News Article | January 4, 2016
Four new elements will join more than a hundred others on the periodic table of the elements, the International Union of Pure and Applied Chemistry (IUPAC) announced last week. IUPAC has now initiated the process of formalizing names and symbols for these elements," Jan Reedijk, president of the Inorganic Chemistry Division of IUPAC, said in a statement. Right now, the new elements have placeholder names and symbols that denote the elements' atomic numbers.
Motörhead fans still mourning the death of the band's singer, songwriter and bassist, Ian 'Lemmy' Kilmister, in December are seeking commemoration for the rock icon in an unusual location — the periodic table. A petition launched on Change.org by John Wright of York, United Kingdom, proposed "Lemmium" as a name for element 115, quickly gathering thousands of signatures. The element holds the cumbersome temporary working name "ununpentium" and the temporary symbol Uup, according to a statement issued by the International Union of Pure and Applied Chemistry (IUPAC) on Dec. 30, 2015. (The name references the Latin roots of "115," the numerals in the element's atomic number.) The IUPAC officially added element 115 and three other new elements to the table, according to the statement. The four elements are among the heaviest to date and the first to be added since 2011, completing the table's seventh row. This news might not have normally caught the attention of your average heavy metal headbanger, but Lemmy, as he was widely known, had died only two days before the IUPAC announcement, on Dec. 28, and his loss was still fresh in many fans' minds. When these yet-to-be-named "superheavy" elements were made public, Wright recognized a uniquely appropriate opportunity to honor a man who, for many, embodied the heavy metal genre. [Video: Head-Banging Bee Puts Metal Heads to Shame] Lemmy, a member of Motörhead since the band's formation in 1975, famously lived the "sex, drugs, and rock-and-roll" lifestyle to the fullest. While other band members rotated in and out over the years, Lemmy remained a permanent fixture. He was a larger-than-life figure whose snarling vocals and frantic bass-playing churned with raw energy, defining the fast-paced, high-powered rock music that came to be known as heavy metal, his fans have said. (Lemmy usually declined to label Motörhead as heavy metal, describing the group's music as rock and roll.) On the petition's website, Wright wrote, "We believe it is fitting that the International Union of Pure and Applied Chemistry (IUPAC) recommend that one of the four newly discovered heavy metals in the periodic table is named Lemmium." As of Jan. 12, the petition is just a few thousand entries away from its goal of 150,000 signatures. Naming these new elements is a privilege generally reserved for the scientists who identified them. "The discoverers from Japan, Russia and the USA will now be invited to suggest permanent names and symbols," IUPAC officials announced in the statement. According to the IUPAC naming conventions, "New elements can be named after a mythological concept, a mineral, a place or country, a property, or a scientist," which would seem to rule out the inclusion of a hard-partying rock-and-roller, no matter how iconic he might be. Once IUPAC's Inorganic Chemistry Division accepts a proposed name (and two-letter symbol), the name undergoes a five-month public review process, after which the IUPAC's Council, the group's highest body, finalizes the element's official name and symbol. This heralds the element's official introduction into the periodic table of the elements. Follow Mindy Weisberger on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science. Copyright 2016 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Scientists designed, created, and tested a chromium (Cr) complex, finding that a novel phosphorus-containing ring structure helps chromium turn dinitrogen and acid into ammonia. This work is part of efforts to develop molecular complexes to control electrons and protons for use in turning renewable energy into storable fuels. Credit: Jonathan Darmon, PNNL Underappreciated compared to its heavier metal counterparts, chromium failed for more than 30 years to turn nitrogen gas into ammonia, a reaction that involves breaking one tough bond and making six new ones. But scientists at the Center for Molecular Electrocatalysis thought chromium was up to the job; it just needed a little support. At the center, one of DOE's Energy Frontier Research Centers (EFRCs), the scientists created a 12-atom ring structure called a ligand that