CN112029075A

CN112029075A - Ionized fluorenyl pyridine conjugated polymer and preparation method and application thereof

Info

Publication number: CN112029075A
Application number: CN202010858531.XA
Authority: CN
Inventors: 宫琳丹; 刘倩南; 范路安; 刘文宇; 杜松辉; 郑文岐; 张博
Original assignee: Harbin Engineering University
Current assignee: Harbin Engineering University
Priority date: 2020-08-24
Filing date: 2020-08-24
Publication date: 2020-12-04

Abstract

The invention belongs to Fe in an aqueous solution system³⁺、Cu²⁺And Co²⁺In particular to an ionized fluorenyl pyridine conjugated polymer and a preparation method and application thereof. The invention designs an ionized fluorenyl pyridine conjugated polymer with a main chain containing a structure capable of capturing metal ion imine bonds (-C ═ N-) and a preparation method thereof, wherein the synthesized fluorenyl pyridine conjugated polymer has the advantages of simple preparation process, low cost and high yield. The ionized fluorenyl pyridine conjugated polymer can be used for preparing and identifying Fe³⁺，Cu²⁺And Co²⁺The fluorescent sensing material of (1). The fluorescent sensing material not only has optical activity in various pH environments and different polar solvent environments, but also has optical activity in various pH environments and different polar solvent environmentsCan rapidly identify Fe in aqueous solution³⁺，Cu²⁺And Co²⁺Three kinds of metal ions. And the detection limit is low, and the specificity recognition effect is good.

Description

Ionized fluorenyl pyridine conjugated polymer and preparation method and application thereof

Technical Field

The invention belongs to Fe in an aqueous solution system³⁺、Cu²⁺And Co²⁺In particular to an ionized fluorenyl pyridine conjugated polymer and a preparation method and application thereof.

Background

Fluorene based polymers are the most promising electroluminescent materials. The fluorescent material plays an important role in the fields of biological systems, metal ion recognition and the like, for example, Bszan research group finds that a water-soluble cationic fluorenyl polymer detects DNA and protein; wanglixiang combined fluorenyl polymer pair Fe with side chain having phosphate substituent³⁺Has good selectivity. The fluorenyl conjugated polymer as a fluorescent sensor has the characteristics of small external interference, high sensitivity and the like, and is widely applied to the fields of light emitting diodes, environmental pollution monitoring, solar cells and the like.

Metal ions play a key role in life activities and environmental quality. They are mutually coordinated and, in case of an imbalance in the content, induce the corresponding disease. For example, Fe³⁺Is a constituent of hemoglobin and is deficient in Fe³⁺Iron deficiency anemia can be caused, and excessive liver fibrosis and hepatoma can be caused; cu²⁺Is an important component of protease in the body, and is deficient in Cu²⁺Alzheimer disease and Parkinson disease can be caused, and poisoning is easily caused by excessive dosage; co²⁺Is vitamin B₁₂Important component of, lack of Co²⁺Pernicious anemia can be produced, and excessive toxicity can cause heart failure and other toxic reactions. Therefore, the detection of the metal ions is always a focus of attention, and compared with the spectrophotometry, the inductively coupled plasma mass spectrometry and the atomic absorption spectrometry, the research is based on the identification of the flourenyl polymer fluorescent sensing material on the metal ions.

Disclosure of Invention

The invention aims to provide an ionized fluorenyl pyridine conjugated polymer.

The purpose of the invention is realized by the following technical scheme: the chemical formula is:

the invention also aims to provide a preparation method of the ionized fluorenyl pyridine conjugated polymer.

The purpose of the invention is realized by the following technical scheme: the method comprises the following steps:

step 1: 2, 7-dibromo fluorene and tetrabutyl ammonium iodide were added to 1, 6-dibromo hexane in N₂Stirring for 10min under the environment, adding 50% NaOH aqueous solution, and reacting for 12h at the temperature of 60 ℃; the molar ratio of the 1, 6-dibromohexane to the 2, 7-dibromofluorene is 1: 3;

step 2: cooling the reaction system to room temperature, dissolving the reaction product with chloroform, extracting in saturated salt water for 5 times, adding anhydrous magnesium sulfate into the organic phase, stirring, and filtering; removing excessive 1, 6-dibromohexane from the filtrate by a rotary evaporator to obtain a yellow viscous product;

and step 3: separating the obtained yellow viscous product by column chromatography, wherein the eluant is petroleum ether; removing the eluent from the product fraction after separation and purification, and drying for 24 hours in vacuum to obtain white solid 9, 9-di (bromohexyl) -2, 7-dibromofluorene;

and 4, step 4: adding absolute ethyl alcohol into a low-temperature reactor, cooling to-78 ℃, putting a reaction bottle filled with THF into the reactor, adding 9, 9-di (bromohexyl) -2, 7-dibromofluorene into the reaction bottle, and reacting the solution in a reactor under the action of N₂Adding n-butyllithium under the environment, stirring for 1h, adding DMF, and reacting for 2.5 h; the molar ratio of DMF to 9, 9-di (bromohexyl) -2, 7-dibromofluorene is 1: 4;

