Preparation of ionic iridium complex and application of ionic iridium complex in detection of 2, 4, 6-trinitrophenol

Abstract

The invention discloses preparation of an ionic iridium complex and application of the ionic iridium complex to detection of 2, 4, 6-trinitrophenol. The preparation method of the iridium complex comprises the following steps: (1) hydrating iridium trichloride and a 2-(2, 4-difluorophenyl) pyridine main ligand to obtain a first intermediate; (2) preparing four NN type auxiliary ligands through different cyclization reactions; and (3) reacting an NN type auxiliary ligand with the first intermediate obtained in the step (1), and carrying out ion exchange by using ammonium hexafluorophosphate to obtain a target product. The iridium complex of the type is simple to synthesize and mild in condition, has good luminescence performance, has good response recognition performance on 2, 4, 6-trinitrophenol (TNP), and has great application potential.

Description

Technical Field

[0001] The invention belongs to the field of photoelectric functional materials, and specifically relates to the preparation of an ionic iridium complex and its application in the detection of 2,4,6-trinitrophenol (TNP). Background Art

[0002] As we all know, 2,4,6-trinitrophenol (TNP), 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT) and other substances are the main components of most industrial explosives. This type of substance is also called nitro explosives. In recent years, it has been widely used in industry and civilian industries, such as pesticides, drugs, leather, fireworks, dyes and other chemical industries. Among them, 2,4,6-trinitrophenol (TNP), also known as picric acid, is a more powerful explosive substance in its class. During production, use and transportation, it often causes huge pollution to soil and aquatic ecosystems. In addition, TNP can cause gene mutations in mammals and have a certain impact on the ecosystem. This type of substance seriously affects human health, so the development of effective and visual detection methods for this type of substance has attracted widespread attention from scientific researchers. At the same time, in some specific cases, 2,4,6-trinitrophenol is more unstable than 2,4,6-trinitrotoluene, so it is particularly important to develop new high-sensitivity and high-selectivity detection methods. In the past, traditional methods for detecting nitro explosives include chromatography, spectroscopy, and ion transfer, but the above methods also have many disadvantages, such as high instrument prices, inconvenient portability, and complex operations.

[0003] Fluorescence detection is not only simple and convenient, but also has the advantages of high sensitivity and selectivity, high spatiotemporal resolution, low detection limit, simplicity and speed. It is considered to be a new and fast detection method. Compared with traditional organic light-emitting probes, phosphorescent probes of metal iridium complexes not only have the advantages of high recognition accuracy and simple operation, but also have the advantages of large Stokes shift, long luminescence lifetime, adjustable luminescence color, and high quantum yield. The background interference fluorescence lifetime generated by cell autofluorescence and scattered light is generally less than 100ns, while the phosphorescence lifetime emitted by cyclometallated iridium complexes is generally in the microsecond level. Therefore, the spectrum obtained after a delay of 100ns can eliminate background interference and improve the accuracy of ion detection. Long-wavelength phosphorescent probes can also be obtained by adjusting the ligand structure, which is conducive to tissue penetration and reduces the damage of phototoxicity to cells. This is another major advantage of cycloiridium phosphorescent probes in biological imaging. In 2018, Zhu Dongxia et al. successfully prepared a cyclometallated iridium complex phosphorescent probe with good response to TNP (Chemical Communications, 2018, 54, 1730-1733), but the detection line of this type of probe is not ideal and the response is poor. So far, there are few reports on materials that can achieve full-color regulation of visible light, so it is of great significance to develop a new type of cyclometallated iridium complex phosphorescent probe with high efficiency and full-color display for detecting TNP. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention aims to:

[0005] One of the purposes of the present invention is to provide an ionic cyclometalated iridium complex which is simple to synthesize, has high luminescence brightness, good luminescence stability and full-color display.

[0006] The second object of the present invention is to provide a method for preparing the above-mentioned ionic cyclometalated iridium complex.

