Boric acid group iridium complex probe as well as preparation method and application thereof

Abstract

The invention discloses a boric acid group iridium complex probe as well as a preparation method and application thereof, and relates to the technical field of analytical chemistry. The boric acid group iridium complex probe is formed by complexing # imgabs0 # precursors and PIPB ligands with boric acid groups, targeted recognition of polyphenol substances can be achieved, and quantitative and qualitative detection of the polyphenol substances is achieved through fluorescence spectrophotometry. Besides, the boric acid group iridium complex probe provided by the invention has the characteristic of long service life, can realize targeted noise reduction detection of polyphenol substances through a time-resolved emission spectrum under the condition of high interference intensity, and has extremely high sensitivity; the technical scheme provided by the invention can be applied to accurate detection of polyphenols in fruits.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry, and particularly relates to an iridium complex probe with a borate group, a preparation method thereof, and an application thereof. Background Art

[0002] Polyphenols are an important class of bioactive components in fruits, playing an important role in the color, taste, and aroma of fruits, and also having various physiological functions and beneficial effects on human health. Their structural feature is that there are two or more hydroxyl groups attached to the benzene ring; the detection of polyphenols plays an important role in the quality evaluation, nutritional evaluation, processing technology optimization, variety identification, and origin traceability of fruits. However, due to the complex chemical composition in fruits, it is difficult to accurately detect polyphenols.

[0003] Iridium(III) complexes are widely used in optical detection. Probes prepared based on them have the advantages of non-standard and low cost; iridium(III) complex probes have adjustable luminescence lifetimes by connecting different ligands and can distinguish targets from other fluorophores in complex environments. Therefore, they have potential application value for the detection of polyphenols in fruits; however, in the prior art, the research field of synthesizing and using iridium(III) complex probes to detect polyphenols is still completely blank. Summary of the Invention

[0004] The present invention provides an iridium complex probe with a borate group and a preparation method thereof, aiming to accurately detect polyphenols.

[0005] The iridium complex probe with a borate group provided by the present invention is formed by complexing a precursor and a PIPB ligand with a borate group, and its structure is as follows: The preparation method of the iridium complex probe with a borate group provided by the present invention includes the following steps:

[0006] .

[0007] Step 1, synthesize the PIPB ligand;

[0008] Step 1, synthesize the PIPB ligand;

[0009] Phenanthroline-5,6-dione and ammonium acetate were mixed and dissolved in glacial acetic acid. The concentration of phenanthroline-5,6-dione was 0.25 mmol / mL, and the concentration of ammonium acetate was 5 mmol / mL. p-Formylphenylboronic acid was added dropwise, and the dosage ratio of p-formylphenylboronic acid to glacial acetic acid was 3.5 mmol: 10 mL. The reaction mixture was heated at 130 °C for 3 hours under reflux. The solution turned into a transparent orange-yellow color. After cooling to room temperature, the mixture was diluted with deionized water, and a yellow flocculent precipitate was produced. The yellow flocculent precipitate was collected by vacuum filtration, washed, air-dried, and recrystallized with absolute ethanol to obtain brown PIPB ligand powder. The structure of the PIPB ligand is shown below:

[0010] ;

[0011] Step 2, The precursor and the PIPB ligand synthesized in Step 1 were mixed and dissolved in a chloroform / methanol solvent according to a dosage ratio of 0.1 mmol: 0.3 mmol, and refluxed at 60 °C for 6 h to obtain an orange-red solution. The solvent in the orange-red solution was removed under reduced pressure to obtain a residue. The residue was purified by silica gel column chromatography using DCM / MeOH with a volume ratio of 20:1 as the eluent, and the target band was collected. After evaporating the solvent, an orange-yellow powdery iridium complex probe with a borate group was obtained.

[0012] The iridium complex probe with a borate group provided by the present invention is used to detect polyphenols.

[0013] Optionally, the detection environment of the iridium complex probe with a borate group is an acidic environment.

[0014] Optionally, the pH of the detection environment of the iridium complex probe with a borate group is 4.4 - 5.6.

[0015] Optionally, fluorescence spectrophotometry is used to detect polyphenols with the iridium complex probe with a borate group.

[0016] Optionally, time-resolved emission spectroscopy is used to detect polyphenols with the iridium complex probe with a borate group.

