FERROCENECARBOXYLIC ACID

FERROCENECARBOXYLIC ACID. 56, 28 Fluorinated aromatic compounds, 59,122 FLUORINATIONS, 58, 75... 

The ODNs used here were prepared on an automated DNA synthesizer and with the standard j6-cyanoethyl phosphoramidite coupling reaction. The ferrocenyl ODN (T12Fc) was synthesized by the coupling of amino-terminated ODN with the activated ester of ferrocenecarboxylic acid. A 16 mer ODN (el6S), which has five successive phosphorothioate units on its 5 -terminus, was synthesized using Beaucage s reagent... 

A highly selective method for determination of lipid hydroperoxides is based on the oxidation of ferrocenecarboxylic acid (201) to the corresponding ferrocenium compound (202), as shown in equation 69, followed by amperometric reduction of this complex with a GCE set at —100 mV vs. SCSE, in phosphate buffer at pH 5.5. The method is insensitive to dissolved oxygen and no interference is observed, either from reductors such as ascorbic acid (22) or uric acid (29) nor from other hydroperoxides such as H2O2 and f-BuOOH at the 1 xM concentration level. At this concentration, a slight interference is observed for cumyl hydroperoxide (27) and 2-butanone peroxide (46 4- 47). The LOD... 

Stepnicka et al. [61] have synthesized mercury(II) complexes with l -(diphenyl-phosphino)ferrocenecarboxylic acid and studied their structure and electrochemical properties. 

A useful synthetic technique involves the acylation of ferrocene with di-phenylcarbamyl chloride and aluminum chloride (50). The product, diphenyl-carbamylferrocene (X), is readily hydrolyzed to ferrocenecarboxylic acid (XI). Acylation of X followed by hydrolysis produces good yields of l -acylferrocene-carboxylic acids. 

Acylmetallocenes undergo many reactions shown by acylbenzenes (35, 87, 91, 116, 124), but a detailed discussion is not presented here. Reductions with either lithium aluminum hydride or sodium borohydride give the corresponding carbinols, while Clemmensen reduction, reduction with lithium aluminum hydride plus aluminum chloride, catalytic hydrogenation, etc., yield corresponding alkyl derivatives. Acetylferrocenes undergo a variety of base condensation reactions and can be oxidized to ferrocenecarboxylic acids without apparent oxidation of the iron atom. 

A second synthetic technique has employed either pyridine or dioxane adducts of sulfur trioxide as sulfonating agents. Both ferrocene and ferrocenecarboxylic acid have been sulfonated in this manner (61, 72). Cyclopentadienylmanganese tricarbonyl is also readily sulfonated (10). 

Carbonation and subsequent hydrolysis of either lithiated or sodiated metallocenes lead to the corresponding carboxylic acids. Ferrocenecarboxylic acid and ferrocene-1,1 -dicarboxylic acid are readily produced in this manner and can be conveniently separated by extraction of the former with ethyl ether or benzene. The reaction of metalated ferrocenes with various chlorosilanes has led to a variety of triaryl- or trialkvlsilylferrocenes (3, 28, 90). 

Several additional studies have confirmed interannular electronic interactions in ferrocene. Early investigations by Nesmeyanov and coworkers and by others demonstrated the electron-donor properties of the ferrocenyl group (71). Aminoferrocene, for example, is approximately 20 times as strong a base as aniline, while benzoic acid is several times more acidic than ferrocenecarboxylic acid. Moreover, acidities and basicities of this sort are markedly affected by substituents on the opposite cyclopentadienyl ring. 

A portion of these data is summarized in Table I, in which the acidities of a number of heteroannular ferrocenecarboxylic acids are compared. Introduction of an electron-releasing alkyl group into the unsubstituted ring lowers the acidity of the corresponding acid, while the introduction of electron-withdrawing groups increases it. 

In some related studies, Little and Eisenthal have found that a plot of similarly obtained pKA values for substituted ferrocenecarboxylic acids vs. Hammett para-sigma constants yields a satisfactory straight line (52). They have also recently measured the second-order rate constants for the esterification of a series of heteroannular substituted ferrocenecarboxylic acids with diphenyldiazo-... 

Fig. 9 Photostimulated bioelectrocatalyzed oxidation of glucose (2.5 x 10-2 M) in the presence of ferrocenecarboxylic acid (23)...

Electrochemical studies confirmed the presence of redox-active nanoparticles. Differential pulse and cyclic voltammetry studies were conducted. Cyclic voltammetry showed that the complex displays an electrochemically reversible ferrocene/ ferrocenium couple (Figure 9.6). The oxidation potential for the hybrid CPMV-Fc conjugate and free ferrocenecarboxylic acid in solution was determined E1/2 of CPMV-Fc was 0.23 V, and Elj2 of free ferrocenecarboxylic acid was 0.32 V versus the Ag/AgCl electrode, respectively. This shift is expected for the conversion of the carboxyl group of ferrocenecarboxylic acid to an amide on coupling to the virus capsid, since the amide is less electron-withdrawing. 

Figure 9.6 (a) Schematic presentation of Cowpea mosaic virus (CPMV) particles chemically modified with ferrocenecarboxylic acid (Fc) moieties via the formation of a peptide bond, (b) Cyclic voltammogram of derivatized CPMV-Fc at a scan rate v ofO.lVs-1, and linear plot of current versus (scan rate)l/2 (inset). 

Ferrocene,136 ferrocenecarboxaldehyde,137 and hydroxymethyl-and hydroxyethylferrocene138 have all been used to prepare various ferrocenylcarbohydrates. Ferrocenecarboxylic acid chloride and 1,3-O-methyleneglycerol139, 140 gave the ferrocenecarboxylate (163). 

Carbodiimides are widely used to mediate the attachment of biomarkers to polypeptides. Examples include carbodiimides with ferrocenyl substituents. Also, peptides are covalently modified with ferrocenecarboxylic acid using EDCCl and N-hydroxy-succinimide to promote the coupling to surface lysines. They also mediate the attachment of substituents to single walled nanotubes (SWNTs) and multiwalled nanotubes (MWNTs). Also, microdots are attached to virus molecules using a water soluble carbodiimide. The attachment of viral DNA to gold particles is used in the manufacture of a new type of vaccine. 

The attention towards electron transfer processes involving host-guest adducts of cyclodextrins (CDs) has become important with regard to their use as modifiers of organic electrode reactions. CDs, when added to solution or to electrode surfaces, can improve the selectivity of electrochemical synthesis. To elucidate the details of electron transfer reactions of guest molecules complexed inside CDs, the redox behavior of ferrocenecarboxylic acid in presence of jff-CD was studied, and this showed that the oxidation of the complexed ferrocenecarboxilic anion, FCA", must proceed via the dissociation of the host-guest adduct to form free FCA" which then transfers an electron to the electrode [81]. 

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