A negative photochromic organic compound and a method for preparing the same

Abstract

The application relates to the field of new material synthesis, in particular to a kind of negative photochromic organic compound with 1,3-dihydro-1,3,3-trimethylspiro[2H-benzo[f]indol-2,2'-[2H-1]benzopyran] as core structure; the application realizes the synthesis and application of the negative photochromic organic compound with 1,3-dihydro-1,3,3-trimethylspiro[2H-benzo[f]indol-2,2'-[2H-1]benzopyran] as core structure.

Description

Technical Field

[0001] This invention belongs to the field of new material synthesis, specifically relating to a negative photochromic organic compound and its preparation method. Background Technology

[0002] From a scientific perspective, the photochromic effect of molecules is the result of a change in molecular configuration from one state to another through the absorption of light, and the two states have different energy levels, corresponding to different absorption spectra, especially in the visible light range. In fact, the applications of photochromic materials exist not only in traditional variable transmission devices (such as ophthalmic sunglasses), but also in the development of switches, logic gates, photoinduced molecular motion (such as rotors and fibrils), and the light modulation of drug availability, taking into account the ability of these molecules to undergo structural and electronic rearrangement upon photoactivation.

[0003] Most photochromic materials studied to date have been classified as ordinary or positive photochromic dyes, in which the deeper colors reversibly manifest upon exposure (usually to ultraviolet light), such as in ophthalmic sunglasses where the lenses appear tinted in normal sunlight and fade when placed in the shade, as disclosed in US4286957. In contrast to ordinary photochromic dyes, negative photochromic dyes, as described in WO2017 / 189700, are molecules whose color reversibly fades upon exposure to electromagnetic radiation (such as visible light or sunlight), but the color intensity is restored in the absence of visible light; that is, the dye's intense color manifests in the dark. Simply put, the color of a negative photochromic dye is brighter in dark environments and darker in bright environments, a phenomenon known as the darkening effect. Although scientists have conducted scientific research on various positive or positive photochromic compounds and explored many known commercial applications, such as ophthalmic sunglasses lenses, negative photochromic compounds have been rarely developed, and their applications are very limited. Summary of the Invention

[0004] To address the aforementioned problems, this invention discloses a class of negative photochromic organic compounds with a core structure of 1,3-dihydro-1,3,3-trimethylspiro[2H-benzo[f]indole-2,2′-[2H-1]benzopyran].

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] This invention provides a negative photochromic organic compound, the structure of which is shown in Formula I:

[0007]

[0008] Wherein, R is a C1-18 alkyl chain.

[0009] Furthermore, the structure of the negative photochromic organic compound is shown in Formula II:

[0010] .

[0011] A molecule of Formula I is a highly polar molecule with two strongly electron-withdrawing nitro substituents. An example of a compound of Formula I is shown in Formula II, where R is butyl, and is called the negative photochromic dye ND0459. The two strongly electron-withdrawing nitro groups stabilize the negatively charged portion of the zwitterionic subcyanine (MC) form, called MC0459. MC0459 is a highly conjugated system with strong absorption in the visible light range, thus exhibiting a dark red color. Thermodynamically, this conjugated MC0459 is more stable than SP0459. Because the conjugation between the aromatic rings in SP0459 is disrupted, its energy is higher, and it has almost no absorption in the visible light range, thus appearing colorless. Exposure to visible light in this case causes a transition from MC0459 to SP0459, i.e., a color change. When SP0459 is placed in the dark, it reverts to the colored MC0459, i.e., a darkening effect.

[0012]

[0013] This invention also provides a method for preparing the negative photochromic organic compound as described above, comprising the following steps:

[0014] (1) Add a mixture of nicotinic acid and sulfuric acid to 5-nitrosalicylaldehyde, stir the reaction mixture into crushed ice, and then extract with methyl tert-butyl ether. Wash the organic phase with deionized water and brine, dry with sodium sulfate and concentrate. Add hexane and methanol to the concentrated organic phase to precipitate, and wash the precipitate with hexane to obtain a light yellow solid IT0228.

[0015] (2) 1-Butyl-2,3,3-trimethyl-3H-benzo[e]indole-1-iodide was added to a sodium hydroxide solution with a mass fraction of 20%. After stirring the reaction, the reaction mixture was extracted with methyl tert-butyl ether. The organic phase was washed with deionized water and brine. After drying with sodium sulfate, the mixture was concentrated to obtain a green viscous liquid IT0265.

[0016] (3) Under an argon atmosphere, ITO228 obtained in step (1) and ITO265 prepared in step (2) were added to anhydrous ethanol, heated and refluxed for 12-24 hours, cooled and washed with methanol and hexane in sequence, and dried to obtain the negative photochromic organic compound ND0459.

