Fluorescent Sensor For I~-Based On Coumarin In Aqueous Solution

Iodide plays an important role in several biological activities and chemistry synthesis.Detecting the level of iodine ions is of great interest to many scientists, including chemists,biologists, clinical biochemists and environmentalists. The advantages of fluorescent sensorsinclude convenience, high sensitivity and selectivity, observation in situ, etc. The coumarindyes have excellent photophysics and photochemistry properties such as high stability againstlight, high fluorescence quantum yields and big Stokes shift, etc. Therefore, fluorescentsensors for anions based on coumarin have drawn much attention in recent years.The fluorescent sensors S1-3for I~-based on coumarin have been designed andsynthesized. Their recognition effects for anions have been investigated in HEPES neutralbuffer. S1exhibits I~--only sensitive among anion（sF~-, Cl~-, Br~-, I~-, AcO-, HSO4-, H2PO4-, CN-）.The addition of I~-leads to80nm blue-shift in absorbance maximum, a6nm blue-shift influorescence maximum, a5.9-fold fluorescence enhancement and an obvious fluorescencechange from almost yellowish green to brilliant blue. Other anions has no interference for S1to detect I~-. S2exhibits I~--only sensitive among anions. The addition of I~-leads to21nmblue-shift in absorbance maximum, a13nm blue-shift in fluorescence maximum, a2.5-foldfluorescence enhancement and an obvious brilliant fluorescence. Other anions has nointerference for S2to detect I~-. S3exhibits I~--only sensitive among anions. The addition of I~-leads to12nm blue-shift in absorbance maximum, a4nm blue-shift in fluorescence maximum,a83%fluorescence quenching and an obvious fluorescence change from almost brilliantgreen to dark green. Other anions has no interference for S3to detect I~-. S1-3having similarstructure exhibits different reconition effects for I~-, the proposed mechanism is that p-OMe(electron-donating group) and p-NO2(electron-withdrawing group) on the aniline ring in S2-3vary the electron cloud density around the molecular and ICT, which have interference on therecognition effects.