A photomolecular switch based on benzothiazole hydrazone and its preparation method and application

Abstract

The present invention belongs to the technical field of organic single-molecule switches, and relates to a photomolecular switch based on benzothiazole hydrazone, and a preparation method and application thereof. The preparation method is to react benzothiazole hydrazone with imidazole formaldehyde to generate a new compound that connects benzothiazole and imidazole rings with a hydrazone bond as a bridge, and then obtain a photoswitch molecule with photochromic and fluorescence changes in solution, solid and film states through addition reaction and ion exchange reaction. The designed photoswitch molecule undergoes E→Z isomerization under 460nm light excitation, and Z→E isomerization under 365nm light excitation to obtain a photothermally stable Z / E isomer, which has the characteristics of large wavelength difference of Z / E isomer absorption spectrum, high Z / E isomerization conversion rate, fast Z / E isomerization photoconversion rate and simple preparation, solving the problem that common photoswitch molecules cannot take into account both high photoconversion rate and high photoconversion rate. This design strategy provides a new method for designing an ideal photomolecular switch.

Description

Technical Field

[0001] The invention belongs to the technical field of organic single-molecule switches and relates to a photomolecular switch based on benzothiazole hydrazone and a preparation method and application thereof. Background Art

[0002] Photomolecular switches can produce bidirectional reversible isomers of functional molecules under the excitation of two different wavelengths of light, and are widely used in advanced optical materials, biomedicine, energy storage, photoactuators, and photodynamic therapy. However, common photomolecular switches have the disadvantages of complex synthesis, difficult control, poor bidirectional photostability, and slow conversion rate, which seriously limit the promotion and application of photomolecular switches. In the past decade, photomolecular switches based on C=N double bonds have received extensive attention because they have the structural and property characteristics of widely used C=C and N=N double bond photomolecular switches. So far, photomolecular switches based on C=N double bonds such as imines and hydrazones have been developed, but they have defects such as low photoconversion rate, overlapping absorption wavelengths of isomers, slow conversion rate, and even unidirectional conversion, which cannot fully utilize the structural advantages of C=N double bonds. Therefore, it is of great theoretical significance and application value to design a more reasonable molecular structure to produce ideal photomolecular switch performance.

[0003] At present, the strategy of photomolecular switch based on hydrazone bond mainly enhances the stability of unstable isomers by introducing carbonyl groups into molecules to form hydrogen bonds, thereby achieving bidirectional stability of photomolecular switch. Alternatively, the stability of isomers is enhanced by introducing alkyl chains into molecules to form macrocyclic control. However, such strategies will reduce the conversion rate of bidirectional isomers while increasing stability, or even turn it into unidirectional conversion. For example, patent CN11510894A discloses a hydrazone-based bistable chiral optical switch material and its preparation and application, which is obtained by using a hydrazone molecular switch as a skeleton, introducing N,N-dimethyltoluidine as an electron donor at one end, modifying a benzene ring at the other end as an electron acceptor, and introducing a chiral center into the ester side chain. The material undergoes reversible photoconfiguration under irradiation with visible light of a wavelength of 440nm or 410nm and ultraviolet light of a wavelength of 340nm or 365nm, accompanied by luminescence quenching and recovery; wherein Z→E isomerization transformation is achieved under irradiation with visible light of a wavelength of 440nm or 410nm, and E→Z recovery occurs under irradiation with light of a wavelength of 340nm or 365nm, as shown in the figure However, in this patent, the photoisomerization quantum yield Φ Z→E =21.9±0.6%, photoisomerization quantum yield Φ E→Z =36.6±0.7%, and the conversion rate is relatively low. Therefore, developing a new, efficient, simple and feasible visible light regulation strategy is a key issue to be solved in the research field of hydrazone photomolecular switches. Summary of the invention

[0004] In view of the technical problem that common optical switch molecules in the prior art cannot take into account both high light conversion rate and high light conversion efficiency, the present invention proposes a photomolecular switch based on benzothiazole hydrazone and its preparation method and application. The prepared photomolecular switch isomer based on benzothiazole hydrazone has strong bidirectional stability and fast response bidirectional isomer conversion rate, and its preparation method is simple and has high yield.

[0005] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A benzothiazole hydrazone-based optical molecular switch, with benzothiazole and its derivatives as fluorescent groups, hydrazone bonds as bridges, and imidazolium ions as electron-withdrawing conjugated groups, with the following structural formula: X is any one of Br, CF3SO3, (CF3SO2)N, CF3CO2, C4F9SO3 or SbF6.

[0007] Furthermore, the preparation method of the benzothiazole hydrazone-based photomolecular switch comprises the following steps:

[0008] (1) Mix 3-methyl-2-benzothiazolone hydrazone hydrochloride and 1-methyl-1H-imidazole-2-carboxaldehyde, dissolve them in solvent I, heat and reflux, remove the solvent after the reaction is complete, and obtain a residue. The residue is separated by silica gel column chromatography or recrystallized to obtain intermediate I;

[0009] (2) dissolving the intermediate I obtained in step (1) in solvent II, adding sodium hydroxide and stirring at room temperature for reaction, and after the reaction is complete, post-treating to obtain intermediate II;

[0010] (3) mixing the intermediate II obtained in step (2) with benzyl bromide and dissolving them in solvent III, then heating to reflux and stirring to react to obtain a mixture, removing the solvent, washing the residue with ether three times, separating by silica gel column chromatography or recrystallizing to obtain a bromide-containing optical switch molecule III;

[0011] (4) reacting the photomolecular switch III obtained in step (2) with a metal salt in a solvent IV at room temperature in the dark, allowing the reaction to stand, removing the precipitate, and separating or recrystallizing the reaction product by silica gel column chromatography to obtain photomolecular switches containing different anions.

