Double-state emission fluorescent dye and preparation method thereof

Abstract

The preparation method comprises the following steps: carrying out reflux reaction on 4-bromo-1, 8-naphthalic anhydride and primary amine in an organic solvent to obtain an intermediate product, and carrying out C-N coupling reaction on the intermediate product, a compound containing a nitrogen secondary amine electron-donating group, alkali and a catalyst in the organic solvent to obtain the double-state emission fluorescent dye. The two-state emission dye is obtained. An amino auxochrome group of a bridge ring structure is modified in a 4-bromine-1, 8-naphthalimide parent, the fluorescence quantum yield of the dye in a polar solvent is improved through the characteristic that nitrogen atom lone pair electrons of the nitrogen-containing bridge ring structure are not easy to overturn, and pi-pi stacking, which is not beneficial to emission, of the dye is inhibited through the large steric hindrance effect of the bridge ring structure; the dye shows bright fluorescence emission in non-polar and polar solvents, also has a very strong fluorescence quantum yield in a solid state, and shows a quantum yield greater than 94% when the dye is dispersed in an EVA (Ethylene-Vinyl Acetate) film.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescent dyes, and in particular to a dual-state emission fluorescent dye and a preparation method thereof. Background Art

[0002] Highly fluorescent dyes are characterized by high sensitivity, simple operation, and ease of detection, and are widely used for detection and labeling in many fields such as biomedicine, chemical analysis, and materials science. However, the application range of traditional fluorescent dyes has been reduced due to the aggregation-induced quenching effect, that is, the dye forms π-π stacking during the aggregation process, which is not conducive to emission. The emergence of the aggregation-induced emission effect broke this deadlock and quickly triggered a research boom. The dye is in a non-emissive state in solution and emits strong fluorescence when aggregated. Although the introduction of aggregation-induced emission solves the shortcomings of aggregation-induced quenching of traditional fluorescent dyes, it only emits light in the aggregated state, which inevitably limits its application. Therefore, how to balance emission in both solution and aggregated states has become a new research goal.

[0003] Dual-state emission, where dyes emit fluorescence both in solution and in the solid state, has evolved into a design concept characterized by the coexistence of rigidity and distortion. Rigidity refers to the conjugated rigid structure of the fluorophore, which reduces non-radiative transitions in solution and improves the fluorescence quantum yield in solution. Twist, on the other hand, refers to the presence of a slightly twisted conformation in the dye that allows the molecule to adopt a slightly twisted conformation during crystallization or aggregation. Slight changes in molecular shape reduce the likelihood of harmful π-π intermolecular interactions. It is worth noting that while a certain degree of freedom is required, this can lead to undesirable relaxation pathways, resulting in non-emissive states. During this period, many novel and complex structures have been reported, but these require more design time and complex synthetic steps. It is worth considering how to transform classic fluorescent dyes into dual-state emitting dyes.

[0004] Among the dyes reported so far, the ICT (intramolecular charge transfer) structure with dialkylamino groups as electron-donating groups is the most classic, but its quantum yield in polar solvents is extremely low, and its emission is limited by the π-π stacking it forms in the solid state, which is not conducive to emission. Based on this, some laboratories have reported the development of fluorescent dyes based on three- and four-membered nitrogen heterocycles and six-membered nitrogen heterocycles containing quaternary ammonium salts and sulfone groups as auxochromophores. This type of functional dye has strong emission capabilities because it overcomes the twisted intramolecular charge transfer (TICT) effect in polar solvents. While the TICT effect explains the fluorescence quenching mechanism of fluorophores in polar solvents, among the reported structures, only nitrogen-containing three- or four-membered heterocycles and six-membered nitrogen heterocycles containing quaternary ammonium salts or sulfone groups can overcome the TICT effect in polar solvents. Five-membered pyrrolidine and six-membered piperidine heterocycles cannot prevent the TICT effect. This may be because the lone pair of electrons in the nitrogen atom of the amino auxochromophore is in a relatively unstable state. That is, the lone pair of electrons in the nitrogen atom conjugated to the fluorophore can be located above or below the plane of the fluorophore and continuously undergo conical flipping, resulting in energy loss through nonradiative relaxation, leading to extremely low quantum yields of fluorescent dyes. The nitrogen atom of aziridine cannot flip freely, which means that when the aziridine is connected to the chromophore through a nitrogen-carbon bond, the nitrogen atom is not easily flipped, and the lone pair of electrons is relatively fixed. However, there is relatively little literature on six-membered nitrogen heterocycles containing quaternary ammonium salts or sulfone groups. Based on existing knowledge, it is speculated that when six-membered heterocyclic piperidines serve as auxochromophores, the nitrogen atom's cone-shaped flip participates in the equilibrium between two chair conformations. The lone pair of electrons on the nitrogen atom can be positioned above or below the plane of the chromophore, and this flipping occurs continuously. When the six-membered ring contains a quaternary ammonium salt or sulfone group, these two groups form hydrogen bonds or solvation with water, making the flipping of the two chair conformations relatively difficult. The amino group is less likely to flip, and the lone pair of electrons remains relatively fixed. Furthermore, neither five-membered heterocyclic pyrrolidines nor six-membered heterocyclic piperidines, nor nitrogen-containing three- and four-membered heterocycles or six-membered nitrogen heterocycles containing quaternary ammonium salts or sulfone groups, exhibit bright solid-state emission.

