Redox active groups

R. T. Boere and T. L. Roemmele, Electrochemistry of Redox-active Group 15/16 Heterocycles, Coord. Chem. Rev., 210, 369 (2000). 

Polymer with attached redox-active groups... 

The monotonic increase of immobilized material vith the number of deposition cycles in the LbL technique is vhat allo vs control over film thickness on the nanometric scale. Eilm growth in LbL has been very well characterized by several complementary experimental techniques such as UV-visible spectroscopy [66, 67], quartz crystal microbalance (QCM) [68-70], X-ray [63] and neutron reflectometry [3], Fourier transform infrared spectroscopy (ETIR) [71], ellipsometry [68-70], cyclic voltammetry (CV) [67, 72], electrochemical impedance spectroscopy (EIS) [73], -potential [74] and so on. The complement of these techniques can be appreciated, for example, in the integrated charge in cyclic voltammetry experiments or the redox capacitance in EIS for redox PEMs The charge or redox capacitance is not necessarily that expected for the complete oxidation/reduction of all the redox-active groups that can be estimated by other techniques because of the experimental timescale and charge-transport limitations. 

Figure 11.2 Cartoon representation of Au MMPC labeled with a redox-active group phenothiazine on the NP periphery. Adapted from Ref. 16 with permission.

Electroionic signals are generated by electrochemical interconversion of a selective receptor molecule containing a redox-active group (metallocene, quinone, etc.) between states of low and high affinity for a given substrate (see Sections 6.4.1 and 8.3.1). 

Fast electrochemistry, especially for self-assembled monolayers containing redox-active groups [3-5]. 

A family of molecular rotors (e.g., compound 4 in Fig. 17.4 a) has been designed to perform rotation under electrochemical stimulation.59 60 The molecules have a piano-stool structure with a stator meant to be grafted on an oxide surface and a rotor bearing redox-active groups, so that addressing the molecule with nanoelectrodes would trigger rotation (Fig. 17.4 b). To avoid intramolecular electron transfer between two electroactive units, which would compete with rotation, insulating... 

The example considered is the redox polymer, [Os(bpy)2(PVP)ioCl]Cl, where PVP is poly(4-vinylpyridine) and 10 signifies the ratio of pyridine monomer units to metal centers. Figure 5.66 illustrates the structure of this metallopolymer. As discussed previously in Chapter 4, thin films of this material on electrode surfaces can be prepared by solvent evaporation or spin-coating. The voltammetric properties of the polymer-modified electrodes made by using this material are well-defined and are consistent with electrochemically reversible processes [90,91]. The redox properties of these polymers are based on the presence of the pendent redox-active groups, typically those associated with the Os(n/m) couple, since the polymer backbone is not redox-active. In sensing applications, the redox-active site, the osmium complex in this present example, acts as a mediator between a redox-active substrate in solution and the electrode. In this way, such redox-active layers can be used as electrocatalysts, thus giving them widespread use in biosensors. 

The redox polymers contain, as the name indeed suggests, redox-active groups that are in turn bound to the polymer s spine, as shown in Fig. 4.111. Electrons travel macroscopic distances by hopping along using the redox groups attached to the spine at points between which the hops occur. 

The reduction potential is central for the function of electron-transfer proteins, since it determines the driving force of the reaction. In particular, it must be poised between the reduction potentials of the donor and acceptor species. Therefore, electron-transfer proteins normally have to modulate the reduction potential of the redox-active group. This is very evident for the blue copper proteins, which show reduction potentials ranging from 184 mV for stellacyanin to 1000 mV for the type 1 copper site in domain 2 of ceruloplasmin [1,110,111]. 

Redox active group Protein Enzyme/protein partner... 

Maruyama and Listowsky (90) reported that ferritin from human liver, both heavy and light subunits, and horse spleen and rat liver ferritins possess fluorescence spectra in which excitation at 350 nm causes emission at 432 nm. Similar spectra (Fig. 4) have been reported for the bacterial ferritins from P. aeruginosa (100), A. vinelandii 73), and.E. coli (30). Although the fluorophor has not been identified, it has been shown to have characteristics different from those of common flavins and folates (100). Possible candidates for the identity of the fluorophor include modified amino acids, such as derivatives of tryptophan and pyridinoline, and a redox-active group, such as pyrro-loquinoline quinone or pterin. If it turns out to be one of the former groups, then the fluorescence will probably arise from oxidative dam-... 

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