CN109705147B

CN109705147B - Environment-sensitive dye and preparation method and application thereof

Info

Publication number: CN109705147B
Application number: CN201811586712.0A
Authority: CN
Inventors: 徐云祥; 曹健
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2018-12-25
Filing date: 2018-12-25
Publication date: 2020-04-03
Anticipated expiration: 2038-12-25
Also published as: CN109705147A

Abstract

The invention relates to the technical field of fluorescent materials, in particular to an environment-sensitive fluorescent material. The invention provides an environment-sensitive dye, which has a structural formula shown as a formula I, wherein in the formula I, A₁And A₂Is a substance containing a group having electron donating properties; r₁、R₂、R₃And R₄Selected from the following groups: alkyl, substituted benzene ring or substituted thiophene ring. The environment-sensitive dye molecule obtained by the invention has the advantage of sensitivity to microenvironment in a solution state and an aggregation state, and has higher fluorescence quantum yield in different solvents when being used as a polar sensitive dye in the solution state.

Description

Environment-sensitive dye and preparation method and application thereof

Technical Field

The invention relates to the technical field of fluorescent materials, in particular to an environment-sensitive fluorescent material.

Background

Environmentally sensitive dyes are capable of changing the color or intensity of emitted light in response to changes in the environment, such as polarity, pH and viscosity (also known as lyotropic dyes). This property makes them widely used in the fields of fluorescent probes, chemical sensors, detection of changes in microenvironment, biological imaging, molecular switching and phase separation visualization, etc.

Environmentally sensitive dye molecules are achieved primarily by forming intramolecular charge transfer states. When the dye is photoexcited, charge is transferred from the donor to the acceptor group, resulting in an excited state with a high dipole moment. Then, the excited state is relaxed by the interaction with the solvent dipole, and thus the fluorescence peak thereof is red-shifted in the polar solvent, and the corresponding color is shifted toward the red light. In general, the requirements for environmentally sensitive dyes are: (1) have a large stokes shift to avoid self-absorption effects; (2) the fluorescence color of the fluorescent material changes dramatically with the change of the environment; (3) has high photoluminescence quantum yield under different environments. Molecules that typically have distorted charge transfer states and planar charge transfer states are often used for environmentally sensitive dyes. Molecules with distorted charge transfer states have large stokes shifts and drastic color changes, but the quantum yields in different environments vary greatly. For example, in polar solvents, the quantum yield is greatly attenuated and even the fluorescence disappears. In contrast, molecules with planar charge transfer states have higher quantum yields in different environments, but their color changes are not sufficiently pronounced.

In addition, environmentally sensitive dye molecules typically have conjugated aromatic rings. The molecules can generate strong intermolecular pi-pi stacking interaction in an aggregation state, so that the fluorescence of the molecules is quenched, and the molecules cannot be applied to the fields of solid environment detection, phase structure visualization and the like. Therefore, the fluorescent dye molecule which has solution and aggregation state environment sensitivity is developed and has wide application prospect.

Disclosure of Invention

In view of the above-mentioned drawbacks, the technical problem to be solved by the present invention is to provide a novel environmentally sensitive dye molecule which has the advantage of having sensitivity to micro-environment in both solution state and aggregation state, and which, in addition, when in solution state, when used as a polar sensitive dye, has higher fluorescence quantum yield in different solvents.

The technical scheme of the invention is as follows:

the first technical problem to be solved by the invention is to provide an environment-sensitive dye (solvent-induced color-changing dye), which has a structural formula shown as a formula I:

wherein A is₁And A₂Is a substance containing a group having electron donating properties; r₁、R₂、R₃And R₄Independently of one another, identical or different, are selected from the following groups: alkyl, substituted benzene ring or substituted thiophene ring.

Further, in the formula I, A₁And A₂Is an aromatic ring or a substituted aromatic ring; further, the aromatic ring is selenophene, benzene, thiophene, furan, bithiophene, benzothiophene, benzodithiophene, naphthalene, or anthracene; the substituent on the substituted aromatic ring is-F, -Cl, -Br, -I, -R, -OR, -SR, -NH₂At least one of-NHR or-NRR ', wherein R and R' are selected from alkyl straight chain or alkyl branched chain with the carbon number of 1-20.

