Redox-controlled switching

Figure 6.10 Palindromic rotaxane 118+ and redox-controlled switching between its contracted and extended forms.

Figure 10.8. The redox-controlled switching of the [2]pseudorotaxane [1 13] 4PF6 and the partial H-NMR spectra [400 MHz, CD3CN/D20 (95 5), 25°C] of an equimolar mixture of 1 4PF6 and 13 (a) after complexation, (b) after oxidation and decomplexation, and (c) after reduction and complexation. The bipyridinium hydrogen atoms (H j in the a-positions with respect to the nitrogen atoms were used as the probe protons and (co) and (un) stand for complexed and uncomplexed species, respectively.

Figure 10.11. The redox-controlled switching between the [2]pseudorotaxanes M-9MPF and [1 17] 4PF and the absorption and emission spectra of an equimolar mixture of 1 4PF6, 9, and 17 (a la ) after the formation of [1 17] 4PF6, (bW) after oxidation and guest exchange, and (c lc") after reduction and guest exchange.

Figure 10.12. The redox-controlled switching between the [2]pseudorotaxanes...

Figure 10.16. The redox-controlled switching of the [2]rotaxane 20 4PF6.

Figure 10.24. The redox-controlled switching of the [2]catenane 31 4PF6 and the absorption spectra (MeCN, 25°C) of 31 4PF6 (a) before oxidation, (h) after oxidation and rotation, and (c) after reduction and rotation.

The redox-controlled mechanical switching in SAMs of disulfide-functionalized bistable TTF-DMN rotaxanes consisting of cyclophane 124+ and a dumbbell-shaped component containing TTF and DMN stations was also extensively investigated.49... 

Photoinduced electron transfer processes involving electron donor (D) and acceptor (A) components can be tuned via redox reactions. Namely, the excited-state properties of fluorophores can be manipulated by either oxidation of electron donors or reduction of electron acceptors. Also, the oxidized and the reduced species show different properties compared to the respective electron donors and acceptors. By making use of these properties of electron donors and acceptors, a number of molecular switches and logic gates have been described in recent years. In the following, we will introduce these redox-controlled molecular switches according to the redox centers. 

The efficient on/off switching of fluorescence from substituted zinc porphyrin-ferrocene dyads 16a and 16b is achieved through redox control of the excited-state electron transfer quenching.26 This redox fluorescence switch is based on the switching of the excited-state electron transfer from the ferrocene to the zinc porphyrin through the use of the ferrocene/ferrocenium (Fc/Fc +) redox couple. 

Scheme 15.8 The photo- and redox-controlled fluorescence switch based on bis-thiaxanthy-lidenes 49 and 50.

Applying this new exciting transition metal dtc-based catenane high yielding synthetic procedure to the construction of novel redox-controlled molecular machines and switches is the subject of ongoing research within the group. 

R. Rathore, P. LeMagueres, S. V Lin-deman, J. K. Kochi, A Redox-controlled Molecular Switch Based on the Reversible C—C Bond Formation in Octa-methoxytetraphenylene, Angew. Chem. Int. Ed. 2000, 39, 809-812. 

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