Guest exchange through single crystal-single crystal transformations in a flexible hydrogen-bonded framework

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Crystallography

Background:

• Guanidinium (G) and 1,2,4,5-tetra(4-sulfonatophenyl)benzene (TSPB) form molecular frameworks.
• Previous GS frameworks lacked flexibility for guest molecule exchange in single crystals.

Purpose of the Study:

• To develop a flexible molecular framework for reversible guest molecule adsorption and exchange.
• To investigate single crystal-to-single crystal transformations (SCSCT) in hydrogen-bonded frameworks.
• To explore the synthesis of single crystalline inclusion compounds via guest exchange.

Main Methods:

• Single crystal X-ray diffraction to verify structural changes during guest exchange.
• Analysis of guest molecule diffusion rates and mechanisms within the framework channels.
• Synthesis of inclusion compounds through guest exchange in the intact framework.

Main Results:

• A new G4TSPB framework with three unique 1D channels was synthesized.
• The framework demonstrated reversible guest molecule adsorption/desorption via cyclic channel expansion/contraction.
• Fast guest exchange (diffusivities ~10^-6 cm^2 s^-1) was observed in all three channels, with distinct diffusion mechanisms.
• Single crystalline inclusion compounds were successfully synthesized through guest exchange, a method not achievable by direct crystallization.

Conclusions:

• The flexible G4TSPB framework enables dynamic channel modulation for guest molecule interactions.
• SCSCTs are feasible in this hydrogen-bonded framework, allowing for rapid guest exchange.
• This approach offers a novel route for synthesizing complex single crystalline inclusion compounds.