Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Molecular Hinges Open Pathways

28.02.2014
Exchange of bismuth atoms for chloride ions with retention of structure
 

Modern technology makes extensive use of ion exchangers. For example, they are commonly used to decalcify water by binding calcium ions and releasing sodium ions in return. Good exchangers tend to be materials with high surface areas, such as resins, zeolites, or clays. German scientists have now demonstrated that the compact, crystalline structures of intermetallic compounds, in which the diffusion pathways for efficient materials transport are actually absent, can also exchange ions. In the journal Angewandte Chemie, they report the full replacement of the chloride ions in Bi12Rh3Cl2 crystals by bismuth atoms.


The team working with Michael Ruck at the Technical University of Dresden noticed this unexpected phenomenon while researching bismuth subhalides. Subhalides are compounds that have fewer halogen ions than pure ionic metal halides. This results in regions that contain direct bonds between metal atoms. Subhalides with bismuth and rhodium are known to have intermetallic substructures that range from clusters to three-dimensional networks. Bi12Rh3Cl2  contains intermetallic networks consisting of edge-sharing [RhBi8] cubes and antiprisms.

The researchers planned to “pull” the halogen atoms out without destroying the intermetallic regions under gentle conditions using an n-butyllithium solution. The chloride ions were extracted just as the scientists hoped, even though they seemed to be tightly enclosed by the narrow channels of the intermetallic network. Even more surprisingly, the resulting voids in the crystal structure were filled by bismuth atoms. The bismuth atoms came from barely noticeable chemical decomposition of the surface of the crystal.

The resulting product is Bi12Rh3Bi2, a metastable superconductor with a structure identical to that of the subchloride. During the reaction, the morphology of the crystal remains unchanged. “The transformation must be based on efficient transport of chloride ions out and bismuth ions into the network,” says Ruck. Crystallographic studies revealed a small change in the torsion angle of the [RhBi8] antiprisms. “The antiprisms act as hinges in the network,” explains Ruck. “Transient changes in the angle allow wide diffusion pathways to open up parallel to all of the intermetallic strands. Since the diffusion paths intersect, the transport system is three-dimensional.”

Although the intermetallic network only changes very slightly, the electronic properties are significantly different: the subchloride only demonstrates metallic conductivity along special directions that are insulated by nonconducting parts of the structure. In the intermetallic compound, in contrast, the conducting strands are metallically connected through the additional bismuth atoms. They are thus electrically connected, resulting in a three-dimensional metal.

About the Author

Professor Dr. Michael Ruck conducts research and teaches chemistry and food chemistry at the Technical University of Dresden. He works in the area of solid-state chemistry and is particularly interested in metallic compounds and low-temperature synthesis of materials. He is also a Fellow of the Max Planck Institute of the Chemical Physics of solids in Dresden.

Author: Michael Ruck, Technische Universität Dresden (Germany), http://www.cpfs.mpg.de/

Title: The Topochemical Pseudomorphosis of a Chloride into a Bismuthide

Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201309460

| Angewandte Chemie
Further information:
http://pressroom.angewandte.org

Further reports about: Molecular bismuth Atoms chloride compounds ions pathways rhodium

More articles from Life Sciences:

nachricht Researchers uncover protein-based “cancer signature”
05.12.2016 | Universität Basel

nachricht The Nagoya Protocol Creates Disadvantages for Many Countries when Applied to Microorganisms
05.12.2016 | Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

High-precision magnetic field sensing

05.12.2016 | Power and Electrical Engineering

Construction of practical quantum computers radically simplified

05.12.2016 | Information Technology

NASA's AIM observes early noctilucent ice clouds over Antarctica

05.12.2016 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>