Triphenylmethane dyes

Abstract

The present invention provides a modified triarylmethane dye having the structure shown in Formula 3 [Chemical Formula 1] JPEG2025524050000021.jpg7674 wherein R1, R2, R3, R4, R5, R6, R7, A1, A2, A1', and A2' are as defined herein.

Description

Technical Field

[0001] Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 391,864, filed Jul. 25, 2022. The entire teachings of the above application are incorporated herein by reference. Field of the Invention The present invention relates to triarylmethane dyes and the use of triarylmethane dyes.

Background Art

[0002] The family of triarylmethane dyes produces bright colors that can be adjusted over a wide portion of the visible spectrum. Triarylmethane (TAM) dyes are widely used in the manufacture of paper dyes, printing inks, ballpoint pen pastes, foods, cosmetics, and an ever-widening range of consumer products. The most well-known triarylmethane dyes have been developed from the central nucleus for the purpose of enhancing resistance to decolorization.

Summary of the Invention

[0003] An object of the present invention is to provide a triarylmethane dye in which the degree of aromaticity and the accompanying optical behavior are controlled.

Brief Description of the Drawings

[0004] The foregoing and other objects, features, and advantages of the present invention will become apparent from the following more detailed description of the preferred embodiments of the present invention, as illustrated in the accompanying drawings. In the accompanying drawings, like reference numerals refer to the same parts throughout the different figures. The drawings are not necessarily to scale, rather emphasis has been placed on illustrating the principles of the present invention.

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[0005] Triarylmethanes are generally known to those skilled in the art as a series of molecules represented by Formula 1, where any combination of R groups is an aryl group that may have additional functional groups, and these functional groups include, but are not limited to, amino (primary, secondary, or tertiary), hydroxy, halogen (bromo, chloro, fluoro, iodo), nitro, methoxy, carboxy, alkyl, aryl, alkoxy, and sulfonic acid. The counterion X can be provided from an external molecule or from an inner-sphere charged group associated with any of the R groups. **[Chemical formula]**

[0006] Due to resonance present within the molecule, the structure of triarylmethane dyes can be shown in various ways as shown in Formula 2, where structures 1, 1', and 1'' are all equivalent. Based on convention, structure 1 is used herein. **[Chemical formula]**

[0007] The present invention relates to Formula 3 [Chemical formula] A modified triarylmethane dye containing the structure shown in the formula, wherein R1, R2, R3, R4, R5, R6, and R7 are independently selected from hydrogen, halogen, C1-C 16 alkyl, amino, nitro, methoxy, carboxy, aryl, alkoxy, and sulfonic acid, A1, A2, A1', and A2' are independently selected from hydrogen, alkyl, aryl, alkaryl, or alkoxy, provided that at least one of A1, A2, A1', and A2' is alkyl, aryl, alkaryl, or alkoxy. Provided is a modified triarylmethane dye.

[0008] In some embodiments, R1, R2, R3, R4, R5, R6, and R7 are independently selected from hydrogen, halogen, C1-C 16 alkyl, amino, nitro, methoxy, carboxy, aryl, alkoxy, and sulfonic acid, provided that at least one of R1, R2, or R3 is halogen.

[0009] In one embodiment, Formula 4 [Chemical formula] A modified triarylmethane dye containing the structure shown in the formula, wherein R1, R2, R3, R4, and R5 are independently selected from hydrogen, halogen, C1-C 16 alkyl, amino, nitro, methoxy, carboxy, aryl, alkoxy, and sulfonic acid, provided that at least one of R1, R2, or R3 is halogen, and A1, A2, A1', and A2' are independently selected from hydrogen, alkyl, aryl, alkaryl, or alkoxy, provided that at least one of A1, A2, A1', and A2' is alkyl, aryl, alkaryl, or alkoxy, a modified triarylmethane dye.

[0010] In some embodiments, R1, R2, R3, R4, and R5 are independently selected from hydrogen, halogen, C1-C 16 alkyl, amino, nitro, methoxy, carboxy, aryl, alkoxy, and sulfonic acid, provided that at least one of R1, R2, or R3 is halogen.

