A class of diketopyrrolopyrrole pigments, and methods of making and using the same

Abstract

The application discloses a kind of double pyrrolopyrrolodione pigment and its preparation method and application, the double pyrrolopyrrolodione pigment is coupled by the alkyl diamine straight chain of different chain length to two molecules pyrrolopyrrolodione, its general structure formula is as shown in formula 1.The application is with halogenated pyrrolopyrrolodione monomer as raw material, under alkaline condition, it is reacted with alkyl dihalogenated substance of different length, obtains double pyrrolopyrrolodione product.This kind of pigment has the characteristics such as bright color, high light and heat stability, good biocompatibility, can be easily prepared into ink, and is used for the preparation of color contact lenses.

Description

Technical Field

[0001] This invention belongs to the field of contact lens pigments, specifically relating to a class of bispyrrolopyrrole dione pigments, their preparation methods, and applications. Background Technology

[0002] Colored contact lenses have become increasingly popular over the past few decades, and they have a promising future in the contact lens market.

[0003] Colored contact lenses can be divided into two main categories: the first type features transparent or opaque colored patterns only in the iris area, allowing the iris to display specific colors and patterns; the second type uses transparent pigments to enhance the lens's color, with the essentially transparent pigment evenly dispersed throughout the entire lens, resulting in a colored appearance. The first type is the most widely used due to its mature manufacturing process, diverse colors and patterns, and complete lack of impact on the lens's optical performance.

[0004] However, colored contact lenses for the iris area often require the addition of colored pigments (usually organic pigments) during manufacturing. Several problems can arise during the manufacturing process or after prolonged wear, including:

[0005] 1) Heat resistance issues. The manufacturing process of eyeglasses involves multiple high-temperature steps such as curing and sterilization, during which some organic pigments may decompose.

[0006] 2) Lightfastness issues. During prolonged wear and storage, factors such as light exposure can cause pigment decomposition and fading.

[0007] 3) Biocompatibility issues. Although organic pigments undergo rigorous biological evaluation before use and are considered to be highly safe, the small molecule compounds produced after their degradation under light and heat conditions may have certain biological effects, thus posing a biocompatibility risk.

[0008] In response to this situation, there is an urgent need to develop colored contact lenses that can both meet people's aesthetic needs and ensure stable photothermal quality of the pigments. To meet this requirement, the development of novel organic colored pigments is crucial. Among these, red pigments are prone to fading in practical use, making the development of novel and stable red pigments essential.

[0009] Pyrrolopyrrole dione (DPP) pigments, such as CI Pigment Red 254 and 255, are highly sought-after high-grade red pigments due to their vibrant colors, high tinting strength, and relatively simple and environmentally friendly production processes. Furthermore, because DPP molecules possess intermolecular hydrogen bonds and have a planar molecular structure, they are prone to conjugated aggregation (molecular mechanism can be found in [reference needed]). Figure 1 Therefore, the stability of this type of pigment is significantly improved compared to traditional red pigments. However, the stability obtained solely through intermolecular planar conjugation aggregation is ultimately limited, and these pigments still exhibit denaturation and discoloration under prolonged light and heating. Patent WO2009037350 reported a type of DPP pigment coupled with disulfide bond linkages for dyeing keratin materials (mainly human hair). Due to the presence of sulfur-containing functional groups, this type of pigment exhibits stronger adhesion to keratin, resulting in more durable dyeing effects and better color brightness; however, it does not improve the photothermal stability of the pigment. Therefore, further structural optimization and modification of DPP pigments are necessary to enhance their photothermal stability. Summary of the Invention

[0010] Purpose of the invention: To address the problems existing in the prior art, this invention provides a novel type of bispyrrolopyrrole dione pigment with good photothermal stability that can be used to prepare colored contact lenses. It effectively solves the problems of poor photothermal stability and easy fading and discoloration of red pigments in current colored contact lenses, and shows significant advantages in terms of photothermal stability and biocompatibility.

[0011] This invention also provides a method for preparing and applying the aforementioned type of dipyrrolopyrrole dione pigment.

[0012] Technical solution: To achieve the purpose of this invention, the present invention provides a type of dipyrrolopyrrole dione pigment, wherein two molecules of pyrrolopyrrole dione are coupled through straight chains of alkyl diamines of different chain lengths, and its general structural formula is shown in Formula 1:

[0013]

[0014] Where X is a chlorine atom, bromine atom, fluorine atom, iodine atom, or a C1-C4 alkyl group; n is an integer from 3 to 5.