[0012] Further, the reaction equation of step (1) is:

[0013]

[0014] Furthermore, in the step (1), the molar ratio of 3-methyl-2-benzothiazolone hydrazone hydrochloride to 1-methyl-1H-imidazole-2-carbaldehyde is 1:(1-1.2), and the solvent I is acetonitrile or anhydrous ethanol.

[0015] Furthermore, in the step (1), the heating reflux temperature is 80-100° C., and the heating reflux time is 7-36 h.

[0016] Further, the reaction equation of step (2) is:

[0017]

[0018] Furthermore, in step (2), the molar ratio of intermediate I to sodium hydroxide is 1:1.2, the solvent II is methanol, and the reaction time is 10-36 hours under stirring at room temperature.

[0019] Furthermore, in step (3), the solvent III is acetonitrile, and the molar ratio of the intermediate II to benzyl bromide is 1:1.

[0020] Further, the reaction equation of step (3) is:

[0021]

[0022] Furthermore, in the step (3), the temperature of the reflux stirring reaction is 80-120° C., the reflux stirring time is 36 hours, and the column chromatography reagent is a mixed solution of dichloromethane and methanol in a volume ratio of 30:1.

[0023] Further, the reaction equation of step (4) is: (taking (CF3SO2)N salt (abbreviated as NTf) and SbF6 salt as examples, the reaction equation is listed, and other photomolecular switches replace different anions in the metal salt (CF3SO3 - CF3CO2 - or C4F9SO3 - ) can be formed)

[0024]

[0025] Furthermore, in step (4), the metal salt is any one of Li or Ag CF3SO3 salt (4a), (CF3SO2)N salt (abbreviated as NTf) (4b), CF3CO2 salt (4c), C4F9SO3 salt (4d) or SbF6 salt (4e), the molar ratio of the bromide-containing optical switch molecule III (4) to the metal salt is 1:1, and the solution IV is dichloromethane. Furthermore, the reaction time in step (4) at room temperature and in the dark is 36 hours.

[0026] Furthermore, the reaction equation of the photomolecular switch based on benzothiazole hydrazone is as follows: (taking (CF3SO2)N salt (abbreviated as NTf) and SbF6 salt as examples, the reaction equation is listed. Other photomolecular switches replace different anions in metal salts (CF3SO3 - CF3CO2- or C4F9SO3 - ) can be formed)

[0027]

[0028] Furthermore, the benzothiazole hydrazone-based optical molecular switch is applied in the field of intelligent fluorescent switch materials.

[0029] The present invention has the following beneficial effects:

[0030] 1. The present invention reacts benzothiazole hydrazone with imidazole formaldehyde to generate a new compound that connects benzothiazole and imidazole rings with a hydrazone bond as a bridge, and then obtains a light switch molecule with photochromic and fluorescence changes in solution, solid and film states through addition reaction and ion exchange reaction. The designed light switch molecule undergoes E→Z isomerization under 460nm light excitation and Z→E isomerization under 365nm light excitation to obtain a photothermally stable Z / E isomer, which has the characteristics of large wavelength difference of Z / E isomer absorption spectrum, high Z / E isomerization conversion rate, fast Z / E isomerization photoconversion rate and simple preparation, solving the problem that common light switch molecules cannot take into account both high light conversion rate and high light conversion rate. The design strategy of the present invention provides a new method for designing an ideal light molecular switch.

[0031] 2. The benzothiazole hydrazone-based optical molecular switch prepared by the present invention can be adjusted by adjusting the different anions (such as Br - CF3SO3 - 、(CF3SO2)N - CF3CO2 - 、C4F9SO3 - or SbF6 - ) regulates the conversion rate of photoinduced E / Z conversion and the fluorescence properties at the same time. And through research, it is found that the size of the substituent and the structure of the anion can effectively regulate the photoinduced E / Z configuration conversion.

[0032] 3. The present invention provides a simple and easy E / Z configuration conversion strategy with a high conversion rate, which is used for new stimulus-responsive aggregation-induced luminescence materials and can be applied in the fields of light capture, molecular robots, nanoactuators, fluorescence sensing, anti-counterfeiting, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 This is the H NMR spectrum of the intermediate I prepared in Example 1 of the present invention, wherein the solvent is DMSO-d6.

[0035] Figure 2 This is the NMR carbon spectrum of intermediate I prepared in Example 1 of the present invention, wherein the solvent is DMSO-d6.

[0036] Figure 3 This is the H NMR spectrum of the intermediate II prepared in Example 1 of the present invention, wherein the solvent is CDCl3.

[0037] Figure 4 This is the NMR carbon spectrum of intermediate II prepared in Example 1 of the present invention, wherein the solvent is CDCl3.

