Calix pyrrole sensors based

As far as chemical sensors are concerned, colorimetric chemosensors for anions based on calix[4]pyrrole (16-18, 22-31) showed strong binding to the fluoride anion. Receptors (29-31) are the first naked-eye detectable chemosensors that are able to discriminate between different anionic substrates as a result of detectable colour changes. On the other hand, the fluorescence of the receptors (16-18, 22-28) is quenched significantly in the presence of anionic guests. 

Chromogenic octamethyl calix[4]pyrrole-based sensors (e.g., 165-167) for antipyretic carboxylates such as naproxen, ibuprofen, and salicylate, without bias by bicarbonate or carboxy termini of blood plasma proteins, have been described <2005JA8270>. The formation of a sensor-anion complex results in partial charge transfer and a dramatic change in color. 

Many of the p-substituted calix[4]pyrroles known in the literature were likewise synthesized via a condensation strategy. Typically, a functionalized pyrrole bearing substituents on one or both of the p-pyrrolic positions is condensed with a ketone under acid catalyzed conditions. However, a number of mono-substituted calix[4] pyrroles have been prepared by a post-synthetic strategy. Here, a functional group, such as an ester, formyl, or iodine substituent, is introduced onto one of the P-pyrrolic positions within OMCP. In many cases, this is done by subjecting the calix[4]pyrrole to deprotonation with a strong base (e.g., n-butyl lithium), followed by the addition of the appropriate electrophile [9,10]. On the other hand, iodination has typically been achieved by reacting calix[4]pyrrole with iodine-[bis(trifluor-oacetoxy)iodo]benzene [11]. These functionalized systems have been elaborated further to create, inter alia, anion sensors or materials that may be attached to solid or polymeric supports. 

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