Metal cation chemosensors

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... 

Many chemosensors designed by Shinkai and coworkers are based on modification of the lower rim of a calix[4]arene with a fluorophore, whose emission properties change upon association of alkali metal cations. Fluorescence from the biphenyl subunit of 42 increases markedly upon the association of Na+... 

Chang JH, Jeong Y, Shin Y-K. Selective photoinduced electron transfer-based cyanoan-thryl fluorescent chemosensors for paramagnetic metal cations. Bull Korean Chem Soc 2003 24 119-22. 

In this section, the sensing properties of the cryptand and bibrachial lariat-type crowned spirobenzopyrans were presented. In the spirobenzopyrans, coloration was efficiently induced in the presence of the alkaline earth metal cations. The cryptand and bibrachial lariat-type crowned spirobenzopyrans represent highly sensitive and selective chemosensors for alkaline earth metal cations. 

Fluorescent chemosensors for the detection of heavy metal ions by a simple fluorescence tum-on (off-on) or quenching (on-ofi) are a fundamental tool for a rapid and nondestructive analysis of biochemical and environmental matrices (2007CSR993). A hot topic is the des p of selective sensors for Hg, one of the most hazardous pollutants of the environment. In this context, a new tren-based starburst molecule containing fluorinated 1,2,4-oxadiazoles as fluorophores has been synthesized and its sensing behavior towards several metal cations has been investigated by UV/Vis, fluorescence. 

SENSING OF D-METAL CATIONS USING ORGANIC LUMINESCENT CHEMOSENSORS... 

Finally, a number of 1,4-diaryltriazoles were reported to have tum-on fluorescence upon addition of a number of metal cations, although their selectivity was insufficient to render them useful chemosensors [48]. Guo and co-workers have also investigated the potential of these compounds for pH sensing [49]. 

It is believed that two crowns bind a K+ ion, thus leading to loosely preassembled bis-pyrene subunits. When the metal ion recognition event occurs in the presence of y-CD, dramatic enhancements of excimer emission are observed, thus providing a method to selectively detect K+ ion in aqueous solution. This ability to sense an ionic analyte is unusual for CD chemosensors. Modification of 28 with other ion binding sites should provide a general method for cation detection. 

Cyclenes are a useful component of metal sensor molecules. The common structure of such chemosensor is fluorophore - linker - sensor. Various fluorophores were connected to the cyclene which ensured the detection of the desired cation. These molecules were often water soluble and worked under physiological conditions what made them interesting from the biomedical point of view. 

The great impact in metal-ion coordination chemistry caused by the discovery of the macrocyclic polyethers31 has led to new designs of chemosensors for the alkali cations. Application of a supramolecular receptor to fluorescence sensing was first... 

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