Application Of Urea And Thiourea Derivatives On Fluorescence Analysis

In the recent years,fluorescence analysis was an important and effective spectrum analysis. Therefore, designing and synthesizing different kinds of fluorescent receptors have become a hot topic and been studied by chemist according to the property of recognizing guest. The fluorescent receptor usually consists of two parts, a recognizing moiety and a signal reporter. When the guest binded with the recognizing moiety the fluorescence property of receptor would undergo change. The change of fluorescence spectrum can be used to detect and distinguish the guest. Urea and thiourea derivatives have always attracted the interest because of its important roles in drug synthesis and industrial application. Meanwhile, the applications of urea and thiourea derivatives in fluorescence analysis have gained great attention gradually. In this dissertation, we introduced the interaction between urea / thiourea derivatives and other molecules, and expounded the mode of action in the following five chapters.In chapter 1, the application of urea/thiourea derivatives in several aspects were briefly reviewed. Then emphatically introduced the development of urea/thiourea derivatives in serum albumins recognition, metal ions recognition and anion recognition.Because of the importance of urea and thiourea derivatives used in fluorescence analysis, we designed and synthesized three fluorescence compounds, 1-[p-(dimethylamino) benzoyl]-4-phenyl-semicarbazide (1), 1-[p-(dimethylamino) benzoyl]-4-phenyl- thiosemicarbazide (2) and p-(dimethylamino) benzamido-thiosemicarbazide (3) based on intermolecular charge transfer (ICT), and studied their application in serum albumins, metal ions and benzaldehyde recognition.Chapter 2 described the method of synthesis, the characterization by IR and ¹H NMR of the fluorescent molecular 1, 2 and 3 and their spectral data.In chapter 3, the interaction between l-[p-(dimethylamino) benzoyl]-4-phenyl-semicarbazide (1) and serum albumin in Tris-HCl buffer of pH 7.4 was investigated by absorption and fluorescence spectroscopy. l-[p-(dimethylamino) benzoyl]-4-phenyl-thiosemicarbazide (2) was also studied as a control compound. FRET studies indicated the energy transfer from the proteins to the host, which resulted in the increasing of 1's fluorescent intensity and the decrease of protein fluorescent intensity. Synchronous fluorescence spectroscopy revealed the secondary structure of human serum albumin (HSA) not bovine serum albumin (BSA) was changed in the presence of 1. 2 and serum albumin had no interactions, and this suggested that the strong interaction between 1 and serum albumin attributed to 1 contains two amide bonds which were similar to peptide bond. The study showed urea derivatives could be storaged and transported by serum albumin in vivo easily compared with thiourea derivatives. Thus, comparing with 2,1 is the better choice in designing these kinds of drugs.In chapter 4, a selective and sensitive fluorescence probe for the recognition of Cu²⁺ in CH3CN was proposed based on l-[p-(dimethylamino)benzoyl]-4-phenyl-semicarbazide (1), l-[p-(dimethylamino)benzoyl]-4-phenyl-thiosemicarbazide (2) as a control compound. In CH3CN solution, the maximum emission wavelength of 1 peaked at 368 nm and 491 nm. Upon addition of increasing amount of Cu²⁺, the fluorescence intensity at 368nm and 491 nm quenched and the quenching rate being up to 75%, a good linear relationship between fluorescence intensities and Cu²⁺ was obtioned. Hg²⁺ also could quench the fluorescence of 1, but the quenching rate only was 25%. The additional of other metal ions, such as Pb²⁺,Mg²⁺,Fe²⁺,Co²⁺,Zn²⁺,Cd²⁺, ect, didn't led to obvious change of the fluorescence spectra. All these results indicated that 1 was highly selective for Cu²⁺. 2 also emits dual fluorescence in CH₃CN, which peaked at 371 nm and 497 nm respectively. Concomitanting with the addition of Cu²⁺ to the solution of 2, the characteristic strong fluorescence emission band of 2 at 371 nm was greatly increased firstly and then decreased; meanwhile, a new band centred at 426 nm was increased. The additional of other mental ions only produced some changes of the spectra of 2 which distinguished from the spectra of Cu²⁺ in the presence, and had no new emission. Fluorescence titration, MS and IR showed a 1:1 stoichiometry between 1 or 2 and Cu²⁺, and it was estimated the different fluorescence phenomena after addition of Cu²⁺ attributed to the difference of the molecule structure between C=O(1) and C=S(2).In chapter 5, p-(dimethylamino) benzamido-thiosemicarbazide (3) was proposed for the determination of benzaldehyde via fluorescence spectroscopy. A strong fluorescence compound schiff's base formed based on the reaction between host 3 and benzaldehyde. In pH 5.30 NaAc-HAc aqueous-acetonitrile mixture solution containing 20% acetonitrile, a good linear fluorescence responses as a function of benzaldehyde concentration was obtained ranging from 1.25×10^-7 to 3.23×10^-6moI L^-1. The limit of detection was found to be 3.75×10^-8 mol L^-1. The existence of large amount of formaldehyde, acetaldehyde, acetone and hypnone didn't interfere the determination of benzaldehyde indicating high selectivity. The proposed method was applied to determine benaldehyde in discharge water samples and the recovery was 99.5-97%.