Further, A₁Is 2-bromoselenophene, A₂Is a benzene ring.

Further, R₁、R₂、R₃And R₄A p-hexylbenzene synthetic compound or a p-methylbenzene synthetic compound is selected.

The second technical problem to be solved by the present invention is to provide a preparation method of the above-mentioned environmentally sensitive dye, the preparation method comprises: dissolving a compound shown as a formula II in an organic solvent, adding bromosuccinimide or bromine, and reacting at normal temperature to obtain a brominated product; the brominated product is directly dissolved in an organic solvent without purification; then adding an oxidant to carry out oxidation reaction to obtain the environment-sensitive dye shown in the formula I.

Further, the structural formula shown in formula II is selected from one of the following compounds:

further, the oxidant is hydrogen peroxide, m-chloroperoxybenzoic acid, potassium peroxydisulfate compound salt or oxygen.

Further, the organic solvent is at least one of chloroform, dichloromethane, acetone or tetrahydrofuran.

Further, the method comprises the following steps:

(1) dissolving a compound shown in a formula II and bromosuccinimide or bromine in an organic solvent, reacting for 1-5 h (preferably 2h) in a dark place, and adding water to quench the reaction after the reaction is finished; extracting and washing the product, and drying the organic phase to obtain a crude product, and directly carrying out the next step;

(2) directly dissolving the crude product obtained in the step (1) in an organic solvent, adding an oxidant, reacting at normal temperature for 0.5-4 h (preferably 3h), and adding water to quench the reaction after the reaction is finished; extracting, washing, drying the organic phase, and purifying by using a chromatographic column to obtain a solid, namely the environment-sensitive dye.

The third technical problem to be solved by the present invention is to provide the application of the above-mentioned environmentally sensitive dye:

the environment sensitive dye is used for environment polarity detection and biological imaging; or:

the environment-sensitive dye is used in the field of polymer phase separation visual detection; or:

the environmentally sensitive dye is used as a pH responsive smart material.

The dye molecule provided by the invention shows blue light in nonpolar n-hexane, the fluorescence of the dye molecule gradually generates red shift along with the continuous increase of the polarity of a solvent, and the dye molecule has a lyotropic discoloration effect and can be applied to environment polarity detection and biological imaging. In addition, the molecule still has fluorescence in an aggregation state, and the fluorescence is red-shifted along with the increase of the polarity of the polymer, so that the molecule can be used in the field of polymer phase separation visual detection. In addition, because of the carboxyl group in the molecule, the compound can be used as a pH response intelligent material.

The invention has the beneficial effects that:

the invention synthesizes a series of fluorescent dye molecules sensitive to the environment, and because the carbonyl group and the carboxyl group of the fluorescent dye molecules have strong intramolecular hydrogen bonds, the molecules keep plane conformation and have higher fluorescence quantum yield in various solvents; for example, the quantum yield in acetonitrile, a strongly polar solvent, was 10% and the quantum yield in chloroform was 62%. In addition, when the molecule is excited, the charge transfer state generated by the molecule leads to the increase of carbonyl alkalinity, intramolecular proton transfer can occur, and a more stable excited state is generated; in the process, the shift of the negative charge position causes the transition dipole moment of the molecule to change greatly; therefore, the fluorescence color in the solvent is changed very sharply with the change of polarity. On the other hand, due to the side chain (R) of the molecule₁、R₂、R₃And R₄) It acts to isolate the chromophore (conjugated backbone) so that it still fluoresces in the aggregate state, and this fluorescence is sensitive to the polarity of the polymer.

In summary, the environmentally sensitive fluorescent dye molecules obtained by the present invention have the following advantages: (1) the color of the liquid crystal material is changed in different polar solvents, and the color is from blue to orange, and basically covers a visible light area; (2) the fluorescence quantum yield is over 10% in different solvents, and particularly in chloroform, the quantum yield reaches 62%; (3) in the aggregation state, the molecules still have fluorescence emission, and the change of the fluorescence emission is changed along with the polarity of the polymer, so that the polymer phase separation visualization research can be carried out.