[0007] The third object of the present invention is to provide the application of the above iridium complex for TNP recognition.

[0008] A technical solution to achieve one of the purposes of the present invention is: an ionic cyclometalated iridium complex, the general structural formula of which is shown below:

[0009]

[0010] The technical solution for achieving the second object of the present invention is: the preparation method of the above-mentioned cyclometalated iridium complex comprises the following steps:

[0011] ① The first intermediate is obtained by reacting the cyclometallated ligand 2-(2,4-difluorophenyl)pyridine with hydrated iridium trichloride;

[0012] ②Four N^N-type auxiliary ligands were prepared under different cyclization conditions: 2-(pyridin-2-yl)-2H-indazole, 2-(pyridin-2-yl)-1H-benzo[d]imidazole, 2-(pyridin-2-yl)imidazo[1,2-a]pyridine and 1-(pyridin-2-yl)-1H-indazole;

[0013] ③ The N^N type auxiliary ligand reacts with the first intermediate iridium dichloro bridge precursor obtained in step 1, and then ion exchange is performed to obtain the target product.

[0014] In the above step ①, the molar ratio of the cyclometallated ligand 2-(2,4-difluorophenyl)pyridine to hydrated iridium trichloride is 2:1 to 3:1.

[0015] The reaction in step ① is carried out in the presence of a mixed solvent; the mixed solvent is preferably 2-ethoxyethanol and water in a volume ratio of 1:1 to 3:1.

[0016] The reaction temperature of step ① is 100-130°C, preferably 120°C.

[0017] The specific synthesis method of the four N^N type auxiliary ligands in step ② above is as follows:

[0018] 2-(Pyridin-2-yl)-2H-indazole is prepared by condensing and dehydrating 2-nitrobenzaldehyde and 2-aminopyridine in an isopropanol reaction system, and then using a cyclization reagent tri-n-butylphosphine at a reaction temperature of 110° C., and further subjected to column chromatography to obtain the auxiliary ligand.

[0019] 2-(Pyridin-2-yl)-1H-benzo[d]imidazole is prepared by reacting 2-pyridinecarboxylic acid and 1,2-phenylenediamine in the presence of a polyphosphoric acid dehydration cyclization reagent at a reaction temperature of 110°C, and further subjected to column chromatography to obtain the auxiliary ligand mentioned above.

[0020] 2-(Pyridin-2-yl)imidazo[1,2-a]pyridine is a mixed system of 1-(2-hydroxyphenyl)ethanone, 2-aminopyridine and elemental iodine, the reaction temperature is 110°C, and the auxiliary ligand is further separated by column chromatography.

[0021] 1-(Pyridin-2-yl)-1H-indazole is prepared from 2-chloropyridine and 1H-indazole as reaction substrates, under the action of alkaline reagent Zn(OAc)2, with catalyst Pd2(dba)3·CHCl3 (5 mol%) and ligand Xantphos (10 mol%) in N2 atmosphere at a reaction temperature of 110°C, and further separated by column chromatography to obtain the above-mentioned auxiliary ligand.

[0022] In the above step ③, the molar ratio of the first intermediate iridium dichloro bridge precursor to the N^N type auxiliary ligand is 1:2.4.

[0023] The reaction in step ③ is carried out in a mixed solvent system; the mixed organic solvent system is dichloromethane and methanol, with a volume ratio of 1:1.

[0024] The ion exchange reaction in step ③ is carried out in the presence of an ion exchange reagent; the molar ratio of the first intermediate to the ion exchange reagent is 1:5 to 1:10. The ion exchange reagent is potassium hexafluorophosphate or ammonium hexafluorophosphate, preferably ammonium hexafluorophosphate.

[0025] The reaction temperature of the above step ③ is 40°C.

[0026] The technical solution for achieving the third object of the present invention is: application of the above-mentioned ionic iridium complex for TNP recognition.

