Midway evaluation in Chemistry - Ivan Tambovtsev
Title: Calculations of molecular motors based on optical excitations of chiral molecules in liquid crystals
Doctoral candidate: Ivan Tambovtsev
Hannes Jónsson, Professor at the Faculty of Physical Sciences, University of Iceland
Elvar Örn Jónsson, Research associate, Science Institute of UI
Tatiana Orlova, Associate professor, ITMO University St. Petersburg
Sergei Egorov, Professor, University of Virginia, Charlottesville, USA
Theoretical calculations are carried out to analyse and predict the performance of molecular motors based on optical excitations of chiral molecules embedded in liquid crystals. The relaxation time of various motors is determined by identifying the minimum energy path between the different states of the chiral molecules. Tuning of the time scale of the dynamics using substitution of atoms such as the replacement H atoms with F atoms, is considered and trends analysed and predicted. Comparison with available experimental data on second-generation motors shows excellent agreement with the calculated results. As an example, the calculations show that CF3 substitution for CH3 in one place increases the transition rate, while F substitution for H in another place decreases it. These opposite effects of the two types of fluorine substitutions enable bidirectional tuning of the lifetime of the metastable state. An explanation of these observations is proposed based on the impact of the two types of fluorine substitutions on the stable, metastable, transition states and electronic structures of the motors. Future work will involve calculations of the optical excitations, including excited state dynamics.