JP7372652B2 - Acceptor material, method for producing π-conjugated boron compound, and electronic device - Google Patents

Description

The present invention relates to a novel π-conjugated boron compound, a method for producing the π-conjugated boron compound, and an electronic device, and in particular, a π-conjugated boron compound suitably used as an acceptor material, a method for producing the same, and the π-conjugated boron compound. This invention relates to electronic devices using boron compounds.

BACKGROUND ART In recent years, lightweight and flexible organic electronic materials that can be used in flexible electronic devices such as organic EL, organic thin film solar cells, and organic field effect transistors have been attracting attention.

In such electronic devices, organic donor materials that are electron rich and organic acceptor materials that are electron poor are used. More specifically, organic acceptor materials are used as charge transport materials for organic EL, n-type semiconductor materials for organic thin film solar cells, organic field effect transistors, and the like.

Fullerene compounds, which are stable in the atmosphere, are often used as organic acceptor materials. However, fullerene compounds are spherical and cannot increase interaction with substrates or planar molecules. Furthermore, fullerene compounds have low solubility in organic solvents, which poses a problem in manufacturing electronic devices using wet processes such as printing.

Therefore, as a planar organic acceptor material, for example, Patent Document 1 and Non-Patent Document 1 disclose a π-conjugated boron compound called planar borane, which is a planarized triarylborane containing boron with a large empty orbital that accepts electrons. is listed. Furthermore, Non-Patent Documents 2 and 3 describe π-conjugated boron compounds into which a dimesitylboryl group, which is one of boron-containing diarylboryl groups, is introduced.

International Publication No. 2017/164093

Z. Zhou, A. Wakamiya, T. Kushida, S. Yamaguchi, J. Am. Chem. Soc., 2012, 134 (10), 4529-4532. Z. Yuan, N. J. Taylor, R. Ramachandran, T. B. Marder, Applied Organometallic Chemistry, 1996, 10, 305-316. C. Foerster, W. Seichter, A. Schwarzer, E. Weber, Supramolecular Chemistry, 2010, 22 (10), 571-581.

The present inventors focused on acene-based molecules (acene and acene-substituted products) that have a planar shape and a π-electron system that is advantageous for intermolecular interactions, and considered imparting acceptor properties to these acene-based molecules. There is.

An object of the present invention is to provide a novel π-conjugated boron compound and an electronic device to which this π-conjugated boron compound is applied.

(1) The π-conjugated boron compound according to the present invention consists of acene or an acene derivative substituted with a diarylborylethynyl group.
(The acene derivative is such that some or all of the hydrogen atoms bonded to carbon atoms other than the carbon atoms substituted with the diarylborylethynyl group of the acene are substituted with a halogen atom, a cyano group, or an alkyl group. )

(2) In one aspect of the present invention, the π-conjugated boron compound is a π-conjugated boron compound represented by the following (Chemical formula 1), wherein Ar is the acene or the acene derivative , and R ¹ to R Each of ¹⁰ is a hydrogen atom, a halogen atom, a cyano group, an alkyl group, or an alkyl group in which some or all of the hydrogen atoms are substituted with halogen atoms.

(3) In one aspect of the present invention, R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ and R ¹⁰ are the alkyl group, or some or all of the hydrogen atoms are substituted with halogen atoms. It is an alkyl group.

(4) In another aspect of the present invention, R ² to R ⁴ and R ⁷ to R ⁹ are the alkyl groups described above, or the alkyl groups in which some or all of the hydrogen atoms are substituted with halogen atoms. be.

(5) In another aspect of the present invention, the π-conjugated boron compound is a π-conjugated boron compound represented by the following (Chemical formula 2), wherein Ar is the acene or the acene derivative , and R ¹ -R ²⁰ are each a hydrogen atom, a halogen atom, a cyano group, an alkyl group, or an alkyl group in which some or all of the hydrogen atoms are substituted with halogen atoms.

(6) In one aspect of the present invention, R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ , R ¹⁰ , R ¹¹ , R ¹³ , R ¹⁵ , R ¹⁶ , R ¹⁸ and R ²⁰ are the alkyl groups , or an alkyl group in which some or all of the hydrogen atoms are replaced with halogen atoms.

(7) In another aspect of the present invention, R ² to R ⁴ , R ⁷ to R ⁹ , R ¹² to R ¹⁴ and R ¹⁷ to R ¹⁹ are the alkyl groups, or some or all of the hydrogen It is an alkyl group in which an atom is substituted with a halogen atom.

(8) In another aspect of the present invention, the number of carbon atoms in the alkyl group and the number of carbon atoms in the alkyl group in which some or all of the hydrogen atoms are substituted with halogen atoms are 1 or more and 20 or less. .

(9) In another aspect of the present invention, the alkynyl group constituting the π-conjugated boron compound is a hydrogen atom on the carbon atom having the largest frontier orbital coefficient among the carbon atoms constituting the acene or acene derivative. has been replaced with

(10) The electronic device according to the present invention includes the π-conjugated boron compound according to any one of (1) to (9) as an acceptor material.

(11) One aspect of the present invention includes a first electrode, a second electrode, and a charge transport layer provided between the first electrode and the second electrode, the charge transport layer being , a layer in which a donor material and the acceptor material are mixed.

(12) The method for producing a π-conjugated boron compound according to the present invention is a method for producing a π-conjugated boron compound shown in (Chemical formula 1) below, in which Ar is acene or an acene derivative , and R ¹ to ^R10 is each a hydrogen atom, a halogen atom, a cyano group, an alkyl group, or an alkyl group in which some or all of the hydrogen atoms are substituted with a halogen atom, and is represented by the following (reaction formula 1). As shown, after the monoethynyl compound of acene is lithiated, diarylfluoroborane is reacted to produce a π-conjugated boron compound shown in (Chemical Formula 1) below.