partially surrounds the metal and offers a stable environment for the metal to drive the reaction. By creating this ligand structure, the team demonstrated the importance of the environment supporting chromium. Often a key to controlling metal reactivity, the structure encircling the chromium causes the normally unreactive dinitrogen to become more reactive when it binds to the metal. "This research required the synergy of experimental and computational efforts in an EFRC," said the study's lead Dr. Michael Mock at DOE's Pacific Northwest National Laboratory. "Studying this challenging reaction has benefited from the multiple years of funding that an EFRC enables." The EFRCs are funded by the Office of Basic Energy Sciences at DOE's Office of Science. Producing ammonia for fertilizer consumes vast quantities of energy, an issue that this work may one day help solve. However, this study is focused on another important challenge: storing intermittent wind and solar energy. Solar panels and wind turbines produce electrons that flow along power lines to energize appliances around our homes. But, solar power levels drop when the clouds roll in. What if those electrons could be stored inside a chemical bond, as an energy-dense storage option? This study, which is complemented by two previous reports focused on understanding dinitrogen reactivity with chromium, may someday lead to the development of a system with this common metal as a hard-working catalyst. "This research shows how important it is to move six electrons and six protons in the right order," said Dr. Roger Rousseau, who led the computational studies. "It is rather like herding cats-and very difficult cats at that." There is a long tradition of turning dinitrogen (N2) into ammonia (NH3) using complex molecular catalysts, materials that reduce the roadblocks to make the reaction occur and aren't consumed in the process. Of the metals studied in the column known as group 6 transition metals, chromium supported by phosphorus ligands didn't work. In fact, papers from 1970 to the present day reported failures using chromium even in an environment that was thought to goad it into working. However, Mock and his team focused on the stabilizing effect from the phosphorus atoms of a 12-membered ligand that partially surrounded the chromium metal. Every fourth atom in the ring is a phosphorus atom that forms a bond with the chromium atom. The chemical bonds formed with three phosphorus atoms of the large ring together with two additional phosphorus donor atoms of a second ligand make the chromium atom very electron rich, which then can bind the dinitrogen. Once bound, the dinitrogen triple bond is weakened by coordination to the metal. The team showed that the correct surroundings enhance chromium's ability to bind and activate dinitrogen. In fact, the dinitrogen molecule in this case is more activated than in similar complexes with the heavier metals, molybdenum and tungsten, which have similar properties to chromium. However, breaking the dinitrogen triple bond is still a delicate task. The team found that managing the number of phosphorus atoms and the electron-donating ability of these atoms was crucial. The team ran the reactions with acid at -50°C so that certain intermediate products containing nitrogen-hydrogen bonds didn't fall apart. In these reactions, hydrogen ions from the acid surrounding the complex formed only a small amount of ammonia. They showed that adding acid caused the protons to favor binding with the metal, an unwanted connection. Additional optimization of the chromium complex and the conditions is required to control the formation of the desired nitrogen-hydrogen bonds. The reaction still has secrets to reveal. The team is digging into two of them. First, how do the 12-membered rings that support the chromium form? In the experiments, the rings self-assemble around the chromium. What factors dictate that formation? Also, how can the protons be controlled to prevent them from binding to the electron-rich chromium and form additional bonds with nitrogen? Answering these questions could lead to learning how to control the reaction's environs and lead to a catalyst that is fast, efficient, and long lasting, to convert nitrogen to ammonia. Explore further: Converting Nitrogen to a More Useful Form More information: Michael T. Mock et al. Protonation Studies of a Mono-Dinitrogen Complex of Chromium Supported by a 12-Membered Phosphorus Macrocycle Containing Pendant Amines, Inorganic Chemistry (2015). DOI: 10.1021/acs.inorgchem.5b00351
