Study On The Synthesis And Properties Of Rhodamine Derivatives For The Detection Of Salicylic Acid

As one of endogenous phytohormone,salicylic acid?SA?is widely distributed in plants,and it plays an extremely important role in the growth and development stages of plants and in the regulation of systemic acquired resistance?SAR?mechanism.In recent years,the role of salicylic acid in the regulation of SAR mechanisms has attracted more and more attention.Thus,it is extremely urgent to develop a real-time method for the determination of endogenous SA in plants.Fluorescent probes have the advantages of good selectivity,high sensitivity,real-time detection,and the ability to detect endogenous small molecules.Therefore,it‘s an ideal method to detect SA.In our previously work,we used probe 1 to detect SA and found that it showed high selectivity for salicylic acid with naked-eye detection.There was nearly negligible interference for the detection of SA from all other competing species,and probe 1responded to varying degrees of salicylic acid derivatives.In the fluorometric and UV–vis titration experiments,the fluorescence intensity and absorbtion titration curve showed a steady and smooth increase until a plateau was reached.The association constant of the probe 1 towards SA was 5.77×10³ M^-1,and the detection limit was 2 nM.Then,we used¹H NMR to speculate a plausible mechanism and probe 1 was successfully applied to imaging SA in vivo,bioimaging investigations showed its good cell-membrane permeability,and probe 1 could detect exogenous SA.We modified the structure of probe 1,then designed and synthesized three small molecule fluorescent probes based-Rhodamine B.The structures of the compounds were identified by 1H NMR,13C NMR and ESI-MS.Through cell imaging and in vitro tests,we found that the modified probes not only achieved a certain improvement in fat solubility,but also maintained good selectivity,extreme sensitivity,naked-eye,strong interference immunity and low detection limit for SA.In the same way,we used ¹H NMR to speculate a plausible mechanism,and calculated the binding constant of each probe for SA.