Synthesis and anion recognition studies of novel 5,5-dioxidophenothiazine-1,9-diamides

Novel 5,5-dioxidophenothiazine-1,9-diacetamide and -dibenzamide receptor molecules were prepared starting from commercially available and relatively cheap chemicals. The anion recognition properties of these two diamides were investigated using UV–vis spectroscopy. Chloride formed a simple hydrogen-bonded complex with the diacetamide receptor, while fluoride, acetate and dihydrogen phosphate deprotonated both sensor molecules. Upon titration with fluoride deprotonation occurred via the formation of [HF2]−, and in the case of the diacetamide receptor complexation took place alongside deprotonation.