RU2671964C1 - PYRAZOLO [1,5-a]GADOLINIUM PYRIMIDINCARBOXYLATES AND FOLLOWING ORGANIC LEDS - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to new compounds, namely to exhibiting luminescent properties of gadolinium complexes of the general formula Gd(Carb)₃(H₂O)_x, where carb^-=

or

, and where values for groups R₁, R₂, R₃ and R₄ defined in p. 1 formula.

EFFECT: invention relates to organic light-emitting diodes based on gadolinium complexes.

4 cl, 18 ex, 1 tbl

Description

The invention relates to new compounds, namely, complexes of gadolinium with anions of pyrazolo [1,5-a] pyrimidinecarboxylic acids exhibiting luminescent properties.

It is known that coordination compounds (CS) of lanthanides with organic ligands often exhibit luminescent properties, including during photo- or electroexcitation.

One of the most relevant areas of application of luminescent materials is their use as luminescent materials in optical devices, including as an emission layer in organic light emitting diodes (OLED or OLED - Organic Light Emitting Diode).

Organic light emitting diodes (OLED or OLED) are devices that emit light under the influence of an electric current. An organic light emitting diode consists of at least an emission layer enclosed between the cathode and the anode. The emission layer is a thin film of a luminescent compound. When a current flows through an organic light emitting diode, charge carriers of different signs — electrons and holes — recombine in the emission layer, which leads to the appearance of excited states - excitons, 75% of which are triplet and 25% singlet. Relaxation of excited states leads to luminescence of the material of the emission layer. To facilitate the injection of electrons and holes into the emission layer in OLED, as a rule, additional layers with electron and / or hole mobility (transport layers), as well as electron and / or hole-blocking layers, are introduced. Like the emission layer, all layers of the OLED heterostructure are thin films with a thickness of 10–500 nm.

As mentioned above, an exciton is formed upon the recombination of charge carriers in the emission layer or on its surface. Therefore, for efficient electroluminescence, the material of the emission layer must possess electron and / or hole transport properties in addition to a high quantum yield of luminescence. However, many luminescent materials, including many compounds of rare-earth elements, have neither electron-hole transport properties.

In this case, to improve the transport properties using the method of introducing a phosphor into the host layer, which is used as a transport material.

The first such composite emission layer was proposed in 1989 by [J. Appl. Phys. 65 (1989) 3610], where coumarin 540 was used as the phosphor, and AlQ _{3 was} used as the host.

In the future, the method of obtaining the emission layer by introducing a phosphor into the host was widespread.

Since 75% of excitons are triplet in nature, it is advisable to use compounds in the emission layer materials whose triplet level is involved in the luminescence. These include many coordination compounds (CS) of gadolinium, in which luminescence from the triplet state (phosphorescence) is possible, but usually it occurs only at low temperatures (-200 C) [Dalt. Trans. 43 (2014) 3121-3136; Mend. Comm. 24 (2014) 91-93; Coord. Chem. 42 (2016) 1-17], although gadolinium CSs that phosphoresce at room temperature are also found [Chem. - A Eur. J. 21 (2016) 17921-17932; J Mater Chem C 4 (2016) 9848-985; patent RU 2605746, patent RU 2015140097]. The criterion for the occurrence of precisely phosphorescence, and not fluorescence, is the lifetime of the excited state: in the case of fluorescence, it usually does not exceed tens of nanoseconds (ns), while in the case of phosphorescence it is usually no less than microseconds [P.S. Kalsi, Spectroscopy of Organic Compounds, New Age International, 2007].

From the point of view of use, aromatic carboxylates of lanthanides, including gadolinium, which are highly stable (chemical, optical, thermal), are of particular interest.

Obtaining stable CS gadolinium with phosphorescence at room temperature is an urgent task.

The technical problem to which the invention is directed is to expand the arsenal of luminescent gadolinium complexes.