[0038] Figure 5 This is the H NMR spectrum of the bromide-containing photoswitch molecule III prepared in Example 1 of the present invention, wherein the solvent is DMSO-d6.

[0039] Figure 6 This is the NMR carbon spectrum of the bromide-containing photoswitch molecule III prepared in Example 1 of the present invention, wherein the solvent is DMSO-d6.

[0040] Figure 7 This is the mass spectrum of the bromide-containing optical switch molecule III prepared in Example 1 of the present invention.

[0041] Figure 8 The benzothiazole hydrazone-based photomolecular switch (NTf - ), where the solvent is DMSO-d6.

[0042] Fig. 9 The benzothiazole hydrazone-based photomolecular switch (NTf - ), where the solvent is DMSO-d6.

[0043] Fig.10 The benzothiazole hydrazone-based photomolecular switch (NTf - ), where the solvent is DMSO-d6.

[0044] Fig.11 The benzothiazole hydrazone-based photomolecular switch (SbF6 - ), where the solvent is DMSO-d6.

[0045] Fig.12 The benzothiazole hydrazone-based photomolecular switch (SbF6 -), where the solvent is DMSO-d6.

[0046] Fig.13 The Z / E ratio diagrams and Z / E conversion stability of hydrazone imidazolium salt optical molecular switches with different anions under light (460nm), among which (a) is the Z / E ratio diagram of CF3SO3(4a), (b) is the Z / E ratio diagram of (CF3SO2)N(4b), (c) is the Z / E ratio diagram of CF3CO2(4c), (d) is the Z / E ratio diagram of C4F9SO3(4d), and (e) is the Z / E ratio diagram of SbF6(4e); (f) is the change in the absorption spectrum of isomers during the reversible photoswitching process of Br(4).

[0047] Fig.14 The fluorescence emission spectra of hydrazone imidazolium salt optical molecular switches 4, 4a, 4b, and 4e with different anions under 365nm light excitation (a) and the emission spectra of their E / Z isomers under 365nm light excitation (b).

[0048] Fig.15 The bromide-containing optical switch molecule III (Br - )(4-E, 4-Z), photomolecular switch based on benzothiazole hydrazone (N(CF3SO2N)2 - )(4b-E), photomolecular switch based on benzothiazole hydrazone (SbF6 - )(4e-E)’s single crystal structure diagram. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] The reagents and materials used in the embodiments of the present invention were purchased from Beijing Inokai Reagent Co., Ltd.

[0051] Example 1

[0052] A photomolecular switch based on benzothiazole hydrazone (NTf - ) (i.e., the preparation method of 4b), the steps are as follows:

[0053] (1) Preparation of Intermediate I

[0054]

[0055] 3-Methyl-2-benzothiazolone hydrazone hydrochloride hydrate (1.078g, 5mmol), 1-methyl-1H-imidazole-2-carboxaldehyde (0.550g, 5mmol) were added to a pressure bottle, a magnetic stirrer was added, 20mL of anhydrous ethanol was added and stirred thoroughly to dissolve the raw materials, and refluxed at 90°C for 7h. The reaction was monitored by TLC. After the reaction was complete, the entire reaction system was cooled to room temperature, the reaction solution was filtered with a glass suction funnel, and the filter cake was washed with ether. The filter cake was vacuum dried to obtain 1.327g of yellow powder crude product, with a yield of 86.2%. The crude product was recrystallized with a mixed solution of anhydrous ethanol and methanol to obtain 1.235g of yellow crystals, with a yield of 80%.

[0056] Melting point Mp = 261 ° C. The H NMR spectrum of intermediate I is as follows Figure 1 As shown, 1 HNMR(400MHz,DMSO-d6)δ8.44(s,1H),7.79(d,J=1.6Hz,1H),7.75(d,J=7.26H z,1H),7.72(d,J=1.6Hz,1H),7.41-7.48(m,2H),4.04(s,3H),3.68(s,3H)ppm.

[0057] The NMR carbon spectrum of intermediate I is as follows Figure 2 As shown, 13 C NMR (100MHz, DMSO-d6): δ170.84,140.49,139.45,126.95,125.64,123.4,122.92,122.62,111.35,36.22and 31.45ppm.

[0058] MALDI TOF-MS, C 13 H 14 N5S[M] + : Calculated value 272.0964, found value 272.0967.

[0059] (2) Preparation of Intermediate II

[0060]

[0061] Weigh intermediate I (0.561 g, 1.8 mmol) and dissolve it in 30 mL methanol, add sodium hydroxide (0.087 g, 2.2 mmol), stir at room temperature for 12 h, wait for the reaction to be complete, and spin-dry the obtained reaction solvent under vacuum. Add 50 mL chloroform to dissolve the powder, wash with ultrapure water and remove the inorganic salt in the organic phase, collect the organic phase, add anhydrous sodium sulfate to dry and filter out the desiccant. The filtrate is concentrated with a rotary evaporator and vacuum dried to obtain 0.431 g of white powder with a yield of 87%.

[0062] Melting point Mp = 151 ° C. The NMR carbon spectrum of intermediate II is as follows Figure 3 As shown, 1 H NMR (400MHz, CDCl3): δ8.74(s,1H),7.7(d,J=6.8Hz,1H),7.58-7.60(d,J=8Hz,1H),7.43(s,H),7.30-7.39(m,2H),4.34(s,3H),3.91(s,3H),and 3.95(s,3H)ppm.

