Ferrocene redox chemistry

It was also found that the hybridization kinetics were found to be faster in a moving sample, as compared to a stationary sample [939]. In another report, active acoustic mixing was used to achieve a five-fold faster DNA hybridization rate. Hybridization was detected electrochemically (by AC voltammetry) based on the ferrocene redox chemistry [62],... 

REDOX CHEMISTRY AND FUNCTIONALITIES OF CONJUGATED FERROCENE SYSTEMS... 

Redox Chemistry and Functionalities of Conjugated Ferrocene Systems Hiroehi Nishihara... 

Figure 6.31 Schematic representation of a glucose sensor operating with ferrocene to mediate the redox chemistry of glucose oxidase (GOD).

The interesting redox chemistry of such conjugated polymeric metallocene systems has been reviewed [121]. For example, oligo(l,ll -dihexylferrocenylenes) 61 show an intervalence charge transfer band (IVCT) on oxidation. For the singly oxidized chains, the IVCT band zmax decreases as the number of ferrocene units increases, as expected. Also, as expected the energy of the IVCT band increases as the oxidation level increases. 

Complex chemistry of cyclophanes links the two best examined two-layered molecules of organic and organometallic chemistry, namely [22 ]para-cyclophane and ferrocene. The rich redox chemistry of ruthenium, cobalt, rhodium and iridium therefore provides a basis for constructing polymeric structures, of which some oligomeric building units are already known. 

Ferrocene has been by far the most used redox-active group in a supramolecular sensor due its stability, its ease of functionalization and its well-understood and reversible redox chemistry. A host of feiTOcene-contain-ing compounds are now known that bind cations anions, and neutral molecules. It can be argued that the first examples of redox-active receptors, for which the complexation of other species was demonstrated, were ferrocenyl crown ether compounds, as reported in the late 1970s and in 1980. " However, it was not until... 

The basic concept of the most common form of electrochemical investigation of the redox chemistry of a coordination compound is that voltammetric data are initially collected and a mechanism for the half-cell reaction that occurs at the working electrode is postulated. A simple process, often used as a voltammetric reference potential standard, would be (Equation (1)) oxidation of ferrocene (Fc) to the ferrocenium cation (Fc ) in an organic solvent (acetonitrile, dichloromethane, etc.) containing 0.1 M of an electrolyte such as BU4NPF6 (added to lower the resistance) ... 

The oxidized conducting polymer can work as an electrode for redox chemistry just as a metal does. For example, solution species such as ferrocene and hydro-quinone can be oxidized or reduced at polypyrrole [52] and other polymeric electrodes. The redox reaction of solution species has been found to be more facile at thin films than at thicker films, implying that morphology changes are important. 

Because of its insolubility, redox potentials of SmCp2 are difficult to obtain. However, electrochemical reduction of (C5H5)3Sm in THF at mercury, gold and platinum electrodes have been used to estimate the redox potential (Bond et al., 1986). The E1/2 value was found to be —2.66 V vs. ferrocene/ferrocenium redox couple. The redox potential is considerably more negative than for the reduction of Sm(III) in water (Morss, 1976) indicating the impact of the Cp ligand on Sm(II) redox chemistry. 

The same reasons for the interest in incorporating ferrocene units into polymers also provided motivation for the synthesis of dendritic macromolecules of well-defined size and structure containing ferrocenyl units. An important additional rationale for the construction of ferrocenyl dendrimers is provided by the fact that such macromolecules raise the possibility of combining the unique and valuable redox properties associated with the ferrocene nucleus with the highly structured macromolecular chemistry. This may provide access to materials of nanoscopic size possessing unusual symmetrical architectures, as well as specific physical and chemical properties which would be expected to differ from those of the ferrocene-based materials prepared to date. 

In addition to ferrocene, the oxidative redox couple that has received the most attention in supramolecular chemistry is tetrathiofulvalene (TTF), 35. This compound undergoes two reversible one-electron oxidations, first to a radical cation and then to a dication (Eq. 1.21). TTF first came to prominence in the 1970s when it was discovered that the charge transfer complex between it and 7,7,8,8-tetracyanoquinonedimethane (TCNQ) shows metallic conductivity. As a result, a large variety of different TTF derivatives have been prepared and characterized. This rich synthetic chemistry, coupled with the electroactivity, has intrigued supramolecular chemists for some time, with the result that the TTF unit has been incorporated into a wide variety of... 

The organometallic ferrocene moiety is an attractive redox center to integrate into macrocyclic polyether ligands because, apart from its established functional group organic chemistry, ferrocene itself is elec-trochemically well behaved in most common solvents undergoing a reversible one-electron oxidation (43). 

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