Synthesis And Properties Of Novel Pyrazole Fluorescence Probes Based On Rhodamine And Fluorescein Derivatives

The environmental pollution has became more and more serious with the development of economy,and heavy metal ion pollution is particularly serious..Heavy metal ions are difficult to biodegrade and they will be enriched in animals and plants,thereby causing various worldwide environmental and health problems every year.It is necessary to design and synthesize a kind of metal ion fluorescence probe which with simple operation,high sensitivity,strong anti-interference and wide application value.Pyrazole,a class of pentatomic heterocyclic compounds,which contain two adjacent nitrogen atoms.Because of their various chemical and biological properties,pyrazole has been widely used in many fields.Pyrazole derivatives own a largely closed?bond and a pair of lone electrons in one of the nitrogen atoms,which indicate that pyrazole could be used as a raw material for the synthesis of a series of fluorescent probes.Fluorescein and rhodamine,as common pigments and fluorescent dyes,have good optical and physical properties,such as high molar extinction coefficient,excitation and emission wavelength in the visible region and good conjugation,etc.It is an important material for bioluminescence probes,and have been widely used in the field of bioluminescence probes in recent years.The main research contents and conclusions are listed as follows:?1?Firstly,fluorescein derivative?fluorescein hydrazide?was synthesized by using fluorescein and hydrazine hydrate as raw materials.Pyrazole and p-fluorobenzaldehyde were used as raw materials to obtain pyrazole-based fluorobenzaldehyde.Then,Rhodamine 6G hydrazide was reacted with pyrazolyl p-fluorobenzaldehyde,and the target probe Pyr-Flu.was obtained.The structure of the target product was characterized by IR and NMR,and the characterization results show that the probe was synthesized successfully.The energy distribution of molecular LUMO and HOMO orbitals had been investigated by using density functional theory and which was an foe the theory of experimental reaction and the mechanism of fluorescence generation on the theoretical level.The UV properties,fluorescence properties and metal ion detection ability of the target product were also studied by UV absorption and fluorescence emission spectra.The results shown that the probe Pry-Flu has a specific detection ability for Ni²⁺.In addition,a series of experiments were designed to study the properties of molecular probes.?2?Two kinds of Rhodamine derivatives?Rhodamine 6G ethylenediamine and Rhodamine 6G hydrazine hydrate?were obtained by reacting with ethylenediamine and hydrazine hydrate,respectively.Pyrazolyl p-fluorobenzaldehyde was synthesized by reaction of pyrazole with p-fluorobenzaldehyde.Two kinds of Rhodamine derivatives?Rhodamine 6G ethylenediamine and Rhodamine 6G hydrazine hydrate?were reacted with pyrazolyl p-fluorobenzaldehyde,and two novel probe molecules Pry-R6G and Pyr-Rhy were obtained.Their structures of these were characterized by IR and NMR.The results shown that the probe molecules Pry-R6G and Pyr-Rhy were synthesized successfully.The probes were detected by UV absorption spectrum and fluorescence emission spectrum.It was found that when the probe molecule Pry-R6G and Pyr-Rhy were combined with Al³⁺and Hg²⁺,respectively,the color of the probe solution change and the fluorescence intensity increase obviously.This indicates that the probe Pry-R6G and Pyr-Rhy have specific detection for Al³⁺and Hg²⁺,respectively,and can be used to detect the two metal ions through naked eye and fluorescence change.At the same time,the density functional theory was used to optimize the probe molecule,and the energy distribution of the molecular LUMO and HOMO orbitals were explored,which provided an effective theoretical guide for the experiment.?3?The nuclear magnetic titration,infrared titration and Job's curves of three probe molecules were studied,and the working mechanism of the probe molecules were predicted verified by combining the experimental results.At the same time,the reversibility and anti-interference of probe molecule were studied by colorimetric experiment,reversibility experiment and anti-interference experiment.The results showed that the specific detection of metal ion by probe molecule was reversible.And which can achieve naked eye detection,and strong anti-interference ability.The innovation of this paper:1.Three kinds of Schiff base fluorescent probes were synthesized by organically combining pyrazole with fluorescein and rhodamine.2.The synthesized fluorescent probe can specifically identify metal ions with high sensitivity,strong fluorescence,visual detection,strong anti-interference ability,wide range of use of pH and reusable.Importantly,they can be used in the detection in water environment.3.The working mechanism of fluorescent probes was explored,and the working mechanism of probe molecule was put forward.