Redox-driven

Fig. 10. Representation of the mechanism of redox driven K + transport using an electron and a cation carrier. (59-Ni°) and (59-Ni ) are the oxidized and reduced form of the electron carrier, the nickel bis-dithiolene complex 59 [] and [K+] are dicyclohexyl-18-crown-6 and its K+ complex. (Cited from Ref. 59>)...

Richter OMH, Ludwig B. 2003. C)dochrDme c oxidase—Structure, function, and physiology of a redox-driven molecular machine. Rev Physiol Biochem Pharmacol 147 47-74. 

We have studied the electrochemical behavior and redox-driven mass changes for PAH-Os/PVS films immersed in solutions of salts with a common anion and different cations and a common cation and different anions [148]. The electrochemical and... 

Another redox-driven intramolecular movement involved the half-turn of one ring of an asymmetric catenane.3 The Sauvage s catenane consisted of two intertwined rings, one containing a phen fragment (2) and the other containing both a phen and a terpy fragment (3). 

Figure 2.1 A square scheme illustrating a redox-driven intramolecular motion. Species with an asterisk (Ox and Red ) are metastable and tend to rearrange to their stable topological isomer (Ox and Red).

The pioneering papers by Stoddart and Sauvage have stimulated the design of a variety of movable rotaxanes and catenanes, whose controlled motion is promoted by a redox change. In all cases, the process of the redox-driven intramolecular motion can be described by a square scheme, as illustrated in Fig. 2.1. 

There exist other types of redox-driven intramolecular motions that can be interpreted on the basis of the square scheme of Fig. 2.1 and are promoted by... 

In the most general situation, a redox-active metal ion is translocated from a given site to another site of the same molecular system, following a chemical (a redox reaction) or an electrochemical input. The redox-driven reversible translocation of a metal ion in a two-component molecular system is schematically sketched in Fig. 2.2. 

Metal Translocation Based on the Fe "/Fe" Couple The first example of redox-driven translocation of a metal center was based on the Fein/Fen couple and took place in ditopic ligands containing (i) a tris-hydroxamate compartment and (ii) a tris-(2,2 -bipyridine) compartment.5... 

Figure 2.8 Redox-driven translocation of a copper center, based on the Cu"/Cu change. The Cu11 ion stays in the tetramine compartment of the ditopic ligand 10, whereas the Cu1 ion prefers to occupy the bis-(2,2 -bipyridine) compartment. The translocation of the copper center between the two compartments is fast and reversible when carried out through the Cun-to-Cu1 reduction with ascorbic acid and Cu -to-Cu" oxidation with H202, in a MeCN solution.

Figure 2.9 Redox-driven translocation of the anion X (e.g., chloride), based on the Nin/Nim change. The nickel center acts both as an engine and as areceptor for the X anion (when in the Ni111 state). Occurrence of the reversible X translocation is afforded by the following sequence of anion affinity Nim > Cu11 > Ni11.

The occurrence of the redox-driven reversible assembling-disassembling process involving copper complexes of 16 has been verified through cyclic voltammetry experiments at a platinum electrode in a MeCN solution. Figure 2.17 shows the CV profile obtained with a solution of the double-strand helicate complex [ Cu 21 (16)212 +. 

Figure 2.16 The redox-driven disassembling of a dicopper(I) double-strand helicate complex to give two mononuclear copper(II) complexes, in which each strand behaves as a quadridentate ligand. On subsequent reduction, the two mononuclear complexes reassemble to give the helicate. The illustrated process fits well the behavior of copper complexes of 16 in a MeCN solution.

More recently, the second-generation molecular shuttle 374+ (Fig. 13.32) was designed and constructed.38 The system is composed of two devices a bistable redox-driven molecular shuttle and a module for photoinduced charge separation. In the stable translational isomer, the electron-accepting cyclophane 124+, which is confined in the region of the dumbbell delimited by the two stoppers Tj and T2, encircles the better electron donor tetrathiafulvalene (TTF) station. 

Fig. 12. Electron-cation coupled transport a redox-driven electron-cation symport consisting of an electron carrier (nickel complex) and a selective cation carrier (macrocyclic polyether). RED, potassium dithionite OX, Na3[Fe(CNft)].

Figure 3.52 Redox-driven chloride translocation in a mixed Cu/Ni complex of 3.74.

Fabbrizzi, L., Gatti, F., Pallavicini, P., Zambarbieri, E., Redox-driven intramolecular anion translocation between transition metal centres. Chem. Eur. J. 1999, 5, 682-690. 

In other work, Dandliker et al. have reported the inclusion of iron porphyrins within dendrimers to serve as functional mimics of redox-based proteins (Dandliker et al., 1994, 1995, 1997). These redox-switchable porphyrins show that the Fe3+/Fe2+ redox couple can be altered by the polarity of the surrounding environment. By changing the polarity imposed by the tightly packed branches of the dendritic core, the authors have illustrated that electrochemical behavior can be controlled by slight and subtle through-space environmental factors. These mimics may potentially model a wide variety of redox-driven enzymes and possibly provide mechanistic insights into their function. 

Metastability of a Redox-driven [2]Rotaxane SAM on Cold Surfaces... 

A Redox-driven [2]Rotaxane-based Molecular Switch Tunnel Junctions (MSTJs) Device... 

For some enzymes, especially cytochrome C, redox-driven conformational changes are believed to be important in their roles as proton pumps. Therefore, it is important to develop immobilization methods that create stable structures and orient the active center of the enzyme away from the electrode surface, yet provide... 

Valadi A, Granath K, Gustafsson L, Adler L (2004) Distinct intracellular localization of Gpdlp and Gpd2p, the two yeast isoforms of NAD+-dependent glycerol-3-phosphate dehydrogenase, explains their different contributions to redox-driven glycerol production. J Biol Chem 279 39677-39685... 

---