Iridium complexes and organic light emitting devices

Abstract

The application discloses an iridium complex and an organic light-emitting device, and belongs to the technical field of display. a represents a first substituent selected from at least one of deuterium, halogen, -CF3, -CN, and substituted or unsubstituted C1-C10 alkyl; R1 and R2 are the same or different, and each is independently selected from deuterium, fluorine, substituted or unsubstituted C1-C20 alkyl, or substituted or unsubstituted C3-C20 cycloalkyl; ring A comprises a group as shown in the following chemical structural formula: q≥2, R b represents a second substituent selected from at least one of deuterium, halogen, -CF3, -CN, and substituted or unsubstituted C1-C10 alkyl, and at least two second substituents in ring A are connected to each other to form a substituted or unsubstituted C5-C20 ring.

Description

Technical Field

[0001] This invention relates to the field of display technology, and particularly to iridium complexes and organic light-emitting devices. Background Technology

[0002] Organic light-emitting diodes (OLEDs) are semiconductor light-emitting devices based on organic light-emitting materials. OLED devices include a light-emitting layer based on the light-emitting material, and the type of light emitted can be adjusted by changing the light-emitting material. Phosphorescent materials can effectively utilize triplet excitons, and theoretically, their internal quantum efficiency can be increased from 25% to 100% compared to fluorescent materials.

[0003] Iridium complexes are a common type of organic electroluminescent phosphorescent material, which has advantages such as good phosphorescence emissivity, high phosphorescence emissivity, wide emission spectrum and strong stability. It is a widely used organic electroluminescent phosphorescent material.

[0004] However, the narrow bandgap of red iridium complexes makes energy level matching between the emitting layer and the carrier transport layer difficult and prone to concentration quenching. Therefore, it is necessary to improve red iridium complexes. Summary of the Invention

[0005] Therefore, embodiments of the present invention provide an iridium complex and an organic light-emitting device, which can solve the above-mentioned technical problems.

[0006] Specifically, the following technical solutions are included:

[0007] On the one hand, an iridium complex is provided, the chemical structural formula of which is shown below:

[0008]

[0009] Where p≥1, R a Represents a first substituent, and when there are multiple first substituents, the multiple first substituents may be the same or different, and the first substituent is selected from at least one of deuterium, halogen, -CF3, -CN, substituted or unsubstituted C1-C10 alkyl groups;

[0010] R1 and R2 may be the same or different, and each is independently selected from deuterium, fluorine, substituted or unsubstituted C1-C20 alkyl or substituted or unsubstituted C3-C20 cycloalkyl.

[0011] Ring A includes groups as shown in the following chemical structural formula:

[0012]

[0013] q≥2, Rb Representing a plurality of identical or different second substituents, the second substituents being selected from at least one of deuterium, halogen, -CF3, -CN, substituted or unsubstituted C1-C10 alkyl groups, and at least two of the second substituents in ring A are connected to each other to form a substituted or unsubstituted C5-C20 ring.

[0014] In some possible implementations, the iridium complex comprises a benzo[F]isoquinoline ring having eight substituted sites, with the following general structural formula:

[0015]

[0016] Among them, T 11 -T 18 One, two, or three of them are not hydrogen.

[0017] In some possible implementations, T 13 T 14 T 15 and T 16 If there exists a component that is not hydrogen, then T 13 T 14 T 15 and T 16 The non-hydrogen alkyl group is selected from deuterium, halogen, -CF3, CN, substituted or unsubstituted C1-C4 alkyl groups.

[0018] In some possible implementations, T 14 -T 16 If there are two elements in T that are not hydrogen, then... 14 -T 16 The two non-hydrogen atoms are each independently selected from deuterium, halogen, -CF3, CN, or substituted or unsubstituted C1-C4 alkyl groups.

[0019] In some possible implementations, T 13 -T 18 If there are three elements in T that are not hydrogen, then... 13 -T 18 The three non-hydrogen groups are each selected from deuterium, halogen, -CF3, CN, and substituted or unsubstituted C1-C4 alkyl groups.

[0020] In some possible implementations, T 11 -T 18 At least two of them are connected to form substituted or unsubstituted C5-C20 carbocyclic groups;

[0021] For substituted C5-C20 carbocyclic groups, the corresponding substituent is T. 1x The T1x Selected from deuterium, halogens, -CF3, CN, substituted or unsubstituted C1-C4 alkyl groups.

[0022] In some possible implementations, at least two of the second substituents are connected to each other in ring A to form a substituted or unsubstituted C5-C8 aliphatic ring, or to form a substituted or unsubstituted C4-C7 heterocyclic compound.

[0023] In some possible implementations, the heteroatoms included in the substituted or unsubstituted C4-C7 heterocyclic compound are N, O, or S.

[0024] In some possible implementations, R1 and R2 are each independently a group having the following chemical structural formula:

[0025]

[0026]

[0027] On the other hand, an organic light-emitting device is also provided, the organic light-emitting device including a light-emitting layer, the raw material for preparing the light-emitting layer including any of the iridium complexes described above.

[0028] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0029] The iridium complex provided in this embodiment of the invention, as can be seen from its chemical structure, adopts a main ligand with a benzo[F]isoquinoline ring as the main ligand and an auxiliary ligand with R1 and R2 groups as the main ligands. The combination of the main ligand and the auxiliary ligands makes the iridium complex, when used as a red light dopant, not only more effectively improve the luminous efficiency and luminous lifetime, but also have stronger thermal stability. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of an exemplary organic light-emitting device provided in an embodiment of the present invention.

[0032] The reference numerals in the attached figures represent:

[0033] 1-Anode, 2-Hole injection layer, 3-Hole transport layer, 4-Electron blocking layer

[0034] 5-Light-emitting layer, 6-Electron transport layer, 7-Electron injection layer, 8-Cathode. Detailed Implementation

[0035] To make the technical solutions and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0036] Organic light-emitting diodes (OLEDs) are semiconductor light-emitting devices based on organic light-emitting materials. An OLED device includes at least a hole transport layer, an emissive layer, and an electron transport layer. Holes generated by the anode travel through the hole transport layer to the emissive layer, and electrons generated by the cathode travel through the electron transport layer to the emissive layer. Holes and electrons then form excitons in the emissive layer, emitting light. The type of light emitted can be adjusted by changing the light-emitting material.

