Main research achievements to date

Main research achievements to date

Programmed chemical synthesis and rapid synthesis catalysts

　During the tenure as an assistant professor at Kyoto University, Itami introduced the concept of programmable molecule construction and devised innovative methods, such as the removable directing group strategy.[1] Focusing primarily on challenging substrates like multisubstituted olefins and extended π-electron systems, which lacked a general, flexible synthesis method, our group successfully demonstrated diversity-oriented synthesis and programmed synthesis. Outcomes included a library of full-color fluorescent molecules and anti-cancer drug candidates, with six compounds developed at Kyoto University reaching commercialization.

 

Inception of molecular nanocarbon science

　Nanocarbons, represented by fullerenes, carbon nanotubes, and graphene, have revolutionized material science. However, two major unresolved problems exist in this field. Firstly, current synthesis methods do not allow the production of structurally pure carbon nanotubes and graphene. Secondly, numerous nanocarbons with novel structures have only been proposed theoretically. Therefore, the key to advancing materials science lies in the development of synthetic chemistry capable of providing structurally pure or entirely new nanocarbons. Aiming to freely synthesize, utilize, and understand nanocarbons as structurally pure molecules, we pioneered the field of “molecular nanocarbon science” rooted in organic chemistry and synthetic chemistry, exploring the challenges faced by nanocarbon science. We have provided clear solutions to the “mixture problem” and “unsynthesized problem.”[2]

Synthesis of carbon nanorings and nanobelts　

　In 2005, we embarked on a groundbreaking quest to synthesize the world’s first carbon nanorings and carbon nanobelts, regarded as structurally pure forms of carbon nanotubes. These targets had long been deemed impregnable.[3] By 2009, we successfully synthesized carbon nanorings (cycloparaphenylene: CPP),[4] a feat also achieved independently by Bertozzi’s group in the United States around the same time.[5] CPP has become a subject of global study, with recent advancements in practical applications spanning devices and various fields. Our group’s notable achievements include an efficient CPP synthesis method, commercialization of seven CPP compounds,[6] and the synthesis of diverse derivatives like perfluorinated CPPs[7] and methylene-bridged CPPs.[8,9] Our work extends to the discovery of unique optoelectronic properties, advancements in supramolecular chemistry, development of host-guest chemistry,[10] stimuli-responsive materials in bioimaging applications,[11] and the use of CPP as a template for carbon nanotube synthesis.[12]

　After 12 years of dedicated efforts, in 2017, we achieved the synthesis of a thick and fully fused carbon nanobelt (CNB);[13] essentially an ultrashort carbon nanotube. Despite their simple and beautiful structures and potential applications in semiconductors and photonics, their synthesis has alluded scientists for more than 60 years due to the high strain on the benzene rings required for its formation. After achieving the first synthesis of CNB, we not only enhanced synthesis efficiency,[14] contributing to CNB commercialization[15] but also achieved more challenging CNB variants with zigzag edges[16] and a Möbius topology.[17] These sought-after CNBs are now employed as functional nanomaterials across diverse fields, marking a significant trend in chemistry.

Synthesis of topologically unique molecular nanocarbons

　In our lab, we also innovated an expandable collection of topologically unique molecular nanocarbons, such as the synthesis of the first carbon nanocage accomplished in 2013.[18] Of particular interest are mechanically interlocked molecules like catenanes, rotaxanes, and molecular knots, prized for their appealing structures and potential applications in molecular machines. In 2019, we successfully synthesized an all-benzene catenane and trefoil knot, providing fully characterized structures.[19]

　Beyond these achievements, three-dimensional curved nanocarbons remained unexplored until 2013, when, in collaboration with Larry Scott, we synthesized a novel warped nanographene (WNG) featuring both positive and negative curvatures on its π-surface.[20] WNGs distinguish themselves from other nanocarbons by their negatively curved geometry imparting a flexible configuration in the solution. Commercially available WNGs are now integral components in various industries,[21] particularly in optoelectronic devices.

　We also developed a water-soluble WNG with long-lived green-yellow fluorescence, excellent photostability, and remarkably low cytotoxicity to cells.[20] This water-soluble WNG, when introduced into HeLa cells, induced cell death by light irradiation, showcasing its potential in photodynamic therapy. Furthermore, WNGs exhibited the ability for one-dimensional self-assembly, resulting in the creation of the first all-carbon organogels.[20]

　At Itami lab, we further expanded our portfolio by synthesizing helically twisted nanocarbons, including multiple helicenes[22] and the infinity-shaped figure-of-eight nanocarbons (infinitene), which was recognized as the molecule of the year in 2021.[23] This diverse collection of topologically unique molecular nanocarbons is poised to open new avenues in organic chemical synthesis, material design, and applied technology.

　During this period, we pioneered the fusion of nanocarbon synthesis chemistry, condensed matter physics,[24] and supramolecular/carbon materials chemistry,[25] through the JST-ERATO Itami Molecular Nanocarbon Project. Collaborative research with companies has facilitated the incorporation of molecular nanocarbons into materials science applications, particularly in the realm of organic electronics.

New reactions and catalysts for intuitive molecular assembling and editing

　Synthetic chemistry serves as the lifeblood for tailoring molecules with diverse structures. We have pioneered the development of numerous novel chemical reactions that activate and connect molecules in an “intuitive” and “direct” manner, transcending the limitations found in traditional textbooks. Notably, we have successfully accomplished direct carbon–hydrogen (C–H) bond activation in aromatic compounds, abundant in nature, enabling the rapid synthesis of arene-assembled molecules including molecular nanocarbons. Our arsenal includes approximately 20 unique C–H transformation catalysts,[26] widely adopted by researchers worldwide. Additionally, nine commercially available catalysts, ligands, and reagents have been employed in groundbreaking work.

　Furthermore, we proposed and successfully developed the annulative π-extension (APEX) reaction[27] as an innovative synthetic methodology. This technique facilitates the rapid synthesis and direct conversion of nanographene, leading to the creation of various functional nanocarbon molecules. The APEX reaction represents a significant stride in the field, providing a versatile approach for synthesizing complex nanocarbon structures with broad applications.

The launch of ITbM and collaboration with plant and animal biologists, and theoretical chemists

　In 2012, Itami established the Institute of Transformative Bio-Molecules (ITbM) at Nagoya University.[28] Here, the Mix-Lab concept was introduced, fostering an environment where researchers from diverse fields could collaborate freely, transcending traditional boundaries. The overarching goal was to pioneer new fields of interdisciplinary research guided by the mantra “changing the world with molecules.”

　As the founding director of ITbM, Itami has played a pivotal role in leading cutting-edge research. Our lab has actively contributed to the development of several groundbreaking molecules. These include inhibiting molecules for the parasitic plant Striga,[29] stomatal controlling molecules[30] modulating the biological clock,[31] and molecules designed to enhance plant fertilization efficiency.[32]

　Over the years, ITbM has evolved into a world-leading international research institute, seamlessly integrating various fields of study. The collaborative and interdisciplinary nature of ITbM has positioned it as a hub for innovative research, marked by the synthesis of transformative molecules and their applications across diverse scientific domains.[33]

 

References

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