Propeller, Linear, Cruciform and Stellate Spiro-bicarbazolium Salts

Area of Science:

• Organic Chemistry
• Materials Science
• Crystallography

Background:

• Tetraaryl-ammonium salts are important organic compounds.
• Developing efficient synthetic routes is crucial for their application.
• Spiro-bicarbazolium derivatives offer unique structural properties.

Purpose of the Study:

• To develop a general synthetic approach for halogenated tetraaryl-ammonium salts.
• To synthesize and characterize enantiopure spiro-bicarbazolium derivatives.
• To explore the potential of these compounds as building blocks for metal-organic frameworks (MOFs).

Main Methods:

• Utilized bromide ammonium salts as synthetic intermediates.
• Employed Suzuki coupling for arylation reactions.
• Applied X-ray crystallography for structural determination.
• Used electronic circular dichroism (ECD) spectroscopy for absolute configuration assignment.

Main Results:

• Established a general synthetic strategy for halogenated tetraaryl-ammonium salts.
• Achieved the first resolution of C2-symmetric spiro-bicarbazolium derivatives into enantiopure forms.
• Confirmed absolute configurations using computational and experimental ECD, and anomalous scattering.
• Identified cruciform and stellate tetra-substituted salts as potential MOF building blocks.

Conclusions:

• The developed synthetic methodology is versatile and efficient.
• Enantiopure spiro-bicarbazoliums are accessible through this approach.
• The synthesized salts show promise for applications in materials science, particularly as MOF components.