and 5: slowly raising the temperature of the reactor to room temperature for reaction for 12 hours; neutralizing the alkaline substance generated by the reaction with dilute hydrochloric acid until the pH of the solution is 7;

step 6: adding chloroform and saturated salt water into a reactor for extraction, adding anhydrous magnesium sulfate into an organic phase for drying, filtering, and performing rotary evaporation on a filtrate to obtain a yellow-green viscous crude product;

and 7: separating and purifying the obtained yellow-green viscous crude product by column chromatography, wherein an eluent is dichloromethane and n-hexane in a volume ratio of 2: 3, a mixed solvent; carrying out rotary evaporation on the separated and purified product again, and drying in vacuum to obtain a white viscous solid 9, 9-di (bromohexyl) -2, 7-bifluorenal;

and 8: adding 9, 9-di (bromohexyl) -2, 7-bifluorenal and 2, 3-diaminopyridine into a reaction bottle, and adding anhydrous LiCl and N as catalysts in a polymerization solvent DMF₂Reacting for 12 hours under the conditions of environment, temperature of 100 ℃ and condensation reflux;

and step 9: after the reaction bottle is returned to the room temperature, transferring the liquid in the reaction bottle into an eggplant-shaped bottle, decompressing and steaming, and slowly dripping the liquid in the reaction bottle into ice water for precipitation; centrifuging the precipitated black solid, and drying in vacuum to obtain a black solid polymer, namely a fluorenyl pyridine conjugated polymer;

step 10: dissolving the fluorenyl pyridine conjugated polymer in THF, adding aqueous trimethylamine solution, and reacting at room temperature N₂Reacting for 72 hours in the environment;

step 11: transferring the liquid after the reaction to an eggplant-shaped bottle, and performing rotary evaporation under reduced pressure to obtain powder; and (3) putting the powdery product into a vacuum drying oven for drying for 24h to obtain the ionized fluorenyl pyridine conjugated polymer.

The invention also aims to provide application of the ionized fluorenyl pyridine conjugated polymer.

The purpose of the invention is realized by the following technical scheme: for preparing and identifying Fe³⁺，Cu²⁺And Co²⁺The fluorescent sensing material of (1).

The invention has the beneficial effects that:

the invention designs an ionized fluorenyl pyridine conjugated polymer with a main chain containing a structure capable of capturing metal ion imine bonds (-C ═ N-) and a preparation method thereof, wherein the synthesized fluorenyl pyridine conjugated polymer has the advantages of simple preparation process, low cost and high yield. The ionized fluorenyl groupPyridine conjugated polymer can be used for preparing and identifying Fe³⁺，Cu²⁺And Co²⁺The fluorescent sensing material of (1). The fluorescent sensing material not only has optical activity in various pH environments and different polar solvent environments, but also can rapidly identify Fe in aqueous solution³⁺，Cu²⁺And Co²⁺Three kinds of metal ions. And the detection limit is low, and the specificity recognition effect is good.

According to the invention, 2, 7-dibromofluorene is used as fluorescein, a dialdehyde monomer is synthesized through a secondary substitution reaction, and then the dialdehyde monomer and 2, 3-diaminopyridine are subjected to a polycondensation reaction to obtain an ionized fluorenylpyridine conjugated polymer fluorescent sensing material, and then the nuclear magnetic hydrogen spectrum and the infrared spectrum are utilized to characterize the structure of the product. It has a constant increase in UV absorbance and decrease in fluorescence intensity in acidic pH 4 to pH 10 alkaline PBS buffer solutions, as in H₂O, Methanol and CDCl₃The 7 common solvents with different polarities show excellent solubility, optical activity and larger Stokes shift (43-51 nm). Fe³⁺And Cu²⁺The fluorescence intensity of the polymer is reduced by 95 percent and 45 percent, and Co²⁺The fluorescence response of the iron core is increased to 1.77 times of the original fluorescence response, the above sensitive fluorescence response is balanced within 8min, and the fluorescence response and Fe are balanced³⁺，Cu²⁺And Co²⁺Respectively in 1-10, 1-5 and 1-10 mu mol L^-1The concentration range of (A) shows good linear relation, and the detection limit can be as low as 0.1 mu mol L^-1，0.077μmol L^-1And 0.11. mu. mol L^-1Trace detection level of (a). Job-plot results show that the polymer is associated with Fe³⁺，Cu²⁺And Co²⁺The complex stoichiometric ratios are all 1: 1. the polymer fluorescent sensing material has the capability of identifying three metal ions without being interfered by pH environment difference and other common metal ions, and shows high environmental adaptability and high selectivity.

Drawings

FIG. 1 is a drawing of Compound 1¹H NMR Spectrum (CDCl)₃-d₆，25℃，500MHz)。

FIG. 2 is a drawing of Compound 2¹H NMR Spectrum (CDCl₃-d₆，25℃，500MHz)。

FIG. 3 shows polymer 3¹H NMR Spectrum (DMSO-d)₆，80℃，500MHz)。

FIG. 4 shows polymer 4¹H NMR Spectrum (DMSO-d)₆，80℃，500MHz)。

FIG. 5 shows FT-IR spectra of Compound 1, Compound 2, Polymer 3 and Polymer 4.

