RU2788650C2 - Asymmetrical luminescent donor-acceptor molecules based on triphenylamine-thiophene block with different electron-acceptor groups and their production method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: group of inventions relates to the field of a chemical technology of organic compounds. New asymmetrical luminescent donor-acceptor molecules of the general formula (I) are presented. In another embodiment, a method for the production of new asymmetrical luminescent donor-acceptor molecules of the general formula (I) is provided.

EFFECT: group of inventions provides new compounds having efficient light absorption in polymer polystyrene matrices in the range from 470 to 620 nm with high values of quantum photoluminescence yield from 20 to 50% in the range from yellow (560 nm) to red (710 nm) spectrum region, as well as high thermal resistance.

11 cl, 4 dwg, 1 tbl, 2 ex

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The claimed invention relates to the field of chemical technology of organic compounds and can find industrial application in obtaining new functional light-converting and light-emitting organic materials in optics and optoelectronics, which have both effective light absorption in the visible part of the spectrum and effective photoluminescence in the long-wavelength range of the spectrum (from yellow to red) combined with high thermal stability. More specifically, the invention relates to the production of new organic luminescent materials, which are asymmetric molecules of the donor-acceptor type based on electron-donor triphenylamine, or its alkyl-, or alkoxy-derivatives, bound through a π-conjugated thiophene fragment with a terminal electron-withdrawing group of various nature.

BACKGROUND OF THE INVENTION

Within the framework of the claimed invention, asymmetric donor-acceptor molecules include organic compounds that have one electron-donating triphenylamine, or dialkyltriphenylamine, or dialkoxytriphenylamine fragment, connected through a π-conjugated thiophene spacer (π-spacer) with N-alkyl- or N-phenylrhodanine, N -alkyl- or N-phenyldicyano-rhodanine, dicyanoindanone, alkyl- or phenylcyanoether and 4-methyl-, 4-methoxy- or 4-nitrophenylacrylonitrile electron-withdrawing groups.

Historically, a similar concept of using triphenylamine derivatives of various architectures, coupled through a π-conjugated through a thiophene spacer with electron-withdrawing substituents, was used primarily in the development of new functional materials for organic photovoltaics (J. Am. Chem. Soc., 2006, 128, 10, 3459-3466) and was mainly focused on obtaining symmetrical trisubstituted star-shaped derivatives of triphenylamine (Faraday Discuss., 2014,174, 313-339). However, the synthesis of star-shaped molecules is relatively difficult, which results in high cost of final compounds and devices based on them. These shortcomings are free from similar but asymmetric donor-acceptor molecules characterized by simple synthesis, which makes this class of compounds more promising for practical applications (Phys. Chem. Chem. Phys. 2010, 12, 11715–11727; Chem. Commun. 2012, 48 , 8907–8909).

Closest in structure to the claimed asymmetric luminescent donor-acceptor molecules include similar compounds that also have triphenylamine as an electron-donating fragment, thiophene as a π-spacer, but dicyanovinyl groups as an electron-withdrawing fragment. Such asymmetric molecules were first published in (Phys. Chem. Chem. Phys. 2010, 12, 11715–11727; Chem. Commun. 2012, 48, 8907–8909), where their optical properties were described in the first paper, and in later work they were used as an active layer component of photovoltaic cells.

Further development of such asymmetric donor-acceptor materials is described in (Adv. Funct. Mater. 2017, 1704039; international application WO2019057196, publication date 03/28/2019), where such asymmetric molecules were studied from the standpoint of light-emitting materials aimed primarily at further practical application in biological imaging systems as a luminescent contrast agent for combined transmission and emission tomography. In this work, the authors also used the mentioned dicyanovinyl electron-withdrawing groups, but varied the substituents on the triphenylamine fragments.

Patents RU2667362C2 (publication date 09/19/2018) and RU2694209C1 (publication date 07/09/2019) disclose similar asymmetric molecules, but with a phenyl and p-fluorophenyl substituent at the dicyanovinyl group, instead of a hydrogen atom. However, the luminescent properties of such materials have not been studied and described.