[0005] The above problems limit the possibility of converting classical dyes into dual-state emission dyes. Therefore, it is urgent to propose a new design method to convert aggregation-induced quenching dyes into dual-state emission dyes. Summary of the Invention

[0006] In response to the deficiencies in the prior art, the present invention provides a dual-state emission fluorescent dye and a preparation method thereof. An amino auxochromophore of a bridged ring structure is modified in a 4-bromo-1,8-naphthalene diimide matrix through Buchwald-Hartwig coupling. The fluorescence quantum yield of the dye in polar solvents is improved by utilizing the characteristic that the lone pair electrons of the nitrogen atom in the nitrogen-containing bridged ring structure are not easily flipped. At the same time, the large steric effect of the bridged ring structure inhibits the π-π stacking of the dye that is not conducive to emission. Based on this, the fluorescence characteristics of the classic naphthalene diimide dye are converted from aggregation-induced quenching to dual-state emission.

[0007] In order to solve the above technical problems, the first aspect of the present invention provides a dual-state emission fluorescent dye, the general structural formula of the dual-state emission fluorescent dye is shown in formula (2):

[0008]

[0009] Among them, R 1 is a C1-C16 straight chain alkyl or Ph(CH2) n -phenyl substituent, n=0, 1 or 2; R 2 It is an electron-donating group for a secondary amine in a nitrogen-bridged ring.

[0010] The dual-state emission fluorescent dye of the present invention improves the fluorescence quantum yield of the dye in polar solvents by utilizing the characteristic that the lone pair electrons of the nitrogen atom in the nitrogen-containing bridge ring structure are not easily flipped. At the same time, the large steric effect of the bridge ring structure inhibits the π-π stacking of the dye that is not conducive to emission, thereby realizing the dual-state emission of the fluorescent dye.

[0011] Furthermore, the R 1 It is a straight chain alkyl group, such as -CH3, -C4H9, -C8H 17 、-C 12 H 25 and -C 16 H 33 or a benzene substituted group, such as -Ph, -Bn, or Ph(CH2)2-.

[0012] Furthermore, the R 2 It is 7-azabicyclo[2.2.1]heptan-7-yl.

[0013] Furthermore, the structural formula of the dual-state emission fluorescent dye is selected from one of Formulas 2a-2h:

[0014]

[0015] The second aspect of the present invention provides a method for preparing the dual-state emission fluorescent dye according to the first aspect, comprising the following steps:

[0016] S1, 4-bromo-1,8-naphthalene dicarboxylic anhydride and R1 The primary amine is refluxed in an organic solvent to obtain a compound of formula (1):

[0017]

[0018] Among them, R 1 is a C1-C16 straight chain alkyl or Ph(CH2) n -phenyl substituent, n=0, 1 or 2;

[0019] S2. The compound of formula (1), a compound containing a nitrogen secondary amine electron-donating group, a base and a catalyst undergo CN coupling reaction in an organic solvent to obtain the dual-state emission dye.

[0020] The present invention modifies an amino auxochromophore with a bridged ring structure into a 4-bromo-1,8-naphthalene diimide matrix through Buchwald-Hartwig coupling. The fluorescence quantum yield of the dye in a polar solvent is improved by utilizing the characteristic that the lone pair electrons of the nitrogen atom in the nitrogen-containing bridged ring structure are not easily flipped. The π-π stacking of the dye that is not conducive to emission is suppressed by the large steric effect of the bridged ring structure, thereby converting the fluorescence characteristics of the classic naphthalene diimide dye from aggregation-induced quenching to dual-state emission.

[0021] Further, in S1, the 4-bromo-1,8-naphthalene dicarboxylic anhydride and the 1 The molar ratio of the primary amine group is 1:(1-3).

[0022] Furthermore, in S1, the temperature of the reflux reaction is 78-100° C., and the reaction time is 3-12 h.

[0023] Furthermore, in S1, the organic solvent is ethanol.

[0024] Furthermore, in S2, the compound containing a nitrogen secondary amine electron-donating group is 7-azabicyclo[2.2.1]heptane hydrochloride.

[0025] Furthermore, in S2, the base is one or more of cesium carbonate, sodium tert-butoxide, and potassium phosphate.

[0026] Furthermore, in S2, the catalyst is a palladium catalyst, preferably Pd(dppf)Cl2.

[0027] Furthermore, in S2, the molar ratio of the compound of formula (1), the compound containing a nitrogen secondary amine electron-donating group, and the base is 1:(1.1-1.5):(2.5-3.5).

[0028] Furthermore, in S2, the amount of the catalyst added is 3%-10% of the total mass of the coupling reaction system.

[0029] Furthermore, in S2, the coupling reaction temperature is 25-50°C.

[0030] Furthermore, in S2, the organic solvent is one or more of 1,4-dioxane, dimethyl sulfoxide, N,N-dimethylformamide and hexamethylphosphoric triamide.

[0031] Beneficial effects of the present invention:

[0032] The present invention uses a secondary amine of an azo-bridged ring as an electron-donating amino auxochromophore and modifies the 4-bromo-1,8-naphthalene diimide matrix through Buchwald-Hartwig coupling to obtain a dye with dual-state emission. The fluorescence quantum yield of the dye in polar solvents is improved by utilizing the characteristic that the lone pair electrons of the nitrogen atom in the nitrogen-containing bridged ring structure are not easily flipped, and the π-π stacking of the dye that is not conducive to emission is suppressed by the large steric effect of the bridged ring structure.

[0033] The dye of the present invention exhibits bright fluorescence emission in both non-polar and polar solvents and has a strong fluorescence quantum yield in a solid state. When the dye is dispersed in an EVA film, the quantum yield exhibits greater than 94%.