FIG. 6 shows an ionized fluorenylpyridine conjugated polymer (10. mu. mol L)^-1) Normalization of UV-visible absorption spectra (left, black) and fluorescence emission spectra (right, red) (λ) in different solvents_ex＝340nm)。

FIG. 7 shows PBS buffer solutions (5mmol L) at different pH^-1) Middle ionized fluorenylpyridine conjugated polymer (10. mu. mol L)^-1) Ultraviolet-visible absorption spectrum (left, real) and fluorescence emission spectrum (right, virtual) (lambda)_ex＝340nm)。

FIG. 8 shows the reaction mixture in PBS buffer (5mmol L)^-1pH 7), ionized fluorenylpyridine conjugated polymer (10 μmol L)^-1) Adding different metal ions (200 mu mol L)^-1) Fluorescence emission spectrum (λ)_ex＝340nm)。

FIG. 9 shows the reaction mixture in PBS buffer (5mmol L)^-1pH 7) of different metal ions (200. mu. mol L)^-1) Ionizing fluorenylpyridine conjugated Polymer in the Presence (10. mu. mol L)^-1) Relative intensity of fluorescence (λ)_ex＝340nm)。

FIG. 10 shows PBS buffer solutions (5mmol L) at different pH^-1) Middle ionized fluorenylpyridine conjugated polymer (10. mu. mol L)^-1) Adding Fe³⁺，Cu²⁺，Co²⁺(200μmol L^-1) Front and rear fluorescence intensity (. lamda.)_ex＝340nm)。

FIG. 11 shows the reaction mixture in PBS buffer (5mmol L)^-1pH 7), ionized fluorenylpyridine conjugated polymer (10 μmol L)^-1) For Fe³⁺，Cu²⁺，Co²⁺(200μmol L^-1) Fluorescence intensity changes with time (0min-14min) (lambda)_ex＝340nm)。

FIG. 12(a) is a schematic view of a PBSBuffer solution (5 mmol)^-1pH 7), ionized fluorenylpyridine conjugated polymer (10 μmol L)^-1) Fluorescence emission spectrum of (1) with Fe³⁺The concentration changes.

FIG. 12(b) shows an ionized fluorenylpyridine conjugated polymer (10. mu. mol L) at 382nm^-1) Fluorescence intensity of (3) and Fe³⁺Concentration relationship (λ) of_ex＝340nm)。

FIG. 12(c) is a solution in PBS buffer (5 mmol)^-1pH 7), ionized fluorenylpyridine conjugated polymer (10 μmol L)^-1) Fluorescence emission spectrum of (1) with Cu²⁺The concentration changes.

FIG. 12(d) shows an ionized fluorenylpyridine conjugated polymer (10. mu. mol L) at 382nm^-1) Fluorescence intensity of (2) and Cu²⁺Concentration relationship (λ) of_ex＝340nm)。

FIG. 12(e) is a solution in PBS buffer (5 mmol)^-1pH 7), ionized fluorenylpyridine conjugated polymer (10 μmol L)^-1) Fluorescence emission spectrum of (2) with Co²⁺The concentration changes.

FIG. 12(f) is an ionized fluorenylpyridine conjugated polymer (10. mu. mol L) at 382nm^-1) Fluorescence intensity of (3) and Co²⁺Concentration relationship (λ) of_ex＝340nm)。

FIG. 13(a) is a solution in PBS buffer (5 mmol)^-1pH 7) ionized fluorenylpyridine conjugated polymer (10 μmol L)^-1) For the recognition of Fe³⁺Interference rejection study (lambda)_ex＝340nm)。

FIG. 13(b) is a solution in PBS buffer (5 mmol)^-1pH 7) ionized fluorenylpyridine conjugated polymer (10 μmol L)^-1) For identifying Cu²⁺Interference rejection study (lambda)_ex＝340nm)。

FIG. 13(c) is a solution in PBS buffer (5 mmol)^-1pH 7) ionized fluorenylpyridine conjugated polymer (10 μmol L)^-1) For identification of Co²⁺Interference rejection study (lambda)_ex＝340nm)。

FIG. 14 is a table of the basic optical properties of polymers in different solvents (λ)_ex＝340nm)。

FIG. 15 shows the pH 7 in PBS bufferIonized fluorenyl pyridine conjugated polymer pair Fe³⁺，Cu²⁺，Co²⁺The detection table of (1).

FIG. 16 is a diagram of the synthetic scheme for ionized fluorenylpyridine conjugated polymers.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

The invention introduces a synthetic method of an ionized fluorenyl pyridine conjugated polymer fluorescent sensing material with a main chain containing a ligand capable of capturing metal ion imine bond (-C ═ N-), which has simple synthetic preparation process, low cost and high yield. The fluorescent sensing material not only has optical activity in various pH environments and different polar solvent environments, but also can rapidly identify Fe in aqueous solution³⁺，Cu²⁺And Co²⁺Three kinds of metal ions. And the detection limit is low, and the specificity recognition effect is good.

