize themselves on top of a surface. They can either be electrostatic in nature, including both multipolar static and dynamical Van der Waals contributions, or arise from orbital overlapping, or both. ZnPcC 8 , which is obtained from the substitution of chlorine atoms for eight of the sixteen surrounding hydrogen atoms, was chosen because it is capable of organizing itself into compact molecular arrangements mainly governed by hydrogen bonds. Phthalocyanines are well-known electron acceptors and their interactions with a metallic surface result from partial charge transfer from the surface electronic states to the lowest unoccupied molecular orbital (LUMO) of p type.[15] Thus, depending on the strength of the overlapping, the symmetry of the host surface may, more or less, influence the way molecules adsorb and organize themselves on this surface. Because of its moderate reactivity and oxidation potential (that is, its electron-donor character), Ag metal seems a good choice as a substrate with little influence on the molecular arrangement, because of its low surface energy. Looking for minimal substrate-molecule interactions, Ag (111) Herein is presented a combined experimental and theoretical approach to the molecular packing of ZnPcCl 8 molecules deposited onto Ag(111) surfaces. STM was performed at room temperature, and theoretical calculations were based on density functional theory (DFT) within the framework of the projector-augmented wave (PAW) method.[16] The evolution of the three different 2D...

The self-assembly of benzene diboronic acid molecules on KCl(001) is investigated at room temperature by means of non-contact Atomic Force Microscopy. When depositing the molecules on the freshly cleaved surface, the molecules self-assemble into an extended twodimensional supramolecular phase driven by H-bonds. Theoretical calculations based on Density Functional Theory show that the cohesion energy of the structure yields almost 1 eV per molecule. In combination with high-resolution structural analysis of the molecular layer and theoretical calculations, it is inferred that the growth of the supramolecular phase is made possible owing to the conformational adaptation of the molecule at the surface, which strengthens the intermolecular H-bonds, while avoiding the intermolecular steric hindrance. This work is the first experimental evidence of an extended H-bonded supramolecular network grown on a bulk insulator at room temperature.