| The recognition and sensing of the heavy metal ions has emerged as a significant goal in the field of chemical sensors in recent years. Among these ions, because of the widely used of silver ion, the essential in bolsystem of ferric ion and the most toxity of mercury ion, development of new methods for sensing these in biological and environmental samples is urgent.Due to their excellent spectroscopic properties of high fluorescence quantum yields, large molar extinction coefficient and long absorption and emission wavelength elongated to visible region, rhodamine B bsed fluorescent probes have received increasing attention. Rhodamine derivatives with spirolactam structure are colorless and non-fluorescent, whereas ring-opening of the spirolactam induced by the metal ions take place, they will exhibit a pink color and strong fluorescence emission. The spirolactam-ring opening system of rhodamine derivative would provide an excellent platform for the design and synthesis of fluorescence-enhanced sensor.This work focuses on the design and synthesis of rhodamine-based "OFF-ON" fluorescent probes and these applications research. Ours studies are carried out as follows:1. A bis-rhodamine based fluorescent probe R1 was designed and synthesized from the rhodamine B, ethylenediamine, and 2-3-(hydroxymethylene)-1-cyclohexene-l-carbaldehyde. It exhibited a high selectivity and sensitivity for the detection of Fe3+, and the detection limit was 3.7×10-7 M. Using Fe3+ and S2- as chemical inputs and the fluorescence intensity signal as outputs, R1 can be utilized as an INHIBIT logic gate at molecular level. A rhodamine ethylenediamine triazine aminopyridine derivative RC2P was synthesized from the rhodamine B, ethylenediamine, cyanuric chloride and aminopyridine. Being environmentally friendly, the probe RC2P colud detect Fe3+ in water solution. The binding constant of RC2P-Fe3+ was calculated to be 4.1×108 M-1. Both of R1 and RC2P were successfully applied to the imaging of Fe3+ in living cells.2. Five fluorescence probes for Ag+ were designed and synthesized from the rhodamine ethylenediamine triazine derivative, atechol, resorcinol and hydroquinone. This article widens the scope of rhodamine applications, because few of Ag+ probes based on rhodamine had been reported. The rhodamine ethylenediamine triazine hydroquinone derivative (RP1) exhibited a high selectivity and antijamming capability for the detection of Ag+, and the detection limit was 3.2×10-8 M. A simple nanofiltration membrane test strip for the rapid monitoring of Ag+ was developed based on RP1.3. Two Off-On fluorescence probes (RH and RC) for Hg2+ were synthesized from the rhodamine ethylenediamine triazine derivative,8-hydroxy quinoline and carbazole. The probe RH exhibited a high selectivity and sensitivity for the detection of Hg2+, and the detection limit was 2.2×10-8 M. The applicability of the probe RH to detect Hg2+ in two samples of tap water and lake water were successfully analyzed.4. The highestoccupied molecular orbital (HOMO)-lowest unoccupied molecularorbital (LUMO) energy of R1 and RC2P, and the optimized structures of R1, RC2P, RO1, RM1, RM2, RP1, RP2 and RH were performed using the Materials Studio software. The HOMO energy of R1-Fe3+ was -3.009 ev,and the LUMO energy of R1-Fe3+ was -2.552 ev. The HOMO energy of RC2P was -4.339 ev, and the LUMO energy of RC2P was -2.256 ev. The optimized geometries of R1, RC2P, RO1, RM1, RM2, RP1, RP2 and RH could help to research the relationship between the spatial configuration of probe and cations, which had a great significance. |
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