The problem is solved in that pyrazolo [1,5-a] pyrimidinecarboxylates of gadolinium of the general formula Gd (Carb) ₃ (H ₂ O) _x ,

Where

или

or

x is 0-3;

R ₁ selected from the group consisting of hydrogen, halogen and alkyl

R _{3 is} selected from the group consisting of hydrogen and alkyl, where alkyl is optionally substituted with one or more groups selected from the group consisting of halogen, hydroxyl, alkyl, alkenyl, alkynyl alkoxy, cycloalkyl, aryl, heteroaryl.

R ₂ and R ₄ are each independently selected from the group consisting of hydrogen, halogen, alkyl, alkoxy, cycloalkyl, aryl, heteroaryl, —C (O) OR ₅ , —OC (O) R ₅ , —C (O) R ₅ , —NHC (O) R ₅ and —NR ₆ R ₇ , where alkyl, alkoxy, cycloalkyl, aryl or heteroaryl, including oligoaromatic, are each optionally substituted with one or more groups selected from the group consisting of halogen , hydroxyl, alkyl, alkenyl, alkynyl alkoxy, cycloalkyl, aryl, heteroaryl, -C (O) OR ₅ , -OC (O) R ₅ , -C (O) R ₅ , -NHC (O) R ₅ and -NR ₆ R ₇

R ₅ , R ₆ and R _{7 are} each independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl and heteroaryl.

Another technical problem solved by this invention is the expansion of the arsenal of organic light-emitting diodes.

This object is achieved in that organic light-emitting diodes are obtained in which a thin film of the Gd (Carb) ₃ (H ₂ O) _x compound or a thin film of a composite material containing the specified compound is used as the emission layer.

The resulting acidide is a multilayer heterostructure consisting of a carrier base made in the form of a substrate with a transparent layer of anode placed on it, on which the emission layer and cathode are located. To improve performance, in hole between the anode and the emission layer, hole-injecting and / or hole-transporting and / or electron-blocking layers can be additionally placed between the anode and the emission layer, and electron-transporting and / or hole-transporting layers on top of the emission layer in front of the cathode.

Unless otherwise indicated, the following definitions used in the description and claims have the meanings given below.

Transport material - material with transport properties in relation to charge carriers - electrons and / or holes, i.e., having high electron or hole mobility;

Doping - the introduction and uniform distribution of one material in another.

A host, or matrix, is a material into which a luminescent material is doped to improve luminescent properties.

Composite material - a material containing a phosphor doped into a host.

An exciton is an excited state of a phosphor molecule.

“Substituted” - means that one or more hydrogen atoms in any accessible place in the indicated group are independently substituted by the corresponding number of substituent groups (substituents). It is understood that the substituents exist only in their possible chemical position. Specialist in the art without special experimental and theoretical studies can determine whether substitution is or is not possible.For example, the combination of amino or hydroxyl groups having free hydrogen and carbon atoms with non saturated bonds (e.g., olefinic) may be unstable.

“Perhaps substituted” means that substitution may, but is not necessary, take place. Those. the description includes the case when the hydrogen atom (s) in the indicated group is substituted by the substituent (s) and the case when there is no substitution.

“Alkyl” means a saturated aliphatic hydrocarbon group including straight and / or branched C ₁ -C ₁₀ groups. Preferably, the alkyl group is alkyl having 1 to 5 carbon atoms. Typical examples include, but are not limited to, methyl , ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, 2 -methylbutyl, 3-methylbutyl, etc. The alkyl group may be substituted or unsubstituted. Tel / and represents one or more groups independently selected from the group consisting of halogen, alkyl, alkoxy, hetero alkyl, aryl, heteroaryl,

"Cycloalkyl" means a saturated or partially unsaturated monocyclic or polycyclic hydrocarbon group containing from 3 to 10 carbon atoms, preferably from 3 to 6 carbon atoms. Typical examples of monocyclic cycloalkyl include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cyclohexadienyl, etc. The cycloalkyl group may be substituted or unsubstituted. Preferably, the substituent / and represents one or more groups independently selected from the group consisting of halogen, alkyl, alkoxy, cycloalkyl, aryl, heteroaryl.

