Why a hexabromodiquinoline host preferentially includes small aromatic hydrocarbon guests.

Area of Science:

• Supramolecular Chemistry
• Crystal Engineering
• Organic Chemistry

Background:

• Lattice inclusion hosts are crucial for molecular recognition and separation.
• Understanding host-guest interactions is key to designing efficient inclusion compounds.
• Hexabromodiquinoline derivatives offer potential as novel host materials.

Purpose of the Study:

• To synthesize and characterize a new hexabromodiquinoline derivative (4).
• To investigate the host-guest properties of derivative 4 with small aromatic hydrocarbons.
• To analyze the crystal structures and packing interactions of the inclusion compounds.

Main Methods:

• Synthesis of hexabromodiquinoline derivative 4.
• Crystallization of derivative 4 with benzene, toluene, o-xylene, and p-xylene.
• X-ray crystallography to determine crystal structures.
• Analysis of intermolecular interactions (Br...Br, OFF, EF, PHD) and lattice packing energies.

Main Results:

• Derivative 4 effectively traps small aromatic hydrocarbons (benzene, toluene, xylenes).
• Crystal structures reveal a shift from Br...Br interactions to aromatic interactions (OFF, EF) upon guest inclusion.
• Toluene, o-xylene, and p-xylene form 1:1 host-guest complexes.
• Benzene forms a 2:3 host-guest complex, facilitated by pi-halogen dimer (PHD) interactions.

Conclusions:

• The hexabromodiquinoline derivative 4 is a selective host for aromatic hydrocarbons.
• Intermolecular interactions play a critical role in determining host-guest stoichiometry and lattice packing.
• The observed changes in interactions lead to optimized lattice packing energies, particularly for the benzene inclusion compound.