Synthesis And Ion Recognition Properties Of Thiourea-based Substituted Poly(Phenylene Ethynylene) And2-thiohydantoin Receptors

There has been considerable interest in ion recognition and sensing because of thefundamental roles of ions in many chemical and biological processes. Photochemical analysismethod displays some advantages including the simple equipments, convenient operation andlow cost and has attracted much attention in recent years. Thiourea is the one of the mostcommon recognition groups, and substituted poly (phenylene ethynylene)s possess excellentphotoelectric properties. In this thesis, thiourea-based substituted poly (phenylene ethynylene)was synthesized, acting as a receptor for anions and metal ions through the colorimetricresponses, absorption spectrum and fluorescence spectrum with the signal amplification of theconjugated main chain. In addition, the NH moiety of2-thiohydantoin was attempted as arecognition site for the first time,2-thiohydantoin derivatives were synthesized and theirrecognition abilities were studied.Substituted poly(phenylene ethynylene) poly(1) were synthesized, the structure wasconfirmed by IR, NMR spectroscopies and element analysis. The recognition ability foranions and metal ions of poly(1) was investigated through colorimetric response experiment,UV–vis absorption spectrum and fluorescence spectrum. The results show that the solutionof poly(1) exhibited drastic color change upon the addition of F, along with the fluorescencequenching, thus provided a colorimetric receptor for anions. With regard to metal ions, thefluorescence of the polymer was quenched upon the addition of Ag+, while other cationsresulted in slight changes to the fluorescence. The fluorescence of poly(1)-Ag+recovered withthe addition of ADP, which can be applied in the detection of ADP.The2-thiohydantoin derivatives including3-butyl-5-(3,5-diiodine-4-hydroxy benzyl)-2-thiohydantoin (2),3-butyl-5-(4-hydroxy phenyl)-2-thiohydantoin (3),3-(4-nitrophenyl)-5-(2’-methyl propyl)-2-thiohydantoin (4), and3-(4-cyano phenyl)-5-(2’-methylpropyl)-2-thiohydantoin (5) were synthesized and characterized. The colorimetric responseexperiment indicated that2,4and5exhibited good specificity for F, while3can bond withstrong basicity F and CH3CO2. Exposure to corresponding anions resulted in obvious colorchanges of the solution of receptors, which provided colorimetric discrimination of the anions.The stoichiometric ratios between receptors and anions were determined through the Job’s plots.1H NMR titration revealed that the binding site interacted with anions through hydrogenbonding and/or deprotonation. Furthermore,3and4can be used to develop test papers fordetection of aqueous fluoride ion in the solid state.