RU2703168C1 - Pigment for protective elements of multilayer articles based on substituted dithiolene complexes of nickel with asymmetric ligands - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemistry of pigments, particularly to production of versions of pigments based on compounds – substituted dithiolene complexes of nickel with asymmetric ligands. Method of producing pigment for protective elements of multilayer articles based on substituted dithiolene complexes of nickel with asymmetric ligands involves producing 1-R₂-3-R₁-thiocarbamide, where R₁ – aryl, and R₂ – alkyl C₁-C₁₈, cycloalkyl, allyl, propargyl, aralkyl, aryl, where R₁ is not equal to R₂. Then it is reacted with oxalyl chloride to form 1-R₂-3-R₁-2-thioxoimidazolidine-4,5-dione, is reacted with metallic nickel in the presence of Lawesson's reagent and the desired product is obtained.

EFFECT: obtaining a pigment for protective elements of multilayer articles, having high light resistance and good resistance to external environment and aggressive media.

2 cl, 1 dwg, 8 ex

Description

The invention relates to the chemistry of pigments, in particular, to the production of pigment variants based on compounds - substituted dithiene complexes of nickel with asymmetric ligands of the general formula 1:

where R ₁ is aryl, including 1- or 2-naphthyl, or phenyl, unsubstituted or containing at different positions of the benzene ring from 1 to 5 identical or different substituents of the type of straight or branched alkyl groups C ₁ -C ₁₈ , including partially or fully fluorinated and / or alkoxy groups, with straight or branched C ₁ -C ₁₈ alkyls, including partially or fully fluorinated, and / or phenyl, and / or one or more halogen atoms of fluorine, chlorine or bromine;

where R ₂ is a straight or branched C ₁ -C ₁₈ alkyl, including partially or completely fluorinated, C ₅ -C ₆ cycloalkyl, allyl, propargyl or aryl containing in different positions of the benzene ring from 1 to 5 identical or different substituents - C ₁ -C ₁₈ straight or branched alkyl groups, including partially or fully fluorinated and / or alkoxy groups, with C ₁ -C ₁₈ straight or branched alkyls, including partially or fully fluorinated, and / or phenyl, and / or one or more halogen atoms of fluorine, chlorine or bromine ; unbranched alkyl containing one or more oxygen bridges of the type (CH ₂ CH ₂ O) _n R in the chain, where n = 1-4, and R = methyl, ethyl or phenyl; aralkyl, where alkyl is a C ₁ -C ₄ normal alkyl chain, and aryl is unsubstituted phenyl or containing in various positions of the benzene ring from 1 to 3 normal C ₁ -C ₄ alkyl substituents, and / or one or more halogen atoms of fluorine, chlorine or bromine and / or alkoxy groups, with straight or branched C ₁ -C ₁₈ alkyls, including partially or fully fluorinated, and / or phenyl, with R ₁ not equal to R ₂ being IR absorbers, as well as the method of obtaining them, and may find application in creating means of protection against counterfeiting banknotes, about fiscal, accounting, and other important business and valuable documents, including such as a counterfeit valuable document, which is a banknote, passport, security paper, plastic card, multi-layer composite token, certificate, travel document, excise stamp, bill of exchange, diploma, driver’s license or other similar products with at least one security element made by the printing method.

The inventive pigment compounds, their properties and the production method are not described in the literature.

The inventive compounds have a structure related to dithiolene metal complexes of nickel with alkyl, cycloalkyl, aralkyl or aryl substituted imidazolidin-2-chalcogenone-4,5-dithionic ligands.

Such metal complexes are known from the prior art, in particular symmetric substituted nickel dithiolene complexes (EP 3067216 A1, publ. 09/14/2016; US 20114103635 A1, publ. 04/17/2014; US 2013234427 A1, publ. 09/12/2013) intensively absorb light in the near The IR regions practically do not absorb visible light, which makes them invisible to the human eye and is an important advantage, since most of the known infrared absorbers of other structures are dyes that intensively absorb in the visible region of the spectrum, which makes them unsuitable for the above special use.