A molecular architecture similar to early publications, but using indanedione electron-withdrawing groups instead of the original dicyanovinyl groups, was also described in (ChemPlusChem 2016, 81, 637–645).

It should be noted that the luminescent properties of molecules in all the works mentioned above have not been studied at all or have been studied partially, only in dilute solutions. However, it is well known that the optical characteristics of organic materials in their solutions can radically differ from their properties in a block or polymer matrix, i.e. in the form in which they are actually used in most optoelectronic devices. Thus, the real potential for the practical application of the aforementioned asymmetric luminescent donor-acceptor lamps remains unknown. In addition, there are no examples of compounds with a similar structure and immediately possessing a set of properties that are important for practical application (high quantum yield of photoluminescence in a polymer matrix with emission and absorption in a wide spectral range, high thermal stability, etc.).

As a rule, the synthesis of such compounds is based on carrying out the Knoevenagel condensation reaction between malononitrile and an aldehyde obtained in advance (Chem. Commun. 2012, 48, 8907–8909; international application WO2019057196, publication date 03/28/2019):

However, such asymmetric luminescent donor-acceptor molecules with N-alkyl- or N-phenylrhodanine, N-alkyl- or N-phenyldicyanorhodanine, dicyanoindanone, alkyl- or phenylcyanoether and 4-methyl-, 4-methoxy- or 4-nitrophenylacrylonitrile electron-withdrawing groups , as well as the method of obtaining them are not described. Obtaining such molecules under the conditions of the Köwenagel condensation reaction is not an entirely trivial task, since can be associated with a number of difficulties caused by different reactivity of the initial aldehyde substrates and precursors of electron-withdrawing groups, steric factors during their interaction, and chemical stability under the reaction conditions. In addition, the above-mentioned methods for the synthesis of such molecules are distinguished by their low technology, since use chlorine-containing organic solvents and additional components for catalysis.

SUMMARY OF THE INVENTION

The technical problem to be solved by the claimed invention is the expansion of the range of asymmetric luminescent donor-acceptor molecules.

The technical result achieved in the implementation of the claimed invention is to obtain new luminescent donor-acceptor molecules and materials based on them, which have efficient light absorption in polymer polystyrene matrices in the range from 470 to 620 nm, high values of the quantum yield of photoluminescence from 20 to 50% in the range from yellow (560 nm) to red (710 nm) spectral region, as well as high thermal stability.

This application proposes an expansion of the range of asymmetric luminescent donor-acceptor molecules by using new electron-withdrawing groups, such as N-alkyl- or N-phenylrhodanine, N-alkyl- or N-phenyldicyanorhodanine, dicyanoindanone, alkyl- or phenylcyanoether and 4-methyl-, 4-methoxy- or 4-nitrophenylacrylonitrile electron-withdrawing groups.

An essential feature of the proposed method for obtaining asymmetric luminescent donor-acceptor molecules is its higher manufacturability due to the use of pyridine both as a solvent and as a catalyst for this reaction.

To solve the technical problem, various asymmetric donor-acceptor molecules of general formula (I) were obtained:

(I),

(I)

where R1 denotes H or a substituent selected from the range: linear C ₁ -C ₁₂ or branched C ₃ -C ₂₀ alkyl groups; linear C ₁ -C ₁₂ or branched C ₃ -C ₂₀ alkyl groups separated by at least one oxygen atom;

EWG stands for electron withdrawing groups, selected from the range:

N-alkyl- or N-phenyl- derivative of 2-thioxo-1,3-thiazolidin-4-one of general formula (II-a):

(II-a),

(II-a),

N-alkyl- or N-phenyl- derivative of 2-(dicyanomethylene)-1,3-thiazolidin-4-one of general formula (II-b):

(II-b),

(II-b),

alkyl or phenyl cyanoacetate derivative of general formula (II-c):

(II-c),

(II-c),

4-methylphenyl-, 4-methoxyphenyl- or 4-nitrophenyl- acetonitrile derivative of general formula (II-d):

(II-d),

(II-d),

3-(dicyanomethylene)indan-1-one derivative of general formula (II-e):

(II-e),

(II-e),

where R2 are linear C ₁ -C ₆ , or branched C ₃ -C ₁₂ alkyl, or cyclic aromatic phenyl groups; R3 are methyl, methoxy, or nitro substituents.

