Primary Study Of Designing Chemodosimeters Based On Cyanine And Coumarin Chromophores

Optical molecular chemosensors (OMCS) have emerged in the field of analytical chemistry as an application of molecular recognition. Research on OMCS has become one of the current scientific fronts due to its unique importance in probing the composition, structure and evolution of environmental or biological microsystems. Cyanine dyes and coumarins, known by their excellent spectroscopic properties, have found applications in the biological research. In this dissertation, some new OMCS using cyanine dyes and coumarins have been successfully developed based on a variety of irreversible and specific reactions. This dissertation consists of five chapters summarized as follows:In chapter 1, a general introduction to the concept and development of optical molecular chemosensors was presented. Then, Emphasis was paid on the developments of optical molecular chemosensors based on cyanine and coumarin chromophores. Finally, the objective of this dissertation was proposed.In chapter 2, the spectral character of a novel boronate of stilbazolium dye as optical molecular chemosensor for hydrogen peroxide was studied. The chemoselective H₂O₂-mediated transformation of arylboronates to phenols would serve as the foundation of this novel chemodosimeter for H₂O₂ in aqueous solution. The absorbance of the system in the longwavelength region, under optimum conditions, was proportional to the concentration of H₂O₂ with a good linear relationship according to our observation. Based on these facts, a spectrophotometry method was developed for the determination of H₂O₂. Besides its high sensitivity and specificity, the semi-quantitative determination by "naked-eye detection" is possible by this method.In chapter 3, the spectral character of an amino-substituted heptamethine cyanine as chromogenic chemodosimeter for Hg²⁺ was studied. Based on the Hg²⁺-promoted guanylation of thiourea and the intramolecular charge transfer (ICT) of this amino-substituted tricarbocyanine, a new method for the determination of Hg²⁺ was presented. Upon addition of Hg²⁺, the absorbance spectra shows a red shift of 166 nm, and accordingly, this spectral change resulted in the color change from blue to slight green, indicating that the chemodosimeter can also serve as a highly sensitive "naked-eye" indicator for Hg²⁺. In addition to the high sensitivity and specificity, this NIR chemodosimeter could greatly overcome the background interferences from bio-molecules or matrix.In chapter 4, a coumarin-based fluorescent sensor for sulfhydryl-containing amino acids was investigated based on the thiol-sensitive characteristic of 2, 4-dinitro-benzenesulfonyl group. First, the fluorescence response of the probe, 7-coumarinyl 2, 4-dinitro-benzenesulfonate, toward sulfhydryl-containing amino acids were investigated. Then the effects of pH, reaction time and coexisting substances on the reaction of the probe were also studied. Under optimum conditions, a fluorescent method for the determination of sulfhydryl-containing amino acids was developed.In chapter 5, some unsuccessful examples were summarized to avoid the same mistake in the further research in this field.