For special use, IR absorbers are required that intensively absorb in the range of 800-1200 nm (ε≥50000 l mol ^-1 cm ^-1 ) and do not absorb, or weakly absorb in the visible region (ε≤10000 l mol ^-1 cm ^-1 ) .

In addition to the requirement for the absence of absorption in the visible spectrum, IR absorbers for counterfeiters must meet the stringent requirements for stability: heat resistance, light resistance and chemical stability with respect to chemicals and solvents.

International patent application WO 2008/086931, 07.24.2008, describes nickel dithiolene complexes with symmetric alkyl substituted imidazolidin-2-chalcogenone-4,5-dithionic ligands, for example, of the following structure:

which practically do not absorb in the visible region of the spectrum, have good light and heat resistance, but are not sufficiently resistant to chemicals and boiling water.

In the patent RU 2575644 publ. 02/20/2016, instead of N-alkyl substituents, N-aryl substituents (all four are the same) are used in the ligand, which made it possible to increase the stability of symmetrical nickel dithiene complexes with respect to chemicals and solvents without losing other advantages.

The structure of compounds belonging to the class of metal-dithiolene complexes, as well as their electronic structure and parameters describing this structure are also known (M. Area et al. Synthesis, X-ray crystal structure and spectroscopic characterization of the new dithiolene [Pd (Et2timdt) 2] and of its adduct with molecular diiodine [Pd (Et2timdt) 2] ⋅I2⋅CHCl3 (Et2timdt = monoanion of 1,3-diethylimidazolidine-2,4,5-trithione) J. Chem. Soc., Dalton Trans., 1998, 0, 3731-3736).

The use of substances to create pigments used in paint to protect products, and methods for creating protection against fake using pigments to create elements in multilayer products, are described in patents RU 2379194, publ. 01/20/2010, and RU 2425757, publ. 08/10/2011

At present, the possibility of creating such protection with the introduction of pigments, such as dithiylene metal complexes with asymmetric ligands, has not been practically studied.

However, despite the fact that the above proposals to some extent solved the problem of protection against counterfeiting of products, the disadvantage of these known solutions is that the rapidly changing requirements for product security determine the need for the creation and operational implementation of new technologies that can prevent counterfeiting of products.

The objective of the claimed invention is to develop a high degree of protection against counterfeiting by introducing a new pigment for the protective elements of multilayer products based on substituted dithiene complexes of nickel with asymmetric imidazolidine ligands, as well as a method for its preparation.

The technical result of the claimed invention consists in obtaining pigment for the protective elements of multilayer products with high light fastness and good resistance to environmental influences and aggressive environments.

The claimed invention ensures that the prints of paints with the above pigment based on these materials have high light resistance, good resistance to various types of organic solvents, solutions of acids, alkalis and sodium hypochlorite, hot water, solutions that simulate artificial sweat, as well as detergent solutions for household and industrial washing.

The solution of this problem is achieved by creating a pigment for the protective elements of multilayer products based on substituted dithiene complexes of nickel with asymmetric ligands of the general formula 1:

where R ₁ is aryl, including 1- or 2-naphthyl, or phenyl, unsubstituted or containing at different positions of the benzene ring from 1 to 5 identical or different substituents of the type of straight or branched alkyl groups C ₁ -C ₁₈ , including partially or fully fluorinated and / or alkoxy groups, with straight or branched C ₁ -C ₁₈ alkyls, including partially or fully fluorinated, and / or phenyl, and / or one or more halogen atoms of fluorine, chlorine or bromine;

