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Science Concentrates

May 31, 2004 | A version of this story appeared in Volume 82, Issue 22

Germanium amine boosts biradical diversity

Organic biradicals such as cyclobutane-1,3-diyl have been extensively studied by chemists as possible intermediates in reaction mechanisms. But only a few of these species are stable enough to be studied spectroscopically. Some researchers have found that replacing ring carbon atoms with phosphorus and/or boron atoms can lead to quite stable biradicals that can be studied in detail. A new class of these inorganic biradicals containing a Ge2N2 core has now been prepared by graduate student Chunming Cui, chemistry professor Philip P. Power, and coworkers of the University of California, Davis [J. Am. Chem. Soc., 126, 6510 (2004)]. The germanium-centered biradical (shown) was synthesized by reacting a germanium alkyne, RGeGeR, first reported by Power’s group in 2002, with excess trimethylsilyl azide. Crystal structure data supported by theoretical calculations reveal a perfectly planar Ge2N2 ring with a Ge–Ge separation of 2.76 Å, indicating that there is no germanium bonding interaction. The researchers conclude from the structure, the intense purple color of the crystals, the compound’s reactivity toward solvents, and the lack of an electron paramagnetic resonance signal that the germanium amine is a singlet biradical.

Familiar enzyme reveals surprising talent

In addition to its “day job” hydrolyzing phosphate esters, alkaline phosphatase from Escherichia coli moonlights as a hydrogenase enzyme. Microbiology associate professor William W. Metcalf and graduate student Kechao Yang of the University of Illinois, Urbana-Champaign, made this surprising observation while purifying an E. coli enzyme capable of oxidizing phosphite into phosphate and H2 [Proc. Natl. Acad. Sci. USA, 101, 7919 (2004)]. It turns out that the novel phosphite-dependent hydrogenase they were hunting for is none other than the well-studied enzyme alkaline phosphatase. Only a handful of other enzymes have been shown to carry out two completely different chemical transformations in vivo. In this case, the moonlighting gig seems to be unique to E. coli alkaline phosphatase—its eukaryotic relatives don’t oxidize phosphite even though they are better phosphatases. What’s more, “the phosphite-dependent, H2-evolving reaction the enzyme catalyzes is unprecedented in both P and H biochemistry, and is likely to involve direct transfer of hydride from the substrate to water-derived protons,” Metcalf and Yang point out.

PNAS tests open access

The National Academy of Sciences has begun an experiment in open access to the Proceedings of the National Academy of Sciences . Articles in the academy’s journal are already available online for free starting six months after they appear in print. Now the academy is offering authors the option to have their articles freely accessible online as soon as they are published. Authors who want to establish this free access for the public will pay a $1,000 surcharge. At the end of 2005, PNAS will evaluate the results of its open-access trial in terms of author participation and its impact on PNAS revenues. The academy says it hopes its experiment will “encourage other scientific publishers to follow suit.”

Microfluidic device for multiphase reactions

Using microfluidic channels, Shu Kobayashi and his colleagues at the University of Tokyo have developed a simple device that provides the high interfacial areas needed for efficient multiphase catalytic reactions [Science, 304, 1305 (2004)]. “This device provides a practical tool for the synthesis of pharmaceuticals and fine chemicals,” Kobayashi says. The researchers anchor a metal catalyst to the glass walls of the channels and flow liquid and gas reagents through them. When the flow conditions are carefully controlled, the gas flows through the center and the liquid flows along the inner surface of the wall. This configuration allows efficient solid-liquid-gas reactions to occur. Kobayashi and his colleagues demonstrate the device with palladium-catalyzed hydrogenation reactions of a variety of substrates with double or triple carbon-carbon bonds. The reactions are complete within two minutes with quantitative yields; the channels can be reused without a loss of catalyst activity. Although an individual device produces a small amount of the product, the reaction can be scaled up by using a number of the devices in parallel.

Name proposed for element 111

The Inorganic Chemistry Division Committee of the International Union of Pure & Applied Chemistry (IUPAC) has decided to recommend the name roentgenium (symbol Rg) for element 111. The name—which honors Wilhelm Conrad Roentgen, who discovered X-rays in 1895—follows the precedent of naming elements in row 7 of the periodic table after famous nuclear scientists. The name was proposed by researchers at the Heavy Ion Research Center (GSI) in Darmstadt, Germany, who reported, in 1995, the creation of three atoms of the element. The first atom was created on Dec. 8, 1994, after bombarding a rotating 209Bi target with a high-energy beam of 64Ni atoms for several days. Element 111 atoms have a half-life of around 1.5 milliseconds and a mass of 272. They form by fusion of nickel and bismuth, followed by emission of a neutron. The GSI team reported additional results in 2002 to confirm the discovery. Last year, a joint IUPAC-International Union of Pure & Applied Physics working party established that the GSI claim fulfilled the criteria for discovery of the element. The name now has “provisional” status and, provided it passes a five-month period of public scrutiny, will be ratified by the IUPAC Bureau when it meets later this year. IUPAC invites chemists to submit comments on the name by Oct. 31 to John Corish, professor of physical chemistry at Trinity College Dublin, who is managing the naming process.




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