[0063] The NMR carbon spectrum of intermediate II is as follows Figure 4 As shown, 13 C NMR (100MHz, CDCl3): δ143.40, 140.72, 129.32, 124.27, 121.28, 118.65, 118.56, 113.22, and 35.69ppm.

[0064] MALDI TOF-MS:m / z[M+H] + Calculated value: C 13 H 16 N5S 272.0964, found value: 272.0972.

[0065] (3) Preparation of bromide-containing optical switch molecule III (i.e. 4)

[0066]

[0067] In a 100 mL pressure bottle, intermediate II (0.400 g, 1.47 mmol) and benzyl bromide (0.251 g, 1.47 mmol) were mixed with 40 mL of acetonitrile and stirred at 100 ° C for 36 h to obtain a yellow solution. After the crude product was cooled to remove the solvent, it was washed with ether three times (3×15 mL) and subjected to column chromatography (SiO2, CH2Cl2:CH3OH=30:1) to obtain 0.533 g of yellow powder with a yield of about 82%.

[0068] Melting point Mp = 244 ° C. The H NMR spectrum of the bromide-containing optical switch molecule III is as follows: Figure 5 As shown, 1 H NMR (400MHz, DMSO-d6) δ8.63(s,1H),7.91(s,2H),7.73(d,J=7.6Hz,1H),7.50(d,J=7.9Hz,1H),7.43(dd ,J=14.1,7.2Hz,3H),7.35(dd,J=12.6,6.9Hz,3H),7.23(t,J=7.5Hz,1H),5.80(s,2H),4.07(s,3H),and 3.68(s,3H).

[0069] The NMR carbon spectrum of the bromide-containing optical switch molecule III (i.e. 4) is as follows Figure 6 As shown, 13 C NMR(100MHz,DMSO-d6)δ172.05,140.22,139.24,134.61,129.80,128.83,128.49,1 27.88,127.00,124.34,123.29,123.17,122.73,122.72,111.55,51.87,36.22,and 31.47ppm.

[0070] The mass spectrum of the bromide-containing optical switch molecule III (i.e., 4) is shown below: Figure 7 As shown, MALDI TOF-MS: m / z [M-Br+H] + calcd.C 20 H 20 N5S 362.1434, found 362.1421.

[0071] (4) Photomolecular switch based on benzothiazole hydrazone (NTf - Preparation of ) (i.e. 4b)

[0072]

[0073] In a glove box, intermediate III (i.e., 4) (0.200 g, 0.45 mmol) was weighed and added to a pressure bottle together with LiNTf (0.116 g, 0.45 mmol), and a magnetic stirrer was added. 50 mL of dichloromethane was added under a nitrogen atmosphere, and the mixture was stirred at room temperature for 1 day in a dark environment. The reaction solution was filtered through a glass suction funnel, and the filter cake was washed with dichloromethane. The filtrate was collected and concentrated to obtain 0.170 g of yellow powder with a yield of about 74%.

[0074] Melting point Mp = 158 ° C. Photomolecular switch based on benzothiazole hydrazone (NTf- The H NMR spectrum of ) (i.e. 4b) is as follows Figure 8 As shown, 1 H NMR (400MHz, DMSO-d6) δ8.62(s,1H),7.90(s,2H),7.72(d,J=7.8Hz,1H),7.48(d,J=8.1Hz,1H) ,7.45–7.39(m,3H),7.35(t,J=9.6Hz,3H),7.22(t,J=7.5Hz,1H),5.79(s,2H),4.06(s,3H),and 3.68(s,3H)ppm.

[0075] Photomolecular switch based on benzothiazole hydrazone (NTf - The NMR carbon spectrum of ) (i.e. 4b) is as follows Fig. 9 As shown, 13 C NMR(100MHz,DMSO-d6)δ171.64,140.44,138.08,134.98,134.51,128.98,128.43,1 27.41,127.06,125.40,123.45,123.23,123.18,122.66,111.60,51.33,37.36,and 31.58ppm.

[0076] Photomolecular switch based on benzothiazole hydrazone (NTf - The NMR fluorine spectrum of ) (i.e. 4b) is as follows Fig.10 As shown, 9 FNMR (376MHz, DMSO d6) δ-78.70.

[0077] MALDI TOF-MS for C 20 H 20 N5S[M-NTf] + :calcd 362.1434, found 362.1431.

[0078] Example 2

[0079] A photomolecular switch based on benzothiazole hydrazone (SbF6 - ) (i.e., the preparation method of 4e), the steps are as follows:

[0080] (1) Preparation of Intermediate I

[0081] 3-Methyl-2-benzothiazolone hydrazone hydrochloride hydrate (1.078g, 5mmol), 1-methyl-1H-imidazole-2-carboxaldehyde (0.550g, 5mmol) were added to a pressure bottle, a magnetic stirrer was added, 20mL of anhydrous ethanol was added and stirred thoroughly to dissolve the raw materials, and refluxed at 90°C for 7h. The reaction was monitored by TLC. After the reaction was complete, the entire reaction system was cooled to room temperature, the reaction solution was filtered with a glass suction funnel, and the filter cake was washed with ether. The filter cake was vacuum dried to obtain 1.327g of yellow powder crude product, with a yield of 86.2%. The crude product was recrystallized with a mixed solution of anhydrous ethanol and methanol to obtain 1.235g of yellow crystals, with a yield of 80%.