where R ₂ is a straight or branched C ₁ -C ₁₈ alkyl, including partially or completely fluorinated, C ₅ -C ₆ cycloalkyl, allyl, propargyl or aryl containing in different positions of the benzene ring from 1 to 5 identical or different substituents - C ₁ -C ₁₈ straight or branched alkyl groups, including partially or fully fluorinated and / or alkoxy groups, with C ₁ -C ₁₈ straight or branched alkyls, including partially or fully fluorinated, and / or phenyl, and / or one or more halogen atoms of fluorine, chlorine or bromine ; unbranched alkyl containing one or more oxygen bridges of the type (CH ₂ CH ₂ O) _n R in the chain, where n = 1-4, and R = methyl, ethyl or phenyl; aralkyl, where alkyl is a C ₁ -C ₄ normal alkyl chain, and aryl is unsubstituted phenyl or containing in various positions of the benzene ring from 1 to 3 normal C ₁ -C ₄ alkyl substituents, and / or one or more halogen atoms of fluorine, chlorine or bromine and / or alkoxy groups, with straight or branched C ₁ -C ₁₈ alkyls, including partially or fully fluorinated, and / or phenyl, wherein R _{1 is} not equal to R ₂ .

In addition, the claimed method of producing pigment for the protective elements of multilayer products based on substituted dithiene complexes of nickel with asymmetric ligands of the general formula 1 according to claim 1, which consists in obtaining 1-R ₂ -3-R ₁ -thiocarbamide, where R ₁ - aryl, a R ₂ - alkyl C ₁ -C ₁₈ , cycloalkyl, aralkyl, aryl, wherein R _{1 is} not equal to R ₂ , it is reacted with oxalyl chloride to form 1-R ₂ -3-R ₁ -2-thioxoimidazolidin-4 , 5-dione, is reacted with metallic nickel in the presence of a Lawesson reagent and the desired product is obtained.

The synthesis of the proposed new dithiolene complexes of Nickel of General formula 1 is carried out in three stages according to the following scheme:

where R ₁ is aryl, R ₂ is C ₁ -C ₁₈ alkyl, cycloalkyl, allyl, propargyl, aralkyl, aryl, wherein R _{1 is} not equal to R ₂ .

The starting compounds for the preparation of new organic IR absorbers of the general formula 1 are R ₁ -isothiocyanate and an amine of the formula R ₂ NH ₂ , where R ₁ is aryl, and R ₂ is C ₁ -C ₁₈ alkyl, cycloalkyl, allyl, propargyl, aralkyl, aryl, wherein R _{1 is} not equal to R ₂ , which are reacted according to the known method to form 1-R ₂ -3-R ₁ -thiocarbamide, which is then reacted with oxalyl chloride to form 1-R ₂ -3-R ₁ - 2-thioxoimidazolidine-4,5-dione (pre-ligand), which, in turn, under the action of the Lawesson reagent in the presence of metallic nickel allows Luciano claimed ditiolenovye nickel complexes with asymmetric ligands of general formula 1.

The structure of the inventive nickel complexes of the general formula 1 and intermediates obtained is confirmed by elemental analysis and spectral characteristics (examples 1-8).

Example 1

Obtaining bis (1-n-butyl-3-phenylimidazolidine-2,4,5-trition) nickel - compound (1):

Example 1A Stage 1 - obtaining 1-n-butyl-3-phenylthiocarbamide.

In a 250 ml flask equipped with a magnetic stirrer, two-horned fortoss and a dropping funnel, 50 ml of dry tetrahydrofuran (THF) and 1.66 g (22.8 mmol) of n-butylamine were placed, 2.7 ml were slowly added dropwise with stirring (3, 08 g, 22.8 mmol) of phenylisothiocyanate, the clear solution was left for several hours, then the solvent was removed, the viscous oil gradually crystallized with the addition of ether. Got a white crystalline substance with T _PL = (62-64) ° C. Yield 4.72 g (99.5%).

¹ H NMR spectrum (300 MHz, CDCl ₃ ) δ, ppm (KSSV, Hz): 0.92 (t, 3H, CH ₃ , ³ J = 7.3), 1.33 (m, 2H, CCH ₂ , ³ J = 7.3), 1.56 (m, 2H, CCH ₂ , ³ J = 7.3; 7.0), 3.62 (2H, NCH ₂ , ³ J = 7.0).

