This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Nanographenes with up to eight helicene units can now be selectively synthesized using a two-step process. Researchers from Science Tokyo have developed a strategy to synthesize multi-helical nanographenes containing up to eight helicene units with controlled handedness.
Using a step-by-step process comprising [2+2+2] cycloaddition and the Scholl reaction, the strategy enables selective construction of complex chiral structures with tunable optical properties, including efficient near-infrared emission, offering potential applications in advanced chiroptical materials and optoelectronic devices. Nanographenes, built from fused aromatic rings arranged in two-dimensional networks, are promising carbon-based materials for next-generation optoelectronic applications. Their extended rigid networks of fused aromatic rings support efficient charge transport and offer high chemical and thermal stability.
However, their planar structures also encourage molecular aggregation, which reduces their solubility in organic solvents and can limit their practical applications. A promising approach to overcome these limitations involves incorporating helicenes, molecules with helical arrangements of fused aromatic rings, along the edges of nanographenes. These helical units can improve solubility while introducing helical chirality and distinctive chiroptical properties, including the ability to interact differently with left- and right-circularly polarized light.
However, incorporating multiple helicenes creates numerous possible stereoisomers, making it challenging to obtain molecules with uniformly aligned helicities without laborious separation procedures. In an effort to overcome these challenges, a research team at the Institute of Science Tokyo (Science Tokyo), Japan, has developed a highly stereoselective strategy for synthesizing multi-helical nanographenes containing up to eight helicene units. The team comprises graduate student Ryota Shimizu, Assistant Professor Juntaro Nogami, Dr.
Futo Morita (a graduate student at the time of the research, now at Kyoto University), Associate Professor Chihiro Maeda and Professor Ken Tanaka from the Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Science Tokyo, together with graduate student Yuko Kishida and Professor Hidehiro Uekusa from the Department of Chemistry, School of Science, Science Tokyo. Their study, published online in the journal Nature Synthesis, demonstrates a method for controlling the three-dimensional arrangement and handedness of these complex molecular structures. "Highly selective synthesis of nanographene molecules incorporating up to eight helicene units has been achieved.
This advancement addresses a longstanding challenge in constructing complex chiral nanomaterials with precisely controlled helicity," says Shimizu. The researchers combined two key reactions: an enantioselective [2+2+2] cycloaddition and a subsequent diastereoselective Scholl reaction. The first reaction establishes the initial helical framework and regulates the formation and handedness of additional helicene units, while the second reaction creates new carbon–carbon bonds through oxidative ring fusion, extending the nanographene structure.
Extract — continue reading at the source.
