Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

Abstract

With the rise of artificial molecular machines, control of motion on the nanoscale has become a major contemporary research challenge. Tetrathiafulvalenes (TTFs) are one of the most versatile and widely used molecular redox switches to generate and control molecular motion. TTF can easily be implemented as functional unit into molecular and supramolecular structures and can be reversibly oxidized to a stable radical cation or dication. For over 20 years, TTFs have been key building blocks for the construction of redox-switchable mechanically interlocked molecules (MIMs) and their electrochemical operation has been thoroughly investigated. In this review, we provide an introduction into the field of TTF-based MIMs and their applications. A brief historical overview and a selection of important examples from the past until now are given. Furthermore, we will highlight our latest research on TTF-based rotaxanes.

Chiroptical inversion of a planar chiral redox-switchable rotaxane

“…Large-amplitude motion and co-conformational changes in (oligo)rotaxanes were triggered by redox chemistry. 38,[42][43][44][45][46][47][48][49][50] Apart from rotaxanes, TTF derivatives with covalently bound chiral substituents exhibited a chiroptical response to a change of their redox-state. [51][52][53][54][55][56][57] Hence, our switchable rotaxanes display ideal optoelectronic properties since they are air stable in their neutral and oxidised form and show a clear-cut optical output, 37 which is even visible by the naked eye.…”

Isolation and characterisation of a stable 2-azaphenalenyl azomethine ylide

“…The CV of 7b in DCM contains three redox waves associated with irreversible oxidation (+0.56 V), reversible oxidation (−0.68 V) and irreversible reduction (−2.06 V), which correspond to the following transformations: Table 1). The E 1 ox value (−0.68 V) is extremely high for a neutral compound especially when considering the fact that the typical electron donor tetrathiafulvalene (TTF) 29 has an oxidation potential of +0.37 V. Moreover, the high E 1 ox value of 7b explains its high reactivity toward oxygen. Finally, the HOMO-LUMO energy gap, estimated using redox potential data) is comparable to that of absorption edge of 7b (1.51 eV/823 nm) ( Supplementary Fig.…”

Electrochemically switchable rotaxanes: recent strides in new directions

“…101 Furthermore, few supramolecular construction motifs have proven to be particularly reliable for introducing electrochemical switching into rotaxanes, e.g. viologens 102 and tetrathiafulvalenes, 103 which provide stable and persistent redoxswitchable building blocks. The improvement of these functional groups and the development of novel yet functionally similar redox-switches are of major signicance for future growth of the eld.…”