Example 1B Stage 2 - obtaining 1-n-butyl-3-phenyl-2-thioxoimidazolidine-4,5-dione.

To a solution of 8.2 g (39.4 mmol) of 1-n-butyl-3-phenylthiocarbamide in 70 ml of dry CH ₂ Cl _{2 was} slowly added dropwise a solution of 8.55 g (39.4 mmol) of oxalyl chloride in 10 ml of dry CH ₂ Cl ₂ . Boiled for 12 hours, the yellow transparent solution was evaporated and 8.88 g of product was obtained with _Tm = (115-116) ° C.

Found,%: C 70.69; H, 4.21. C ₃₀ H ₂₂ O ₈ . Calculated,%: C 70.58; H 4.34; About 25.07.

¹ H NMR spectrum (300 MHz, CD Cl ₃ ) δ, ppm (KSSV, Hz): 1.00 (tr, 3H, CH ₃ , ³ J = 7.3), 1.43 (2H, CCH ₂ , ³ J = 7.3; 7.6), 1.77 (m, 2H, CCH ₂ , ³ J = 7.3 ; 7.6), 4.06 (t, 2H, NCH ₂ , ³ J = 7.5), 7.33 (d, 2H arom., ³ J = 7.9), 7.56 (t, 2H arom., ³ J = 7.7), 7.58 ( t, 1H arom, 7.7).

Example 1B Stage 3 - obtaining bis (1-n-butyl-3-phenylimidazolidine-2,4,5-trition) nickel (1).

The reaction flask and solvent were purged with argon. Subsequently, the synthesis was also conducted under argon. To a boiling solution of 8.8 g (34.4 mmol) of 1-n-butyl-3-phenyl-2-thioxoimidazolidin-4,5-dione in 300 ml of dry toluene, 15.28 g (37.8 mmol) of Lawesson's reagent was added and boiled for 4-5 minutes, then 1.01 g (17.2 mmol) of nickel metal powder was quickly added and boiled for another 1 hour. A precipitate of dark brown crystals fell in hot toluene. Yield: 3.2 g (29.3% by weight), _mp about 300 ° C.

The absorption maximum of complex (1) is observed at 1020 nm, ε = 50,000 l mol ¹ cm ¹ (methylene chloride), in the visible region (400-800 nm), the molar extinction coefficient did not exceed 8000 l mol ^-1 cm ^-1 .

Example 2

Obtaining bis (1-n-propyl-3-phenylimidazolidine-2,4,5-trition) nickel - compound (2):

Example 2A Stage 1 - obtaining 1-n-propyl-3-phenylthiocarbamide.

Analogously to example 1A, in a molar ratio of 1: 1, propylamine was reacted with phenylisothiocyanate. Got a white crystalline substance with T _PL ⁼ (60-61) ° C. Yield 4.5 g (91.8%).

Example_2B. Step 2 — Preparation of 1-n-propyl-3-phenyl-2-thioxoimidazolidin-4,5-dione.

Analogously to example 1B at a molar ratio of 1: 1, 1-n-propyl-3-phenylthiocarbamide was reacted with oxalyl chloride. Got a yellow crystalline product with T _PL = (136-138) ° C. Yield 4.9 g (96.0%).

¹ H NMR spectrum (300 MHz, CDCI ₃ ) δ, ppm (KSSV, Hz): 1.03 (t, 3H, CH ₃ , ³ J = 7.4), 1.82 (m, 2H, CH ₂ , ³ J = 7.5), 4.03 (t, 2H, NCH ₂ , ³ J = 7.5) 7.34 (m, 2H, arom.); 7.51 (m, 3H arom.).

Example 2B Stage 3 - obtaining bis (1-n-propyl-3-phenylimidazolidine-2,4,5-trition) nickel (2).

