An odd couple: Photoluminescent liquid crystals based on metal clusters

Apr 30, 2010

(PhysOrg.com) -- Combine liquid crystals (mesogens) and metal clusters and you get clustomesogens -- a new class of compounds, the first examples of which have now been produced by scientists at the Universities of Rennes (France) and Bucharest (Rumania). As the team headed by Yann Molard and Stephane Cordier reports in the journal Angewandte Chemie, when irradiated, the material glows intensely in the red and infrared range.

Liquid crystals are familiar from LC displays. These materials behave like something between a liquid and a solid. On one hand, their molecules are oriented and partially ordered like in a crystal; on the other, they are not rigid, but truly mobile, like in a liquid. When a voltage is applied, liquid crystals can be switched between different states.

Another class of materials of interest to the optoelectronics field is metal clusters. Clusters are aggregates of a few atoms. Such clusters of metal atoms show unusual electronic, magnetic, and that arise from the metal-metal bonds in the cluster, and the properties are completely different from those of macroscopic metal particles. The team was able to unite the interesting characteristics of both types of material in the form of a new class of materials called clustomesogens, which contain metal clusters in a liquid-crystalline phase.

Liquid crystals with metal-metal bonds have been rare and limited to species with only two connected metal atoms. The scientists have now constructed a that contains octahedral clusters made of six atoms. For stabilization, there are eight bromide ions coordinated as ligands above the eight surfaces of the octahedron. The researchers attached special organic ligands to the six corners of the octahedron. These ligands are aromatic rings, each equipped with three long hydrocarbon chains, the ends of which are also made of two aromatic rings. Simple warming triggers a self-organization process by which the clusters stretch out to form long, narrow units (see figure) arranged in a lamellar structure. The flat rings at the ends of the ligands of neighboring layers are interleaved; this structure has liquid-crystalline properties.

The material shows strong luminescence in the red/near infrared range when excited over a broad range of wavelengths, and this type of material may be useful for the production of red displays and infrared signals. The new class of compounds has been patented in the USA in November 2009 as no. 61/264888.

Explore further: Recycling industrial waste water: Scientists discover a new method of producing hydrogen

More information: Yann Molard, Clustomesogens: Liquid Crystal Materials Containing Transition-Metal Clusters, Angewandte Chemie International Edition 2010, 49, No. 19, 3351-3355, dx.doi.org/10.1002/anie.201000325

Related Stories

When liquid crystals with a metal center are 'shaking hands'

Mar 14, 2005

Without liquid crystals (LC's) our cell phones and notebook computers would not be possible, for these compounds keep our display screens flat and lightweight. Being a phase of matter whose order is intermediate between that ...

Crystal to glass cooling model developed

Feb 22, 2006

University of Tokyo scientists have discovered why cooling sometimes causes liquid molecules to form disordered glasses, rather than ordered crystals.

Recommended for you

A greener source of polyester—cork trees

6 hours ago

On the scale of earth-friendly materials, you'd be hard pressed to find two that are farther apart than polyester (not at all) and cork (very). In an unexpected twist, however, scientists are figuring out ...

A beautiful, peculiar molecule

9 hours ago

"Carbon is peculiar," said Nobel laureate Sir Harold Kroto. "More peculiar than you think." He was speaking to a standing-room-only audience that filled the Raytheon Amphitheater on Monday afternoon for the ...

Metals go from strength to strength

Apr 15, 2014

To the human hand, metal feels hard, but at the nanoscale it is surprisingly malleable. Push a lump of metal with brute force through a right-angle mould or die, and while it might look much the same to the ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Skeptic_Heretic
not rated yet Apr 30, 2010
Transparent aluminium on its way.

Gene Roddenberry, you really were a visionary.

More news stories

Breakthrough points to new drugs from nature

Researchers at Griffith University's Eskitis Institute have developed a new technique for discovering natural compounds which could form the basis of novel therapeutic drugs.

A greener source of polyester—cork trees

On the scale of earth-friendly materials, you'd be hard pressed to find two that are farther apart than polyester (not at all) and cork (very). In an unexpected twist, however, scientists are figuring out ...

A beautiful, peculiar molecule

"Carbon is peculiar," said Nobel laureate Sir Harold Kroto. "More peculiar than you think." He was speaking to a standing-room-only audience that filled the Raytheon Amphitheater on Monday afternoon for the ...

Researchers see hospitalization records as additional tool

Comparing hospitalization records with data reported to local boards of health presents a more accurate way to monitor how well communities track disease outbreaks, according to a paper published April 16 in the journal PLOS ON ...

Ebola virus in Africa outbreak is a new strain

Scientists say that the Ebola (ee-BOH'-lah) virus that has killed scores of people this year in Guinea (GIH'-nee) is a new strain. That means it did not spread there from outbreaks in some other African nations.