The Halogen Bond to Ethers - Prototypic Molecules and Experimental Electron Density

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Crystallography

Background:

• Halogen bonding interactions involving dialkyl ethers are not well understood.
• Ethers are common organic molecules with potential as halogen bond acceptors.

Purpose of the Study:

• To synthesize and characterize the first halogen-bonded noncyclic alkyl ethers.
• To investigate the structural motifs and electronic properties of these novel halogen-bonded systems.

Main Methods:

• Synthesis of halogen-bonded complexes using 1,4-diiodotetrafluorobenzene and various ethers.
• Crystallization experiments to control stoichiometry and obtain different structural motifs.
• High-resolution X-ray diffraction to analyze the electronic details of halogen bonds.

Main Results:

• Two distinct structural motifs were obtained: discrete trimolecular aggregates and oxygen-bifurcated halogen-bonded supramolecular chains.
• Selective formation of these structures was achieved by adjusting stoichiometry.
• X-ray diffraction revealed the electrostatic nature of the interactions and the flexibility of the ether oxygen center.

Conclusions:

• Ethers exhibit remarkable versatility as halogen bond acceptors, forming diverse structural arrangements.
• The electronic properties and flexibility of ethers contribute to their role in halogen bonding.
• These findings highlight the underestimated importance of ethers in supramolecular chemistry and natural structural designs.