“Aryl” means a 6-14 membered carbon monocyclic ring or a polycyclic fused ring (“fused” ring means that each ring (cycle) in the specified system has a common pair of adjacent carbon atoms with another ring (cycle) in the specified cyclic system) , and has a fully coupled pi-electronic system. Preferably, aryl is 6-10 membered, such as phenyl and naphthyl, most preferably phenyl. Said aryl may be fused to heteroaryl, or cycloalkyl, wherein the ring bound to the parent structure is aryl. Typical examples include, but are not limited to, the following groups:

и

and

The aryl group may be substituted or unsubstituted. Preferably, the substituent / and represents one or more groups independently selected from the group consisting of halogen, alkyl, alkoxy, aryl, heteroaryl.

“Heteroaryl” - means a 5-14 membered carbon monocyclic ring or a polycyclic fused ring (“fused” ring means that each ring (cycle) in the specified system has a common pair of adjacent carbon atoms with another ring (cycle) in the specified cyclic system) , and has a fully conjugated pi-electronic system containing from 1 to 4 heteroatoms selected from the group consisting of N, O and S as ring atoms. Preferably, the heteroaryl is 5-10 membered and, more preferably, 5-6- membership. Examples include furyl, thienyl, pyridyl, pyrrolyl, N-alkyl pyrrolyl, pyrimidinyl, pyrazinyl, imidazolyl, tetrazolyl and the like. Said heteroaryl may be fused to an aryl or cycloalkyl ring, wherein the ring associated with the parent structure is a heteroaryl ring. Typical examples include, but are not limited to, the following groups:

и

and

The heteroaryl group may be substituted or unsubstituted. Preferably, the substituent / and represents one or more groups independently selected from the group consisting of alkyl, alkoxy, halogen, aryl, heteroaryl.

“Alkoxy” - means both the group —O— (alkyl) and the group —O— (unsubstituted cycloalkyl), where alkyl and cycloalkyl are as defined above. Representative examples include, but are not limited to, methoxy, ethoxy, propoxy, butoxy, cyclopropyloxy, cyclobutyloxy, cyclopentyloxy, cyclohexyloxy, and the like. The alkoxy group may be substituted or unsubstituted. Preferably, the substituent / and represents one or more groups independently selected from the group consisting of alkyl, alkoxy, halogen, cycloalkyl, aryl, heteroaryl.

"Halogen" means fluorine, chlorine, bromine or iodine.

"Hydroxyl" - refers to the group-OH.

“Amino” means a group —NH ₂ .

All of the claimed compounds exhibit interesting luminescent properties, namely, they have phosphorescence at room temperature, electroluminescence, as well as transport properties.

содержащего два сопряженных кольца и атом азота, участвующий в координации иона гадолиния.We have shown that the ability to phosphorescence and the presence of transport properties of the claimed compounds is determined by the presence in their composition of a conjugated heteroaromatic fragment

containing two conjugated rings and a nitrogen atom involved in the coordination of the gadolinium ion.

It can be assumed that the presence of a coordinating nitrogen atom leads to an increase in the degree of covalency of the metal-ligand bond, which in turn leads to an increase in intrasystem transport due to the presence of a paramagnetic ion (gadolinium), and, as a result, to the manifestation of phosphorescence at room temperature.

In addition, due to the presence of heteroatoms, this fragment is electron depleted, which allows it to be an electron acceptor, and a high degree of conjugation allows electron transfer along a chain of molecules with high efficiency. Thus, both conditions for the occurrence of electronic transport are fulfilled, which leads to the presence of transport properties of the claimed compounds.

The introduction of substituents in the indicated fragment can lead to a change in the luminescence wavelength, electroluminescence intensity, solubility and stability of the CS, but does not affect the presence of phosphorescence ability and transport properties in the claimed complexes.

