阅读说明：本技术 一种苯并噻唑-苯乙氰类化合物及其制备方法和应用 (Benzothiazole-phenethyl cyanide compound and preparation method and application thereof ) 是由 谷标 唐斯萍 刘梦琴 易英杰 于 2019-10-08 设计创作，主要内容包括：本发明提供了一种苯并噻唑-苯乙氰类化合物,分子式如下。该化合物兼具激发态分子内质子转移和聚集诱导发光性质。本发明还提供该化合物的制备方法,该方法合成简单,仅需一步反应,反应条件温和,产率较高,达到80％以上,斯托克斯位移大,可达330nm,发射波长635nm在近红外区域等特点。该化合物可以应用于荧光检测领域。<Image he="295" wi="647" file="DDA0002225774710000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(The invention provides a benzothiazole-phenethyl cyanide compound with a molecular formula as follows. The compound has both excited intramolecular proton transfer and aggregation induced light emitting properties. The invention also provides a preparation method of the compound, which has the characteristics of simple synthesis, only one-step reaction, mild reaction conditions, high yield of more than 80%, large Stokes shift of 330nm, emission wavelength of 635nm in a near-infrared region and the like. The compound can be applied to the field of fluorescence detection.)

1. A benzothiazole-phenethyl cyanide compound, the molecular formula is:

2. a process for the preparation of benzothiazole-benzonitrile compounds as claimed in claim 1, comprising the steps of:

(1) adding 4-cyanobenzene acetonitrile, a catalyst and acetonitrile into BA serving as a raw material, and uniformly mixing to obtain a mixed solution; the formula proportion of the mixed solution is as follows:

wherein the molecular formula of BA is:

the catalyst is selected from one or more of triethylamine, pyrrolidine and 4-methylpiperidine;

(2) stirring the mixed solution at 30-82 ℃ for reaction for 1-12 hours;

(3) after the reaction is finished, a brown precipitate is separated out; the precipitate was filtered and washed 2-3 times with acetonitrile to give pure BA-CN.

3. The method for preparing benzothiazole-benzonitrile compound according to claim 2, wherein the formula ratio of the mixed solution in step (1) is:

4. the process for preparing benzothiazole-benzonitrile compound, according to claim 2, wherein the step (2) is performed by stirring at 50 to 82 ℃ for 5 to 10 hours.

5. The use of benzothiazole-benzonitrile compounds as in claim 1 in fluorescent detection reagents.

Technical Field

The invention relates to the technical field of preparation of organic functional materials, and relates to a benzothiazole-phenethyl cyanide compound, and a preparation method and application thereof.

Background

The discovery of an aggregation-induced emission (AIE) compound effectively overcomes the concentration-induced quenching effect brought by the traditional fluorescent molecules and also brings opportunities for the application and development of fluorescent materials. In the fields of chemical/biological detection and biological imaging, the AIE compounds have advantages over other compounds: (1) has high aggregation state luminous efficiency, and can improve organismThe sensitivity of the detection; (2) the cell permeability and the cell compatibility are good, and the cell imaging application is facilitated; (3) has excellent photobleaching resistance and is suitable for long-term tracing of target substances in cells. As many research groups explore the AIE phenomenon, more and more AIE compounds are synthesized, but the number of AIE compounds that can be used for biosensing and imaging remains quite limited. Because conventional AIE compounds still suffer from certain deficiencies: (1) most AIE molecules have small Stokes shift, and have the problem of serious overlapping of absorption spectrum and emission spectrum, which can greatly reduce the sensitivity; (2) the AIE compounds reported so far have emission wavelengths mainly concentrated in the ultraviolet and visible region (lambda)_emLess than or equal to 600nm), has the defects of poor tissue penetrability, light absorption and autofluorescence interference of biological samples, low signal-to-noise ratio and the like in the using process, and seriously restricts the detection of in-vivo analytes and the imaging analysis of living tissues by AIE compounds. In contrast, light with an emission wavelength in the near infrared region can effectively reduce light scattering of dense media (such as cells, tissues and living bodies), achieves a deeper tissue penetration depth, and is suitable for imaging analysis of cells and living bodies. Meanwhile, the near infrared light can excite the biological sample to generate autofluorescence to a small extent, reduce background signal interference, improve the signal-to-noise ratio of fluorescence imaging, and have obvious advantages in biological sample analysis. Therefore, how to obtain near-infrared AIE compounds with large stokes shift is a problem to be solved.

