Sensors Supramolecular

The mechanism of recognition of most supramolecular entities (such as abiotic receptors) is the formation of several hydrogen bonds. Since heterocyclic tautomers possess both strong HBA and HBD properties (see Sections III,G, V,D,2, and VI,G), they are often used for this purpose. For instance, the hydrogen bond network formed by 5,5 -linked bis(2-pyridones) has been used by Dickert to obtain sensors (96BBG1312). 

Cyclophanes or 7r-spherands have played a central role in the development of supramolecular chemistry forming an important class of organic host molecules for the inclusion of metal ions or organic molecules via n-n interactions. Particular examples are provided by their applications in synthesis [80], in the development of molecular sensors [81], and the development of cavities adequate for molecular reactions with possible applications in catalysis [82]. The classical organic synthesis of cyclophanes can be quite complex [83], so that the preparation of structurally related molecules via coordination or organometallic chemistry might be an interesting alternative. 

These results have demonstrated that the biomimetic approach of copying the supramolecular principle of archaeal cell envelopes opens new possibilities for exploiting functional hpid membranes at meso- and macroscopic scales. Moreover, this technology has the potential to initiate a broad spectrum of developments in such areas as sensor technology, diagnostics, biotechnology, and electronic or optical devices. 

Recently, Astruc et al. [189] reported novel amido-ferrocene dendrimers (e.g., 91) which were shown to act as supramolecular redox sensors for the recognition of small inorganic ions (Fig. 41). It was further observed that as the den-drimer generation number increased the sensitivity to the guest molecules also increased as observed by cyclic voltammetry experiments. 

F.-C. Gong, X.-B. Zhang, C.-C. Guo, G.-L. Shen, and R.-Q. Yu, Amperometric metronidazole sensor based on the supramolecular recognition by metallopor-phyrin incorporated in carbon paste electrode, Sensors, 3 (2004) 91-100. 

Keywords Luminescence m Fluorescence m Phosphorescence a Sensors a Switches a Logic Gates a Supramolecular Systems a Truth Tables a Photoinduced Electron Transfer a Molecular-Level Devices... 

L. Fabbrizzi, A. Poggi, Sensors and switches from supramolecular chemistry , Chem. Soc Rev. 1995, 24, 197-202. 

Fig. 37 (a) QD-based sensing of cocaine by the formation of a cocaine-aptamer supramolecular structure that triggers FRET and (b) time-dependent luminescence spectra of the system in the presence of cocaine. The inset shows a calibration curve for variable concentrations of cocaine and a fixed so observation time of 15 min. (c) Schematic of the FRET-based TNT sensor and (d) increase of the QD luminescence upon addition of TNT in the competitive assay format. (Reprinted with permission from [220, 221], Copyright 2009 Royal Society of Chemistry and 2005 American Chemical Society)... 

In the [Zn(2)2]2+ species, a single Zn2+ ion is able to revive the luminescence of all the 32 naphthyl units present in the two dendritic structures. This result shows that dendrimers can be profitably used as supramolecular fluorescent sensors for metal ions, as shown in Fig. 2. In this case, the sensor fluorescence is switched on upon metal ion coordination, and low Zn2+ concentrations (ca. 1 pM) can be easily detected. 

Class 3 fluorophores linked, via a spacer or not, to a receptor. The design of such sensors, which are based on molecule or ion recognition by a receptor, requires special care in order to fulfil the criteria of affinity and selectivity. These aspects are relevant to the field of supramolecular chemistry. The changes in photophysical properties of the fluorophore upon interaction with the bound analyte are due to the perturbation by the latter of photoinduced processes such as electron transfer, charge transfer, energy transfer, excimer or exciplex formation or disappearance, etc. These aspects are relevant to the field of photophysics. In the case of ion recognition, the receptor is called an ionophore, and the whole molecular sensor is... 

Fabbrizzi L. and Poggi A. (1995) Sensors and Switches from Supramolecular Chemistry Chem. Soc. Rev. 24, 197-202. 

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