(13) The method for producing a π-conjugated boron compound according to the present invention is a method for producing a π-conjugated boron compound shown in (Chemical formula 2) below, in which Ar is acene or an acene derivative , and R ¹ to R ²⁰ is each a hydrogen atom, a halogen atom, a cyano group, an alkyl group, or an alkyl group in which some or all of the hydrogen atoms are substituted with a halogen atom, and R ¹¹ to R ²⁰ are each It is the same substituent as R ¹ to R ¹⁰ , and after dilithioating the diethynyl compound of acene as shown in the following (reaction formula 2), diarylfluoroborane is reacted, and as shown in the following (chemical formula 2). Generates a π-conjugated boron compound.

According to the present invention, it is possible to provide a novel π-conjugated boron compound and an electronic device to which this π-conjugated boron compound is applied.

FIG. 1 is a cross-sectional perspective view schematically showing the configuration of an electronic device according to an embodiment. FIG. 3 is a cross-sectional view of a main part showing a manufacturing process of an electronic device according to an embodiment. This is a ¹ H-NMR spectrum of the first example. This is a ¹ H-NMR spectrum of Example 2. FIG. 2 is a schematic diagram showing the molecular structure of the first example. FIG. 2 is a schematic diagram showing the molecular structure of Example 2. FIG. 2 is a schematic diagram showing the molecular structures of a first comparative example and a second comparative example. FIG. 3 is a schematic diagram showing frontier trajectories of the first example and the second example. FIG. 2 is a schematic diagram showing the energy level of the lowest unoccupied orbital of molecules including the first example and the second example. 7 is a graph showing the energy level of the lowest unoccupied orbital according to the first to eighth examples.

(Considerations)
Before describing the embodiments, matters considered by the present inventors will be described.

As described above, the present inventors focused on acene-based molecules that have a planar shape and a π-electron system that is advantageous for intermolecular interactions, and investigated imparting acceptor properties to these acene-based molecules.

Acene (polyacene, oligoacene) is a general term for hydrocarbons having a structure in which a plurality of benzene rings are linearly condensed, and is represented by the following general formula (Formula 1).

C _4n+2 H _2n+4 (n is an integer of 2 or more)...(Formula 1)
Specific examples of acene include naphthalene (n=2), anthracene (n=3), tetracene (n=4), and pentacene (n=5).

Acene-based molecules have a large planar π-electron system that is advantageous for intermolecular interactions and molecule-substrate interactions, and a narrow Highest Occupied Molecular Orbital (HOMO) - lowest unoccupied orbital. (Lowest Unoccupied Molecular Orbital: LUMO) Because it has a gap, it is expected to be used as an organic semiconductor material. However, since acene molecules are electron-rich, they behave as donor compounds.

Therefore, the present inventors investigated the introduction of a boron-containing substituent into an acene-based molecule in order to impart acceptor properties to the acene-based molecule.

Boron, which is a Group 13 element, has three valence electrons, and three-coordinate boron compounds (boranes) that use these valence electrons for covalent bonds are electron-deficient compounds with an isoelectronic structure with carbocations. It has a large empty p orbital that accepts electrons on the boron atom. It is known that this empty p orbital strongly interacts (p-π ^* interaction) with the antibonding π orbital (π ^* ), which is the LUMO of the π-conjugated molecule. Therefore, by introducing borane as a substituent into a π-conjugated compound, the LUMO level of the parent skeleton of the π-conjugated compound can be stabilized, and acceptor properties due to electron-deficient boron can be imparted to the entire π-conjugated system. Conceivable.

Here, problems identified by the present inventors in introducing borane as a substituent into acene will be explained.

Generally, boranes are used as arylborane having a bulky aryl group (more specifically, diarylboryl group) because the boron center is susceptible to nucleophilic attack. Therefore, the present inventors focused on anthracene into which a dimesitylboryl group, which is one of the diarylboryl groups, is a π-conjugated boron compound described in the above-mentioned Non-Patent Documents 2 and 3. Hereinafter, a monosubstituted product of anthracene with a dimesitylboryl group will be referred to as B1 (chemical formula 11), and a disubstituted product of anthracene will be designated as B2 (chemical formula 12).

However, in the π-conjugated boron compounds related to B1 and B2, the acene-based molecule has a large π-plane and the diarylboryl group is bulky, so in order to avoid steric hindrance, these It was found that the coordination boron plane has a twisted structure with respect to each other, and specifically, that the dihedral angle φ between the acene ring and the tricoordination boron plane is 45° or more (see Figure 7 and Table 1 below). (see 1). That is, in the π-conjugated boron compounds related to B1 and B2, it is not possible to increase the p-π ^* interaction between the antibonding π orbital of acene and the p orbital of boron, and the LUMO is placed on the boron atom. It turned out that it was localized. Therefore, in the π-conjugated boron compounds related to B1 and B2, acceptor properties due to electron-deficient boron cannot be imparted to the entire π-conjugated system.

The π-conjugated boron compounds described in Patent Document 1 and Non-Patent Document 1 mentioned above are compounds represented by the following B3 (Chemical Formula 13), B4 (Chemical Formula 14), and B5 (Chemical Formula 15).

The π-conjugated boron compounds related to B3 to B5 are those in which a boron atom arylborane (triarylborane) is fixed in the plane with a σ bond, and it is true that the π plane of the aryl group and the 3-coordinate boron plane are on the same plane. However, with this method, it is not possible to introduce an arylborane as a substituent into acene, as in B1 and B2 described above.

From the above, when introducing arylborane into acene as a substituent, it is possible to suppress twisting between the acene ring and the three-coordinated boron plane and impart acceptor properties due to electron-deficient boron to the entire π-conjugated system. is desired.

(Embodiment)
Hereinafter, one embodiment of the present invention will be described in detail based on the drawings. Note that two embodiments of the present invention, a first embodiment and a second embodiment (hereinafter, these may be collectively referred to as the present embodiment), will be described.