[0027] The application of the iridium complex for TNP recognition is mainly to dissolve the above series of cyclometallated iridium complex phosphorescent probes in an acetonitrile solution system, showing strong fluorescence. However, after the solution of the material reacts with TNP (diluted with acetonitrile), its fluorescence intensity is significantly reduced, resulting in obvious fluorescence annihilation. Using the ionic iridium complex as the recognition group of TNP, it has a rapid and sensitive response to TNP and can perform fluorescence detection on the level of exogenous TNP.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] ① The series of ionic iridium complexes of the present invention are used as fluorescent recognition solution-type TNP molecular probes, and have simple and stable molecular structures and simple synthesis methods.

[0030] ② The probe has high luminescence efficiency. After contacting with TNP solution, the fluorescence is annihilated instantly. Moreover, the minimum detection limit for TNP is at the μM level, with high sensitivity.

[0031] ③This series of ionic iridium complexes are visualized and therefore have great application potential in the detection of TNP. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. The following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also obtain other related drawings based on these drawings without creative work.

[0033] Figure 1 The molecular structure of the ionic iridium complex Ir1-Ir4

[0034] Figure 2The synthetic reaction route of ionic iridium complexes Ir1-Ir4

[0035] Figure 3 The fluorescence response spectrum of the ionic iridium complex Ir2 to TNP, [Ir] = 10 μM

[0036] Figure 4 The redox electrochemical diagram of ionic iridium complex Ir1-Ir4

[0037] Figure 5 This is the UV-visible absorption spectrum of the ionic iridium complex Ir1-Ir4

[0038] Figure 6 The fluorescence emission diagram of ionic iridium complex Ir1-Ir4

[0039] Figure 7 Comparison of Ir test paper under UV light and test paper after TNP action DETAILED DESCRIPTION

[0040] The following examples will further illustrate the present invention, but are not intended to limit the present invention. The nuclear magnetic resonance data were measured by a Bruker 400 nuclear magnetic resonance instrument.

[0041] Example 1

[0042] The structural formula of the ionic iridium complex Ir1 of this embodiment is as follows:

[0043]

[0044] The preparation method of the ionic iridium complex comprises the following steps:

[0045] ①Synthesis of the first intermediate dimer (L)2Ir(μ-Cl)2Ir(L)2 between iridium and chlorine bridges

[0046] 0.40 g of 2-(2,4-difluorophenyl)pyridine (2.09 mmol) and 0.34 g of IrCl3·3H2O (0.95 mmol) were dissolved in a mixture of 8 mL of ethylene glycol monoethyl ether and 4 mL of water, and the mixture was evacuated and ventilated for 3 times, and then heated to 120°C under nitrogen protection for 10 h. After the reaction, 10 mL of water was added, and the solid was collected by filtration. The solid was further vacuum dried to obtain 0.37 g of the first intermediate dimer (L)2Ir(μ-Cl)2Ir(L)2 containing an iridium-chloride bridge bond, with a yield of 64.3%.

[0047] ②Synthesis of auxiliary ligand 2-(pyridin-2-yl)-2H-indazole

[0048] 500 mg of 2-nitrobenzaldehyde was dissolved in 3.0 mL of isopropanol, and then 311 mg of 2-aminopyridine was added in batches. After the addition was completed, the reaction solution was heated to 80°C and stirred for 4 hours. The reaction system was cooled to room temperature, and 1.96 g of tri-n-butylphosphine was added in batches, and then the reaction system was heated to 80°C and stirred for 16 hours. The system was cooled to room temperature, 25 mL of ethyl acetate was added, and the organic phase was washed with 15 mL of ammonium chloride and 15 mL of saturated brine in turn, dried over MgSO4, filtered and concentrated in vacuo. The residue was purified by silica gel chromatography (0-25% ethyl acetate / heptane) to obtain 0.59 g of the desired product 2-(pyridin-2-yl)-2H-indazole, with a yield of 92.1%. ③ Synthesis of ionic iridium complex Ir1

[0049] 100 mg of dimer (L)2Ir(μ-Cl)2Ir(L)2 and 40 mg of 2-(pyridin-2-yl)-2H-indazole were dissolved in a mixed solvent of methanol and dichloromethane, heated to 40°C and refluxed for 5 h under nitrogen protection, cooled to room temperature, and ammonium hexafluorophosphate was added and stirred for 2 h.