[0011] In any embodiment herein, halogen is selected from fluorine, bromine, chlorine, or iodine. In any embodiment herein, halogen is fluorine. In any embodiment herein, halogen is bromine. In any embodiment herein, halogen is chlorine. In any embodiment herein, halogen is iodine.

[0012] In any embodiment herein, amino is a primary, secondary, or tertiary amino. In any embodiment herein, amino is a primary amino. In any embodiment herein, amino is a secondary amino. In any embodiment herein, amino is a tertiary amino.

[0013] In some embodiments, only one of R1, R2, or R3 is halogen and the other two are hydrogen. In some embodiments, when R1 is halogen, R2 and R3 are hydrogen and R1 is selected from fluorine, bromine, chlorine, or iodine. In some embodiments, when R2 is halogen, R1 and R3 are hydrogen and R2 is selected from fluorine, chlorine, bromine, or iodine. In some embodiments, when R3 is halogen, R1 and R2 are hydrogen and R3 is selected from fluorine, bromine, or iodine.

[0014] In some embodiments, R4 and R5 are hydrogen.

[0015] In some embodiments, R6 and R7 are hydrogen.

[0016] In one embodiment, Formula 4 [Chemical Formula] is a modified triarylmethane dye having the structure shown in wherein R1, R2, and R3 are independently selected from hydrogen or halogen, provided that only one of R1, R2, or R3 is halogen, provided that when R1 is halogen, R2 and R3 are hydrogen, and R1 is selected from fluorine, bromine, or iodine, when R2 is halogen, R1 and R3 are hydrogen, and R2 is selected from fluorine, chlorine, bromine, or iodine, when R3 is halogen, R1 and R2 are hydrogen, and R3 is selected from fluorine, bromine, or iodine, R4 and R5 are hydrogen, A1, A2, A1', and A2' are independently selected from hydrogen, alkyl, aryl, alkaryl, or alkoxy, provided that at least one of A1, A2, A1', and A2' is alkyl, aryl, alkaryl, or alkoxy, a modified triarylmethane dye.

[0017] In some embodiments, A1, A2, A1', and A2' are independently selected from hydrogen, alkyl, aryl, alkaryl, or alkoxy, provided that at least one of A1, A2, A1', and A2' is alkyl, aryl, alkaryl, or alkoxy.

[0018] In some embodiments, when R1 is halogen, A1, A2, A1', and A2' are independently selected from hydrogen, alkyl, aryl, alkaryl, or alkoxy.

[0019] When used in any embodiment of this specification, the term "halogen" refers to any element of the group including fluorine, chlorine, bromine, and iodine.

[0020] When used in any embodiment of this specification, the term "alkyl" represents both substituted and unsubstituted straight-chain and branched-chain carbon chains. Preferred alkyl groups are those containing 1 to 15 carbon atoms (i.e., C1-C 15 alkyl), more preferably C1-C 10 alkyl, and even more preferably C1-C5 alkyl. In some embodiments, alkyl is selected from methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, each of which may optionally be substituted. Preferably, alkyl is substituted or unsubstituted ethyl. Preferably, alkyl is unsubstituted ethyl.

[0021] When used in any embodiment of this specification, the terms "aryl" or "aromatic group" are used interchangeably to represent either a substituted or unsubstituted monocyclic or polycyclic system. The polycyclic ring may have two or more rings, where two carbons are shared between two adjacent rings ("fused" rings), where at least one of the rings is aromatic, and for example, the other rings may be cycloalkyl, cycloalkenyl, aryl, heterocycle, and / or heteroaryl. Preferred aryl groups are those containing 6 to 30 carbon atoms (i.e., C6-C 30 aryl), preferably those containing 6 to 20 carbon atoms (i.e., C6-C 20 aryl), and even more preferably those containing 6 to 12 carbon atoms (i.e., C6-C 12It is (aryl). In some embodiments, the aryl contains 6 carbon atoms, 10 carbons, or 12 carbons. Suitable aryl groups include phenyl, biphenyl, triphenyl, triphenylene, tetraphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene, preferably phenyl, biphenyl, triphenyl, benzylsulfonic acid, triphenylene, fluorene, and naphthalene, but are not limited thereto, and each of these may be optionally substituted.