[0015] The preparation method of the bispyrrolopyrrole dione pigment of the present invention includes the following steps:

[0016] Using halopyrrolopyrroledione monomers as raw materials, they are added to solvent A and reacted with alkyl dihalogenated products of different lengths under the action of alkaline reagents. The reactants are washed with solvent B and water, filtered, dried and ground to obtain the dipyrrolopyrroledione product.

[0017] The general reaction formula is as follows:

[0018]

[0019] Wherein, Formula 2 is a halopyrrolopyrroledione monomer. These are alkyl dihalogenated compounds of different lengths.

[0020] The alkaline reagent includes any one or more of potassium carbonate, sodium methoxide, sodium ethoxide, and sodium hydride.

[0021] Wherein, solvent A is any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, methanol, and ethylene glycol dimethyl ether.

[0022] The molar ratio of the halogenated pyrrolopyrroledione monomer, the basic reagent, and the alkyl dihalogenated product is (2.0–4.0):(4.0–6.0):1.

[0023] The reaction temperature is 80–150°C.

[0024] The reaction time is 12 to 36 hours.

[0025] Solvent B is any one or more of methanol, ethylene glycol dimethyl ether, ethanol, or N,N-dimethylformamide.

[0026] The bispyrrolopyrrole dione pigments described in this invention are formulated into inks for use in the preparation of colored contact lenses.

[0027] Preferably, the dipyrrolopyrrole dione pigment is used as a photothermally stable red pigment.

[0028] This invention obtains dual-linked DPPs through the design of flexible alkyl diamine linear chains of varying lengths. These dual-linked molecules fold themselves to form an interlocking, cross-conjugated aggregation pattern. Compared to the layered conjugation pattern of DPP molecules, this cross-conjugated aggregation pattern further enhances the stability of the pigment molecules' conjugated aggregation, and its intermolecular conformational effect is as follows: Figure 2 As shown.

[0029] The pigments prepared by this invention have the characteristics of bright colors, high photothermal stability, and good biocompatibility. They can be easily formulated into inks for use in the preparation of colored contact lenses.

[0030] This invention, based on DPP monomer pigment molecules, couples two DPP molecules through flexible alkyl diamine straight chains of different lengths to obtain dual-DPP. These molecules possess cross-conjugated aggregation properties, which enhance the stability of pigment molecule conjugation and overcome the shortcomings of existing colored contact lens red pigments, such as poor photothermal stability. The novel dual-pyrrolopyrrole dione pigment of this invention has a dual-DPP molecular structure, which is not only easy to prepare but also exhibits superior photothermal stability and biocompatibility compared to monomeric DPP.

[0031] Beneficial Effects: Compared with existing technologies, this invention, based on DPP monomer pigment molecules, couples two DPP molecules through flexible alkyl diamine straight chains of different lengths to obtain dual-linked DPP. These dual-linked molecules can fold themselves to form an interlocking, cross-conjugated aggregation mode. Compared to the layered conjugation mode of monomeric DPP molecules, the cross-conjugated aggregation mode of the dual-linked DPP molecules disclosed in this invention further enhances the stability of pigment molecule conjugation aggregation. Specifically, the dual-linked DPP molecules disclosed in this invention have the following advantages:

[0032] 1. It can overcome the defects of poor photothermal stability of red pigments in current colored contact lenses, and is not easy to fade when stored and used under high heat and strong light conditions;

[0033] 2. The method for preparing bispyrrolopyrrole dione pigments disclosed in this invention is simple and easy to implement, and is suitable for large-scale industrial preparation.

[0034] 3. This pigment has good biocompatibility and can be formulated into inks for the preparation of colored contact lenses. Attached Figure Description

[0035] Figure 1 : Intermolecular force diagram of DPP molecules;

[0036] Figure 2 : A diagram showing the difference in aggregation modes between single DPP molecules and double DPP molecules;

[0037] Figure 3 : NMR spectrum of pigment 1;

[0038] Figure 4 : NMR spectrum of pigment 2;

[0039] Figure 5 : NMR spectrum of pigment 3;

[0040] Figure 6 Thermogravimetric analysis results of monomeric compounds and pigments 1, 2, and 3;

[0041] Figure 7 Images showing the appearance of pigments 1, 2, 3 and commercially available reference materials before and after ultraviolet light irradiation;

[0042] Figure 8 Thermal stability test diagrams of color films in Examples 5-7;

[0043] Figure 9 Examples 5-7: Photostability test diagrams of colored films;

[0044] Figure 10 Cell proliferation rate of different concentrations of extracts from lenses in Examples 5-7 and Comparative Example 1. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. Experimental methods not specifically described in the examples are generally performed under standard conditions or as recommended by the manufacturer.