[0037] Typically, 25% of excitons are in singlet excited states, while the remaining 75% are in triplet excited states. The radiative transition pathways corresponding to these two types of excitons are singlet fluorescence and triplet phosphorescence, respectively. Phosphorescent materials can effectively utilize triplet excitons; theoretically, compared to fluorescent materials, the internal quantum efficiency of phosphorescent materials can be increased from 25% to 100%. Therefore, high-efficiency phosphorescent organic light-emitting diodes (OLEDs) are a focus of attention for applications in devices such as flat panel displays and portable displays.

[0038] Common phosphorescent materials include red, green, and blue phosphorescent materials, with iridium complexes being a widely used organic electroluminescent phosphorescent material. Iridium's high atomic number results in strong spin-orbit coupling in iridium complexes, which is beneficial for phosphorescence emission. The large splitting of the d-orbitals in iridium metal ions avoids metal-ligand charge-transfer (MLCT) interactions with ligands, further improving phosphorescence emission efficiency. The trivalent iridium ion can form very stable neutral molecules with ligands, facilitating the fabrication of light-emitting devices using vacuum evaporation or solution processing. The emitted light from iridium complexes can cover the entire visible spectrum and exhibits good stability, meeting the requirements of electroluminescent materials. Therefore, iridium complexes, with their advantages of good phosphorescence emission, high phosphorescence efficiency, broad emission spectrum, and strong stability, have become a research focus in organic electroluminescent phosphorescent materials.

[0039] However, the narrow bandgap of red iridium complexes makes energy level matching between the emitting layer and the carrier transport layer difficult and prone to concentration quenching. Therefore, it is necessary to improve red iridium complexes.

[0040] This invention provides an iridium complex, the chemical structural formula of which is shown below:

[0041]

[0042] Where p≥1, R a The first substituent represents a first substituent, and when there are multiple first substituents, the multiple first substituents may be the same or different, and the first substituent is selected from at least one of deuterium, halogen, -CF3, -CN, substituted or unsubstituted C1-C10 alkyl groups.

[0043] R1 and R2 may be the same or different, and each is independently selected from deuterium, fluorine, substituted or unsubstituted C1-C20 alkyl or substituted or unsubstituted C3-C20 cycloalkyl.

[0044] Ring A includes groups as shown in the following chemical structural formula:

[0045]

[0046] Where a represents the binding site of ring A with the benzo[F]isoquinoline ring, and b represents the binding site of ring A with iridium (Ir).

[0047] q≥2, R b Representing multiple identical or different second substituents, the second substituents are selected from at least one of deuterium, halogen, -CF3, -CN, substituted or unsubstituted C1-C10 alkyl groups, and at least two second substituents are connected to each other in ring A to form a substituted or unsubstituted C5-C20 ring.

[0048] The iridium complex provided in this embodiment of the invention, as can be seen from its chemical structure, adopts a main ligand with a benzo[F]isoquinoline ring as the main ligand and an auxiliary ligand with R1 and R2 groups as the main ligands. The combination of the main ligand and the auxiliary ligands makes the iridium complex, when used as a red light dopant, not only more effectively improve the luminous efficiency and luminous lifetime, but also have stronger thermal stability.

[0049] In some implementations, R a The first substituent can be selected from deuterium, halogen, -CF3, -CN, substituted or unsubstituted C1-C4 alkyl groups. Furthermore, the C1-C4 alkyl group can be substituted by deuterium, halogen, -CF3, -CN, etc.

[0050] The C1-C4 alkyl groups mentioned above include, but are not limited to: methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc. The halogens mentioned above include fluorine, chlorine, bromine, and iodine.

[0051] In some implementations, R a The first substituent is selected from F or -CF3.

[0052] In some implementations, the iridium complex includes a benzo[F]isoquinoline ring having eight substitutable sites, of which 1-3 are non-hydrogen substitutable sites. That is, of these eight substitutable sites, 1-3 are substituted with substitutable groups.

[0053] The general structural formula of the benzo[F]isoquinoline ring with 8 substituted sites is shown below:

[0054]

[0055] Among them, T 11 -T 18 One, two, or three of them are not hydrogen.

[0056] In some implementations (1), T 11 -T 18 If there exists a component that is not hydrogen, then T 11 -T 18 The non-hydrogen alkyl group is selected from deuterium, halogens, -CF3, CN, and substituted or unsubstituted C1-C4 alkyl groups. For substituted C1-C4 alkyl groups, they can be substituted by deuterium, halogens, -CF3, or CN. The C1-C4 alkyl groups involved in this implementation are selected from methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc. The halogens involved in this implementation include fluorine, chlorine, bromine, and iodine.

[0057] Furthermore, as a preferred example, T 11 -T 18 If there exists a component that is not hydrogen, then T 11 -T 18 The non-hydrogen alkyl group is selected from deuterium, fluorine, -CF3, CN, or an unsubstituted C1-C4 alkyl group, wherein the C1-C4 alkyl group is selected from methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl.

[0058] Furthermore, as a preferred example, T 13 T 14 T 15 or T 16 Any one of them is selected from deuterium, fluorine, -CF3, CN, or an unsubstituted C1-C4 alkyl group, wherein the C1-C4 alkyl group is selected from methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl.

[0059] In some implementations (2), T 11 -T 18 If there are two elements in T that are not hydrogen, then... 11 -T 18The two non-hydrogen alkyl groups are each independently selected from deuterium, halogens, -CF3, CN, and substituted or unsubstituted C1-C4 alkyl groups. For substituted C1-C4 alkyl groups, they can be replaced by deuterium, halogens, -CF3, or CN. The C1-C4 alkyl groups involved in this implementation are selected from methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc. The halogens involved in this implementation include fluorine, chlorine, bromine, and iodine.