[0034] The dye of the present invention provides the possibility for polar environment fluorescence imaging in a solution state, and the high-brightness emission in a solid state and a thin film also provides an option for OLED or OPV light-emitting devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 This is a synthetic route for the dual-state emission fluorescent dye of the present invention;

[0037] Figure 2 A and B are the superimposed graphs of the UV-visible absorption and fluorescence emission spectra of dyes 2a-2h in water, dimethyl sulfoxide, and 1,4-dioxane, respectively;

[0038] Figure 3 Where ah are the excitation and emission spectra of dyes 2a-2h in solid state, respectively;

[0039] Figure 4 Wherein ah are the excitation spectra and emission spectra of dyes 2a-2h in the EVA film state, respectively. DETAILED DESCRIPTION

[0040] The following will provide a clear and complete description of the technical solutions of the present invention in conjunction with specific embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] This embodiment relates to a method for preparing a dual-state emission fluorescent dye, comprising the following steps:

[0042] S1, 4-bromo-1,8-naphthalene dicarboxylic anhydride and R 1 The primary amine is refluxed in an organic solvent to obtain a compound of formula (1):

[0043] Among them, R 1 is a C1-C16 straight chain alkyl or Ph(CH2) n -phenyl substituent, n=0, 1 or 2;

[0044] S2. A compound of formula (1), a compound containing a nitrogen secondary amine electron-donating group, a base and a catalyst are subjected to a CN coupling reaction in an organic solvent to obtain the dual-state emission dyes 2a-2h. The synthesis route is as follows: Figure 1 shown.

[0045] Example 1

[0046] This embodiment relates to a method for preparing a dual-state emission fluorescent dye 2a, comprising the following steps:

[0047] (1) 4-Bromo-1,8-naphthalene dicarboxylic anhydride (5.00 g, 18.05 mmol) was dissolved in 100 ml of ethanol, and 40% aqueous methylamine (1.60 ml, 19.85 mmol) was added. The reaction solution was stirred at 80°C for 3 hours. After the reaction was completed, the reaction solution was cooled to room temperature, and the precipitated solid was filtered to obtain 4.82 g of white solid 1a with a yield of 92%.

[0048] (2) Compound 1a (1.00 g, 3.45 mmol), 7-azabicyclo[2.2.1]heptane hydrochloride (0.55 g, 4.14 mmol), Pd(dppf)Cl2 (0.13 g, 0.17 mmol) and sodium tert-butoxide (0.83 g, 8.62 mmol) were added to a 25 ml two-necked flask in sequence. The atmosphere was purged with nitrogen three times, and then 10 ml of N,N-dimethylformamide was added. The temperature was raised to 50°C and stirred for 5 hours. After the reaction was completed, the reaction solution was cooled to room temperature and extracted with ethyl acetate (20 ml × 2) and water (30 ml). The organic phases were combined and washed with saturated brine (30 ml × 3). The solvent of the organic layer was then removed by rotary evaporation. The final product was purified by column chromatography with EA / PE (1:4, v / v) to obtain 0.64 g of yellow solid compound 2a with a yield of 61%. Dye 2a was characterized by H NMR, C NMR, and MS. The characterization results are as follows:

[0049] 1 H NMR (400MHz, CDCl3) δ (ppm) 8.58 (dd, J=7.2, 1.2Hz, 1H, Ar-H), 8.45 (dd, J=8.4, 1.2Hz, 1H, Ar-H), 8.42 (d, J=8.2Hz, 1H, Ar-H), 7.64 (dd, J=8.5, 7.3 Hz,1H,Ar-H),7.05(d,J=8.2Hz,1H,Ar-H),4.38(p,J=2.4Hz,2H,2×CH),3.53(s,3H,CH3),2.06-1.94(m,4H,2×CH2),1.57(d,J=7.2Hz,4H,2×CH2).

[0050] 13 CNMR (151MHz, CDCl3) δ (ppm) 164.9, 164.4, 151.4, 132.7, 131.0, 130.9, 130..0, 125.2, 124.8, 122.8, 114.3, 113.0, 61.4, 29.0, 26.8.

[0051] HRMS (TOF, ESI + ):m / z calcd C 19 H 19 N2O2 + for[M+H] + :307.1442,found:307.1444.

[0052] Example 2

[0053] This embodiment relates to a method for preparing a dual-state emission fluorescent dye 2b, comprising the following steps:

[0054] (1) 4-Bromo-1,8-naphthalene dicarboxylic anhydride (5.00 g, 18.05 mmol) was dissolved in 100 ml of ethanol, and n-butylamine (2.64 g, 36.09 mmol) was added thereto. The reaction solution was stirred at 80°C for 12 hours. After the reaction was completed, the reaction solution was cooled to room temperature, and the precipitated solid was filtered. The obtained solid was recrystallized from ethanol to obtain 3.88 g of yellow solid 1b, with a yield of 65%;

[0055] (2) Compound 1b (1.00 g, 3.01 mmol), 7-azabicyclo[2.2.1]heptane hydrochloride (0.48 g, 3.61 mmol), Pd(dppf)Cl2 (0.11 g, 0.15 mmol) and sodium tert-butoxide (0.72 g, 7.53 mmol) were added to a 25 ml two-necked flask in sequence. The atmosphere was replaced with nitrogen three times, and then 10 ml of N,N-dimethylformamide was added. The temperature was raised to 50°C and stirred for 5 hours. After the reaction was completed, the reaction solution was cooled to room temperature and extracted with ethyl acetate (20 ml × 2) and water (30 ml). The organic phases were combined and washed with saturated brine (30 ml × 3). The solvent of the organic layer was then removed by rotary evaporation. The final product was purified by column chromatography with DCM / PE (1:1, v / v) to obtain 0.68 g of yellow solid compound 2b with a yield of 65%. Dye 2b was characterized by H NMR, C NMR, and MS. The results are as follows:

[0056] 1 H NMR (400MHz, CDCl3) δ (ppm) 8.57 (dd, J=7.3, 1.1Hz, 1H, Ar-H), 8.45 (dd, J=8.4, 1.2Hz, 1H, Ar-H), 8 .41(d,J=8.2Hz,1H,Ar-H),7.64(dd,J=8.4,7.3Hz,1H,Ar-H),7.05(d,J=8.2Hz,1H,Ar-H),4.38(p, J=2.4Hz,2H,2×CH),4.16(t,J=7.5Hz,2H,CH2),2.00(d,J=6.2Hz,4H,2×CH2),1.70(p,J=7.6Hz,2H , CH2), 1.57 (d, J=7.2Hz, 4H, 2×CH2), 1.44 (dq, J=14.7, 7.4Hz, 2H, CH2), 0.97 (t, J=7.3Hz, 3H, CH3).

[0057] 13C NMR(151MHz,CDCl3)δ(ppm)164.7,164.1,151.3,132.7,131.0,130.8,130 .1,125.2,124.8,123.0,114.5,113.0,61.4,40.0,30.3,29.0,20.4,13.9.

[0058] HRMS (TOF, ESI + ):m / z calcd C 22 H 25 N2O2 + for[M+H] + :349.1911,found:349.1916.

[0059] Example 3

[0060] This embodiment relates to a method for preparing a dual-state emission fluorescent dye 2c, comprising the following steps:

[0061] (1) 4-Bromo-1,8-naphthalene dicarboxylic anhydride (5.00 g, 18.05 mmol) was dissolved in 100 ml of ethanol, and n-octylamine (2.57 g, 19.85 mmol) was added. The reaction solution was stirred at 80°C for 6 hours. After the reaction was completed, the reaction solution was cooled to room temperature, and the precipitated solid was filtered to obtain 5.78 g of white solid 1c with a yield of 83%.

[0062] (2) Compound 1c (1.00 g, 2.58 mmol), 7-azabicyclo[2.2.1]heptane hydrochloride (0.41 g, 3.10 mmol), Pd(dppf)Cl2 (0.09 g, 0.13 mmol) and sodium tert-butoxide (0.74 g, 7.73 mmol) were added to a 25 ml two-necked flask in sequence. The atmosphere was purged with nitrogen three times, and then 10 ml of N,N-dimethylformamide was added. The temperature was raised to 50°C and stirred for 4 hours. After the reaction was completed, the reaction solution was cooled to room temperature and extracted with ethyl acetate (20 ml × 2) and water (30 ml). The organic phases were combined and washed with saturated brine (30 ml × 3). The solvent of the organic layer was then removed by rotary evaporation. The final product was purified by column chromatography with EA / PE (1:20, v / v) to obtain 0.35 g of yellow solid compound 2c with a yield of 33%. The dye 2c was characterized by H NMR, C NMR, and MS. The characterization results are as follows:

[0063] 1H NMR (400MHz, CDCl3) δ (ppm) 8.57 (dd, J=7.3, 1.2Hz, 1H, Ar-H), 8.45 (dd, J=8.4, 1.2Hz, 1H, Ar-H) ,8.41(d,J=8.2Hz,1H,Ar-H),7.64(dd,J=8.4,7.3Hz,1H,Ar-H),7.05(d,J=8.2Hz,1H,Ar-H),4. 37(p,J=2.4Hz,2H,2×CH),4.15(t,J=7.6Hz,2H,CH2),2.08-1.91(m,4H,2×CH2),1.71(p,J=7.4H z,2H,CH2),1.57(d,J=7.2Hz,4H,2×CH2),1.46-1.23(m,10H,5×CH2),0.87(t,J=6.8Hz,3H,CH3).

[0064] 13 C NMR (151MHz, CDCl3) δ (ppm) 164.6,164.1,151.3,132.7,131.0,130.8,130.1,125.2,1 24.8,123.0,114.5,113.0,61.4,40.3,31.8,29.4,29.2,29.0,28.2,27.2,22.6,14.1.

[0065] HRMS (TOF, ESI + ):m / z calcd C 26 H 33 N2O2 + for[M+H] + :405.2537,found:405.2540.

[0066] Example 4

[0067] This embodiment relates to a method for preparing a dual-state emission fluorescent dye 2d, comprising the following steps:

[0068] (1) 4-Bromo-1,8-naphthalene dicarboxylic anhydride (5.00 g, 18.05 mmol) was dissolved in 100 ml of ethanol, and n-dodecylamine (3.68 g, 19.85 mmol) was added thereto. The reaction solution was stirred at 80°C for 12 hours. After the reaction was completed, the reaction solution was cooled to room temperature, and the precipitated solid was filtered to obtain 7.30 g of white solid 1d, with a yield of 91%;

[0069] (2) Compound 1d (1.00 g, 2.25 mmol), 7-azabicyclo[2.2.1]heptane hydrochloride (0.36 g, 2.70 mmol), Pd(dppf)Cl2 (0.08 g, 0.11 mmol), and sodium tert-butoxide (0.65 g, 6.75 mmol) were added to a 25 ml two-necked flask in sequence. The atmosphere was purged with nitrogen three times, and then 10 ml of N,N-dimethylformamide was added. The temperature was raised to 50°C and stirred for 4 hours. After the reaction was completed, the reaction solution was cooled to room temperature and extracted with ethyl acetate (20 ml × 2) and water (30 ml). The organic phases were combined and washed with saturated brine (30 ml × 3). The solvent of the organic layer was then removed by rotary evaporation. The final product was purified by column chromatography with EA / PE (1:20, v / v) to obtain 0.35 g of yellow solid compound 2d with a yield of 33%. The dye 2d was characterized by H NMR, C NMR and MS, and the characterization results are as follows:

[0070] 1 H NMR (400MHz, CDCl3) δ (ppm) 8.57 (dd, J=7.3, 1.2Hz, 1H, Ar-H), 8.44 (dd, J=8.4, 1.2Hz, 1H, Ar-H) ,8.41(d,J=8.2Hz,1H,Ar-H),7.64(dd,J=8.4,7.3Hz,1H,Ar-H),7.05(d,J=8.2Hz,1H,Ar-H),4. 37(p,J=2.4Hz,2H,2×CH),4.15(t,J=7.6Hz,2H,CH2),2.05-1.95(m,4H,2×CH2),1.71(p,J=7.4H z,2H,CH2),1.57(d,J=7.2Hz,4H,2×CH2),1.42-1.22(m,18H,9×CH2),0.87(t,J=6.8Hz,3H,CH3).

[0071] 13 C NMR (151MHz, CDCl3) δ (ppm) 164.6,164.1,151.3,132.7,131.0,130.8,130.1,125.2,124.8,123.0 ,114.5,113.0,61.4,40.3,31.9,29.8,29.7,29.6,29.6,29.5,29.4,29.1,28.2,27.2,22.7,14.1.

[0072] HRMS (TOF, ESI + ):m / z calcd C 30 H 41 N2O2 +for[M+H] + :461.3163,found:461.3165.

[0073] Example 5

[0074] This embodiment relates to a method for preparing a dual-state emission fluorescent dye 2e, comprising the following steps:

[0075] (1) 4-Bromo-1,8-naphthalene dicarboxylic anhydride (5.00 g, 18.05 mmol) was dissolved in 150 ml of ethanol, and n-hexadecylamine (4.79 g, 19.85 mmol) was added thereto. The reaction solution was stirred at 80°C for 12 hours. After the reaction was completed, the reaction solution was cooled to room temperature, and the precipitated solid was filtered to obtain 4.20 g of white solid 1e, with a yield of 46%;

[0076] (2) Compound 1e (1.00 g, 2.00 mmol), 7-azabicyclo[2.2.1]heptane hydrochloride (0.32 g, 2.40 mmol), Pd(dppf)Cl2 (0.07 g, 0.10 mmol) and sodium tert-butoxide (0.58 g, 6.00 mmol) were added to a 25 ml two-necked flask in sequence. The atmosphere was purged with nitrogen three times, and then 10 ml of N,N-dimethylformamide was added. The temperature was raised to 50°C and stirred for 4 hours. After the reaction was completed, the reaction solution was cooled to room temperature and extracted with ethyl acetate (20 ml × 2) and water (30 ml). The organic phases were combined and washed with saturated brine (30 ml × 3). The solvent of the organic layer was then removed by rotary evaporation. The final product was purified by column chromatography with EA / PE (1:20, v / v) to obtain 0.29 g of yellow solid compound 2e with a yield of 28%. The dye 2e was characterized by H NMR, C NMR, and MS. The characterization results are as follows:

[0077] 1H NMR (400MHz, CDCl3) δ (ppm) 8.57 (dd, J=7.3, 1.2Hz, 1H, Ar-H), 8.45 (dd, J=8.5, 1.2Hz, 1H, Ar-H), 8.41 (d,J=8.2Hz,1H,Ar-H),7.64(dd,J=8.4,7.3Hz,1H,Ar-H),7.05(d,J=8.2Hz,1H,Ar-H),4.37(p,J=2.3H z,2H,2×CH),4.15(t,J=7.6Hz,2H,CH2),2.06-1.94(m,4H,2×CH2),1.71(p,J=7.3Hz,2H,CH2),1.59(d, J=6.5Hz,2H,CH2),1.55(d,J=6.5Hz,2H,CH2),1.43-1.23(m,26H,13×CH2),0.88(t,J=6.7Hz,3H,CH3).

[0078] 13 C NMR (151MHz, CDCl3) δ (ppm) 164.6,164.1,151.3,132.7,131.0,130.8,130.1,125.2,124.8,123.0 ,114.5,113.0,61.4,40.3,31.9,29.7,29.7,29.6,29.6,29.4,29.4,29.0,28.2,27.2,22.7,14.1.

[0079] HRMS (TOF, ESI + ):m / z calcd C 34 H 49 N2O2 + for[M+H] + :517.3789,found:517.3796.

[0080] Example 6

[0081] This embodiment relates to a method for preparing a dual-state emission fluorescent dye 2f, comprising the following steps:

[0082] (1) 4-Bromo-1,8-naphthalene dicarboxylic anhydride (5.00 g, 18.05 mmol) was dissolved in 150 ml of ethanol, and aniline (2.00 g, 21.66 mmol) was added thereto. The reaction solution was stirred at 80°C for 12 hours. After the reaction was completed, the reaction solution was cooled to room temperature, and the precipitated solid was filtered to obtain 4.20 g of white solid 1f, with a yield of 71%;

[0083] (2) Compound 1f (1.00 g, 2.84 mmol), 7-azabicyclo[2.2.1]heptane hydrochloride (0.46 g, 3.41 mmol), Pd(dppf)Cl2 (0.10 g, 0.14 mmol) and sodium tert-butoxide (0.68 g, 7.10 mmol) were added to a 25 ml two-necked flask in sequence. The atmosphere was purged with nitrogen three times, and then 10 ml of N,N-dimethylformamide was added. The temperature was raised to 50°C and stirred for 4 hours. After the reaction was completed, the reaction solution was cooled to room temperature and extracted with ethyl acetate (20 ml × 2) and water (30 ml). The organic phases were combined and washed with saturated brine (30 ml × 3). The solvent of the organic layer was then removed by rotary evaporation. The final product was purified by column chromatography with EA / PE (1:20, v / v) to obtain 0.59 g of yellow solid compound 2f with a yield of 57%. The dye 2f was characterized by H NMR, C NMR, and MS. The characterization results are as follows:

[0084] 1 H NMR (400MHz, CDCl3) δ (ppm) 8.61 (dd, J=7.3, 1.2Hz, 1H, Ar-H), 8.51 (dd, J=8.5, 1.2Hz, 1H ,Ar-H),8.45(d,J=8.2Hz,1H,Ar-H),7.67(dd,J=8.5,7.3Hz,1H,Ar-H),7.56-7.51(m,2H, 2×Ar-H),7.48-7.43(m,1H,Ar-H),7.33-7.28(m,2H,2×Ar-H),7.09(d,J=8.2Hz,1H,Ar-H) ,4.41(p,J=2.5Hz,2H,2×CH),2.02(d,J=6.3Hz,4H,2×CH2),1.60(d,J=7.2Hz,4H,2×CH2).

[0085] 13 C NMR (151MHz, CDCl3) δ (ppm) 164.8,164.2,151.7,135.8,133.1,131.5,131.3 ,130.6,129.3,128.7,128.4,125.3,124.9,123.1,114.4,113.1,61.5,29.1.

[0086] HRMS (TOF, ESI + ):m / z calcd:C 24 H 21 N2O2 + for[M+H] + :369.1598,found:369.1608.

[0087] Example 7

[0088] This embodiment relates to a method for preparing a dual-state emission fluorescent dye 2g, comprising the following steps:

[0089] (1) 4-Bromo-1,8-naphthalene dicarboxylic anhydride (5.00 g, 18.05 mmol) was dissolved in 150 ml of ethanol, and benzylamine (2.30 g, 21.66 mmol) was added thereto. The reaction solution was stirred at 80°C for 6 hours. After the reaction was completed, the reaction solution was cooled to room temperature, and the precipitated solid was filtered to obtain 6.03 g of white solid (yield 91%).

[0090] (2) Compound 1g (1.00 g, 2.73 mmol), 7-azabicyclo[2.2.1]heptane hydrochloride (0.44 g, 3.27 mmol), Pd(dppf)Cl2 (0.10 g, 0.14 mmol) and sodium tert-butoxide (0.66 g, 6.83 mmol) were added to a 25 ml two-necked flask in sequence. The atmosphere was purged with nitrogen three times, and then 10 ml of N,N-dimethylformamide was added. The temperature was raised to 50°C and stirred for 4 hours. After the reaction was completed, the reaction solution was cooled to room temperature and extracted with ethyl acetate (20 ml × 2) and water (30 ml). The organic phases were combined and washed with saturated brine (30 ml × 3). The solvent of the organic layer was then removed by rotary evaporation. The final product was purified by column chromatography with DCM / PE (1:1, v / v) to obtain 0.55 g of yellow solid compound 2g with a yield of 53%. The dye 2g was characterized by H NMR, C NMR, and MS. The characterization results are as follows:

[0091] 1 H NMR (400MHz, CDCl3) δ (ppm) 8.58 (dd, J=7.3, 1.2Hz, 1H, Ar-H), 8.46-8.41 (m, 2H, 2×Ar-H ),7.63(dd,J=8.5,7.3Hz,1H,Ar-H),7.53(d,J=6.9Hz,2H,2×Ar-H),7.28(t,J=7.3Hz,2H ,2×Ar-H),7.21(t,J=7.3Hz,1H,Ar-H),7.05(d,J=8.2Hz,1H,Ar-H),5.37(s,2H,CH2),4. 37(p,J=2.4Hz,2H,2×CH),2.02-1.96(m,4H,2×CH2),1.58(s,2H,CH2),1.56(s,2H,CH2).

[0092] 13C NMR (151MHz, CDCl3) δ (ppm) 164.7,164.1,151.5,137.7,133.0,131.3,131.0,13 0.2,128.8,128.3,127.2,125.2,124.8,122.9,114.3,113.0,61.5,43.3,29.0.

[0093] HRMS (TOF, ESI + ):m / z calcd:C 25 H 23 N2O2 + for[M+H] + :383.1755,found:383.1761.

[0094] Example 8

[0095] This embodiment relates to a method for preparing a dual-state emission fluorescent dye 2h, comprising the following steps:

[0096] (1) 4-Bromo-1,8-naphthalene dicarboxylic anhydride (5.00 g, 18.05 mmol) was dissolved in 150 ml of ethanol, and phenylethylamine (2.62 g, 21.66 mmol) was added thereto. The reaction solution was stirred at 80°C for 6 hours. After the reaction was completed, the reaction solution was cooled to room temperature, and the precipitated solid was filtered to obtain 6.27 g of gray solid (1h), with a yield of 91%;

[0097] (2) Compound 1h (1.00 g, 2.63 mmol), 7-azabicyclo[2.2.1]heptane hydrochloride (0.42 g, 3.16 mmol), Pd(dppf)Cl2 (0.09 g, 0.13 mmol) and sodium tert-butoxide (0.63 g, 6.57 mmol) were added to a 25 ml two-necked flask in sequence. The atmosphere was replaced with nitrogen three times, and then 10 ml of N,N-dimethylformamide was added. The temperature was raised to 50°C and stirred for 4 hours. After the reaction was completed, the reaction solution was cooled to room temperature and extracted with ethyl acetate (20 ml × 2) and water (30 ml). The organic phases were combined and washed with saturated brine (30 ml × 3). The solvent of the organic layer was then removed by rotary evaporation. The final product was purified by column chromatography with EA / PE (1:20, v / v) to obtain 0.50 g of yellow solid compound 2h with a yield of 48%. The dye 2h was characterized by H NMR, C NMR and MS, and the characterization results are as follows:

