Results of a theoretical examination of the effect of crystal packing on singlet fission (SF) rate are presented. For a model system (pair of ethylenes) and several known or suspected SF materials: tetracene (1), cibalackrot (2), and 1,3-diphenylisobenzofuran (3), we predict molecular pair arrangements that are especially favorable for the rate of SF. The predictions are obtained from an approximate evaluation of squares of SF eectronic matrix elements, based on a complete search of all possible pair packing geometries. This is refined by an evaluation of intermolecular contributions to the energy balance of the SF process, followed by Marcus theory evaluation of SF rates, which are used to reoptimize the best geometries. We also evaluate biexciton binding energies. Going beyond the prediction of optimal geometries, the model has been applied to a series of variously fluorinated derivatives of 3 and found to determine successfully which ones perform SF and which ones yield excimers instead. Although a consideration of molecular pairs thus appears to be a useful first step and may be sufficient in some cases, experimental evidence shows convincingly a need to consider at least three molecules at a time in the future. Evaluation of triplet yields will require an additional evaluation of rates of competing processes, especially charge separation and excimer formation.
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Ph.D.: Czechoslovak Academy of Sciences, Prague, 1965
Areas of Expertise
Inorganic, Physical, Photochemistry, Organometallic Chemistry, Organic, Physical Organic
Awards and Honors
Czechoslovak Society for Arts and Sciences, 2017, Neuron Foundation Award, Czech Republic, 2016, Hammond Award, I-APS, 2015, Boron in the Americas Award, 2014, American Chemical Society Fellow, 2010, Medal of the Institute of Organic Chemistry and Biochemistry (Acad. Sci., Prague, Czech Republic), 2012 and 2004, Fulbright Fellowship, 2006, University of Colorado Faculty Fellowship, 2006, Patria Award, Government of the Czech Republic, Prague, 2005, Honorary Doctorate, Masaryk University, Czech Republic, 2004, Marinus Smith Award, University of Colorado, 2003, Porter Medal (I-APS, EPA, JPA), 2002, Best Journal Issue Award for Chemical Reviews (Association of American Publishers), 2002, ALA Achievement Award (Association for Laboratory Automation), 2002, Otto Wichterle Award (Czech Chemical Society), 2001, James Flack Norris Award (American Chemical Society), 2001, Auburn - G. M. Kosolapoff Award (ACS Auburn Section), 2000, American Academy of Arts and Sciences, 1999, Japan Society for Promotion of Science Award, 1998, Honorary Doctorate, University of Pardubice, Czech Republic, 1996, World Association of Theoretically Oriented Chemists (WATOC) Fellow, 1996, Czech Learned Society, Honorary Member, 1995, Charles University Gold Medal, Prague, Czech Republic, 1995, J. Heyrovsky Gold Medal (Czech Academy of Sciences), 1994, IAPS Award (Inter-American Photochemical Society), 1994, Schrödinger Medal (World Association of Theoretical Organic Chemists), 1993, Arthur C. Cope Senior Scholar Award (American Chemical Society), 1993, Honorary Doctorate, Georgetown University, 1990, International Academy of Quantum Molecular Science, 1988, U.S. National Academy of Sciences, 1986, ACS Utah Section Award, 1986, John Simon Guggenheim Fellow, 1984-85, The Honor Society of Phi Kappa Phi (Member), Alexander von Humboldt Senior U.S. Scientist Award, 1980, Distinguished Research Award, University of Utah, 1978-79, Alfred P. Sloan Fellow, 1971-75