Synthesis And Recognition Properties Of Fluorescent Probes Based On Rhodamine And Anthraquinone Deravitives

Metal ions have wide range of applications in many fields, and the environmental and health problems caused by the metal ions gradually aroused widespread concern. Therefore, the detection of metal ions is of great significance. Several conventional analytical methods for metal ions detection, such as atomic absorption/emission spectrophotometry, and ion-coupled plasma emission-mass spectrometry are not only expensive and time-consuming in practice, but also requirement of highly trained individuals. Comparatively, fluorescence methods based on supramolecular chemistry show unique potential for sensitivity and selectivity for metal ions with relatively simple analysis protocols and have afforded essential basis in chemistry and biomedical systems.As a rare transition metal, palladium which deposited in soil and plants near highways and effected with sulfhydryl group containing amino acid, protein (casein, silk protein and some enzymes), DNA and other biological macromolecules (vitamin B6) can pollute water and harm human health. The design of selective and sensitive fluorescent chemosensors for the heavy transition metal (HTM) Pd2+ions is still a challenge because it is typical fluorescence quenchers.Up to now, only a few examples of chemosensors for palladium detections have been reported. Therefore, the design of novel and effective chemosensors for palladium detection with high selectivity and sensitivity in aqueous solutions under mild conditions is still required.Herein, two fluorescent chemosensors RPdl and RPd2based on a conjugate of phosphine and rhodamine B and rhodamine6G have been designed and synthesized, which take advantage of the selective affinity and chelating properties of phosphine ligands toward palladium species and high photostability of rhodamine fluorophore. The chemosensors showed excellent selectivity for Pd2+ions over relevant competing metal ions and anions with a strong fluorescent enhancement based on the mechanism of a strong Pd-P"N chelation and the ring opening of spirolactam of rhodamine in aqueous ethanol solution, thus resulting in the enhancement of fluorescence. The details are summarized as follows:The recognition properties of molecular probes were investigated by UV-visible absorption and fluorescence emission spectra. The chemosensors showed an excellent palladium selectivity with a detection limit to the10-9M and10-8M range in a wide pH span(RPdl:5.3-10.0, RPd2:4.9-8.6), which are lower than the WHO limit for palladium content in drug chemicals and can be used to analyze natural water samples. Among the metal ions examined, chemosensors showed a selective fluorescence increase only with Pd2+and form a1:1complex. Furthermore, the chemosensors was shown to be potential probes for the direct qualitative determinations of a wide range of palladium complex including Pd(Ⅱ) and Pd(0) species.The improper use of aluminum will produce some side effects and even threaten human health, excess aluminum ion accumulated in human body may cause serious illness such as Alzheimer’s disease and osteoporosis. In this paper, a highly selectivity fluorescent probe QAl for aluminum ion detection based on anthraquinone has been developed. The interaction between QAl and aluminum ion was investigated in detail by UV-visible absorption spectra and fluorescence emission spectra experiments. QAl showed good selective recognition ability for aluminum ion and can form a1:1complex in ethanol-H2O (v/v,1:1) solution. In the concentration of aluminum ion increased from0to100μM, the fluorescence intensity at600nm increased and at522nm decreased, meanwhile, the maximum absorption peak blue-shifted from532nm to490nm. The ratio change of absorption(A493/A330) and fluorescence signal (F600/522) presents a non-linear relationship and fits Sigmoidal formula, the dissociation constant Kd was deduced to be1.41X10"5M (R=0.999) and1.82×10-5M (R=0.998), respectively. In addition, the detection limit of QAl was estimated to be9.6×10-6M and the pH application range from3.01to10.06. The defect of QAl is the presence of anions will disturb the recognition ability for aluminum ion.The ion-induced water addition reaction of benzothiazole derivative1could change the molecular conjugate structure and spectroscopic properties. The research indicates the absorption of1decreased with Pd, otherwise, the fluorescence intensity increased; the presence of OCl-which concentration increased from0to100μM not only caused the decline of absorption until it disappears, but also caused a complete fluorescence quenching, the reason may be low concentration OCl-induced compound1occur water addition reaction and high concentration OCl-destroyed molecular structure because of its strong oxidative capacity. Other common anions and cations do not result similar changes. Therefore, compound1and the reaction mechanism have important guiding significance in design of novel fluorescent probes for detecting Pd2+and OCl-.