[0060] Furthermore, as a preferred example, T 14 -T 16 If there are two elements in T that are not hydrogen, then... 14 -T 16 The two non-hydrogen alkyl groups are each independently selected from deuterium, halogens, -CF3, CN, and substituted or unsubstituted C1-C4 alkyl groups. For substituted C1-C4 alkyl groups, they can be replaced by deuterium, halogens, -CF3, or CN. The C1-C4 alkyl groups involved in this implementation are selected from methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc. The halogens involved in this implementation include fluorine, chlorine, bromine, and iodine.

[0061] Furthermore, as a preferred example, T 14 -T 16 At least one of them is selected from F or -CF3.

[0062] In some implementations (3), T 11 -T 18 If there are three elements in T that are not hydrogen, then... 11 -T 18 The three non-hydrogen alkyl groups are each independently selected from deuterium, halogens, -CF3, CN, and substituted or unsubstituted C1-C4 alkyl groups. For substituted C1-C4 alkyl groups, they can be replaced by deuterium, halogens, -CF3, or CN. The C1-C4 alkyl groups involved in this implementation are selected from methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc. The halogens involved in this implementation include fluorine, chlorine, bromine, and iodine.

[0063] Furthermore, as a preferred example, T 13 -T 18 If there are three elements in T that are not hydrogen, then... 13 -T 18The three non-hydrogen alkyl groups are each selected from deuterium, halogens, -CF3, CN, and substituted or unsubstituted C1-C4 alkyl groups. For substituted C1-C4 alkyl groups, they can be replaced by deuterium, halogens, -CF3, or CN. The C1-C4 alkyl groups involved in this implementation are selected from methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc. The halogens involved in this implementation include fluorine, chlorine, bromine, and iodine.

[0064] Furthermore, as a preferred example, T 13 -T 18 At least one of them is selected from F or -CF3.

[0065] In some implementations, T 11 -T 18 At least two of the components are connected to form substituted or unsubstituted C5-C20 carbocyclic groups. For substituted C5-C20 carbocyclic groups, the corresponding substituent is T. 1x T 1x Selected from deuterium, halogens, -CF3, CN, substituted or unsubstituted C1-C4 alkyl groups.

[0066] For ring A, in some implementations, at least two second substituents are connected to each other in ring A to form a substituted or unsubstituted C5-C8 aliphatic ring (which may be saturated or unsaturated), or to form a substituted or unsubstituted C4-C7 heterocyclic compound.

[0067] Furthermore, for the two second substituents that form the above-mentioned C5-C8 aliphatic ring or C4-C7 heterocyclic compound, these two connected second substituents can be located in two adjacent positions.

[0068] In some examples, the heteroatoms included in the substituted or unsubstituted C4-C7 heterocyclic compounds are N, O, or S. That is, N, O, or S atoms substitute for any carbon atom in the aforementioned C5-C8 aliphatic rings.

[0069] In some examples, applicable ring A comprising C5-C8 aliphatic rings can be found in the groups represented by the following general formulas:

[0070]

[0071]

[0072] Wherein, the groups represented by RD-2 to RD-10 can be unsubstituted or substituted, and the R involved in the general formula of RD-2 to RD-10 m That is, represented by a substituent, R mIt can substitute any substituted site on the aliphatic ring, or it can substitute any substituted site on the benzene ring.

[0073] In some examples, R m It may be selected from at least one of deuterium, halogen, -CF3, -CN, substituted or unsubstituted C1-C10 alkyl groups.

[0074] In some examples, the ring A of some applicable heterocyclic compounds including C4-C7 can be found in the groups shown in the following general formulas:

[0075]

[0076]

[0077]

[0078]

[0079] In some examples, the chemical structure of ring A can be as shown in RD-3, RD-6, RD-12, RD-15, and RD-31.

[0080] Furthermore, the chemical structure of ring A can be as shown in RD-3 and RD-6. This type of structure is more advantageous for improving luminescence efficiency, reducing voltage, and extending lifespan.

[0081] In the embodiments of the present invention, R1 and R2 may be the same or different. In some examples, R1 and R2 are each independently a group having the following chemical structural formula.

[0082]

[0083] In some examples, the hydrogen in the R1 and R2 groups shown above can be further substituted, and the corresponding substituents can be, for example, deuterium, halogen, -CF3, CN or C1-C4 alkyl groups, wherein C1-C4 alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc., and halogens include fluorine, chlorine, bromine, iodine.

[0084] Based on the above-described structures of the R1 and R2 groups, the chemical structure of the auxiliary ligand of the iridium complex provided in the embodiments of the present invention can be found in any of the chemical structures shown in RP-1 to RP-20.

[0085]

[0086]

[0087] In some examples, it is preferred to use a main ligand containing the group shown in RD-3 or RD-6 in combination with any of the auxiliary ligands shown in RP-1 to RP-20.

[0088] Furthermore, it is preferable to use a main ligand containing the group shown in RD-3 or RD-6 in combination with any of the auxiliary ligands shown in RP-1, RP-3, RP-7, RP-8, and RP-9.

[0089] The iridium complex obtained based on the above combination is more conducive to improving luminous efficiency, reducing voltage, and increasing brightness. In addition, it has a narrow emission spectrum range, purer color, better stability, and longer service life.

[0090] In some embodiments, the chemical structural formula of the iridium complex provided in the present invention can be found in any of the chemical structures shown in RDP-1 to RDP-48 below:

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100] On the other hand, embodiments of the present invention also provide a method for preparing an iridium complex, the method comprising:

[0101] A main ligand compound and an auxiliary ligand compound are provided, wherein the main ligand compound is used to provide a main ligand for an iridium complex, and the auxiliary ligand compound is used to provide an auxiliary ligand for an iridium complex.

[0102] Dimers were prepared by reacting the host ligand compound with iridium.

[0103] The dimer is reacted with an auxiliary ligand compound to yield an iridium complex. This reaction can be carried out in the presence of potassium carbonate or sodium carbonate.

[0104] The chemical structural formula of the host ligand compound is shown below:

[0105]

[0106] The chemical structural formula of the dimer is shown below:

[0107]

[0108] The chemical structural formula of the auxiliary ligand compound is shown below:

[0109]

[0110] In another aspect, embodiments of the present invention also provide an organic light-emitting device, which includes a light-emitting layer, and the raw materials for preparing the light-emitting layer include the aforementioned iridium complex.