Analogously to example 1B, with a 10% molar excess of Lawesson's reagent and the corresponding amount of metallic nickel, dark brown crystals of the nickel complex were obtained (2). Yield 1.2 g (48.0%), _mp about 300 ° C. The maximum absorption of complex (2) is observed at 1016 nm, ε = 13800 l mol ^-1 cm ^-1 (methylene chloride), in the visible region (400-800 nm), the molar extinction coefficient did not exceed 8000 l mol ^-1 cm ^-1 .

Example 3

Obtaining bis (1-n-hexyl-3-phenylimidazolidine-2,4,5-trition) nickel - compound (3):

All three stages of the synthesis process of the Nickel complex (3) was carried out similarly to examples 1-2. Almost black crystals of the nickel complex were obtained (3). Yield 1.32 g (25.8%), T _mp = (274-277) ° C. The absorption maximum of complex (3) is observed at 1011 nm, ε = 90,000 l mol ^-1 cm ^-1 (methylene chloride), in the visible region (400-800 nm), the molar extinction coefficient did not exceed 8000 l mol ^-1 cm ^-1 .

Example 4

Obtaining bis (1-n-octyl-3-phenylimidazolidine-2,4,5-trition) nickel - compound (4):

All three stages of the synthesis process of the Nickel complex (4) was carried out similarly to examples 1-3. Almost black dark brown crystals of the nickel complex were obtained (4). Yield 1.5 g (31.0%), T _mp = (272-276) ° C. The absorption maximum of complex (4) is observed at 1010 nm, ε = 84000 l mol ^-1 cm ^-1] (methylene chloride), in the visible region (400-800 nm), the molar extinction coefficient did not exceed 8000 l mol ^-1 cm ^-1 .

Example 5

Obtaining bis (1-cyclohexyl-3-phenylimidazolidine-2,4,5-trition) nickel - compound (5):

All three stages of the synthesis process of the Nickel complex (5) was carried out similarly to examples 1-4. Almost black dark brown crystals of the nickel complex were obtained (5). The yield of about 1%, T _PL more than 300 ° C. The absorption maximum of complex (5) is observed at 1018 nm; ε is not determined.

Example 6

Obtaining bis (1-benzyl-3-phenylimidazolidine-2,4,5-trition) nickel - compound (6):

Example 6A Stage 1 - obtaining 1-benzyl-3-phenylthiocarbamide.

3.0 ml (0.025 mol) of phenyl isothiocyanate and 3.0 ml (0.027 mol) of benzylamine were poured into a flat-bottomed flask containing 20 ml of dioxane and stirred on a magnetic stirrer at room temperature for 3 hours. It was filtered, washed with dioxane and then hexane. The product is dried. Received 4.1 g (67.8% of theoretical) of a white powder of 1-benzyl-3-phenylthiocarbamide with T _PL = (192-195) ° C.

Example 6B Stage 2 - obtaining 1-benzyl-3-phenyl-2-thioxo-imidazolidine-4,5-dione.

3.0 g (12.4 mol) of the obtained 1-benzyl-3-phenylthiocarbamide and 1.57 g (0.012 mol) of oxalyl chloride were boiled for 4 hours in 20 ml of dry toluene. The reaction mass was cooled, the precipitate was filtered off, the product was dissolved in benzene, precipitated with hexane and dried in a desiccator over paraffin. Received 2.2 g (60.0% of theoretical) of an orange-yellow precipitate of the product with T _PL = (192-195) ° C.

Example 6B Stage 3 - obtaining bis (1-benzyl-3-phenylimidazolidine-2,4,5-trition) nickel (6).

3.4 g of Lawesson's reagent (8.4 mmol) was placed in a 250 ml conical flask equipped with forstoss with a dropping funnel and a reflux condenser with a calcium chloride tube. 50 ml of dry toluene, previously purged with argon, were added, and the contents were heated to boiling with stirring on a magnetic stirrer. A solution of 2.2 g (7.5 mmol) of 1-benzyl-3-phenyl-2-thioxoimidazolidine-4,5-dione in 10 ml of dry toluene flushed with argon was added via a dropping funnel. After 8 minutes, 0.21 g of Ni powder (3.6 mmol) was added and boiled for another 1 hour. The hot solution was decanted and filtered through a dense filter. Benzene was added to the residue in the flask, the precipitate was filtered off and washed with benzene. The precipitate was dried in a desiccator over paraffin. 1.5 g (56.4% of theory) of dark brown crystals of the nickel complex were obtained (6). The absorption maximum of complex (6) is observed at 1010 nm; ε is not determined due to poor solubility.