[0098] 1H NMR (400MHz, CDCl3) δ (ppm) 8.58 (dd, J=7.3, 1.2Hz, 1H, Ar-H), 8.46 (dd, J=8.5, 1.2Hz, 1H, Ar-H), 8. 43(d,J=8.2Hz,1H,Ar-H),7.65(dd,J=8.5,7.3Hz,1H,Ar-H),7.39(d,J=6.8Hz,2H,2×Ar-H),7.32(t, J=7.6Hz,2H,2×Ar-H),7.22(t,J=7.3Hz,1H,Ar-H),7.06(d,J=8.2Hz,1H,Ar-H),4.38(t,J=8.2Hz,4H ,2×CH2),3.05-2.97(p,J=3.3Hz,2H,2×CH),2.05-1.96(m,4H,2×CH2),1.58(d,J=7.0Hz,4H,2×CH2).

[0099] 13 C NMR (101MHz, CDCl3) δ (ppm) 164.5, 164.0, 151.2, 139.1, 132.7, 131.2, 131.0, 130. 2,129.1,128.5,126.4,125.3,124.9,123.0,114.6,113.2,61.6,41.7,34.4,29.1.

[0100] HRMS (TOF, ESI + ):m / z calcd:C 26 H 25 N2O2 + for[M+H] + :397.1911,found:397.1914.

[0101] Test Case

[0102] The UV absorption and fluorescence emission of the fluorescent dyes 2a-2h prepared in Examples 1-8 were tested in water, dimethyl sulfoxide (DMSO) and 1,4-dioxane (dye concentration was 10 μM). The results are as follows: Figure 2 shown. Figure 2 Where ah is the superposition of the UV-visible absorption spectra and fluorescence emission spectra of dyes 2a-2h in water, dimethyl sulfoxide and 1,4-dioxane, respectively. a nm; b ×10 4 M -1 cm -1 ; c%, with coumarin-153 (Φ = 55% in ethanol) as a reference. Dye 2a has maximum absorption wavelengths of 409 nm, 420 nm, and 406 nm, respectively. At an excitation wavelength of 410 nm and a slit width of 3 nm / 3 nm, its maximum emission wavelengths are 565 nm, 536 nm, and 509 nm, respectively, with relative fluorescence quantum yields of 28%, 75%, and 96%, respectively. Dye 2b has maximum absorption wavelengths of 414 nm, 420 nm, and 406 nm. At an excitation wavelength of 410 nm and a slit width of 3 nm / 3 nm, its maximum emission wavelengths are 551 nm, 536 nm, and 509 nm, respectively, with relative fluorescence quantum yields of 20%, 73%, and 96%, respectively. Dye 2c has maximum absorption wavelengths of 409 nm, 420 nm, and 406 nm. At an excitation wavelength of 410 nm and a slit width of 3 nm / 3 nm, its maximum emission wavelengths are 533 nm, 536 nm, and 509 nm, with relative fluorescence quantum yields of 19%, 71%, and 95%, respectively. Dye 2d has maximum absorption wavelengths of 409 nm, 420 nm, and 406 nm. At an excitation wavelength of 410 nm and a slit width of 3 nm / 3 nm, its maximum emission wavelengths are 530 nm, 536 nm, and 509 nm, with relative fluorescence quantum yields of 18%, 70%, and 96%, respectively. Dye 2e has maximum absorption wavelengths of 409 nm, 420 nm, and 406 nm. At an excitation wavelength of 410 nm and a slit width of 3 nm / 3 nm, its maximum emission wavelengths are 530 nm, 536 nm, and 509 nm, with relative fluorescence quantum yields of 18%, 76%, and 95%, respectively. Dye 2f has maximum absorption wavelengths of 415 nm, 420 nm, and 406 nm. At an excitation wavelength of 410 nm and a slit width of 3 nm / 3 nm, its maximum emission wavelengths are 539 nm, 536 nm, and 509 nm, with relative fluorescence quantum yields of 19%, 74%, and 98%, respectively. Dye 2g has maximum absorption wavelengths of 419 nm, 420 nm, and 406 nm. At an excitation wavelength of 410 nm and a slit width of 3 nm / 3 nm, its maximum emission wavelengths are 541 nm, 536 nm, and 509 nm, with relative fluorescence quantum yields of 18%, 73%, and 96%, respectively. Dye 2h has maximum absorption wavelengths of 415 nm, 420 nm, and 406 nm. At an excitation wavelength of 410 nm and a slit width of 3 nm / 3 nm, its maximum emission wavelengths are 536 nm, 536 nm, and 509 nm, with relative fluorescence quantum yields of 18%, 76%, and 97%, respectively. Dyes 2a-2h exhibit bright fluorescence emission in both non-polar and polar solvents, with fluorescence quantum yields ranging from 95% to 98% in 1,4-dioxane, 70% to 76% in dimethyl sulfoxide, and 18% to 28% in water.

