Cyclodextrin ferrocene-functionalized

An interesting example of a system whose components become mechanically bound upon surface immobilization is rotaxane trans-21 (Fig. 13.24), consisting of a ferrocene-functionalized /3-cyclodextrin (fi-CD) macrocycle threaded on a molecule containing a photoisomerizable azobenzene unity and a long alkyl chain.33 A monolayer of trans-21 was self-assembled on a gold electrode. Therefore, the ring... 

As illustrated in Figure 5.23, Willner et al. [49] have developed a light-driven molecular shuttle. This device consists of a ferrocene-functionalized /3-cyclodextrin... 

The electrochemical properties of ferrocene-functionalized dendrimers have been studied also in the presence of )8-cyclodextrin f -CD), which is a well-known inclu-... 

A monolayer of the photoactive rotaxane trans-31 (Figure 19), which consists of a ferrocene-functionalized -cyclodextrin (/i-CD) macrocycle threaded on a molecnle containing a photoisomerizable azobenzene nnity and a long... 

Zuo F, Luo C, Ding X, Zheng Z, Cheng X, Peng Y (2008) Redox-responsive inclusion complexation between p-cyclodextrin and ferrocene-functionalized poly(N-isopropyla-crylamide) and its effect on the solution properties of this polymer. Supramol Chem 20 559-564... 

The condensation reactions described above are unique in yet another sense. The conversion of an amine, a basic residue, to a neutral imide occurs with the simultaneous creation of a carboxylic acid nearby. In one synthetic event, an amine acts as the template and is converted into a structure that is the complement of an amine in size, shape and functionality. In this manner the triacid 15 shows high selectivity toward the parent triamine in binding experiments. Complementarity in binding is self-evident. Cyclodextrins for example, provide a hydrophobic inner surface complementary to structures such as benzenes, adamantanes and ferrocenes having appropriate shapes and sizes 12) (cf. 1). Complementary functionality has been harder to arrange in macrocycles the lone pairs of the oxygens of crown ethers and the 7t-surfaces of the cyclo-phanes are relatively inert13). Catalytically useful functionality such as carboxylic acids and their derivatives are available for the first time within these new molecular clefts. 

Fe2(III,III)2+ states. By considering that organometallic dendrimers based on conjugated ferrocene units are of special importance since mixed-valence states have interesting electrical, redox, and magnetic properties, recently three generations of polypropylene amine) dendrimers, decorated at their periphery with 4, 8, and 16 (compound 6, Fig. 6.6a) BFc units, respectively, have been synthesized and the electrochemical behavior of the dendrimers complexed with (3-cyclodextrins ([3-CD) and adsorbed at self-assembled monolayers (SAMs) of heptathioether-functionalized [3-CD on gold (molecular printboard) has been studied.40... 

Norbomene was functionalized with cyclodextrins and surface grafted onto silica-based supports using ROMP (44). The CSP are suitable for the enantioselective separation various amino acids, including jS-blockers and other compounds, such as chiral ferrocene derivates. 

The supramolecular assembly of (3-cyclodextrin-capped AuNPs on ITO previously coated with a monolayer of ferrocene molecules was shown to exhibit interesting redox properties, as presented in Figure 8.5.25 This is a fine example of the functionalization of a nanoparticle with a functionalized recognition element to create a unique supramolecular scaffold with tailor-made properties. Specifically, the electrocatalytic determination of ascorbic acid was demonstrated by this surface assembly with excellent discrimination over dopamine. 

Figure 8.5 Schematic illustration of a supramolecular assembly consisting of a ferrocene (FC) monolayer-modified ITO electrode functionalized with ff-cyclodextrin (p-CD)-cappcd AuNPs.25 (Reprinted with permission from F. Zuo et al., Electroanalysis 2008,20, 894-899. Copyright Wiley-VCH Verlag GmbH Co. KGaA.)...

Different cyclodextrin monolayers have been synthesized and their surface properties have been characterized. Kaifer et al. prepared per-6-thiol-cyclodextrins, and described the interfacial monovalent ferrocene complexation at the monolayer.55 Mittler-Neher et al. studied the kinetics of the adsorption of mono- and multithiolate-functionalized CD SAMs.56,57 Beulen et al.,58 Huskens et al.,59 Auletta et al.,60 and Nijhuis et al.61 reported on the concept of molecular printboards, that is, (3-cyclodextrin ((3-CD) SAMs on gold or silicon oxide substrates, onto which complementary multivalent guest-functionalized dendrimer molecules were adsorbed, resulting in the formation of kinetically stable supramolecular assemblies. With the... 

Considering the high efficiency of enzymes, model compounds have been developed that mimic their functions (Fig. 4-21). Among them, -cyclodextrin occupies a prominent place, as it forms inclusion complexes with suitably constructed ferrocene derivatives that then may undergo kinetic resolution (Fig. 4-21 d). An ester of an unsaturated acid derived from a 1,2-ferrocenophane is the best substrate for this technique the rate of hydrolysis of one enantiomer is enhanced by 3.2 x 10 [133]. 

Curve (a) in Fig. 6.10 shows the CD spectrum in aqueous solution of a molecule comprising a ferrocene unit (achiral) functionalized with chiral D-glucopiranose units [21]. Curves (b-d) represent the spectral changes observed upon addition of / -cyclodexttin, a well known chiral macrocycle. In water, ferrocene forms an inclusion complex with -cyclodextrin. As in the examined spectral region only the... 

Fig. 6.10 CD spectral changes of a glucopyranose derivative of ferrocene (1 X 10- M, H2O, 295 K) in the absence (a) and in the presence of increasing amounts of / -cyclodextrin (b-d) [21], Notice that neither the D-glucopyranose units nor jS-cyclodextrin exhibit absorption bands in the examined spectral region. From the titration curve obtained by plotting the ellipticity at 350 nm as a function of the added equivalents of / -cyclodextrin (inset) the stabihty constant of the complex can be determined...

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