[0022] When used in any embodiment herein, the term "aralkyl" refers to an alkyl group containing 1 to 15 carbon atoms having an aromatic group as a substituent. Further, the aralkyl group may be optionally substituted.

[0023] When used in any embodiment herein, the term "alkoxy" refers to any alkyl group bonded to an oxygen group. In some embodiments, alkoxy groups include, but are not limited to, ether, ester, amide, carboxylic acid, or alcohol. Also included in this definition are structures characterized by the periodic insertion of oxygen atoms into a carbon chain having less than 20 carbon atoms and terminating with an alcohol or alkyl group, such as polyethylene glycol, but are not limited thereto. A preferred alkoxy group is a polyethylene glycol chain, which preferably has 1 to 10 ethylene glycol repeating units, more preferably 2 to 8 ethylene glycol repeating units. In some embodiments, the polyethylene glycol chain contains 5 ethylene glycol repeating units.

[0024] In any embodiment herein, A1, A2, A1', and A2' provide a solubilizing group to the structure of Formula I. As used herein, the term "solubilizing group" refers to a terminal carboxylic acid, sulfonate, benzylsulfonic acid, ester, or alcohol group introduced to improve solubility in polar solvents (water, alcohol).

[0025] By selectively halogenating the dye molecule at the positions of R1 to R3, the electronic structure changes, the π-system becomes more susceptible to interruptions or breaks that cause color fading, and the decolorization rate is effectively regulated.

[0026] In some embodiments, by substituting the amine group, molecules such as the following can be prepared: i) A1 and A2 can be the same or different, ii) A1 and A2' can be the same or different, iii) A1 and A1' can be the same or different, iv) A2 and A1' can be the same or different, v) A2 and A2' can be the same or different, or vi) A1' and A2' can be the same or different.

[0027] As used herein, the term "optionally substituted" means that the group in question can be substituted at one or more positions with any one or combination of the elements listed below: halogen, hydrogen, alkyl, aryl, alkoxy, aralkyl, solubilizing group.

[0028] In any embodiment of the present specification, A1 and A1' are the same, and A2 and A2' are the same. In some embodiments, A1 and A1' are alkyl, and A2 and A2' are aryl. In some embodiments, A1 and A1' are C1-C5 alkyl, and A2 and A2' are C6-C 12 aryl. In some embodiments, A1 = A1' = ethyl, and A2 = A2' = benzenesulfonic acid.

[0029] In any embodiment of this specification, A1, A1’, A2, and A2’ are alkoxy. In some embodiments, A1, A1’, A2, and A2’ are polyethylene glycol (PEG). Preferably, A1, A1’, A2, and A2’ are, independently, polyethylene glycols having 1 to 10 ethylene glycol repeating units. Preferably, A1, A1’, A2, and A2’ are, independently, polyethylene glycols having 2 to 8 ethylene glycol repeating units. In some embodiments, A1, A1’, A2, and A2’ are polyethylene glycol chains containing 5 ethylene glycol repeating units. In some embodiments, A1, A1’, A2, and A2’ are all the same.

[0030] Non-limiting examples of the compounds according to the present invention are shown in Tables 1 to 4.

[0031] Table 1 [Chemical formula]

[0032] Table 2 [Chemical formula]

[0033] Table 3 [Chemical formula] In the formula, n is from 1 to 10, preferably from 2 to 8.

[0034] Table 4 [Chemical formula]

[0035] Materials and Methods Materials Acid Green 9 was purchased from TCI chemicals and used without further purification. N-Ethyl-N-benzylaniline-3'-sulfonic acid was purchased from AK Scientific. Ethoxylated aniline was purchased from Ethox Chemicals. Halogenated aldehyde and p-toluenesulfonic acid (PTSA) were all purchased from Sigma Aldrich. N,N-Dimethylformamide (DMF), ethanol, and chloranil were purchased from VWR. Deuterated solvents were purchased from Cambridge Isotope Laboratories Inc. Hydrogen peroxide stock solution was purchased from Evonik and diluted to 0.5% w / w with DI water before use.