The ability to electroluminescence and the presence of transport properties allows the use of thin films of the obtained complexes as an emission layer in OLED. To improve the transport properties, and, consequently, the intensity of electroluminescence, a thin film of a composite material obtained by doping the complex into a host, which is used as a transport material, can be used as the emission layer.

Currently, a large number of organic and inorganic compounds are known that have high electronic and / or hole conductivity, for example [http://www.lumtec.com.tw] and can be used as transport material.

The most widely used transport materials to obtain a composite emission layer are currently poly-N-vinylcarbazole (PVK), N, N'-bis (3-methylphenyl) -N, N'-bis (phenyl) -benzidine (TPD) , 4,4'-N, N'-dicarbosolbiphenyl (CBP), 2,2 ', 2' '- (1,3,5-benzintriyl) -tris (1-phenyl-1-H-benzimidazole) (TPBi) [Dyes and Pigments 124 (2016) 35-44].

OLED is a multilayer heterostructure consisting of at least a carrier base made in the form of a substrate with a transparent layer of anode placed on it, on which an emission layer is located, on top of which the cathode is located.

For the manufacture of the anode and cathode, any suitable materials may be used.

The anode can be made, for example, of indium tin oxide (ITO) or fluorine tin oxide (FTO). The cathode can be made, for example, of calcium, aluminum, ytterbium, silver or sequentially deposited calcium and aluminum.

Devices consisting only of the anode, the emission layer, and the cathode are suitable for demonstrating the electroluminescence of the emission layer, however, its intensity is extremely low and the applied voltage is extremely high; therefore, hole-injecting and / or hole transport and / or electron blocking layers, and on top of the emission layer in front of the cathode, electron injecting and / or electron transport and / or hole blocking layers. As such can be used, for example:

- hole injecting: poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonate) (PEDOT: PSS), MoS ₂ , MoSe ₂ and others

- hole transport and / or electron blocking: N, N'-bis (naphthalen-1-yl) -N, N'-bis (phenyl) -2,2'-dimethylbenzidine (α-NPD), N, N'-bis ( 3-methylphenyl) -N, N'-bis (phenyl) -benzidine (TPD), N, N'-bis (naphthalen-1-yl) -N, N'-bis (phenyl) -benzidine (NPB), poly [N, N'-bis (4-butylphenyl) -N, N'-bis (phenyl) benzidine] (poly-TPD) and others

- electron-injecting: LiF, CsF, CaF ₂ , MgF ₂ and others

- electron transport and / or hole blocking: lithium 8-hydroxyquinolinate (Liq), aluminum 8-hydroxyquinolinate (Alq), 1,3,5-tris (1-phenyl-1H-benzimidazol-2-yl) benzene (TPBi), 2- (4-Biphenyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (PBD), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (HRV), 4, 7-diphenyl-1,10-phenanthroline (BPhen), 3- (4-biphenyl) -4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ) and others.

The inventive complex compounds of gadolinium can be obtained by any suitable method, for example, by reacting lanthanide hydroxide and the corresponding acid in an organic medium

Gd (OH) ₃ + 3H Carb = Gd (Carb) (H ₂ O) _x + (3-x) H ₂ O

The synthesis is carried out by reacting an excess of freshly precipitated lanthanide hydroxide with a suspension of the corresponding acid in an organic medium. In this case, dissolution occurs due to complexation.

The starting organic acids, in turn, can be obtained, for example, by reacting substituted betadiketonates with derivatives of 5-aminopyrazolecarboxylic acid [J. Comb. Chem. 2005, 7, 236-245].

or

Moreover, during each of the reactions, isomers A and B are formed, the separation of which is carried out by high performance liquid column chromatography (HPLC). After separation, each isomer is used separately.

The following examples of specific performance illustrate the claimed invention, but do not limit it.

Examples

Organic acids are prepared by reacting the corresponding substituted betadiketone and substituted 5-aminopyrazolecarboxylic acid. For this, a suspension of amino acid (1 mol) and betadiketone (1 mol) is placed in 600 ml of a mixture of acetic acid: 2N aqueous HCl solution (1: 1 by volume) and heated under reflux for 7 hours. After cooling to room temperature, the precipitate formed is filtered off and recrystallized from acetonitrile.