[0047] Example 1

[0048] Preparation of Pigment 1

[0049]

[0050] Bis(p-chlorophenyl)-1,4-dionepyrrolopyrrole (5 g, 14 mmol) and potassium carbonate (3.9 g, 28 mmol) were added to 100 mL of N,N-dimethylformamide (DMF). The reaction solution was heated to 90 °C, and 1,6-dibromohexane (1.4 g, 6 mmol, dissolved in 10 mL of DMF) was added dropwise to the system using a dropping funnel. After the addition was complete, the reaction was maintained at 90 °C for 24 h. Upon cooling, a red precipitate formed. The precipitate was filtered, washed with methanol and water respectively, dried, and ground to obtain a red powdery solid, which was pigment 1.

[0051] The NMR data are as follows: 1 H NMR (500MHz, DMSO-d6): δ8.59(d,4H,arom),8.35(d,4H,arom),7.76-7.80(m,4H,arom),7.60-7.75(m,4H,arom),3.65(br,2H,2N H ), 3.30-3.45 (m, 4H, 2NC) H2 ), 1.00-1.50 (m, 8H, 4C) H2 ESI-MS:[M+H] + =794.9. The NMR spectrum is as follows: Figure 3 As shown.

[0052] Example 2

[0053] Preparation of Pigment 2

[0054]

[0055] A mixture of bis(p-bromophenyl)-1,4-dionepyrrolopyrrole (4.4 g, 10 mmol) and 1,6-dichlorohexane (0.4 g, 2.5 mmol) was dissolved in 200 mL of dimethyl sulfoxide (DMSO), and then sodium methoxide (0.8 g, 15 mmol) was added. The mixture was reacted at 80 °C for 36 h. After the reaction was complete, the mixture was cooled, filtered, and the filter cake was washed with ethylene glycol dimethyl ether and water, respectively. The product was then dried and ground to obtain a red powder, which is pigment 2.

[0056] The NMR data are as follows: 1 H NMR (500MHz, DMSO-d6): δ8.49(d,4H,arom),8.30(d,4H,arom),7.70-7.80(m,8H,arom),3.62(s,2H,2N H ), 3.35-3.40 (m, 4H, 2NC) H2 ), 1.10-1.65 (m, 8H, 4C) H2 ESI-MS:[M+H] + =974.1. The NMR spectrum is as follows: Figure 4 As shown.

[0057] Example 3

[0058] Preparation of Pigment 3

[0059]

[0060] Bis(p-fluorophenyl)-1,4-dione pyrrolopyrrole (3.9 g, 12 mmol) and sodium hydride (0.48 g, 20 mmol) were added to 100 mL of anhydrous N-methylpyrrolidone. The reaction mixture was heated to 150 °C, and 1,4-diiodobutane (1.2 g, 4 mmol, dissolved in 10 mL of N-methylpyrrolidone) was added dropwise to the system using a dropping funnel. The reaction was maintained at 150 °C for 12 h. After cooling the reaction mixture to room temperature, a red precipitate formed. The mixture was then filtered.

[0061] The sample was washed with N,N-dimethylformamide and water, dried, and ground to obtain a red powdery solid, which is pigment 3. The NMR data are as follows: 1 H NMR (500MHz, DMSO-d6): δ8.46(d,4H,arom),8.30(d,4H,arom),7.76-7.81(m,8H,arom),3.61(br,2H,2N H ),2.62(m,4H,2NC H2 ),1.23(br,4H,2CH2 ESI-MS:[M+H] + =766.9. The NMR spectrum is as follows: Figure 5 As shown.

[0062] Example 4

[0063] Preparation of Pigment 4

[0064]

[0065] Bis(p-chlorophenyl)-1,4-dionepyrrolopyrrole (5 g, 14 mmol), sodium ethoxide (0.9 g, 14 mmol), and potassium carbonate (3.9 g, 28 mmol) were added to 100 mL of a mixed solvent of ethylene glycol dimethyl ether / N,N-dimethylacetamide / methanol (1:1:1, v / v / v). The reaction solution was heated to 90 °C, and 1,5-dibromopentane (1.6 g, 7 mmol, dissolved in 10 mL of ethylene glycol dimethyl ether) was added dropwise to the system using a dropping funnel. After the addition was complete, the reaction was maintained at 90 °C for 24 h. Upon cooling, a red precipitate formed. The precipitate was filtered, washed with ethanol / N,N-dimethylformamide, and water, and dried and ground to obtain a red powdery solid, which was pigment 4. ESI-MS: [M+H] + =781.1.

