Design And Synthesis Of Rhodamine B-based Fluorescent Probes For Selective Detection Of Al³⁺ And Fe³⁺

In recent years, fluorescence molecular probes have attracted particular attention of the researchers for their high sensitivity, controllable operation, excellent visual resolution and real-time discrimination detection. Rhodamine B and its derivatives have excellent Photophysics and Photochemistry properties. Therefore, the studies on fluorescent probes based on Rhodamine dyes are becoming hot subjects in the field of cations detection. As we all know, metal ions such as Al3+ and Fe3+ play the fundamental roles in many chemical and biological processes. It is very essential to design and synthesize specific fluorescence molecular probes for detecting these cations.-In this dissertation, starting from Rhodamine B, compound RB-1 was synthesized by introduction of 3-Aminopropanol into Rhodamine B. After purification, RB-1 was characterized by NMR in detail. The sensoring properties of RB-1 for metal ions were studied by Fluorescence and UV absorption spectroscopy. The results showed that RB-1 has low selectivity and exhibited response to both Al3+ and Fe3+. In order to obtain specific fluorescent probes which have remarkably high selectivity to Al3+ or Fe3+, we synthesized compound RM by introduction of 2-Mercaptopropionic acid to RB-1. After purification, RM was characterized by NMR and Mass spectrum in detail. The probe RM exhibited excellent selectivities toward Al3+ with a detection limit of 0.787μM. Moreover, the probe RB-1 could be employed stably to Al3+ in a facile solution of methanol-HEPES mixtures around pH=7.10. The relative association constant was Ka=1.56 ×104M-1.Based on the exploratory experiments for the synthesis of compound F, another specific fluorescent probe RBAC-1 which has high selectivity to Fe3+ was successfully synthesized by introducing 3-Aminobenzoic acid to RB-1. The sensoring properties of RBAC-1 for metal ions were studied by Fluorescence and UV absorption spectroscopy. The results showed that RBAC-1 exhibited specific and high response to Fe3+. The detection limit was 0.021 μM and the relative association constant was Ka=2.30×104M-1. Energy simulation tests were employed to demonstrate the coordination mechamism between probes and Fe3+. Moreover, the probe RBAC-1 was proved to be biocompatible according to cell experiments. Based on these advantages, the probe RBAC-1 has promising applications in the future.