Example 7

Obtaining bis [1- [2- (4-fluorophenyl) ethyl] -3-phenyl-imidazolidine-2,4,5-trition] nickel - compound (7):

Example 7A Step 1 — Preparation of [1- [2- (4-fluorophenyl) ethyl] -3-phenylthiocarbamide.

In a 50 ml flask equipped with a magnetic stirrer, two-horn forestoss and a dropping funnel, 10 ml of dry tetrahydrofuran (TFH) and 2.2 ml (2.33 g, 16.75 mmol) of 2- (4-fluorophenyl) ethylamine were placed, with while stirring, a solution of 3 ml (3.30 g, 25 mmol) of phenylisothiocyanate in 5 ml of dry THF was slowly added dropwise and further stirred at room temperature for 5 hours. The solvent was distilled off on a rotary evaporator, a crystalline white precipitate was washed from the starting materials with light petroleum ether. Received 4.12 g (96.0%) of a white crystalline powder with T _PL = (64-65) ° C.

Example 7B Step 2 — Synthesis of [1- [2- (4-fluorophenyl) ethyl] -3-phenyl-2-thioxoimidazolidine-4,5-dione.

2.7 g (9.9 mmol) of 1- (1-ethyl-4-fluorophenyl) -3-phenylthiocarbamide and 20 ml of dry CH ₂ Cl were placed in a two-necked round bottom flask equipped with a dropping funnel and a reflux condenser with a calcium chloride tube. ₂ , a solution of 1 ml (1.455 g, 12 mmol) of oxalyl chloride in 5 ml of dry CH ₂ Cl ₂ was added dropwise and boiled for 5 hours. The reaction mass was cooled, the solvent was removed on a rotary evaporator, the residue was washed with light petroleum ether. Received 2.97 g (91.0%) of a yellow crystalline powder, luminescent with yellow-green light under UV - illumination with T _PL = (136-138) ° C.

Example 7B Stage 3 - synthesis of bis [1- [2- (4-fluorophenyl) ethyl] -3-phenyl-imidazolidine-2,4,5-trition] nickel (7).

2.46 g (7.5 mmol) of 1- [2- (4-fluorophenyl) ethyl] -3-phenyl-2-thioxoimidazolidine- were placed in a 250 ml flat-bottomed conical flask equipped with a two-horn forestoss with a reflux condenser and a calcium chloride tube. 4,5-dione and 80 ml of dry toluene, previously purged with argon for 20 minutes. Subsequently, the synthesis was also carried out under argon. It was brought to a boil with stirring on a magnetic stirrer and 3.33 g (8.25 mmol) of Lawesson's reagent was poured into the boiling solution. After 6 minutes, a solution of 0.242 g (4.1 mmol) of Ni powder was added and boiled for 1.5 hours. Filtered hot. The precipitate of the complex was dried in a desiccator over paraffin. Received 0.53 g (18.0%) of a brown powder with T _PL more than 300 ° C. The absorption maximum of complex (7) is observed at 1015 nm, ε is not determined due to poor solubility.

Example 8

Obtaining bis1- [2- (3,4-dimethoxyphenyl) ethyl] -3-phenyl-imidazolidine-2,4,5-trition] nickel - compound (8):

Example 8A Step 1 — Synthesis of 1- [2- (3,4-dimethoxyphenyl) ethyl] -3-phenylthiocarbamide.

