1,3,5-2,4,6-Functionalized Benzene Molecular Cage: An Environmentally Responsive Scaffold that Supports Hierarchical...

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Chemical Engineering

Background:

• Stimulus-responsive scaffolds are crucial for hierarchical supramolecular ensembles.
• Functionalized benzene moieties are established building blocks for host molecules.
• The use of switchable benzene motifs in multi-component supramolecular structures is underexplored.

Purpose of the Study:

• To report a novel molecular cage (1) capable of reversible conformational changes.
• To investigate the pH-induced switching mechanism of the molecular cage.
• To demonstrate the use of this cage in constructing stimuli-responsive hierarchical superstructures.

Main Methods:

• Synthesis of a molecular cage (1) comprising a bent anthracene dimer (3) and 1,3,5-tris(aminomethyl)-2,4,6-triethylbenzene (2).
• Investigation of pH-induced isomerization of the functionalized benzene units within the cage.
• Characterization of the reversible opening and closing of the cage in solution and solid states.
• Formation and analysis of hierarchical superstructures, such as Russian doll-like complexes, using the cage.

Main Results:

• A molecular cage (1) was successfully synthesized and demonstrated reversible pH-triggered switching between open and closed states.
• The cage's conformational motion was observed in both solution and solid states.
• Stimuli-responsive hierarchical superstructures, including [K⊂18-crown-6⊂1]+ and [K⊂cryptand-222⊂1]+, were formed using the cage.
• The assembly and disassembly of these superstructures were controlled by the cage's open-to-closed state transition.

Conclusions:

• The study presents an innovative molecular cage that utilizes pH-triggered conformational motion for controlled assembly of hierarchical ensembles.
• This work highlights an unusual mechanism where molecular conformation changes dictate the formation and dissociation of complex supramolecular structures.
• The findings offer a new paradigm for designing switchable scaffolds in supramolecular chemistry and materials science.