Description of the drawings:

FIG. 1 shows fluorescence emission spectra of ISOAA-H fluorescent molecules of example 1 of the present invention in different polar solvents.

FIG. 2 is a photograph of the fluorescence of ISOAA-H fluorescent molecules of example 1 of the present invention in various polar solvents (photographed under a 365nm UV lamp).

FIG. 3 shows the fluorescence emission spectra of 1% ISOAA-H fluorescent molecules dispersed in different polymer matrices and the fluorescence emission spectra of pure ISOAA-H powder (excitation wavelength 365 nm).

FIG. 4 is a diagram of a phase separation scheme with 1% of ISOAA-H fluorescent molecules dispersed in different polymer blends.

FIG. 5 shows fluorescence emission spectra of ISOAA-M fluorescent molecules of example 3 of the present invention in different polar solvents.

Detailed Description

The invention provides a series of fluorescent dye molecules sensitive to environment, the structural formula of which is shown as formula I, wherein the formula I has a six-membered ring structure which is composed of carboxyl and carbonyl and has intramolecular hydrogen bonds; a. the₁And A₂Is a structure having electron donating properties; r₁、R₂、R₃And R₄Is a structure with certain steric hindrance; therefore, the molecule of the structural formula can be used as an environment-sensitive dye molecule, has the advantage of sensitivity to a microenvironment in a solution state and an aggregation state, and has higher fluorescence quantum yield in different solvents when used as a polar sensitive dye in a solution state. This is mainly due to the following reasons: (1) due to the strong intramolecular hydrogen bond between the carbonyl group and the carboxyl group in the molecule, the molecule keeps plane conjugated (chromophore) conformation, so the molecule has fluorescence emission; the molecule has a planar conformation and therefore is useful in a variety of solventsThe yield of fluorescence quantum is high; (2) when the molecule is excited, the charge will be transferred from electron donor moiety A₁And A₂Transferring to electron-withdrawing carbonyl and carboxyl groups to form a charge transfer state; the charge transfer state interacts with the dipole of the solvent in the solvents with different polarities, so that the luminescent red shift of the charge transfer state is caused, and different colors are generated; the compound shown in the formula I can generate intramolecular proton transfer due to the connection of carboxyl and carbonyl through intramolecular hydrogen bonds, so that a more stable excited state is generated; in the process, the transition dipole moment (the difference between the excited state dipole moment and the ground state dipole moment) of the molecule is increased, so that drastic color change in different solvents is caused (the larger the transition dipole moment is, the more sensitive the molecule is to the polarity of the solvent, and the more obvious the color change is); (3) for conjugated molecules, fluorescence quenching is generally caused by strong pi-pi accumulation in an aggregation state, the molecules in the invention can cause chromophores to be in an isolated state due to the existence of steric side chains, the pi-pi accumulation is inhibited, the molecules mainly take a single molecular state, and fluorescence emission can also be generated in the aggregation state; and a single molecule will generate a dipole-dipole interaction with the polymer matrix, exhibiting responsiveness to the polarity of the polymer matrix.

The synthetic reaction formula of the preparation method of the environment-sensitive dye is as follows:

the following examples are intended to further illustrate the present invention, but are not to be construed as limiting the scope of the invention, and all techniques that can be practiced by one skilled in the art based on the teachings herein are within the scope of the invention.

EXAMPLE 1 Synthesis of ISOAA-H

The synthetic route of the environment sensitive fluorescent molecule ISOAA-H is shown as formula III:

in the reaction formula, NBS is N-bromoSuccinimide, chloroform, oxone potassium hydrogen peroxysulphate complex salt (K)₂SO₄·KHSO₄·KHSO₅)，NaHCO₃Sodium bicarbonate, DCM dichloromethane, acetone, H₂O is water, R.T represents normal temperature;

the specific synthesis steps are as follows:

(1) IDS (180mg, 0.200mmol, 1eq) and NBS (78.0mg, 0.440mmol, 2.2eq) are dissolved in 5.00mL of chloroform and reacted for 2h in a dark place, and after the reaction is finished, water is added to quench the reaction; extracting the product with dichloromethane, washing with water, adding anhydrous sodium sulfate into the organic phase, and drying to obtain a crude product which is directly subjected to the next step;