[0103] Table 1

[0104]

[0105]

[0106] The excitation and emission spectra of the fluorescent dyes 2a-2h prepared in Examples 1-8 were tested in a solid state. The results are as follows: Figure 3 shown. Figure 3 Where ah is the excitation spectrum and emission spectrum of dyes 2a-2h in solid state, respectively. a nm; b %, Φ measured using a calibrated integrating sphere system) show that the optimal excitation wavelength for dye 2a is 350 nm, its maximum emission wavelength is 540 nm, and its absolute fluorescence quantum yields are 67%. The optimal excitation wavelength for dye 2b is 367 nm, its maximum emission wavelength is 532 nm, and its absolute fluorescence quantum yields are 89%. The optimal excitation wavelength for dye 2c is 368 nm, its maximum emission wavelength is 526 nm, and its absolute fluorescence quantum yields are 92%. The optimal excitation wavelength for dye 2d is 367 nm, its maximum emission wavelength is 524 nm, and its absolute fluorescence quantum yields are 94%. The optimal excitation wavelength for dye 2e is 368 nm, its maximum emission wavelength is 522 nm, and its absolute fluorescence quantum yields are 94%. The optimal excitation wavelength for dye 2f is 368 nm, its maximum emission wavelength is 530 nm, and its absolute fluorescence quantum yields are 60%. The optimal excitation wavelength for dye 2g is 370 nm, its maximum emission wavelength is 524 nm, and its absolute fluorescence quantum yields are 81%. The optimal excitation wavelength for dye 2h is 368 nm, and its maximum emission wavelength is 516 nm. The absolute fluorescence quantum yields for dye 2a-2h are 92%, respectively. Thus, dyes 2a-2h also have strong fluorescence quantum yields in the solid state, with photoluminescence efficiencies ranging from 60% to 94%.

[0107] Table 2

[0108]

[0109] The excitation and emission spectra of the fluorescent dyes 2a-2h prepared in Examples 1-8 were tested in the EVA film state. The results are as follows: Figure 4 As shown, the film contains 0.1 wt% of a dual-state emission dye. Figure 4In Table 2, A and B represent the excitation and emission spectra of dyes 2a-2h in the EVA film state, respectively. As shown in Table 2, the optimal excitation wavelength for dye 2a is 404 nm, its maximum emission wavelength is 502 nm, and its absolute fluorescence quantum yields are 97%. The optimal excitation wavelength for dye 2b is 395 nm, its maximum emission wavelength is 504 nm, and its absolute fluorescence quantum yields are 94%. The optimal excitation wavelength for dye 2c is 406 nm, its maximum emission wavelength is 498 nm, and its absolute fluorescence quantum yields are 96%. The optimal excitation wavelength for dye 2d is 406 nm, its maximum emission wavelength is 499 nm, and its absolute fluorescence quantum yields are 97%. The optimal excitation wavelength for dye 2e is 407 nm, its maximum emission wavelength is 498 nm, and its absolute fluorescence quantum yields are 94%. The optimal excitation wavelength for dye 2f is 397 nm, its maximum emission wavelength is 507 nm, and its absolute fluorescence quantum yields are 97%. Dye 2g has an optimal excitation wavelength of 396 nm and a maximum emission wavelength of 506 nm; the absolute fluorescence quantum yields are 99%. Dye 2h has an optimal excitation wavelength of 406 nm and a maximum emission wavelength of 504 nm; the absolute fluorescence quantum yields are 96%. Thus, dyes 2a-2h also have strong fluorescence quantum yields in the EVA film state, with photoluminescence efficiencies ranging from 94% to 99%.

[0110] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A dual-state emission fluorescent dye, characterized in that The general structural formula of the dual-state emission fluorescent dye is shown in formula (2): Among them, R 1 is a C1-C16 straight chain alkyl or Ph(CH2) n -phenyl substituent, n=0, 1 or 2; R 2 It is an electron-donating group for a secondary amine in a nitrogen-bridged ring.

2. The dual-state emission fluorescent dye according to claim 1, wherein The R 2 It is 7-azabicyclo[2.2.1]heptan-7-yl.

3. A method for preparing the dual-state emission fluorescent dye according to any one of claims 1 to 2, characterized in that: The steps include: S1, 4-bromo-1,8-naphthalene dicarboxylic anhydride and R 1 The primary amine is refluxed in an organic solvent to obtain a compound of formula (1): Among them, R 1 is a C1-C16 straight chain alkyl or Ph(CH2) n -phenyl substituent, n=0, 1 or 2; S2. The compound of formula (1), a compound containing a nitrogen secondary amine electron-donating group, a base and a catalyst undergo CN coupling reaction in an organic solvent to obtain the dual-state emission dye.

4. The method for preparing a dual-state emission fluorescent dye according to claim 3, wherein: In S1, the 4-bromo-1,8-naphthalene dicarboxylic anhydride and the 1 The molar ratio of the primary amine group is 1:(1-3).

5. The method for preparing a dual-state emission fluorescent dye according to claim 3, wherein: In S1, the temperature of the reflux reaction is 78-100°C.

6. The method for preparing a dual-state emission fluorescent dye according to claim 3, wherein: In S2, the compound containing a nitrogen secondary amine electron-donating group is 7-azabicyclo[2.2.1]heptane hydrochloride.

7. The method for preparing a dual-state emission fluorescent dye according to claim 3, wherein: In S2, the base is one or more of cesium carbonate, sodium tert-butoxide, and potassium phosphate.

8. The method for preparing a dual-state emission fluorescent dye according to claim 3, wherein: In S2, the catalyst is a palladium catalyst.

9. The method for preparing a dual-state emission fluorescent dye according to claim 3, wherein: In S2, the molar ratio of the compound of formula (1), the compound containing a nitrogen secondary amine electron-donating group, and the base is 1: (1.1-1.5): (2.5-3.5).

10. The method for preparing a dual-state emission fluorescent dye according to claim 3, wherein: In S2, the coupling reaction temperature is 25-50°C.

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