Conjugated systems ferrocenes

Reversible one-electron oxidation of ferrocene and its derivatives to cation radicals (so-called ferricenium cations) is a well-known reaction. The cation radical center is localized at the iron atom. In contrast to this statement, the hole transfers though conjugated systems were proven for the bis(ferrocenyl) ethylene cation radical (Delgado-Pena et al. 1983) and the cation radical of bis(fulvaleneiron) (LeVanda et al. 1976). Scheme 1-53 depicts these structures. 

Protonation-induced Intramolecular Electron Transfer in the Ferrocene-Quinone Conjugated System... 

The dimeric complex 39 exhibits individual Fe(III)/ Fe(II) redox couples at +0.47 and +0.60 V v. SCE in CH2CI2. The averaged value (+0.54 V) is close to that of the corresponding monomeric complex 38 (+0.51 V). These results are explained by the electronic effect as reported in the literature. The trimer 40 exhibits two redox couples at +0.51 and +0.67 V in a similar condition. The positive peak suggests the presence of significant electronic interaction between two ferrocene units (center and C-terminus). This result indicates the possibility of constructing an expanded conjugation system of polymeric ferrocene amino acid and the development of the conductive devices by partial oxidation. 

Special procedures for visualising ferrocene derivatives are unnecessary since they are coloured. Alkylferrocenes and derivatives without chromophore groups in conjugation with the ferrocene nucleus are yellow monoacylferrocenes are orange diacyl derivatives, red and decidedly conjugated systems, red-violet. Less intensively coloured ferrocene derivatives may be oxidised to blue or blue-green ferrocinium derivatives. The lower limit of detection of most ferrocence derivatives is 2-3 [xg. 

The expected protonation-induced phenomena of the ferrocene-quinone (FcQ) Ji-conjugated system are shown in Figure 3, which includes two basic and important processes of acid-base equilibrium and intramolecular PCET. The former process is the interaction of the quinonoid moieties with protic solvent or acid. The latter process can appear when the donor and acceptor levels are close and the... 

Figure 3. Differential Pulse Voltammetry profile obtained at a platinum microsphere for a MeCN solution of the conjugate system FcS02[Nill(cyclam)](C104)2, 8. The less anodic peak refers to the one-electron oxidation of the ferrocene moiety, the more anodic one corresponds to the Ni to Ni oxidation process taking place in the metallocyclam fragment.

Figure 4. Electrode potentials measured for MeCN solutions of the ferrocene/metallocyclam conjugate system 8 and for related fragments.

Figure 9.4 shows a series of bis-ferrocene (bis-Fc) complexes 15-18 [12c, 16]. Electrochemistry revealed poor separation of the pseudo-two-electron oxidation, but it was possible to estimate the separation of the first and second oxidation potentials as listed in Figure 9.4. Comparing the two linearly conjugated systems...

REDOX CHEMISTRY AND FUNCTIONALITIES OF CONJUGATED FERROCENE SYSTEMS... 

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