[0111] The organic light-emitting device provided in this embodiment of the invention can emit red light. Based on the use of the above-mentioned iridium complex including oxygen-containing heterocycles, the luminous efficiency and luminous lifetime of the organic light-emitting device are significantly improved, and the organic light-emitting device also has stronger thermal stability.

[0112] Iridium complexes can be used as red light dopants, i.e., emitting dopants, in the emitting layer, working synergistically with the host emitting material to achieve luminescence. In some examples, the mass ratio of the host emitting material to the iridium complex is 90-99:5, such as 91:5, 92:5, 93:5, 94:5, 95:5, 96:5, 97:5, etc.

[0113] For example, the host luminescent material includes at least one of the following groups: triphenylene, carbazole, dibenzothiophene, dibenzofuran, dibenzoselenene, azittriphenylene, azicarbazole, azittriphenylthiophene, azittriphenylfuran, and azittriphenylselenene.

[0114] The organic light-emitting device provided in this embodiment of the invention includes an anode, a cathode, and an organic layer, wherein the organic layer includes at least a light-emitting layer, and the organic layer may further include at least one of a hole injection layer, a hole transport layer, a hole blocking layer, an electron injection layer, and an electron transport layer.

[0115] For example, as shown in the appendix Figure 1 As shown, the organic light-emitting device provided in this embodiment of the invention includes an anode 1, a hole injection layer 2, a hole transport layer 3, an electron blocking layer 4, a light-emitting layer 5, an electron transport layer 6, an electron injection layer 7, and a cathode 8, which are stacked sequentially from bottom to top. The anode 1 is formed on a substrate, which may be, for example, a glass substrate, a ceramic substrate, etc.

[0116] Anode 1, hole injection layer 2, hole transport layer 3, electron blocking layer 4, electron transport layer 6, electron injection layer 7, and cathode 8 can each be made of materials commonly used in the field, and will not be described in detail here.

[0117] Hole injection layer 2, hole transport layer 3, electron blocking layer 4, electron transport layer 6, and electron injection layer 7 can be formed by one of the following methods: vacuum evaporation, molecular beam evaporation, solvent-based dip coating, spin coating, bar coating, or inkjet printing. Anode 1 and cathode 8 can be prepared by evaporation or sputtering.

[0118] In some examples, the organic light-emitting devices provided in the embodiments of the present invention can be used in any of the following electronic devices for display or light emission: computers, tablet computers, televisions, telephones, virtual reality or augmented reality displays, etc.

[0119] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. In the following embodiments, unless otherwise specified, "%" refers to weight percentage.

[0120] Example 1

[0121] Example 1 provides an iridium complex, the chemical structure of which is described in RDP-25 above. The preparation steps and related preparation equations for the iridium complex RDP-25 are shown below.

[0122]

[0123] Step 1: Synthesize intermediate IP-1

[0124] Referring to preparation equation 1-1, tetrahydronaphthol (25.00 g) and pyridine (13.3 g) were added to a flask and dissolved in 250 mL of dichloromethane. Trifluoromethanesulfonic anhydride (49.97 g) was slowly added dropwise while stirring in an ice-water bath. After the addition was complete, stirring was continued for 30 min. The mixture was then filtered, and the filtrate was collected. The solvent was removed by rotary evaporation, and the filtrate was not further purified before proceeding to the next reaction step.

[0125] Step 2: Synthesize intermediate IP-2

[0126] Referring to preparation equation 1-1, intermediate IP-1 obtained in step 1 was added to a flask, followed by the sequential addition of pinacol diborate (51.49 g), potassium carbonate (53.54 g), palladium acetate (100 mg), X-PHOS (400 mg), and potassium bromide (1.99 g). Then, 400 mL of toluene, 200 mL of ethanol, and 200 mL of water were added, and the mixture was heated to reflux and stirred for 4 h. After the reaction was complete, the mixture was extracted with water and ethyl acetate, and the organic phase was collected. Column chromatography was used to separate the organic phase into a white solid intermediate IP-2 (42.43 g), with a total yield of 64.44%.

[0127]

[0128] Step 3: Synthesize intermediate IP-3

[0129] Referring to preparation equations 1-2, 13.00 g of 2-chloro-4-iodopyridin-3-carboxaldehyde, 7.86 g of 3-cyanobenzoic acid, and 8.17 g of sodium bicarbonate were added to a flask, followed by 100 mL of toluene, 50 mL of ethanol, and 50 mL of water. After purging with nitrogen, 50 mg of tetrakis(triphenylphosphine)palladium was added, and the mixture was heated under reflux with stirring for 4 h. After the reaction was complete, the mixture was extracted with water and ethyl acetate, and the organic phase was collected and separated by column chromatography to obtain a white solid intermediate, IP-3 (11.07 g, yield 93.85%).

[0130]

[0131] Step 4: Synthesize intermediate IP-4

[0132] Referring to preparation equations 1-3, take a flask and add methoxymethyltriphenylphosphine chloride (16.95 g) and toluene (150 mL). Add potassium tert-butoxide (6.47 g) in portions under an ice-water bath. After the addition is complete, continue stirring under an ice-water bath for 1 h. Then, add intermediate IP-3 (10.00 g) dissolved in 50 mL of toluene dropwise. After the addition is complete, remove the ice-water bath and continue stirring for 2 h. After the reaction is complete, quench the reaction with water, extract with water and ethyl acetate, and wash several times. Collect the organic phase, and separate the organic phase by column chromatography to obtain a white solid intermediate IP-4 (9.23 g, yield 82.74%).

[0133]

[0134] Step 5: Synthesize intermediate IP-5

[0135] Referring to preparation equations 1-4, take a flask, add intermediate IP-4 (9.00 g) and dichloromethane (80 mL), purge with nitrogen, and then add methanesulfonic acid (25.56 g) dropwise while stirring. After the addition is complete, continue stirring at room temperature for 2 h. After the reaction is complete, quench with water. Extract with dichloromethane and water, collect the organic phase, and separate by column chromatography to obtain a white solid intermediate IP-5 (7.20 g, yield 90.74%).