The optical properties of the new asymmetric luminescent donor-acceptor molecules can vary over a wide range depending on the chosen electron-withdrawing group EWG. This can be illustrated, for example, by both absorption spectra and their luminescence spectra in polystyrene polymer matrices (Fig. 1) according to Examples 2-5, 7. Some optical characteristics of luminescent asymmetric donor-acceptor molecules, as well as their thermal stability, are given in Table 1 for Examples 2-9. As can be seen from the spectral data, the claimed new asymmetric donor-acceptor molecules have an intense absorption spectrum in the range from 470 to 620 nm. Polystyrene polymer films obtained with the addition of asymmetric donor-acceptor molecules demonstrate efficient emission in a wide spectral range from yellow (560 nm) to red (710 nm) spectral region with high values of photoluminescence quantum yields, from 20 to 50%. By high quantum yield in the context of this invention is meant a photoluminescence quantum yield of at least 20%. The variation of both donor fragments and various electron-withdrawing groups, presented in the framework of the claimed invention, allows you to fine-tune the complex of physico-chemical properties of the materials obtained on their basis. The data given are examples only and do not limit the characteristics of the claimed asymmetric luminescent donor-acceptor molecules.

Also, one of the distinguishing features of the claimed asymmetric donor-acceptor molecules is their high thermal stability, defined in the framework of this invention as the temperature of loss of 5% of the initial mass when the substance is heated in an inert atmosphere. This temperature for various special cases is at least 300 ^° C, mainly 340 ^° C. The thermogravimetric analysis (TGA) data for Examples 2-9 are shown in Table 1. The data given are only examples and do not limit the characteristics of the declared asymmetric donor-acceptor molecules.

The technical problem is also solved by developing an efficient scheme for the synthesis of new asymmetric luminescent donor-acceptor molecules, which is reduced to obtaining the necessary aldehydes, general form (III), with further Knoevenagel condensation reaction (J. March, Advanced Organic Chemistry: Reactions, Mechanisms, and Structure , McGraw-Hill, New York, NY: 1968, pp. 693, 697-698).

(III)

(III)

Thus, the key step for obtaining the proposed asymmetric luminescent donor-acceptor molecules is the condensation reaction between an aldehyde selected from a number of compounds of general formula (III) and various EWG precursors having active methylene groups, selected from a number (IVa-e):

(IV-a);

(IV-b);

(IV-c);

(IV-d);

(IV-a);

(IV-b);

(IV-c);

(IV-d);

(IV-e),

(IV-e),

where R2 are linear C ₁ -C ₆ , or branched C ₃ -C ₁₂ alkyl, or cyclic aromatic phenyl groups; R3 are methyl, methoxy, or nitro substituents.

In the context of the present invention, the Knoevenagel condensation reaction between an aldehyde selected from the series of compounds of general formula (III) and an EWG precursor selected from the series of compounds (IVa-e) results in the substitution of the carbonyl group in the aldehyde to form an unsymmetrical luminescent donor-acceptor molecule of the general formula (I). The general reaction scheme can be represented as follows:

In particular, the Knoevenagel condensation reaction between an aldehyde and a methylene substrate is carried out in various organic solvents or their mixtures, for example, in toluene, chlorobenzene, tetrahydrofuran, dichloroethane, chloroform, pyridine in the presence of a basic catalyst in the reaction medium. Various bases can be used as a catalyst, for example, organic (triethylamine, pyridine, piperidine, sodium ethoxide, etc.) or inorganic (ammonium acetate, metal hydroxides, for example, NaOH, KOH, KOH, oxides, Al₂O₃ and etc., salts) bases, as well as their mixtures with Lewis acids (AlCl₃, TiCl_four). It is preferable to use pyridine, since in this case, it functions as both a solvent and a catalyst. The temperature range of the reaction in this case varies from +20 to +150 ºС, it is preferable to carry out the reaction at a temperature from +80 to +150 ºС, since carrying out the reaction at elevated temperatures increases the reaction rate and increases the yield of the target product. To do this, the heating of the reaction mixture can be carried out both in the traditional way and using microwave radiation. It is preferable to heat the reaction by microwave radiation, since in this case the heating occurs more evenly, without overheating the reaction mass, which leads to a decrease in by-products and a decrease in the reaction time.