[0017] Further, in step (1), the mass-volume ratio of 5-nitrosalicylaldehyde to fuming sulfuric acid is 10:1-10:5, and the mass-volume ratio of 5-nitrosalicylaldehyde to sulfuric acid is 1:10-1:100; the stirring reaction temperature is 15-30℃.

[0018] Further, in step (2), the mass-to-volume ratio of 1-butyl-2,3,3-trimethyl-3H-benzo[e]indole-1-iodide to sodium hydroxide solution is 1:100-1:10, and the stirring temperature is 15-30℃.

[0019] Furthermore, the mass ratio of ITO228 obtained in step (1) to ITO265 prepared in step (2) is 2.19:2.7, and the mass-volume ratio of ITO228 obtained in step (1) to anhydrous ethanol is 2.19:250.

[0020] The present invention also provides the use of the organic compounds described above in negative photochromic materials.

[0021] The present invention also provides the application of an organic compound prepared by the method described above in a negative photochromic material.

[0022] The beneficial effects of this invention are as follows:

[0023] The negative photochromic organic compound of Formula I in this invention integrates a benzimidazole ring instead of the indole ring typically studied, in order to stabilize the positive charge generated on the nitrogen atom when the molecule is in the colored MC form, such as MC0459. Furthermore, compared to molecules with an indole core, the benzimidazole core provides more binding to the system, further lowering the energy level, absorbing more visible light, and thus resulting in a deeper color in the dark.

[0024] Another design in Formula I involves the integration of an alkyl chain on the nitrogen atom of the benzimidazole core, i.e., R in Formula I. Chemically, the alkyl chain is inherently hydrophobic, while the zwitterionic moiety of the MC form in Formula I is inherently hydrophilic. Therefore, the choice of the R group in the alkyl chain of Formula I provides an opportunity to adjust the hydrophobicity and hydrophilicity of the Formula I molecule to meet the specific needs of certain applications. A longer alkyl chain on the nitrogen atom of the benzimidazole moiety in Formula I results in greater hydrophobic functionality. R = butyl (C4H9) is chosen in the design of a compound with a specific structure to balance the hydrophilicity and hydrophobicity. The synthetic route of the negative photochromic organic compound of this invention is simple and efficient, with minimal scale-up effects. Attached Figure Description

[0025] Figure 1 This is a diagram showing the molecular configuration transition of the negative photochromic molecule of this invention during photoactivation;

[0026] Figure 2The negative photochromic compound prepared in Example 3 of this invention 1 H-NMR spectrum;

[0027] Figure 3 The absorption spectrum of the negative photochromic molecule prepared in Example 3 of this invention in the dark. Detailed Implementation

[0028] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0029] Unless otherwise specified, all chemicals and reagents are ACS grade and purchased from Sigma-Aldrich. Example 1

[0030] Synthesis of IT0228

[0031] 10 g of 5-nitrosalicylic acid was added to a 1000 ml glass flask. Then, a mixture of 3.8 ml of fuming sulfuric acid and 500 ml of sulfuric acid was added to the flask. The mixture was stirred at room temperature for 3 hours, and then carefully poured into 1000 g of crushed ice. The resulting mixture was extracted twice with 1000 ml of methyl tert-butyl ether (MTBE). The combined organic phases were washed successively with 1000 ml of deionized water and 1000 ml of brine, and then dried over sodium sulfate. The drying agent was filtered off, and the organic phase was concentrated to approximately 500 ml using a rotary evaporator. 200 ml of hexane and 20 ml of methanol were added to the concentrated organic phase to precipitate the solid. The precipitate was collected by filtration and washed with hexane to give 5.6 g of a pale yellow solid. NMR spectroscopy confirmed that the collected yellow solid was ITO228, with the structure shown below. Figure 1 As shown. Example 2

[0032] Synthesis of IT0265

[0033] 10.3 g of 1-butyl-2,3,3-trimethyl-3H-benzo[e]indole-1-iodide (IT0395, commercially available from 1-Material Inc, Canada) was mixed with 500 mL of 20% (w / w) sodium hydroxide solution and stirred at room temperature for 2 hours. The resulting mixture was extracted twice with 500 mL of methyl tert-butyl ether (MTBE), and the combined organic phases were washed successively with 300 mL of deionized water and 300 mL of brine, followed by drying with sodium sulfate. The drying agent was filtered off, and the solvent was removed by rotary evaporation to give 6.81 g of a green viscous liquid, which was analyzed by NMR to confirm its composition. 1 The structure confirmed by H-NMR is IT0265, and the structure is as follows: Figure 1 As shown. Example 3

