JP5567286B2 - Organic electroluminescence device - Google Patents

Description

  The present invention relates to an organic electroluminescent element (hereinafter also referred to as “organic EL element”).

  In recent years, organic electroluminescence devices have been actively researched and developed because they can emit light with high luminance when driven at a low voltage. In general, an organic EL element is composed of an organic layer including a light emitting layer and a pair of electrodes sandwiching the layer. Electrons injected from the cathode and holes injected from the anode are recombined in the light emitting layer and generated. The energy of the excitons is used for light emission.

  Each thin layer of the organic EL element is formed by a spin coating method or a vapor deposition method for low molecules. In addition, a method of forming a thin film of a device material precursor by spin coating as in Patent Document 2 and then forming a film of the device material by exposure to an electric field, light irradiation, or the like has been reported.

  However, many low molecular weight materials using vapor deposition have a low boiling point and low glass transition temperature (hereinafter referred to as Tg), and exposure of the produced film to high temperature conditions may cause changes in crystallization and film quality. there were. This is due to the nature of the molecules trying to rearrange with kinetic energy. As a result, the element after heating may not be able to maintain the light emission characteristics, for example, it may not emit light partially before the heating, and the luminance may decrease.

  In order to solve such a problem, not only the molecular weight is increased, but also a structure having many free rotation sites for suppressing the molecules from taking a crystal arrangement is required. However, most of the materials widely used for organic EL device materials have rigid structures in which aromatic rings such as benzene are directly connected for the purpose of adjoining π bonds in order to maintain high charge transportability. Met. For this reason, sp3 carbon etc. which can rotate freely with organic EL element material were not used for a connection group.

  Patent Document 1 reports a fluorescent light-emitting material in which thiophene rings having high charge transporting properties are connected by an arylene group. In this report, the thiophene ring is directly connected or connected by a benzene ring, and there is no description about the light emission stability under thermal aging. In this means, the problem of film quality change at high temperatures is not solved because there is no free rotation between the arylene group and the thiophene ring and the whole molecule is rigid.

Patent Document 2 reports a polymer in which compounds using an aromatic hetero 5-membered ring such as a thiophene ring or a pyrrole ring are linked by various methods.
However, in order to form a film by the cationic polymerization method described in Patent Document 2, the terminal 2-position of the thiophene ring must be unsubstituted, and the film is formed by vapor deposition without protecting the chemically active site. Is considered difficult to form.
In addition, a compound using methylene or silylene as a linking group is in no way distinguished from a compound using a single bond or an arylene bond, and there is no description about uncoupling the linking group. Further, no investigation has been made under high temperature conditions.

  In the above-mentioned literature, it is assumed that any compound using a hetero 5-membered ring is used as a fluorescent material.

International Publication No. 04/58850 Pamphlet JP 2007-19462 A

Use organic EL elements for applications such as personal computer displays that store heat when driven for long periods of time, in-vehicle displays that are exposed to high temperature conditions when not driven, and other electronic devices that are used under high temperature conditions such as organic thin-film solar cells. In this case, it is required that even if the device is exposed to a high temperature condition, the device can emit light without impairing its light emission characteristics.
An object of the present invention is to provide an organic electroluminescent device that does not impair the luminescent properties even when exposed to high temperature conditions.

As a result of various studies, the present inventors have found that a compound in which an aromatic hetero 5-membered ring such as thiophene or pyrrole is linked by a non-conjugated linking group has sufficient charge transportability as an organic EL device material. Moreover, when these compounds were used in the device and driven under high temperature conditions, they were successfully driven without impairing their light emission characteristics. Based on this knowledge, it discovered that the said subject was solved by the invention using the compound of the following structure.
Furthermore, it has been found that an element that emits light with higher luminance can be obtained by using in combination with a light emitting material, particularly a phosphorescent material.

That is, the present invention is as follows.
[1]
An organic electroluminescence device having an organic layer including a light emitting layer between a pair of electrodes, wherein the compound represented by the following general formula (1) is contained in any one of the organic layers. Organic electroluminescent device.

(N represents an integer of 1 to 7.
Each R independently represents a substituent.
m and o each independently represents an integer of 0 to 2.
X represents each independently a sulfur atom, an oxygen atom, or NR ¹ .
Y ₁ each independently represents a substituent.
L _a represents a linking group selected from O, S, Sir ³¹ r ³² , NR ¹ or alkylene, or a combination thereof. Here, R ¹ represents any ^one of hydrogen, an alkyl group, an aryl group, and a heterocyclic group. r ³¹ and r ³² each independently represents a hydrogen atom, an alkyl group, an aryl group, a halogen atom, a cyano group or a heterocyclic group. )
[2]
Formula (1) in _{L a} is ^CR 21 ^{R 22} or ^{Sir 31 r 32 (R 21,} R 22, r 31, r 32 are independently a hydrogen atom, an alkyl group, an aryl group, a halogen atom, a cyano group, a hetero The organic electroluminescent element according to [1], wherein the organic electroluminescent element represents any one of cyclic groups.
[3]
The organic electroluminescent element as described in [1] or [2], wherein X in the general formula (1) is a sulfur atom.
[4]
The organic electroluminescent element as described in [3], wherein the compound represented by the general formula (1) is represented by the general formula (2).

(N represents an integer of 1 to 7. Y ₂ and L _b each independently represent either a carbon atom or a silicon atom. R ³ and R ⁴ each independently represent a substituent.)
[5]
The organic electroluminescent element according to any one of [1] to [4], wherein the light emitting layer contains both a phosphorescent material and a compound represented by the general formula (1).
[6]
The organic electroluminescent element as described in [5], wherein the phosphorescent material is a platinum complex.
[7]
The organic electroluminescent element as described in [6], wherein the platinum complex is represented by the following general formula (3).

(L represents a divalent linking group.
X ¹ represents a sulfur atom, a phosphorus atom, an oxygen atom or a nitrogen atom.
X ² represents a carbon atom, a sulfur atom or a phosphorus atom.
R ⁵ , R ⁶ and R ⁷ each independently represents a substituent, and a, b and c each independently represent an integer of 0 to 3. )
[8]
The phosphor layer includes a phosphorescent material, a compound represented by the general formula (1), and a compound represented by the general formula (4-1) or (4-2). The organic electroluminescent device according to any one of [1] to [7].

