Curved nanographene with five-, six- and seven-membered rings synthesized in two steps
Nanographenes can be considered molecular fragments of graphene, a 2D conductive material in which carbon atoms are connected in a honeycomb pattern. Because their electronic and photophysical properties vary depending on the size and shape of the molecule, nanographenes are expected to find applications in OLEDs, organic solar cells, organic field-effect transistors and more.
Researchers from WPI-ITbM at Nagoya University and RIKEN have developed a novel two-step annulative π-extension (APEX) method to synthesize diverse nanographenes featuring rare defects, including curvature, five- or seven-membered rings, and highly fused hexagonal structures. Nanographenes, molecular fragments of graphene, are 2D conductive materials with varying electronic and photophysical properties based on their size and shape.
The new APEX method involves using a palladium catalyst and ortho-chloranil to selectively extend particular PAHs (polycyclic aromatic hydrocarbons) at specific sites. The resulting polyaryl intermediates are then subjected to an oxidative cyclization reaction using dichloro-5,6-dicyano-p-benzoquinone (DDQ) and trifluoromethanesulfonic acid (TfOH) to create nanographenes with various frameworks, including 8–10 rings.
The researchers unexpectedly discovered a nanographene with fused five-, six-, and seven-membered rings exhibiting a highly curved structure with negative curvature and a 34.8° interplanar tilt. This two-step APEX method is efficient in synthesizing known frameworks and holds promise for discovering nonplanar nanographenes with diverse shapes and electronic properties.
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