Selenium-induced curvature control enables polymorphism in borabuckybowls

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Organic Chemistry

Background:

• Selenium, a heavier sulfur congener, exhibits unique reactivity and bonding due to its larger atomic radius and polarizability.
• The structural implications of selenium incorporation in curved π-conjugated systems, particularly for molecular geometry and conformational adaptability, are underexplored.
• Tuning solid-state properties of curved π-conjugated systems is crucial for advanced materials applications.

Purpose of the Study:

• To investigate the impact of selenium incorporation on the molecular geometry and conformational adaptability of borabuckybowls.
• To explore the resulting solid-state properties, including polymorphism and redox stability.
• To establish sulfur-to-selenium substitution as a strategy for controlling molecular and material characteristics.

Main Methods:

• Synthesis of a selenium-embedded borabuckybowl with shallow bowl geometry.
• Crystallization studies to identify and characterize distinct polymorphs.
• Differential scanning calorimetry (DSC) to analyze thermodynamic differences among polymorphs.
• Computational investigations of crystal polymorphism's influence on charge-transport properties.
• Iodine (I2) doping and single-crystal electrical conductivity measurements.

Main Results:

• The selenium-embedded borabuckybowl exhibited enhanced shape adaptability and shallow bowl geometry.
• Three distinct polymorphs were identified, demonstrating temperature-dependent crystallization.
• Differential scanning calorimetry revealed significant enthalpic and entropic contributions to the thermodynamic differences between polymorphs.
• Computational studies correlated crystal polymorphism with microscopic charge-transport properties.
• Stable single crystals suitable for conductivity measurements were formed under iodine doping.

Conclusions:

• Selenium incorporation effectively enhances the conformational adaptability and redox stability of curved π-conjugated molecules.
• The strategy of sulfur-to-selenium substitution provides a powerful tool for controlling molecular shape and tuning solid-state properties.
• This work opens avenues for designing novel materials with tailored electronic and structural characteristics.