After completion of the reaction, the condensation product is isolated according to known methods. For example, water and an organic solvent are added. The organic phase is separated, washed with water until neutral and dried, after which the solvent is evaporated. As an organic solvent, any solvent immiscible or limitedly miscible with water can be used, for example, selected from a number of ethers: diethyl ether, methyl tert-butyl ether, or selected from a number of aromatic compounds: benzene, toluene, xylene, or selected from a number of organochlorine compounds: dichloromethane, chloroform, carbon tetrachloride, chlorobenzene. Mixtures of organic solvents can also be used for isolation. The product can be isolated without the use of organic solvents, for example, by distillation of solvents from the reaction mixture, or by any other known method. It is preferable to isolate the product by distillation of the solvent followed by purification.

Purification of the target product is carried out by any known method, for example, preparative column chromatography in adsorption or exclusion mode, recrystallization, fractional precipitation, fractional dissolution, or any combination thereof.

The purity and structure of the resulting asymmetric donor-acceptor molecules are confirmed by a combination of physical and chemical analysis data obtained using methods such as chromatographic, spectroscopic, mass spectrometric. The most preferred confirmation of the purity and structure of the donor-acceptor molecules are ¹ H NMR spectra (see Fig. 3-4).

The starting aldehydes selected from a number of compounds of general formula (III) for the synthesis of unsymmetrical luminescent donor-acceptor molecules are obtained in two stages using a set of organic and organometallic synthesis reactions. A specific example of obtaining the starting aldehyde of general formula (III), where R1=H, is illustrated below (see Example 1).

INFORMATION CONFIRMING THE IMPLEMENTATION OF THE INVENTION

Figure 1 as an illustration shows the absorption and luminescence spectra in polystyrene polymer matrices of asymmetric donor-acceptor molecules according to Examples 2-5, 7.

Figure 2, as an illustration of high thermal stability, shows TGA curves in an inert atmosphere of asymmetric donor-acceptor molecules according to Examples 2-5, 7.

Figure 3 shows the ¹ H NMR spectrum of the compound of Example 2.

Figure 4 shows the ¹ H NMR spectrum of the compound of Example 7.

The invention can be illustrated by the following examples of the synthesis of asymmetric luminescent donor-acceptor molecules (see Example 1 and Table 1 with Examples 3-9). We used commercially available reagents and solvents without additional purification: 4-bromotriphenylamine, thiophene, magnesium (Mg), bis(diphenylphosphino)ferrocene]dichloropalladium (2) (Pd(dppf)Cl ₂ ), 1.6 M solution of n-butyllithium (n -BuLi) in hexane, N,N-dimethylformamide, N-ethyldicyanorhodanine, etc. Additional reagents and substances were obtained using procedures described in the literature. All reactions, unless otherwise noted, were carried out under an argon atmosphere.

Obtaining aldehydes of general formula (III), where R1=H for the synthesis of asymmetric luminescent donor-acceptor molecules.

Example 1. The synthesis of aldehyde (3) of general formula (III), where R1 is equal to H, was carried out according to the scheme below:

