Mechanochemically Triggered Topology Changes in Expanded Porphyrins.

Area of Science:

• Supramolecular Chemistry
• Chemical Physics
• Materials Science

Background:

• Expanded porphyrins represent a novel class of molecules for molecular force probe applications.
• Their potential as conformational mechanophores has remained largely unexplored.

Purpose of the Study:

• To investigate the mechanical responsiveness of [28]hexaphyrin.
• To establish expanded porphyrins as viable conformational mechanophores operating under mild force conditions.

Main Methods:

• Utilized a straightforward approach based on distance matrices to select pulling scenarios.
• Performed quantum mechanochemical calculations to support proposed methods.
• Conducted force distribution analyses to understand energy allocation within the molecule.

Main Results:

• Demonstrated that mechanical force effectively triggers Hückel-Möbius topology interconversions in [28]hexaphyrin.
• Identified specific pulling scenarios that favor either Hückel or Möbius topologies.
• Showed that [28]hexaphyrin selectively allocates mechanical energy to trigger these topological changes.
• Found that meso-substitution patterns influence the mechanical activation of topology interconversions.

Conclusions:

• [28]hexaphyrin functions as a conformational mechanophore under sub-1 nN force conditions.
• The proposed distance matrix approach aids in designing experiments for controlling topology.
• Meso-substitution is a critical factor in tuning the mechanical response of these expanded porphyrins.