How Does the Flexibility of Molecules Affect the Performance of Molecular Rotors?

Abstract

In research on molecular machines, the flexibility of the molecules has been shown to significantly affect the performance of such "soft" machines and thus lead to unexpected phenomena that differ from rigid machines in the macroscopic world. Taking several typical rotational molecules as examples, we examine how the deformation of the molecule (commonly caused by curving parts of a molecule due to its interaction with other molecules) affects the effectiveness of a molecular machine system, such as a chain of molecular gears. From the viewpoint of quantum chemistry and classical mechanics, we introduce a torque analysis strategy to quantitatively analyze the strength of the repulsion/attraction force induced by the deformation of such molecules. By comparing different types of chemical bonds, we show that a bond connecting to an aromatic ring exhibits a larger stiffness than bonds that do not directly connect to an aromatic ring. We thereby highlight that the inclusion of aromatic rings in a molecular machine can considerably increase the stiffness of the machine, which is an important factor in designing effective molecular machines.

Mechanical Transmission of Rotational Motion between Molecular-Scale Gears

“…Although mechanical transmission involving up to three molecule-gears [22] as well as collective rotations have recently been observed [23,24], it is still unclear how to design single molecule-gears in order to control mechanical rotations along a long train of molecule-gears. Several calculations using density functional theory (DFT) have been performed trying to establish specific design rules concerning, for example, the axle stability or the gear teeth flexibility [25][26][27][28]. However, there are many open questions about how molecule-gears must be individually stabilized on a surface and how they must mutually interact in a long train of gears for the mechanical transmission of motion to occur along the train.…”

Structures and internal dynamics of diphenylether and its aggregates with water

“…As such, characterization of structural flexibility can be relevant when trying to understand the function of molecules, be it in chemical reactions or biological environments, for example. [1][2][3][4][5] It is well known that structure and structural flexibility can be largely influenced by their environment, namely by interactions with other molecules. In some cases, the energy order of conformers of a specific molecule is significantly altered upon complexation with other species.…”

Multi-functional switch effect in interlocking molecular rotators-on-graphene systems using electric fields

“…The flexibility of different side groups serving as gear arms (without an electric field) for similar gear molecules has been studied recently, indicating that the C 6 (CN) 6 molecule is a good choice as a model gear system for the study of the effects of an applied electric field. 64,65 Using DFT calculations, we can obtain the total energy to evaluate the stability of the system, as shown in Fig. 3a.…”