(D and e represent an integer of 0 to 3, at least one is 1 or more. F represents an integer of 1 to 3. R ⁸ represents a carbazole group represented by the following general formula (5). )

_{(R 9} each independently represents a substituent, g represents an integer of 0-8.)
[9]
A charge transporting compound represented by formula (2).

(N represents an integer of 1 to 7. Y ₂ and L _b each independently represent either a carbon atom or a silicon atom. R ³ and R ⁴ each independently represent a substituent.)

  According to the organic EL device of the present invention, even if the device is exposed to a high temperature condition, it can emit light without impairing its light emission characteristics. In the organic EL device of the present invention, by using an aromatic hetero five-membered ring, sufficient charge transporting property to be used for an organic EL device can be obtained even if it is a non-conjugated connection structure which is generally considered unsuitable as a charge transport material. Can be secured.

  The organic electroluminescent element of the present invention is an organic electroluminescent element having an organic layer including a luminescent layer between a pair of electrodes, and a compound represented by the following general formula (1) is added to any one of the organic layers. Contained.

(In general formula (1), n represents the integer of 1-7.
Each R independently represents a substituent.
m and o each independently represents an integer of 0 to 2.
X represents each independently a sulfur atom, an oxygen atom, or NR ¹ .
Y ₁ each independently represents a substituent.
L _a represents a linking group selected from O, S, Sir ³¹ r ³² , NR ¹ or alkylene, or a combination thereof. Here, R ¹ represents any ^one of a hydrogen atom, an alkyl group, an aryl group, and a heterocyclic group. r ³¹ and r ³² each independently represents a hydrogen atom, an alkyl group, an aryl group, a halogen atom, a cyano group or a heterocyclic group. )

n represents an integer of 1 to 7. From the viewpoint of maintaining the molecular weight that can be deposited, n = 1 to 3 is preferable from the viewpoint of ease of synthesis and improving purity, and n = 1 is more preferable. M and o each independently represent an integer of 0 to 2, preferably m = o = 0.
Each R independently represents a substituent, and the total number of carbon atoms preferably does not exceed 30 from the viewpoint of providing a vapor-depositable material.
The substituents represented by R are each independently an alkyl group (methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, etc.), an alkenyl group (vinyl). , Allyl, 2-butenyl, 3-pentenyl, etc.), alkynyl group (propargyl, 3-pentynyl, etc.), aryl group (phenyl, p-methylphenyl, naphthyl, anthranyl, etc.), amino group (amino, methylamino, dimethylamino) , Diethylamino, dibenzylamino, diphenylamino, ditolylamino, etc.), alkoxy groups (methoxy, ethoxy, butoxy, 2-ethylhexyloxy, etc.), aryloxy groups (phenyloxy, 1-naphthyloxy, 2-naphthyloxy, etc.), Heterocycle Xyl group (pyridyloxy, pyrazyloxy, pyrimidyloxy, quinolyloxy etc.), acyl group (acetyl, benzoyl, formyl, pivaloyl etc.), alkylthio group (methylthio, ethylthio etc.), arylthio group (phenylthio etc.), heterocyclic thio group (pyridylthio, 2-benzimidazolylthio, 2-benzoxazolylthio, 2-benzthiazolylthio, etc.), halogen atoms (eg fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, nitro group, heterocyclic group ( Examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom. Specifically, imidazolyl, pyridyl, quinolyl, furyl, thienyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzthiazolyl, etc.), silyl group (trimethyl) And preferably an alkyl group, aryl group, alkoxy group, aryloxy group, heterocyclic oxy group, halogen atom, cyano group, nitro group, heterocyclic group, silyl group, and Preferred are an alkyl group, an aryl group, a halogen atom, a cyano group, a heterocyclic group, and a silyl group, and most preferred are an alkyl group and an aryl group. The alkyl group and the aryl group are preferably those having 14 or less carbon atoms, and the alkyl group is preferably one in which the substitution position is a quaternary carbon. In addition, these substituents may be substituted with further substituents.

  When the same 5-membered ring has two substituents, they may be bonded to each other to form a ring, and examples thereof include the following structures.

Each X independently represents any ^one of an oxygen atom, a sulfur atom, and NR ¹ , and a sulfur atom is preferred from the viewpoint of having an appropriate energy gap and maintaining charge injection at the layer interface.

R ¹ represents a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group, preferably a substituted or unsubstituted alkyl group having 10 or less carbon atoms (methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, etc.), substituted or unsubstituted aryl groups having 10 or less carbon atoms (phenyl, p-methylphenyl, naphthyl, anthranyl, etc.), or substitutions having 9 or less carbon atoms Or an unsubstituted heterocyclic group (for example, nitrogen atom, oxygen atom, sulfur atom as a hetero atom, specifically, imidazolyl, pyridyl, quinolyl, furyl, thienyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, Benzthiazolyl). R ¹ is stable and has a molecular weight such as methyl, ethyl, iso-propyl, phenyl, pyridyl, etc. from the viewpoint of suppressing the increase in crystallinity of the material due to the bulky aromatic rings trying to overlap while maintaining chemical stability. Are preferred.

Y ₁ independently represents a substituent, and examples of the substituent represented by Y ₁ include the substituent in R. Y ₁ is preferably _one that forms a rigid bond and has low thermal decomposability for the purpose of protecting the polymerization active site from the heat of vapor deposition, energy during driving, and electric charge and suppressing decomposition. Specific examples of Y ₁ include an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a heterocyclic oxy group, a heterocyclic group, and a silyl group. From the above viewpoint, Y ₁ represents Ar, a heterocyclic group, and CR ²¹ R. ²² R ²³ and Sir ³¹ r ³² r ³³ are preferred, and Y ₁ = CR ²¹ R ²² R ²³ or Sir ³¹ r ³² r ³³ is most preferred.

