Anionic optical devices based on 4-(nitrostyryl)phenols for the selective detection of fluoride in acetonitrile and cyanide in water

Abstract Four compounds, 4-(4-nitrostyryl)phenol ( 1a ), 4-(2,4-dinitrostyryl)phenol ( 2a ), [4-(4-nitrostyryl)phenoxy]triisopropylsilane ( 3 ), and [4-(2,4-dinitrostyryl)phenoxy]triisopropylsilane ( 4 ), were synthesized and characterized. The three-dimensional molecular structures of compounds 3 and 4 were solved using X-ray crystallography. Compounds 1a and 2a were used in an acid-base strategy for the detection of fluoride and cyanide in acetonitrile. With the addition of small amounts of water the systems were able to detect only cyanide. Compounds 1a and 2a were also able to selectively detect cyanide in pure water, in the presence of a micellar concentration of cetyltrimethylammonium bromide, which is required to adjust the acidity constants of the compounds for the detection of the anion. Compounds 3 and 4 were used in a chemodosimeter approach for the selective detection of fluoride in acetonitrile. The fluoride attacks the silicon centers of 3 and 4 and through a nucleophilic substitution at the silicon (S N 2@Si) their corresponding colored phenolate species are immediately released as leaving groups. This process is effective in acetonitrile for the detection of fluoride, which is a strongly nucleophilic analyte under these experimental conditions. Paper test strips were prepared, containing compounds 1a and 2a , and in tests with aqueous solutions of different anions it was verified that only CN − changes the color of the modified paper.