<Characteristics and effects of the π-conjugated boron compound according to the first embodiment>
The π-conjugated boron compound according to the first embodiment consists of acene or an acene derivative (acene substituted product) substituted with a diarylborylethynyl group. More specifically, the π-conjugated boron compound according to the first embodiment is a π-conjugated boron compound having an acene substituent shown in (Chemical Formula 1) below.

In (Chemical Formula 1), Ar is aceneacene or an acene derivative , and R ¹ to R ¹⁰ are each a hydrogen atom, a halogen atom, a cyano group, an alkyl group, or some or all of the hydrogen atoms are substituted with a halogen atom. This is an alkyl group. Here, Ar ( acene or acene derivative ) referred to in (Chemical formula 1) has hydrogen atoms bonded to all of the carbon atoms constituting the acene, except for the carbon atoms to which the ethynyl group is bonded. (acene monosubstituted) as well as those in which some or all of the hydrogen atoms bonded to carbon atoms other than the carbon atom to which the ethynyl group is bonded are substituted with halogen atoms, cyano groups, or alkyl groups. Including those who are

In other words, the π-conjugated boron compound shown in (Chemical formula 1) is a completely new acene substituted compound in which a diarylboryl group is connected (linked, bonded) to acene via an ethynyl group (two carbon atoms having an sp-hybridized orbital). It is. In other words, it can be said to be a compound in which acene and diarylboryl groups are crosslinked with acetylene.

In this way, by connecting the acene and the diarylboryl group with a linear and rigid ethynyl group, the distance between the acene and the diarylboryl group is increased, steric hindrance is alleviated, and the acene ring and the 3-coordinated boron are connected. It is possible to suppress twisting with respect to the plane, specifically, to make the dihedral angle φ between the acene ring and the three-coordinated boron plane 30° or less. Furthermore, the empty p orbital of the boron atom of the diarylboryl group and the antibonding π orbital (π ^* ), which is the LUMO of the π-conjugated system extending from the ethynyl group to the acene, have mutual orbital symmetry, so Interorbital interaction becomes possible. Therefore, the π-conjugated system can be extended from the acene skeleton to the terminal boron atom via the ethynyl group. Further, as a result, the energy level of the LUMO of the π-conjugated boron compound shown in (Chemical formula 1) can be made deeper than the energy level of the LUMO of acene alone. That is, acceptor properties due to electron-deficient boron can be imparted to the entire π-conjugated system.

As a result, in the π-conjugated boron compound according to the first embodiment, acceptor properties can be imparted to acene or an acene derivative that is originally rich in electrons and used as a donor, and it can be used as an amphoteric semiconductor (p/n). It is expected that the function will be expressed.

In addition, in the π-conjugated boron compound according to the first embodiment, since the entire molecule is planar, the π-π interaction (π-π stacking) between molecules increases, resulting in a crystal structure (packing structure). It can be stabilized. As a result, when this π-conjugated boron compound is used as an acceptor molecule, an improvement in carrier mobility can be expected.

Further, in the π-conjugated boron compound according to the first embodiment, in a preferable form, R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ and R ¹⁰ are the alkyl group or the part Or it is an alkyl group in which all hydrogen atoms are substituted with halogen atoms. By doing so, the thermal stability of the diarylboryl group can be increased.

Further, in the π-conjugated boron compound according to the first embodiment, in a preferable form, R ² to R ⁴ and R ⁷ to R ⁹ are the alkyl group, or some or all of the hydrogen atoms are It is an alkyl group substituted with a halogen atom. By doing this, in the diarylboryl group decorated with a substituent, the orientation of the π-conjugated boron compound as a whole is increased without increasing the steric hindrance between the aryl group and acene and the steric hindrance between the aryl groups. Therefore, it can be expected to exhibit liquid crystal properties.

In the π-conjugated boron compound according to the first embodiment, the number of carbon atoms in the alkyl group and the number of carbon atoms in the alkyl group in which some or all of the hydrogen atoms are substituted with halogen atoms are preferably determined. The number of carbon atoms is 1 or more and 20 or less. By doing so, it is possible to achieve both thermal stability of the diarylboryl group and improvement in the orientation of the π-conjugated boron compound as a whole.

Furthermore, in the above description, the halogen atom substituted for the hydrogen atom of the diarylboryl group is preferably a fluorine atom. In this way, by substituting the hydrogen atom of the diarylboryl group with an electron-withdrawing substituent, the LUMO energy level of the π-conjugated boron compound shown in (Chemical Formula 1) can be further deepened.

Further, in the π-conjugated boron compound according to the first embodiment, as a preferable form, the ethynyl group constituting the π-conjugated boron compound has the highest frontier orbital coefficient among the carbon atoms constituting the acene. A hydrogen atom is substituted on a large carbon atom. Specifically, when acene is anthracene, it is preferable that the ethynyl group is substituted with the hydrogen atom on the carbon atom at the 9th or 10th position. When acene is tetracene, the ethynyl group is preferably substituted with a hydrogen atom on any one carbon atom at the 5th, 6th, 11th or 12th positions. When acene is pentacene, the ethynyl group is preferably substituted with a hydrogen atom on any one of the carbon atoms at the 5th, 6th, 7th, 12th, 13th, or 14th positions.

<Method for producing a π-conjugated boron compound according to the first embodiment>
Hereinafter, a method for manufacturing (synthesizing) a π-conjugated boron compound according to the first embodiment will be described.

The π-conjugated boron compound shown in the above (Chemical formula 1) can be synthesized by lithiation of an acene monoethynyl compound and then reacting with diarylfluoroborane, as shown in the following (Reaction formula 1). .

More specifically, when a monoethynyl compound of acene is lithiated, for example, ⁿ -butyllithium (hereinafter referred to as nBuLi) is dissolved in dehydrated tetrahydrofuran (hereinafter referred to as THF) at -95°C. An equivalent amount (more preferably 1.1 to 1.2 equivalents) is applied. Then, by adding 1 equivalent (more preferably 1.1 to 1.3 equivalents) of diarylfluoroborane to THF containing the lithiated acene monoethynyl compound and raising the temperature from -95°C to about room temperature, A π-conjugated boron compound shown in the above (Chemical formula 1) can be obtained.

