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1.4 CHEMICAL SCIENCES
A neutral 2-site chloride selective compound has been developed (3), based on a 1,3- alternate tetrasubstituted calixarene providing a preorganised supramolecular scaffold. The resultant supramolecular cavity is amongst the first to combine urea functional groups bridged with single methylene spacers to pyrene moieties. It combines a naturally and synthetically proven H-bonding system with the elegant ratiometric fluorescent signalling properties of an intramolecular pyrene excimer system, triggered by conformational changes upon anion coordination. The excimer emission of 3 is quenched, with a simultaneous rise in the monomer emission solely by the chloride anion amongst a wide variety of anions tested. 3 has an association constant of 2.4×104M-1 with chloride. The suitability and advantages of ratiometric optical sensor compounds like 3 for use in practical sensor devices is discussed. 3 has an LOD of 8×10-6M with chloride in acetonitrile-chloroform (95:5 v/v). A dynamic fluorescence study revealed a response time ofproduct.
Schazmann, B., Alhashimy, N. & Diamond, D. (2006) Journal of the American Chemical Society, 2006, Jul 5;128(26):8607-14. DOI: 10.1021/ja061917m