[0136]

[0137] Step 6: Synthesize ligand RD-1

[0138] Referring to preparation equations 1-5, take a flask and add intermediates IP-5 (7.00 g) and IP-2 (5.28 g), then add toluene (50 mL), ethanol (25 mL), and water (25 mL). Purge with nitrogen and stir. Then add X-PHOS (200 mg) and palladium acetate (50 mg), and heat under reflux for 2 h. Once the reaction is complete, stop heating. Extract with water and ethyl acetate, collect the organic phase, separate by column chromatography, and then recrystallize with ethanol to obtain a white solid ligand RD-1 (8.65 g, yield 95.64%).

[0139]

[0140] Step 7: Synthesize iridium complex RDP-25

[0141] Referring to preparation equations 1-6, take a flask, add ligand RD-1 (2.10 g) and iridium trichloride trihydrate (1.00 g), add 30 mL of ethylene glycol diethyl ether and 10 mL of water, purge with nitrogen, then stir and heat to reflux. After reacting for 24 h, stop heating. After cooling the reaction solution to room temperature, filter, and wash the filter cake three times with water, ethanol, and methyl ether, respectively, and collect the filter cake. Add the collected filter cake to a flask, then add potassium carbonate (1.96 g) and ligand RP-1 (5.36 g), dissolve with 30 mL of dichloromethane, stir under nitrogen protection for 18 h, and stop the reaction when it is detected as complete. Separate by column chromatography, and then slurry with ethanol and n-hexane to obtain 1.79 g of red solid iridium complex RDP-25.

[0142] The prepared iridium complex RDP-25 was subjected to mass spectrometry analysis, as shown below, which indicates that Example 1 successfully synthesized the iridium complex RDP-25 with the desired chemical structure.

[0143] 1H-NMR(400MHz,Chloroform-d)δ8.86(d,J=9.7Hz,2H),8.78–8.71(m,2H),8.20(dd,J=8.9,0.8H z,2H),8.11–8.06(m,2H),7.89–7.80(m,4H),7.56(dd,J=8.7,0.7Hz,2H),7.30–7.23(m,2H),7.0 3(dt,J=10.6,1.0Hz,2H),5.94(d,J=1.8Hz,1H),3.20–3.04(m,4H),2.83–2.70(m,4H),2.74–2.6 3(m,1H),2.49(td,J=8.9,1.8Hz,1H),1.84–1.65(m,8H),1.68–1.46(m,9H),0.93–0.85(m,12H).

[0144] Example 2

[0145] This embodiment 2 provides an iridium complex, the chemical structure of which is shown in RDP-30 above. The preparation steps of the iridium complex RDP-30 and the related preparation equation are as follows.

[0146]

[0147] Refer to preparation equation 2-1 and synthesize intermediate IP-7 according to steps 1-2 in Example 1.

[0148]

[0149]

[0150] Refer to preparation equations 2-2 to 2-4 to synthesize ligand RD-2 according to steps 3-6 in Example 1.

[0151]

[0152] Referring to preparation equation 2-5, the iridium complex RDP-30 was synthesized. A flask was taken, and ligand RD-2 (2.10 g) and iridium trichloride trihydrate (1.00 g) were added. 30 mL of ethylene glycol diethyl ether and 10 mL of water were added, and the mixture was purged with nitrogen. The mixture was then stirred and heated to reflux for 24 h, after which heating was stopped. The reaction solution was cooled to room temperature and filtered. The filter cake was washed three times with water, ethanol, and methyl ether, and collected. The collected filter cake was added to a flask, and potassium carbonate (1.96 g) and ligand RP-1 (5.36 g) were added. The mixture was dissolved in 30 mL of dichloromethane and stirred under nitrogen protection for 18 h. Once the reaction was complete, the reaction was stopped, and the mixture was separated by column chromatography. The solution was then slurried with ethanol and n-hexane to obtain 1.80 g of a red solid iridium complex RDP-30.

[0153] The prepared iridium complex RDP-30 was subjected to mass spectrometry analysis, as shown below, which indicates that Example 2 successfully synthesized the iridium complex RDP-30 with the desired chemical structure.

[0154] 1 H NMR(400MHz,Chloroform-d)δ8.90(d,J=9.7Hz,2H),8.77–8.70(m,2H),8.20(dd,J=9.1,0. 8Hz,2H),8.11–8.06(m,2H),7.83(dd,J=8.8,0.8Hz,2H),7.72(t,J=1.1Hz,2H),7.56(d,J=8 .8Hz,2H),7.30–7.23(m,2H),6.90(t,J=1.0Hz,2H),5.94(d,J=1.7Hz,2H),2.83–2.63(m,10 H), 2.49 (td, J=8.9, 1.8Hz, 2H), 1.81–1.66 (m, 8H), 1.70–1.46 (m, 10H), 0.93–0.85 (m, 12H).

[0155] Example 3

[0156] This embodiment 3 provides an iridium complex, the chemical structure of which is described in RDP-15 above. The preparation steps of the iridium complex RDP-15 and the related preparation equation are shown below.

[0157]

[0158] Refer to preparation equation 3-1, and synthesize intermediate IP-12 according to steps 1-2 in Example 1.

[0159]

[0160]

[0161] Refer to preparation equations 3-2 and 3-5, and synthesize ligand RD-3 according to the methods shown in steps 3-6 of Example 1.

[0162]

[0163] Referring to preparation equations 3-6, the iridium complex RDP-15 was synthesized. A flask was taken, and ligand RD-2 (1.89 g) and iridium trichloride trihydrate (1.00 g) were added. 30 mL of ethylene glycol diethyl ether and 10 mL of water were added, and the mixture was purged with nitrogen. The mixture was then stirred and heated to reflux for 24 h, after which heating was stopped. The reaction solution was cooled to room temperature and filtered. The filter cake was washed three times with water, ethanol, and methyl ether, and collected. The collected filter cake was added to a flask, and potassium carbonate (1.96 g) and ligand RP-1 (5.36 g) were added. The mixture was dissolved in 30 mL of dichloromethane and stirred under nitrogen protection for 18 h. Once the reaction was complete, the reaction was stopped, and the mixture was separated by column chromatography. The solution was then slurried with ethanol and n-hexane to obtain 1.52 g of a red solid iridium complex RDP-15.

