A new chromogenic azo-azomethine sensor, containing active phenolic sites, has been designed and synthesized via condensation reaction of N,N,N′,N′-tetrakis(2-aminoethyl)-2,2-dimethyl propane-1,3-diamine with 1-(3-formyl-4-hydroxyphenylazo)-4-nitrobenzene. The anion recognition ability of the synthesized receptor was evaluated using UV–Vis spectroscopy and 1H NMR technique. The anion recognition studies exhibited that the receptor acts as a sensor for biologically important anions such as F−, AcO− and H2PO4− over other anions. The binding stoichiometry between sensor and anions was found to be 1:2. 1H NMR experiment revealed that sensor recognizes anions via H-bonds and subsequent deprotonation to elicit a vivid color change. Interestingly, the sensory system not only let for the naked eye detection without any spectroscopic instrumentation but also helped to discriminate between anions.
