| There are a variety of biochemical reactions in human life, and many metal ions and biological molecules take part in the reaction. Due to their special physiological functions, they play an important role in the activities of life. Some of them are necessary for the body, and the concentration maintains in a certain range in the physiological environment. However, when the concentration is abnormal, they will affect human's health. The others are non-essential or even harmful to life. The accumulation in body will cause various diseases. To determine the concentration of these ions and bioactive small molecules accurately and efficiently is essential for the treatment and prevention of the diseases which get from the abnormal concentration. With high sensitivity, fast and convenient detection and the short response time, fluorescent chemical sensors have been widely in application. In recent years, a lot of fluorescent chemical sensors were synthesized, but the sensors based on the phenanthroline groups are rare. Phenanthroline derivatives as fine biological ligands have been widely used as the secondary structure of DNA probes. It has been proved that they have low toxicity and good membrane permeability. Due to the fine luminescent properties, phenanthroline derivatives may have potential applications in the fluorescent chemical sensors. In this paper, we designed and synthesized several fluorescent probes based on phenanthroline groups to detect biological molecules, selenite combined-4-([1,10] phenanthroline [5,6-d] imidazol-2-yl) toluene (Cl), Cl-Zn2+ system and 4-([1,10] phenanthroline [5,6-d] imidazol-2-yl) benzaldehyde(PIPIP), which could specifically recognize Zn2+, Cu2+, and D-3--hydroxybutyric acid respectively. The main contents are listed as follows:1. A fluorescent chemical sensor Cl was synthesized, which can specifically recognize Zn2+ in the aqueous solution. The compound showed little observable fluorescence in aqueous solution. Notably, the fluorescent intensity at 500 nm was dramatically enhanced upon titration of Zn2+. As a result, an obvious fluorescence in green color was observed, corresponding to a 200-fold enhancement. A 205 nm Stokes shift avoided the interference of the excitation light on the emission intensity. The fluorescence titration curve showed that an adduct of 1:1 is formed, with K of 8.5* 106M-1, which was further confirmed by Job's plot. The response mechanism was studied by fluorescence spectroscopy, UV-visible spectroscopy, mass spectrometry. Meanwhile, with good membrane permeability and low toxicity, Cl has been applied to mark Zn2+ successfully in living cell.2. A probe which can recognize selectively Cu2+ in aqueous solution was developed. To Cl-Zn2+ system, the addition of trace amount Cu2+ caused a dramatic change in the emission spectra of Cl-Zn2+. The fluorescence intensity at 500 nm decreased gradually with the increasing concentration of Cu2+, and higher concentrations led to more efficient quenching. Such strong quenching may be caused by the change in the microenvironment around Cl and paramagnetism of Cu2+. The change in the microenvironment around Cl was also confirmed by a red shift in the maximum absorption wavelength from 298 to 304 nm. Furthermore, the fluorescence quenching values (Ⅰ/Ⅰ0) shows a good linear relationship with Cu2+ concentration for a certain range of concentrations. The response mechanism is based on the displacement of Zn2+ by Cu2+.3. A fluorescent chemical sensor PIPIP was synthesized, which can specifically recognize D-3-hydroxybutyric acid molecules in DMSO solvent. The free compound emits blue fluorescence in DMSO. Upon addition of D-3-hydroxybutyric acid, the system exhibits green fluorescence. Meanwhile the solution color changes from colorless to yellow. The mechanism was studied by UV-Vis and fluorescent technology. The mechanism was deduced by 1H NMR and ESI that intermolecular hydrogen bonds between PIPIP and D-3-hydroxybutyric acid formed. |
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