Synthesis And Properties Of Novel Fluorescence Ratiometric Probes Based On Rhodamine B-naphthalene Conjugates

Nowadays, Fluorescent probes have been widely used in various fields.Rhodamine-based fluorescent dyes have been widely used in the preparation ofcationic fluorescent probes due to their advantages of good fluorescence quantumyield, high molar extinction coefficient, low cost and good water solubility.Rhodamine B derivatives are very weak and colorless with a spiro ring form, whilethe cyclic structures are opened, they lead to a strong fluorescence emission in thevisible region with the solution turned pink color. Naphthalimide derivatives are idealfluorescent carries. These compounds have desirable spectroscopic properties, suchas strong thermal stability and light stability, high fluorescence quantum yield,moderate emission wavelength and strong fluorescence.In this thesis, we designed and synthesized a series of rhodamine B–naphthaleneconjugate derivatives, which were novel ratiometric fluorescent probes based oninduced fluorescence resonance energy transfer (FRET) and through bond energytransfer (TBET). Target compounds (L1-L10) were characterized and comfirmed by1H NMR,13C NMR, IR and HR-MS.Through a series of fluorescence emission and UV absorption spectras test, westudied the spectral properties of target compounds. Owing to the strong thiophiliceffect of Hg2+, we designed and synthesized compounds L1and L2which exhibitedhighly selective and sensitive ratiometric recognition toward Hg2+based on FRET inMeOH-water solution. But the recognition modes for Hg2+were different. Thecoordination of L1with Hg2+was chemically and partially reversible, but sensor L2was irreversible. The detection limit of sensor L2toward Hg2+was2.11×10-8M,which was lower than L1. Sensor L3suggested selective ratiometric detection of Fe3+through bond energy transfer (TBET) in a MeOH-water (4:6, v/v) solution and wasthe first reported fluorescent probe based rhodamine B–naphthalene conjugate. Thetime course of fluorescence intensity in the presence of L3and Fe3+indicated that thestable reading coule be obtained in less than1min. Sensor L5exhibited the ratiometric detection of Fe3+in a ethanol solution, which was based on fluorescenceresonance energy transfer (FRET). Comparison, the end structure with differentnitrogen-containing groups of the compounds had no much impact on selectiverecognition. Sensor L1、L2、L3and L5all could be applied for ratiometricfluorescence imaging in living cells, and preliminary experimental resultsdemonstrated that they had potential applications in biological systems.