Molecular sensors metal cations

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. 

One of the first alkali metal cation chemosensors was based on the molecular architecture of the anthracene derivative (Figure 16.2c) [9]. Substitution of the simple tertiary amino group with an azacrown macrocycle resulted in fluorescence of the chemosensor responding to protons and potassium cations (Figure 16.5a). Further increase in selectivity of the sensor can be achieved via reduction of Brpnsted s basicity of the macrocycle. On the other hand, this modification must retain the electron donor character of the receptor in order to preserve the PET mode of... 

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]. 

Compared to systems based on a single interaction, cooperative sensors based on multiple, concerted, inter-molecular interactions between the components exhibit higher discrimination capabilities and enhanced functions. As examples for this class of sensors, two systems, both based on the absorption/luminescence properties of the porphyrin nucleus are illustrated in Fig. 5. Structure (a) represents a ditopic receptor where cooperative binding of a cation by the amide-appended calixarene and of an anion by the Zn-porphyrin allows recognition of complete binary metal salts. Structure (b) incorporates two cyclodextrin cavities and relies on the modification of the Fe(III) complex spectroscopic properties by inclusion of guests in these hydrophobic sites.This species is able to sense the presence of benzylmercaptane and 1-adamantanecarboxylate in four... 

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