[0050] After the reaction, the reaction system was cooled to room temperature, 20 mL of dichloromethane was added, the organic phase was washed with saturated brine, dried over MgSO4, filtered and concentrated in vacuo, and the residue was separated by column chromatography (eluent: dichloromethane: methanol = 100:0-50:1) to obtain 80 mg of the target product Ir1 with a yield of 64.1%. 1 H NMR(400MHz, CDCl3)δ9.39(s,1H),8.60(d,J=8.5Hz,1H),8.33-8.26(m,3H),7.84-7.75(m,4H),7.62(d,J=5.8Hz,1H),7.55-7.53(m,1H), 7.48-7.45(m,1H),7.19-7.09(m,3H),7.05-7.01(m,1H),6.67-6.56(m,2H),6.31(d,J=8.7Hz,1H),5.80-5.78(m,1H),5.71-5.68(m,1H).

[0051] Example 2

[0052] The structural formula of the ionic iridium complex Ir2 of the present embodiment is as follows:

[0053]

[0054] The preparation method of the ionic iridium complex comprises the following steps:

[0055] ①Synthesis of 2-(pyridin-2-yl)-1H-benzo[d]imidazole

[0056] 1.23 g of 2-picolinic acid, 1.08 g of 1,2-phenylenediamine and polyphosphoric acid (PPA, 10 g) were heated to 150 °C for 2 h. After cooling, the solution was poured into cold water and the pH was adjusted to 7-8 with NaOH. The resulting grey / pink precipitate was filtered, washed with water and dried in air. The crude product was purified on a chromatographic column (silica gel) using a mixture of ethyl acetate and n-hexane (1:1) as the eluent to obtain 1.31 g of the desired product with a yield of 64.5%.

[0057] ②Synthesis of ionic iridium complex Ir2

[0058] 100 mg of dimer (L)2Ir(μ-Cl)2Ir(L)2 and 30 mg of 2-(pyridin-2-yl)-1H-benzo[d]imidazole were dissolved in a mixed solvent of methanol and dichloromethane, heated to 40°C and refluxed for 5 h under nitrogen protection, cooled to room temperature, and ammonium hexafluorophosphate was added and stirred for 2 h.

[0059] After the reaction, the reaction system was cooled to room temperature, 20 mL of dichloromethane was added, the organic phase was washed with saturated brine, dried over MgSO4, filtered and concentrated in vacuo, and the residue was separated by column chromatography (eluent: dichloromethane: methanol = 100:0-50:1) to obtain 72 mg of the target product Ir2 with a yield of 58.4%. 1 H NMR (400MHz, CDCl3) δ8.64(d,J=7.9Hz,1H),8.32-8.24(m,2H),8.14(t,J=7.6Hz,1H),7.90(d,J=5.2Hz,1H),7.80-7.64(m,4H),7.51(d,J=5.7Hz, 1H),7.47-7.44(m,1H),7.29(t,J=7.7Hz,1H),7.08-6.98(m,3H),6.65-6 .54(m,2H),6.35(d,J=8.3Hz,1H),5.84-5.81(m,1H),5.76-5.74(m,1H).

