The element rhodium is a powerful catalyst — a driver of chemical reactions — but is also one of the rarest and most expensive. In addition to its common use in vehicle catalytic converters, rhodium is also used in combination with other metals to efficiently drive a wide range of useful chemical reactions.
Chemists' efforts to study the inner workings of dirhodium metal complex reactions have been hindered by their extreme efficiency and speed, reacting at about 300 times per second. Now, a team of scientists led by University of Wisconsin–Madison chemistry professor John Berry reports an advance that freezes one step of the process long enough to offer researchers a glimpse into the finer mechanism.
Chemical reactions pass through a series of steps from starting material to end product, with intermediate chemical structures formed at each step. The nature of those "part-way" compounds — called intermediates — can tell chemists a great deal about the processes and their efficiency.
However, intermediates normally exist for a second or less before moving to the next step in the reaction, making them extremely difficult to study. The new paper, appearing in this week's issue of Science Express (Sept. 12), describes the isolation and characterization of an intermediate that is stable for hours at 0 degrees Celsius.
"We've provided the first solid fundamental data on these compounds," said Berry, who led the effort to synthesize the stable version of a normally short-lived molecule. "People have thought about it for forty years, but this is the first time that we can actually see it and say this is definitely what's going on."
Berry and UW–Madison graduate student Katherine Kornecki used computational models to predict how the intermediate molecules might be trapped. From those predictions, they were able to identify a suitable dirhodium complex and starting material with the properties needed to stabilize the intermediate compound long enough to study it further.
Formation of the reactive intermediate is visible as the green starting material changes to an ocean blue color that faded over time. Ultraviolet-visible spectrometry showed the formation of a new molecule, and Berry rallied the help of collaborators to make sure they were actually capturing the desired intermediate.
Huw Davies from Emory University provided a starting material that allowed characterization of the compound by vibrational spectroscopy and nuclear magnetic resonance (NMR). Jochen Autschbach from the University of Buffalo used density function theory to predict the NMR features of the compound, and Kyle Lancaster from Cornell University elucidated the compound's structure using a series of X-ray absorption spectroscopy experiments.
"This paper is a wonderful example of how big challenges in chemistry can be solved by employing a multidisciplinary, collaborative approach," says Davies, professor of organic chemistry at Emory University and director of the Center for Selective C-H Functionalization.
In addition to providing evidence of an intermediate previously known only on paper, the finding opens new avenues for the field of catalysis. "Now that we can make the intermediate, we can further explore its reactivity. We can try reactions with substrates that nobody has ever thought of before," Berry says.
The work was supported by grants from the National Science Foundation and the U.S. Department of Energy.
—HongNgoc Pham, email@example.com; Jill Sakai, 608-262-9772, firstname.lastname@example.org
John Berry | EurekAlert!
New gene catalog of ocean microbiome reveals surprises
18.08.2017 | University of Hawaii at Manoa
Organ Crosstalk: Fatty Liver Can Cause Damage to Other Organs
18.08.2017 | Deutsches Zentrum für Diabetesforschung
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Information Technology