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Chemistry professor Akira Sekiguchi of the University of Tsukuba, in Japan, has become renowned for his ability to make novel compounds of the heavier group 14 elements (silicon, germanium, and tin). In particular, he has become a wizard of silicon chemistry, converting target molecules that once existed only on paper into stable and fully characterizable compounds.
The growing list of silicon compounds he and his coworkers have created includes stable silyl radicals, cations, and anions, along with their heavier group 14 analogs; silicon analogs of triplet carbenes (silylenes); heterocyclic compounds and alkene analogs with silicon-germanium and other group 14 element double bonds; an alkyne analog with a silicon-silicon triple bond (disilyne); a silicon version of vinyllithium (disilenyllithium); and a stable, aromatic all-silicon ring (cyclotrisilenylium ion).
In 1995, most of these accomplishments were still challenging unsolved problems, notes chemistry professor Peter P. Gaspar of Washington University, St. Louis. But Sekiguchi's group has solved them all. "Sekiguchi is the most outstanding silicon chemist of the past decade, and he will remain an inspirational leader for many years to come," Gaspar says.
Silylenes, R2Si:, is one area where Sekiguchi has excelled. This class of compounds, discovered 30 years ago, was initially found to have different electronic properties from carbenes. While carbenes can take on singlet or triplet electronic ground states (with paired or unpaired nonbonding electrons, respectively), the silylenes were observed to assume only singlet ground states. In 2003, Sekiguchi succeeded in generating a silylene that had been predicted to have a triplet ground state, (R3Si)2Si:, where R = tert-butyl, and proving that it indeed was a triplet (J. Am. Chem. Soc. 2003, 125, 4962).
Although double and triple bonds between two carbon atoms have been standard fare in chemistry for more than a century, it wasn't until the 1970s that double bonds between the heavier group 14 elements began to appear. Clever synthetic strategies using bulky organic substituents as stabilizing groups eventually led to all of the alkene and alkyne analogs from silicon to lead to be made, with one exception: a compound containing a silicon-silicon triple bond. Sekiguchi's group scored yet another coup in 2004 by making the first isolable disilyne, R3Si-Si≡Si-SiR3 (C&EN, Sept. 20, 2004, page 9).
Sekiguchi, 53, received bachelor's and master's degrees in chemistry from Gunma University, and a doctoral degree in chemistry in 1981 from the University of Tsukuba. He immediately began his career at Tsukuba, later spent a postdoctoral year (1986-87) at the University of Wisconsin, Madison, and then returned to Japan to become an associate professor at Tohoku University. He assumed his current position as full professor at the University of Tsukuba in 1996.
He has written nearly 200 research papers and contributed to seven books. Among his honors and awards, Sekiguchi received the Japan IBM Science Award (1996), the Chemical Society of Japan Award for Creative Work (1997), the Bulletin of the Chemical Society of Japan Award (BCSJ Award) for outstanding research article (2001), and an Alexander von Humboldt Research Award (2004). He has served as an associate editor of the Bulletin of the Chemical Society of Japan, and he's currently an associate editor of Chemistry Letters and a member of the advisory board of Organometallics.
There will be an award address at the ACS national meeting in Atlanta before the Division of Organic Chemistry. A second award address and the award presentation will be held at the 39th Silicon Symposium during the ACS Central Regional Meeting in Frankenmuth, Mich., on May 16-20.—Steve Ritter