In a round bottom flask equipped with a magnetic stirrer, two-horn forestoss and a dropping funnel, 10 ml of dry tetrahydrofuran (TFH) and 2.9 ml (17.2 mmol) of 2- (3,4-dimethoxyphenyl) ethylamine were placed, while solution 2 was slowly added dropwise with stirring , 0 ml (2.26 g, 16.7 mmol) of phenylisothiocyanate in 4 ml of dry THF and further stirred at room temperature for 5 hours. The solvent was distilled off on a rotary evaporator, the crystalline white residue was washed from the starting materials with light petroleum ether. Received 5.04 g (95.4%) of a white crystalline powder with T _PL = (58-60) ° C.

¹ H NMR spectrum (300 MHz, CDCl ₃ ) δ, ppm 2.87 (t, 2H, NCH ₂ , ³ J = 6.7), 3.83 (s, 3H, OCH ₃ ), 3.90 (t, 2H, ArCH ₂ , ³ J = 6.6), 6.02 (br.s, 1H, NH) , 6.66 (d, 1H arom., ³ J = 8.6), 6.68 (s, 1H arom., ³ J = 8.6), 7.01 (d, 2H arom., ³ J = 7.5) 7.26 (t, 1H arom., ³ J = 7.6), 7.34 (t, 2H arom., ³ J = 7.1), 7.79 (br s, 1H, NH).

Example 8B. Stage 2 - synthesis of 1- [2- (3,4-dimethoxyphenyl) ethyl] -3-phenyl-2-thioxoimidazolidine-4,5-dione.

In a two-necked round bottom flask equipped with a dropping funnel and a reflux condenser with a calcium chloride tube, 2.7 g (8.53 mmol) of 1- [2- (3,4-dimethoxyphenyl) ethyl] -3-phenylthiocarbamide and 20 ml of dry CH _{2 were} placed Cl ₂ , a solution of 1.455 g (11.45 mmol) of oxalyl chloride in 5 ml of dry CH ₂ Cl ₂ was added dropwise and boiled for 5 hours. The reaction mass was cooled, the solvent was removed on a rotary evaporator, the residue was washed with light petroleum ether. Received 2.91 g (85.3%) of a yellow crystalline powder, luminescent with yellow-green light under UV light with T _PL = (145-146) ° C.

¹ H NMR spectrum (300 MHz. CDCI ₃ ) δ, ppm (KSSV, Hz): 3.04 (t, 2H, CH ₂ , ³ J = 7.9), 3.86 (s, 3H, OCH ₃ ), 3.91 (s, 3H, OCH ₃ ), 4.28 (t, 2H, CH ₂ , ³ J = 7.7), 6.83 (m, 3H, arom.), 7.30 (m, 2H arom.), 7.56 (m, 3H arom.).

Example 8B Stage 3 - synthesis of bis [1- [2- (3,4-dimethoxyphenyl) ethyl] -3-phenylimidazolidine-2,4,5-trition) nickel (8).

4.0 g (10 mmol) of 1- [2- (3,4-dimethoxyphenyl) ethyl] -3-phenyl-2-thioxo- was placed in a 250 ml flat-bottomed conical flask equipped with a two-horn forestoss with a reflux condenser and a calcium chloride tube. imidazolidine-4,5-dione and 120 ml of dry toluene, previously purged with argon for 20 minutes. Subsequently, the synthesis was also carried out under argon. It was brought to a boil with stirring on a magnetic stirrer and 4.8 g (11.88 mmol) of Lawesson's reagent were poured into the boiling solution. After 5.5 minutes, a solution of 0.35 g (5.94 mmol) of Ni powder was added and boiled for 1 hour 40 minutes. Filtered hot. The black precipitate of the complex was dried in a desiccator over paraffin. 0.7 g (18.0%) was obtained, which was further stirred on a magnetic stirrer in 30 ml of benzene, filtered and dried in a desiccator over paraffin. Received 0.6 g (13.9%) of black powder with T _PL more than 300 ° C.

The absorption maximum of complex (8) is observed at 1016 nm, ε is not determined due to poor solubility.

