A research team at UNIST has developed a synthesis method to continuously insert boron-oxygen bonds into the edges of the carbon framework of the organic semiconductor pentacene. Unlike conventional methods that attach functional groups to the outside of the molecule, this method is characterized by its ability to control the atomic arrangement of the framework itself.

A research team led by Professors Young-Seok Park and Seung-Kyu Min of the Department of Chemistry at UNIST announced the results of the study on the 18th. The research results were published online on April 16 in the international chemistry journal Angewandte Chemie International Edition.

Pentacene is an organic semiconductor material consisting of five benzene rings connected in a linear fashion. Due to its excellent charge transport properties, it has been utilized in research on organic transistors, sensors, solar cells, and light-emitting materials. However, existing organic semiconductor research has focused on attaching functional groups to the outside of a carbon-based framework or controlling side branches, and there have been limitations in stably inserting desired elements into the framework.

The research team configured the reaction of introducing an iodine atom at a specific location, the binding of a boron reagent, and the cyclization reaction into a single cycle. The explanation is that repeating this cycle allows for the stepwise expansion of the benzene ring and the continuous insertion of boron-oxygen bonds into the edges of pentacene.

Using this method, the research team synthesized three types of pentacene derivatives with different boron-oxygen bonding positions. The three materials had different wavelengths of light absorbed or emitted, and their fluorescence quantum yields were all above 0.70. Fluorescence quantum yield refers to the efficiency with which a material re-emits light it has absorbed.

The research team explained that this synthesis method has the potential to be utilized in fields such as luminescent organic semiconductors, fluorescent sensors, and optoelectronic materials that require high luminescence efficiency. They also highlighted the ability to control molecular length and bond arrangement through repetitive synthesis as a key feature.

Professor Park Young-seok stated, “We have presented a method to synthesize new acene derivatives with continuous boron-oxygen bonds in a stepwise manner,” adding, “This will broaden the chemical diversity of organic semiconductor molecules and contribute to design and synthesis research.”