(2) a mixed solution of 8.00mL of acetone, 10.0mL of dichloromethane and 11.0mL of water was prepared, the crude product from the previous step was dissolved in the mixed solution, and sodium bicarbonate (380mg) and oxone (K) were added₂SO₄·KHSO₄·KHSO₅) (701mg, 1.14mmol, 6eq) and reacting at normal temperature for 3h, and adding water to quench the reaction after the reaction is finished; washing with water and dichloromethane for three times, drying the organic phase with anhydrous sodium sulfate, spinning, and purifying with 200-mesh silica gel 300-mesh column (the developing agent is PE: DCM ═ 1:1, and the product shows bright yellow fluorescence under 365 ultraviolet lamp); 41.0mg of a yellow solid was obtained in 17.0% yield.

¹H NMR(400MHz,CDCl₃)δ14.62(s,1H),7.85(s,1H),7.25(s,1H),7.23(s,1H),7.09(dd,J＝22.7,3.6Hz,16H),6.35(s,1H),2.57(dd,J＝15.9,8.9Hz,8H),1.59(dd,J＝14.5,6.7Hz,8H),1.37–1.23(m,24H),0.87(dd,J＝6.7,2.4Hz,12H).¹³C NMR(100MHz,CDCl₃)δ195.24,165.12,161.93,159.86,155.75,153.83,150.12,143.42,142.76,142.59,141.16,139.81,133.95,133.04,129.66,128.94,128.86,128.65,127.73,123.45,122.44,117.32,64.70,61.59,35.68,35.62,31.84,31.44,31.40,29.85,29.23,22.73,14.24.HRMS(m/z):[M]⁺,calcd for C₆₄H₇₃BrO₃Se,1049.3981；found:1049.3964.

The fluorescence emission spectra of the product ISOAA-H of this example in different solvents and in photographs under UV light are shown in FIGS. 1 and 2, respectively (concentration 10)^-5M, excitation wavelength365 nm); as can be seen from the two figures, the wavelength of the fluorescence emission peak of ISOAA-H continuously red-shifts with the increase of the polarity of the solvent, and the phenomenon of very obvious lyotropic discoloration is shown; the corresponding color changed gradually from blue (n-hexane) to orange (acetone and acetonitrile) essentially covering the visible region. The corresponding fluorescence quantum yields (shown in fig. 1) were all greater than 10%, reaching a maximum of 62% in chloroform; the ISOAA-H is a dye molecule which is very sensitive to environmental polarity, and can keep higher quantum yield in various solvents.

Example 2

This example is a preparation of the molecule ISOAA-H from example 1 dispersed in different polymers and blends, with the following specific steps:

(1) respectively dissolving Polystyrene (PS), polymethyl methacrylate (PMMA), polyisoprene (PIP), styrene-butadiene-styrene terpolymer (SBS) and polyethylene glycol (PEG) in good solvent (PS, PMMA, SBS and PI are dissolved in toluene, and PEG is dissolved in chloroform) to prepare 50mg/ml solution; ISOAA-H is dissolved in toluene to prepare 10mg/ml solution;

(2) adding 1% ISOAA-H into PS, PMMA, PI, SBS and PEG solution (mass fraction of ISOAA-H in polymer is 1%), stirring for 2 hr, coating on quartz glass by dripping method, and oven drying; respectively testing the obtained sample and pure ISOAA-H powder on a fluorescence spectrometer, wherein the excitation wavelength is 365 nm; the test results are shown in FIG. 3, and from FIG. 3 it can be seen that ISOAA-H powder exhibits orange fluorescence with peak 599nm of emission peak; in addition, with the continuous increase of the polarity of the polymer matrix, the fluorescence peak of ISOAA-H in the polymer matrix gradually generates red shift, and obvious polarity dependence is shown;

