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Materials

ACS Award For Creative Research & Applications Of Iodine Chemistry

by Stephen K. Ritter
February 2, 2015 | APPEARED IN VOLUME 93, ISSUE 5

Christe
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Credit: Joerg Sarbach
09305-awards1-christecxd.jpg
Credit: Joerg Sarbach

Sponsored by SQM S.A.

Karl O. Christe, a research professor at the Loker Hydrocarbon Research Institute at the University of Southern California, has long been a hero of chemistry fans who love to see what kind of strange and seemingly impossible compounds can be created from the elements. One facet of Christe’s work to make unusual molecules that is now being singled out involves the synthesis of inorganic iodine compounds.

“Karl Christe is one of the most imaginative and creative inorganic chemists of our times,” says George A. Olah, a USC colleague. “He has enriched chemistry in varied fields, including the discovery of many interesting, simple, and novel iodine compounds, for which he is receiving this most deserved prize.”

For example, Christe and his coworkers have synthesized many binary iodine fluorides, including IF2, IF4, IF4+, IF52−, IF6, IF6+, IF8, I2F11, and I3F16. Christe also discovered IF4O, IF5O2−, IF5O22−, and IF6O. With these compounds, Christe unveiled molecules reaching the limits of coordination, in several cases featuring unprecedented pentagonal planar and pentagonal bipyramidal structures. This work also revealed how to stepwise replace two fluorine atoms with an oxygen atom.

With I(ClO4)3 and I(ClO4)4, Christe discovered the first examples of iodine perchlorates. He also synthesized IF4OF and IF4OCl, the first iodine hypofluorites and hypochlorites, as well as I2O6. Christe found that iodine fluorosulfate, ISO3F, can be added across olefinic double bonds to form iodoperfluorocarbon fluorosulfates. And he solved the long-standing problems of the fluxionality of IF7 and the steric activity of the free valence electron pair in halogen hexafluoride anions.

The casual chemist might wonder what anyone would want to do with this zoo of iodine compounds. These molecules have many applications as explosives, propellants, and powerful oxidizing reagents—often in secret defense applications.

“Karl has a deeper understanding of the nature of inorganic iodine compounds than anyone,” says David A. Dixon of the University of Alabama, a longtime collaborator. “Not only has he made novel compounds of fundamental scientific interest, he has applied them to fields such as high-energy-density materials and chemical lasers.”

Christe received B.S., M.S., and Ph.D. degrees from the Technical University of Stuttgart, in Germany, in 1957, 1960, and 1961, respectively. Christe has spent most of his career working in industry, notably with defense contractors Rocketdyne (1967–94) and Raytheon, Hughes, and ERC (1994–2005). In 1994, he also joined the chemistry faculty at USC.

Among his other honors, Christe is a recipient of the 2006 Alfred Stock Prize from the German Chemical Society, the ACS Award in Inorganic Chemistry (2003) and Award for Creative Work in Fluorine Chemistry (1986), the international Prix Moissan for fluorine chemistry (2000), and the Apollo Achievement Award from the National Aeronautics & Space Administration (1969).

Preparing and characterizing Christe’s menagerie of iodine compounds has required a certain fearlessness and skill in the lab. Besides dueling with halogens, Christe is a renowned athlete, participating in fencing and bicycle racing. He is a former member of both the German and U.S. national fencing teams, and he is still active as a fencing coach.

Christe will present his award address before the Division of Fluorine Chemistry.

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