BN-Embedded Polycyclic Aromatic Hydrocarbon Oligomers: Synthesis, Aromaticity, and Reactivity

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are fundamental building blocks in organic electronics.
• Incorporating heteroatoms like boron and nitrogen into PAHs can tune their electronic and photophysical properties.
• Developing novel BN-embedded PAHs with controllable structures and functionalities is crucial for advanced materials.

Purpose of the Study:

• To synthesize and characterize BN-embedded oligomers with varying numbers of BN units within large PAHs.
• To investigate the impact of BN incorporation on the geometric, photophysical, electrochemical, and Lewis acidic properties.
• To understand the electronic structure and reactivity of these novel BN-containing aromatic systems.

Main Methods:

• Electrophilic borylation for synthesizing BN-embedded oligomers.
• X-ray crystallography for determining molecular geometry.
• Optical spectroscopy and cyclic voltammetry for investigating photophysical and electrochemical properties.
• Computational calculations to analyze electronic structure and aromaticity.

Main Results:

• Successful synthesis of BN-embedded PAH oligomers with up to four BN units.
• B-N bonds exhibit delocalized double-bond characteristics, extending conjugation through trans-oriented azaborine units.
• Calculations show reduced aromaticity in inner azaborine rings, with frontier orbitals delocalized over these inner regions.
• Inner moieties of BN-embedded PAH oligomers demonstrate higher reactivity compared to outer parts, confirmed by oxidation studies.

Conclusions:

• BN-embedded PAH oligomers represent a new class of functional organic materials.
• The electronic properties and reactivity are tunable by controlling the number and position of BN units.
• These findings offer insights into the structure-property relationships of BN-containing aromatic systems for potential applications in organic electronics.