Studies On The Synthesis And Ion Recognition Properties Of Schiff Base Containing Thiourea And Carbazole

Along with the rapid development of the economy, hazardous contaminants have earned close attention due to their harmful effects on human health and the environment. In order to detect different kinds of ions, many kinds of chemical chemosensors have been reported. Mercury as one of hazardous contaminants has attracted extensive attention. Mercury can gradually accumulate in our brain tissue, and it will damage the brain when reaching a certain amount. The design and synthesis of fluorescent chemosensors do not have to complex instruments and procedures and high cost. It has a short reaction time, high sensitivity and selectivity.We use carbazole and 4-aminobenzoic thiourea as raw materials, a new schiff-base(L1) was synthesized. With the study of the fluorescence spectrometry、 UV-absorption spectrometry of L1, it found that L1 have a recognition effect on Hg2+. After adding the Hg2+, the fluorescence of LI get a enhancement. In addition Hg2+, the binding stoichiometry is confirmed as 1:2 ([Hg2+]:[L]) by both using UV-Vis, Job’s plot and fluorescence methods. The fluorescence enhancement of L-Hg2+ may be due to the intramolecular PET process is suppressed, and the isomerization C=N. Therefore, L1 can be used as a chemical sensor to detect Hg2+, with high selectivity, high sensitivity.L2 is adding a benzothiazole group based on L1. And compared with L1 and it occurred a red shift of UV-absorption peak. After adding the Hg2+, the fluorescence of L2 get fluorescence quenching. Using Job curve found that the complexing ratio of L2 and Hg2+ to be 2:1. the detection limit was 7.9×10-6 M. Fluorescence quenching of L2 is likely to be the addition of Hg2+, suppressesed the intramolecular ICT process.L3 and L4 are on the basis of L1 to import a thiophene group and a phenyl. It found that both L3 and L4 have a recognition effect on Hg2+. Besidesit L3 have a recognition effect on Ag+. we have experimented with reversible, find the solution of L-Ag+ is reversible, and the solution of L-Hg2+ is irreversible, the desulphurization may occur. Through Job curve indicating L3 with Hg2+, Ag+ complexation are 1:1.The detection limits of Hg2+ and Ag+ are 1.3×10-5 and 1.O×1O-5. The solution of L4 are changed from colorless to yellow, with the naked eye can identify, after adding Hg+ and get fluorescence quenching. The Job curve indicate that the L and Hg2+ is 2:1 complexing, the detection limit of 6.5 × 10"6 mol/L. The cause of L4 fluorescence quenching could be intramolecular ICT process. After joining KI found that L-Hg2+ is a reversible process.L5 have a benzothiazole group and a thiophene group, make its have a bigger conjugate system. After joining ion, can be found that L5 has the response to the various ions, this may be related to its functional groups is more, it contains both benzothiazole group, N, S and thiourea groups, which leads to, it can with many ions complexation, resulting in its ion of specificity of choice, also found that its stability is bad, may be associated with its structure is too long, therefore increase the conjugate system, though is likely to make molecular fluorescent occurred red shift, but also can make the molecular stability is reduced, the loss of specificity of ion selective.