A colorimetric chemosensor for the sequential recognition of Mercury (II) and iodide in aqueous media

A new highly selective colorimetric chemosensor 1 N′1,N′2-bis((1E,2E)-3-(4-(dimethylamino)phenyl)allylidene)oxalohydrazide was designed and synthesized as a colorimetric sensor for Hg^{2 +}. The sensor 1 showed high selectivity toward Hg^{2 +} in a 1:1 stoichiometric system and fast color change from yellow to orange in the presence of Hg^{2 +}. The sensing mechanism was explained by theoretical calculations. Moreover, the resulting 1-Hg^{2 +} complex acted as an efficient colorimetric sensor for I^-, showing recovery of 1 from 1-Hg^{2 +} complex. Furthermore, 1 and 1-Hg^{2 +} complex could be used as practical, visible colorimetric test kits for Hg^{2 +} and I^-, respectively, in an aqueous environment. Therefore, probe 1 could be a good alternative method for onsite and real time screening of Hg^{2 +} and I^-.