The compound with Excited State Intramolecular Proton Transfer (ESIPT) property can generate large Stokes shift due to 'alcohol-ketone' tautomerism, can effectively eliminate internal filtering effect and fluorescence self-absorption effect, enhance the contrast between target fluorescence and background fluorescence, and improve the detection sensitivity. In consideration of the performance advantages brought by AIE and ESIPT properties, the two luminescence mechanisms are combined to develop a novel 'AIE + ESIPT' fluorescent compound, and the novel 'AIE + ESIPT' fluorescent compound can exert more advantages in the fields of chemical sensing, biological recognition, imaging and the like. For example: liu (J.Mater.chem.B.2018,6(13),1973-1983.) and the like combine ESIPT structural module benzothiazole with AIE structural module tetraphenylethylene with a propeller shape to successfully prepare a fluorescent compound with dual effects of ESIPT and AIE, and researches show that certain synergistic effect exists between the two effects, namely: the structure of the fluorescent molecule can be more rigid due to intramolecular hydrogen bonds formed by the benzothiazole under light excitation, so that intramolecular rotation is inhibited, non-radiative attenuation is reduced, and the AIE characteristic is enhanced; meanwhile, tetraphenyl ethylene forms an aggregation state, so that the interference of proton transfer to surrounding media can be effectively avoided, the ESIPT process is facilitated, and fluorescent molecules are promoted to generate large Stokes displacement and strong ketone emission. However, in the fluorescent molecule, the ESIPT structure module benzothiazole and the AIE structure module tetraphenylethylene are both electron donors, effective push-pull electron action is lacked in the molecule, the emission wavelength is not obviously red-shifted, and the luminescence is still in a yellow region after aggregation. If an ESIPT structure module with electron pushing property and an AIE structure module with electron pulling effect and steric hindrance effect are selected to construct a 'push-pull' electronic structure, fluorescent compounds with ESIPT, AIE and near infrared characteristics can be obtained, multiple advantages of the fluorescent compounds can be exerted to a certain extent, and the defects of single ESIPT, AIE and near infrared fluorescent compounds in biosensing and fluorescence imaging are overcome.

Disclosure of Invention

Aiming at the problems of small Stokes shift, short fluorescence emission wavelength (concentrated in ultraviolet light and visible light regions), difficult synthesis and the like of the existing AIE compound, the invention provides a benzothiazole-phenethyl cyanide compound with excitation state intramolecular proton transfer and aggregation induced emission properties, a preparation method and application thereof, the method takes 2- (2 ' -hydroxy-3 ' -formyl-5 ' -methylphenyl) benzothiazole (BA for short) which has high fluorescence quantum yield, large Stokes displacement, good optical stability and yellow light emission as an ESIPT structure module, the near infrared fluorescent compound (BA-CN for short) with the excited intramolecular proton transfer and aggregation induced luminescence properties is obtained by the bond connection of the Knoevenagel condensation reaction and the AIE structure module 4-cyanophenylacetonitrile with the electron withdrawing property. Compared with the existing 'AIE + ESIPT' compound, the BA-CN prepared by the method has the characteristics of simple synthesis (one-step reaction), higher yield (more than 80%), large Stokes shift (330nm), emission wavelength (635nm) in a near-infrared region and the like. The compound can be applied to the field of fluorescence detection.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a benzothiazole-phenethyl cyanide compound, the molecular formula is:

the preparation method of the benzothiazole-phenethyl cyanide compound comprises the following steps:

(1) adding 4-cyanobenzene acetonitrile, a catalyst and acetonitrile into BA serving as a raw material, and uniformly mixing to obtain a mixed solution; the formula proportion of the mixed solution is as follows:

wherein the molecular formula of BA is:

the catalyst is selected from one or more of triethylamine, pyrrolidine and 4-methylpiperidine;

(2) stirring the mixed solution at 30-82 ℃ for reaction for 1-12 hours;

(3) after the reaction is finished, a brown precipitate is separated out; the precipitate was filtered and washed 2-3 times with acetonitrile to give pure BA-CN.

The formula proportion of the mixed solution in the step (1) is preferably as follows:

step (2) is preferably stirred at 50-82 ℃ for 5-10 hours.

Structural identification of the compound:

the probe BA-CN nuclear magnetic resonance hydrogen spectrum results are as follows:

¹H NMR(500MHz,CDCl₃)：δ＝13.37(s,1H),8.29(s,1H),8.21(s,1H),8.02(d,J＝8.1,1H),7.97(d,J＝7.9,1H),7.87(d,J＝8.5,2H),7.78(d,J＝8.5,2H),7.65(s,1H),7.57(dd,J＝11.3,4.1,1H),7.48(t,J＝7.6,1H),1.60(s,3H).

the probe BA-CN nuclear magnetic resonance carbon spectrum results are as follows:

¹³C NMR(126MHz,CDCl₃)：δ＝168.72,155.33,151.46,139.07,132.76,132.57,131.66,129.61,128.95,126.99,126.58,125.98,122.22,121.65,118.29,117.37,116.96,112.49,109.66,20.64.

the probe BA-CN high resolution mass spectrum result is as follows:

ESI-MS m/z：[M-H]⁺392.0853 (experimentally determined values), 392.0863 (theoretically calculated values).

