Symmetry-breaking host–guest assembly in a hydrogen-bonded supramolecular system

Abstract

Bio-inspired self-assembly is invaluable to create well-defined giant structures from small molecular units. Owing to a large entropy loss in the self-assembly process, highly symmetric structures are typically obtained as thermodynamic products while formation of low symmetric assemblies is still challenging. In this study, we report the symmetry-breaking self-assembly of a defined C1-symmetric supramolecular structure from an Oh-symmetric hydrogen-bonded resorcin[4]arene capsule and C2-symmetric cationic bis-cyclometalated Ir complexes, carrying sterically demanding tertiary butyl (tBu) groups, on the basis of synergistic effects of weak binding forces. The flexible capsule framework shows a large structural change upon guest binding to form a distorted resorcin[4]arene hexameric capsule, providing an asymmetric cavity. Location of the chiral guest inside the anisotropic environment leads to modulation of its Electric Dipole (ED) and Magnetic Dipole (MD) transition moments in the excited state, causing an increased emission quantum yield, longer emission lifetime, and enhancement of the dissymmetry factor (glum) in the circularly polarized luminescence.

Host–Guest Interactions of Zirconium-Based Metal–Organic Framework with Ionic Liquid

“…The anion contains sulfur and fluorine, which have a similar charge distribution electronegative property as the hydroxyl group from the organic linker, which can provide strong electrostatic forces. The oxygen from the [TFSI] − anion displays strong intermolecular forces with the hydroxyl part of the organic linker, causing an orientation twist with an intermolecular distance of 1.74784 Å, which corresponds to strong hydrogen bonding [ 42 , 43 ].…”

Noncovalent tailoring of coordination complexes by resorcin[4]arene-based supramolecular hosts

“…13). 65 The NMR studies proved that all resorcin[4]arene units were fixed in a non-equivalent environment around the Ir III complex guest in the NMR time scale, forming a defined C 1 symmetric host–guest complex (Fig. 13b).…”

“…15b). 65 Interestingly, the X-ray structure showed that the stoichiometry of the inclusion complex was a 3 : 1 host–guest complex, which was far different from the solution state. The trimeric capsule structure was stabilized by multiple hydrogen-bonding networks among the counter anions of the metal complex, solvent molecules, and hydroxy groups in the resorcin[4]arene units.…”

Redox‐Modulated Circularly Polarized Luminescence in Chiral Photonic Films Derived from Cellulose Nanocrystals and Polyoxometalate

“…Self-assembly has been proved to be a powerful strategy for precisely controlling the arrangement of building blocks and amplifying the g lum . [21][22][23][24][25][26] Chiral nematic liquid crystals (NLCs) as a typical 1D chiral photonic crystals (CPCs) of helical structures have been recognized as powerful platforms to generate CPL. [27] For instance, in our previous work, we achieved tunable CPL with a large |g lum | value up to 0.25 through the coassembly of inorganic nanowires and quantum dots into CPCs via Langmuir-Schaefer technique.…”