Synthesis And Application Of Fluorescent Probes Based On Rhodamine-Benzothiazole Sacffold

Too much or too little heavy metal ions will have a certain impact on our living environment and health.Iron ions play important roles in the human body,such as oxygen transfer,electron transfer,and enzyme reactions.Excessive iron ions can cause serious cell damage.Fe²⁺is the potential catalyst of Fenton reaction,which leads to serious cell damage through the generation of hydroxyl radicals.Mercury（Hg）is a liquid metal,which generally exists in two ionic states of mercury（I）and mercury（II）,Salt containing mercury（I）and mercury（II）dissolved in water has great biological toxicity.Hypochlorous acid（HClO）is a kind of reactive oxygen species（ROS）.Excessive accumulation can cause tissue damage and cause diseases that seriously affect human health.Small molecule fluorescent probe has many advantages such as small size,simple synthesis and wide application.Generally,the fluorescence signal of the analyte to be measured is changed by the chemical reaction between the analyte to be measured and the fluorescent probe.In this paper,three kinds of small molecular fluorescence probes were designed and synthesized based on rhodamine-benzothiazole sacffold for the detection of metal ions(Fe²⁺,Hg²⁺)and hypochlorous acid（HClO）,respectively,and their spectral properties were studied.Based on rhodamine-benzothiazole sacffold,using NO as recognition group and ESIPT mechanism,a ratio type fluorescence probe HOS for recognition of Fe²⁺was designed and synthesized.The ESIPT process exists between the hydroxyl group and the nitrogen atom on the benzene ring of the probe,which releases yellow-green fluorescence.After the addition of Fe²⁺,the nitrogen oxide is reduced,the spiral ring of rhodamine is opened,and the ESIPT process is broken,which releases orange-red strong fluorescence.The probe can specifically identify Fe²⁺,has a ratio response,excellent fluorescence properties,good linear relationship（0-10μm）,high sensitivity and low detection limit（3.1 n M）,etc.On the basis of rhodamine-benzothiazole sacffold,thiourea group was introduced to design and synthesize the"off-on"fluorescent probe AHT for recognition of Hg²⁺.The probe AHT showed weak fluorescence.After the reaction with Hg²⁺,the two molecules of the fluorescent probe formed coordination bonds with Hg²⁺through the intramolecular S atom and N atom.The five-member spiral ring of rhodamine opened and emitted strong fluorescence.The probe has good fluorescence properties,good linear relationship（0-46μm）,low detection limit（0.30μm）,good selectivity and competitiveness,and is suitable for the detection of Hg²⁺in biological environment.Finally,based on the rhodamine-benzothiazole sacffold,a fluorescent probe OST for HClO detection was synthesized.The probe itself can emit weak green fluorescence.After adding ClO^-,C-N and an ester bond on a benzene ring is disconnected,forming N=N and hydroxyl group,and rhodamine ring is opened,emitting red fluorescence.This probe has high fluorescence quantum yield,good linear relationship,sensitive reaction,good selectivity and strong anti-interference ability.which can be well applied to biological environment,and lays a foundation for the diagnosis and treatment of diseases.