[0060] Example 3

[0061] The structural formula of the ionic complex Ir3 of this embodiment is as follows:

[0062]

[0063] The preparation method of the ionic iridium complex comprises the following steps:

[0064] ①Synthesis of 2-(pyridin-2-yl)imidazo[1,2-a]pyridine

[0065] A round-bottom flask was charged with 0.75 g of 1-(2-hydroxyphenyl)ethanone, 1.19 g of 2-aminopyridine (1) and 1.68 g of iodine. After the reaction mixture was stirred at 110° C. for 4 hours, the mixture was cooled to 70° C. and stirred overnight. The residue was diluted with 5 mL of distilled water and an excess of aqueous sodium hydroxide solution (45%) was added. The reaction mixture was stirred at 100° C. for 1 h. After cooling to room temperature, the reaction mixture was diluted with 25 mL of CH2Cl2. A 10% aqueous HCl solution was added to the water-organic mixture until a neutral pH was obtained. The mixture was then extracted with CH2Cl2. The organic layer was washed with water, dried over Na2SO4, and concentrated under reduced pressure. The solid was separated by column chromatography (silicon dioxide, dichloromethane / hexane=1:2→dichloromethane / hexane=3:1). After crystallization from ethanol-water, 0.69 g of the desired product was obtained with a yield of 64.5%.

[0066] ②Synthesis of ionic iridium complex Ir3

[0067] 100 mg of dimer (L)2Ir(μ-Cl)2Ir(L) and 30 mg of 2-(pyridin-2-yl)imidazo[1,2-a]pyridine were dissolved in a mixed solvent of methanol and dichloromethane, heated to 40°C and refluxed for 5 h under nitrogen protection, cooled to room temperature, and ammonium hexafluorophosphate was added and stirred for 2 h.

[0068] After the reaction, the reaction system was cooled to room temperature, 20 mL of dichloromethane was added, the organic phase was washed with saturated brine, dried over MgSO4, filtered and concentrated in vacuo, and the residue was separated by column chromatography (eluent: dichloromethane: methanol = 100:0-50:1) to obtain 80 mg of the target product Ir3 with a yield of 65.1%. 1 H NMR (400MHz, CDCl3) δ8.88(s,1H),8.50(d,J=6.8Hz,1H),8.36(d,J=8.1Hz,1H),8.31-8 .26(m,2H),8.03(t,J=7.8Hz,1H),7.82-7.77(m,3H),7.65(d,J=5.3Hz,1H),7.53(d,J= 5.8Hz,1H),7.33-7.30(m,1H),7.14-7.11(m,1H),7.05(t,J=6.6Hz,2H),6.98(t,J=6.8 Hz,1H),6.61-6.55(m,2H),6.20(d,J=9.2Hz,1H),5.82-5.80(m,1H),5.73-5.70(m,1H).

[0069] Example 4

[0070] The structural formula of the ionic iridium complex Ir4 of this embodiment is as follows:

[0071]

[0072] The preparation method of the ionic iridium complex comprises the following steps:

[0073] ①Synthesis of 1-(pyridin-2-yl)-1H-indazole

[0074] Under N2 atmosphere, 20mL of degassed 1,4-dioxane was added to a round-bottom flask. 1.01g of 2-chloropyridine, 1.04g of 1H-indazole and 0.97g of Zn(OAc)2 were added to the round-bottom flask, and nitrogen was passed through the mixture for 10 minutes, and then catalysts Pd2(dba)3·CHCl3 (5mol%) and Xantphos (10mol%) were added. The mixture was stirred at 100°C for 16 hours. After the reaction was completed, the material was cooled to room temperature, diluted with 10mL of CH2Cl2, and filtered through a silica gel plug. The filtrate was concentrated in vacuo and then purified by column chromatography to obtain 1.32g of the desired product in a yield of 76.8%.

[0075] ②Synthesis of ionic iridium complex Ir4

[0076] 100 mg of dimer (L)2Ir(μ-Cl)2Ir(L) and 30 mg of 2-(pyridin-2-yl)imidazo[1,2-a]pyridine were dissolved in a mixed solvent of methanol and dichloromethane, heated to 40°C and refluxed for 5 h under nitrogen protection, cooled to room temperature, and ammonium hexafluorophosphate was added and stirred for 2 h.