[0066] Example 5

[0067] Preparation of Pigment 1 Colored Contact Lenses

[0068] Weigh out 12.67g of hydroxyethyl methacrylate (HEMA), 2.22g of methyl methacrylate (MMA), 2.56g of N-vinylpyrrolidone, 0.1g of tert-butyl peroxybenzoate, 20g of ethyl acetate, 5.3g of pigment, and 1g of zirconium balls (1.6mm in diameter). Grind the mixture in a ball mill for 30 minutes. Use a pad printing machine to transfer the resulting ink to the lens mold. Mix 20g of hydroxyethyl methacrylate (HEMA), 0.1g of ethylene glycol dimethacrylate (EGDMA), and 0.1g of azobisisobutyronitrile (AIBN) until homogeneous. Drop the mixture into the mold and cure it at 80℃ for 24 hours. Hydrate it in pure water for 5 hours. Then transfer it to standard saline solution (prepared according to GB / T 11417.4 national standard) to produce colored contact lenses.

[0069] Example 6

[0070] Preparation of Pigment 2 Colored Contact Lenses

[0071] Weigh 12.50g of hydroxyethyl methacrylate (HEMA), 2.01g of methyl methacrylate (MMA), 2.59g of N-vinylpyrrolidone, 0.1g of tert-butyl peroxybenzoate, 20g of ethyl acetate, 5.5g of pigment, and 2g of zirconium balls. Grind them in a ball mill for 30 minutes. Use a pad printing machine to transfer the resulting ink to the lens mold. Stir 20g of HEMA, 0.1g of EGDMA, and 0.1g of AIBN until homogeneous. Drop the mixture into the mold and cure it at 80℃ for 24 hours. Hydrate it in pure water for 5 hours. Then transfer it to standard saline solution to produce colored contact lenses.

[0072] Example 7

[0073] Preparation of Pigment 3 Colored Contact Lenses

[0074] Weigh 12.22g of hydroxyethyl methacrylate (HEMA), 2.00g of methyl methacrylate (MMA), 3.05g of N-vinylpyrrolidone, 0.1g of tert-butyl peroxybenzoate, 20g of ethyl acetate, 5.0g of pigment, and 2g of zirconium balls. Grind them in a ball mill for 30 minutes. Use a pad printing machine to transfer the resulting ink to the lens mold. Stir 20g of HEMA, 0.1g of EGDMA, and 0.1g of AIBN until homogeneous. Drop the mixture into the mold and cure it at 80℃ for 24 hours. Hydrate it in pure water for 5 hours. Then transfer it to standard saline solution to produce colored contact lenses.

[0075] Comparative Example 1

[0076] Preparation of colorless contact lenses

[0077] After mixing 20g HEMA, 0.1g EGDMA, and 0.1g AIBN evenly, the mixture is dripped into a mold and cured at 80℃ for 24 hours. It is then placed in pure water for 5 hours to hydrate, and finally transferred to standard saline solution to produce colorless contact lenses.

[0078] Example 8

[0079] Cytotoxicity assay of pigments

[0080] The cytotoxicity of the samples was determined by the MTT assay: pigments 1, 2, 3, 4 and the commercially available pigment bis(p-chlorophenyl)-1,4-dionepyrrolopyrrole were added to a minimum amount of DMSO, shaken to dissolve, and then diluted with RPMI-1640 complete medium containing fetal bovine serum (the final concentrations of the test samples were controlled to be 1, 5, and 10 μM, respectively; DMSO content <0.2%). Human normal cells (MRC-5) were cultured in vitro at 37℃ and 5% CO2 using RPMI-1640 complete medium containing fetal bovine serum until they entered the exponential growth phase. Cells were collected and seeded into 96-well plates. After 24 h of culture, the original medium was discarded, and blank control (complete medium), negative control (complete medium containing 0.2% DMSO), positive control (complete medium containing 0.64% phenol), and test samples were added to each well (3 wells per group, 200 μL per well). After 72 h of in vitro culture, 20 μL of MTT (5 mg / mL) was added and incubated for 4 h. The supernatant was removed from the wells, and 100 μL of DMSO was added. The plates were shaken thoroughly until all crystals were completely dissolved. The absorbance at 490 nm was measured using a full-wavelength microplate reader, and the cell proliferation rate was calculated. The average value of the results for each group was taken. The results are shown in Table 1.

