Angewandte Frontispiece: Self-Assembly and (Hydro)gelation Triggered by Cooperative π–π and Unconventional C[BOND]H⋅⋅⋅X Hydrogen Bonding Interactions†
Angew. Chem. Int. Ed., 2014. Weak C[BOND]H⋅⋅⋅X hydrogen bonds are important stabilizing forces in crystal engineering and anion recognition in solution. In contrast, their quantitative influence on the stabilization of supramolecular polymers or gels has thus far remained unexplored. Herein, we report an oligophenyleneethynylene (OPE)-based amphiphilic PtII complex that forms supramolecular polymeric structures in aqueous and polar media driven by π–π and different weak C-H⋅⋅⋅X (X=Cl, O) interactions involving chlorine atoms attached to the PtII centers as well as oxygen atoms and polarized methylene groups belonging to the peripheral glycol chains. A collection of experimental techniques (UV/Vis, 1D and 2D NMR, DLS, AFM, SEM, and X-Ray diffraction) demonstrate that the interplay between different weak noncovalent interactions leads to the cooperative formation of self-assembled structures of high aspect ratio and gels in which the molecular arrangement is maintained in the crystalline state.
J. Am. Chem. Soc., 2013, 135, 2148-2151. A new oligophenyleneethynylene (OPE)-based Pd(II) pyridyl complex has been synthesized, and its self-assembly has been investigated in solution, in the bulk state, and on surfaces. Detailed analysis of concentration- and temperature-dependent UV–vis studies in methylcyclohexane supported by DFT calculations demonstrate for the first time that cooperative supramolecular polymerization processes can be driven by metallophilic interactions.
Narcissistic versus social! G. Fernández et al. report on the self-assembly of two structurally related oligophenyleneethynylene (OPE) derivatives featuring polar or nonpolar peripheral chains and their remarkable narcissistic versus social self-sorting behaviour in aqueous media that can be controlled by concentration and solvent changes. Between 0.01 and 0.1 mm the mixture of both OPEs self-assembles into independent spherical aggregates, whereas a slight increase in concentration to 1 mm induces a co-assembly process, giving rise to large ribbon-like aggregates.
Nature Materials. 2013, 12, 12-14. Three-dimensional ordering in liquid-crystalline polymers is induced by the photopolymerization of a mixture of mesogens sandwiched between two patterned substrates. By incorporating an infrared-sensitive dye in the mixture, polymer films that undergo reversible shape deformations on heating are formed.