The preparation method of the invention is greatly influenced by the raw material mixing ratio, the catalyst dosage, the reaction temperature and the reaction time. The raw material mixing ratio is too large, and the BA-CN is difficult to purify; too low raw material charge ratio, too small catalyst amount, too low reaction temperature and too short reaction time can result in reduced BA-CN yield. The appropriate raw material proportioning can save cost, and the appropriate reaction temperature and reaction time can improve the reaction yield.

Compared with the prior art, the invention has the innovation points that:

1. the invention successfully synthesizes a novel benzothiazole-phenethyl cyanide compound BA-CN, which has ESIPI, AIE and near-infrared emission characteristics at the same time, and compared with a single ESIPT, AIE and near-infrared fluorescent compound, the multi-mechanism compound fluorescent compound shows more advantages.

2. The invention takes BA and 4-cyano benzene acetonitrile as initial raw materials, and the benzothiazole-phenethyl cyanide compound BA-CN with higher yield and convenient purification can be obtained by simple one-step reaction. More importantly, the BA-CN molecular skeleton prepared by the method has an active hydroxyl group, and a fluorescent probe can be constructed by a hydroxyl protection-deprotection strategy, so that the method has wide application prospect in the fields of biosensing and bioimaging.

3. The benzothiazole-phenethyl cyanide compound BA-CN has the advantages of no concentration quenching effect in high concentration, strong fluorescence emission, large Stokes shift and the like, and effectively overcomes the defects of ACQ effect, fluorescence self-absorption, background fluorescence and the like in the use of the traditional fluorescent compound.

The detailed structure of the present invention will be further described with reference to the accompanying drawings and the detailed description.

Drawings

FIG. 1 is a schematic diagram of the synthesis of the compound BA-CN in the present invention. As shown in figure 1, BA-CN can be obtained by taking BA and 4-cyano phenylacetonitrile as initial raw materials and carrying out simple one-step reaction; the preparation method has the characteristics of mild synthesis conditions, high yield (more than 80%), simple purification (filtration and washing), and the like.

FIG. 2 is a hydrogen spectrum of the compound BA-CN prepared according to the present invention (compound BA-CN in CDCl)₃In (1)¹H NMR spectrum (500 MHz)). As can be seen from FIG. 2, the product prepared by the example of the present invention is relatively pure; the characteristic proton resonance signal peak of hydroxyl at the low field of 13.37ppm indicates that intramolecular hydrogen bond (-OH & N & C) exists in the BA-CN molecule.

FIG. 3 is a carbon spectrum of the compound BA-CN prepared according to the present invention (compound BA-CN in CDCl)₃In (1)¹³C NMR spectrum (126 MHz)).

FIG. 4 is a high resolution mass spectrum of BA-CN compound prepared by the present invention, wherein the peak at 392.0853 is BA-CN molecular ion peak, which shows that BA-CN is successfully prepared by the present invention.

FIG. 5 shows the UV-visible absorption spectrum and the fluorescence emission spectrum of the compound BA-CN prepared according to the present invention. One of BA-CN at 305nm is assigned to pi-pi^*The ultraviolet absorption peak of the transition has a maximum fluorescence emission peak at 635nm, which is assigned to a 'ketone type' structure and falls in a near infrared region. The Stokes shift of BA-CN is as high as 330nm, and the internal filtering effect and the fluorescent self-absorption effect can be effectively eliminated in the fluorescent detection and biological application.

FIG. 6 shows fluorescence spectra of the prepared compound BA-CN (10 μ M) in different solvents. In ether, BA-CN has dual emission peaks, where the short wavelength fluorescence emission peak is the "alcoholic" emission peak and the long wavelength strong fluorescence emission peak is the "ketone" emission peak; in ethyl acetate, dichloromethane, acetone and dimethyl sulfoxide, a single and strong "ketonic" emission peak is exhibited. The above spectroscopic data illustrate that BA-CN has typical ESIPT properties.

FIG. 7 shows fluorescence spectra of the prepared compound BA-CN (10. mu.M) in different water ratios of mixed tetrahydrofuran-water system.

FIG. 8 is a graph showing the change of fluorescence intensity of the compound BA-CN (10. mu.M) prepared according to the present invention in a mixed system of tetrahydrofuran and water having various water content ratios. The inset is a fluorescent photograph of the test solution under a 365nm ultraviolet lamp. In the tetrahydrofuran-water system, the fluorescence intensity of the compound BA-CN increased with increasing water content, indicating that the compound BA-CN has AIE properties.

Detailed Description

The present invention is described in more detail below with reference to examples, but it should not be construed that the scope of the present invention is limited to the examples below, and any technologies implemented based on the above contents of the present invention are within the scope of the present invention.