The production method described above, in which a diarylboryl group is introduced into acene via an ethynyl group, has not been reported so far and is a new production method. According to this production method, a diarylborylethynyl group can be easily introduced into acene without going through any complicated steps.

<Characteristics and effects of the π-conjugated boron compound according to the second embodiment>
Similar to the first embodiment, the π-conjugated boron compound according to the second embodiment is composed of acene or an acene derivative substituted with a diarylborylethynyl group. More specifically, the π-conjugated boron compound according to the second embodiment is a π-conjugated boron compound shown in (Chemical Formula 2) below.

In (Chemical Formula 2), Ar is acene or an acene derivative , and R ¹ to R ²⁰ are each a hydrogen atom, a halogen atom, a cyano group, an alkyl group, or some or all of the hydrogen atoms are substituted with a halogen atom. This is an alkyl group. Here, Ar ( acene or acene derivative ) referred to in (Chemical formula 2) has hydrogen atoms bonded to all of the carbon atoms constituting the acene, except for the carbon atoms to which the ethynyl group is bonded. In addition to those in which some or all of the hydrogen atoms bonded to carbon atoms other than the carbon atom to which the ethynyl group is bonded are substituted with halogen atoms, cyano groups, or alkyl groups, Including those who are

In other words, the π-conjugated boron compound shown in (Chemical formula 2) is a completely new acene compound in which two diarylboryl groups are connected (linked, bonded) to acene via an ethynyl group (two carbon atoms having an sp-hybridized orbital). It is a substitute. In other words, it can be said to be a compound in which acene and two diarylboryl groups are crosslinked with acetylene.

In this way, by connecting acene and two diarylboryl groups with a linear and rigid ethynyl group, as in the first embodiment, the distance between acene and diarylboryl groups is increased to prevent steric hindrance. The dihedral angle φ between the acene ring and the tricoordinate boron plane can be reduced to 30° or less. In the second embodiment, the π-conjugated system can be extended from the acene skeleton to the two terminal boron atoms via the ethynyl group. Therefore, in the π-conjugated boron compound according to the second embodiment, acceptor properties due to electron-deficient boron can be imparted to the entire π-conjugated system, similarly to the first embodiment.

As a result, in the π-conjugated boron compound according to the second embodiment, acceptor properties can be imparted to the acene-based molecule, which is originally rich in electrons and used as a donor, and it can be used as an amphoteric semiconductor (p/n). Functional expression can also be expected.

In addition, in the π-conjugated boron compound according to the second embodiment, the entire molecule is planar, as in the first embodiment, so the π-π interaction (π-π stacking) between molecules becomes large. , the crystal structure (packing structure) can be stabilized. As a result, when this π-conjugated boron compound is used as an acceptor molecule, an improvement in carrier mobility can be expected.

In addition, in the second embodiment, the energy level of the LUMO of the π-conjugated boron compound shown in (Chemical formula 2) can be made deeper than the energy level of the LUMO of acene alone, and furthermore, the energy level of the LUMO of acene alone can be made deeper. It can be made deeper than the LUMO energy level of the π-conjugated boron compound shown in (Chemical formula 1) in one embodiment.

Further, in the π-conjugated boron compound according to the second embodiment, R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ , R ¹⁰ , R ¹¹ , R ¹³ , R ¹⁵ , R ¹⁶ , R ¹⁸ and R ²⁰ are the alkyl groups described above, or the alkyl groups in which some or all of the hydrogen atoms are substituted with halogen atoms. By doing so, the thermal stability of the diarylboryl group can be improved similarly to the first embodiment.

Further, in the π-conjugated boron compound according to the second embodiment, in a preferable form, R ² to R ⁴ , R ⁷ to R ⁹ , R ¹² to R ¹⁴ and R ¹⁷ to R ¹⁹ are the alkyl groups , or an alkyl group in which some or all of the hydrogen atoms are replaced with halogen atoms. By doing this, similarly to the first embodiment, in the diarylboryl group decorated with a substituent, the π-conjugated system is It is expected that the boron compound as a whole will improve its orientation and exhibit liquid crystal properties.

<Method for producing a π-conjugated boron compound according to the second embodiment>
Hereinafter, a method for producing (synthesizing) a π-conjugated boron compound according to the second embodiment will be described.

The π-conjugated boron compound of (Chemical Formula 2) above can be synthesized by dilithioating a diethynyl compound of acene and then reacting it with diarylfluoroborane, as shown in (Reaction Formula 2) below.

More specifically, when a diethynyl compound of acene is dilithiated, for example, 2 equivalents (more preferably 2.1 to 2.2 equivalents) of ⁿ BuLi are reacted in dehydrated THF at -95°C. Then, 2 equivalents (more preferably 2.1 to 2.3 equivalents) of diarylfluoroborane are added to THF containing the diethynyl compound of dilithiated acene, and the temperature is raised from -95°C to about room temperature. A π-conjugated boron compound shown in (Chemical formula 2) can be obtained.

The production method described above, in which two diarylboryl groups are introduced into acene via an ethynyl group, has not been reported so far and is a new production method. According to this production method, a diarylborylethynyl group can be easily introduced into acene without going through any complicated steps.

In addition, in the method for producing a π-conjugated boron compound according to the second embodiment, in the π-conjugated boron compound shown in the above (Chemical formula 2), R ¹¹ to R ²⁰ are the same as R ¹ to R ¹⁰ , respectively. The substituents were explained as examples. In this case, in place of the monoethynyl compound of acene in the method for producing a π-conjugated boron compound according to the first embodiment, a diethynyl compound of acene is prepared, and the equivalent amounts of the corresponding reagents are combined. A π-conjugated boron compound according to the second embodiment can be synthesized.

(Application example of π-conjugated boron compound)
An electronic device that is an application example of the π-conjugated boron compound according to this embodiment will be described below.