[0036] Synthesis of metachloro acidic triarylmethane In a three-necked round-bottom flask equipped with a condenser, 2 equivalents of N-ethyl-N-benzylaniline-3'-sulfonic acid, 1 equivalent of PTSA, and DMF were combined and heated in an oil bath until the solid was completely dissolved. 1 equivalent of halogenated aldehyde was added, and the mixture was stirred overnight to obtain a leuco dye. 1 equivalent of chloranil was added to the crude mixture. After 2.5 hours, the round bottom was removed from the heat. The solvent was removed in vacuo, and the resulting solid was redissolved in methanol and purified by chromatography to obtain a pure dye species. [Chemical formula]

[0037] Synthesis of metachloro polyethylene glycol (PEG) triarylmethane In a beaker, 1 equivalent of ethanol was mixed with 3 equivalents of water, and the pH of the mixture was adjusted to 0.7 using concentrated HCl. In a three-necked round-bottom flask equipped with a condenser, 2 equivalents of ethoxylated aniline and 1 equivalent of halogenated aldehyde were dissolved in the acidic ethanol / water mixture. The mixture was heated and stirred to obtain a leuco dye. 1.1 equivalents of chloranil were added to the crude mixture. After 18 hours, the round bottom was removed from the heat. The solvent was removed in vacuo, and the dye was redissolved in methanol and purified by chromatography to obtain a pure dye species. [Chemical]

[0038] Fading Test The light absorption measurement was performed using a Shimadzu UV-VIS 1900i spectrometer. The dye was dissolved in non-buffered DI water to form a 10 mM stock solution.

[0039] To measure the fading rate of the dye under basic conditions, 25 μL of the dye stock solution was added to 10 mL of 0.1 M potassium phosphate buffer at pH = 8. Then, 3 mL of the diluted dye solution at pH = 8 was pipetted into a clean quartz cuvette and inserted into the spectrometer. The absorbance intensity at λmax was measured every second for 400 seconds for each dye tested.

[0040] To measure the dye sensitivity to hydrogen peroxide, 25 μL of the dye stock solution was added to 10 mL of DI water. 1.5 mL of the diluted stock solution was added to a clean quartz cuvette. 1.5 mL of 0.5% w / w hydrogen peroxide solution was added to the same cuvette. Then, the cuvette was vortexed briefly to mix uniformly and loaded into the spectrometer. The absorbance intensity at λmax was measured every second for 400 seconds for each dye tested.

[0041] NMR Property Evaluation 1 The 1H NMR sample was dissolved in methanol-d4 and scans were acquired using a 300 MHz NMR.

[0042] Mass Spectrometry Mass property evaluation data were obtained using a high-resolution mass spectrometer.

[0043] Results 1 1H NMR and high-resolution mass spectrometry (Figures 1 - 3 and Table 5 (below)) showed that the metachloro acidic triarylmethane had the mass and structure predicted theoretically.

[0044] 1By \(^1H\) NMR and high-resolution mass spectrometry (Figures 4 - 6 and Table 6 (below)), it was shown that the metachloro-PEG triarylmethane had the mass and structure predicted by theory.

[0045] In solution, both the metachloro-acidic triarylmethane and the metachloro-PEG triarylmethane were bluer than Acid Green 9, with a greenish tint. Figures 7 and Table 7 (below) show a distinct shift in the maximum absorbance and relative absorbance intensity between the metachloro-acidic triarylmethane, the metachloro-PEG triarylmethane, and Acid Green 9. Such differences in absorption spectra are likely to correspond to the perceived color changes in solution.

[0046] Both the metachloro-acidic triarylmethane and the metachloro-PEG triarylmethane showed a decrease in stability at alkaline pH compared to Acid Green 9. 25 μM solutions of both the metachloro-acidic triarylmethane and the metachloro-PEG triarylmethane at pH = 8 showed significant fading within a 400-second time window, while Acid Green 9 showed negligible fading under the same conditions (Figures 8 and Table 8 (below)).

[0047] Both the metachloro-acidic triarylmethane and the metachloro-PEG triarylmethane showed an increased rate of fading in hydrogen peroxide compared to Acid Green 9. Non-buffered solutions of both the metachloro-acidic triarylmethane and the metachloro-PEG triarylmethane showed significant fading within a 400-second time window when combined with 0.5% w / w hydrogen peroxide. Acid Green 9 showed negligible fading within the same time window when combined with such a low concentration of hydrogen peroxide (Figures 9 and Table 9 (below)).