Using Avance III-500 nuclear magnetic resonance spectrometer of Bruker company in Switzerland at 25 deg.C or 80 deg.C, using deuterated chloroform (CDCl)₃-d₆) And deuterated dimethyl sulfoxide (DMSO-d)₆) The structure of the synthesis product is characterized for the solvent. Adopts SPECTRUM100 model FT-IR Fourier infrared spectrometer of PE company in America in the wavelength range of 4000-^-1And preparing a sample by using a potassium bromide sheet, scanning for 8 times, and characterizing the structure of a synthetic product at room temperature.

The UV-visible absorption spectrum of the sample is tested by adopting a Meipu UV-6100 spectrophotometer under the condition of room temperature, the sample is contained by a quartz cuvette with the size of 10 multiplied by 10mm, the volume of the sample is 2000 mu l, and the scanning range is 200 plus 800 nm. Fluorescence spectra were measured at room temperature with a PE LE55 fluorescence spectrophotometer in USA, using a 10 × 10mm quartz cuvette with a sample volume of 3000 μ l, an excitation wavelength of 330nm, a slit width of 7nm, a scanning range of 200 and 800nm, and a scanning speed of 300 nm/min.

First, the optical properties of the ionized fluorenylpyridine conjugated polymer in different solvents and different pH (

pH

4, 5, 6, 7, 8, 9, 10) environments were measured for uv-vis absorption spectrum and fluorescence emission spectrum, and in H₂O，DMF，DMSO，Methanol，THF，Acetone，CDCl₃Solubility in solvents of different polarity is common. And 1mol L of quinine sulfate^-1The sulfuric acid solution of (a) was used as a standard to estimate the fluorescence quantum yield of the polymer. The ionized fluorenylpyridine conjugated polymer was then dissolved in PBS (5mmol L) at pH 7^-1) In buffer solution, make 10. mu. mol L^-1Sample solutions to which 20 times equivalent of metal ion chloride (Ca) was added²⁺，Fe²⁺，Fe³⁺，Mn²⁺，Ni²⁺，Co²⁺，Cu²⁺，Zn²⁺，Cr³⁺，Hg²⁺) Then, the difference of fluorescence emission spectrum is used to complete the Fe-Fe fluorescence detection³⁺，Cu²⁺，Co²⁺And (3) specific recognition research of three metal ions. In addition, the ionized fluorenyl pyridine conjugated polymer is examined to Fe under the environment of

pH

4, 5, 6, 7, 8, 9 and 10³⁺，Cu²⁺，Co²⁺Fluorescence quenching behavior and time response. Finally passing through different concentrations of Fe³⁺，Cu²⁺，Co²⁺Obtaining the linear range for detecting three metal ions according to the relation of fluorescence quenching efficiency of the polymer at 382nm, establishing a linear equation, and calculating Fe³⁺，Cu²⁺，Co²⁺The detection limit of (2).

According to the invention, 2, 7-dibromofluorene is used as fluorescein, a dialdehyde monomer is synthesized through a secondary substitution reaction, and then the dialdehyde monomer and 2, 3-diaminopyridine are subjected to a polycondensation reaction to obtain an ionized fluorenylpyridine conjugated polymer fluorescent sensing material, and then the nuclear magnetic hydrogen spectrum and the infrared spectrum are utilized to characterize the structure of the product. It has a constant increase in UV absorbance and decrease in fluorescence intensity in acidic pH 4 to pH 10 alkaline PBS buffer solutions, as in H₂O, Methanol and CDCl₃The 7 common solvents with different polarities show excellent solubility, optical activity and larger Stokes shift (43-51 nm). Fe³⁺And Cu²⁺The fluorescence intensity of the polymer is reduced by 95 percent and 45 percent, and Co²⁺The fluorescence response of the fluorescent probe is increased to 1.77 times of the original fluorescence response, the above sensitive fluorescence response reaches the balance within 8min,and this fluorescent response is associated with Fe³⁺，Cu²⁺And Co²⁺Respectively in 1-10, 1-5 and 1-10 mu mol L^-1The concentration range of (A) shows good linear relation, and the detection limit can be as low as 0.1 mu mol L^-1，0.077μmol L^-1And 0.11. mu. mol L^-1Trace detection level of (a). Job-plot results show that the polymer is associated with Fe³⁺，Cu²⁺And Co²⁺The complex stoichiometric ratios are all 1: 1. the polymer fluorescent sensing material has the capability of identifying three metal ions without being interfered by pH environment difference and other common metal ions, and shows high environmental adaptability and high selectivity.

Synthesis of ionized fluorenyl pyridine conjugated polymer

1.1 Synthesis of Compound 1(9, 9-bis (bromohexyl) -2, 7-dibromofluorene)

4.86g of 2, 7-dibromofluorene and 0.11g of tetrabutylammonium iodide were mixed in a molar ratio to 2, 7-dibromofluorene of about 1: 3, 12ml of 1, 6-dibromohexane was added thereto in the presence of N₂Stirring for 10min under the environment, adding 16ml of 50% NaOH aqueous solution, and reacting under the condition of N₂The reaction is carried out for 12 hours at the temperature of 60 ℃ under the environment.