<Characteristics and effects of electronic devices>
FIG. 1 is a cross-sectional perspective view schematically showing the configuration of an electronic device according to this embodiment. The electronic device according to the present embodiment is an application example of the π-conjugated boron compound according to the first embodiment and the second embodiment described above. The electronic device according to this embodiment is also called an organic thin film solar cell because it uses an organic material as a donor (electron donor) material and an acceptor (electron acceptor) material and has a thin film active layer.

As shown in FIG. 1, the electronic device ED according to the present embodiment includes a first electrode EL1, a second electrode EL2, and an active layer (charged) disposed between the first electrode EL1 and the second electrode EL2. It has an AL (also referred to as a transport layer).

The active layer AL provided on the first electrode EL1 is a layer in which donor material DO and acceptor material AC are present in a mixed state. The active layer AL can be formed by forming a coating layer by coating a mixed solution of a donor material, an acceptor material, and a solvent, and then solidifying the coating layer by drying or the like.

Note that a buffer layer may be provided between the first electrode EL1 and the active layer AL. Further, a buffer layer may be provided between the active layer AL and the second electrode EL2. The first electrode EL1 and the second electrode EL2 are made of a conductive material (conductor), and at least one of the first electrode EL1 and the second electrode EL2 has optical transparency.

Further, the first electrode EL1 may be provided on a substrate (support). In this case, a transparent substrate can be used as the substrate. As the transparent substrate, a glass substrate, a plastic film (flexible substrate), etc. can be used. As the first electrode EL1, ITO (indium tin oxide), indium zinc oxide, or the like can be used. As the second electrode EL2, metals such as aluminum and silver, alloys containing these metals, and the like are used.

As the donor material DO according to this embodiment shown in FIG. 1, acene-based molecules, porphyrin complexes, oligothiophenes, etc. can be used. As the acceptor material AC according to the present embodiment shown in FIG. 1, the π-conjugated boron compound shown in (Chemical Formula 1) or (Chemical Formula 2) is used. In this way, by using the π-conjugated boron compound shown in (Chemical Formula 1) or (Chemical Formula 2) above as an acceptor material, it is possible to improve the characteristics of an electronic device.

Moreover, it is preferable to use an acene-based molecule as the donor material DO shown in FIG. In this way, when the acene-based molecule is used as the donor material DO and the π-conjugated boron compound according to the present embodiment is used as the acceptor material AC, the donor and acceptor materials are mixed in the charge transfer layer. The π-π interaction between the molecules constituting the material and the molecules constituting the acceptor material increases. As a result, the adhesion between the donor material and the acceptor material increases, and carrier mobility can be improved.

<Method for manufacturing electronic devices>
An example of a method for manufacturing an electronic device (organic thin film solar cell) will be described below. FIG. 2 is a cross-sectional view showing the manufacturing process of the electronic device according to this embodiment.

As shown in FIG. 2(a), a first electrode EL1 is formed on a light-transmissive substrate SUB. For example, ITO (indium tin oxide) is formed as a conductive layer on the substrate SUB and patterned to form the first electrode EL1.

Next, a buffer layer BUF1 is formed on the first electrode EL1. For example, a conductive polymer solution, PEDOT:PSS (poly(4-styrene sulfonic acid)-doped poly(3,4-ethylenedioxythiophene) aqueous solution, is applied onto a substrate and dried to form a buffer layer. Form BUF1.

Next, as shown in FIG. 2(b), an active layer AL is formed on the buffer layer BUF1. First, a solution for forming the active layer is prepared. The donor material and acceptor material are dissolved in a solvent, and additives are added if necessary. Additives are used, for example, to increase the solubility of donor and acceptor materials. This solution for forming the active layer is applied onto the buffer layer BUF1 and dried to form the active layer AL. After that, annealing treatment (heat treatment) is performed on the active layer AL, if necessary.

Next, as shown in FIG. 2(c), a buffer layer BUF2 is formed on the active layer AL. For example, a calcium layer is formed as the buffer layer BUF2 on the active layer AL using a vacuum evaporation method or the like.

Next, a second electrode EL2 is formed on the buffer layer BUF2. For example, an aluminum layer is formed on the buffer layer BUF2 as a conductor layer for the second electrode EL2 by using a vacuum evaporation method or the like.

As described above, acene molecules, porphyrin complexes, oligothiophenes, etc. can be used as the donor material DO. As the acceptor material AC according to the present embodiment shown in FIG. 1, the π-conjugated boron compound shown in (Chemical Formula 1) or (Chemical Formula 2) is used. The π-conjugated boron compound shown in (Chemical formula 1) or (Chemical formula 2) has a large π-π interaction between molecules and has good crystallinity, so annealing treatment can be omitted and it can be used in electronic devices. Manufacturing costs can be reduced.

(Example)
Hereinafter, this embodiment will be explained using the first to eighth examples (hereinafter referred to as Example 1 to Example 8) and the first to fifth comparative examples (hereinafter referred to as Comparative Examples 1 to 5). Although explained in more detail, this embodiment is not limited to the examples shown below.

<Configuration of Example 1>
Example 1 is 9-(dimesitylborylethynyl)anthracene (hereinafter referred to as AntB) shown in (Chemical Formula 3) below.

That is, in AntB of Example 1, Ar is anthracene in the π-conjugated boron compound shown in the above (chemical formula 1), and R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ and R ¹⁰ are all methyl. This is an example in which R ² , R ⁴ , R ⁷ and R ⁹ are all hydrogen atoms.

<Production method of Example 1>
The manufacturing method of Example 1 is as shown in (Reaction Formula 3) below.