[0082] (2) Preparation of Intermediate II

[0083] Weigh intermediate I (0.561g, 1.8mmol) and dissolve in 30mL methanol, add sodium hydroxide (0.087g, 2.2mmol), stir at room temperature for 12h, wait for the reaction to be complete, and spin-dry the obtained reaction solvent under vacuum. Add 50mL chloroform to dissolve the powder, wash with ultrapure water and remove the inorganic salt in the organic phase, collect the organic phase, add anhydrous sodium sulfate drying and filter out the desiccant. The filtrate is concentrated with a rotary evaporator and vacuum dried to obtain 0.431g of white powder, with a yield of 87%.

[0084] (3) Preparation of bromide-containing optical switch molecule III (i.e. 4)

[0085] In a 100 mL pressure bottle, intermediate II (0.400 g, 1.47 mmol) and benzyl bromide (0.251 g, 1.47 mmol) were mixed with 40 mL of acetonitrile and stirred at 100 ° C for 36 h to obtain a yellow solution. After the crude product was cooled to remove the solvent, it was washed with ether three times (3×15 mL) and subjected to column chromatography (SiO2, CH2Cl2:CH3OH=30:1) to obtain 0.533 g of yellow powder with a yield of about 82%.

[0086] (4) Photomolecular switch based on benzothiazole hydrazone (SbF6 - Preparation of )(i.e. 4e)

[0087]

[0088] In a glove box, intermediate III (i.e., 4) (0.200 g, 0.45 mmol) was weighed and added to a pressure bottle together with AgSbF6 (0.155 g, 0.45 mmol), and a magnetic stirrer was added. 50 mL of dichloromethane was added under a nitrogen atmosphere, and the mixture was stirred at room temperature for 1 day in a dark environment. The reaction solution was filtered through a glass suction funnel, and the filter cake was washed with dichloromethane. The filtrate was collected and concentrated to obtain 0.108 g of yellow powder (i.e., 4e), with a yield of about 83%.

[0089] Melting point Mp = 218 ° C. Photomolecular switch based on benzothiazole hydrazone (SbF6 - The H NMR spectrum of ) (i.e. 4e) is as follows Fig.11 As shown, 1 H NMR(400MHz,DMSO-d6)δ8.62(s,1H),7.89(s,2H),7.72(d,J=7.8Hz,1H),7.51- 7.31(m,8H),7.21(t,J=7.5Hz,1H),5.79(s,2H),4.06(s,3H),3.68(s,3H)ppm.

[0090] Photomolecular switch based on benzothiazole hydrazone (SbF6 - The NMR carbon spectrum of ) (i.e. 4e) is as follows Fig.12 As shown, 13 C NMR(100MHz,DMSO-d6)δ172.1,140.9,138.5,135.4,134.9,129.4,128.9,12 7.8,127.5,125.8,123.9,123.7,123.6,123.1,112.1,51.8,37.8,32.1ppm.

[0091] MALDI TOF-MS for C 20 H 20 N5S[M-SbF6] + :calcd 362.1434, found 362.1425.

[0092] Example 3

[0093] A preparation method of a benzothiazole hydrazone-based photomolecular switch (CF3SO3) (ie, 4a), comprising the following steps:

[0094] (1) Preparation of Intermediate I

[0095] Add 3-methyl-2-benzothiazolone hydrazone hydrochloride hydrate (1.078g, 5mmol), 1-methyl-1H-imidazole-2-carboxaldehyde (4mmol) to a pressure bottle, add a magnetic stirrer, add 20mL of acetonitrile and stir well to dissolve the raw materials, and reflux for 5h under heating at 90°C. Monitor the reaction by TLC. After the reaction is complete, cool the entire reaction system to room temperature, filter the reaction solution with a glass suction funnel, wash the filter cake with ether, and vacuum dry the filter cake to obtain a yellow powder crude product. The crude product is recrystallized with a mixed solution of anhydrous ethanol and methanol to obtain yellow crystals.

[0096] (2) Preparation of Intermediate II

[0097] Weigh intermediate I (0.561g, 1.8mmol) and dissolve in 30mL methanol, add sodium hydroxide (0.087g, 2.2mmol), stir at room temperature for 10h, wait for the reaction to be complete, and spin-dry the obtained reaction solvent under vacuum. Add 50mL chloroform to dissolve the powder, wash with ultrapure water and remove the inorganic salt in the organic phase, collect the organic phase, add anhydrous sodium sulfate drying and filter out the desiccant. The filtrate is concentrated with a rotary evaporator and vacuum dried to obtain 0.431g of white powder, with a yield of 87%.

[0098] (3) Preparation of bromide-containing optical switch molecule III (i.e. 4)

[0099] In a 100 mL pressure bottle, intermediate II (0.400 g, 1.47 mmol) and benzyl bromide (0.251 g, 1.47 mmol) were mixed with 40 mL of acetonitrile and stirred at 80 ° C for 36 h to obtain a yellow solution. The crude product was cooled to remove the solvent, washed with ether three times (3×15 mL), and subjected to column chromatography (SiO2, CH2Cl2:CH3OH=30:1) to obtain 0.533 g of yellow powder with a yield of about 82%.