After the reaction system was cooled to room temperature, the reaction product was dissolved in a large amount of chloroform, extracted 5 times in saturated saline, and the organic phase was stirred with anhydrous magnesium sulfate and filtered. The filtrate was passed through a rotary evaporator to remove excess 1, 6-dibromohexane to give a yellow viscous product. Separating the obtained crude product by column chromatography, wherein the eluent is petroleum ether. After removal of the eluent from the product fractions, vacuum drying was carried out for 24 hours to give 4.36g of a white solid in 44.7% yield.

1.2 Synthesis of Compound 2(9, 9-bis (bromohexyl) -2, 7-bifluorenal)

Adding anhydrous ethanol into a low-temperature reactor, cooling to-78 deg.C, placing a reaction bottle containing 150ml of THF into the reactor, adding 13.3 g of compound, and adding N₂20ml of n-butyllithium are added to the reaction mixture under ambient conditions and stirred for 1 hour, in a molar ratio of 1: 4, 2ml of DMF was added thereto and the mixture was reacted for 2.5 hours, followed by slowly raising the temperature of the reactor to room temperature and reacting for 12 hours. The alkaline material formed by the reaction was neutralized with dilute hydrochloric acid until the solution had a pH of 7.

Adding chloroform and saturated saline solution into the reaction product for extraction, adding anhydrous magnesium sulfate into the organic phase for drying, filtering, and performing rotary evaporation on the filtrate to obtain a yellow-green viscous crude product. And (3) separating and purifying the crude product by column chromatography, wherein the elution machine is formed by mixing dichloromethane and n-hexane in a volume ratio of 2: 3, the obtained product is again rotary evaporated and dried in vacuum to finally obtain 0.3g of white viscous solid with the yield of 11%.

1.3 Synthesis of Polymer 3 (fluorenylpyridine conjugated Polymer)

Adding 0.11g of compound 2 into a 100ml reaction flask, adding 0.065g of (9, 9-di (bromohexyl) -2, 7-bifluorenal and 2, 3-diaminopyridine in a molar ratio of 1: 3)2, 3-diaminopyridine, DMF as a polymerization solvent, anhydrous LiCl as a catalyst and reacting under the conditions of N₂The temperature is 100 ℃, and the condensation reflux is carried out for 12 hours.

After the room temperature is recovered, the liquid after the reaction is transferred to an eggplant-shaped bottle, reduced pressure rotary evaporation is carried out until 4ml of liquid is remained, then the liquid is slowly dripped into 500ml of ice water for precipitation, a black solid is separated out, centrifugation and vacuum drying are carried out, and finally 0.069g of the black solid is obtained, and the black solid polymer 3 with the yield of 46.7% is obtained.

1.4 Synthesis of Polymer 4 (ionized fluorenylpyridine conjugated Polymer)

40mg of Polymer 3 was placed in a 100ml reaction flask, dissolved in 20ml of THF, and 25ml of an aqueous trimethylamine solution was added thereto at room temperature under N₂And reacting for 72 hours in the environment. The liquid after the reaction was transferred to an eggplant type bottle, rotary-evaporated under reduced pressure to a powder, and the product was dried in a vacuum oven for 24 hours to obtain a black solid polymer 4, an ionized fluorenylpyridine conjugated polymer, in a yield of 85.8%.

Second, nuclear magnetic hydrogen spectrum analysis

FIG. 1 is a drawing of Compound 1¹H NMR spectrum, the product has 7 kinds of different proton peaks, from low field to high field, and the hydrogen proton peaks are assigned as follows:¹H NMR(500MHz，CDCl₃，TMS，20℃，ppm)＝7.53-7.35(m，Ar-H，6H)，3.33-3.28(t，-CH₂-Br，4H),1.94-1.87(m,-(CH₂-CH₂)₅Br，4H)，1.73-1.63(m，-CH₂-CH₂ Br)，1.22-1.15(m，-CH₂-(CH₂)₄Br，4H)，1.13-1.01(m,-CH₂-(CH₂)₂Br，4H)，0.61-0.50(m，-CH₂-(CH₂)₃br, 4H). The analysis map shows that the target product is successfully synthesized and can be used for the next experiment.

FIG. 2 is a drawing of Compound 2¹H NMR spectrum, the product has 8 different proton peaks, from low field to high field, and the hydrogen proton peaks are assigned as follows:¹H NMR(500MHz，CDCl₃，TMS，20℃，ppm)＝10.03(s，O＝CH，2H)，7.97-7.91(m，Ar-H，6H)，3.27-3.22(t，-CH₂-Br，4H)，2.11-2.06(m，-CH₂-(CH₂)₅Br，4H)，1.67-1.57(m，-CH₂-CH₂ Br，4H)，1.19-1.09(m，-CH₂-(CH₂)₄Br,4H)，1.09-1.05(m，-CH₂-(CH₂)₂Br，4H)，0.61-0.53(m，-CH₂-(CH₂)₃br, 4H). The analytical pattern showed that the dialdehyde monomer was successfully synthesized.