L _a represents ^{what O, S, Sir 31 r 32} , NR 1 or backbone is constructed by combining a linking group, or they are selected from alkylene of 1 to 6 carbon atoms. It is desirable that approaching a charge transport hetero 5-membered rings in smooth intramolecular order to perform each other, _{L a} is ^{CR 21 R 22, O, S} , Sir 31 r 32, NR 1 are preferred, chemical stability it is most preferable in view of sex _{L a} is ^CR 21 ^{R 22} or ^Sir 31 ^{r 32.}

R ²¹ , R ²² and R ²³ each independently represents a hydrogen atom, an alkyl group, an aryl group, a halogen atom, a cyano group or a heterocyclic group. It may be unsubstituted or substituted, preferably an alkyl group (methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, Cyclohexyl, etc.), aryl groups (phenyl, p-methylphenyl, naphthyl, anthranyl, etc.), heterocyclic groups (hetero atoms include, for example, nitrogen, oxygen and sulfur atoms, specifically imidazolyl, pyridyl, quinolyl, Furyl, thienyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzthiazolyl and the like, more preferably a substituted or unsubstituted alkyl group having 10 or less carbon atoms, and a substituted or unsubstituted aryl group having 10 or less carbon atoms. It is. Among them, more preferred are methyl, ethyl, iso-propyl, tert-butyl, phenyl and pyridyl, and particularly preferred are methyl and phenyl.
As the substituents exemplified as r ³¹ , r ³² and r ³³ , the same groups as those described for R ²¹ , R ²² and R ²³ can be mentioned, and preferred ranges are also the same.

Formula (1) in _{L a} is ^CR 21 ^{R 22} or ^{Sir 31 r 32 (R 21,} R 22, r 31, r 32 each independently represent a hydrogen atom, an alkyl group, an aryl group, a halogen atom, a cyano group, a hetero Represents any of the cyclic groups).

  In the present invention, the compound represented by the general formula (1) is preferably represented by the following general formula (2). Since the compound represented by the general formula (2) does not have a substituent at the 3- and 4-positions of the hetero 5-membered ring, other molecules can approach the 5-membered ring, and therefore, it is electrified transport. This is advantageous in that it does not interfere with performance.

(In General Formula (2), n represents an integer of 1 to 7. Y ₂ and L _b each independently represent either a carbon atom or a silicon atom. R ³ and R ⁴ each independently represents a substituent. Represents.)

n represents an integer of 1 to 7, and a preferred range is the same as in the general formula (1).
Y ₂ and L _b each independently represent either a carbon atom or a silicon atom.
L _b is preferably a carbon atom. This is because the use of a carbon atom having a small atomic radius is advantageous for charge transport because the thiophene ring is closer in distance.
R ³ and R ⁴ each independently represents a substituent. Even if it is unsubstituted, it may have a substituent and the thing similar to the substituent which R < ²¹ >, R <^22> , R < ²³ > represents can be mentioned. Preferably, it represents an alkyl group having 10 or less carbon atoms or an aryl group having 10 or less carbon atoms.

  Further, the compound represented by the general formula (2) is preferably represented by the following general formula (5). The compound represented by the following general formula (5) is easier to synthesize and higher in purity than a compound in which three or more thiophenes are linked. In synthesizing these low crystallinity compounds, column chromatography is generally used. However, when composing a compound in which many thiophenes are connected, by-products having different thiophene numbers must be removed. The compound represented by the general formula (5) is advantageous because it does not generate such a by-product.

(In the general formula _{(5), Y 2, L} b, R 3, R 4 is _Y 2 in the general formula _(2), L ^b, and R 3, ^{R 4} synonymous.)

  The compounds represented by the general formulas (1), (2), and (5) of the present invention preferably form a thin layer by a vacuum deposition process, but a wet process such as solution coating is also preferably used. I can do it. The molecular weight of the compound is preferably 2000 or less, more preferably 1200 or less, and particularly preferably 1000 or less from the viewpoints of deposition suitability and solubility. Also, from the viewpoint of vapor deposition suitability, if the molecular weight is too small, the vapor pressure becomes small, the change from the gas phase to the solid phase does not occur, and it is difficult to form an organic layer. More preferably, 400 or more is particularly preferable.

[Compound represented by formula (2)]
The present invention also relates to a compound represented by the following general formula (2). The compound represented by the general formula (2) is useful as a charge transporting compound.

(In General Formula (2), n represents an integer of 1 to 7. Y ₂ and L _b each independently represent either a carbon atom or a silicon atom. R ³ and R ⁴ each independently represents a substituent. Represents.)
Illustrative and preferred in formula (2) _n, in Y _2, L _b, ^{R 3} and ^{R 4} are the same as _{n, Y 2, L b,} R 3 and ^{R 4} in the general formula.

The compounds exemplified as the compounds represented by the above general formulas (1), (2), and (5) are, for example, Heterocyclic Chemistry (1992) 523, Chemical Abstract (195) 5430, JCS Perkin Transaction I (1976) 897. It can be synthesized by the method described on the page or a combination thereof. Moreover, the hetero 5-membered ring compound bridge | crosslinked with the quaternary methylene can be obtained by heating various hetero 5-membered rings and ketones in 75% sulfuric acid. Although this reaction proceeds without a solvent, acetic acid, polyphosphoric acid, dilute sulfuric acid and the like may be used as a solvent depending on the material used.
Especially the compound illustrated as a compound represented by (2) is compoundable by combining the method shown below.

  When synthesizing compounds having different substituents on silicon, the corresponding chlorosilicon compound may be used as a reactant.

  When synthesizing a compound in which the substituents at both ends are one-sided silicon or one-sided carbon, a carbon substituent may be introduced after using the following reaction.

  In order to synthesize a compound having four or more thiophene rings, these reactions are combined and repeated.

  Specific examples of the compounds represented by the general formulas (1), (2), and (5) in the present invention are illustrated below, but the present invention is not limited thereto.