[0164] The prepared iridium complex RDP-15 was subjected to mass spectrometry analysis, as shown below. This indicates that Example 3 successfully synthesized the iridium complex RDP-15 with the desired chemical structure.

[0165] 1 H NMR(400MHz,Chloroform-d)δ8.83(d,J=9.8Hz,2H),8.66(d,J=9.6Hz,2H),8.18(dd,J=8.9, 0.7Hz,2H),8.11–8.06(m,2H),7.84–7.73(m,4H),7.58–7.51(m,2H),7.30–7.23(m,2H),7.0 9(dt,J=10.4,1.0Hz,2H),5.93(d,J=1.9Hz,1H),4.10(dt,J=9.1,6.1Hz,4H),2.87–2.63(m, 5H), 2.49 (td, J=8.9, 1.8Hz, 1H), 2.03–1.89 (m, 4H), 1.68–1.47 (m, 9H), 0.93–0.85 (m, 12H).

[0166] Example 4

[0167] Example 4 provides an iridium complex, the chemical structure of which is described above as RDP-26. The preparation steps and related preparation equations for the iridium complex RDP-26 are shown below.

[0168]

[0169]

[0170] Refer to preparation equations 4-1 to 4-4, and synthesize ligand RD-4 according to steps 3-6 in Example 1.

[0171]

[0172] Referring to preparation equations 4-5, the iridium complex RDP-26 was synthesized as 1.64 g of red solid according to step 7 in Example 1.

[0173] The prepared iridium complex RDP-26 was subjected to mass spectrometry analysis, as shown below, which indicates that Example 4 successfully synthesized the iridium complex RDP-26 with the desired chemical structure.

[0174] 1 H-NMR (400MHz, Chloroform-d) δ8.83 (d, J=9.8Hz, 2H), 8.44–8.37 (m, 2H), 7.92–7.85 (m, 2H), 7.85–7.72 (m, 4H), 7.57 (dd, J= 9.0,0.7Hz,2H),7.40(dd,J=8.0,7.4Hz,2H),7.36(ddd,J=7.7,1.5,0.6Hz,2H),7.09(dt,J=10.4,1.0Hz,2H),5.93(d,J=1.9 Hz,1H),4.10(dt,J=9.1,6.1Hz,4H),3.36(heptd,J=4.6,0.7Hz,2H),2.81(dddd,J=12.3,9.5,7.5,1.0Hz,4H),2.70(p,J=9. 5Hz,1H),2.49(pd,J=8.9,1.8Hz,1H),2.03–1.89(m,4H),1.68–1.47(m,9H),1.37(d,J=4.5Hz,12H),0.89(q,J=4.7Hz,12H).

[0175] Example 5

[0176] Example 5 provides an iridium complex, the chemical structure of which is described above as RDP-16. The preparation steps and related preparation equations for the iridium complex RDP-16 are shown below.

[0177]

[0178] Refer to preparation equation 5-1, and synthesize intermediate IP-21 according to the method shown in steps 1-2 of Example 1.

[0179]

[0180]

[0181] Refer to preparation equations 5-2 to 5-5, and synthesize ligand RD-5 according to the method shown in steps 3-6 of Example 1.

[0182]

[0183] Referring to preparation equations 5-6, the iridium complex RDP-16 was synthesized as a red solid (2.11 g) according to step 7 in Example 1.

[0184] The prepared iridium complex RDP-16 was subjected to mass spectrometry analysis, as shown below, which indicates that Example 5 successfully synthesized the iridium complex RDP-16 with the desired chemical structure.

[0185] 1 H NMR(400MHz,Chloroform-d)δ8.86(d,J=9.7Hz,2H),8.78–8.71(m,2H),8.20(dd,J=8.9,0.8Hz,2H),8.11–8. 06(m,2H),7.89–7.80(m,4H),7.56(d,J=8.9Hz,2H),7.30–7.23(m,2H),7.04(dt,J=10.5,1.0Hz,2H),5.94(d, J=1.8Hz,1H),3.01(td,J=11.0,8.2Hz,4H),2.77(dd,J=1.7,1.0Hz,1H),2.74(dd,J=1.6,1.0Hz,2H),2.72(d d,J=1.7,0.8Hz,1H),2.73–2.63(m,1H),2.49(pd,J=8.9,1.8Hz,1H),1.69–1.39(m,21H),0.93–0.85(m,12H).

[0186] Example 6

[0187] Example 6 provides an iridium complex, the chemical structure of which is described above as RDP-20. The preparation steps of the iridium complex RDP-20 and the related preparation equations are shown below.

[0188]

[0189] Referring to preparation equation 6, take a flask, add ligand RD-1 (2.10 g) and iridium trichloride trihydrate (1.00 g), add 30 mL of ethylene glycol diethyl ether and 10 mL of water, purge with nitrogen, then stir and heat to reflux. After reacting for 24 h, stop heating. After cooling the reaction solution to room temperature, filter, and wash the filter cake three times with water, ethanol, and methyl ether, respectively, and collect the filter cake. Add the collected filter cake to a flask, then add potassium carbonate (1.96 g) and ligand RP-9 (5.96 g), dissolve with 30 mL of dichloromethane, stir under nitrogen protection for 18 h, and stop the reaction when it is detected as complete. Separate by column chromatography, and then slurry with ethanol and n-hexane to obtain iridium complex RDP-20, which is a red solid of 1.74 g.

[0190] The prepared iridium complex RDP-20 was subjected to mass spectrometry analysis, as shown below, which indicates that Example 6 successfully synthesized the iridium complex RDP-20 with the desired chemical structure.