Under an argon atmosphere, 153.7 mg (0.760 mmol) of 9-(ethynyl)anthracene was weighed out and dissolved in anhydrous THF (15 mL). 0.53 mL (0.836 mmol) of a 1.6 mol/L ⁿ BuLi hexane solution was added dropwise thereto at −95° C. and stirred for 30 minutes. 5 mL of a THF solution containing 224.2 mg (0.836 mmol) of dimesitylfluoroborane (hereinafter referred to as FBMes ₂ ) was added dropwise to the resulting suspension at -95°C, stirred for 30 minutes, and slowly warmed to room temperature. did. Thereafter, after stirring at room temperature for 15 hours, the blue-green fluorescent reaction solution was dried under reduced pressure, and the residue was dissolved in a dichloromethane-hexane mixed solvent (CH ₂ Cl ₂ :C ₆ H ₁₄ =1:1, 35 mL x 3 times). Extracted. The extract was dried under reduced pressure and washed with hexane (7 mL x 3) to obtain the target product AntB (176.5 mg, yield 39%) as a yellow solid. A single crystal of AntB could be easily obtained by leaving a hexane solution in the air and concentrating it.

It was verified by ¹ H-NMR spectrum that the product obtained by the above production method was AntB shown in (Chemical Formula 3) above. FIG. 3 is a ¹ H-NMR spectrum of Example 1. In the ¹ H-NMR spectrum, the vertical axis shows the relative intensity of the proton signal, and the horizontal axis shows the chemical shift (δ) value. As shown in FIG. 3, it can be confirmed that the above product is AntB shown in the above (chemical formula 3). As described above, in Example 1, AntB, which is a π-conjugated boron compound shown in the above (Chemical formula 3), was successfully synthesized.

<Configuration of Example 2>
Example 2 is 9,10-bis(dimesitylborylethynyl)anthracene (hereinafter referred to as AntB ₂ ) shown in (Chemical Formula 4) below.

That is, AntB ₂ of Example 2 is a π-conjugated boron compound shown in the above (chemical formula 2), in which Ar is anthracene, and R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ , R ¹¹ , R ¹³ , R ¹⁵ , R ¹⁶ and R ¹⁸ are all methyl groups, and R ² , R ⁴ , R ⁷ , R ⁹ , R ¹² , R ¹⁴ , R ¹⁷ and R ¹⁹ are all hydrogen atoms. Become.

<Production method of Example 2>
The manufacturing method of Example 2 is as shown in (Reaction Formula 4) below.

Under an argon atmosphere, 100.2 mg (0.422 mmol) of 9,10-bis(ethynyl)anthracene was weighed out and dissolved in anhydrous THF (30 mL). Thereto, 0.61 mL (0.972 mmol) of a 1.6 mol/L ⁿ BuLi hexane solution was added dropwise at −95° C., stirred for 20 minutes, and stirred for an additional 20 minutes after raising the temperature to 0° C. The resulting suspension was cooled to -95°C, 5 mL of a solution of 260.9 mg (0.972 mmol) of FBMes ₂ in diethyl ether (hereinafter referred to as Et ₂ O) was added dropwise, stirred for 20 minutes, and slowly warmed to room temperature. It was warm. Thereafter, after stirring at room temperature for 15 hours, the yellow-green fluorescent reaction solution was dried under reduced pressure, and the residue was dissolved in a dichloromethane-hexane mixed solvent (CH ₂ Cl ₂ :C ₆ H ₁₄ =1:1, 35 mL x 3 times). Extracted. The extract was dried under reduced pressure and washed with hexane (3 mL x 3) to obtain the target product AntB ₂ (122.6 mg, yield 38%) as an orange solid. A single crystal of AntB ₂ could be easily obtained by leaving a hexane solution in the air and concentrating it.

Furthermore, it was verified by ¹ H-NMR spectrum that the product obtained by the above production method was AntB ₂ shown in the above (chemical formula 4). FIG. 4 is a ¹ H-NMR spectrum of Example 2. As shown in FIG. 4, it can be confirmed that the product is AntB ₂ shown in (Chemical Formula 4) above. As described above, in Example 2, AntB ₂ , which is a π-conjugated boron compound shown in the above (Chemical formula 4), was successfully synthesized.

<Configuration of Example 3>
Example 3 is 1-(dimesitylborylethynyl)naphthalene (hereinafter referred to as NapB) shown in (Chemical Formula 5) below.

That is, NapB of Example 3 is a π-conjugated boron compound shown in (Chemical formula 1) above, in which Ar is naphthalene, and R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ and R ¹⁰ are all methyl. This is an example in which R ² , R ⁴ , R ⁷ and R ⁹ are all hydrogen atoms. The manufacturing method of Example 3 is the same as that of Example 1, so the explanation thereof will be omitted (hereinafter, the same applies to Example 5 and Example 7).

<Configuration of Example 4>
Example 4 is 1,4-bis(dimesitylborylethynyl)naphthalene (hereinafter referred to as NapB ₂ ) shown in (Chemical Formula 6) below.

That is, NapB ₂ of Example 4 is a π-conjugated boron compound shown in (Chemical formula 2) above, in which Ar is naphthalene, and R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ , R ¹¹ , R ¹³ , R ¹⁵ , R ¹⁶ and R ¹⁸ are all methyl groups, and R ² , R ⁴ , R ⁷ , R ⁹ , R ¹² , R ¹⁴ , R ¹⁷ and R ¹⁹ are all hydrogen atoms. Become. The manufacturing method of Example 4 is the same as that of Example 2, so the explanation thereof will be omitted (hereinafter, the same applies to Example 6 and Example 8).

<Configuration of Example 5>
Example 5 is 5-(dimesitylborylethynyl)tetracene (hereinafter referred to as TetB) shown in (Chemical Formula 7) below.

That is, in TetB of Example 5, in the π-conjugated boron compound shown in the above (Chemical formula 1), Ar is tetracene, and R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ and R ¹⁰ are all methyl. This is an example in which R ² , R ⁴ , R ⁷ and R ⁹ are all hydrogen atoms.

<Configuration of Example 6>
Example 6 is 5,12-bis(dimesitylborylethynyl)tetracene (hereinafter referred to as TetB ₂ ) shown in (Chemical Formula 8) below.