The function of the compound represented by the general formula (1) is not limited, and the compound represented by the general formula (1) may be any one other than the layer containing the compound when there are a plurality of organic layers. This layer can also be contained. The compound represented by the general formula (1) is more preferably contained in the light emitting layer, and further preferably contained in the light emitting layer as a host material. The light emitting material may be used singly or in combination of two or more, but it is particularly preferable that the light emitting material is contained in the light emitting layer together with at least one light emitting material.
When contained as a host material in the light emitting layer, the total content of the host material in the light emitting layer is preferably 50 to 99.9% by mass, and more preferably 60 to 98% by mass. When the compound of the present invention and one or more host materials are further contained, the weight ratio of the compound of the present invention and the other host materials as a whole is preferably close to the same amount, preferably 20:80 to 50:50 35:65 to 50:50 is more preferable, and 40:60 to 50:50 is most preferable. In this case, it is preferable that the compound of this invention is a main component (component with most content) in a light emitting layer. Moreover, when it contains in a positive hole injection layer, a positive hole transport layer, an electron block layer, a positive hole block layer, an electron transport layer, and an electron injection layer, the content rate of the compound of this invention in each layer is 70 to 100%. It is preferably 85% to 100%, and most preferably 99% to 100%. The compound of the present invention is excellent in hole transportability as well as thermal aging stability and has a large ionization potential. Therefore, the compound of the present invention is preferably used as a hole injection layer, a hole transport layer, or an electron block layer, and used as a hole transport layer. Is most preferred. When the compound of the present invention is used as the hole transport layer, it is preferable that the light emitting layer also contains the compound of the present invention from the viewpoint of simplification of device fabrication.
The light emitting material may be a fluorescent light emitting material or a phosphorescent light emitting material, and particularly preferably a phosphorescent light emitting material.

The fluorescent light emitting material and the phosphorescent light emitting material are described in detail in, for example, Japanese Patent Application Laid-Open No. 2008-270736 and Japanese Patent Application Laid-Open No. 2007-266458, and the matters described in these documents can be applied to the present invention.
Preferred phosphorescent materials include Ir complex, Pt complex, Cu complex, Re complex, W complex, Rh complex, Ru complex, Pd complex, Os complex, Eu complex, Tb complex, Gd complex, Dy complex, and Ce complex. Can be mentioned.
Particularly preferred are Ir complexes and Pt complexes. When the Ir complex is used at the same time as the compound of the present invention, the driving voltage is larger than that of the platinum complex. Regarding this, the Ir complex usually has an octahedral 6-coordinated structure and has a large surface area and a bulky structure. Therefore, it is considered that the Ir complex is not close to the compound of the present invention and charge transfer is hindered. .
The metal complex preferably contains at least one coordination mode of a metal-carbon bond, a metal-nitrogen bond, a metal-oxygen bond, and a metal-sulfur bond. Further, from the viewpoint of luminous efficiency and driving durability, a platinum complex is preferable, and a platinum complex containing a tetradentate multidentate ligand is particularly preferable.

  The platinum complex containing a tetradentate multidentate ligand is preferably a compound represented by the general formula (3).

(In General Formula (3), L represents a divalent linking group. X ¹ represents a sulfur atom, a phosphorus atom, an oxygen atom or a nitrogen atom. X ² represents a carbon atom, a sulfur atom or a phosphorus atom. R ⁵ and R ⁶ each independently represents a substituent, R ⁷ represents a substituent, and a, b and c each independently represents an integer of 0 to 3.)

L represents a divalent linking group. In the platinum tetradentate complex, all the bonds from platinum are on the same plane, and the entire complex has a planar structure. Therefore often π orbitals and dipole moment of the ligand, the interaction of d _z orbital of platinum, it is known to make aggregates of the complex (Sankyo Shuppan, metal complex photochemical, 101 pp -103 pp ). Aggregates have a narrow energy gap, leading to sharp emission spectra and poor emission efficiency. If L is low in polarity, the polar moment of the molecule becomes small, and association light emission between complexes can be suppressed. Specific examples of L include alkylene groups (methylene, ethylene, propylene, etc.), arylene groups (phenylene, naphthalenediyl), heteroarylene groups (pyridinediyl, thiophenediyl, etc.), imino groups (—NR—) (phenylimino groups). ), Oxy group (-O-), thio group (-S-), phosphinidene group (-PR-) (phenylphosphinidene group etc.), silylene group (-Sirr'-) (dimethylsilylene group, diphenylsilylene) Group), or a combination thereof. These linking groups may further have a substituent.
L is preferably an alkylene group (methylene, ethylene, propylene, etc.), an arylene group (phenylene, naphthalenediyl), a heteroarylene group (pyridinediyl, thiophenediyl, etc.), a silylene group (-Sirr'-) (r, r ' Examples of the substituent include those similar to R ^21, and preferred ranges are also the same, such as dimethylsilylene group, diphenylsilylene group, etc., and more preferably a methylene group.

X ¹ represents a sulfur atom, a phosphorus atom, an oxygen atom or a nitrogen atom, and these may have a substituent.
X ¹ is preferably an atom that forms a bond rigidly with platinum, specifically an oxygen atom or a nitrogen atom. More preferred is an oxygen atom.
X ² represents a carbon atom, a sulfur atom or a phosphorus atom, and these may have a substituent.
When X ² is a carbon atom, the carbon atom may form a carbonyl group, an imino group or a thiocarbonyl group. When the carbon atom has a substituent, specific examples of the substituent include an alkyl group, an aryl group, an alkoxy group, and an aryloxy group.
When X ² is a sulfur atom or a phosphorus atom, specific examples of the substituent include an alkyl group, an aryl group, an alkoxy group, and an aryloxy group.
When X ² is a sulfur atom, it is preferably a divalent or hexavalent sulfur atom from the viewpoint of chemical stability. The sulfur atom may form a sulfonyl group.
When X ² is a phosphorus atom, it is preferably a pentavalent phosphorus atom from the viewpoint of stability. When the phosphorus atom is pentavalent, an unsubstituted or substituted phosphoryl group may be formed. X ² is preferably a carbon atom from the viewpoint of thermal stability, and most preferably the carbon atom forms a carbonyl group.
Further, these X ¹ and X ² do not form a ring with each other.

R ⁵ and R ⁶ each independently represents a substituent. a and b each independently represents an integer of 0 to 3; When a and b are integers of 2 or more, R ⁵ and R ⁶ may be the same as or different from each other. R ⁵ and R ⁶ are specifically halogen atoms, cyano groups, silyl groups, alkylamino groups, arylamino groups, alkyl groups, aryl groups, heteroaryl groups, alkoxy groups, and aryloxy groups, preferably Is a halogen atom, a cyano group, a dialkylamino group, or an alkyl group. The alkyl group and dialkylamino group preferably have 1 to 20 carbon atoms from the viewpoint of not increasing the molecular volume too much.
R ⁷ represents a substituent. c is represented by an integer of 0 to 3. When c is an integer of 2 or more, R ⁷ may be the same as or different from each other. R ⁷ is specifically a halogen atom, cyano group, silyl group, alkylamino group, arylamino group, alkyl group, aryl group or heteroaryl group, preferably a halogen atom, cyano group or alkyl group. is there.
The following structure is mentioned as a preferable aspect of the coupling | bonding position and the number of bonds of the substituent of the compound represented by General formula (3).