[0017] The present invention has the following beneficial effects:

[0018] The iridium complex probe with a borate group provided by the present invention consists of a functional borate group PIPB ligand and It is formed by precursor complexation, which can achieve targeted recognition of polyphenols; the iridium complex probe with boric acid groups generates fluorescence of a certain wavelength under the excitation of a specific wavelength. After targeted binding with polyphenols, the fluorescence intensity of the sample decreases. Therefore, the content of polyphenols in the sample can be characterized by detecting the fluorescence intensity through fluorescence spectrophotometry, realizing the quantitative and qualitative detection of polyphenols. In addition, the iridium complex probe with boric acid groups provided by the present invention has the characteristic of long lifetime. In the case of high interference intensity, targeted noise reduction detection of polyphenols can be achieved through time-resolved emission spectroscopy, with extremely high sensitivity. The technical solution of the present invention can be applied to accurately detect polyphenols in fruits. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0020] Figure 1 It is the fluorescence emission spectrum diagram of the iridium complex probe with boric acid groups prepared in the embodiment of the present invention under different pH conditions;

[0021] Figure 2 Shows Figure 1 The average intensity of the optimal emission wavelength of the iridium complex probe with boric acid groups in different pH conditions;

[0022] Figure 3 It is the fluorescence emission spectrum diagram of the iridium complex probe with boric acid groups prepared in the embodiment of the present invention under different epicatechin concentration conditions;

[0023] Figure 4 Shows Figure 3 The detection limit of the iridium complex probe with boric acid groups for detecting epicatechin;

[0024] Figure 5 It is the count ratio data diagram of the detection of two groups of samples containing and not containing epicatechin by the iridium complex probe with boric acid groups and coumarin mixture in the TRES noise reduction detection experiment of the present invention;

[0025] Figure 6 Shows Figure 5 In the TRES noise reduction detection experiment shown, at 100 ns, the counts of two groups of samples containing and not containing epicatechin detected by the iridium complex probe with boric acid groups and coumarin mixture. Detailed Embodiments

[0026] In order to make the invention objectives, features, and advantages of the present invention more obvious and understandable, the following will, in conjunction with the accompanying drawings in the embodiments of the present invention, clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0027] The first aspect of the present invention provides a boric acid group iridium complex probe.

[0028] The boric acid group iridium complex probe (abbreviated as Ir-PIPB) provided by the embodiment of the present invention is formed by complexing a precursor and a PIPB ligand with a boric acid group, and its structure is as follows:

[0029] .

[0030] The boric acid group iridium complex probe provided by the embodiment of the present invention can be prepared through the following steps:

[0031] Step 1, synthesize the PIPB ligand;

[0032] Under vigorous stirring, dissolve a mixture of phenanthroline-5,6-dione (0.3 g, 2.5 mmol) and ammonium acetate (3.88 g, 50 mmol) in glacial acetic acid (10 mL). Drop p-formylphenylboronic acid (0.525 g, 3.5 mmol) into this solution. Heat the reaction mixture at 130 °C for 3 hours under reflux. During this period, the solution turns into a transparent orange-yellow color. After cooling to room temperature, dilute the mixture with deionized water (100 mL) to produce a yellow flocculent precipitate; collect the yellow flocculent precipitate by vacuum filtration, wash it thoroughly with water, air-dry it, and then recrystallize it from absolute ethanol to obtain brown PIPB ligand powder (0.53 g, 62% yield).

[0033] The structure of the PIPB ligand is as follows:

[0034] ;

[0035] Step 2, ​The precursor (110 mg, about 0.1 mmol) was mixed and dissolved with the PIPB ligand (105 mg, about 0.3 mmol) obtained in Step 1 in a chloroform / methanol (volume ratio 10 mL / 10 mL) solvent, and refluxed at 60 °C for 6 h to obtain a uniform orange-red solution; the solvent in the orange-red solution was removed under reduced pressure to obtain a residue, and the residue was purified by silica gel column chromatography using a DCM (dichloromethane) / MeOH (methanol) gradient (volume ratio 20:1) as the eluent, and the target band was collected. After evaporating the solvent, an orange-yellow powdery iridium complex probe with a borate group (102 mg, yield 58%) was obtained.

[0036] In the second aspect of the present invention, the iridium complex probe with a borate group prepared in the above examples was used to detect polyphenols, especially polyphenols in fruits.

[0037] Polyphenols in fruits mainly include flavonoids, hydroxybenzoic acids, hydroxycinnamic acids, catechins, proanthocyanidins, etc., which play important roles in the color, taste and aroma of fruits, and also have various physiological functions and beneficial effects on human health.

[0038] In order to explore the performance of the prepared iridium complex probe with a borate group in the detection of polyphenols, the following examples were designed.

[0039] Example 1

[0040] This example explored the optimal pH conditions of the iridium complex probe with a borate group.