That is, TetB ₂ of Example 6 is a π-conjugated boron compound shown in (Chemical formula 2) above, in which Ar is tetracene, and R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ , R ¹¹ , R ¹³ , R ¹⁵ , R ¹⁶ and R ¹⁸ are all methyl groups, and R ² , R ⁴ , R ⁷ , R ⁹ , R ¹² , R ¹⁴ , R ¹⁷ and R ¹⁹ are all hydrogen atoms. Become.

<Configuration of Example 7>
Example 7 is 6-(dimesitylborylethynyl)pentacene (hereinafter referred to as PenB) shown in (Chemical Formula 9) below.

That is, in PenB of Example 7, in the π-conjugated boron compound shown in the above (Chemical formula 1), Ar is pentacene, and R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ and R ¹⁰ are all methyl. This is an example in which R ² , R ⁴ , R ⁷ and R ⁹ are all hydrogen atoms.

<Configuration of Example 8>
Example 8 is 6,13-bis(dimesitylborylethynyl)pentacene (hereinafter referred to as PenB ₂ ) shown in (Chemical Formula 10) below.

That is, PenB ₂ of Example 8 is a π-conjugated boron compound shown in the above (chemical formula 2), in which Ar is pentacene, and R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ , R ¹¹ , R ¹³ , R ¹⁵ , R ¹⁶ and R ¹⁸ are all methyl groups, and R ² , R ⁴ , R ⁷ , R ⁹ , R ¹² , R ¹⁴ , R ¹⁷ and R ¹⁹ are all hydrogen atoms. Become.

<Comparative example 1>
Comparative Example 1 is 9-(dimesitylboryl)anthracene (hereinafter referred to as B1) shown in (Chemical Formula 11) below.

Comparative Example 1 differs from Example 1 in that the dimesitylboryl group is directly bonded to anthracene without an ethynyl group.

<Comparative example 2>
Comparative Example 2 is 9,10-bis(dimesitylboryl)anthracene (hereinafter referred to as B2) shown in (Chemical Formula 12) below.

Comparative Example 2 differs from Example 2 in that the dimesitylboryl group is directly bonded to anthracene without an ethynyl group.

<Comparative example 3>
Comparative Example 3 is a planar fixed triphenylborane (hereinafter referred to as B3) in which the 2,6-positions of all three phenyl groups of triphenylborane shown in (Chemical Formula 13) are connected with a 1,1-dimethylmethylene group. ) (see Patent Document 1 and Non-Patent Document 1).

<Comparative example 4>
Comparative Example 4 is a planar fixed 9,10-diphenyl-9,10-dihydro-9,10-diboranthracene (hereinafter referred to as (referred to as B4) (see Patent Document 1 and Non-Patent Document 1).

<Comparative example 5>
Comparative Example 5 is a planar fixed triphenylborane (hereinafter referred to as B5) in which the 2,6-positions of all three phenyl groups of triphenylborane shown in (Chemical Formula 15) are connected with three oxygen atoms. (See Patent Document 1 and Non-Patent Document 1).

<Consideration of Examples and Comparative Examples>
[Molecular structure]
FIG. 5 is a schematic diagram showing the molecular structure of Example 1 determined by single crystal X-ray structural analysis, FIG. 6 is a schematic diagram showing the molecular structure of Example 2 determined by single crystal X-ray structural analysis, and FIG. is a schematic diagram showing the molecular structure of Comparative Example 1 and Comparative Example 2.

Table 1 also shows the single-crystal X-ray structural analysis shown _in FIGS. Based on the results, the values (rounded to the first decimal place) of the dihedral angle φ formed by the anthracene ring and the dimesitylboryl group were summarized.

As shown in Table 1, FIG. 5, and FIG. 6, AntB of Example 1 and AntB ₂ of Example 2 have a dihedral angle φ of 20° or less. On the other hand, as shown in Table 1 and FIGS. 7(a) and 7(b), B1 of Comparative Example 1 and B2 of Comparative Example 2 have dihedral angles φ of 45° or more.

As described above, according to Examples 1 and 2, by connecting anthracene and dimesitylboryl groups with a linear and rigid ethynyl group, the distance between the anthracene ring and dimesitylboryl group is increased to prevent steric hindrance. It was shown that it is possible to relax and suppress the twisting between the anthracene ring and the three-coordinated boron plane. The results suggest that the conjugated system is expanded from anthracene to the terminal boron atom via an acetylene bridge (ethynyl group). On the other hand, in Comparative Examples 1 and 2, it was shown that the anthracene ring and the three-coordinated boron plane had a twisted structure to avoid steric hindrance between the anthracene ring and the dimesitylboryl group. As a result, it is suggested that the 14π electron system of anthracene and the empty p orbital on the boron atom do not overlap spatially, and that the expansion effect of the conjugated system including the boron atom is small.

[Molecular orbital]
FIG. 8 is a schematic diagram showing the frontier orbits of Example 1 and Example 2. This frontier orbital distribution was calculated using the density functional method (calculation software: Gaussian 16, calculation level: B3LYP/6-31G(d), state : Vacuum).

As shown in FIG. 8, in both Example 1 (AntB) and Example 2 (AntB ₂ ), LUMO is delocalized from the anthracene ring to the terminal boron atom via an acetylene bridge (ethynyl group), It can be confirmed that the electron accepting property derived from the boron atom extends to the anthracene ring. In this way, the molecular orbital calculation results do not contradict the considerations explained in the above molecular structure section.

[Energy level]
FIG. 9 is a schematic diagram showing the energy level of the lowest unoccupied orbital for molecules including Example 1 and Example 2, and FIG. 10 is a schematic diagram showing the energy level of the lowest unoccupied orbital according to Examples 1 to 8. It is a graph. In FIG. 9, [60]PCBM is phenyl C61-butyric acid methyl ester ([6,6]-phenyl-C61-butyric acid methyl ester), and [70]PCBM is phenyl C71 butyric acid methyl ester ([6,6]-phenyl-C61-butyric acid methyl ester). ]-phenyl-C71-butyric acid methyl ester), and both are fullerene-based acceptor molecules.

