A DFT study on spring property of helicenes

Abstract

This study focuses on investigating the spring properties of helicenes through DFT theoretical calculations. The energy change during stretching was observed by incrementally scanning the distance between both ends of the helicene from its stable state. The stiffness (k value) of each helicene was also determined at different stretching states. Interestingly, the k value was found to be non-constant during stretching, suggesting that helicenes do not behave as ideal springs. Furthermore, the effects of heteroatom doping and lateral π-extension on [6]helicene were examined, indicating that these factors have minimal impact on the spring nature of helicenes. Additionally, the study extended to longer helicenes, namely [12] and [18]helicenes. It was observed that the stiffness at the middle part of the helicene is greater than at the terminal parts, and the helical structures begin to collapse when the stretching length reaches approximately 2.5 times the stable state. We expected this work could bring innovative concept in future design of molecular devices.