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We report on a dendronized bis‐urea macrocycle1self‐assembling via a cooperative mechanism into two‐dimensional (2D) nanosheets formed solely by alternated urea‐urea hydrogen bonding interactions. The pure macrocycle self‐assembles in bulk into one‐dimensional liquid‐crystalline columnar phases. In contrast, its self‐assembly mode drastically changes in CHCl₃or tetrachloroethane, leading to 2D hydrogen‐bonded networks. Theoretical calculations, complemented by previously reported crystalline structures, indicate that the 2D assembly is formed by a brick‐like hydrogen bonding pattern between bis‐urea macrocycles. This assembly is promoted by the swelling of the trisdodecyloxyphenyl groups upon solvation, which frustrates, due to steric effects, the formation of the thermodynamically more stable columnar macrocycle stacks. This work proposes a new design strategy to access 2D supramolecular polymers by means of a single non‐covalent interaction motif, which is of great interest for materials development.

 

We report on a dendronized bis‐urea macrocycle1self‐assembling via a cooperative mechanism into two‐dimensional (2D) nanosheets formed solely by alternated urea‐urea hydrogen bonding interactions. The pure macrocycle self‐assembles in bulk into one‐dimensional liquid‐crystalline columnar phases. In contrast, its self‐assembly mode drastically changes in CHCl₃or tetrachloroethane, leading to 2D hydrogen‐bonded networks. Theoretical calculations, complemented by previously reported crystalline structures, indicate that the 2D assembly is formed by a brick‐like hydrogen bonding pattern between bis‐urea macrocycles. This assembly is promoted by the swelling of the trisdodecyloxyphenyl groups upon solvation, which frustrates, due to steric effects, the formation of the thermodynamically more stable columnar macrocycle stacks. This work proposes a new design strategy to access 2D supramolecular polymers by means of a single non‐covalent interaction motif, which is of great interest for materials development.

 

Absorption of electronic acceptors in the accessible channels of an assembled triphenylamine (TPA) bis -urea macrocycle 1 enabled the study of electron transfer from the walls of the TPA framework to the encapsulated guests. The TPA host is isoskeletal in all host–guest structures analyzed with guests 2,1,3-benzothiadiazole, 2,5-dichlorobenzoquinone and I 2 loading in single-crystal-to-single-crystal transformations. Analysis of the crystal structures highlights how the spatial proximity and orientation of the TPA host and the entrapped guests influence their resulting photophysical properties and allow direct comparison of the different donor–acceptor complexes. Diffuse reflectance spectroscopy shows that upon complex formation 1·2,5-dichlorobenzoquinone exhibits a charge transfer (CT) transition. Whereas, the 1·2,1,3-benzothiadiazole complex undergoes a photoinduced electron transfer (PET) upon irradiation with 365 nm LEDs. The CT absorptions were also identified with the aid of time dependent density functional theory (TD-DFT) calculations. Cyclic voltammetry experiments show that 2,1,3-benzothiadiazole undergoes reversible reduction within the host–guest complex. Moreover, the optical band gaps of the host 1·2,5-dichlorobenzoquinone (1.66 eV), and host 1·2,1,3-benzothiadiazole (2.15 eV) complexes are significantly smaller as compared to the free host 1 material (3.19 eV). Overall, understanding this supramolecular electron transfer strategy should pave the way towards designing lower band gap inclusion complexes. 

Herein, we probe the hydrogen bond‐driven self‐assembly of a triphenylamine (TPA) bis‐urea macrocycle in the presence and absence of guests. Comprised of methylene urea‐bridged TPAs with exterior tridodecyloxy benzene solubilizing groups, the macrocycle exhibits concentration‐dependent aggregate formation in THF and H₂O/THF mixtures as characterized by¹H NMR and DOSY experiments. Its assembly processes were further probed by temperature‐dependent UV/Vis and fluorescence spectroscopy. Upon heating, UV/Vis spectra exhibit a hypsochromic shift in the λ_max, while fluorescence spectra show an increase in emission intensity. Conversely, the protected macrocycle that lacks hydrogen bond donors demonstrates no significant change. Thermodynamic analysis indicates a cooperative self‐assembly pathway with distinct nucleation and elongation regimes. The morphology and structure of the aggregate were elucidated by dynamic light scattering, atomic force microscopy, scanning and transmission electron microscopy. Variable temperature emission spectra were utilized to monitor the impact of guests, such as diphenylacetylene, that can be bound in the columnar channels. The findings suggest that the elongation of assemblies is influenced by the presence of these guests. In comparison, diphenyl sulfoxide, likely functioning as a chain stopper, limited the assembly size. These studies suggest that judicious selection of (co)monomers may modulate the function and utility of these supramolecular systems.