A highly selective colorimetric chemodosimeter for thiol-containing compounds in aqueous solutions is reported. The design protocol makes use of a highly specific reaction between thiols and the electrophilic four-membered ring of highly colored, fluorescent squaraine backbones. At neutral pH selective decoloration and total emission quenching was found due to the rupture of the highly delocalized squaraine framework upon selective nucleophilic addition of thiol-containing derivatives. The squaraine derivatives have been successfully applied to the determination of low-molecular mass aminothiols in human plasma. The method utters the high potential applicability of the chemodosimeter approach in the search for new or improved chromogenic selective or specific probes for target guests.

A new chromo-chemodosimeter for the anion sulfide in aqueous environments has been developed. The recognition concept is based on a pyrylium-thiopyrylium transformation that is conveniently drawn toward "color chemistry" concepts by means of the anchoring of an aniline group. This causes the color of the aniline-pyrylium backbone in L1 to change selectively from magenta to blue when transformed to the corresponding aniline-thiopyrylium in the presence of the sulfide anion. The method is simple and easy, suggesting potential applications in a variety of different environments where easy and rapid determination of sulfide might be required.

The Hg 2+ ion is one of the environmentally most important metal ions whose toxicity, even at very low concentrations, has long been recognized and is a problem of primary concern.[1]Moreover, despite a reduction of its industrial use as a result of stricter regulations, high concentrations of mercury are still present in many environmental compartments and it can still be found in many products of daily life such as paints, electronic equipment, and batteries.[2] Accordingly, the need for analytical methods for the sensitive and selective determination of mercury is of topical interest, especially in situations where conventional techniques are not appropriate, for instance in many on-site or in situ analyses and for rapid screening applications. In these fields, optical and electrochemical sensing devices play a leading role, in particular utilizing molecular probes that generate and transduce an analytical signal as a response to the binding event. [3] Although several examples of redox-active, [4] fluorogenic, [5] and chromogenic [6] chemosensors for Hg 2+ ions have been reported recently, the combined "binding site and signaling subunit" approach that is commonly used with such probes often harbors disadvantages for analysis in realistic media. Many signaling units suffer through the strong hydrogenbonding ability of water, fluoroionophores often undergo unspecific fluorescence quenching upon binding to heavymetal ions, and the number of Hg 2+ -ion-selective receptors is limited.A particularly attractive alternative presented herein are chemodosimeters that indicate an analyte through a specific chemical reaction between dosimeter molecule and target species, leading to the formation of a fluorescent or colored product. [7,8] A disadvantage of dosimeters, however, is that the reactions are mostly irreversible and thus provide only single-use assays.To take advantage of the favorable features of chemodosimeters and also reuse them, it is necessary to install a procedure that allows the molecular reporter to be regenerated. We thus designed a method where the indicator dye is passivated first in a chemical addition reaction with a small organic compound, the "spectroscopic inhibitor" that "switches off" the color and fluorescence of the indicator. This addition product is the chemodosimeter. The target ion then reacts with the inhibitor, liberating the dye, that is, signaling is accomplished by "metal-induced dye release" methods. With the proper choice of dye scaffold and passivation reaction, it should thus be possible to generate drastic chromo-and fluorogenic changes that result in a true "switching-on" behavior rather than a modulation of already existing signals or minor shifts of absorption or emission bands.We have applied this newly designed procedure to the selective analysis of Hg 2+ ions. The method is based on the thiophilic affinity of the Hg 2+ ion and its reactivity with 2,4-bis(4-dialkylaminophenyl)-3-hydroxy-4-alkylsulfanylcyclobut-2-enone (APC) derivatives. As we have recently shown, APC der...

An ionically controlled nanoscopic molecular gate has been developed by using functionalized mesoporous materials. The system shows that control of mass transport at nanometric scale can be achieved by using suitable rigid solids and pH-active molecules. The design principle suggests new perspectives in the search of ionically tuned tailored materials and devices with a fine control of mass transport for new applications in fields such as drug delivery, selective removal of toxic species, sensing, or catalysis.