Study On The Synthesis And Property Of Molecular Probe Based On The Fluorescein Derivatives

We selected fluorescein as the reporting group due to its superior brightness (Φ= 0.65, highε) and water solubility. In the present work, based on fluorescein chromophore, molecular probes were designed and synthesized. All compounds were characterized by MS, ¹H NMR. By measurement of their UV-vis and fluorescence spectra, the selection to metal ions and the titration of pH were investigated.Based on the fluorescein fluorophore, four pH probes were designed and synthesized, the FS4 probe exhibits good properties as a pH fluorescent sensor with a 99-fold fluorescence enhancement in the pH range of 4-8.Based on PET mechanism, we designed and synthesized two new fluorescein amide sensors FA. After addition of 6.5 equiv. Hg²⁺, FA2 showed obvious enhancement of fluorescence intensity at 522 nm. The mechanism for the fluorescence response was presumably the photo-induced electron transfer (PET) mechanism. The job plot indicated a 1:1 stoichiometry between FA2 and Hg²⁺.A fluorescein-based probe 2-pyridylaldehyde fluorescein hydrazone (FH1) for naked-eye sensing of Cu²⁺ was synthesized. A new absorption peaked at 496 nmε=1.2×10⁴L/(mol-cm) was observed upon the addition of copper ion. The solution changed from colorless to bright yellow.It showed obvious enhancement of absorbance at 496 nm comparing with other ions. The selectivity of FH1 to copper ion was very high.The aldehyde was reacted with resorcinol in CH₃SO₃H to afford the fluorescein derivative LF. Their photophysical properties and responses to cations were investigated.