W0028

Crystal Engineering of Conducting Solids Based on Selenium-Nitrogen Radical Units. Wally Cordes, Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, Richard Oakley and Robin Hicks, Department of Chemistry and Biochemistry, University of Guelph, Guelph, Ontario, N1G 2W1, and Robert Haddon, Department of Chemistry, University of Kentucky, Lexington, KY 40506 USA

Highly conductive charge transfer salts can be formed by interactions of selenium-nitrogen-carbon heterocyclic radicals, such as the (1,2,3,5)-diselenadiazolyl radical (-CN₂Se₂), with iodine. A number of these solids have structures which possess evenly-spaced stacks of the radical-containing units at room temperature. At low temperature, however, charge density waves cause structural distortions which produce diamagnetic materials with small band gaps. One of the best conducting materials in this arena of Se-N-C heterocyclic radicals contains two of the diselenadiazolyl radical rings meta-bonded to a phenylene ring. One strategy for suppressing the metal-to-semiconductor transition involves altering the central bridging units so as to increase the lateral inter-stack interactions of the peripheral selenium atoms and thus give the solid a more isotropic dispersion. The structural and electronic results of this "crystal engineering" will be presented.