1260159-82-7Relevant academic research and scientific papers
Pentiptycene-derived light-driven molecular brakes: Substituent effects of the brake component
Sun, Wei-Ting,Huang, Yau-Ting,Huang, Guan-Jhih,Lu, Hsiu-Feng,Chao, Ito,Huang, Shou-Ling,Huang, Shing-Jong,Lin, Ying-Chih,Ho, Jinn-Hsuan,Yang, Jye-Shane
, p. 11594 - 11604 (2010)
Five pentiptycene-derived stilbene systems (1R; R = H, OM, NO, Pr, and Bu) have been prepared and investigated as light-driven molecular brakes that have different-sized brake components (1Hrot = 108-109 s-1) with little interaction with the brake component in the trans form ((E)-1R), which corresponds to the brake-off state. When the brake is turned on by photoisomerization to the cis form ((Z)-1R), the pentiptycene rotation can be arrested on the NMR spectroscopic timescale at temperatures that depend on the brake component. In the cases of (Z)-1NO, (Z)-1Pr, and (Z)-1Bu, the rotation is nearly blocked (krot = 2-6 s-1) at 298 K. It is also demonstrated that the rotation is slower in [D6]DMSO than in CD2Cl 2. A linear relationship between the free energies of the rotational barrier and the steric parameter A values is present only for (Z)-1H, (Z)-1OM, and (Z)-1NO, and it levels off on going from (Z)-1NO to (Z)-1Pr and (Z)-1Bu. DFT calculations provide insights into the substituent effects in the rotational ground and transition states. The molar reversibility of the E-Z photoswitching is up to 46%, and both the E and Z isomers are stable under the irradiation conditions.