Preparation of compound 2. 4-(diphenylamino)phenylthiophene (2) was obtained by cross-coupling reaction under Kumada conditions: to a solution of 5.52 g (17.0 mmol) of triphenylamine monobromide (1) and 83 mg (0.1 mmol) of Pd(dppf)Cl ₂ into 35 ml of dry THF, 37 ml of a solution of thiophenemagnesium bromide (1eq) prepared in situ in THF was slowly added dropwise with stirring, while cooling in an inert atmosphere. Thereafter, the temperature of the reaction mixture was raised to room temperature over 1 hour, followed by stirring for 8 hours. After completion of the reaction, the reaction mixture was poured into 150 ml of distilled water and extracted with diethyl ether. The organic phase was washed with distilled water and dried over anhydrous Na ₂ SO ₄ . The solvent was distilled off in vacuo and the pure product (4.62 g, 83%) was obtained after purification on a silica gel column chromatography (eluent hexane:toluene 12:1). ¹ H NMR (250 MHz, CDCl ₃ , δ, ppm): 7.00-7.17 (overlapping signals, 9H), 7.21-7.32 (overlapping signals, 6H), 7.49 (d, 2H, J = 8.55 Hz).

Preparation of compound 3. 5-[4-(diphenylamino)phenyl]thiophene-2-carbaldehyde 3 was obtained as follows: a 1.6 M solution of n-butyllithium in hexane (10.4 ml, 16.7 mmol) was slowly added to a solution of compound 2 (5.43 g , 16.7 mmol) in 160 ml of dry THF at -78 ºС in an inert atmosphere. After that, stirring at a temperature of -78 ºС was continued for 1 hour. Then, one portion of 1.22 g (16.7 mmol) of anhydrous N,N-dimethylformamide was added to the reaction mass at a temperature of -78 ºС. After that, the temperature of the reaction mixture was raised to room temperature for 1 hour. After completion of the reaction, the reaction mixture was poured into 250 ml of distilled water and extracted with diethyl ether. The organic phase was washed with distilled water and dried over anhydrous Na ₂ SO ₄ . The solvent was distilled off in vacuo and the pure product (5.10 g, 87%) was obtained after purification on a silica gel column chromatography (eluent dichloromethane:hexane 10:1). ¹ H NMR (250 MHz, CDCl ₃ , δ, ppm): 7.03-7.20 (overlapping signals, 8H), 7.26-7.36 (overlapping signals, 5H), 7.53 (d, 2H, J = 8.55 Hz), 7.72 (d, 2H, J = 3.97 Hz), 9.87 (s, 1H).

Obtaining asymmetric luminescent donor-acceptor molecules.

Example 2 General procedure for the preparation of unsymmetrical luminescent donor-acceptor molecules of general formula (I) by means of Knoevenagel condensation reactions between an aldehyde selected from a number of compounds of general formula (III) and
N-ethyldicyanorhodanine, selected from a number of compounds of general formula (IV), is given below by the example of the aldehyde obtained above (Compound 3, Example 1), where R 1 = H, R 2 = linear C ₂ alkyl group, of general formula (IV-b):

A solution of aldehyde (3) from Example 1 (0.80 g, 2.3 mmol) and N-ethyldicyanorhodanine (0.65 g, 3.4 mmol) in 24 ml of dry pyridine was subjected to microwave irradiation at the boil for 8 hours. After completion of the reaction, the reaction mass was evaporated from pyridine in a vacuum, and the pure product (0.86 g, 72%) was obtained after purification on a chromatographic column with silica gel (eluent chloroform). ¹ H NMR (250 MHz, CDCl ₃ , δ, ppm): 1.42 (t, 3H, J = 7.32 Hz), 4.32 (dd, 2H, J ₁ = 7.02 Hz, J ₂ = 14.34 Hz), 7.03 -7.20 (overlapping signals, 8H), 7.26-7.36 (overlapping signals, 5H), 7.46 (d, 1H, J = 3.97 Hz), 7.54 (d, 1H, J = 8.85 Hz), 8.06 (s, 1H).

Other examples (Examples 3-9) of asymmetric luminescent donor-acceptor molecules of general formula (I), obtained in a similar way, as well as some of the main physico-chemical properties of the obtained molecules, are presented in Table 1.

Table number 1.

Example No. Structural formula of asymmetric luminescent donor-acceptor molecules Some Properties of Unsymmetrical Donor-Acceptor Molecules Maximum absorption spectrum in the polystyrene matrix, nm Maximum photoluminescence spectrum in a polystyrene matrix, nm PLQY, % Thermal stability, ^o C 2

525 620 50 355 3

505 600 23 361 four

615 710 26 300 five

479 565 40 315 6

485 581 46 301 7

486 605 33 340 8

471 591 37 334 nine

479 599 24 345

Note: PLQY is the photoluminescence quantum yield.