As can be seen from the examples, the proposed method for producing the claimed compounds is quite technologically advanced, and the substances used for their synthesis are commercially available compounds.

The absorption spectra of the synthesized complexes and their physicochemical properties were studied.

It was found that the maxima in the absorption spectra of all the obtained compounds (1–8) in methylene chloride solutions (CH ₂ Cl ₂ ) are in the region (1000–1018 nm), and the molar extinction coefficients reach 90,000 l mol ^–1 cm ^–1 the interval (13000-90000) l mol ^-1 cm ^-1 . In the visible region of the claimed compounds practically do not absorb. A typical absorption spectrum is shown in FIG. one.

Most of the claimed complexes are soluble in polar organic solvents, such as acetone, methanol, ethanol, tetrahydrofuran, chloroform, and are not soluble in water.

Ink impressions based on these complexes have high light fastness, good resistance to various types of organic solvents, solutions of acids, alkalis and sodium hypochlorite, hot water, solutions simulating artificial sweat, as well as detergent solutions for household and industrial washing.

Thus, as can be seen from the above data, the claimed compounds are intensively absorbed in the near infrared region of the spectrum and practically do not absorb in the visible region, which allows them to be used as infrared absorbers when creating protection against banknote counterfeiting, office, accounting and other important business and other documentation, which is, for example, a banknote, passport, security paper, plastic card, multi-layer composite token, certificate, travel document, excise stamp, bill of exchange, diploma, identity card or other similar products with at least one security element made by the printing method.

Claims (5)

1. The pigment for the protective elements of multilayer products based on substituted dithiene complexes of nickel with asymmetric ligands of the general formula 1:

where R ₁ is aryl, including 1- or 2-naphthyl, or phenyl, unsubstituted or containing at different positions of the benzene ring from 1 to 5 identical or different substituents of the type of straight or branched C ₁ -C ₁₈ alkyl groups, including partially or fully fluorinated and / or alkoxy groups, with straight or branched C ₁ -C ₁₈ alkyls, including partially or fully fluorinated, and / or phenyl, and / or one or more halogen atoms of fluorine, chlorine or bromine; where R ₂ is a straight or branched C ₁ -C ₁₈ alkyl, including partially or completely fluorinated, C ₅ -C ₆ cycloalkyl, allyl, propargyl or aryl containing in different positions of the benzene ring from 1 to 5 identical or different substituents - C ₁ -C ₁₈ straight or branched alkyl groups, including partially or fully fluorinated and / or alkoxy groups, with C ₁ -C ₁₈ straight or branched alkyls, including partially or fully fluorinated, and / or phenyl, and / or one or more halogen atoms of fluorine, chlorine or bro and; unbranched alkyl containing one or more oxygen bridges of the type (CH ₂ CH ₂ O) _n R in the chain, where n = 1-4, and R = methyl, ethyl or phenyl; aralkyl, where alkyl is a C ₁ -C ₄ normal alkyl chain, and aryl is unsubstituted phenyl or containing in various positions of the benzene ring from 1 to 3 normal C ₁ -C ₄ alkyl substituents, and / or one or more halogen atoms of fluorine, chlorine or bromine and / or alkoxy groups, with straight or branched C ₁ -C ₁₈ alkyls, including partially or fully fluorinated, and / or phenyl, wherein R _{1 is} not equal to R ₂ . 2. A method of producing a pigment for the protective elements of multilayer products based on substituted nickel dithiolene complexes with asymmetric ligands of the general formula 1 according to claim 1, which consists in obtaining 1-R ₂ -3-R ₁ -thiocarbamide, where R ₁ is aryl , a R ₂ is C ₁ -C ₁₈ alkyl, cycloalkyl, allyl, propargyl, aralkyl, aryl, and R _{1 is} not equal to R ₂ , it is reacted with oxalyl chloride to form 1-R ₂ -3-R ₁ -2-thioxoimidazolidine -4,5-dione, is reacted with metallic nickel in the presence of a Lawesson reagent and obtain the target product.

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