The ICT Fluorophore For Molecular Recognition

Molecular recognition based on fluorescence detection has many merits, it hasattracted much attention and has been applied to many fields, such as life sciences,environmental sciences and communication sciences. In this thesis, ICT fluorescencechemosensors containing N-amino(thio)ureas were synthesized, their spectraproperties and application in molecular recognition have been investigated in thefollowing five chapters.In chapter 1, the development of molecular recognition and main fluorescencemechanisms of recognition were reviewed.In chapter 2, the interaction between N-amino(thio)ureas and serum albumin wasinvestigated by absorbance spectroscopy and fluorescence spectroscopy. FRETstudies indicated the energy transfer from proteins to the ICT fluorophore, whichmade the ICT fluorescence of fluorophore increase and proteins' fluorescencedecrease. Synchronous fluorescence spectroscopy revealed that the secondarystructure of HSA or BSA molecules was also changed in the presence of the ICTfluorophore.In chapter 3, a selective and sensitive fluorescent chemodosimeter for thedetermination of Hg²⁺ in aqueous solution was proposed based on N-[p-(dimethylamino) benzamido]-N'-phenylthiourea. The fluorogenic chemodosimetricbehaviors toward various metal ions were studied using fluorescence spectroscopy.High sensitivity as well as selectivity was achieved for Hg²⁺. This response camefrom a strongly fluorescent 1,3,4-oxadiazoles which was produced by the Hg²⁺promoted desulfurization reaction. The spectra of ESI mass and IR providedevidences for this reaction. It was promising for determining trace Hg²⁺ inenvironmental or biological samples.In chapter 4, a simple structural receptor containing ICT fluorophore showedhighly selective response to Zn²⁺ in pH 8.0 Tris-HCl buffer solution. The spectrum ofICT fluorophore showed two emission peaks in the presence of Zn²⁺ and thefluorescence intensity ratio could serve as monitor index for the determination of Zn²⁺ concentration. The long wavelength emission was ascribed to charge transfer of L toM. Mass spectra and IR spectra also gave evidences for 1:1 zinc(â…¡) complexformation. Moreover, this method successfully avoided the fluctuation in theexcitation source that suffered in total intensity sensing mode and the backgroundinterference. Thus it was good for application in detecting Zn²⁺ in biological samples.In chapter 5, absorbance spectroscopy and fluorescence spectroscopy were usedto investigate the interaction between serum albumins and zinc(â…¡) complex. Thefluorescence quenching of proteins in the presence of the complex was attributed tothe energy transfer-which also made the fluorescence of complex increase. It wasclear that the curves had a good linear relationship according to the quenchingequation, by calculateing there is two binding site between the compound and theprotein. Moreover, synchronous fluorescence spectroscopy revealed that thesecondary structure of HSA or BSA molecules was also changed in the presence ofthe ICT fluorescence.