[0191] 1 H NMR(400MHz,Chloroform-d)δ8.88(d,J=9.7Hz,2H),8.78–8.70(m,2H),8.20(dd,J=9.1,0.7Hz,2H),8.12–8.05(m,2H) ,7.89–7.79(m,4H),7.56(dd,J=8.8,0.7Hz,2H),7.31–7.22(m,2H),7.03(dt,J=10.6,1.0Hz,2H),5.91(d,J=1.7Hz,1H ),3.20–3.03(m,4H),2.83–2.68(m,4H),2.56(qd,J=7.7,1.8Hz,1H),2.15(dq,J=12.3,4.7Hz,2H),1.84–1.68(m,10H) ,1.71–1.64(m,1H),1.68–1.59(m,3H),1.64–1.54(m,1H),1.59–1.47(m,5H),1.52–1.37(m,1H),1.02(t,J=4.7Hz,6H).

[0192] Example 7

[0193] This embodiment 7 provides an iridium complex, the chemical structure of which is described in RDP-35 above. The preparation steps of the iridium complex RDP-35 and the related preparation equation are shown below.

[0194]

[0195] Referring to Equation 7, take a flask, add ligand RD-1 (2.50 g) and iridium trichloride trihydrate (1.00 g), add 30 mL of ethylene glycol ethyl ether and 10 mL of water, purge with nitrogen, then stir and heat to reflux. Stop heating after 24 h. Cool the reaction solution to room temperature and filter. Wash the filter cake three times with water, ethanol, and methyl ether, and collect the filter cake. Add the collected filter cake to a flask, then add potassium carbonate (1.96 g) and ligand RP-7 (5.96 g), dissolve in 30 mL of dichloromethane, stir under nitrogen protection for 18 h. Stop the reaction when it is detected as complete, separate by column chromatography, and then slurry with ethanol and n-hexane to obtain 2.43 g of red solid, which is the iridium complex RDP-35.

[0196] The prepared iridium complex RDP-35 was subjected to mass spectrometry analysis, as shown below, which indicates that Example 7 successfully synthesized the iridium complex RDP-35 with the desired chemical structure.

[0197] 1 H NMR(400MHz,Chloroform-d)δ8.88(d,J=9.7Hz,2H),8.78–8.70(m,2H),8.20(dd,J=9.0,0.7H z,2H),8.12–8.05(m,2H),7.89–7.79(m,4H),7.56(dd,J=8.8,0.7Hz,2H),7.31–7.22(m,2H), 7.03(dt,J=10.6,1.0Hz,2H),6.06(s,1H),3.20–3.03(m,4H),2.81–2.69(m,4H),2.21–2.08( m,4H),1.84–1.72(m,5H),1.77–1.60(m,6H),1.62(dd,J=4.4,3.0Hz,1H),1.06–0.95(m,13H).

[0198] Example 8

[0199] This embodiment 8 provides an iridium complex, the chemical structure of which is described in RDP-5 above. The preparation steps of the iridium complex RDP-5 and the related preparation equations are shown below.

[0200]

[0201] Referring to preparation equation 8, take a flask, add ligand RD-1 (2.50 g) and iridium trichloride trihydrate (1.00 g), add 30 mL of ethylene glycol diethyl ether and 10 mL of water, purge with nitrogen, then stir and heat to reflux. After reacting for 24 h, stop heating. After cooling the reaction solution to room temperature, filter, and wash the filter cake three times with water, ethanol, and methyl ether, respectively, and collect the filter cake. Add the collected filter cake to a flask, then add potassium carbonate (1.96 g) and ligand RP-3 (5.96 g), dissolve with 30 mL of dichloromethane, stir under nitrogen protection for 18 h, and stop the reaction when it is detected as complete. Separate by column chromatography, then slurry with ethanol and n-hexane to obtain 2.36 g of red solid, which is the iridium complex RDP-5.

[0202] The prepared iridium complex RDP-5 was subjected to mass spectrometry analysis, as shown below, which indicates that Example 8 successfully synthesized the iridium complex RDP-5 with the desired chemical structure.

[0203] 1 H NMR(400MHz,Chloroform-d)δ8.86(d,J=9.7Hz,2H),8.78–8.71(m,2H),8.20(dd, J=9.1,0.8Hz,2H),8.12–8.05(m,2H),7.89–7.79(m,4H),7.56(dd,J=8.8,0.7Hz, 2H),7.31–7.22(m,2H),7.03(dt,J=10.5,1.0Hz,2H),5.93(d,J=1.8Hz,1H),3.21 –3.03(m,4H),2.83–2.65(m,5H),2.51(pd,J=7.7,1.8Hz,1H),1.85–1.37(m,27H).

[0204] Application Example 1

[0205] Application Example 1 uses the iridium complex RD-25 prepared in Example 1 to prepare an organic electroluminescent device, which includes the following layers stacked in sequence: glass / anode / hole injection layer / hole transport layer / electron blocking layer / light emitting layer / electron transport layer / electron injection layer / cathode.

[0206] The fabrication method of this organic electroluminescent device is as follows:

[0207] (1) The transparent conductive ITO glass substrate with an anode (China Southern Glass Group Co., Ltd.) was ultrasonically treated in a commercial cleaning agent, rinsed in deionized water, and then washed with ethanol, acetone and deionized water in sequence. It was baked in a clean environment until all moisture was removed, cleaned with ultraviolet photosynthetic ozone, and then treated with oxygen plasma for 30 seconds.

[0208] (2) The pretreated transparent conductive ITO glass substrate with an anode is placed in a vacuum chamber, a vacuum is drawn, and HIL compound is deposited on the surface of the ITO anode as a hole injection layer at a deposition rate of 0.1 nm / s.

[0209] (3) The compound HT was vapor-deposited on the surface of the hole injection layer to form a hole transport layer with a thickness of 100 nm and a deposition rate of 0.1 nm / s.

[0210] (4) The compound EB was deposited on the surface of the hole transport layer to form a 10 nm thick electron blocking layer at a deposition rate of 0.1 nm / s.

[0211] (5) A 40 nm thick light-emitting layer is deposited on the surface of the electron blocking layer, wherein 95% by weight of compound RH is used as the host light-emitting material and 5% by weight of iridium complex RD-25 is used as the dopant guest material, and the deposition rate is 0.1 nm / s.

[0212] (6) A 35 nm thick compound ET:Liq (weight ratio of 50:50) was deposited on the surface of the light-emitting layer as an electron transport layer at a deposition rate of 0.1 nm / s.

