Electronic communication and negative binding cooperativity in diborylated bithiophenes

Area of Science:

• Organometallic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Bifunctional organoboranes are valuable for constructing complex molecular architectures.
• Understanding electronic communication in conjugated systems is crucial for designing advanced materials.

Purpose of the Study:

• To synthesize and characterize novel bifunctional conjugated organoboranes with 2,2'-bithiophene linkers.
• To investigate the electronic communication between boron centers and cooperative effects in guest binding.
• To explore the influence of aryl substituents on electronic properties and Lewis acidity.

Main Methods:

• Synthesis of organoborane compounds (3, 4, 5).
• X-ray crystallography for structural analysis.
• Density Functional Theory (DFT) calculations.
• Electrochemical studies (cyclic voltammetry).
• Spectroscopic techniques (NMR, UV-Vis absorption and emission).

Main Results:

• Compounds 3, 4, and 5 were successfully synthesized.
• X-ray structures revealed significant electronic delocalization in the bithiophene linker.
• DFT calculations and spectroscopy indicated a smaller HOMO-LUMO gap for compound 4, correlating with its green luminescence.
• Cooperative binding of pyridine was observed, with the first pyridine molecule reducing the Lewis acidity of the second boron center.
• A significant electronic communication parameter (a) was quantified, showing stronger communication in the fluorinated derivative 4.

Conclusions:

• The synthesized bifunctional organoboranes exhibit tunable electronic properties and cooperative guest binding.
• The bithiophene linker facilitates electronic communication between the boron centers.
• Fluorinated aryl substituents enhance Lewis acidity and electronic communication, impacting luminescence and binding behavior.