Synthesis Of Schiff Base Fluorescent Probes And Recognition Study To The Spectroscopic Properties

With the use of various metal products and the aggravation of environmental pollution, the content of metal ions in vivo has increased. And that is likely to cause biological disorders and even various diseases, and bring serious damage to the health of the living body. Therefore, it is great demand to have a rapid and efficient method to detect the presence and content of metal ions. Fluorescent methods have gained much attention of researchers now due to its good selectivity and recognition, rapid response and application in the environment and organisms. The fluorescent probe based on a Schiff base structure has synthesized facilely and can improve the chelator's affinity toward metal ions. Therefore, Schiff base structure has become an ideal mode to construct fluorescent chemosensors. In this paper we have synthesized six Schiff-based fluorescent probes. Their structures were confirmed by HRMS, IR,1H NMR and 13C NMR, and their spectral properties were investigated, too. The contents mainly including the following parts:1. The structure, influence factors and mechanism of probes are reviewed. A summary of Schiff-based fluorescent probe literature in recent years are reported.2. Four new Schiff-based fluorescent probes ?R1, R2, R4 and R5? by using rhodamine B as fluorophore have been synthesized and the spectral properties including selectivity, competition, concentration titration curve, job curve, pH and time curve were investigated. The effect of substituents on the fluorescence intensity of the probe was also discussed. The UV absorption and fluorescence spectra show that they have the same response to Fe³⁺. Compared with probe R3, the fluorescence intensity of probe R1 was decreased, and the probe R2 was increased. Moreover, probe R4 and R5 showed excellent selectivity and recognition toward Fe³⁺regardless of whether there were other metal ions.3. Two new Schiff-based fluorescent probes ?R6 and R7? by using aminothiazole moiety as electron donor have been synthesized. We can see that the addition of Cd²⁺ makes R6 exhibite an intense fluorescent emission, which realizes high selectively of the recognition, Cd²⁺ and probe R6 complex can also form a new fluorescent probe RC to achieve relay recognition. Probe RC exhibits highly selective and sensitive to PO₄^3- by fluorescence quenching method and had no significant variation regardless of whether there were other anions. A good liner relationship between the fluorescence emission intensity of RC and the concentration of PO₄^3- in a certain range was noted, and PO₄^3- can be quantitatively detected in this range. The probe R7 has good selective recognition ability for Fe³⁺.