Ferrocenes, electrochemical behavior polymers

The electrochemical behavior of ferrocene-based polymers [15] and of complexes containing a large, well defined number of ferrocene-type units [16] had already been reported when several groups became interested in dendrimer research. In the past few years several dendrimers of different chemical nature and structure carrying ferrocene-type units in the periphery have been synthesized... 

The presence of at least one alkyl group on the cyclopentadienyl motif is required to induce solubility in these poly(ferrocenylene persulfide)s. These polymers show two reversible oxidations. This type of electrochemical behavior is fairly common in ferrocene polymers where the ferrocene units are separated by short spacers as will be pointed out in the next section. 

Poly(ferrocenylsilane)s have been investigated extensively in terms of their electrochemical behavior. The general observation of these investigations is that under cyclic voltammetric conditions these polymers show two reversible oxidation (Fe(II)/Fe(III)) peaks separated by a AE1/2 that varies from about 0.16 to 0.29 V. The observation of two oxidation peaks has been explained as two successive events where the first oxidation involves a set of alternate ferrocene units followed by the second oxidation of the other alternate set. The second oxidation occurs at a higher potential than the first one [3,7]. 

Like their isoelectronic ferrocene counterparts, cobaltocenium units are resistant to strong oxidizing agents and possess interesting electrochemical behavior. The synthesis of polyesters and polyamides containing cationic cobalt units in the main chain has been reported (32,74-76). Sheats and Carraher reported the synthesis of cobaltocenium polymers containing tin, antimony, titanium, and zirconium atoms in their backbone via the reaction of the dicarboxylic... 

Ferrocene units were tethered to electrodes by telechelic poly(ethylene oxide) [579] and showed preferential adsorption of pyrene end groups to highly oriented pyrolytic graphite [580]. Ferrocene-based polymer brushes were grafted from conducting surfaces, which imparted special electrochemical behavior [581-584] e.g., the interaction of these surfaces with cyclodextrin could be modulated by electrochemical means (Fig. 51) [583, 585]. 

Zhang W, Chen M, Diao G (2011) Preparation and electrochemical behavior of water-soluble inclusion complex of ferrocene with beta-cyclodextrin polymer. Electrochim Acta 56 5129-5136... 

Aoki A, Miyashita T (1996) Electrochemical behavior of hetero-deposiled redox polymer Langmuir-Blexlgett films with ferrocene and tiis(bipyridine)ruthenium derivatives. Chem Lett 25(7) 563-564... 

Ferrocenyl-based polymers are established as useful materials for the modification of electrodes, as electrochemical biosensors, and as nonlinear optical systems. The redox behavior of ferrocene can be tuned by substituent effects and novel properties can result for example, permethylation of the cyclopentadienyl rings lowers the oxidation potential, and the chaige transfer salt of decamethylfer-rocene with tetracyanocthylene, [FeCpJ]" (TCNE], is a ferromagnet below = 4.8 K, and electrode surfaces modified with a pentamethylferrocene derivative have been used as sensors for cytochrome c These diverse properties have provided an added impetus to studies on ferrocene dendrimers. 

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