(In the general formulas (IIId), (IIIe), and (IIIf), L, X ¹ , X ² , R ⁵ , R ⁶ , R ⁷ , a, b, c are L, X ¹ in the general formula (3)). , X ² , R ⁵ , R ⁶ , R ⁷ , a, b, c.

  The compound illustrated as a compound represented by General formula (3) can be manufactured according to the process similar to what is shown, for example in Unexamined-Japanese-Patent No. 2006-261623.

  The compound represented by the general formula (3) of the present invention is prepared by using an organic electroluminescence device by a vacuum deposition process or a solution coating process, and is preferably 2000 or less from the viewpoint of deposition suitability and solubility. More preferably, it is 1200 or less, and particularly preferably 1000 or less. Further, from the viewpoint of vapor deposition suitability, if the molecular weight is too small, the vapor pressure becomes small, the change from the gas phase to the solid phase does not occur, and it is difficult to form an organic layer. Is more preferable, and 400 or more is particularly preferable.

  Specific examples of the compound represented by the general formula (3) in the present invention are illustrated below, but the present invention is not limited thereto.

  In the following description of the general formulas (1), (2), (3) and (5), the hydrogen atom also includes isotopes (deuterium atoms, etc.), and the atoms constituting the substituent are also the isotopes. Indicates that it contains.

The light emitting layer preferably contains a compound represented by the general formulas (1), (2), and (5), a phosphorescent light emitting material (3), and a host material. The host material may be a hole transporting host material or an electron transporting host material, but a hole transporting host material can be used.
In the present invention, the phosphorescent material and the compound represented by the general formula (1) in the light emitting layer, and one of the compounds represented by the general formula (4-1) or (4-2), It is preferable to contain.

  The host material is preferably a compound represented by the following general formula (4-1) or (4-2).

(In the general formulas (4-1) and (4-2), d and e each represent an integer of 0 to 3, and at least one is 1 or more. F represents an integer of 1 to 3. R ⁸ is the following. Represents a carbazole group represented by the general formula (5).)

(In General Formula (5), each R ₉ independently represents a substituent. G represents an integer of 0 to 8.)

R ₉ each independently represents a substituent, specifically a halogen atom, an alkoxy group, a cyano group, a nitro group, an alkyl group, an aryl group, or a heterocyclic group, preferably an alkyl group having 10 or less carbon atoms, a carbon group It is a substituted or unsubstituted aryl group of several tens or less.
g represents an integer of 0 to 8, and is preferably 0 to 4 from the viewpoint of not excessively shielding the carbazole skeleton responsible for electron transport. Further, from the viewpoint of ease of synthesis, when carbazole has a substituent, those having a substituent so as to be symmetrical left and right are preferable.
In the general formula (4-1), R ⁸ is preferably substituted with meta at the substitution position of the other benzene ring. In ortho substitution, since the steric hindrance of the adjacent substituent is large, the bond is easily cleaved and the durability is lowered. In addition, in para substitution, the molecular shape approaches a rigid rod shape and is easily crystallized, so that element degradation is likely to occur under high temperature conditions. In the general formula 4-2, when f is 2 or 3, it is preferable that R ⁸ is substituted with meta from the same viewpoint.

When the general formulas (4-1) and (4-2) have a hydrogen atom, an isotope (such as a deuterium atom) is also included. In this case, all hydrogen atoms in the compound may be replaced with isotopes, or a mixture in which a part is a compound containing isotopes may be used. R ⁹ in the general formula (5) is preferably substituted with deuterium, and the following structures are particularly preferable.

  Furthermore, the atom which comprises a substituent represents that the isotope is also included.

  The compounds represented by the general formulas (4-1) and (4-2) of the present invention preferably form a thin layer by a vacuum deposition process, but a wet process such as solution coating can also be suitably used. . The molecular weight of the compound is preferably 2000 or less, more preferably 1200 or less, and particularly preferably 800 or less from the viewpoints of deposition suitability and solubility. Also, from the viewpoint of vapor deposition suitability, if the molecular weight is too small, the vapor pressure becomes small, the change from the gas phase to the solid phase does not occur, and it is difficult to form an organic layer. Particularly preferred.

  Specific examples of the compounds represented by formulas (4-1) and (4-2) in the present invention are illustrated below, but the present invention is not limited to these.

[Organic electroluminescence device]
The device of the present invention will be described in detail.
The organic electroluminescent element of the present invention is an organic electroluminescent element having an organic layer including a light emitting layer between a pair of electrodes, and has a layer containing a compound represented by the general formula (1).

In the organic electroluminescent element of the present invention, the light-emitting layer and the layer containing the compound represented by the general formula (1) are organic layers, and may further have a plurality of organic layers.
In view of the properties of the light emitting element, at least one of the anode and the cathode is preferably transparent or translucent.

  Although it does not specifically limit as an organic layer, In addition to a light emitting layer, a positive hole injection layer, a positive hole transport layer, an electron injection layer, an electron transport layer, a positive hole block layer, an electron block layer, an exciton block layer, a protective layer, etc. You may have. Each of these layers may have other functions.

As an aspect of lamination of the organic layer in the present invention, an aspect in which a hole transport layer, a light emitting layer, and an electron transport layer are laminated in this order from the anode side is preferable. Further, a charge blocking layer or the like may be provided between the hole transport layer and the light-emitting layer, or between the light-emitting layer and the electron transport layer. A hole injection layer may be provided between the anode and the hole transport layer, and an electron injection layer may be provided between the cathode and the electron transport layer. Each layer may be divided into a plurality of secondary layers.
Each element constituting the element of the present invention will be described in detail.