[0041] The pH value of 0.01 M PBS (phosphate buffer solution) was adjusted with 0.1 mol / L hydrochloric acid or sodium hydroxide solution to obtain the optimal luminescence pH value of Ir-PIPB at different pH values.

[0042] Specifically, an appropriate amount of 0.1 mol / L hydrochloric acid or sodium hydroxide solution was added to 0.01 M PBS to obtain PBS solutions with pH values of 4.4, 5.0, 5.6, 6.2, 6.8, 7.4, 8.0, and 8.6, respectively; 40 μM Ir-PIPB / DMSO (dimethyl sulfoxide solution of Ir-PIPB, Ir-PIPB concentration is 40 μM) was diluted with PBS solutions with different pH values to DMSO-PBS solutions with a DMSO volume fraction of 2%; the above solutions were excited to emit fluorescence at a wavelength of 405 nm, and the fluorescence intensity was detected using a fluorescence spectrophotometer and scanned in the emission wavelength range of 450 - 750 nm.

[0043] The detection results are as Figure 1 and Figure 2As shown, Ir-PIPB exhibits strong fluorescence in the pH range of 4.4 to 5.6; as the pH increases, the fluorescence intensity of Ir-PIPB decreases, indicating its characteristics as an acidic probe and making it suitable for the detection environment of functional polyphenols in slightly acidic fruit juices such as litchi, rose hips, and prunes.

[0044] Example 2

[0045] To evaluate the detection ability of Ir-PIPB for 1,2-dihydroxybenzene compounds (a type of polyphenols), under the optimal pH conditions of the probe, epicatechin, which is representative in litchi, was selected as the target analyte.

[0046] Under the condition of pH 5, a mixed solution of the probe and the standard substance (epicatechin standard solution) in 2% DMSO-PBS buffer was prepared. The concentration of Ir-PIPB in the mixed solution was set at 40 μM, and the concentrations of the standard substance were set as follows: 0, 1, 2.5, 5, 10, 20, 50, 100, 200, 400, and 800 μM; after culturing at room temperature for 30 minutes, the final solution was excited to fluoresce at a wavelength of 405 nm, and the fluorescence intensity was detected using a fluorescence spectrophotometer, scanning in the emission wavelength range of 450 - 750 nm.

[0047] The detection results are as Figure 3 and Figure 4 shown. Even when the epicatechin content is 1 μM, the fluorescence intensity of Ir-PIPB decreases significantly, indicating that Ir-PIPB provided in the embodiment of the present invention has excellent sensitivity in detecting epicatechin; as the epicatechin content increases, the fluorescence intensity of Ir-PIPB gradually decreases, enabling quantitative analysis of epicatechin.

[0048] Example 3

[0049] In this example, to evaluate the noise reduction detection ability of Ir-PIPB for 1,2-dihydroxybenzene compounds under complex conditions, TRES noise reduction detection was used to detect epicatechin in an interfering environment.

[0050] Specifically, a 40 μM Ir-PIPB probe and a 100 μM interfering probe (coumarin) were configured in a 2% DMSO-PBS solution as the objects for noise reduction detection, and samples with and without 8 μM epicatechin standard were detected respectively; the final solution was excited to fluoresce at a wavelength of 405 nm, and time-resolved emission spectra were scanned at an emission wavelength of 500 - 700 nm with a step of 10 nm.

[0051] The principle of Time-Resolved Emission Spectroscopy (TRES) is as follows: When a substance is excited, the molecules in the excited state will return to the ground state by emitting fluorescence or phosphorescence; different fluorescent substances have different fluorescence lifetimes, that is, the average time that excited-state molecules stay in the excited state; the TRES technique uses a pulsed laser or a flash light source to instantaneously excite the sample, and then measures the fluorescence spectrum emitted by the sample at different time delays; in this way, components with different fluorescence lifetimes can be distinguished, and fluorescence spectrum information changing with time can be obtained.

[0052] The experimental results are as Figure 5 and Figure 6 shown. Two groups of samples with and without epicatechin were compared. It was observed that in the range of 1 - 100 ns, the count ratio increased significantly. After reaching the peak at 100 ns, the count ratio gradually decreased; this indicates that Ir-PIPB has a long lifetime characteristic (generally, the luminescence lifetime of exogenous fluorescent substances is short and will decay within a short time). By applying TRES detection, Ir-PIPB takes advantage of its long luminescence lifetime, which can greatly reduce the interference of exogenous fluorescent substances on the detection and improve the accuracy and specificity of the detection; and at 100 ns, the noise reduction detection effect of Ir-PIPB reaches the optimal.