(3) respectively mixing 1) PS and PI, 2) PS and SBS, and 3) PMMA and PI according to the mass ratio of 1:1, adding 1% of ISOAA-H (the mass fraction of ISOAA-H in the polymer blend is 1%), and then stirring for 2H to mix uniformly; the prepared 1% ISOAA-H doped polymer blend was spin coated on 1cm in a spin coater using a rate of 1000r/min²Then imaging on a fluorescence microscopeTesting, wherein exciting light is ultraviolet light; the test results are shown in fig. 4, and it can be seen from fig. 4 that under the fluorescence microscope, all three blends can show phase separation structures with different colors, for example, in the PS/SBS blend, the phase structure with the color of bright blue is the PS phase, and the other phase is the SBS phase (dark blue); it can be seen that in the PS/SBS blend (50:50 wt%), the PS phase is the continuous phase and the SBS is the discontinuous phase; in the blends of PS/PI and PMMA/PI, a very pronounced sea-island structure can be observed, the PS (PMMA) phase being the island phase and the PI being the continuous sea phase; therefore, ISOAA-H obtained by the invention can be used as an efficient environment-sensitive fluorescent probe molecule to be applied to the research of polymer phase separation visualization.

EXAMPLE 3 Synthesis of the environmentally sensitive fluorescent molecule ISOAA-M

The ISOAA-M structural formula and the synthetic route are shown as a formula IV:

in the reaction formula, BuLi is n-butyllithium, THF is tetrahydrofuran, AcOH is glacial acetic acid, and octane is n-octane.

The specific synthesis steps are as follows:

(1) dropwise adding n-butyllithium (4.2mL, 2.5M hexane solution, 10.4mmol) to a solution of 4-bromotoluene (1.77g, 10.4mol) in anhydrous tetrahydrofuran (30mL) at-78 ℃ under an argon atmosphere, maintaining the mixture at-78 ℃ for 1 hour, then dropwise adding a THF (10mL) solution (1.0g, 2.07mmol) of compound 1 to the mixture, after maintaining at 78 ℃ for 1 hour, slowly raising the temperature to room temperature, stirring overnight, and then quenching with water; the mixture was then poured into water and extracted with dichloromethane, the organic layer was dried over anhydrous sodium sulfate, then the solvent was removed under vacuum to give a yellow solid which was used directly in the next step;

(2) the yellow solid was added to a mixture of n-octane (100mL) and acetic acid (10mL), then 2 drops of concentrated sulfuric acid were added to the mixture under argon, the reaction was refluxed for 3 hours and quenched with water; the mixture was extracted with dichloromethane, and the combined organic layers were washed three times with water, and the organic layer was dried over anhydrous sodium sulfate; after removal of the solvent, the crude compound was purified by silica gel chromatography using a mixture of petroleum ether/dichloromethane (10: 1) as eluent to give IDS-M (398mg, 26.5%) as a yellow solid;

¹H NMR(400MHz,CDCl₃)δ7.87(d,J＝5.4Hz,2H),7.37(s,2H),7.18(d,J＝5.4Hz,2H),7.13(d,J＝8.2Hz,8H),7.05(d,J＝8.2Hz,8H),2.30(s,12H).HRMS(ESI)m/z:[M+Na]⁺,calcd for C₄₄H₃₄Se₂,745.0883；found,745.0858.

(3) IDS-M (318mg, 0.440mmol, 1eq) and NBS (172mg, 0.968mmol, 2.2eq) are dissolved in 15.00mL of chloroform and react for 2 hours in a dark place, after the reaction is finished, water is added to quench the reaction, a product is extracted by dichloromethane and washed by water, and an organic phase is added with anhydrous sodium sulfate and dried to obtain a crude product which is directly carried out in the next step;

(4) a mixed solution of 8.00mL of acetone, 10.0mL of dichloromethane and 11.0mL of water was prepared, and the crude product from the previous step was dissolved in the mixed solution, and sodium bicarbonate (600mg) and oxone (K) were added₂SO₄·KHSO₄·KHSO₅) (276mg, 0.449mmol, 1.5eq), reacting at normal temperature for 3h, and adding water to quench the reaction after the reaction is finished; the extract was washed three times with water and dichloromethane. The organic phase was dried over anhydrous sodium sulfate, and purified by column chromatography on 200-mesh 300-mesh silica gel (the developing solvent was PE: DCM ═ 1:1, the product showed bright yellow fluorescence under 365 UV lamp); yellow solid ISOAA-M43.0 mg was obtained in 18.2% yield.