Grinding a crystalline metal-organic framework (MOF) material in a ball mill converts it into an amorphous structure and then into other crystal morphologies, according to research presented Tuesday at the American Chemical Society national meeting in Boston. The observation suggests researchers could use mechanochemical synthesis as a route to new MOFs. Tomislav Friščić, a chemistry professor at Canada’s McGill University, reported the work in a symposium sponsored by the Division of Inorganic Chemistry. “We have almost direct proof of nucleation and crystal growth taking place during milling, which is very counterintuitive,” Friščić said. MOFs are porous materials investigated for use in gas storage, catalysis, separation, and sensing. They are typically prepared from a metal salt and an organic ligand, using organic solvents in a process that often involves high temperature and bases. In contrast, mechanochemical synthesis replaces thermal with mechanical energy and can start from an easily obtainable metal oxide, eliminate the need for bases, and sharply reduce or eliminate solvents. Friščić and colleagues, including Ivan Halasz of Croatia’s Ruđer Bošković Institute and Trong-On Do of Canada’s University of Laval, explored mechanochemical synthesis of a commercially relevant zeolitic MOF called ZIF-8 by grinding ZnO and 2-methylimidazole (HMeIm) using steel balls in a poly(methyl methacrylate) milling jar (Nat. Commun. 2015, DOI: 10.1038/ncomms7662). The clear milling jar allowed them to monitor the material using an X-ray beam at the European Synchrotron Radiation Facility, in Grenoble, France. They added small amounts of acetic acid or water to the milling jar to catalyze the reaction. While milling, they initially observed a diffraction pattern that they had expected: ZIF-8, Zn(MeIm) , in the “sodalite” topology. The diffraction pattern, however, disappeared with further milling, indicating conversion to amorphous material. Then another diffraction pattern appeared. “That was fully unexpected,” Friščić said. They eventually determined that the new diffraction pattern reflected a new ZIF-8 polymorph not previously observed. The team named it katsenite, after McGill postdoctoral fellow Athanassios D. Katsenis. Ground further, katsenite turns into a third, previously known diamondoid polymorph. Mechanically synthesizing MOFs in a safer, cleaner way is a great advance, comments Omar Farha of Northwestern University. But seeing new topologies arise from amorphous material after grinding is “spectacular.” Chemists Get Back To The Grind With Mechanochemistry
News Article | March 16, 2016
When it comes to making phosphorus compounds, chemists have traditionally relied on white phosphorus, P , a tetrahedral-shaped allotrope of the element. The one downside with white phosphorus is that it’s toxic and flammable. Red phosphorus, an air-stable amorphous oligomeric allotrope, is a safer alternative. But chemists have had difficulty processing the relatively inert material in large quantities without resorting to high temperature and strong reducing agents. Florida State University chemists have now solved that problem by discovering an easy way to convert red phosphorus to soluble polyphosphides (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201511186). Alina Dragulescu-Andrasi, a postdoctoral researcher in Michael Shatruk’s group, provided details of the approach during a Division of Inorganic Chemistry symposium on Monday at the American Chemical Society national meeting in San Diego. The team simply passes a solution of inexpensive potassium ethoxide in an organic solvent through red phosphorus under mild heating to produce P –, P 2-, and P 3-. These variously sized clusters, which the researchers isolate as potassium or tetrabutylammonium salts, could be used to synthesize phosphorus compounds or to make two-dimensional semiconductors and lithium-ion battery anodes. Taking the process a step further, the researchers adapted it to run as a continuous-flow reaction by passing potassium ethoxide through a stainless-steel column packed with red phosphorus, generating multigram amounts of the soluble polyphosphides. The Florida State team’s work is funded in part by a Small Business Innovation Research grant in collaboration with Chemring Ordnance, a Florida-based munitions company. “This appears to be a relatively safe and convenient methodology for generating soluble salts of polyphosphide anions,” commented MIT’s Christopher C. Cummins, who builds new compounds from elemental phosphorus. “It should open the door to more widespread study and application of these interesting little bits of reduced phosphorus.”