Amide-nitrophenyl based colorimetric receptors for selective sensing of fluoride ions

New chromogenic receptors containing 2-nitroplienyl or 3,5-dinitrophenyl groups appended to the amide or ill secondary airline positions have been synthesized and characterized. Upon addition of fluoride to two of the receptors ill acetonitrile, the solution acquired a yellow colour. The third receptor showed an intense purple colour with fluoride in acetonitrile and the appearance of the purple colour can be detected by the naked eye at parts per million level. The addition of chloride, bromide and iodide to the receptors did not induce any colour. Thus the receptors can act as fluoride ion sensors even in the presence of other halide ions. (c) 2005 Elsevier Ltd. All rights reserved.