(substrate)
The substrate used in the present invention is preferably a substrate that does not scatter or attenuate light emitted from the organic layer.
(anode)
The anode usually only needs to have a function as an electrode for supplying holes to the organic layer, and there is no particular limitation on the shape, structure, size, etc., depending on the use and purpose of the light-emitting element, It can select suitably from well-known electrode materials. As described above, the anode is usually provided as a transparent anode.
(cathode)
The cathode usually has a function as an electrode for injecting electrons into the organic layer, and there is no particular limitation on the shape, structure, size, etc., and it is known depending on the use and purpose of the light-emitting element. The electrode material can be selected as appropriate.
(Organic layer)
The organic EL device of the present invention has at least one organic layer including a light emitting layer, and as the organic layer other than the light emitting layer, as described above, a hole transport layer, an electron transport layer, a charge blocking layer. , Hole injection layer, electron injection layer and the like.
(Light emitting layer)
The light-emitting layer receives holes from the anode, the hole injection layer, or the hole transport layer when an electric field is applied, receives electrons from the cathode, the electron injection layer, or the electron transport layer, and recombines holes and electrons. It is a layer which has the function to provide and to emit light.

  The substrate, anode, cathode, organic layer, and light emitting layer are described in detail in, for example, Japanese Patent Application Laid-Open No. 2008-270736 and Japanese Patent Application Laid-Open No. 2007-266458, and the matters described in these documents can be applied to the present invention. .

As a light emitting layer, the thing using the compound represented by General formula (1) as a light emitting material and host material is preferable.
The light emitting layer may be a single layer or a multilayer of two or more layers. When there are a plurality of light emitting layers, the compound represented by the general formula (1) may be contained in two or more light emitting layers. In addition, each light emitting layer may emit light with different emission colors.

  The content of the light emitting material in the light emitting layer is preferably in the range of 0.1% by mass to 50% by mass and more preferably in the range of 0.2% by mass to 50% by mass with respect to the total mass of the light emitting layer. Preferably, the range of 0.3 mass% or more and 40 mass% or less is more preferable, and the range of 5 mass% or more and 30 mass% or less is most preferable.

When the light-emitting material used in combination with the compound of the present invention is a phosphorescent light-emitting material, the content thereof is preferably in the range of 0.1% by mass to 50% by mass with respect to the total mass of the light-emitting layer, and 1% by mass to 40% The range of mass% or less is more preferable, and the range of 5 mass% or more and 30 mass% or less is most preferable. In particular, in the range of 5% by mass or more and 30% by mass or less, the chromaticity of light emission of the organic electroluminescent element is less dependent on the addition concentration of the phosphorescent light emitting material.
In the organic electroluminescent element of the present invention, the compound (1) (the compound represented by the general formula (1)) is 5 to 30% by mass of at least one phosphorescent material with respect to the total mass of the light emitting layer. It is most preferable to contain.

(Host material)
The host material is a compound mainly responsible for charge injection and transport in the light-emitting layer, and is a compound that itself does not substantially emit light. In this specification, “substantially no light emission” means that the light emission amount from the substantially non-light emitting compound is preferably 5% or less, more preferably 3% or less of the total light emission amount of the entire device. More preferably, it means 1% or less.

In the present invention, the light emitting layer preferably contains a host material.
The concentration of the host material in the light emitting layer is not particularly limited, but is preferably the main component (the component having the largest content) in the light emitting layer, more preferably 50% by mass or more and 99.9% by mass or less, 50 mass% or more and 99.8 mass% or less are more preferable, 60 mass% or more and 99.7 mass% or less are especially preferable, and 70 mass% or more and 95 mass% or less are the most preferable. When two or more kinds of host materials are used in combination, it is preferable that more host molecules are close to other molecules in the film. Therefore, the weight ratio of the two host materials is preferably close to the same amount, preferably 20:80 to 50:50, more preferably 35:65 to 50:50, and most preferably 40:60 to 50:50.

  The glass transition point of the host material is preferably 60 ° C. or higher and 500 ° C. or lower, more preferably 70 ° C. or higher and 300 ° C. or lower, and still more preferably 90 ° C. or higher and 250 ° C. or lower.

  The fluorescence wavelength in the film state of the host material contained in the light emitting layer of the present invention is preferably in the range of 400 nm to 650 nm, more preferably in the range of 420 nm to 600 nm, and in the range of 440 nm to 550 nm. More preferably.

  Examples of the host material contained in the light emitting layer in the present invention include those having a carbazole skeleton, those having a diarylamine skeleton, those having an indole skeleton, those having a pyridine skeleton, those having a pyrazine skeleton, and triazines Those having a skeleton and those having an arylsilane skeleton, those having a thiophene skeleton, those having a furan skeleton, those having a pyrrole skeleton, those having a silole skeleton, a hole injection layer, a hole transport layer, an electron described later The material illustrated by the term of an injection | pouring layer and an electron carrying layer is mentioned, Preferably it is a material represented by General formula (1).

  Examples of host materials used in the present invention include compounds described in paragraphs [0113] to [0161] of JP-A No. 2002-1000047 and compounds described in paragraphs [0087] to [0098] of JP-A No. 2004-214179. However, it is not limited to these.

  Although the thickness of a light emitting layer is not specifically limited, Usually, it is preferable that they are 1 nm-500 nm, it is more preferable that they are 5 nm-200 nm, and it is still more preferable that they are 10 nm-100 nm.

(Hole injection layer, hole transport layer)
The hole injection layer and the hole transport layer are layers having a function of receiving holes from the anode or the anode side and transporting them to the cathode side. The hole injection material and the hole transport material used for these layers may be a low molecular compound or a high molecular compound.

(Electron injection layer, electron transport layer)
The electron injection layer and the electron transport layer are layers having a function of receiving electrons from the cathode or the cathode side and transporting them to the anode side. The electron injection material and the electron transport material used for these layers may be a low molecular compound or a high molecular compound.

  The hole injection layer, the hole transport layer, the electron injection layer, and the electron transport layer are described in detail in, for example, Japanese Patent Application Laid-Open No. 2008-270736 and Japanese Patent Application Laid-Open No. 2007-266458. Can be applied to.