[0034] Synthesis of ND0459

[0035] 2.19 g of ITO228 prepared in Example 1 and 2.7 g of ITO265 prepared in Example 2 were mixed with 250 ml of anhydrous ethanol into a 500 ml four-necked round-bottom flask equipped with a mechanical stirrer, condenser, and argon inlet / outlet protection device. The resulting mixture was heated to reflux and maintained for 24 hours, then cooled to room temperature. The precipitate formed after cooling was filtered, washed successively with 50 ml of methanol and 50 ml of hexane, and dried in a vacuum oven for 24 hours. It was a beige solid under normal light, with a mass of 3.9 g. The yield was 83.5%. Figure 2 The 1H NMR of this solid was performed, confirming its structure as ND0459, as shown below. Figure 1 As shown. The molecule is a typical spiropyran compound, and its color changes from dark red in the dark (on the left) to colorless (on the right) when exposed to visible light. Example 4

[0036] ND0459's photochromic function

[0037] 2 mg of ND0459 was dissolved in 10 ml of analytical grade dichloromethane (DCM). Under normal indoor lighting, the solution was observed to be pale yellow. When exposed to outdoor sunlight, the color rapidly disappeared. When stored in an opaque container (dark environment), the color gradually turned deep purplish-red. Furthermore, the spectral absorbance of the solution was measured using a marine optical spectrometer. Figure 3 The absorption spectra of the solution in the dark are shown after exposure to room temperature for 1 minute and 2 minutes, respectively. Clearly, the solution exhibits strong absorption in the visible light range in the dark environment, and the absorption in the visible light range decreases rapidly after 1 minute of exposure to indoor light, while almost no absorption in the visible light range is observed after 2 minutes of exposure to outdoor light. This demonstrates strong negative photochromic behavior.

[0038] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A negative photochromic organic compound, characterized in that, The structure of the negative photochromic organic compound is shown in Formula I: Formula I; Wherein, R is a C1-18 alkyl chain.

2. The negative photochromic organic compound according to claim 1, characterized in that, The structure of the negative photochromic organic compound is shown in Formula II: Formula II.

3. A method for preparing the negative photochromic organic compound as described in claim 2, characterized in that, Includes the following steps: (1) Add a mixture of nicotinic acid and sulfuric acid to 5-nitrosalicylaldehyde, stir the reaction mixture into crushed ice, and then extract with methyl tert-butyl ether. Wash the organic phase with deionized water and brine, dry with sodium sulfate and concentrate. Add hexane and methanol to the concentrated organic phase to precipitate, and wash the precipitate with hexane to obtain a light yellow solid IT0228. ； (2) 1-Butyl-2,3,3-trimethyl-3H-benzo[e]indole-1-iodide was added to a sodium hydroxide solution with a mass fraction of 20%. After stirring the reaction, the reaction mixture was extracted with methyl tert-butyl ether. The organic phase was washed with deionized water and brine. After drying with sodium sulfate, the mixture was concentrated to obtain a green viscous liquid IT0265. ； (3) Under an argon atmosphere, ITO228 obtained in step (1) and ITO265 prepared in step (2) were added to anhydrous ethanol, heated and refluxed for 12-24 hours, cooled and washed with methanol and hexane in sequence, and dried to obtain the negative photochromic organic compound ND0459. 。 4. The method for preparing a negative photochromic organic compound according to claim 3, characterized in that, In step (1), the mass-volume ratio of 5-nitrosalicylaldehyde to fuming sulfuric acid is 10:1-10:5, and the mass-volume ratio of 5-nitrosalicylaldehyde to sulfuric acid is 1:10-1:100; the stirring temperature is 15-30℃.

5. The method for preparing a negative photochromic organic compound according to claim 3, characterized in that, In step (2), the mass-to-volume ratio of 1-butyl-2,3,3-trimethyl-3H-benzo[e]indole-1-iodide to sodium hydroxide solution is 1:100-1:10, and the stirring temperature is 15-30℃.

6. The method for preparing a negative photochromic organic compound according to claim 3, characterized in that, In step (3), the mass ratio of ITO228 obtained in step (1) to ITO265 prepared in step (2) is 2.19:2.7, and the mass-volume ratio of ITO228 obtained in step (1) to anhydrous ethanol is 2.19:

250.

7. The use of an organic compound as described in claim 1 or 2 in negative photochromic materials.

8. The application of an organic compound prepared by the preparation method according to any one of claims 3-6 in negative photochromic materials.

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