[0100] (4) Preparation of photomolecular switch based on benzothiazole hydrazone (CF3SO3) (i.e. 4a)

[0101]

[0102] In a glove box, intermediate III (i.e., 4) (0.200 g, 0.45 mmol) was weighed and added to a pressure bottle together with CF3SO3Li (0.45 mmol), and a magnetic stirrer was added. 50 mL of dichloromethane was added under a nitrogen atmosphere, and the mixture was stirred at room temperature for 1 day in a dark environment. The reaction solution was filtered through a glass suction funnel, and the filter cake was washed with dichloromethane. The filtrate was collected and concentrated to obtain a solid powder (i.e., 4a).

[0103] Example 4

[0104] A preparation method of a benzothiazole hydrazone-based photomolecular switch (CF3CO2) (ie, 4c), comprising the following steps:

[0105] (1) Preparation of Intermediate I

[0106] Add 3-methyl-2-benzothiazolone hydrazone hydrochloride hydrate (1.078g, 5mmol), 1-methyl-1H-imidazole-2-carboxaldehyde (5.4mmol) to a pressure bottle, add a magnetic stirrer, add 20mL of acetonitrile and stir thoroughly to dissolve the raw materials, and reflux for 18h under heating conditions at 100°C. Monitor the reaction using TLC. After the reaction is complete, cool the entire reaction system to room temperature, filter the reaction solution with a glass suction funnel, wash the filter cake with ether, and vacuum dry the filter cake to obtain a yellow powder crude product. The crude product is recrystallized with a mixed solution of anhydrous ethanol and methanol to obtain yellow crystals.

[0107] (2) Preparation of Intermediate II

[0108] Weigh intermediate I (0.561g, 1.8mmol) and dissolve in 30mL methanol, add sodium hydroxide (0.087g, 2.2mmol), stir at room temperature for 15h, wait for the reaction to be complete, and spin-dry the obtained reaction solvent under vacuum. Add 50mL chloroform to dissolve the powder, wash with ultrapure water and remove the inorganic salt in the organic phase, collect the organic phase, add anhydrous sodium sulfate drying and filter out the desiccant. The filtrate is concentrated with a rotary evaporator and vacuum dried to obtain 0.431g of white powder, with a yield of 87%.

[0109] (3) Preparation of bromide-containing optical switch molecule III (i.e. 4)

[0110] In a 100 mL pressure bottle, intermediate II (0.400 g, 1.47 mmol) and benzyl bromide (0.251 g, 1.47 mmol) were mixed with 40 mL of acetonitrile and stirred at 90 ° C for 36 h to obtain a yellow solution. The crude product was cooled to remove the solvent, washed with ether three times (3×15 mL), and subjected to column chromatography (SiO2, CH2Cl2:CH3OH=30:1) to obtain 0.533 g of yellow powder with a yield of about 82%.

[0111] (4) Preparation of photomolecular switch based on benzothiazole hydrazone (CF3CO2) (i.e. 4c)

[0112]

[0113] In a glove box, intermediate III (0.200 g, 0.45 mmol) was weighed and added to a pressure bottle together with AgCF3CO2 (0.45 mmol), and a magnetic stirrer was added. 50 mL of dichloromethane was added under a nitrogen atmosphere, and stirred at room temperature for 1 day in a dark environment. The reaction solution was filtered through a glass suction funnel, and the filter cake was washed with dichloromethane. The filtrate was collected and concentrated to obtain a solid powder (i.e., 4c).

[0114] Example 5

[0115] A preparation method of a benzothiazole hydrazone-based photomolecular switch (C4F9SO3) (ie, 4d), comprising the following steps:

[0116] (1) Preparation of Intermediate I

[0117] Add 3-methyl-2-benzothiazolone hydrazone hydrochloride hydrate (1.078g, 5mmol), 1-methyl-1H-imidazole-2-carboxaldehyde (6mmol) to a pressure bottle, add a magnetic stirrer, add 20mL of anhydrous ethanol and stir thoroughly to dissolve the raw materials, and reflux for 36h under heating conditions at 80°C. Monitor the reaction using TLC. After the reaction is complete, cool the entire reaction system to room temperature, filter the reaction solution with a glass suction funnel, wash the filter cake with ether, and vacuum dry the filter cake to obtain a yellow powder crude product. The crude product is recrystallized with a mixed solution of anhydrous ethanol and methanol to obtain yellow crystals.

[0118] (2) Preparation of Intermediate II

[0119] Weigh intermediate I (0.561g, 1.8mmol) and dissolve in 30mL methanol, add sodium hydroxide (0.087g, 2.2mmol), stir at room temperature for 36h, wait for the reaction to be complete, and spin-dry the obtained reaction solvent under vacuum. Add 50mL chloroform to dissolve the powder, wash with ultrapure water and remove the inorganic salt in the organic phase, collect the organic phase, add anhydrous sodium sulfate drying and filter out the desiccant. The filtrate is concentrated with a rotary evaporator and vacuum dried to obtain 0.431g of white powder, with a yield of 87%.

