Sulfur[n]arenes: Synthesis and Solid-State Supramolecular Dimerization via Multiple Sulfur···Sulfur Interactions.

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Materials Science

Background:

• Controlling structural dimensionality is crucial for designing supramolecular assemblies with tunable properties.
• Sulfur-containing macrocycles offer unique structural and electronic characteristics.

Purpose of the Study:

• To synthesize and characterize novel macrocycles, termed "sulfur[n]arenes", containing multiple sulfur atoms.
• To investigate the self-assembly behavior and structural properties of these sulfur[n]arenes.
• To evaluate the impact of macrocyclization on photophysical properties, specifically fluorescence quantum yield.

Main Methods:

• Synthesis of a series of sulfur[n]arenes macrocycles.
• Single-crystal X-ray diffraction analysis to determine solid-state structures.
• Computational studies to understand molecular interactions and orientation.
• Photophysical measurements to determine fluorescence quantum yield.

Main Results:

• Successful synthesis of novel sulfur[n]arenes macrocycles.
• Demonstrated discrete self-assembly into dimer structures via cooperative σ-hole interactions (S···S).
• Identified stabilization of monomer orientation by alkyl chains, maximizing S···S interactions.
• Observed significant enhancement of fluorescence quantum yield (up to ΦFL = 0.88) upon macrocyclization.
• Attributed fluorescence enhancement to suppressed singlet-to-triplet intersystem crossing and nonradiative decay.

Conclusions:

• Sulfur[n]arenes represent a new class of macrocycles capable of controlled self-assembly.
• Cooperative σ-hole interactions between sulfur atoms drive the formation of discrete supramolecular structures.
• Macrocyclization of sulfur-containing units offers a strategy to enhance photophysical properties like fluorescence.