Synthesis And Spectra Study Of Reaction-Based Cyanide And Thiol Receptors

Among various anions, cyanide is one of the most concerned anions because of its being widely used in synthetic fibers, resins, herbicide, and the gold-extraction process. However, cyanide anion is extremely detrimental, and could be absorbed through lungs, gastrointestinal track and skin, leading to vomiting, convulsion, loss of consciousness, and eventual death. Thus, there is a need for an efficient sensing system to monitor cyanide concentration from contaminant sources. Due to the importance of cyanide in environment, the design and synthesis of efficient cyanide receptors attracts intensive interests of scientists and have become a significant subject in the field of supramolucular chemistry. However, the traditional cyanide synthetic receptors or sensors on the basis of hydrogen bonding interactions show poor selectivity due to the presence of F-, AcO-, CO32-, HCO3-, HSO4-, and H2PO4-which often display the strong interference to cyanide detection. In this dissertation, three novel fluorescent probes with coumarin and anthracene as fluorophores and1,3-indanedione and benzo[b]thiophene-3(2H)-one1,1-dioxide as receptors for cyanide were designed and synthesized.On the other hand, considering the similar strong nucleophility of the thiols and cyanide, we were thinking that the conjugate1,4-addition of thiols to unsaturated bond could be used for the detection of thiol with high selectivity. Biothiols such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) play crucial roles in many physiological processes. Alternations in the level of cellular thiols have been linked to a number of diseases, such as cardiovascular disease, Alzheimer’s disease, leucocyte loss, psoriasis, liver damage, cancer, and AIDS. Thus, it is important to develop efficient methods for the detection and quantification of biothiols in physiological media for academic research and clinic applications. Due to their simplicity, inexpensiveness, sensitivity and selectivity, optical approach based on synthetic colorimetric and fluorescent probes has attracted increasing interest during the last decade. In the last part of this dissertation, a novel fluorescent probe with coumarin as fluorophore and benzo[b]thiophene-3(2H)-one1,1-dioxide as receptor for thiol was designed and synthesized. The main contents and results are outlined as follows:In chapter1, the major sensing principles of optical chemosensors are introduced, and the progress of cyanide recognition and thiol detection is reviewed. Finally, the objective of this dissertation was proposed.In chapter2, a ratiometric fluorescent probe (2-1) based on coumarin-indandione conjugate was synthesized for cyanide detection. A colorimetricand ratiometric fluorescent probe (2-1) for the detection of cyanide ion based on the1,4-addition reaction of cyanide ion to indandione moiety in CH3CN, exhibits fast response and high selectivity toward cyanide ion over other anions. The Michael addition of cyanide to indandione of2-1would block the ICT from the electron-rich coumarin group to the electron-poor indandione group, leading to a blue shift in the absorption spectra and emission spectra with an observed color change (from pink to colorless). The1:1binding stoichiometry for the compound2-1with cyanide ion was confirmed by HRMS, and the proposed mechanism was confirmed by1HNMR. Additionally, compound2-2with a nitro group was designed and synthesized as a control compound for investigating the substituent effect.In chapter3, a ratiometric fluorescent probe (3-1) based on coumarin-benzo[b]thiophene-3(2H)-one1,1-dioxide conjugate was synthesized for cyanide detection. A colorimetric and ratiometric fluorescent probe (3-1) for the detection of cyanide ion based on the1,4-addition reaction of cyanide ion to benzo[b]thiophene-3(2H)-one1,1-dioxide moiety in CH3CN, exhibits fast response and high selectivity toward cyanide ion over other anions. The Michael addition of cyanide to benzo[b]thiophene-3(2H)-one1,1-dioxide of3-1would block the ICT from the electron-rich coumarin group to the electron-poor benzo[b]thiophene-3(2H)-one1,1-dioxide group, leading to a blue shift in the absorption spectra and emission spectra with an observed color change(from pink to colorless). The1:1binding stoichiometry for the compound3-1with cyanide ion was proven by HRMS, and the proposed mechanism was confirmed by1HNMR.In chapter4, a turn-on fluorescent probe (4-1) based on anthracene-indanedione conjugate was synthesized for cyanide detection. A colorimetric (from yellow to colorless) and turn-on fluorescent probe (4-1) for the detection of cyanide ion based on the 1,4-addition reaction of cyanide ion to indandione moiety in CH3CN, exhibits fast response and high selectivity toward cyanide ion over other anions. The Michael addition of cyanide to indandione of4-1would block the π-conjugation of the molecule and the whole molecular structure becomes flexible, which makes it easy for the two parts of the compound to fold. Consequently, light excitation may induce the interaction of1,3-indandione anion with anthracene, leading to exciplex formation. In addition, the fluorescence enhancement at short wavelength (467nm) is probably a result of the inhibition of PET quenching from the anthracene to the indandione-containing Michael receptor upon addition of cyanide. The1:1binding stoichiometry for the compound4-1with cyanide ion was proven by job’plot and by HRMS, and the proposed mechanism was confirmed by1HNMR.In chapter5, two colorimetric probes for the detection of thiol based on the1,4-addition reaction of thiol to indandione moiety in DMSO-PBS buffer, exhibit fast response and high selectivity toward thiol over other amino acids. The Michael addition of thiol to2-1or3-1would block the ICT from the electron-rich coumarin group to the electron-poor1,3-indandione or benzo[b]thiophene-3(2H)-one1,1-dioxide group, leading to a blue shift in the absorption spectra with an observed color change(from bluevoilet to colorless).