Ferrocene crown ethers

OXIDIZABLE CATION SENSORS Ferrocene crown ether species... 

The electrochemical properties of ferrocene have been utilized by many workers in the field of electrochemical molecular recognition. Saji (1986) showed that the previously synthesized (Biernat and Wilczewski, 1980) ferrocene crown ether molecule (Fig. 3 [1]), whose binding properties had previously been studied only by nmr and UV/Vis techniques (Akabori et al., 1983), could be used as an electrochemical sensor for alkali metal cations involving a combination of through-space and through-bond interactions. 

Initially, on addition of sodium cations to a solution of the ligand, two distinct CV waves were observed, corresponding to the uncomplexed and complexed compound [1] (Fig. 4) (Chariot et al., 1962). Hie wave at the higher positive potential corresponds to the solution complexed species. Hie oxidized ferrocene crown ether has a lower binding constant with sodium than the... 

Reaction of [l,r-ferrocenediyl6/s(methylene)]bi s[pyridinium] salt with diaza-12-crown-4 afforded the ferrocene crown ether l,l r,r -6(. s(ferrocenediyl)b/s[4,10-Ws(methylene)-1,7-dioxa-4,10-diazacyclododecane [95IC3964],... 

Although a selection of ferrocene crown ethers (Scheme 4) were initially reported by Biernat and Wilczewski (44), Saji (45) described the first evidence of anodic shifts in the oxidation potential of pentaoxa[13]-ferrocenophane (6) resulting from the addition of alkali metal salts. Two distinct electrochemical CV waves corresponding to complexed and uncomplexed (6) were observed for both Na+ and Li+ guest cations (Fig. 4). The respective anodic shifts correspond to a decrease of the... 

Electrochemical Data and Metal Cation Dependence of Ferrocene Crown Ethers Containing Direct and Schiff Base Linkages... 

Besides the ferrocene crown ether ligands described earlier, a variety of related macrocyclic ferrocenophanes containing various sulfur, oxygen, and nitrogen heteroatoms have been reported by a number of groups (110-115) (Scheme 21). These ligands complex transition metal guest cations such as Ag(I), Cu(I), and Pd(II) (116,117). Of particular... 

Plenio, H. Diodone, R. Complexation of Na in redox-active ferrocene crown-ethers, a structural investigation, and an unexpected case of Li" selecti ity. Inorg. Chem. 1995. 34. 3964-3972. 

As a matter of fact, the N-substitution induced in the polymer backbone a much weaker configurational flexibility than the 3-substitution. To circumvent this problem, Moutet et al. have synthesized polypyrroles N-substituted by ferrocene crown ether [270] and aza crown ether-linked bipyridine ruthenium (II) complexes [271]. Poly(19) was found to be Ba + and Ca " "-responsive [270], whereas the ruthenium(II)-based PPy was more sensitive to alkali metal cations [271]. The recognition of the cation binding was based on the changes in the electrochemical response of the metallic center instead of PPy. 

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