1609200-04-5Relevant articles and documents
H-aggregates of oligophenyleneethynylene (OPE)-BODIPY systems in water: Guest size-dependent encapsulation mechanism and co-aggregate morphology
Allampally, Naveen Kumar,Florian, Alexander,Mayoral, Maria Jose,Rest, Christina,Stepanenko, Vladimir,Fernandez, Gustavo
, p. 10669 - 10678 (2014)
The synthesis of a new oligophenyleneethynylene (OPE)-4,4-difluoro-4-bora- 3a,4a-diaza-s-indacene (BODIPY) bolaamphiphile 1 and its aqueous self-assembly are reported. Compound 1 forms H-type aggregates in aqueous and polar media, as demonstrated by UV/Vis and fluorescence experiments. Concentration-dependent 1H NMR studies in CD3CN reveal that the BODIPY units are arranged on top of each other into π-stacks with H-type excitonic coupling, as supported by ROESY NMR and theoretical calculations and visualized by Cryo-SEM studies. A detailed analysis of the spectral changes observed in temperature-dependent UV/Vis studies reveals that 1 self-assembles in a non-cooperative (isodesmic) fashion in water. The hydrophobic interior of these self-assembled structures can be exploited to encapsulate hydrophobic dyes, such as tetracene and anthracene. Both dyes absorb in a complementary region of the UV/Vis spectrum and are small enough to interact with the hydrophobic segments of 1. Temperature-dependent UV/Vis studies reveal that the spectral changes associated to the encapsulation mechanism of tetracene can be fitted to a Boltzmann function, and the initially flexible fibres of 1 rigidify upon guest addition. In contrast, the co-assembly of 1 and anthracene is a highly cooperative process, which suggests that a different class of (more-ordered) aggregates is formed. TEM and Cryo SEM imaging show the formation of uniform spherical nanoparticles, indicating that a subtle change in the guest molecular structure induces a significant change in the encapsulation mechanism and, consequently, the aggregate morphology. Dye encapsulation: We report the aqueous self-assembly of a new oligophenyleneethynylene (OPE)-BODIPY amphiphilic derivative into H-type aggregates and its ability to encapsulate hydrophobic guest molecules. Subtle changes in the guest size induce a dramatic change of the encapsulation mechanism. Addition of tetracene leads to the non-cooperative formation of stiff fibres, whereas co-assembly with anthracene is a highly cooperative process, leading to highly organized micellar assemblies.
Self-assembly and (hydro)gelation triggered by cooperative π-π And unconventional C-H×××X hydrogen bonding interactions
Rest, Christina,Mayoral, María José,Fucke, Katharina,Schellheimer, Jennifer,Stepanenko, Vladimir,Fernández, Gustavo
, p. 700 - 705 (2014/01/23)
Weak C-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. Growing hand in hand! Multiple unconventional C-H×××X (X=O, Cl) hydrogen-bonding interactions, assisted by π-π interactions, are strong enough to drive the cooperative formation of supramolecular polymers and gels in polar and aqueous media. The aggregates consolidate themselves in the crystals, as shown by combined studies in solution and crystalline state. Copyright