FIG. 3 shows polymer 3¹The HNMR spectrum, the presence of an imine peak at 8.4ppm, demonstrates the occurrence of an aldol condensation reaction in the third reaction step, thus demonstrating the successful preparation of polymer 3, which is a 46.7% yield. And the product has high purity and can be used for the next experiment.

FIG. 4 shows polymer 4¹The HNMR spectrogram shows that the peak at 3.7ppm is the peak of methyl hydrogen of the quaternary ammonium group, the occurrence of the peak proves that the preparation of the polymer 4 is successful, the reaction yield of the step is 85.8 percent, and the analysis chart shows that the polymer 4 is successfully synthesized and has good purity, so that the method can be used for the next step of experiments.

Three, infrared spectral analysis

From FIGS. 5(1) and 5(2), it can be seen that the substance is 2732cm^-1And 1694cm^-1The peaks are characteristic peaks of aldehyde groups respectively. Attribution is as follows, 2732cm^-1Is the stretching vibration peak of (-C-H) in aldehyde group, 1694cm^-1Is the stretching vibration peak of (-C ═ O) in aldehyde group, 3468cm^-1Stretching vibration of benzene ring hydrogen (Ph-H)Peak, 2929cm^-1Is an alkyl chain (- (CH)₂)₄-) has a peak of stretching vibration of 1604cm^-1751cm as a skeletal vibration absorption peak of benzene ring (Ph)^-1Is an alkyl chain (- (CH)₂)₄-) plane rocking vibration peaks. Finally, the successful synthesis of compound 2 can be confirmed by qualitative analysis.

FIG. 5(3) is a FT-IR spectrum of Polymer 3, which is 3328cm in comparison with the second dialdehyde monomer^-12931cm of stretching vibration peak of benzene ring hydrogen (Ph-H)^-1And 756cm^-1The alkyl vibration peak still exists, and 2732cm is used^-1And 1694cm^-1The peak of aldehyde groups had disappeared and finally the polymer was 1605cm^-1A new vibration peak appears, and the infrared absorption peak of the imino group usually appears at 1600-^-1In combination with the structure of the polymer 3, the infrared absorption peak with an imino group at the peak can be determined, and finally, the successful synthesis of the polymer 3 can be determined through qualitative analysis.

FIG. 5(4) is an FT-IR spectrum of Polymer 4, which is 3454cm in comparison with Polymer 3 for Polymer 4^-12931cm, which is located at the stretching vibration peak of benzene ring hydrogen (Ph-H)^-1And 752cm^-1Vibration peak of alkyl group and 1632cm^-1The peak of the imino vibration still exists while the polymer 4 is at 1101cm^-1A new vibration peak appears, and the infrared absorption peak of (C-N) in the tertiary amine group usually appears at 1360-^-1In the meantime, in combination with the structure of the polymer 4, the infrared absorption peak of the tertiary amine group can be determined, and finally, the successful synthesis of the polymer 4 can be determined through qualitative analysis.

Optical property of tetra (ionized) fluorenylpyridine conjugated polymer

4.1 optical Properties of ionized fluorenylpyridine conjugated polymers in different solvents

As can be seen from fig. 6, the ultraviolet-visible absorption spectrum and the fluorescence emission spectrum show that the ionized fluorenyl pyridine conjugated polymer has good optical activity in different solvent environments. The ultraviolet-visible absorption spectrum range of the compound is between 233nm and 500nm, and the highest peak of the compound is between 333nm and 339 nm; the fluorescence emission spectrum range appears at 370nm650nm, with the highest peak occurring in the 382nm-388nm range. This is because the polarity of the solvent has an influence on both the aggregation state and the extension of the fluorene-based polymer, which is reflected in the difference of the fluorescence emission spectra. Ionized fluorenylpyridine conjugated polymers in CDCl₃Maximum Stokes shift of 51nm at H₂The Stokes shift in O is the smallest and 43nm, and the Stokes shift in other solvents is larger and is between 46nm and 50 nm. It is believed that materials with larger Stokes shift values are more suitable for use as fluorescent sensing materials. The fluorescence quantum efficiency of the polymer under different solvents is calculated to be between 0.8 and 4.6 percent by taking quinine sulfate as a standard substance. The results in FIG. 14 show that the polymer has better solubility in 7 common solvents, mainly because the main chain is hydrophobic and the side chain quaternary ammonium cation is hydrophilic, so that the polymer can be completely dissolved in H with strong polarity₂O, DMF, DMSO, THF, methanol solvent, in general polar solvent such as chloroform, acetone, etc.

