Electrochemical Recognition of Anions

The addition of stoichiometric amounts of tetrabutylammonium bromide to electrochemical solutions of (84) led to gradual cathodic shifts in the reversible reduction wave of the host. A maximum shift of 45 mV was observed after 4 equivalents had been added. No cathodic shifts were observed with (87), which implies that bromide anion complex-ation within the macrocyclic cavity of (84) is essential for electrochemical detection. 

The general poor solubility of these macrocyclic polycobalticinium systems coupled with their lability to ester hydrolysis has very recently led us to a new synthetic strategy which utilizes the stable amide linkage to construct novel acyclic cobalticinium anion receptors (132). 

The electrochemical properties of compounds (90)—(97) were investigated in acetonitrile using cyclic voltammetry with [Bu 4N]BF4 as the supporting electrolyte. Each compound exhibited a reversible redox 

Only in the case where the cobalticinium receptor contains at least one amide N-H linkage are significant one-wave cathodic shifts pro- 

6 Three-electron reduction process as determined by coulometric experiments. f Cathodic shift in reduction potential produced by the presence of anions (4 equivalents) added as their ammonium or tetrabutylammonium salts. d Values obtained in DMSO solution. 

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Electrochemical recognition of anionic guest species by redox-active... 

Application of Ferrocenyl-Containing Dendrimers in the Electrochemical Recognition of Anions and as Electron Transfer Mediators in Amperometric Biosensors... 

Cuadrado. I. del Barrio, J.L. A polymerizable pyn ole-cobaltocenium receptor for the electrochemical recognition of anions in solution and immobilized onto 125. electrode surfaces. Inorg. Chem. Commun. 2002.5. 288-... 

The molecular recognition of anionic guest species by positively chaiged or neutral receptors is a relatively new area of research of growing interest in view of the key roles that these anions play in biochemical and chemical processes. For this reason, as part of the electrochemical studies, we decided to examine the use of the redox-active ferrocenyl dendrimers 3 and 4 that contain multiple N-H linkages capable of participating in H-bonding, as well as characteristic internal cavities,... 

Beer, P. D. Gale, P. A. Chen. G. Z. Mechanisms of electrochemical recognition of cations, anions and neutral guest species by redox-active receptor molecules, Coord. Chem. Rev. 1999, 185-186, 3-36. 

Supramolecules containing metal-polypyridine units, especially the Ru(dpp)-based dendrimers, could be used as electron reservoirs or components of molecular-electronic devices. Supramolecules in which an electroactive M(N,N) group is attached to a receptor capable of molecular recognition (crown ethers, calixarenes, cryptands etc.) can work as electrochemical sensors. Electrochemical recognition of cations as well as anions has been reported [33-35, 257, 263]. 

Recently, Shinkai and co-workers (85) reported a ferroceneboronic acid receptor (26). This receptor showed selective electrochemical recognition of fluoride ions over other halides, the redox potential for the ferrocene unit being perturbed on the addition of F . There is, however, only one orbital overlap interaction provided by this host and it is likely the selectivity arises solely due to the hardness of the fluoride anion. 

Beer. P.D. Drew, M.G.B. Smith. D.K. Selective electrochemical recognition of bidentate anionic guests in competitive solvents using novel ferrocenyl thiourea and guanidinium receptors. J. Organomet. Chem. 1997. 

Beer. P.D. Chen. G.Z. Goulden. A.J. Graydon, A.R. Stokes. S.E. Wear, T. Selective electrochemical recognition of the dihydrogen phosphate anion in the presence of hydrogen sulfate and chloride ions by new neutral ferrocene anion receptors. Chem. Commun. 1993, 24. 1834. 

The supramolecular assembly of dendrimers via H-bonding has been accomplished by Astruc, Boisselier, and Ornelas in which commercial dendritic poly(propylenimine) cores are rapidly and reversibly H-bonded to triallyl-or tris-amidoferrocenyl phenol dendrons these novel supramolecular assemblies were used for the electrochemical recognition of H2P04 and adenosine-triphosphate anions. ... 

With the aim of developing electroactive systems capable of electrochemically and specifically recognizing anions [370], some anionic receptors have been bound to redox-active groups such as cobaltocenium, ferrocene, and transition-metal bipyridyl moieties [370-373]. Although such compounds were suitable for the electrochemical recognition of some anionic species in solution, their immobilization on an electrode surface to achieve sensitive layers has been investigated with very few examples. 

Shao, Y. H., B. Linton, A. D. Hamilton, and S. G. Weber, Electrochemical studies on moleeular recognition of anions complex formation between xylylenyl bis-iminoimidazolinium and dicarboxylates in nitrobenzene and water, J Electroanal Chem, Vol. 441, (1998) p. 33. 

CV and SWV were used to investigate the electrochemical anion recognition properties of these species in acetonitrile and the results are summarized in Tables 21 and 22. With reference to the known electrochemical properties of [Ru(bipy)3][PF6]2, the respective reversible oxidation and reduction redox couples exhibited by the receptors can be assigned to the metal-centred... 

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