[0077] After the reaction, the reaction system was cooled to room temperature, 20 mL of dichloromethane was added, the organic phase was washed with saturated brine, dried over MgSO4, filtered and concentrated in vacuo, and the residue was separated by column chromatography (eluent: dichloromethane: methanol = 100:0-50:1) to obtain 85 mg of the target product Ir4 with a yield of 65.9%. 1 H NMR (400MHz, CDCl3) δ8.57(d,J=8.6Hz,1H),8.41(d,J=8.7Hz,1H),8.35-8.30(m,3H),7.84-7.79(m,6H),7.75(d,J=5.8Hz,1H),7.71(d ,J=5.8Hz,1H),7.50-7.46(m,1H),7.35-7.31(m,1H),7.17-7.13(m,1H),7.10-7.07(m,1H),6.59(t,J=10.3Hz,2H),5.75-5.69(m,2H).

[0078] Example 5

[0079] Experiment on the exogenous response of Ir2 to TNP

[0080] The complex used below is the compound prepared in Example 2.

[0081] Use HPLC grade acetonitrile as solvent to prepare a 10μM complex solution, add different concentrations of TNP solution, and test the fluorescence intensity directly after adding. The maximum emission wavelength of the complex is 510nm under 406nm excitation wavelength. The experimental results are Figure 2 As can be seen from the figure, the fluorescence intensity of the complex, which originally had strong fluorescence, was greatly weakened after adding a small amount of TNP solution, indicating that the complex can show a very sensitive fluorescence response to solution-type TNP and can be used as a fluorescent probe of TNP.

Claims

1. An ionic metal iridium complex, characterized in that The general structure is as follows: In the formula, R each independently represents a carbon atom or a nitrogen atom, and the N^N type auxiliary ligands are 2-(pyridin-2-yl)-2H-indazole, 2-(pyridin-2-yl)-1H-benzo[d]imidazole, 2-(pyridin-2-yl)imidazo[1,2-a]pyridine and 1-(pyridin-2-yl)-1H-indazole.

2. The method for preparing an ionic iridium complex according to claim 1, wherein: (1) In the first step, the commercial cyclometallated ligand 2-(2,4-difluorophenyl)pyridine is reacted with hydrated iridium trichloride to obtain the first intermediate; (2) In the second step, four N^N type auxiliary ligands are prepared using different cyclization conditions; (3) In the third step, the N^N type auxiliary ligand is reacted with the intermediate iridium dichloro bridge precursor obtained in step 1, and then ion exchange is carried out with ammonium hexafluorophosphate to obtain the target product.

3. The method for preparing an ionic iridium complex according to claim 2, characterized in that: The first step of the chlorine bridge preparation reaction is that the molar ratio of 2-(2,4-difluorophenyl)pyridine to hydrated iridium trichloride is 2:1; the molar ratio of the N^N type auxiliary ligand in the third step to the intermediate of the first step is 2:1 to 3:1, and then ion exchange is carried out with 5 equivalents of ammonium hexafluorophosphate.

4. The use of the ionic iridium complex according to claim 1, characterized in that: Used for the detection of 2,4,6-trinitrophenol.

5. The use of the ionic iridium complex according to claim 4, characterized in that: The method for detecting 2,4,6-trinitrophenol comprises the following steps: Step 1, adding a cyclometalated iridium complex to an HPLC grade acetonitrile solvent to form a 10 μm cyclometalated iridium complex solution; Step 2, dissolving TNP in acetonitrile solvent to form solutions of different concentrations; TNP solutions of different concentrations were added to the cyclometallated iridium complex solution obtained in step (1), and the fluorescence spectrum was detected within 5 minutes to obtain a standard curve of TNP concentration and fluorescence intensity.

6. The use of the ionic iridium complex according to claim 5, characterized in that: Combining four different N^N type auxiliary ligands to form ionic metal iridium complexes can effectively transfer electrons with TNP and realize the detection of TNP.

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