The resulting product is sent to the separation of isomers by HPLC. Each of the obtained individual products is analyzed. The composition of the products is confirmed by elemental analysis, and the structure, in particular, the position of each of the substituents, is established using ¹ H NMR spectroscopy, including two-dimensional (COZY, NOESY).

The complexes are prepared as follows.

To a solution of 1.1 mmol of gadolinium nitrate in 10 ml of water, a stoichiometric amount of aqueous ammonia is added dropwise. The precipitated gadolinium hydroxide is centrifuged, washed three times with water and transferred to a glass with a solution of 3 mmol of the corresponding acid in 100 ml of a mixture of toluene: ethanol (1: 1 by volume). The reaction mixture is left on a magnetic stirrer when heated under reflux for 3 hours, while dissolution occurs due to complexation. An undissolved excess of the starting gadolinium hydroxide is filtered off on a paper filter, the clear solution is evaporated to dryness on a rotary evaporator (30 min, water-jet pump, 60 ° C). The product is collected and dried in air (day).

Anhydrous Gd (Carb) _{3 is} obtained by keeping in vacuum (0.01 mm Hg) the corresponding hydrates of Gd (Carb) ₃ (H ₂ O) _x at 200 ° C for one hour.

The presence of a paramagnetic gadolinium ion in all CSs did not allow us to use the usually very informative NMR spectroscopy method to determine the composition due to the extremely strong signal broadening in the spectrum; therefore, the composition of the target product is determined by the combination of elemental analysis data (C, H, Vario Micro N-analyzer Cube (Elementar, Germany) and thermal analysis (STA 409 thermal analyzer, NETZSCH, Germany, in the temperature range 20-1000 ° C in argon flow, heating rate 10 ° / min, initial mass ~ 5 mg). The presence or absence is coordinated water molecules were determined by the presence or absence of a characteristic wide band in the IR spectra in the region of 3600 cm ^–1 (Perkin-Elmer Spectrum One IR spectrometer).

The presence and region of luminescence is determined by recording the luminescence spectra upon excitation with a wavelength of 300 nm on a Fluorolog 3 luminescent spectrometer. The lifetime of the excited state is determined based on the luminescence decay curve. The lifetime of all the complexes obtained lies in the range of 8–11 μs, which corresponds to phosphorescence.

To assess the efficiency of electroluminescence, the obtained compounds or composite materials based on them were used as emission layers in acid, which were prepared as follows:

The glass substrate coated with indium tin oxide (ITO, anode) is cleaned by immersion in an ultrasonic bath filled with a slightly alkaline solution (NaOH, 5%) for 30 minutes. Then the substrate is removed from the bath, washed with a copious amount of distilled water and dried.

A dry substrate is placed on the spincoater and a hole-injecting layer of PEDOT is applied on it: PSS (poly (3,4-ethylenedioxythiophene) -poly (styrene sulfonate)) (5 g / l in H ₂ O), for which 70 μl of the solution is applied from the dispenser to the surface substrate and untwist (2000 rpm, 2 min). The substrate is removed, heat treated at 100 ° C for 30 minutes and an emission layer is applied.

In Examples 1a, 2a, 3a, 4a, 7, 9, 12, 13, 16-18, a solution for applying an emission layer was prepared by dissolving 5 mg of Gd (Carb) ₃ in 1 ml of toluene.

In Example 2b, a solution for applying an emission layer was prepared by dissolving a mixture of 0.75 mg Gd (Carb) ₃ and 4.25 mg PVK in 1 ml of toluene.

In Example 4b, a solution for applying an emission layer was prepared by dissolving a mixture of 0.75 mg Gd (Carb) ₃ and 4.25 mg TPD in 1 ml of toluene.

