Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A crystal of a different color

05.08.2013
1 chemical forms 2 colors of crystals, sheds insight on agostic bonds important in industrial catalysis

Chemists have unexpectedly made two differently colored crystals – one orange, the other blue – from one chemical in the same flask while studying a special kind of molecular connection called an agostic bond. The discovery, reported in Angewandte Chemie International Edition on July 29, is providing new insights into important industrial chemical reactions such as those that occur while making plastics and fuels.


One flask of chemicals gives rise to either blue or orange crystals. Credit: van der Eide/PNNL

"We were studying agostic bonds in a project to make liquid fuels like methanol from carbon dioxide to replace fuels we get from oil," said chemist Morris Bullock at the Department of Energy's Pacific Northwest National Laboratory. "We knew the molecule we were making would have an agostic bond, but we had no idea there'd be two flavors of these metal complexes."

While chemists have studied these bonds in chemicals in liquid form, no one had crystallized one chemical with multiple forms of its agostic bonds. And no one expected different forms to give rise to different colors.

Bonds come in many varieties in molecules. They string atoms together, sometimes forming a trunk and branches of atoms like a tree. But the trunk and branches of chemicals often fold up into a more compact shape, requiring additional weaker bonds to hold the shape in place. An agostic bond is one of these additional bonds, a shape-holder. They occur between a metal and a distant carbon-hydrogen bond along some chain, folding the chain back to the metal and pinning it there.

First discovered in the 1980s, agostic bonds frequently occur in catalysts because catalysts usually contain metals. This work will help researchers get a better handle on some catalytic reactions found in common industrial processes such as making plastic or fuels.

Heart of the Matter

The metal in a catalyst is usually the reactive heart of the molecule. Bullock and postdoctoral chemist Edwin van der Eide knew an agostic bond in their catalyst would help protect the reactive metal from working at the wrong time: The carbon-hydrogen bond blocks the reactive metal until conditions were right, which in turn would help the scientists better control the catalytic reactions. So van der Eide set about producing and crystallizing catalysts that contain a metal atom -- in this case, molybdenum.

In the lab, van der Eide's flask of chemicals held a molybdenum-containing molecule that turned the solution violet. He added another liquid to coax the molybdenum complex to crystallize, just as salt crystallizes from seawater to form flakes at the seashore. Some crystals formed at the bottom of the flask and others formed near the top of the violet solution.

Oddly, the crystals were two different colors.

Orange crystals formed at the bottom of the flask and blue above. If van der Eide dissolved either the orange or blue crystals in a fresh flask of the original solvent, the violet color returned, with the same properties as the original violet solution. These results suggested that either molecule in the two colored solids could give rise to both structures in liquid, where they easily change back and forth.

The researchers examined the differently colored crystals to determine their structures. The molecule forms a shape like a piano stool: a ringed section forms a stool seat on top of the molybdenum atom, with multiple legs connecting to the molybdenum at the bottom.

One of the legs, however, is longer than the others and contains a chain of three carbon atoms, each with at least one protruding hydrogen. The team found that the long leg was involved in the agostic bonds, with the middle carbon atom involved in the orange crystals and an end carbon involved in the blue crystals.

PNNL's Ping Yang at EMSL, DOE's Environmental Molecular Sciences Laboratory on the PNNL campus, took to EMSL's supercomputer Chinook to perform theoretical calculations on the orange and blue structures. Chemically, the two structures were almost equally likely to form, with the blue one having a slight edge. The analysis also revealed why the crystals were different colors, which is due to subtleties within the structures.

This work was supported by the Department of Energy, Office of Science.

Reference: Edwin F. van der Eide, Ping Yang, and R. Morris Bullock. Isolation of Two Agostic Isomers of an Organometallic Cation: Different Structures and Colors, Angewandte Chemie July 29, 2013, doi:10.1002/anie.201305032. (http://onlinelibrary.wiley.com/doi/10.1002/anie.201305032/full)

The Department of Energy's Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit http://science.energy.gov/.

Interdisciplinary teams at Pacific Northwest National Laboratory address many of America's most pressing issues in energy, the environment and national security through advances in basic and applied science. Founded in 1965, PNNL employs 4,400 staff and has an annual budget of more than $1 billion. It is managed by Battelle for the U.S. Department of Energy. For more information, visit the PNNL News Center, or follow PNNL on Facebook, LinkedIn and Twitter.

EMSL, the Environmental Molecular Sciences Laboratory, is a national scientific user facility sponsored by the Department of Energy's Office of Science. Located at Pacific Northwest National Laboratory in Richland, Wash., EMSL offers an open, collaborative environment for scientific discovery to researchers around the world. Its integrated computational and experimental resources enable researchers to realize important scientific insights and create new technologies. Follow EMSL on Facebook, LinkedIn and Twitter.

Mary Beckman | EurekAlert!
Further information:
http://www.pnnl.gov

More articles from Life Sciences:

nachricht Cells communicate in a dynamic code
19.02.2018 | California Institute of Technology

nachricht Studying mitosis' structure to understand the inside of cancer cells
19.02.2018 | Biophysical Society

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Contacting the molecular world through graphene nanoribbons

19.02.2018 | Materials Sciences

When Proteins Shake Hands

19.02.2018 | Materials Sciences

Cells communicate in a dynamic code

19.02.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>