4.2 optical Properties of ionized fluorenyl pyridine conjugated polymers in different pH environments

As shown in fig. 7, in the process of increasing pH from 4 to 10, the position of the maximum absorption peak of the ionized fluorenyl pyridine conjugated polymer in the uv-visible absorption spectrum is about 338nm, and the peak shape is not significantly different, but when pH is 4, the uv-visible absorption spectrum is the lowest, and when pH is 10, the absorption spectrum reaches the highest value and the spectrum is red-shifted by 2 nm. In contrast, the maximum emission peak of the fluorescence emission spectrum is around 382nm, the fluorescence spectrum is strongest at pH 4, and as pH is increased to pH 10, the fluorescence spectrum of the polymer is minimized and the spectrum is blue-shifted by 2.5 nm. The above spectral changes are due to H in solution⁺Or OH^-The interaction with the polymer can promote or inhibit electron transfer in the system to a certain extent. Ionized fluorenylpyridine conjugated polymers have rigid fluorenylfluorescent chromophores, and the fluorescence enhancement under acidic conditions may be due to H⁺Can possibly form hydrogen bonds with N atoms in-C ═ N-, and basic property caused by charge transfer (ICT) of fluorene ring fluorescence chromophore unit electrons in molecules is blockedReduced fluorescence under conditions which may be the Lewis acidity of the quaternary ammonium cation of the polymer side chain, and OH^-Acid-base combination is generated, the hydrophobicity of the system is increased after the charges are neutralized, and the polymer which is originally arranged orderly and well stretched under the action of the repulsion force of the positive charge side chain of the side chain is subjected to agglomeration or the pi-pi accumulation of the main chain, so that the fluorescence of the polymer is quenched.

Fifthly, ionizing fluorenyl pyridine conjugated polymer pair Fe³⁺，Cu²⁺And Co²⁺Fluorescent identification of

5.1 ionizing fluorenyl pyridine conjugated Polymer Pair Fe³⁺，Cu²⁺And Co²⁺Specific fluorescent response of

FIG. 8 and FIG. 9 show the fluorescence emission spectrum change and the fluorescence relative intensity of the ionized fluorenyl pyridine conjugated polymer after different metal ions are added. Respectively adding Ca into polymer buffer solution system by taking 340nm as fluorescence excitation wavelength²⁺，Fe²⁺，Mn²⁺，Zn²⁺，Ni²⁺，Cr³⁺，Hg²⁺When the Fe is added into the polymer buffer solution system, the fluorescence spectrum of the polymer does not change obviously³⁺，Cu²⁺And Co²⁺Of (i) Fe³⁺，Cu²⁺The addition of (2) causes a spectral dip, while Co²⁺The addition of (b) causes the spectrum to rise. When Fe is added to the polymer system³⁺When the fluorescence intensity of the polymer at 382nm decreased to 0.05 times of the initial value, Cu was added to the polymer system²⁺When this occurs, the fluorescence intensity of the polymer decreases to 0.55 times the initial value. In contrast, when Co is added to the polymer system²⁺In this case, the fluorescence intensity of the polymer was increased to a certain extent, and the fluorescence intensity was increased by 1.77 times as much as the original intensity. The fluorescent chromophore fluorenyl group on the main chain of the ionized fluorenyl pyridine conjugated polymer contains pi-pi electrons, and forms a single-double bond alternating conjugated structure together with imine bonds and pyridine rings in the main chain, and the structural characteristic enables the main chain of the polymer to have a larger electron delocalization range. The N atom in the main chain imine bond is susceptible to Fe with d orbital not filled with electrons³⁺And Cu²⁺Coordination occursThe reaction forms a stable complex. On the other hand Fe³⁺And Cu²⁺Having paramagnetism in Fe³⁺And Cu² ⁺Fe in the complex³⁺And Cu²⁺The electrons at the center tend to be in a high spin state, the electrons in the higher energy orbitals are unstable, and quenching of fluorescence can be caused by the action of photo-induced Electron Transfer (PET) from the polymer to the center of the metal ion. And with Fe³⁺And Cu²⁺In contrast, Co is reported in the literature²⁺Coordination to the polymer may be followed by activation of an Intramolecular Charge Transfer (ICT) process, which significantly enhances the Fluorescence of the polymer by a chelate Enhanced Fluorescence (CHEF) mechanism.

5.2 ionized fluorenyl pyridine conjugated polymer Fe in different pH environments³⁺，Cu²⁺And Co²⁺Specific fluorescent response

FIG. 10 examines the ionized fluorenylpyridine conjugated polymer vs. Fe under 7 different acidity environments with pH from 4 to 10³⁺，Cu²⁺，Co²⁺Fluorescence quenching behavior of three metal ions. With 340nm as the excitation wavelength, the initial fluorescence intensity of the polymer is continuously reduced along with the continuous increase of pH, and Fe³⁺，Cu²⁺All the addition of (A) effectively quenches the fluorescence, and Co²⁺But enhances its fluorescence. Therefore, the ionized fluorenyl pyridine conjugated polymer can effectively detect and identify Fe under different pH environments³⁺，Cu²⁺，Co²⁺。

5.3 ionizing fluorenyl pyridine conjugated Polymer Pair Fe³⁺，Cu²⁺And Co²⁺Time response of fluorescence recognition

The identification of metal ions by a fluorescence sensor based on a metal complexing mechanism is a process from the beginning of reaction to the equilibrium, and FIG. 11 shows that at 382nm, an ionized fluorenylpyridine conjugated polymer and Fe are respectively³⁺，Cu²⁺，Co²⁺The fluorescence intensity of (a) is varied with time between 0min and 14 min. When Fe is added³⁺，Cu²⁺，Co²⁺Before 8min Fe³⁺，Cu²⁺The fluorescence intensity of the polymer is gradually reduced, and Co²⁺The fluorescence intensity of the polymer is increased, but the fluorescence intensity is not changed within 8min-14min, which shows that the polymer has Fe³⁺，Cu²⁺，Co²⁺The detection of (2) can reach reaction equilibrium and complete rapid detection within 8 min.