In examples 1b, 2c, 3b, 5-6, 8, 10, 11, 14, 15, 19-32, a solution for applying the emission layer was obtained by dissolving a mixture of 0.25 mg Gd (Carb) ₃ and 4.75 mg CBP in 1 ml of toluene.

The application of the emission layer in all examples is carried out by applying 70 μl of the appropriate solution to the substrate, followed by unwinding (1500 rpm, 2 min).

A TAZ (3- (biphenyl-4-yl) -5- (4-tert-butyl-phenyl) -4-phenyl-4H-1 film was applied on top of the emission layer by physical evaporation in a vacuum in all examples except 2b. 2,4-triazole, 10 nm, electron transport material) and an aluminum film (100 nm, cathode), and in example 2b, a BPhen film (bathophenanthroline, 10 nm, electron transport material), a LiF film (1 nm, electron injection material) and a film aluminum (100 nm, cathode).

The intensity of electroluminescence (EL) is measured at the wavelength of the maximum luminescence indicated in the table at a voltage of 9V.

The results are shown in Table. one.

Studies have shown that the obtained aromatic gadolinium carboxylates luminesce, and the luminescence of all complexes is precisely phosphorescence, which follows from the high lifetimes of the excited state.

The obtained complexes also have electroluminescence, both as when a thin film of the Gd (Carb) ₃ (H ₂ O) _x compound by itself is used as the emission layer, and when the complex is used as part of a composite emission layer.

Examples 1a, 2a, 3a, 4a, 7, 9, 12, 13, 16-18 show that the resulting complexes have charge carrier mobility. Indeed, the presence of intense electroluminescence of OLEDs containing, as the emission layer, a film of a complex not doped to the host, is possible only if the complex has both luminescent and transport properties.

Among the obtained compounds, the most interesting are the complex according to example 18, having luminescence in the shortest wavelength range of the spectrum. This is especially important, since the search for blue emitters for acid is one of the most urgent tasks.

Claims (15)

1. Pyrazolo [1,5-a] pyrimidine carboxylates of gadolinium of the general formula Gd (Carb) ₃ (H ₂ O) _x , Where

x is 0-3; R ₁ selected from the group consisting of hydrogen, halogen and alkyl; R _{3 is} selected from the group consisting of hydrogen and alkyl, where alkyl is optionally substituted with one or more groups selected from the group consisting of halogen, hydroxyl, alkyl, alkenyl, alkynyl alkoxy, cycloalkyl, aryl, heteroaryl; R ₂ and R ₄ are each independently selected from the group consisting of hydrogen, halogen, alkyl, alkoxy, cycloalkyl, aryl, heteroaryl, —C (O) OR ₅ , —OC (O) R ₅ , —C (O) R ₅ , —NHC (O) R ₅ and —NR ₆ R ₇ , where alkyl, alkoxy, cycloalkyl, aryl or heteroaryl, including oligoaromatic, are each optionally substituted with one or more groups selected from the group consisting of halogen , hydroxyl, alkyl, alkenyl, alkynyl alkoxy, cycloalkyl, aryl, heteroaryl, -C (O) OR ₅ , -OC (O) R ₅ , -C (O) R ₅ , -NHC (O) R ₅ and -NR ₆ R ₇ ; R ₅ , R ₆ and R _{7 are} each independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl and heteroaryl; or formula Gd (Carb) ₃ , where Carb ^- represents

23 or

2. Organic light-emitting diode containing at least a carrier base made in the form of a substrate with a transparent layer of anode placed on it, an emission layer and a cathode, characterized in that a thin film of the compound according to claim 1 or a thin film is used as the emission layer a film of a composite material containing a compound according to claim 1. 3. The organic light emitting diode according to claim 2, characterized in that between the anode and the emission layer there are additionally placed hole-injecting and / or hole transport and / or electron-blocking layers. 4. Organic light emitting diode according to claims. 2 and 3, characterized in that on top of the emission layer in front of the cathode, electron-injecting and / or electron-transporting and / or hole-blocking layers are additionally placed.