The Synthesis And Properties Of New Near-Infared Dyes Based On Rhodamine Derivatives

Nowadays,fluorescent probe has aroused general interest in analytical chemistry.Due to high analysis speed,simple operation,good selectivity,high sensitivity,fluorescence analysis technology has been widely used in various fields,such as chemistry,materials chemistry,environmental science and biomedical fields.Rhodamine derivatives are excellent fluorescent probe dyes on account of a large rigid conjugate structure and high fluorescent quantum yield.However,rhodamine has a short wavelength which limits its application in biological imaging.Near-infrared（NIR）fluorescent probes,which absorption and emission wavelength are located in the range of 650-900 nm,possesse several merits,such as better tissue penetration,less damage to living cells,and less damage to biomolecules in the living systems.Therefore,in recent years,a growing number of people have studied near-infrared fluorescent probes.In this paper,by modifying rhodamine compounds to increase the conjugate structure of probes,we synthesized a series of near-infrared fluorescent probes,which can be applied in the detectionof GSH and Al³⁺ respectively.Details are as follows:Firstly,we designed and synthesized two near-infrared fluorescent probes named NIR-Rh1,NIR-Rh2.And structures of probes were confirmed and characterized by mass spectrometry,1H NMR and 13 C NMR spectroscopy.Secondly,an NIR fluorescent probe（NIR-Rh1）with high fluorescence quantum yield was developed.And NIR-Rh1 with spirolactam structure was firstly synthesized and used to recognize GSH.NIR-Rh1 exhibits high fluorescence quantum yield（Φ =0.43）after the addition of GSH and high sensitivity toward GSH with 75-fold fluorescence enhancement.Furthermore,the probe is highly selective,which will not interfere with the other biological thiols（Cys,Hcy）and amino acids.Furthermore,the response mechanism of NIR-Rh1 with GSH is supported by NMR and MS.In particular,NIR-Rh1 displays selective detection of GSH in biological samples such as living cells and tissues.Finally,another NIR fluorescent probe（NIR-Rh2）is developed for detecting trivalent aluminum ions(Al³⁺).To the best of our knowledge,this is the first exampleof near-infrared fluorescent probes that is applied in the detection of aluminum ions in biological samples.It exhibits high sensitivity to Al³⁺ with a 77-fold fluorescence enhancement after the addition of 2 equiv.of Al³⁺ added.The probe can be highly selective in the detection range of 1.0 × 10^-7 to 2.0 × 10^-5 M of Al³⁺,and the detection limit is about 3.0 × 10^-8 M.And the probe provides excellent selectivity toward Al³⁺over other metal ions.When p H is 6.0-8.0,it won’t interfere with the detection of Al³⁺.The response of the probe is less than 90 s and the probe is chemically reversible.Furthermore,the ring-opening mechanism of the NIR-Rh2 spirolactam induced by Al³⁺ were supported by NMR,MS and DFT theoretical calculations.In addition,the proposed probe has been used to detect Al³⁺in living cells and tissues with satisfying results.