-Hole blocking layer-
The hole blocking layer is a layer having a function of preventing holes transported from the anode side to the light emitting layer from passing through to the cathode side. In the present invention, a hole blocking layer can be provided as an organic layer adjacent to the light emitting layer on the cathode side.
Examples of organic compounds constituting the hole blocking layer include aluminum (III) bis (2-methyl-8-quinolinato) 4-phenylphenolate (Aluminum (III) bis [2-methyl-8-quinolinato] 4- aluminum complexes such as phenylphenolate (abbreviated as balq)), carbazole derivatives, triazole derivatives, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (2,9-Dimethyl-4,7-diphenyl-1) , 10-phenanthroline (abbreviated as BCP)) and the like.
The thickness of the hole blocking layer is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, and still more preferably 10 nm to 100 nm.
The hole blocking layer may have a single layer structure made of one or more of the materials described above, or may have a multilayer structure made of a plurality of layers having the same composition or different compositions.
-Electronic block layer-
The electron blocking layer is a layer having a function of preventing electrons transported from the cathode side to the light emitting layer from passing through to the anode side. In the present invention, an electron blocking layer can be provided as an organic layer adjacent to the light emitting layer on the anode side.
As an example of the organic compound constituting the electron blocking layer, for example, those mentioned as the hole transport material described above can be applied.
The thickness of the electron blocking layer is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, and even more preferably 10 nm to 100 nm.
The electron blocking layer may have a single layer structure composed of one or more of the above-described materials, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions.

(Protective layer)
In the present invention, the entire organic EL element may be protected by a protective layer.
As a material contained in the protective layer, any material may be used as long as it has a function of preventing materials that promote device deterioration such as moisture and oxygen from entering the device.

  The protective layer is described in detail, for example, in JP-A-2008-270736 and JP-A-2007-266458, and the matters described in these publications can be applied to the present invention.

<Sealing container>
The element of this invention may seal the whole element using a sealing container. You may enclose a water | moisture-content absorber or an inert liquid in the space between a sealing container and an element. Although it does not specifically limit as a moisture absorber, For example, barium oxide, sodium oxide, potassium oxide, calcium oxide, sodium sulfate, calcium sulfate, magnesium sulfate, phosphorus pentoxide, calcium chloride, magnesium chloride, copper chloride Cesium fluoride, niobium fluoride, calcium bromide, vanadium bromide, molecular sieve, zeolite, magnesium oxide and the like. The inert liquid is not particularly limited, and examples thereof include fluorinated solvents such as paraffins, liquid paraffins, perfluoroalkanes, perfluoroamines, perfluoroethers, chlorinated solvents, and silicone oils. It is done.

  The element of the present invention can obtain light emission by applying a direct current (which may include an alternating current component if necessary) voltage (usually 2 to 15 volts) or a direct current between the anode and the cathode. it can.

  Regarding the driving method of the element of the present invention, JP-A-2-148687, JP-A-6-301355, JP-A-5-29080, JP-A-7-134558, JP-A-8-234665, and JP-A-8-214447, The driving methods described in Japanese Patent No. 2784615, US Pat. Nos. 5,828,429 and 6023308, etc. can be applied.

  The element of the present invention can be suitably used for display elements, displays, backlights, electrophotography, illumination light sources, recording light sources, exposure light sources, reading light sources, signs, signboards, interiors, optical communications, and the like.

  EXAMPLES The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the scope of only the parts shown in the following examples.

[Synthesis Example 1] The following Exemplified Compound 1 was synthesized.

  Thiophene (25.0 g, 300 mmol, 2.0 eq) and acetone (11 mL, 150 mmol, 1.0 eq) were mixed and 75% aqueous sulfuric acid was added dropwise so that the internal temperature was 90 ° C. The reaction system was allowed to cool, neutralized by dropwise addition to a saturated aqueous potassium carbonate solution, and extracted with ethyl acetate. The organic phases were combined, dried and concentrated, and the resulting residue was purified with a column to obtain 7 g (22%) of Compound a as a viscous liquid.

  Compound a (3.0 g, 14 mmol, 1.0 equivalent) was dissolved in a mixed solvent of hexane (46 mL) and dimethoxyethane (23 mL), and cooled with ice. Normal butyl lithium (1.6 mol / L hexane solution, 35 mL, 57 mmol, 4.0 equivalents) was added dropwise, and then the mixture was stirred at room temperature for 2.5 hours. Thereafter, chlorotriphenylsilane (17.0 g, 57 mmol, 4.0 equivalents) was added, and the mixture was further stirred for 2 hours. A diluted hydrochloric acid aqueous solution was added to the reaction system, and extraction was performed with chloroform. The organic phases were combined, dried and concentrated, and ethyl acetate was added, and the resulting precipitate was filtered to obtain 6.8 g (67%) of Exemplary Compound 1 as a white solid.

¹ H-NMR (300 mhz, CDCl ₃ ) δ: 1.85 (s, 6H), 6.93 (d, J = 4.0 Hz, 2H), 7.11 (d, J = 4.0 Hz, 2H) , 7.33-7.46 (m, 18H), 7.55-7.58 (m, 12H).

[Synthesis Example 2] The following Exemplified Compound 2 was synthesized.

  Compound a (5.0 g, 24 mmol, 1.0 equivalent) and 1,1-diphenylethanol (9.5 g, 48 mmol, 2.0 equivalent) were dissolved in carbon disulfide (25 mL) and cooled with ice. Tin tetrachloride (12.5 g, 48 mmol, 2.0 equivalents) was added dropwise, followed by stirring for 2.5 hours at room temperature. A diluted hydrochloric acid aqueous solution was added to the reaction system, and extraction was performed with ethyl acetate. The organic phases were combined, dried and concentrated, and the resulting residue was purified with a column to obtain 6.3 g (46%) of Exemplary Compound 2 as a glassy solid.

¹ H-NMR (300 mhz, CDCl ₃ ) δ: 1.75 (s, 6H), 2.18 (s, 6H), 6.36 (d, J = 4.0 Hz, 2H), 6.62 (d , J = 4.0 Hz, 2H), 7.13-7.29 (m, 20H).

  Similarly, the following exemplary compounds 3 to 7 were synthesized. In addition, the following comparative compounds ref-1 to ref-3 and Pt-1, Pt-2, Ir-1, Ir-2, and Fl-1 were prepared.

