Synthesis And Fluorescence Properties Of Asymmetrically Condensed Thiosemicarbazones As The Small Molecule Probes

Thiosemicarbazone and semicarbazide compounds have special structures and properties,because thatthey contain sulfur atoms and electron-donating nitrogen,so that they have strong complexation ability,and can form complexes with many metal ions.Especially for the mercury ions,due to its hydrophilic characteristics,it is easy to coordinate or react with such compounds.In this paper,we use triphenylaldehydeand triazole-aldehydes as the fluorescent chromophores,diaminothiourea and diamino urea,nitrogen atoms as the identification moieties when design these probes.Their optical properties were detected by fluorescence spectroscopy and ultraviolet spectrophotometer.The main research contents are as follows:1.Using diaminothiourea and triphenylaldehyde as the parent material,a small amount of triphenylaldehyde was slowly addedto the ethanol solution of diaminothiourea.The probe M1 was successfully obtained by controlling the dropping speed and reaction temperature.When Hg2+ was added to the mixed solution of M1(VDMSO: VTris-HCl=8:2),the maximum absorption peak of M1 was red shifted,and its fluorescence was completely quenched.The detection limit of M1 to Hg2+was up to 3.11 × 10-8 M.Job's plot,nuclear titration,mass spectrometry were used to explore the possible mechanisms.2.L1 was synthesized by using triazole aldehydes and diaminothiourea in a similar manner.Then,using L1 and M1 as the reaction products,adding the same amount of salicylaldehyde,respectively.The bilateral asymmetric condensation products of M2 and M3 was obtained.After fluorescence and UV test,we found that M2 has a good selectivity to recognize CN-,and its detection limit was 7.6 × 10-8 M,while M3 has light-induced aggregation effect,but it can not specifically recognize cations and anions.3.Using 2-naphthaleneboronic acid and bromotriazole aldehydes as raw materials,L2 was prepared by Pd-catalyzed coupling reaction.Then,the probe M4 was prepared by condensation reactionbeteen L2 and thiosemicarbazide.M4 couldselectively detect Hg2+ and Ag+.The difference of response time between the two ions provides an effective method to distinguish them.4.Monosodium diurethylamine Schiff base M5 was successfully obtained by using diaminurea and triphenylaldehyde as raw materials.The synthesis method was similar to that of M1.After fluorescence and UV test,foundind that it has good recognition ability and anti-interference ability to Hg2+,the detection limit was up to3.68 × 10-8 M.