Title:	Design of molecular motors powered by visible light
DNr:	LiU-2017-00089-7
Project Type:	LiU Compute
Principal Investigator:	Bo Durbeej <bo.durbeej@liu.se>
Affiliation:	Linköpings universitet
Duration:	2017-03-07 – 2022-04-01
Classification:	10407
Homepage:	http://old.liu.se/forskning/foass/bo-durbeej
Keywords:

Abstract

Molecular motors are molecules that can perform work by absorbing energy and converting the energy into directed mechanical motion like rotation around a chemical bond. Because of their ability to execute a number of useful functions, such as rotating objects thousand-fold heavier than themselves, it has long been recognized that molecular motors have enormous potential for a wide variety of applications in nanotechnology and medicine. Fittingly, the 2016 Nobel Prize in Chemistry was awarded to three scientists who have made outstanding contributions to the design and synthesis of molecular motors. In the last few years, we have initiated a line of research unique to Swedish academia in which more powerful molecular motors are designed from in silico modeling in the field of theoretical chemistry. Specifically, we have focused on finding ways to further improve the performance (i.e., the rotational frequencies) of the synthetic molecular motors developed from so-called overcrowded alkenes by Nobel Laureate Ben Feringa and his group. These motors use UV light and heat to produce rotary motion that under favorable circumstances may reach the MHz regime. In our work, we have performed quantum chemical calculations to identify a number of different strategies for bringing the rotational frequencies of overcrowded-alkene motors into new territory, beyond the MHz regime (see, for example, Phys. Chem. Chem. Phys. 2015, 17, 21740 and ChemPhysChem 2016, 17, 3399). Such rate acceleration is a prerequisite for many of the applications currently envisioned for molecular motors. However, it is also desirable to design entirely new motors that do not require UV light for their function but rather produce rotary motion by using visible light as the input energy source. This holds true particularly for applications in medicine, because visible light is much less harmful to human tissue than UV light. In this regard, it is certainly unfortunate that the most efficient synthetic motors developed to date are all powered by UV light. To rectify this situation, we will in the present project investigate how a recent UV-light-driven motor designed in our laboratory (see Phys. Chem. Chem. Phys. 2017, DOI: 10.1039/c6cp08484b) should be modified in order for it to rather be powered by visible light. One of the most appealing features of this motor design is that it produces rotary motion in a purely photochemical fashion and thus functions perfectly well even at low temperatures. The approach that will be taken to make our motor design work also when subjected to visible light is to increase the number of conjugated double bonds in the motor. From the viewpoint of the non-adiabatic molecular dynamics (NAMD) simulations through which the photochemical processes will be modeled, however, this approach is costly in that the required ab initio description of the photoactive excited state becomes increasingly more complex with each added double bond, even if the size of the motor does NOT increase. This is why the project needs additional HPC allocations to complement those that we currently have access to.