The Synthesis Of Rhodamine, Tricarbocyanine Derivatives And Their Application In Fluorescent Probe For Cation Detection

Fluorescent probes can transfer molecular recognition events into fluorescence signals, which make a bridge between the molecular analytes and the analyst. It has been of current interest in molecular recognition owing to its high sensitivity, nice selectivity, observation in situ (fluorescence imaging), and so on. Rhodamine derivatives are an important class of material in fluorescent probe because they have good photophysical properties and solubilities in water. Most importantly,the distinct color and fuorescent changes due to the spirolactam ring-opening makes these derivatives more valuable for sensing ions through ?uorescence. At the same time, the NIR fluorescent probe based on tricarbocyanine derivatives with small background interference has also attract wide attention, owing to several advantages: it is poorly absorbed by biomolecules, so it can penetrate deeply into tissues; there is also less auto-fluorescence in this region, and so the characteristics of the Near-infrared dyes are favorable for in vivo imaging.In response to these research focus, a series of rhodamine and tricarbocyanine derivatives were designed and synthesized in this paper, and their application in fluorescent probe were studied.1. A rhodamine-coumarin conjugate D was designed ,synthesized. Synthetic route is as follows: Compound A is synthesized from 7-diethylaminocoumarin by DMF/ POCl₃. Rhodamine B reacts with hydrazine to get rhodamine B hydrazide B, and then rhodamine B thiohydrazide C is obtained from Compound B by Lawesson's reagent. The condensation of A and C generates Compound D. The relevant reaction mechanisms were discussed. The target product and the intermediate were confirmed by MS, 1H NMR and 13C NMR. Compound D was prepared as a fluorescent probe for Hg²⁺. The probe is based on a specific metal ion induced reversible ring-opening mechanism of rhodamine Derivatives, which leads to significant changes in color and fluorescence. The analytical performance characteristics of the proposed Hg²⁺-sensitive probe were investigated. The Probe exhibits high sensitivity and selectivity for sensing Hg²⁺, and increase in fluorescence emission intensity is observed upon binding Hg²⁺ in 50% water/ethanol buffered at pH 7.24. The fluorescence response to Hg²⁺ is attributed to the 1:1 complex formation between the probe and Hg²⁺, which has been utilized as the basis for the selective detection of Hg²⁺. 2. Starting from rhodamine B and 2-thienylethylamine, a rhodamine-thiophene conjugate E was designed , synthesized. The target product was confirmed by MS, 1H NMR and 13C NMR. Compound E was prepared as a fluorescent probe for Hg²⁺ based on the same mechanism as chapter 2. The analytical performance characteristics of the proposed Hg²⁺-sensitive probe were investigated. The probe exhibits high sensitivity and selectivity for sensing Hg²⁺, and increase in fluorescence emission intensity is observed upon binding Hg²⁺ in 50% CH3CN/H2O buffered at pH 6.00. The fluorescence response to Hg²⁺ is attributed to the 2:1 complex formation between the probe and Hg²⁺, which has been utilized as the basis for the selective detection of Hg²⁺.3. A new Near-infrared dye derivative, 2-(2-aminoethyl)-pyridine-tricarbocyanine F was synthesized from IR-780 and 2-(2-aminoethyl)-pyridine. The target product was confirmed by MS, 1H NMR. Compound F was prepared as a fluorescent probe for Cu²⁺. The analytical performance characteristics of the proposed Cu²⁺-sensitive probe were investigated. The probe can be applied to the quantification of Cu2+ with a linear concentration range. The experiment results show that the response of F to Cu2+ is pH independent in 50% CH₃CN/H₂O buffered at pH 6.0-8.0, and exhibits excellent selectivity towards Cu²⁺ over other common metal cations.