[0053] In addition, by comparing with the results of detecting the epicatechin content by the ordinary fluorescence spectrophotometry in Example 2, it can be found that: compared with the ordinary fluorescence spectrophotometry, when detecting the same content of epicatechin by TRES, even under the influence of a 2.5-fold coumarin interference concentration, the reduction amplitude of the fluorescence intensity to be detected still reaches 9.3 times, while the fluorescence intensity detected by the ordinary fluorescence spectrophotometry only decreases by about 1.7 times; this shows that by using the long lifetime characteristic of Ir-PIPB, even in the case of high interference intensity, the detection sensitivity for polyphenols can still be further improved.

[0054] In summary, the iridium complex probe with a borate group provided in the embodiment of the present invention is formed by complexing a functional borate group PIPB ligand with a precursor, and can achieve targeted recognition of polyphenols; the iridium complex probe with a borate group generates fluorescence of a certain wavelength under excitation at a specific wavelength. After targeted binding with polyphenols, the fluorescence intensity of the sample decreases. Therefore, the fluorescence intensity can be detected by fluorescence spectrophotometry to characterize the content of polyphenols in the sample, and quantitative and qualitative detection of polyphenols can be realized; in addition, the iridium complex probe with a borate group provided by the present invention has a long lifetime characteristic. In the case of high interference intensity, targeted noise reduction detection of polyphenols can be achieved through time-resolved emission spectroscopy, with extremely high sensitivity.

[0055] The iridium complex probe with boric acid groups provided by the embodiments of the present invention is applicable to the precise detection of polyphenols in fruits, and plays an important role in the quality evaluation, nutritional assessment, processing technology optimization, variety identification, origin traceability, etc. of fruits.

[0056] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An iridium complex probe with a boric acid group, characterized in that Formed by the complexation of a precursor and a PIPB ligand with a borate group, the structure is as follows: Formed by the complexation of a precursor and a PIPB ligand with a borate group, the structure is as follows: 。 2. A method for preparing the iridium complex probe with a boric acid group as claimed in claim 1, characterized in that, It includes the following steps: Step 1: Synthesize the PIPB ligand; Mix phenanthroline-5,6-dione and ammonium acetate and dissolve them in glacial acetic acid. Dropwise add p-formylphenylboronic acid, and heat the reaction mixture at 130 °C for 3 hours under reflux. The solution turns into a transparent orange-yellow color. After cooling to room temperature, dilute the mixture with deionized water to produce a yellow flocculent precipitate. Vacuum filter to collect the yellow flocculent precipitate, wash and air-dry it, and then recrystallize it with absolute ethanol to obtain brown PIPB ligand powder. The structure of the PIPB ligand is shown as follows: ； Step 2, dissolve the precursor and the PIPB ligand obtained in Step 1 in a chloroform / methanol solvent, reflux at 60 °C for 6 h to obtain an orange-red solution; remove the solvent from the orange-red solution under reduced pressure to obtain a residue, purify the residue by silica gel column chromatography to collect the target band, and evaporate the solvent to obtain an orange-yellow powdery iridium complex probe with a borate group.

3. The preparation method of the iridium complex probe with a boric acid group according to claim 2, characterized in that, In the said Step 1, mix phenanthroline-5,6-dione and ammonium acetate and dissolve them in glacial acetic acid. The concentration of phenanthroline-5,6-dione is 0.25 mmol / mL, and the concentration of ammonium acetate is 5 mmol / mL.

4. The preparation method of the iridium complex probe with a boric acid group according to claim 2, characterized in that, In the said Step 1, the dosage ratio of p-formylphenylboronic acid to glacial acetic acid is 3.5 mmol: 10 mL.

5. The preparation method of the iridium complex probe with a boric acid group according to claim 2, characterized in that, In the said step 2, The dosage ratio of the precursor to the PIPB ligand is 0.1 mmol: 0.3 mmol.

6. The preparation method of the iridium complex probe with a boric acid group according to claim 2, wherein In the said Step 2, the eluent for silica gel column chromatography purification is DCM / MeOH with a volume ratio of 20:

1.

7. Application of the iridium complex probe with a boronic acid group as claimed in claim 1 or the iridium complex probe prepared by the preparation method according to any one of claims 2-6 in detecting polyphenols.

8. The application according to claim 7, characterized in that, The detection environment of the iridium complex probe with a boronic acid group is an acidic environment.

9. The application according to claim 7, wherein Fluorescence spectrophotometry is used to detect polyphenols by using the iridium complex probe with a boronic acid group.

10. The application according to claim 7, characterized in that, Time-resolved emission spectroscopy is used to detect polyphenols by using the iridium complex probe with a boronic acid group.

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