[0048] [Table 5]

[0049] [Table 6]

[0050]

Table 7

[0051]

Table 8

[0052]

Table 9

[0053] Although the present invention has been specifically illustrated and described with reference to its preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims

1. Modified triarylmethane dye containing the structure shown in Formula 3 [Chemical Formula 3] wherein

2. R １ , R ２ , R ３ , R ４ , R ５ , R ６ , and R ７ are independently selected from hydrogen, halogen, C １ -C １６ alkyl, amino, nitro, methoxy, carboxy, aryl, alkoxy, or sulfonic acid. A １ , A ２ , A １ ’, and A ２ ’ are independently selected from hydrogen, alkyl, aryl, alkaryl, or alkoxy, provided that at least one of A １ , A ２ , A １ ’, and A ２ ’ is alkyl, aryl, alkaryl, or alkoxy, a modified triarylmethane dye.

3. R １ 、R ２ 、R ３ 、R ４ 、R ５ 、R ６ 、and R ７ are independently selected from hydrogen, halogen, C １ -C １６ alkyl, amino, nitro, methoxy, carboxy, aryl, alkoxy, or sulfonic acid, provided that at least one of R １ 、R ２ 、or R ３ is halogen, the modified triarylmethane dye according to claim 1.

4. R ４ and R ５ is hydrogen, the modified triarylmethane dye according to claim 1 or 2.

5. R ６ and R ７ The modified triarylmethane dye according to any one of claims 1 to 3, wherein is hydrogen.

6. A １ , A １ ’, A ２ , and A ２ ’ is an alkoxy group, the modified triarylmethane dye according to any one of claims 1 to 4.

7. A １ 、 A １ ’, A ２ 、 and A ２ ’ is polyethylene glycol, the modified triarylmethane dye according to claim 5.

8. A １ 、 A １ ’, A ２ 、 and A ２ ’ are independently polyethylene glycols having 1 to 10 ethylene glycol repeating units, the modified triarylmethane dye according to claim 6.

9. A １ 、 A １ ’, A ２ 、 and A ２ ’ are polyethylene glycols having five ethylene glycol repeating units, the modified triarylmethane dye according to claim 7.

10. R ２ The modified triarylmethane dye according to any one of claims 1 to 8, wherein R is a halogen.

11. R ２ The modified triarylmethane dye according to claim 9, wherein R is chlorine.

12. R １ and R ３ is hydrogen, the modified triarylmethane dye according to claim 9 or 10.

13. Modified triarylmethane dye containing the structure shown in Formula 4 【Chemical 4】 wherein

14. R １ 、 R ２ 、 R ３ 、 R ４ 、 and R ５ are independently selected from hydrogen, halogen, C １ - C １６ alkyl, amino, nitro, methoxy, carboxy, aryl, alkoxy, or sulfonic acid, provided that at least one of R １ 、 R ２ 、 or R ３ is halogen, A １ , A ２ , A １ ’, and A ２ ’ are independently selected from hydrogen, alkyl, aryl, alkaryl, or alkoxy, provided that at least one of A １ , A ２ , A １ ’, and A ２ ’ is alkyl, aryl, alkaryl, or alkoxy, a modified triarylmethane dye.

15. R １ 、 R ２ 、 R ３ 、 R ４ 、 and R ５ are independently selected from hydrogen, halogen, C １ - C １６ alkyl, amino, nitro, methoxy, carboxy, aryl, alkoxy, or sulfonic acid, provided that at least one of R １ , R ２ , or R ３ is halogen, the modified triarylmethane dye according to claim 12.

16. R １ , R ２ , or R ３ wherein only one of them is halogen, the modified triarylmethane dye according to claim 12 or 13.

17. (i) R １ When R ２ and R ３ are hydrogen, R １ is selected from fluorine, bromine, chlorine, or iodine, (ii) R ２ When R is halogen, R １ and R ３ are hydrogen, R ２ is selected from fluorine, bromine, chlorine, or iodine, or (iii) R ３ When R is halogen, R １ and R ２ are hydrogen, and R ３ is selected from fluorine, bromine, chlorine, or iodine,

18.

