Spectroscopic and computational studies on the development of simple colorimetric and fluorescent sensors for bioactive anions

Spectroscopic techniques (UVvis and fluorescence) and computational (HF/6-31G(d,p)) methods were adopted to investigate the anion recognition ability of two novel Schiff base receptors (L 1 and L 2 ) synthesised from the condensation of 5-nitrosalicylaldehyde and 2-aminophenol or 2-aminothiophenol. Both the receptors portrayed a visually detectable colour change upon addition of fluoride, acetate and dihydrogen phosphate anions from light yellow (L 1 ) or colourless (L 2 ) to yellow due to the formation of hydrogen bonding complexes in 1:1 stoichiometry and/or deprotonation between these anions and the receptors. No significant colour change was observed upon addition of other anions such as chloride, bromide, iodide and hydrogen sulphate.