Desolvation Induced Conformational Transition in a Cryptophane Host: Crystal To Crystal Transformation

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Chemistry

Background:

• Cryptophanes are known to adopt various conformations in solution and solid states.
• These conformational changes are influenced by factors like linker length, medium, and guest molecules.
• Understanding cryptophane conformational dynamics is crucial for designing host-guest systems.

Purpose of the Study:

• To synthesize and study a novel cyclotriguaiacylenes (CTG)-based cryptophane.
• To investigate the conformational behavior of the synthesized cryptophane in solution and solid states.
• To explore the role of guest molecules in inducing conformational changes and transformations.

Main Methods:

• Synthesis of a CTG-based cryptophane using click chemistry with three triazole linkers.
• Structural characterization in solution and solid state using spectroscopic and crystallographic techniques.
• Density functional theory (DFT) calculations to support experimental observations.

Main Results:

• The synthesized cryptophane exhibits two distinct conformations: out-out crown-crown (CC) and out-in CC.
• The out-in CC conformation was achieved through the slow release of trapped acetone molecules from the out-out CC form in the solid state.
• A single-crystal-to-single-crystal (SCSC) transformation was observed, transitioning from a larger volume out-out CC to a smaller volume out-in CC.

Conclusions:

• The CTG-based cryptophane demonstrates tunable conformational flexibility.
• Guest molecule release can trigger significant structural rearrangements, including SCSC transformations.
• This study provides insights into the design of responsive supramolecular materials based on cryptophane scaffolds.