Dr. Hiroo Inokuchi initiated pioneering research on electrical conduction between molecules with benzene rings and established the scientific foundation for studying the electrical conductivity of organic materials. Further, he systematically elucidated an electronic structure of a wide variety of organic materials by photoelectron spectroscopy. Through a series of such studies, he established the academic base essential for studying the electronic properties, making fundamental contributions to the subsequent development of organic molecular electronics.
On the Electrical Conductibity of Violanthrone, Iso-Violanthrone and Pyranthrone, The Journal of Chemical Physics 18: 810-811 (Akamatsu, H. and Inokuchi, H.), 1950.
Photoconductivity of Condensed Polynuclear Aromatic Compounds, Bulletin of the Chemical Society of Japan 27: 22-27, 1954.
Electrical Conductivity of the Perylene-Bromine Complex, Nature 173: 168-169 (Akamatu, H., Inokuchi, H. and Matsunaga, Y.), 1954.
Electrical Conductivity of Organic Semiconductors, Solid State Physics 12: 93-148 (with Akamatsu, H.), 1961.
“Organic Semiconductors”, Maki Shoten Publishing Co., p.201. (in Japanese), 1964.
A Novel Type of Organic Semiconductors. Molecular Fastener. Chemistry Letters : 1263-1266 (with Saito, G., Wu, P., Seki, K., Tang, T.B., Mori, T., Imaeda, K., Enoki, T., Higuchi, Y., Inaka, K. and Yasuoka, N.), 1986.
Dr. Hiroo Inokuchi focused his attention on organic molecules consisting of benzene rings in the late 1940s and started pioneering research on electrical conduction between molecules, discovering that they exhibit semiconducting properties. Further, he established the scientific foundation for studying the electrical conductivity of organic materials through his discovery that the addition of an electron-accepting substance to organic molecules dramatically increases electrical conductivity, making them an organic conductor. Moreover, Dr. Inokuchi systematically elucidated the electronic structure of a wide variety of organic materials by photoelectron spectroscopy. Through a series of such studies, Dr. Inokuchi established the scientific foundation essential for understanding and utilizing the electronic properties and functions of organic materials, making fundamental contributions to the subsequent development of organic molecular electronics.
Around 1950, Dr. Inokuchi, jointly with Dr. Hideo Akamatu, conducted groundbreaking studies that systematically investigated the intermolecular electrical conductivity of an organic molecule called violanthrone consisting of nine benzene rings, and found that this organic material is capable of acting like a semiconductor in a manner similar to inorganic materials. In addition, he discovered jointly with Dr. Akamatu and Dr. Yoshio Matsunaga that the addition of an electron-accepting substance such as bromine or iodine to an organic material such as perylene causes transfer of electrons between the two components and forms charge-transfer complexes with high charge density, thereby increasing electrical conductivity significantly. These pioneering studies triggered major advances in the science of organic conductors in the following 50 years, helping to establish a technological basis for the practical utilization of organic conductors. Dr. Inokuchi continued with systematic studies of photoelectron spectroscopy to elucidate the electronic structures of organic materials, determining the ionization energies of a large number of organic materials. The findings of this research played a critical role in the design and creation of organic electroluminescent (EL) devices in later years.
Dr. Inokuchi’s groundbreaking studies served as a basis not only for scientific investigations into organic conductors, which have advanced remarkably over the past fifty years, but also for the creation and development of technologies that utilize the electronic properties of organic materials, making fundamental contributions to the establishment of organic molecular electronics that includes applications to organic EL devices and organic transistors. Furthermore, Dr. Inokuchi has assisted in the development of outstanding researchers and research groups in the science and engineering fields of organic molecules and established a world-class center of excellence for the research of organic materials with electrical properties, making substantial contributions to international, academic interactions.
For these reasons, the Inamori Foundation is pleased to present the 2007 Kyoto Prize in Advanced Technology to Dr. Hiroo Inokuchi.
My journey in the field of chemical research began in April 1947, when I entered the laboratory of Professor Jitsusaburo Sameshiima as a third-year student in the chemistry department of the Faculty of Science in the University of Tokyo. As it was shortly after the end of the war, the laboratory was in a pathetic state and virtually devoid of newly published materials; but Professor Sameshima and my senior colleagues, who engaged in direct instruction, were veritable treasure troves themselves. My journey therefore began with learning from people. This has not changed right up to the present, some 60 years later. The story of this interaction with people is at the same time the story of my journey. It contains interludes of scolding and even stern lecturing as well as encouragement. Here, I would like to take up one of these interludes and comment on what are precious memories to me as my subject today. Specifically, I would like to share a poem that was composed by Professor Hideo Akamatu, another professor to whom I am deeply indebted, on the occasion of the gathering to celebrate my 60th birthday during my days at the Institute for Molecular Science (1975 to 1996): “Looking back, the bountiful harvest of autumn comes only after the toils of spring and summer.”
I also make a point of learning from things. Chemistry is a science of making substances and learning about their essences. In this sense, my first encounter came with measuring the electrical resistance of carbon blacks as the theme of my graduate research. The suggestion that the carbon blacks areconstantly combusting provided the key drive for my foray into the territory of organic semiconductors, my lifelong research theme. Taking natural and synthetic together, there are nearly 100 million types of substances (or things) on the face of the earth. People who major in chemistry do their utmost to synthesize a new type.
At this point, I would like to mention how, since the dawn of history, our ancestors contributed to human advancement by learning from natural things or, in other words, from nature. I also want to describe how what they learned in this way was correct even when viewed in the light of modern chemical knowledge.
Let us take the case of dyes. Some textiles on 1,500-year-old artifacts stored in Nara’s Shosoin repository were dyed using safflower and saffron. Only recently, well over a thousand years later, scientists have determined that the molecular structures of such dyes, which our ancestors discovered empirically, were optimal for dyeing.
Dyes are only one example. Penicillin; smallpox vaccine; and chemical condiments derived from Japan’s research, the kind of research in which it takes great pride, are all examples of substances isolated from compounds that were born by learning from nature.
I have high hopes that we will be able to bequeath human knowledge intact to succeeding generations, learn from the things in nature brimming with wonder, and maintain the health of the earth in a balanced manner.