[0081] Table 1. Effects of pigments 1-4 on cell proliferation rate.

[0082]

[0083]

[0084] As shown in Table 1 above, the positive control exhibited significant cytotoxicity, and the monomeric compound bis(p-chlorophenyl)-1,4-dione pyrrolopyrrole also showed some cytotoxicity at a concentration of 10 μM. However, the pigments 1, 2, 3, and 4 disclosed in this invention did not show cytotoxicity even at a high concentration of 10 μM (as stated in GB / T16886.5-2017 Biological Evaluation of Medical Devices Part 5: In Vitro Cytotoxicity Tests, a quantitative evaluation of a decrease in cell proliferation rate exceeding 30% is considered cytotoxic). The cell proliferation rate of the test group was comparable to that of the negative control group, indicating that the bis(p-chlorophenyl)-1,4-dione pigments disclosed in this invention are non-cytotoxic under the test conditions and have better biocompatibility than commercially available monomeric compounds.

[0085] Example 9

[0086] Thermal stability test of pigments

[0087] Accelerated thermal stability testing was conducted. Pigments 1, 2, 3, and 4, along with the monomer compound bis(p-chlorophenyl)-1,4-dionepyrrolopyrrole, were placed in a 60℃ oven and kept at that temperature for 90 days. Afterward, they were removed, cooled, and their appearance was observed. The sample content was determined using liquid chromatography (Agilent 1260 high-performance liquid chromatography system, C18 column, mobile phase: acetonitrile / water (45:55, v / v)), and the decomposition rate was calculated. The results are shown in Table 2.

[0088] Table 2. Decomposition rate of pigments

[0089] Test compound Pigment 1 Pigment 2 Pigment 3 Pigment 4 Monomer compounds Decomposition rate 0.12％ 0.22％ 0.13％ 0.10％ 2.29％

[0090] As shown in the table above, pigments 1, 2, 3, and 4 showed no fading in the accelerated thermal stability test and almost no decomposition (the decomposition rate was less than 1%), indicating that these pigments have very good thermal stability. However, the monomer compound bis(p-chlorophenyl)-1,4-dione pyrrolopyrrole showed significant thermal decomposition, with a decomposition rate of 2.29%.

[0091] Given that the dual pigments disclosed in this invention have shown good stability in conventional thermal stability studies, pigments 1, 2, and 3 were selected for thermogravimetric analysis (TGA) at a temperature range of 0 to 600°C. The stability of the pigments was assessed through high-temperature degradation experiments. The test results are as follows: Figure 6 As shown, pigments 1, 2, and 3 exhibit excellent thermal stability, with thermal decomposition temperatures around 450℃. In contrast, the thermal decomposition temperature of the monomer compound bis(p-chlorophenyl)-1,4-dionepyrrolopyrrole is around 400℃, significantly lower than that of pigments 1, 2, and 3. Furthermore, the thermogravimetric curves of these three pigments are very smooth before thermal decomposition, and no step-like decomposition phenomenon is observed after thermal decomposition, indicating that the overall molecular structure of these three compounds is stable and there is no local decomposition.

[0092] Example 10

[0093] Pigment light stability test

[0094] Accelerated photostability testing was conducted. The test pigments (pigment 1, pigment 2, pigment 3, pigment 4, and a commercially available control phosphor (specifically Qingdao Shuocheng phosphor H2)) were exposed to a 40W UV lamp for 45 consecutive days. Samples were then removed, and the pigment appearance was observed. The sample content was determined using liquid chromatography (Agilent 1260 high-performance liquid chromatography system, C18 column, mobile phase: acetonitrile / water (45:55, v / v)), and the decomposition rate was calculated. The results are shown in Table 3. Figure 7 As shown.

[0095] Table 3. Decomposition rate of pigments

[0096] Test pigments Pigment 1 Pigment 2 Pigment 3 Pigment 4 fluorescent powder Decomposition rate No decomposition 0.10％ 0.12％ 0.05％ 5.60％

[0097] From the above table 3 and Figure 7 As can be seen, pigments 1, 2, 3, and 4 exhibited very good thermal stability, with almost no decomposition or fading observed in the accelerated photostability test; while the phosphor showed photostability, with 5.6% decomposing after exposure to light and exhibiting some fading.

