Biasing the Formation of Solution-Unstable Intermediates in Coordination Self-Assembly by Mechanochemistry

Area of Science:

• Supramolecular Chemistry
• Mechanochemistry
• Coordination Chemistry

Background:

• Coordination self-assembly pathways in solution are challenging to study due to reversible bonds and solvation effects.
• Transient and high-energy intermediates are typically difficult to isolate and characterize in solution.

Purpose of the Study:

• To investigate the use of ball-milling approaches for accessing and trapping transient self-assembly intermediates.
• To explore the potential of mechanochemistry in uncovering novel supramolecular structures and reactivity.

Main Methods:

• Ball-milling for solid-state synthesis.
• Solution-based characterization techniques including NMR spectroscopy, DOSY NMR, and ESI-MS.
• X-ray diffraction for structural elucidation.

Main Results:

• Successfully trapped highly aqueous-unstable intermediates, such as Pd3L11 and Pd6L14 (Fujita cage), and Pd2L22, Pd3L21, Pd4L22 (Mukherjee capsule) in solid-state.
• Characterized trapped intermediates using a combination of spectroscopic and diffraction methods.
• Demonstrated the feasibility of accessing unique chemical space via mechanochemistry.

Conclusions:

• Mechanochemistry provides a powerful alternative to solution-based methods for studying complex self-assembly processes.
• Solid-state trapping of intermediates expands the accessible chemical space in supramolecular chemistry.
• This work opens new avenues for designing and synthesizing novel coordination complexes and materials.