[0120] (3) Preparation of bromide-containing optical switch molecule III (i.e. 4)

[0121] In a 100 mL pressure bottle, intermediate II (0.400 g, 1.47 mmol) and benzyl bromide (0.251 g, 1.47 mmol) were mixed with 40 mL of acetonitrile and stirred at 120°C for 36 h to obtain a yellow solution. The crude product was cooled to remove the solvent, washed with ether three times (3×15 mL), and subjected to column chromatography (SiO2, CH2Cl2:CH3OH=30:1) to obtain 0.533 g of yellow powder (ie, 4), with a yield of about 82%.

[0122] (4) Preparation of benzothiazole hydrazone-based photomolecular switch (C4F9SO3) (i.e. 4d)

[0123]

[0124] In a glove box, intermediate III (0.200 g, 0.45 mmol) was weighed and added to a pressure bottle together with C4F9SO3Li (0.45 mmol), and a magnetic stirrer was added. 50 mL of dichloromethane was added under a nitrogen atmosphere, and the mixture was stirred at room temperature for 1 day in a dark environment. The reaction solution was filtered through a glass suction funnel, and the filter cake was washed with dichloromethane. The filtrate was collected and concentrated to obtain a solid powder (i.e., 4d).

[0125] Application Example 1

[0126] The preparation steps of the benzothiazole hydrazone-based photomolecular switch solution are as follows:

[0127] (1) Preparation of hydrazone imidazolium salt photomolecular switch solution

[0128] Weigh an appropriate amount of hydrazone imidazolium salt optical molecular switch and prepare it with DMSO-d6 to a concentration of 1×10 -5 The solution of M should be stored at room temperature and away from light.

[0129] (2) Fluorescence spectrum test method

[0130] Use a pipette to transfer 3 mL of hydrazone imidazole salt photomolecular switch solution into a 1 cm cuvette. Mix thoroughly and let stand for 2 minutes before testing. The excitation wavelength of all test objects is set to 365-460 nm. Use a Cary Eclipse absolute quantum efficiency tester for testing.

[0131] (3) Ultraviolet spectrum test method

[0132] Use a pipette to transfer 3 mL of hydrazone imidazole salt photomolecular switch solution into a 1 cm cuvette. Mix thoroughly and let stand for 2 min before testing. Use a TU1901 UV-visible spectrophotometer for detection.

[0133] (5) Structural characterization

[0134] The hydrogen spectrum was detected by 400MHz Varian NMR, and the chemical shift was obtained by comparing with TMS. The mass spectrum was detected by LC-MSD-Trap-SL system, and the elemental analysis was detected by Flash EA 1112 elemental analyzer.

[0135] Effect Example 1

[0136] 1. Structural analysis of Example 1

[0137] 3-Methyl-2-benzothiazolone hydrazone hydrochloride hydrate reacts with 1-methyl-1H-imidazole-2-carboxaldehyde to obtain intermediate I, intermediate I reacts with sodium hydroxide to obtain intermediate II, intermediate II reacts with benzyl bromide to obtain hydrazone imidazole salt optical molecular switch (Br - ), the synthesis technology route is:

[0138]

[0139] pass 1 H NMR, 13 C NMR, mass spectrometry, and elemental analysis confirmed its structure.

[0140] 2. Effects of different anions on the conversion rate, response rate and fluorescence spectrum of hydrazone imidazolium salt optical molecular switches

[0141] As shown in the following table and Fig.13 Through experimental characterization, different anions can undergo reversible photoinduced E / Z isomerization, but the conversion rate is different. As can be seen from the table, after replacing different anions, the rate of photoinduced E / Z conversion is different. When the anion is SbF6 - , the fastest response rate.

[0142] Table 1 Effects of different anions on the conversion rate, response rate and fluorescence spectrum of hydrazone imidazolium salt optical molecular switches

[0143]

[0144] Note: The cation is (C 20 H 20 N5S) + , named according to the different anions, Br - (4) CF3SO3 - (4a), (CF3SO2)2N - (NTf - )(4b), CF3COO - (4c), C4F9SO3 - (4d) and SbF6 - (4e).

[0145] Fig.13 The Z / E ratio diagram of hydrazone imidazolium salt photomolecular switches with different anions under light (460nm) and the stability of Z / E conversion, where (a) is CF3SO3 - (4a) and (4b) are (CF3SO2)2N - (4b) and (4c) are CF3COO - (4c) and (4d) are C4F9SO3 - (4d) and (e) are SbF6 - (4e) is the absorption intensity ratio of the Z / E isomer; (f) is the absorption intensity ratio of Br - The change of the absorption spectrum of (4) during the reversible isomerization process. Fig.13 It can be seen that the oblique straight line is the photoconversion rate of E / Z isomers. The larger the slope, the greater the conversion rate. - , the fastest response rate.

[0146] Fig.14 The fluorescence emission spectra of hydrazone imidazolate optical molecular switches 4, 4a, 4b, and 4e with different anions under 365 nm light excitation (a) (photography was completed within 0.1 s to reduce the influence of cis-trans isomerism under light irradiation) and the emission spectra of their E / Z isomers under 365 nm light excitation (b). Fig.14 As shown in the figure, it can be seen from the fluorescence picture and fluorescence spectrum that the maximum emission wavelength is between 511nm-527nm, the fluorescence emission color is green, and the common feature of different anion compounds is that the fluorescence quantum efficiency of the E-configuration is higher than that of the Z-configuration. The fluorescence properties of compounds with different anions are also different. We can obtain the desired fluorescent material through a simple ion exchange reaction.