¹H NMR(400MHz,CDCl₃,δ)14.55(s,1H),7.84(s,1H),7.24(d,J＝2.7Hz,2H),7.15–7.02(m,16H),6.34(s,1H),2.34(s,6H),2.32(s,6H).¹³C NMR(100MHz,CDCl₃,δ)164.88,161.67,159.68,155.51,153.64,149.96,143.25,140.88,139.53,137.60,137.42,133.82,132.88,129.52,129.43,129.37,128.48,127.57,123.47,122.21,117.05,64.49,61.36,21.00,20.94.HRMS(ESI)m/z:[M+H]⁺,calcd for C₄₄H₃₃BrO₃Se,769.0851；found,769.0899.

The fluorescence emission spectra of the product ISOAA-M of this example in different solvents are shown in FIG. 5 (concentration 10)^-5M, excitation wavelength of365nm), as can be seen from fig. 5, the wavelength of the fluorescence emission peak of ISOAA-M is continuously red-shifted with the increase of the polarity of the solvent, showing a very significant lyotropic discoloration phenomenon, the corresponding color gradually changes from blue to orange, substantially covering the visible light region; ISOAA-H is shown to be a very environmentally polar sensitive dye molecule.

Claims

1. An environmentally sensitive dye, wherein the environmentally sensitive dye has a structural formula shown in formula I:

wherein, A is₁And A₂Is an aromatic ring or a substituted aromatic ring, the aromatic ring is selenophene, benzene, thiophene, furan, bithiophene, benzothiophene, benzodithiophene, naphthalene or anthracene; r₁、R₂、R₃And R₄Selected from the following groups: alkyl, substituted benzene ring or substituted thiophene ring.

2. The environmentally sensitive dye of claim 1 wherein the substituents on the substituted aromatic ring are-F, -Cl, -Br, -I, -R, -OR, -SR, -NH₂At least one of-NHR or-NRR ', wherein R and R' are selected from alkyl straight chain or alkyl branched chain with the carbon number of 1-20.

3. The process for preparing environmentally sensitive dyes according to claim 1 or 2, characterized in that the process comprises: dissolving a compound shown in a formula II in an organic solvent, adding bromosuccinimide or bromine, and reacting at normal temperature to obtain a brominated product; the brominated product is directly dissolved in an organic solvent without purification; then adding an oxidant to carry out oxidation reaction to obtain the environment-sensitive dye shown in the formula I;

4. the method for preparing the environmentally sensitive dye according to claim 3, wherein the compound represented by the formula II is one selected from the following compounds:

5. the method for preparing the environmentally sensitive dye according to claim 3 or 4, wherein the oxidizing agent is hydrogen peroxide, m-chloroperoxybenzoic acid, potassium peroxydisulfate complex salt or oxygen.

6. The method of claim 3 or 4, wherein the organic solvent is at least one of chloroform, dichloromethane, acetone, or tetrahydrofuran.

7. The method for preparing the environmentally sensitive dye according to claim 3 or 4, wherein the method comprises the following steps:

(1) dissolving a compound shown in a formula II and bromosuccinimide or bromine in an organic solvent, reacting for 1-5 hours in a dark place, and adding water to quench the reaction after the reaction is finished; extracting and washing the product, and drying the organic phase to obtain a crude product, and directly carrying out the next step;

(2) directly dissolving the crude product obtained in the step (1) in an organic solvent, adding an oxidant, reacting at normal temperature for 0.5-4 h, and adding water to quench the reaction after the reaction is finished; extracting, washing, drying the organic phase, and purifying by using a chromatographic column to obtain a solid which is the environment sensitive dye.

8. The method of claim 5, wherein the method comprises the steps of:

9. The method of claim 6, comprising the steps of:

10. The environmental sensitive dye is used in the field of polymer phase separation visual detection or as a pH-responsive smart material, wherein the environmental sensitive dye is the environmental sensitive dye as claimed in claim 1 or 2; or a dye obtained by the preparation method of any one of claims 3 to 9.