Synthesis,performance Analysis And Application Of Heterocyclic Rhodamine Fluorescent Probes

Traditional rhodamine dyes have excellent photophysical properties,such as large molar extinction coefficient,high fluorescence quantum efficiency,good light stability,strong Photobleaching ability,etc,but the emission wavelength of traditional rhodamine dyes is in the visible light zone,and the Stokes shift is small,which is not suitable for research on cell imaging.In view of the shortcomings of traditional rhodamine dyes as fluorophores at present,this paper starts with the construction of new xanthene dyes,and explores the probes used to identify and detect reactive oxides and metal ions.The main work is as follows:（1）The electron donor group of 3-methoxythiophene was introduced into the rhodamine skeleton,and the fluorescent dye DTPO with deep red light emission was designed and synthesized.Compared with the traditional rhodamine dyes,the introduction of heterocyclic thiophene makes the dyes have fluorescence emission at650 nm and high fluorescence quantum efficiency due to its asymmetric structure（Φ=0.57）and effectively extended the stokes shift,reaching 50 nm.At the same time,the classical spironolactone structure of rhodamine is retained,and the fluorescence signal is turned on through the spironolactone"on-off"structure,which provides a platform for the design of fluorescence probes.On this basis,o-phenylenediamine,which is sensitive to NO,was introduced as the recognition site,and a fluorescent probe DTPO-OPD was designed and synthesized.The probe exhibited high selectivity,sensitivity（detection limit of 42 n M）,fast response time（<3 minutes）,and fluorescence imaging detection of exogenous and endogenous mitochondrial NO in a water/acetonitrile=3/1（v:v）system.（2）On the basis of previous work in the laboratory,quinoline and its derivatives were introduced into the rhodamine skeleton,and fluorescent dyes HQO,DHQO and QRN were designed and synthesized.Due to the structural asymmetry,compared with the traditional rhodamine B dye,the Stokes shift and fluorescence emission wavelength of the dye are effectively improved.The stokes shift of the dye in ethanol reaches 50nm.The large stokes shift effectively reduces the interference of background signals and improves the resolution of cell imaging.Because all three dye structures contain nitrogen atoms and hydroxyl groups,they are conducive to coordination with metal ions.Among them,dye QRN can serve as a fluorescent probe for recognizing Fe³⁺ratio due to the participation of nitrogen atoms of oxoanthrene epoxy and benzoquinoline.In water systems,when dye QRN interacts with Fe³⁺,as the Fe³⁺concentration increases,the fluorescence intensity at 599 nm of the dye gradually decreases,while the fluorescence intensity at 454 nm gradually increases,Reaching saturation at 100equivalents.The dye QRN exhibits high selectivity and sensitivity to Fe³⁺（detection limit of 26.5 n M）,real-time monitoring of Fe³⁺,and can achieve fluorescence imaging detection of exogenous Fe³⁺.