Intellectual Merit. Professor Michl and his collaborators will work on reactive intermediates, new reactions, and new structures in the area of alkylated derivatives of the icosahedral carborane cage CB11 and will examine their broader implications. They will investigate the scope and mechanism of new reactions that were discovered in the current grant period, apply new techniques for the characterization of their intermediates, elucidate the observed substituent effects on carbon acidity and explore a new group of compounds in which a main group metal is attached to the cage carbon. They will pursue the synthesis of novel oligomeric structures that ultimately promise facile three-dimensional hole hopping and could be useful as a source of a new kind of conducting polymers. Finally, they will pursue the use of especially inert anions derived from the CB11 cage by partial trifluoromethylation and partial fluorination for the production and characterization of simple cations that may be known from gas phase studies but lie beyond the current horizon of solution chemistry of isolable compounds, such as H3+, SiH5+, SiH3+, or Zn2++. Broader Impacts. The project involves undergraduate, graduate, and postdoctoral students and will take place in a research group that has traditionally promoted the education of women and active international contacts and is highly interdisciplinary in scope. Collaboration with physicists has been common and the presently proposed work involves organic, inorganic, physical, and theoretical chemistry. The group's activities include many international collaborations, and each graduate student is expected to spend a few months performing research abroad. Workshops and conferences will be organized, some abroad. The activities have traditionally involved collaborations with industry and national laboratories and will continue to do so. The results will be broadly disseminated. The PI is the editor of a major review journal, for which he also often writes contributions. Traditional journal publication of articles and reviews is complemented by articles in trade journals. In addition to lecturing to professionals, the PI and group members give public lectures and lectures to K-12 students, domestically and abroad, on the radio and TV. Some of the international activity occurs in the Czech Republic, the PI's country of origin, where he has a part-time appointment. General benefits to society go well beyond the training of competent scientists. Some of the past scientific discoveries have been taken up by industry (Li+ catalysis of alkene polymerization, for example), and it is expected that some of the efforts proposed presently will as well (possibly new kinds of electrically conducting solids for solar cell or molecular electronics, and possibly new materials for the production of plastic electronics).
Description of Project Outcomes Intellectual Merit. Professor Michl and his collaborators have advanced the frontiers of chemical understanding on four fronts. (i) They have prepared new icosahedral carborane anions and radicals, including what probably is the world’s strongest neutral oxidant. These materials are potentially useful for improved batteries and fuel cells, and detailed information about their properties was obtained. (ii) They have elucidated the behavior of systems composed of mutually interacting Si-Si bonds upon light absorption or addition of an extra electron, with possible implications for the theory of chemical bonding on the one hand and for the performance of amorphous silicon solar cells on the other. (iii) They have synthesized and examined new components for dipolar surface-mounted molecular rotors, of considerable interest in nanoelectronics. (iv) They have provided an answer to the question whether in solution, self-assembled molecular cages of a certain type are filled with solvent or are empty (contain a bubble). In the latter case, they would have been useful as models for certain biological structures in cell walls. In spite of initial indications that bubbles may be present, the final conclusion was that they are not. Broader Impact. Postdoctoral, graduate, and undergraduate students have received interdiscipinary and international education and training in scientific research and problem solving at the borderline of chemistry and physics and have entered the scientific work force. The new knowledge they produced in the process has been widely disseminated in writing and at scientific meetings. The work involved lively interactions with industry and national laboratories. Several international meetings and many outreach activities were organized. The principal investigator has completed three decades of service as the editor of the ACS journal Chemical Reviews, presently the highest impact journal in the field of chemistry. Brief summary The outcome of Professor Michl’s project can be organized into four categories: (i) Advances in the chemistry of carborane anions and radicals containing the icosahedral CB11 cage. These included the discovery of new anions extremely resistant to oxidation and of a radical that probably is the strongest known neutral oxidant. (ii) Progress in the theory of chemical bonding in singly-bonded systems, in particular delocalization versus localization of electronic excitation (excitons) and extra charges (polarons) and its dependence on silicon chain length and conformation. The results included the discovery of situations in which a silicon atom uses five valence orbitals instead of the usual four. (iii) Synthesis of new components for molecular machinery, specifically surface-mounted dipolar molecular rotors. A by-product of this work was a new procedure for attaching organic molecules directly to a gold surface. (iv) Finding an answer to the question whether a class of molecular cages suspected of containing voids in solution actually contains voids or is filled with solvent. Items (i) and (ii) promise to be ultimately useful in the field of sustainable energy, the former for battery electrolytes and fuel cells, the latter for the understanding of the gradual decay of the performance of amorphous silicon in solar cells upon irradiation. Item (iii) is important for nanoelectronics. Item (iv) permitted the conclusion that self-assembled structures of the type examined will not serve as a simple model for possible cavity formation in biological structures.
