The hydrogen sulfate recognition properties of azo-salicylaldehyde schiff base receptors

Azo-salicylaldehyde Schiff base-typed receptors containing an acidic H-bond donor moiety were synthesized and characterized. The UV-Vis data indicate that these receptors could act as selective colorimetric sensors for basic anions and acidic species hydrogen sulfate by different color changes in a water-containing medium. The experiment of Br?nsted acid-base reaction by adding the sodium hydroxide or perchloric acid revealed that the mechanism of recognition of anions might be deprotonation/protonation of the OH fragments by interacting with different anions and that the deprotonation/protonation process is fully reversible. The deprotonation/protonation of the receptors is responsible for the dramatic color change. Supported by the National Natural Science Foundation of China (Grant Nos. 20371040 & 20671077), the Natural Science Foundation of Gansu Province (Grant No. 3YS051-A25-01) and the Key Project of Chinese Ministry of Education (Grant No. 205161)