Conductive Organic Molecules Research Background
Nanographenes are organic semiconductor materials used in smartphones, OLED displays, and solar cells. At the molecular level, they are composed of polycyclic aromatic hydrocarbons (PAHs) which are a network of connected benzene rings (hexagon-shaped carbon molecules). Chemists can modify the electronic properties of PAHs by adding more benzene rings to them, changing their size and shape. As such, there is high demand for methods that can selectively extend specific sites of PAH molecules to allow greater versatility in technological applications.
Depending on their size, the peripheral regions of the PAH skeletons can be categorized as K, M, L, bay, and fissure regions. Previously, researchers from Nagoya University developed the Annulative π-Extension (APEX) reaction that transforms small PAHs into larger PAHs and nanographenes by extending these regions. While APEX reactions have developed to selectively extend each region of PAHs, the L-region is the last frontier and continues to elucidate researchers. Recently, however, a research group including Kanami Nakata (a graduate student), Associate Professor Hideto Ito of the Graduate School of Science at Nagoya University, and Principal Investigator Kenichiro Itami of RIKEN and WPI-ITbM at Nagoya University has reported an L-APEX reaction methodology that selectively targets the L-region in PAHs. This research was published in the journal Chemical Science on January 29, 2026.
How the Chemical Reaction Works
APEX reactions provide chemists the means of creating larger PAH structures and new nanographenes as if they were building blocks. However, the L-region in PAHs is intrinsically more stable and difficult to react selectively. Nonetheless, the L-APEX reaction was made possible by modifying a known M-APEX reaction ( W. Matsuoka et al., Nature Communications , 2021, 12, 3940 ). The M-APEX reaction proceeds by first breaking the aromaticity of the PAH ring, making it more reactive, followed by an iron-catalyzed diarylation with a Grignard reagent at the M-region. The L-APEX reaction also proceeds with initial de-aromatization but is instead followed by a palladium catalyzed a-allylic substitution and a subsequent intramolecular substitution and re-aromatization selectively at the L-region.
The L-APEX reaction proceeds over 3-steps that can performed in one-pot with 45% yield without detectable side-products from other APEX reactions. Additionally, the researchers demonstrated that the reaction can be followed by another L-APEX reaction or a K-APEX reaction, creating large and intricate PAH structures. With this new reaction methodology in hand, it is expected that researchers will be able to generate a greater variety of nanographene technologies.
Chemical Science
Experimental study
L-region-selective annulative π-extension through dearomative activation of polycyclic aromatic hydrocarbons
29-Jan-2026