[0213] (7) A 1 nm thick LiQ layer is deposited on the surface of the electron transport layer as an electron injection layer and a 100 nm thick Al layer is deposited as a cathode.

[0214] The chemical structural formulas of the various compounds involved in this organic electroluminescent device are shown below:

[0215]

[0216] Comparative Example 1

[0217] The difference between Comparative Example 1 and Application Example 1 is that, in the fabrication of the organic electroluminescent device, the iridium complex RDP-25 was replaced with compound Ir-1.

[0218] The chemical structural formula of compound Ir-1 is shown below:

[0219]

[0220] Comparative Example 2

[0221] The difference between Comparative Example 2 and Application Example 1 is that, in the fabrication of the organic electroluminescent device, the iridium complex RDP-25 was replaced with compound Ir-2.

[0222] The chemical structural formula of compound Ir-2 is shown below:

[0223]

[0224] Application Example 2

[0225] The difference from Application Example 1 is that when preparing the organic electroluminescent device, the iridium complex RDP-25 is replaced with the iridium complex RDP-30, while the other preparation processes are the same.

[0226] Application Example 3

[0227] The difference from Application Example 1 is that when preparing the organic electroluminescent device, the iridium complex RDP-25 is replaced with the iridium complex RDP-15, while the other preparation processes are the same.

[0228] Application Example 4

[0229] The difference from Application Example 1 is that when preparing the organic electroluminescent device, the iridium complex RDP-25 is replaced with the iridium complex RDP-26, while the other preparation processes are the same.

[0230] Application Example 5

[0231] The difference from Application Example 1 is that when preparing the organic electroluminescent device, the iridium complex RDP-25 is replaced with the iridium complex RDP-16, while the other preparation processes are the same.

[0232] Application Example 6

[0233] The difference from Application Example 1 is that when preparing the organic electroluminescent device, the iridium complex RDP-25 is replaced with the iridium complex RDP-20, while the other preparation processes are the same.

[0234] Application Example 7

[0235] The difference from Application Example 1 is that when preparing the organic electroluminescent device, the iridium complex RDP-25 is replaced with the iridium complex RDP-35, while the other preparation processes are the same.

[0236] Application Example 8

[0237] The difference from Application Example 1 is that when preparing the organic electroluminescent device, the iridium complex RDP-25 is replaced with the iridium complex RDP-5, while the other preparation processes are the same.

[0238] Test case

[0239] Using a Photo Research PR650 spectrometer, the above-mentioned organic electroluminescent devices were tested at 10 mA / cm². 2 The operating voltage, current efficiency, and CIE coordinates of the organic electroluminescent device at a current density of 50 mA / cm² were determined. 2The ratio of the brightness to the initial brightness after 150 hours of operation at a given current density is LT(150) value, where the initial brightness is defined as 100%. The LT(150) value represents the degree of brightness decay relative to the initial brightness after 150 hours of operation, and is used to characterize the stability of the organic electroluminescent device. The test results are shown in Table 1.

[0240] Table 1

[0241] project Iridium complex Voltage (V) Current efficiency (cd / A) LT(150)(%) Application Example 1 RDP-25 3.41 21.62 95.79 Application Example 2 RDP-30 3.36 23.21 96.84 Application Example 3 RDP-15 3.57 20.85 92.41 Application Example 4 RDP-26 3.53 20.99 93.97 Application Example 5 RDP-16 3.51 20.57 93.10 Application Example 6 RDP-20 3.50 24.16 93.63 Application Example 7 RDP-35 3.43 24.83 92.39 Application Example 8 RDP-5 3.42 23.49 97.23 Comparative Example 1 Ir-1 3.51 18.37 75.65 Comparative Example 2 Ir-2 3.64 15.73 81.90

[0242] As shown in Table 1, the use of the iridium complex provided in the embodiments of the present invention reduces the operating voltage of the organic electroluminescent device, improves the luminous efficiency, enhances the stability of the device, and effectively extends the device lifespan.

[0243] The above description is merely for the purpose of enabling those skilled in the art to understand the technical solutions of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An organic light-emitting device, characterized in that, The organic light-emitting device includes a light-emitting layer, and the raw materials for preparing the light-emitting layer include an iridium complex and a host light-emitting material; The mass ratio of the host luminescent material to the iridium complex is 90. 99:5; The chemical structural formula of the iridium complex is shown below: ； Where p≥1, R a The first substituent represents a first substituent, and when there are multiple first substituents, the multiple first substituents may be the same or different. The first substituent is selected from at least one of deuterium, halogen, -CF3, -CN, substituted or unsubstituted C1-C4 alkyl groups, and the C1-C4 alkyl group can be substituted by deuterium, halogen, -CF3 or -CN. The chemical structural formula of ring A is shown in any of the following: ； ； Wherein, the auxiliary ligand of the iridium complex is ; The chemical structural formula of the auxiliary ligand is as follows: RP 1 to RP Any of the 20 shown:

2. The organic light-emitting device according to claim 1, characterized in that, The iridium complex comprises a benzo[F]isoquinoline ring with eight substituted sites, and its general structural formula is shown below: ； Among them, T 11 -T 18 One, two, or three of them are not hydrogen.

3. The organic light-emitting device according to claim 2, characterized in that, T 13 T 14 T 15 and T 16 If there exists a component that is not hydrogen, then T 13 T 14 T 15 and T 16 The non-hydrogen alkyl group is selected from deuterium, halogen, -CF3, CN, or substituted or unsubstituted C1-C4 alkyl groups.

4. The organic light-emitting device according to claim 2, characterized in that, T 14 -T 16 If there are two elements in T that are not hydrogen, then... 14 -T 16 The two non-hydrogen atoms are each independently selected from deuterium, halogen, -CF3, CN, or substituted or unsubstituted C1-C4 alkyl groups.

5. The organic light-emitting device according to claim 2, characterized in that, T 13 -T 18 If there are three elements in T that are not hydrogen, then... 13 -T 18 The three non-hydrogen groups are each selected from deuterium, halogen, -CF3, CN, and substituted or unsubstituted C1-C4 alkyl groups.

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