Ferrocenes supramolecular structures

A further approach to electrically wire redox enzymes by means of supramolecular structures that include CNTs as conductive elements involved the wrapping of CNTs with water-soluble polymers, for example, polyethylene imine or polyacrylic acid.54 The polymer coating enhanced the solubility of the CNTs in aqueous media, and facilitated the covalent linkage of the enzymes to the functionalized CNTs (Fig. 12.9c). The polyethylene imine-coated CNTs were covalently modified with electroactive ferrocene units, and the enzyme glucose oxidase (GOx) was covalently linked to the polymer coating. The ferrocene relay units were electrically contacted with the electrode by means of the CNTs, and the oxidized relay mediated the electron transfer from the enzyme-active center to the electrode, a process that activated the bioelectrocatalytic functions of GOx. Similar results were observed upon tethering the ferrocene units to polyacrylic acid-coated CNTs, and the covalent attachment of GOx to the modifying polymer. 

The oligomers 39 have further been functionalized through introduction of redoxactive units such as viologen and ferrocene via an alkyl side chain 53 [156, 157]. The functionalization is thought to be of interest for the physical organic changes of electronic proj rties, but may also induce the formation of new supramolecular structures of well defined oligomers. The additional redox... 

Cyclodextrins, for example, form inclusion complexes with metallocenes such as ferrocene, cobaltocene and nickelocene to form crystalline compounds. The structures of the complexes are dependent on the size of the cyclodextrin. Although ferrocene and its derivatives are strongly bound in uncharged states, when they are oxidized, the complexes dissociate. Dendrimers containing ferrocene units at the ends of the molecule have been prepared. The dendrimers form large supramolecular structures that can be broken apart or assembled upon... 

Another interesting comparison can be made with the charge transfer dynamics observed in porphyrin-ferrocene dyads. These supramolecular structures feature porphyrin and ferrocene units covalently linked. Imahori et al. have shown that the quenching of zinc tetraphenylporphyrin-ferrocene dyads takes place via the singlet state with a rate constant in the range of 10 s . This rate con-... 

Zakaria, C.M., G. Ferguson, A.J. Lough, and C. GlideweU. 2002. Ferrocene-1,1 -dicarboxylic acid as a building block in supramolecular chemistry Supramolecular structures in one, two and three dimensions. Acta Crystallogr. 58B 786-802. 

Fullerenes C60 and C70 form supramolecular adducts with a variety of molecules, such as crown ethers, ferrocene, calixarene, and hydroquinone. In the solid state, the intermolecular interactions may involve ionic interaction, hydrogen bonding, and van der Waals forces. Figure 14.2.9 shows a part of the structure of [K(18C6)]3-C6o-(C6H5CH3)3, in which Cgg is surrounded by a pair of [K+(18C6)] complexed cations. 

Similarly, the pyridyl fullerenes 30 and 31 also axially bind to ZnNcCBu)4 (28) to form supramolecular triads in which the zinc(II) naphthalocyanine acts as an electron donor, the pyridyl fullerenes act as primary electron acceptors, and either the ferrocene (Fc) or iV,iV-dimethylaminophenyl (DMA) moiety serves as a second electron donor [43], Fig. 2 shows the optimized structures of the resulting triads calculated by density functional theory (DFT), showing that the three components are arranged in a linear fashion. The binding constants of these systems (7.4 x 104M 1 for [ZnNc( Bu)4] 30 and 10.2 x 104M 1 for [ZnNc( Bu)4] 31 in o-dichlorobenzene) determined by UV-Vis spectroscopy are comparable with... 

Chlathrates may, in a way, be regarded as supramolecular adducts in the crystalline state. C ) forms a series of these compounds which in most cases are obtained by simple cocrystallization of their constituents. Known examples are the inclusion compounds with hydrocarbons tike pentane or nonane, etc., but chlathrates of Qo or C70 have also been found with hydroquinone in the presence of benzene. In these cases the fullerene molecules occupy interstitial spaces within the crystal structure of hydroquinone and form donor-acceptor complexes. Further inclusion compounds with fuUerenes are known for ferrocene and other inorganic substances such as sulfur (Sg), white phosphorus (P4) or complexes hke (PhCN)2PdCl2 and PhsPAuCl (also refer to Section 2.5.3). For the complex of > with ferrocene the crystal structure of the first is found with the latter inserted into the given gaps. The whole stracture can only exist because ferrocene is too weak a reducing agent to transform > into Qo. 

Ferrocene (Fc) possesses a rich synthetic chemistry, a three-dimensional structure which allows the preparation of many derivatives, high thermal stability, and good solubility in common organic solvents. These characteristics allow the synthesis of a great variety of liquid-crystalline materials. Furthermore, its unique electrochemical properties (fast and reversible one-electron transfer process) make Fc a valuable building block for the elaboration of redox-active supramolecular switches. In 30 years (1976-2006), liquid-crystalline ferrocenes have been established as a versatile class of metallomesogens. The aim of this chapter is to highlight the main results obtained for... 

Introduction of the tricarbonylchromium group into cyclophane chemistry has great potential for the preparation of planar- (or helical-)chiral compounds. Besides structure/chiroptics relationships, carrying out stereoselective reactions is of major importance. Recently, inclusion of ferrocenes and benzene-Cr(CO)3 into the cavity of a cyclodextrine was achieved and this makes the connection to supramolecular chemistry [183]. 

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