Researchers Seek To Create Conducting Crystals From Non-Metallic Materials

FAYETTEVILLE, Ark. - A University of Arkansas researcher and his colleagues have collaborated to create non-metal materials that conduct electricity. Their research may lead one day to the use of lightweight, inexpensive, non-metal materials in electronic circuits.

Wally Cordes, University Professor of chemistry and biochemistry, will present a paper at a symposium on crystal engineering at the American Chemical Society’s southeast-southwest regional meeting in New Orleans on Dec. 7. The paper is based on his work and that of his colleagues, Richard Oakley of the University of Waterloo, Canada, and Robert Haddon of the University of California, Riverside, in crystal engineering.

The three researchers modify and study molecules containing nitrogen-sulfur free radicals, which have an unpaired electron, yet remain stable. The unpaired electron has the potential to allow the material to conduct electricity, given the right structure.

"For electrical conductivity you need electrons to move through the material," Cordes said. "If the material is going to conduct, an electron must move from one molecule to the next."

To determine an optimal conducting structure for nitrogen-sulfur free radicals, Oakley creates different crystalline forms of the molecules, and Cordes uses X-ray crystallography to determine their exact structures. Cordes takes a tiny crystal and bombards it with X-rays to determine the distance between molecules. The X-rays create a diffraction pattern - dark and light spots on a computer screen that resemble a star map. Using sophisticated computer programs, Cordes can then determine how the molecule is built, the distances and bond angles between atoms, and how the molecules pack to form a crystal. Haddon then tests the crystal for its electrical properties.

Knowing the structure and the electrical properties, the scientists can then determine the direction of their next experiment, maximizing the potential for increasing conductivity within the molecule.

So far, the trio has created molecules that conduct about as well as mercury, a moderately good conductor, Cordes said.

Editor’s note: The paper is titled: "Structural aspects of the Products of a Property-Oriented Synthetic Program Designed for Molecular Metals Based on Sulfur-Nitrogen Radicals."

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