Efficient and Selective Construction of 4₁ ² Metalla-links Using Weak C-H⋅⋅⋅Halogen Interactions

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Coordination-driven self-assembly is a powerful strategy for constructing complex molecular architectures.
• Understanding the role of substituents and non-covalent interactions is crucial for controlling self-assembly outcomes.

Purpose of the Study:

• To synthesize novel metallacycles with high selectivity and yield.
• To investigate the influence of halogen substituents on the formation of metallacycles.
• To study the dynamic interconversion between different metallacycle structures.

Main Methods:

• Coordination-driven self-assembly using adjusted building blocks.
• X-ray crystallographic analysis for structural determination.
• Electrospray ionization-time-of-flight/mass spectrometry (ESI-TOF/MS) for molecular weight confirmation.
• Elemental analysis for composition verification.
• Solution-state nuclear magnetic resonance (NMR) spectroscopy for structural and dynamic studies.

Main Results:

• Successfully synthesized four metallacycles and one tetranuclear monocycle with high selectivity and yield.
• Identified halogen substituents (F, Cl, Br, I) as key factors promoting metallacycle formation via weak C-H···X interactions.
• Demonstrated the dynamic conversion of metallacycles to monocyclic structures in methanol solution using quantitative 1H NMR.

Conclusions:

• The judicious choice of building block substituents, particularly halogens, enables precise control over the self-assembly of metallacycles.
• Weak halogen interactions play a significant role in stabilizing the desired metallacycle structures.
• The synthesized metallacycles exhibit dynamic behavior, allowing for interconversion between different structural motifs.