[0098] Example 11

[0099] Thermal stability test of color film

[0100] One colored lens prepared in Examples 5-7 was placed in a vial containing standard saline solution, sealed, and stored in an oven at 130°C for 30 hours. The lenses were then removed at 15 hours and 30 hours and compared with the initial lenses to observe color changes. The results are as follows: Figure 8 As shown, the colored contact lenses prepared in Examples 5-7 did not show obvious fading or discoloration after being stored at high temperature for 15 hours and 30 hours, indicating that the colored contact lenses have good high temperature resistance.

[0101] Example 12

[0102] Light stability test of colored film

[0103] The lenses prepared in Examples 5-7 were placed in vials containing standard saline solution and directly exposed to ultraviolet light (wavelength 313 nm, power 8 W) for 30 consecutive days. The photostability of the lenses was then observed and tested. The results are as follows: Figure 9 As shown, the colored contact lenses prepared in Examples 5-7 did not show obvious fading or discoloration after being placed under light for 15 days and 30 days, indicating that the colored contact lenses have good light resistance.

[0104] Example 13

[0105] Cytotoxicity test of color film

[0106] Lenses from Examples 5-7 and Comparative Example 1 were tested for cytotoxicity according to the in vitro cytotoxicity assay method in GB / T16886.5-2017. It was found that all three colored lenses and the control lens showed no cytotoxicity. Cell proliferation rates were observed (see [reference needed]). Figure 10 GB / T16886.5-2017, Biological Evaluation of Medical Devices Part 5: In Vitro Cytotoxicity Tests, stipulates that a quantitative evaluation of a decrease in cell proliferation rate exceeding 30% is considered cytotoxic. The cell proliferation rates of the different concentrations of extracts from the lenses in Examples 5-7 and Comparative Example 1 were all above 70%, indicating that the lenses showed no cytotoxicity and met the safety evaluation requirements for lenses.

Claims

1. A class of dipyrrolopyrrole dione pigments, characterized in that, The dual-pyrrolopyrrolidinone pigments are composed of two pyrrolopyrrolidinone molecules coupled by straight chains of alkyl diamines of different chain lengths, as shown in Formula 1: ； Where X is a chlorine atom, bromine atom, fluorine atom, or iodine atom; n is an integer from 3 to 5.

2. A method for preparing a dipyrrolopyrrole dione pigment according to claim 1, characterized in that, Includes the following steps: Using halopyrrolopyrroledione monomers as raw materials, they are added to a solvent and reacted with alkyl dihalogenated products of different lengths under the action of an alkaline reagent. The reactants are washed, filtered, dried and ground to obtain the dipyrrolopyrroledione product. Its general reaction formula is as follows: ； Wherein, Formula 2 is a halopyrrolopyrroledione monomer. It is an alkyl dihalogenated compound of different lengths, selected from any one of 1,6-dibromohexane, 1,6-dichlorohexane, 1,4-diiodobutane, and 1,5-dibromopentane.

3. The method for preparing dipyrrolopyrrole dione pigments according to claim 2, characterized in that, The alkaline reagent is any one or more of potassium carbonate, sodium methoxide, sodium ethoxide, and sodium hydride.

4. The method for preparing dipyrrolopyrrole dione pigments according to claim 2, characterized in that, The solvent is any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, methanol, and ethylene glycol dimethyl ether.

5. The method for preparing dipyrrolopyrrole dione pigments according to claim 2, characterized in that, The molar ratio of the halogenated pyrrolopyrrole dione monomer, the basic reagent, and the alkyl dihalogenated product is (2.0~4.0): (4.0~6.0):

1.

6. The method for preparing dipyrrolopyrrole dione pigments according to claim 2, characterized in that, The reaction temperature is 80~150℃.

7. The method for preparing dipyrrolopyrrole dione pigments according to claim 2, characterized in that, The reaction time is 12 to 36 hours.

8. The method for preparing dipyrrolopyrrole dione pigments according to claim 2, characterized in that, The reaction mixture is washed with a solvent consisting of one or more of methanol, ethylene glycol dimethyl ether, ethanol, or N,N-dimethylformamide.

9. The use of a bispyrrolopyrrole dione pigment of claim 1 formulated into an ink for the preparation of colored contact lenses.

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