N EWS O F T H E W E E K
SPYING ON CATALYSTS SPECTROSCOPY: Infrared method
E L I STAV I TS K I / U T R EC H T U N I V E RS I T Y
probes reactions as they occur in zeolites
F
OR THE FIRST TIME, researchers have applied
infrared microspectroscopy to monitor catalytic reactions as they occur within the pores of zeolite crystals (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200705562). MONITOR The technique provides sciA new method can probe molecules, entists with a new procedure such as the cationic fluorinated for probing the detailed relastyrene dimer depicted, as they form tionship between a catalyst’s in the channels of a zeolite crystal. structure and its function. The method also o offers a means for elucidating reaction pathways re mediated by industrially relin evant catalysts catalyst such as zeolites. Like law en enforcement agents who search fo for ways to spy on criminals so th they can catch the perpetrators perpetrato “in the act,” chemists try to t develop methods to monito monitor catalysts under typical condit conditions and catch the catalysts pr promoting chemical reactions. re Developing analytical methods that are compatible with elevated temperatures and pressures
and other standard catalysis reaction conditions is challenging. Yet a few in situ microscopy and spectroscopy methods that can scrutinize the internal surfaces of porous catalyst materials during the course of a reaction have already been developed. Now, researchers at Utrecht University, in the Netherlands, have added the molecular-structure-resolving power of vibrational spectroscopy to that small but growing collection of in situ analytical tools. Demonstrating the technique, chemistry professor Bert M. Weckhuysen, postdoc Eli Stavitski, and their coworkers exposed micrometer-sized crystals of an acidic zeolite, H-ZSM-5, to 4-fluorostyrene. They heated the samples and then probed the styrene oligomerization process in various ways with high-intensity synchrotron IR radiation. In one set of experiments, the group focused on a 5- × 5-μm region of a single crystal for a prolonged period to monitor the evolution of the oligomerization process over time in that spot. In other experiments, the researchers scrutinized larger areas by scanning individual crystals under the microscope’s field of view. Among other outcomes, the team observed the principal reaction intermediate, a bisphenyl-ylium cationic dimer. They identified that species by comparing calculated spectra to spectra measured experimentally. The group also deduced the dimeric cation’s molecular orientation within the zeolite’s channels and mapped its microscopic distribution across the catalyst both spatially and temporally. Matthew Neurock, a professor of chemical engineering at the University of Virginia, notes that the new IR method, used either by itself or in conjunction with fluorescence and UV-Vis techniques, “will provide unprecedented resolution of the time and spatial mapping of reactant, intermediate, and product molecules in catalytically active microporous systems under actual catalytic working conditions.” He adds that the method “will greatly increase our understanding of molecular transformations that follow during the course of catalytic reactions.”—MITCH JACOBY
CAREER CHANGE Chemist-president Cech steps down at HHMI to return to academia nounced competition for early-career scientists (C&EN, March 17, page 8). “A lot of the things I hoped to accomplish are well on their way, if not done,” Cech says. “The next big thing that the Howard Hughes Medical Institute engages in deserves to have somebody who’s going to see it through. Some of these projects are five to 10 years in length, and I had never planned to stay here that long. This seems like an appropriate time
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for me to return to being engaged directly with research and with teaching.” Cech plans to return to those activities at the University of Colorado, Boulder, where he has been a chemistry professor since 1978. During his time at HHMI, he has maintained a small research group studying telomeres (the DNA sequences that cap chromosomes) and telomerase (the enzyme that synthesizes telomeres).—CELIA ARNAUD PAU L F E T T E RS FO R H H M I
Biochemist Thomas R. Cech announced on April 1 that he will step down as president of Howard Hughes Medical Institute (HHMI) in spring 2009. A nationwide search for his successor is expected. Cech has been president of HHMI since January 2000. During his tenure, HHMI has launched several new initiatives, including the HHMI Professors program, which provides grants to research professors for the purpose of transforming undergraduate education; the Janelia Farm Research Campus in Ashburn, Va.; and the recently an-
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