[0147] The prepared anions are Br - (4) N(CF3SO2N)2 - (4b) and SbF6 - (4e) Crystal data were used for identification, and the results are shown in Table 2.

[0148] Table 2 Crystal data and structure optimization table

[0149]

[0150] Fig.15 The bromide-containing optical switch molecule III (Br - )(4-E, 4-Z), photomolecular switch based on benzothiazole hydrazone (N(CF3SO2N)2 - )(4b-E), photomolecular switch based on benzothiazole hydrazone (SbF6 -)(4e-E)’s single crystal structure diagram.

[0151] The benzothiazole hydrazone-based photomolecular switch involved in the present invention has a simple structure, is easy to synthesize, works reliably, and has good use effects. The conversion rate of the photoinduced E / Z conversion is regulated by adjusting the different anions corresponding to the compound, and the fluorescence properties are regulated at the same time. Studies have found that the size of the substituents, the structure of the anions, etc. can effectively regulate the photoinduced E / Z configuration conversion. This work provides a simple and easy E / Z configuration conversion strategy with a high conversion rate, which provides a new idea for the design of new intelligent fluorescent switch materials.

[0152] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A photomolecular switch based on benzothiazole hydrazone, characterized in that: The benzothiazole hydrazone-based optical molecular switch uses benzothiazole and its derivatives as fluorescent groups, a hydrazone bond as a bridge, and an imidazolium ion as an electron-withdrawing conjugated group. The structural formula is as follows: , X is any one of Br, CF3SO3, (CF3SO2)N, CF3CO2, C4F9SO3 or SbF6.

2. The method for preparing the benzothiazole hydrazone-based photomolecular switch according to claim 1, characterized in that: Here are the steps: (1) Mix 3-methyl-2-benzothiazolone hydrazone hydrochloride and 1-methyl-1H-imidazole-2-carboxaldehyde, dissolve them in solvent I, heat and reflux, remove the solvent after the reaction is complete, and obtain a residue. The residue is separated by silica gel column chromatography or recrystallized to obtain intermediate I; (2) dissolving the intermediate I obtained in step (1) in solvent II, adding sodium hydroxide and stirring at room temperature for reaction, and after the reaction is complete, post-treating to obtain intermediate II; (3) The intermediate II obtained in step (2) is mixed with benzyl bromide and dissolved in solvent III, and then heated to reflux and stirred for reaction to obtain a mixture, and the solvent is removed. The residue is washed three times with ether, and separated by silica gel column chromatography or recrystallized to obtain a bromide-containing optical switch molecule III; (4) reacting the photomolecular switch III obtained in step (3) with a metal salt in a solvent IV at room temperature in the dark, allowing the reaction to stand, removing the precipitate, and separating the precipitate by silica gel column chromatography or recrystallization to obtain photomolecular switches containing different anions.

3. The method for preparing a benzothiazole hydrazone-based photomolecular switch according to claim 2, characterized in that: In the step (1), the molar ratio of 3-methyl-2-benzothiazolone hydrazone hydrochloride to 1-methyl-1H-imidazole-2-carbaldehyde is 1:(0.8-1.2), and the solvent I is acetonitrile or anhydrous ethanol.

4. The method for preparing a benzothiazole hydrazone-based photomolecular switch according to claim 2 or 3, characterized in that: The heating reflux temperature in step (1) is 80-100° C., and the heating reflux time is 5-36 h.

5. The method for preparing a benzothiazolehydrazone-based photomolecular switch according to claim 2, characterized in that: In the step (2), the molar ratio of intermediate I to sodium hydroxide is 1:1.2, the solvent II is methanol, and the reaction time is 10-36 hours under stirring at room temperature.

6. The method for preparing a benzothiazolehydrazone-based photomolecular switch according to claim 5, characterized in that: In the step (3), the solvent III is acetonitrile, and the molar ratio of the intermediate II to benzyl bromide is 1:

1.

7. The method for preparing a benzothiazolehydrazone-based photomolecular switch according to claim 6, characterized in that: The temperature of the reflux stirring reaction in step (3) is 80-120° C., the reflux stirring time is 36 h, and the column chromatography reagent is a mixed solution of dichloromethane and methanol in a volume ratio of 30:

1.

8. The method for preparing a benzothiazolehydrazone-based photomolecular switch according to claim 7, characterized in that: In step (4), the metal salt is any one of Li or Ag in CF3SO3 salt, (CF3SO2)N salt, CF3CO2 salt, C4F9SO3 salt or SbF6 salt, the molar ratio of the bromide ion-containing optical switch molecule III to the metal salt is 1:1, and the solution IV is dichloromethane.

9. The method for preparing a benzothiazole hydrazone-based photomolecular switch according to any one of claims 2 to 3 or 5 to 8, characterized in that: The reaction time in step (4) at room temperature and in the dark is 36 h.

10. Application of the benzothiazolehydrazone-based photomolecular switch according to claim 1 in the field of intelligent fluorescent switch materials.

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