19. R １ The modified triarylmethane dye according to claim 14 or 15, wherein R is a halogen.

20. R ２ The modified triarylmethane dye according to claim 14 or 15, wherein R is halogen.

21. R ３ The modified triarylmethane dye according to claim 14 or 15, wherein R is halogen.

22. A １ and A １ ’ are the same, and A ２ and A ２ ’ are the same, the modified triarylmethane dye according to any one of claims 12 to 18.

23. A １ and A １ ’ is alkyl, and A ２ and A ２ ’ is aralkyl, the modified triarylmethane dye according to claim 19.

24. A １ and A １ ’ is C １ ~C ５ alkyl, and A ２ and A ２ ’ is C bonded to N via a crosslinked alkyl carbon ６ ~C １２ aryl, the modified triarylmethane dye according to claim 20.

25. A １ and A １ ’ is ethyl, and A ２ and A ２ ’ is benzenesulfonic acid, the modified triarylmethane dye according to claim 21.

26. R ２ The modified triarylmethane dye according to any one of claims 19 to 22, wherein R is a halogen.

27. R ２ The modified triarylmethane dye according to claim 23, wherein R is chlorine.

28. A １ 、 A １ ’, A ２ 、 and A ２ ’ is an alkoxy group, the modified triarylmethane dye according to any one of claims 12 to 18.

29. A １ 、 A １ ’, A ２ 、 and A ２ ’ are polyethylene glycols, the modified triarylmethane dye according to claim 25.

30. A １ 、 A １ ’, A ２ 、 and A ２ ’ are, independently, polyethylene glycols having 1 to 10 ethylene glycol repeating units, the modified triarylmethane dye according to claim 26.

31. A １ , A １ ’, A ２ , and A ２ ’ is polyethylene glycol having 5 ethylene glycol repeating units, the modified triarylmethane dye according to claim 27.

32. R ２ The modified triarylmethane dye according to any one of claims 25 to 28, wherein R is a halogen.

33. R ２ The modified triarylmethane dye according to claim 29, wherein R is chlorine.

34. R １ and R ３ is hydrogen, the modified triarylmethane dye according to claim 29 or 30.

35. Modified triarylmethane dye containing the structure shown in Formula 4 【Chemical 4】 wherein

36. R １ 、R ２ 、and R ３ is independently selected from hydrogen or halogen, provided that R １ 、R ２ 、or R ３ is halogen, provided that only one of R １ When R is a halogen, ２ R and ３ are hydrogen, and R １ is selected from fluorine, bromine, chlorine, or iodine, R ２ When R is halogen, １ R and ３ R are hydrogen, and R ２ is selected from fluorine, chlorine, bromine, or iodine, R ３ When R is a halogen, １ R and ２ R are hydrogen, and R ３ is selected from fluorine, bromine, chlorine, or iodine, R ４ and R ５ is hydrogen, A １ , A ２ , A １ ’, and A ２ ’ are independently selected from hydrogen, alkyl, aryl, alkaryl, or alkoxy, provided that at least one of A １ , A ２ , A １ ’, and A ２ ’ is alkyl, aryl, alkaryl, or alkoxy, a modified triarylmethane dye.

37. R １ The modified triarylmethane dye according to claim 32, wherein R is a halogen.

38. R ２ The modified triarylmethane dye according to claim 32, wherein R is a halogen.

39. R ３ The modified triarylmethane dye according to claim 32, wherein R is a halogen.

40. A １ and A １ ' are the same, and A ２ and A ２ ' are the same, the modified triarylmethane dye according to any one of claims 32 to 35.

41. A １ and A １ ’ is alkyl, and A ２ and A ２ ’ is aralkyl, the modified triarylmethane dye according to claim 36. ​ A １ and A １ ’ is C １ to C ５ alkyl, and A ２ and A ２ ’ is C bonded to N via a crosslinked alkyl carbon ６ to C １２ aryl, the modified triarylmethane dye according to claim 37. ​ A １ and A １ ’ is ethyl, and A ２ and A ２ ’ is benzenesulfonic acid, the modified triarylmethane dye according to claim 38. ​ R ２ The modified triarylmethane dye according to any one of claims 36 to 39, wherein R is a halogen. ​ R ２ The modified triarylmethane dye according to claim 40, wherein R is chlorine.

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