Biradical-Like Reactive Intermediates

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The Chemical Structure, Dynamics and Mechanisms B Program in the Division of Chemistry supports Professor Josef Michl of the University of Colorado at Boulder for investigation of previously unknown relaxed geometrical structures of peralkylated oligosilanes in their lowest singlet excited state, which are responsible for observed blue and green emissions in such compounds. These structures contain one silicon atom in a trigonal bipyramidal geometry or two silicon atoms at geometries half-way between tetrahedral and trigonal bipyramidal, and their silicon atoms carry five instead of the usual four "valence" orbitals. The calculated structures have implications for electronic excitation and electron conduction in silicon nanoparticles and all saturated molecules, but this requires experimental verification. A second independent project deals with the chemistry of the icosahedral carborane cage CB11. It is proposed to prepare new reversible anion/radical couples of potential interest as components of new hole conductors, and to examine the reactivity of such cages when they contain a naked boron vertex. The proposed research is especially relevant for solar energy conversion in solar cells and for photonics (for example, understanding light emission in silicon nanoparticles that may be used in television and computer displays). To date, several theoretical predications have yet to be tested, and the work in this award will provide much-needed experimental verification. The work will provide graduate students and postdoctoral research associates with excellent training in both synthetic organic and experimental physical chemistry.