Claims (28)

1. Asymmetric luminescent donor-acceptor molecules of general formula (I):

(I) where R1 denotes H or a substituent selected from the series: linear C ₁ -C ₁₂ alkyl groups; linear C ₁ -C ₁₂ alkyl groups separated by at least one oxygen atom; EWG stands for an electron withdrawing group selected from: N-alkyl- or N-phenyl derivative of 2-thioxo-1,3-thiazolidin-4-one of general formula (II-a):

(II-a), where R2 denotes linear C ₁ -C ₆ alkyl or phenyl groups; N-alkyl or N-phenyl derivative of 2-(dicyanomethylene)-1,3-thiazolidin-4-one of the general formula (II-b):

(II-b), where R2 denotes linear C ₁ -C ₆ alkyl or phenyl groups; alkyl derivative of cyanoacetate of general formula (II-c):

(II-c), where R2 denotes alkyl linear C ₁ -C ₆ or branched C ₃ -C ₁₂ groups; 4-nitrophenyl derivative of acetonitrile of general formula (II-d):

(II-d), where R3 is a nitro substituent. 2. Asymmetric luminescent donor-acceptor molecules according to claim 1, characterized in that R1 denotes H or a substituent selected from the series: linear C ₁ -C ₁₂ alkyl groups; linear C ₁ -C ₁₂ alkyl groups separated by at least one oxygen atom. 3. Asymmetric luminescent donor-acceptor molecules according to claim 1, characterized in that EWG denotes an electron-withdrawing group selected from a number of compounds of formula (IIa-d). 4. Asymmetric luminescent donor-acceptor molecules according to claim 1, characterized in that the maxima of their absorption spectra in the polymer polystyrene matrix are in the range from 470 nm to 565 nm. 5. Asymmetric luminescent donor-acceptor molecules according to claim 1, characterized in that the maxima of their luminescence spectra in the polymer polystyrene matrix are in the range from 560 nm to 705 nm. 6. Asymmetric luminescent donor-acceptor molecules according to claim 1, characterized in that their quantum yield of photoluminescence in a polymeric polystyrene matrix is at least 20%. 7. Asymmetric luminescent donor-acceptor molecules according to claim 1, characterized in that they have high thermal stability of at least 300 ^° C. 8. A method for obtaining asymmetric luminescent donor-acceptor molecules according to claim 1, which consists in carrying out the Knoevenagel condensation reaction between an aldehyde selected from a number of compounds of general formula (III):

(III) where R1 denotes H or a substituent selected from the series: linear C ₁ -C ₁₂ alkyl groups; linear C ₁ -C ₁₂ alkyl groups separated by at least one oxygen atom, and various EWG precursors having active methylene groups selected from the series (IVa-d):

(IV-a), where R2 denotes linear C ₁ -C ₆ alkyl or phenyl groups;

(IV-b), where R2 denotes linear C ₁ -C ₆ alkyl or phenyl groups;

(IV-c), where R2 denotes alkyl linear C ₁ -C ₆ or branched C ₃ -C ₁₂ groups;

(IV-d) where R3 is a nitro substituent. 9. The method according to claim 8, characterized in that the Knoevenagel condensation reaction between aldehyde and various EWG precursors having active methylene groups is carried out in a pyridine medium or a mixture thereof with at least one solvent selected from the series toluene, tetrahydrofuran, chloroform, dichloroethane, chlorobenzene, while pyridine is also a catalyst. 10. The method according to claim 8, characterized in that the Knoevenagel condensation reaction between the aldehyde and various EWG precursors having active methylene groups is carried out at a temperature of from +20 ^to +150 ° C, preferably at a temperature of from +80 ^to +150 ° C . 11. The method according to claim 8, characterized in that the Knoevenagel condensation reaction between the aldehyde and various EWG precursors having active methylene groups is carried out by heating with microwave radiation.

Images