NEWS OF THE WEEK
MOLECULAR CLOSE-UP ELECTRON MICROSCOPY: Images show motions of single, confined molecule
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Y CONFINING a single, small organic molecule inside a narrow, single-walled carbon nanotube, scientists in Japan have been able to use transmission electron microscopy (TEM) to follow the molecule's motions with near-atomic resolution (Science, DOI: io.H26/science.H3869o). "What we did is like trapping a flying bee in a glass tube to see how the wings move," remarks Eiichi Nakamura, the chemistry professor at the University of Tokyo who led the discovery team supported by the Japan Science & Technology Agency. In a vacuum, small molecules tend to move too fast, he explains, but trapping them in a nanotube slows them down enough to allow close observation. Nakamura and coworkers studied several guest molecules, including ortho-carboranes bearing two adjacent alkyl chains up to 22 carbon atoms long. They vaporized the molecules and allowed them to diffuse into the nanotubes in vacuum. By irradiating the nanotubes with electrons at roughly 2-second intervals, the researchers were able to capture the molecules' mo-
F. ALBERT COTTON DIES OBITUARY: Inorganic chemistry pioneer was first to show existence of metal-metal quadruple bond
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RANK ALBERT (AL) COTTON, world-renowned inorganic chemist, died on Feb. 20 at age 76 from complications stemming from a head injury he suffered from a fall in October. He is survived by his wife of 47 years, Diane, and two daughters. Cotton's research spanned more than 50 years and included seminal work in the areas of metal-metal bonding, organometallic chemistry, and computational chemistry. Among the highlights of his career are studies of the first metal-metal quadruple bonds, the first mechanistic studies of fluxional organometallic compounds, and work leading to the resurrection of crystal field theory. Author of more than 1,600 publications, Cotton was the W. T. Doherty-Welch Foundation Chair in the chemistry department at Texas A&M University. Prior to joining Texas A&M in 1972, Cotton was a faculty
tions in stop-action videos. These videos reveal the molecule moving along the length of the nanotube as well as undergoing conformational changes. The images show that an alkyl tail sometimes momentarily sticks to the nanotube wall. "You can also study the entanglement of the tails" to get a measure of the competition between tail-tail and tail-wall attractions, comments chemist Roald Hoffmann of Cornell University. "This is the most direct visualization of the motion of a molecule inside a nanotube" that he's seen, Hoffmann tells C&EN, and it's "damn clever." Two reviewers of the paper were similarly impressed, calling the work "an exciting achievement" and "a very ambitious study" offering "amazing" data. TEM has been used previously to image molecules such as proteins and fullerenes. Scientists have attempted to image small organic molecules in thin films, but these tend to decompose under electron impact, partly due to heat formation, Nakamura points out. "What we discovered is that a single molecule in a nanotube in vacuum survives TEM conditions for some time."—RON DAGANI MORE ONLINE
Visit C&EN Online for TEM videos of molecules moving inside a carbon nanotube.
member at MIT. His work earned him many honors, including the ACS Priestley Medal, the Wolf Prize, and the National Medal of Science. He was an emeritus ACS member, as well as a member of the National Academy of Sciences and the American Philosophical Society. "Our department's loss of a colleague and friend is shared by the entire academic and industrial chemical community," says David H. Russell, chemistry department chairman at Texas A&M. "He was a great role model for scientists of all ages, but it is important to realize that few will be able to impact the chemical sciences in a similar way." Cotton's legacy includes not only five text and reference books but also a large scientific family. "Al Cotton was a giant figure in inorganic chemistry," says Stephen J. Lippard, chemistry professor at MIT and a former Cotton student. "He cared deeply about his extended scientific family and went to great lengths to nurture their careers. His death is a huge loss for the chemical community." "Those of us who knew Al had the privilege to know one of the most brilliant, focused, imaginative, and driven individuals in chemistry and beyond," says Bruce E. Bursten, ACS president-elect and a former Cotton postdoc. "We will miss his presence, but his legacy in chemistry will last forever."—SUSAN MORRISSEY
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TEM image (top) and molecular model (bottom) show the conformation of a carborane bearing two alkyl chains inside a carbon nanotube. Boron atoms are pink; hydrogen, white; carbon, gray.
FEBRUARY 26, 2007
