Periodic Reporting for period 1 - RedSwiMot (Redox-driven Switches and Motors)
Période du rapport: 2022-09-01 au 2024-08-31
Molecular switches and machines – the tiniest analogues of macroscopic machinery – have the potential to generate enormous impact across multiple scientific and technological applications. This includes, among others, smart materials, soft robotics, energy storage, advanced (molecular) computing, biomedicine and many more. However, this large application scope has only been partially explored. The by far most commonly used energy input to control molecular switches and machines remains light, as it is a convenient source of energy in many applications and can be applied with high spatiotemporal control. This has resulted in the development of numerous photoswitches and light-driven motors and their proof-of-principle applications. In contrast, control of such systems via electrochemical stimulation (i.e. redox) remains much less explored, in spite of its appeal in applications where light may not be an ideal stimulus (for example in opaque environments or at the interface with existing electrical nanotechnologies). This can in part be attributed to the relative lack of redox-active switches that undergo well-defined geometric changes with high reversibility. One such switch is the overcrowded alkene bisthioxanthylidene (BTX), a fatigue-resistant light and redox-responsive multi-state switching scaffold. The objective of this project was to further investigate the fundamental (redox) switching properties of BTX and novel derivatives thereof and to elucidate important design principles of this class of switches. This improved understanding is expected to contribute to the development of the next generation of redox-switches with numerous potential applications such as those listed above.
The project was implemented by successfully synthesising a series of (novel) BTX switches via multi-step synthetic organic chemistry. All systems were then analysed in detail by numerous different analytical techniques, including, but not limited to nuclear magnetic resonance spectroscopy, ultraviolet–visible spectroscopy, fluorescence spectroscopy, X-ray crystallography and detailed electrochemical characterisation. The latter encompassed advanced voltametric studies including low-temperature experiments as well as spectroelectrochemistry. These detailed studies into the switching and conformational properties of the BTX family of switches revealed numerous new insights into their synthesis and switching behavior, which has/will result in multiple high impact peer-reviewed publications in international scientific journals. In addition, various proof-of-concept applications including multi-state switching of ion recognition (and sensing of ions) were successfully demonstrated for the first time using this switch system. Furthermore, the study of the chiral properties of BTX switching systems revealed unexpected novel chiral switching mechanisms and will aid in the further development of these scaffolds in redox-driven molecular machines and motors.
The main results of the project are the successful development of an expanded toolbox of geometric redox switches and a significantly enhanced understanding of their switching properties. This includes a more detailed understanding of their redox, optical and structural properties and how to tune them. This is of immediate fundamental scientific relevance to a broad research community interested in molecular switches/machines, supramolecular chemistry and organic electrochemistry. In addition, various proof-of-principle applications of these switches are now within reach, which will enable numerous follow up scientific studies.