Synthesis And Properties Characterization Of New Cation-Sensititive Fluorescent Probes Based On Rhodamin B And 8-Hydroxyquinoline Derivatives

The recognition of the transition metal ions in aqueous solution is an important mission for analytical chemistry because of its important roles in many fields such as chemistry, medicine ?clinical biochemistry?, biology. Fluorescent chemosensor can transfer molecular recognition groups into fluorescence signals, which make a bridge between the target object and the analyst as an observer. The advantages of the probes include high sensitivity of detection down to the single molecule, high selectivity, ect. So it is developing the excellent fluorescent chemosensors that has been got more and more attention now.8-hydroxyquionline is a sort of important chelating agent, which is widely used in fluorescent molecular probes. The main mechanism is that the process of its combination with metal ion can block itself excited state intramolecular proton transfer, which makes the increase of fluorescent intensity in the system. In the second chapter of this paper, the specific reaction mechanism that generate furan ring structure, was used in 8-hydroxyquionline group for purpose of the design and synthesis of new fluorescent probe H1 using the specific recognition of mercury ion. The study results showed that:H1 exhibited the specific recognition of Hg2- by fluorescence emission spectrum, and the rest of cations were no interference. The addition of 5 equiv. Hg2- led to the increase 70 times of fluorescent intensity in the neutral test solution, and reaction of the system ended within 4h. After the NMR titration, H1 turned into the new corresponding compound Hg-HI upon the addition of mercury.Rhodamine-based fluorescent organic carriers have been widely used for conjugation with cations. In the third chapter of this paper, the specific reaction mechanism that generate furan ring structure, was also used in Rhodamine group in order to the design and synthesis of a new couple of corresponding fluorescent probe H2 and H3. Moreover, according to the unique structure of the rhodamine derivatives, we designed and synthesized a new couple of corresponding fluorescent probe H4 and H5 as well. The study results showed that:the spirolactam ring of probe H2 did not open by Hg²⁺, and the corresponding furan ring structure also did not exist. But there was an unexpected find that the solution significantly enhanced fluorescence intensity at ?_em=581 nm by Fe³⁺, which indicate that the spirolactam ring of probe H2 was open. Upon addition of Fe³⁺, the color of solution transformed into red in one minute, and that indicate H2 exhibited high sensitivity for Fe³⁺ and could be used for naked-eye detection. The addition of AcO- led to the fading of the fluorescence and color. The Fe³⁺ recognition processes were proven to be a revisable process.However probe H2 exhibited high selectivity for Fe³⁺ and the rest of cations were no interference. We carried out spectral titration and Job's experimental to know that the banding mode was 2.9 x104 M-1, ligand of the detection process 1:1, and detection limits 6.04 x 10"8 mol/L. which is more sensitive than many probes have been reported; meanwhile the detection limits of H2-Fe³⁺ complex to AcO- was 7.51 X 10^-8 mol/L. The successful living Ana-1 cell fluorescence imaging experiments demonstrated that H2 exhibited low cytotoxicity and cell-membrane permeability, and had potential value of ion imaging in biosystem. Comparing with star probe H2, probes H3, H4 and H5 had poor capability of detecting cations. H4 could detect Fe³⁺ and Cr³⁺ together, and it is difficult to distinguish them as to the same detected capability. H5 and H3 hardly had any ability of recognition, so they had no practical value.