Table 2 summarizes the measured values of HOMO and LUMO of Example 1 (AntB) and Example 2 (AntB ₂ ). For Examples 1 and 2, the oxidation potential and reduction potential in dichloromethane solution were measured by differential pulse voltammetry (DPV), and the HOMO/LUMO energy levels were calculated from the results (see Table 3 below). The same applies.). Table 2 also shows the measured values of HOMO and LUMO of anthracene (based on oxidation potential and ultraviolet-visible absorption spectrum) for comparison.

Table 3 also shows the calculated values of HOMO and LUMO of Examples 1 to 8, and the calculated values of HOMO and LUMO of Example 1 (AntB), Example 2 (AntB ₂ ), and Example 4 (NapB ₂ ). The actual measured values are summarized.

As shown in Table 2, it can be seen that the LUMOs of Example 1 (AntB) and Example 2 (AntB ₂ ) are deeper than that of anthracene, which is the comparison target. This result showed that the introduction of an alkynylborane skeleton to acene (that is, the introduction of a diarylboryl group via an ethynyl group) imparts acceptor properties to acene resulting from electron-deficient boron.

Further, as shown in Table 3 and FIG. 10, in Examples 1 to 8, it was shown that the energy level of LUMO becomes deeper as the acene ring becomes larger. This is because, as explained in the section on molecular orbitals above, the orbital distribution of LUMO spreads from the acene ring to the terminal boron atom, so as the acene ring becomes larger, the contribution of stabilization due to delocalization increases. It is thought that this is because

As a result, as shown in Table 2, Table 3, FIG. 9, and FIG. , Examples 5 to 8), the energy level of LUMO is deeper than that of planar borane in which electron-deficient boron is directly incorporated into the π-electron system (Comparative Examples 3 to 5). The results were comparable.

As described above, according to the present invention, it has been possible to provide a novel π-conjugated boron compound having acceptor properties in acene having a planar shape and a π-electron system that is advantageous for intermolecular interactions. This π-conjugated boron compound was shown to be useful as a non-fullerene acceptor molecule.

Although the invention made by the present inventors has been specifically explained based on the embodiments above, the present invention is not limited to the above embodiments, and can be modified in various ways without departing from the gist thereof. Needless to say.

AC Acceptor material AL Active layer (charge transport layer)
BUF1 Buffer layer BUF2 Buffer layer DO Donor material ED Electronic device EL1 First electrode EL2 Second electrode SUB Substrate

Claims (11)

An acceptor material containing a π-conjugated boron compound consisting of acene or an acene derivative substituted with a diarylborylethynyl group.
(The acene derivative is such that some or all of the hydrogen atoms bonded to carbon atoms other than the carbon atoms substituted with the diarylborylethynyl group of the acene are substituted with a halogen atom, a cyano group, or an alkyl group. ) In the π-conjugated boron compound according to claim 1,
The π-conjugated boron compound is a π-conjugated boron compound represented by the following (Chemical formula 1),
Ar is the acene or acene derivative ,
R ¹ to R ¹⁰ are each a hydrogen atom, a halogen atom, a cyano group, an alkyl group, or an alkyl group in which some or all of the hydrogen atoms are substituted with halogen atoms, a π-conjugated boron compound acceptor material containing.

In the π-conjugated boron compound according to claim 2,
R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ and R ¹⁰ are the above-mentioned alkyl groups, or the above-mentioned alkyl groups in which some or all of the hydrogen atoms are substituted with halogen atoms, π-conjugated boron Acceptor material containing compounds. In the π-conjugated boron compound according to claim 2,
R ² to R ⁴ and R ⁷ to R ⁹ are the aforementioned alkyl groups, or the alkyl groups in which some or all of the hydrogen atoms have been substituted with halogen atoms, an acceptor material containing a π-conjugated boron compound. In the π-conjugated boron compound according to claim 1,
The π-conjugated boron compound is a π-conjugated boron compound represented by the following (chemical formula 2),
Ar is the acene or acene derivative ,
R ¹ to R ²⁰ are each a hydrogen atom, a halogen atom, a cyano group, an alkyl group, or an alkyl group in which some or all of the hydrogen atoms are substituted with halogen atoms, a π-conjugated boron compound acceptor material containing.

In the π-conjugated boron compound according to claim 5,
R ¹ , R ³ , R ⁵ , R ⁶ , R ⁸ , R ¹⁰ , R ¹¹ , R ¹³ , R ^{15 , R 16 ,} R ¹⁸ and R ²⁰ are the alkyl group, or some or all of the hydrogen An acceptor material containing a π-conjugated boron compound, which is an alkyl group whose atom is substituted with a halogen atom. In the π-conjugated boron compound according to claim 5,
R ² to R ⁴ , R ⁷ to R ⁹ , R ¹² to R ¹⁴ and R ¹⁷ to R ¹⁹ are the alkyl groups described above, or the alkyl groups in which some or all of the hydrogen atoms have been replaced with halogen atoms; An acceptor material containing a π-conjugated boron compound. In the π-conjugated boron compound according to claim 2 or 5,
An acceptor material containing a π-conjugated boron compound, wherein the number of carbon atoms in the alkyl group and the number of carbon atoms in the alkyl group in which some or all of the hydrogen atoms are substituted with halogen atoms are 1 or more and 20 or less. In the π-conjugated boron compound according to any one of claims 1 to 8,
The acceptor material includes a π-conjugated boron compound, in which the diarylborylethynyl group is substituted with a hydrogen atom on a carbon atom having the largest frontier orbital coefficient among the carbon atoms constituting acene or an acene derivative . An electronic device comprising an acceptor material comprising the π-conjugated boron compound according to claim 1. The electronic device according to claim 10,
comprising a first electrode, a charge transport layer provided above the first electrode, and a second electrode provided above the charge transport layer,
The electronic device, wherein the charge transport layer is a layer in which a donor material and the acceptor material are mixed.

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