Theoretical research of covalent and controllable molecular brake based on 9-triptycene

In order to understand the mechanism of molecular brake more clearly, the brake system (3-(9-triptycyl)-6,6′-dimethoxy-2,2′-bipyridine) was studied in computational methods using the density functional theory (DFT). The M06-2X functional is used to obtain various parameters of the molecules. The relaxed potential energy surface scans were performed to obtain the minimum energy profiles (MEPs). The ground state and transition state during rotation are accurately found, and then a lot of thermodynamic data are obtained and analyzed. For the purpose of proving the occurrence of rotation motion, the transition state theory (TST) was used to investigate the kinetic properties. The Boltzmann statistics was used to analyze the conformer populations, which can also explain some thermodynamic properties of molecular brake. Based on these results, the braking mechanism was pointed out: The rotation of triptycene (Tp) rotor was suppress by a chemical method, to terminate the motion completely, the temperature was lowered appropriately. The molecular dynamics (MD) simulations of the ground states and transition states were also carried out to further verify the rationality of the mechanism. Comparing with the experimental results, the conclusions were figured out.