Ferrocene thiolates

Other metallic clusters that have been demonstrated to show the QDL effect are palladium [116, 117], silver [118] and copper [119]. Palladium MFCs capped with mixed monolayers of hexanethiolate/dodecanethiolate and ferrocene thiolate ligands are prepared in a manner similar to that employed for gold MFCs. The DPV studies exhibit a quantized charging effect but the current peaks are not as well defined as those observed for Au-MPCs. Capacitance values of the order of 0.35 aF are obtained, indicating smaller core sizes or thicker monolayer dielectrics [116]. 

The necessity of an anionic thiolate ligand was established by performing reactions with ferrocene thioethers 37 as ligands. Here, essentially racemic products were obtained. 

We describe how we prepared and characterized gold nanoparticles ( 3 nm in diameter) capped with thiolated cyclodextrins. The CD-capped nanoparticles are hydrophilic, and they bind compounds derivitized from ferrocene as evidenced by values measured by NMR spectroscopy. (Adapted from Liu et al., 2001)... 

Various redox functionalities have been appended to NP cores via thiolated redox molecules, place exchange reactions, and postfunctionalization of a MPC through amide15 or ester-forming reactions.16 The redox moieties include ferrocene,17 biferrocene, phenol, nitrobenzene, and anthraquinone, which commonly are synthesized using a gold core composition. The observed voltammetry of these redox-active units tend to exhibit similar electrochemical potentials to their free... 

The intercalation of polycyclic aromatic compounds into duplex DNA structures was used to develop nucleic acid-based electrochemical sensors.66 For example, the bis-ferrocene-tethered naphthalene diimide (16) was used as a redox-active intercalator to probe DNA hybridization.67 The thiolated probe was assembled on a Au electrode, and the formation of the duplex DNA with the complementary analyte nucleic acid was probed by the intercalation of (16) into the double-stranded nucleic acid structure and by following the voltammetric response of the ferrocene units (Fig. 12.17a). The method enabled the analysis of the target DNA with a sensitivity that corresponded to ca. 1 x 10-20mol. 

Scheme 11 Photochemical control of electrical contact between a ferrocene-tethered glucose oxidase and the electrode using a thiolated nitrospiropyran as a command interface.

A further approach to controlling electrical communication between redox proteins and their electrode support through a photo-command interface includes photo stimulated electrostatic control over the electrical contact between the redox enzyme and the electrode in the presence of a diffusional electron mediator (Scheme 12).[58] A mixed monolayer, consisting of the photoisomerizable thiolated nitrospiropyran units 30 and the semi-synthetic FAD cofactor 25, was assembled on an Au electrode. Apo-glucose oxidase was reconstituted onto the surface FAD sites to yield an aligned enzyme-layered electrode. The surface-reconstituted enzyme (2 x 10-12 mole cm-2) by itself lacked electrical communication with the electrode. In the presence of the positively charged, protonated diffusional electron mediator l-[l-(dimethylamino)ethyl]ferrocene 29, however, the bioelectrocatalytic functions of the enzyme-layered electrode could be activated and controlled by the photoisomerizable component co-immobilized in the monolayer assembly (Figure 12). In the... 

Ferrocenyl and ferrocenyl thiolate derivatives of the metals are heterobimetallic compounds, one component of which is iron. In principle, complex fragments of different metals may be combined with a ferrocene unit, as in the trimetallic l,T-ferrocenylene dithiolate, Cp(NO)2Cr-[S(fc)S]-W(CO)3Cp. Another versatile method to synthesize heterobimetallic complexes makes use of chelating ligands such as l,l -bis(diphenylphosphinyl) ferrocene, fc(PPh2)2 (see Chapter 1), and 1,1 -bis(methylchalcogenyl) ferrocene, fc(EMe)2 (E = S, Se), (Sect. 5.4). 

Substitution of the two diphenylphosphino substituents for thiolate groups affords a series of complexes, the structure of which is typically represented by that of dichloro[l,r-bis(ibutylsulfido)ferrocene]palladium(ii) shown in Fig. 7-53 [10]. The assembly is similar to that of the preceding bis (diphenylphosphino) complexes, except for the eclipsed and less tilted (1.9°) conformation of the cyclopentadienyl rings of the ferrocene group. 

Radi and O Sullivan recently described a similar approach wherein they attached a thiolated TEA sequence containing a redox-active ferrocene group... 

Figure 14.13. [AJ Formation of mixed SAM on Au electrode, (B) immobilization of ferrocene functionalized dendrimers (Fc-D), (C] immobilization of thiolated capture probe with bifunctional linker, (D) hybridization with target, [E] hybridization with biotinylated detection probe, (F) association with avidin-alkaline phosphatase, (G] description of the process of the electrocatal5rtic reaction of p-aminophenol Cp-AP) via electronic mediation of Fc-D.

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