Design And Synthesis Of Cu²⁺ Receptors For Recognition

Heavy and transition metal ions play the important roles in many biological and environmental processes, in particular, Cu²⁺ is one of the necessary trace elements for the human body, which ranks third in the human body only inferior to Fe³⁺ and Zn²⁺ . To design and synthesize chemosensors for Cu²⁺ has drawn much recent interest. Due to high sensitivity, intrinsic simplicity and remote sensing capacity, fluorescent sensors have been rapidly developed. Fluorescent sensing heavy and transition metal ions based on fluorescence enhancement is a subject of intensive recent interest.This article consists of five chapters.Chapter 1 briefly summaries the background of the research. The research to be carried out is presented in the same chapter.Chapter 2 describes equipments, materials and methods involved in this dissertation. Synthetic details and characterization of sensor molecules are provided.Absorption and fluorescence spectral properties of the synthesized receptors and their response to metal ions are reported in Chapter 3. These receptors based on benzaldehyde thiosemicarbazone (PTMB).Chapter 4 reports Absorption spectral properties of the synthesized receptors and their response to Cu²⁺ ions. These receptors based on phenyl benzamide (DMB).Chapter 5 additional reports a ligand (DMPN) based on thiourea compound, which could detect Cu²⁺ conveniently.Series PTMB derivatives were detailly studied as sensors for metal ions. It was found that PTMB could bind metal ions such as Cu²⁺, Pb²⁺, Hg²⁺and Ni²⁺ in a similar coordination manner in the ground state in acetonitrile, but only Cu²⁺ induces dramatic enhancement in the fluorescence of PTMB while other heavy and transition metal ions have little effect on it. The highest fluorescence enhancement factor was observed in l-(2-Methoxybenzylidene)-4-phenylthiosemicarbazide (PTMB-OM) with a value of 35 in acetonitrile and was the biggest in PTMB series. PTMB-OM used as a fluorescent sensor for Cu²⁺ in acetonitrile and water mixtures was then examined. The fluorescence enhancement factor of PTMB-OM was up to 15 fold in the presence of Cu²⁺even if in acetonitrile/water (9:1, v/v) mixture. Under the same conditions, other metal ions led to minor changes in the fluorescence spectrum of PTMB-OM. It was therefore concluded that PTMB-OM could be employed as a potential fluorescent chemosensor for Cu²⁺with high selectivity and sensitivity.In the research of the production reacted by Cu²⁺ and PTMB-OM, We found that the high selectivity between Cu²⁺ and PTMB-OM comes from the strong oxidation ability of Cu²⁺ in acetonitrile. A ring compound (PTMB-cycle) with high Fluorescence quantum yields was made after the reaction between Cu²⁺ and PTMB-OM. We had reported the structure data of crystal, which could illustrate the mechanism of fluorescence enhancement of PTMB-OM in the presence of Cu²⁺.Furthermore, the series of phenyl benzamide (DMB) were synthesized. The effect of different metal cations on the ultraviolet absorption spectra in acetonitrile solution was studied. The experimental results showed that only Cu²⁺ induces dramatic enhancement in Absorption spectral of DMB derivatives while other heavy and transition metal ions have little effect on it.Additionally, a higher selectivity and sensitivity receptor DMPN based on thiourea compound was prepared. The effect of different metal cations on the ultraviolet absorption spectra showed highly Cu²⁺-selective absorbance intensity enhancing properties in acetonitrile solution. The selective and sensitive signaling behaviors was found to originate from the Cu²⁺ induced transformation of a colorless solution into a amaranth one, which could detected by nude eyes.