Synthesis and Spectroscopic Study of a Chemosensor for Naked Eye Recognition of Cu2+ and He2+

Compound L, as the procedural sensor for the detection of Cu2+ and Hg2+, was designed and synthesized based on the coumarin-modified rhodamine derivative. The structure of compound L was characterized by NMR, high resolution mass spectrometry and infrared method. Its sensing behavior toward various metal ions was investigated with absorbance methods. The study found that L had good selectivity and sensitivity for Cu2+. When addition of various metal ions (Zn2+, Hg2+, Cu2+, Fe3+, Cd2+, Co2+, Ni2+, Mg2+, Ca2+, AP(3+), La3+, K+, Na+, Mn2+, Pb2+ and Ag+), only Cu2+ could induce a visible change of solution from colourless to pink and a new absorption band centered at 534 nm appear, which indicated that compound L could be used for the naked eye detection of Cu2+. From UV titration, the detection limit was about 1. 9 X 10(-8) mol . L-1. Test strips based on L were fabricated, and this test strips could act as a convenient and efficient Cu' test kit. The binding ratio of the complex of L-Cu2+ was 1 : 1 according to the Job' s plot and high resolution mass spectrometer (FIRMS) experiments. Moreover, Upon addition of 1 equiv. EDTA to the mixture of L and Cu" in DMSO solution, colour changed from pink to almost colourless, indicating that the EDTA replaced the receptor L to coordinate with Cu2+. Therefore, L could be classified as a reversible sensor for Cu2+. In addition, when adding Hg2+ to L-Cu2+ complexes, a visible change of solution from pink to colourless was observed, while other metal ions didn't cause this change. Thus, L-Cu2+ complex also could be used for the naked eye recognition of Hg2+, and the detection limit was calculated about 2. 9 X 10(-7) mol . L-1 according to the UV titration. Consequently, this procedural sensor L could be use for the orderly naked eye recognition of Cu2+ and He2+.