The Study Of Identification Chemical Small Molecules Based On Nucleophilic Addition

Small chemical molecules are ubiquitous in our daily life and they play important roles in people’s lifes and biochemical processes. They have been concerned by scientists worldwide because of their potential applications in medicine, catalysis, environmental science, life sciences and some other areas. A wide variety of excellent chemical sensors have been developed after the detection and recognition of small chemical became the research topics of many scientists. A class of chemical molecules have been concerned and studied due to their strong nucleophilicity. Thiol, hydrogen sulfide, cyanide and bisulfite which have strong nucleophile play vital roles in our life. Biothiol play many crucial roles in maintaining cell oxidation-reduction equilibrium, metabolism and some other physiological processs. A deficiency of cysteinc may cause causes various health problems such as retarded growth, hair depigmentation, lethargy, liver damage, muscle and fat loss, and skin lesions. An elevated level of homocysteine in human plasma is one of the symptoms of Alzheimer’s disease, cardiovascular disease, neural tube defect, inflammatory bowel disease, and osteoporosis. Glutathione plays a pivotal role in maintaining the reducing environment in cells and acts as a redox regulator. Hydrogen sulfide contributes to a diverse array of physiological processes, including vasodilation, angiogenesis, oxygen sensing, apoptosis, inflammation, and neuromodulation, and it can also protect against ischemia reperfusion injury. Cyanide is widely used in pesticides, metallurgy, electroplating and other industries. However, cyanide anion (CN-) is extremely toxic to organisms and is lethal to humans at 0.5-3.5 mg/kg of body weight. Sulfites are essential preservatives for many foods, beverages, and pharmaceutical products to prevent oxidation and bacterial growth and to control enzymatic reactions during production and storage. The sulfite and sulfur dioxide levels in food and medicine are therefore strictly limited in a number of countries. For example, in China, the levels of bisulfite in wine and beer may not exceed 0.05g/kg (calculated as SO2).New analytical methods for the determination of sulfite levels are important for consumer safety. Therefore, it is very necessary to study the nucleophilic molecules. With the advantage of their nucleophilic character, a variety of sensors have been developed in this dissertation.Based on our previous work, coumarin-chromene was prepared and characterized. The probe displays sensing features via a nucleophilic attack of thiols to the α,β-unsaturated ketone in 2-3 which resulted in the formation of a fluorescent coumarin derivative. As an additional feature,2-3-thiol derivatives can be used for the chromo-fluorogenic detection in water of the metal cations Cu2+, Hg2+ and Cd2+ via a metal-promoted desulfurization reaction and recovery of 2-3.N-[4-Methylcoumarin-7-yl]maleimide was firstly to be developed as a probe which exhibits highly selective recognition of cysteine. The detection limit was found to be as low as 74 nmol/L. Its potential application in bioimaging was also illustrated.A colorimetric and fluorescent chemosensor bearing hybrid coumarin-hemicyanine functionality has been synthesized for H2S sensing. The detection of sulfide was performed via the nucleophilic attack toward the polarized C=N and an electron-poor C=C bond of the probe, which can provide a potentially powerful approach for probing H2S chemistry in biological system.The nucleophilic nature of cyanide is used to develop a simple, sensitive, and highly effective sensor.Among the tested anions, the fact that only CN- could turn on the fluorescence intensity indicated that the system was a highly selective sensor for CN-A simple coumarin (7-diethylaminocoumarin-3-aldehyde) was utilized for the selective detection of bisulfite anions in water. The probe has exhibited a selective and sensitive response to the bisulfite anion against other anions, including Cys, through the nucleophilic addition of the bisulfite to probe. The fluorescence of the probe changes upon the addition of bisulfite anions, such that millimolar concentrations of bisulfite are detectable. Moreover, the sensor can also be applied to detect the level of bisulfite in sugar samples.