〔Example〕
(Production of element)
A glass substrate having a 0.5 mm thickness and a 2.5 cm square ITO film (manufactured by Geomatek Co., Ltd., surface resistance 10 Ω / □) is placed in a cleaning container, subjected to ultrasonic cleaning in 2-propanol, and then subjected to UV-ozone treatment for 30 minutes. Went. The following organic layers were sequentially deposited on the transparent anode (ITO film) by vacuum deposition.
First layer: DNTPD: film thickness 160 nm
Second layer: NPD: film thickness 10 nm
Third layer: Compound 1 and Pt-1 (mass ratio 85:15): film thickness 60 nm
Fourth layer: BAlq: film thickness 10 nm
Fifth layer: BCP and 1% Li: film thickness 20 nm
On top of this, 1.0 nm of lithium fluoride and 100 nm of metallic aluminum were vapor-deposited in this order to form a cathode.
This is put in a glove box substituted with argon gas without being exposed to the atmosphere, and sealed with a stainless steel sealing can and an ultraviolet curable adhesive (XNR5516HV, manufactured by Nagase Ciba Co., Ltd.). And the element 1-1 of this invention was obtained.
In addition, as shown in Table 1 below, the light emitting layer material of the third layer was changed to fabricate the device of the present invention or the comparative device.
The brightness | luminance at the time of constant voltage (7.0V) application was investigated with respect to the obtained various elements. Thereafter, the device was placed in an oven PH-101 manufactured by Espec Corp. and allowed to stand at 102 ° C. for 24 hours. After the device taken out was allowed to cool, a voltage having the same intensity was applied again and the luminance was measured. In the following examples, various measurements were performed as follows.
(A) Luminance Luminance Using a source measure unit 2400 manufactured by Toyo Technica, a direct current voltage is applied to each element to emit light. The brightness was measured with a luminance meter BM-8 manufactured by Topcon Corporation. The luminescent color was confirmed visually. In the table, evaluation is made using the luminance before heating (relative value to the element 1-1 of the present invention) and the ratio (%) of the luminance obtained after heating to the luminance before heating.

  From the results of Table 1, it can be seen that the element of the present invention maintains substantially the same luminance even after driving after heating.

A device 2-1 of the present invention was prepared in the same manner except that the third layer was Compound 1, Pt-1, and H-1 (mass ratio 45:15:40), and evaluated in the same manner.
Moreover, the element 2-2 of this invention was produced similarly to the element 2-1, and evaluated.

  From the results in Table 2, it can be seen that the emission luminance before heating is improved by using together with H-1 or H-2.

  A device 3-1 of the present invention was produced in the same manner as in 1-1 except that the second layer was made of compound 1, and evaluated in the same manner.

  From the results in Table 3, it can be seen that when the compound of the present invention is used as the hole transport layer, the luminance before heating is improved and the luminance after heating is hardly lowered.

  The structure of the compound used in the above example is shown below.

Exemplary compounds

Comparative compound

Luminescent material

  Other compounds used in the examples

Claims (9)

An organic electroluminescence device having an organic layer including a light emitting layer between a pair of electrodes, wherein the compound represented by the following general formula (1) is contained in any one of the organic layers. Organic electroluminescent device.

(N represents an integer of 2 to 7.
Each R independently represents a substituent.
m and o each independently represents an integer of 0 to 2.
X represents each independently a sulfur atom, an oxygen atom, or NR ¹ .
Y ₁ each independently represents a substituent.
L _a represents a linking group selected from O, S, Sir ³¹ r ³² , NR ¹ or alkylene, or a combination thereof. Here, R ¹ represents any ^one of hydrogen, an alkyl group, an aryl group, and a heterocyclic group. r ³¹ and r ³² each independently represent a hydrogen atom, an alkyl group, an aryl group, a halogen atom, or a cyano group . ) Formula (1) in L _a is CR ²¹ R ²² or ^{Sir 31 r 32 (R 21,} R 22 each independently represent a hydrogen atom, an alkyl group, an aryl group, a halogen atom, a cyano group, or a heterocyclic group The organic electroluminescent device according to claim 1 , wherein r ³¹ and r ³² each independently represent a hydrogen atom, an alkyl group, an aryl group, a halogen atom, or a cyano group .   The organic electroluminescent element according to claim 1, wherein X in the general formula (1) is a sulfur atom. The organic electroluminescent element according to claim 3, wherein the compound represented by the general formula (1) is represented by the general formula (2).

(N represents an .Y ₂ and L _b .R ³ and R ⁴ are each independently a substituent represented each independently either a carbon atom or a silicon atom represents an integer of 2-7. However, the L _b When it is a silicon atom, R ⁴ is selected from the group consisting of a hydrogen atom, an alkyl group, an aryl group, a halogen atom and a cyano group.   The organic electroluminescent element according to any one of claims 1 to 4, wherein the light emitting layer contains both a phosphorescent light emitting material and a compound represented by the general formula (1).   6. The organic electroluminescent element according to claim 5, wherein the phosphorescent material is a platinum complex. The organic electroluminescence device according to claim 6, wherein the platinum complex is represented by the following general formula (3).

(L represents a divalent linking group.
X ¹ represents a sulfur atom, a phosphorus atom, an oxygen atom or a nitrogen atom.
X ² represents a carbon atom, a sulfur atom or a phosphorus atom.
R ⁵ , R ⁶ and R ⁷ each independently represents a substituent, and a, b and c each independently represent an integer of 0 to 3. ) The phosphor layer includes a phosphorescent material, a compound represented by the general formula (1), and a compound represented by the general formula (4-1) or (4-2). The organic electroluminescent element according to any one of claims 1 to 7.

(D and e represent an integer of 0 to 3, at least one is 1 or more. F represents an integer of 1 to 3. R ⁸ represents a carbazole group represented by the following general formula (5). )

(R ₉ each independently represents a substituent, and g represents an integer of 0 to 8.) A charge transporting compound represented by formula (2).

(N represents .R ^3, R ⁴ each independently represents a substituent represents either represents .Y ₂ and L _b are each independently a carbon atom or a silicon atom an integer of 2-7. However, the L _b When it is a silicon atom, R ⁴ is selected from the group consisting of a hydrogen atom, an alkyl group, an aryl group, a halogen atom and a cyano group.