5.4 degree of linearity and detection Limit

FIGS. 12(a), 12(c), 12(e) show ionized fluorenylpyridine conjugated polymers in the wavelength range of 350nm-600nm with Fe³⁺，Cu²⁺The concentration increases, the fluorescence emission spectrum gradually decreases, and Co²⁺The increase in concentration gradually increased the fluorescence spectrum, and only Fe was added³⁺The back spectrum is red-shifted, and the other two metal ions do not generate blue shift or red shift. When 1 equivalent of Fe was added to the polymer solution³⁺When the fluorescence intensity is reduced by about 50%, the maximum emission wavelength is red-shifted from 382nm to 417nm, when Fe³⁺When the concentration reaches 20 times of the equivalent weight of the polymer, the fluorescence intensity of the system is reduced to 5 percent of the initial value, the maximum emission wavelength is also from 18nm to 436nm, and the red shift is 54 nm. Adding 1 equivalent of Cu²⁺When the fluorescence intensity of the polymer decreased to 74% of the initial value, 10 equivalents of Cu were added²⁺When the fluorescence intensity of the polymer decreased to 55% of the initial value, the fluorescence spectrum of the subsequent system did not follow Cu²⁺The concentration increases and changes. When 1 equivalent of Co is added²⁺The fluorescence intensity of the polymer increased to 140% of the initial value, and Co was continuously added²⁺Until 20 equivalents, the fluorescence intensity of the polymer rises to 177% of the initial value, and then the fluorescence spectrum of the system hardly follows Co²⁺The concentration increases and changes.

As can be seen from FIGS. 12(b), 12(d) and 12(f), the fluorescence intensity and Fe of the ionized fluorenylpyridine conjugated polymer³ ⁺，Cu²⁺，Co²⁺Shows good linear relation in a certain concentration range, and the linear regression equation of the linear relation is used

And (4) showing. As shown in FIG. 15, the minimum detection limits were calculated to be 0.1. mu. mol L each based on IUPAC and its detection limit definition formula (1)^-1，0.077μmol L^-1And 0.11. mu. mol L^-1. The above results show that the polymer is specific to Fe³⁺，Cu² ⁺，Co²⁺All have good quantitative detection capability.

LOD＝3σ/K (1)

In the formula (I), the compound is shown in the specification,

LOD-detection Limit

K-slope of the plotted Standard Curve

Standard deviation of polymer measurements from blank samples

5.5 anti-interference study

FIG. 13(a), FIG. 13(b), and FIG. 13(c) examine the specific recognition of Fe by the ionized fluorenylpyridine conjugated polymer³⁺，Cu²⁺,Co²⁺The anti-interference capability of the three ions. From the comparative analysis results of the relative fluorescence intensities of the polymer under the conditions that the three metal ions are singly used and the three ions coexist with other ions, the polymer shows that the polymer has Fe in the presence of the interfering metal ions³⁺，Cu²⁺，Co²⁺The selectivity error of the polymer is only between 6.67-15.88% and 1.27-1.63% and 0.28-0.68%, which proves that the polymer is used as a fluorescent probe for Fe³⁺，Cu²⁺，Co²⁺The detection of the three ions has extremely high selectivity and sensitivity and good anti-interference performance, and can be used for detecting Fe³⁺，Cu²⁺，Co²⁺The detection of the three ions has extremely high selectivity and interference resistance.

Sixth, conclusion

For identifying Fe mentioned in the present invention³⁺，Cu²⁺And Co²⁺The fluorescent sensing material ionized fluorenyl pyridine conjugated polymer has the characteristics of simple synthesis method, few steps, low cost and higher yield. The fluorescence sensing material has excellent solubility, good optical activity and large Stokes shift value in different solvents and different pH environments, and is a fluorescence detection reagent suitable for variable media. It is aided by waterThe medium can be effectively used for Fe³⁺，Cu²⁺，Co²⁺The three metal ions are qualitatively and quantitatively detected, so that the selectivity is good, the sensitivity is high, the anti-interference performance is good, and the detection result can be quickly obtained within minutes. The fluorescent sensing material can realize quantitative detection of three metal ions in an extremely low concentration range, and the detection limit is as low as the detection level of nanomole to submicromol.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An ionized fluorenyl pyridine conjugated polymer, characterized by the chemical formula:

2. a preparation method of an ionized fluorenyl pyridine conjugated polymer is characterized by comprising the following steps:

3. The application of an ionized fluorenyl pyridine conjugated polymer is characterized in that: for preparing and identifying Fe³⁺，Cu²⁺And Co²⁺The fluorescent sensing material of (1).