A Ratio Fluorescent Sensor Based on Coumarin and Rhodamine for Sequential Detection of Aluminium Ion and Pyrophosphate and Its Applicability in Arabidopsis Thaliana

Abstract A ratio fluorescent sensor N '‐(( E )‐3‐(( E )‐((3′, 6′‐bis(diethylamino)‐3‐oxospiro[isoindoline‐1, 9′‐xanthen]‐2‐yl)imino)methyl)‐2‐hydroxy‐5‐methylbenzylidene)‐7‐(diethylamino)‐2‐oxo‐2 H ‐chromene‐3‐carbohydrazide ( I) based on the FRET mechanism was synthesized using coumarin as the donor and rhodamine as the receptor. Its structure was characterized by FT‐IR, 1 H NMR, 13 C NMR, and ESI‐MS. The sensing performance of sensor I was studied using fluorescence spectrophotometry, and the detection mechanism was studied using density functional theory. The results indicated that in MeOH/H 2 O medium, sensor I exhibits a significant fluorescence enhanced response to Al 3+ , with a detection limit of 5.8 × 10 −7 mol/L. In addition, complex I ‐Al 3+ exhibits a significant fluorescence quenching response to PPi, with a detection limit of 3.7 × 10 −7 mol/L, indicating that sensor I has high sensitivity and anti‐interference ability for the recognition and detection of Al 3+ and PPi. Through the analysis of complexation curves, it was found that the complexation ratio of sensor I to Al 3+ was 1:1 and complex I ‐Al 3+ to PPi was 2:1, and the cyclic response test could be performed stably for more than four times. The imaging results of Arabidopsis thaliana show that sensor I has low toxicity and good biocompatibility, which provides a way for the detection of Al 3+ in plants.