Novel Graphene Nanoribbon and Method for Producing the Same

Abstract

For a graphene nanoribbon represented by general formula (1) (in the formula, R1 represents a C1-12 linear alkyl group. R3 and R4 are both hydrogen atoms or R3 and R4 together form a group represented by SiR2aR2b-; where, R2a and R2b are the same or different and represent a hydrogen atom, an optionally branched C1-4 alkyl group, or a phenyl group. n represents an integer of 1 or higher.), an easier and industrially superior GNR production method and a novel GNR obtained by the production method.

Description

Technical Field

[0001] The present invention relates to an improved manufacturing method of graphene nanoribbons and novel graphene nanoribbons obtained by the manufacturing method.

Background Art

[0002] Graphene nanoribbons (hereinafter sometimes referred to as "GNR") are substances expected to be applied to semiconductors, solar cells, transparent electrodes, high-speed transistors, organic EL elements, etc. As manufacturing methods of the GNR, there are roughly two types known: a top-down method and a bottom-up method. In particular, the latter is attractive in that a large amount of GNR can be synthesized by precisely controlling the edge structure and width.

[0003] The present inventors focused on the latter bottom-up method and intensively studied its manufacturing method. As a result, as a manufacturing method of GNR with a small number of steps and suppressed side reactions, a method of polymerizing a silole compound by using an alkyne compound having a specific structure as an initiator was found (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the method of Patent Document 1 requires further improvement in its industrial implementation, and a simpler manufacturing method of GNR is required.

[0006] For this reason, an object of the present invention is to provide a simpler and industrially advantageous manufacturing method of GNR and novel GNR obtained by the manufacturing method.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that according to the following method, GNR can be produced more simply and with industrial advantages, and a novel GNR described below can be provided. Specifically, the present invention includes the following inventions.

[0008] [1] General formula (1):

[0009]

Chemical formula

[0010] (In the formula, R 1 represents a linear alkyl group having 1 to 12 carbon atoms. R 3 and R 4 are both hydrogen atoms, or R 3 and R 4 together form a group represented by -SiR 2a R 2b -. However, R 2a and R 2b are the same or different and represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may have a branch, or a phenyl group. n represents an integer of 1 or more.) A graphene nanoribbon represented by

[0011] [2] General formula (1-1):

[0012]

Chemical formula

[0013] (In the formula, R 1 , R 2a and R 2b are the same as defined above. n a represents an integer of 1 or more.) , and / or general formula (1-2):

[0014]

Chemical formula

[0015] (wherein, R 1 is the same as described above. n b represents an integer of 1 or more.) The graphene nanoribbon according to [1], represented by

[0016] [3] A method for producing the graphene nanoribbon according to [1] or [2], comprising General formula (2):

[0017]

Chemical formula

[0018] (wherein, R 1 , R 2a and R 2b are the same as described above.) A production method in which 0.01 to 0.4 mol of a palladium compound, o-chloranil, and a silver compound are present with respect to 1 mol of the silole compound represented by

[0019] [4] General formula (2):

[0020]

Chemical formula

[0021] (wherein, R 1 represents a linear alkyl group having 1 to 12 carbon atoms. R 2a and R 2b represent an alkyl group having 1 to 4 carbon atoms or a phenyl group which may have a branch.) The graphene nanoribbon obtained by polymerizing 0.01 to 0.4 mol of a palladium compound, o-chloranil, and a silver compound with respect to 1 mol of the silole compound represented by

[0022] [5] General formula (3):

[0023] [Chemical formula]

[0024] (In the formula, n-Bu represents an n-butyl group. R 2a and R 2b are the same or different and each represents an alkyl group having 1 to 4 carbon atoms which may have a branch or a phenyl group.) A silole compound represented by [Advantages of the Invention]

[0025] According to the present invention, under the above-described specific conditions, the following general formula (4A), which has been considered essential for initiating a polymerization reaction until now:

[0026] [Chemical formula]

[0027] (In the formula, R 5a and R 5b are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, a (poly) ether group, an ester group, a boronic acid or its ester group, a monovalent aromatic hydrocarbon group or a monovalent heterocyclic group. k1 and k2 are the same or different and each represents an integer of 1 to 3. When k1 and k2 are integers of 2 or more, each R 3a and / or R 3b may be the same or different.) An alkyne compound represented by the following general formula (4B):

[0028] [Chemical formula]

[0029] (In the formula, R 6a , R 6b , R 6c , R 6d , R 6e and R 6fis the same as or different from, and represents a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, a (poly)ether group, an ester group, a boronic acid or its ester group, a monovalent aromatic hydrocarbon group, or a monovalent heterocyclic group. a1 and a2 are the same as or different from each other, and represent a carbon atom or a nitrogen atom.) It is possible to produce GNR without using a K-region-containing aromatic compound, dibenzocyclooctadiyne, benzothiophene, or benzofuran (hereinafter sometimes referred to as "initiator compound") represented by . Therefore, since it is not necessary to separately use an initiator compound, GNR can be produced more inexpensively and simply, and a novel GNR having no unit derived from the initiator compound, which could not be produced by conventional known production methods, i.e., GNR represented by the general formula (1), can be produced.

[0030] In addition, according to the conventional known production method, it was considered necessary to use a palladium compound in an amount equal to or more than the equivalent amount with respect to the silole compound, but according to the production method of GNR of the present invention, GNR can be produced with a catalytic amount (i.e., less than the equivalent amount with respect to the silole compound) of the palladium compound. At the same time, since the amount of the silver compound used can also be reduced, according to the production method of GNR of the present invention, GNR can be produced at a lower cost.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0032] In this specification, "comprise" is a concept that also includes "consist essentially of" and "consist of".

[0033] In this specification, when a range is expressed as "A to B", it means A or more and B or less unless otherwise specified.

[0034] (1) Method for producing GNR of the present invention The method for producing GNR of the present invention is to polymerize a silole compound having a specific structure represented by the general formula (2) in the presence of 0.01 to 0.4 mol of a palladium compound, o-chloranil, and a silver compound with respect to 1 mol of the silole compound described below:

[0035]

Chemical formula

[0036] (In the formula, R 1 represents a linear alkyl group having 1 to 12 carbon atoms. R 2a and R 2b are the same or different and each represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may have a branch, or a phenyl group.) It is characterized by polymerizing a silole compound having a specific structure represented by the formula.

[0037] (1-1) Silole compound The silole compound used in the present invention has a structure represented by the above general formula (2). In the above general formula (2), the substituent R 1 needs to be a linear alkyl group having 1 to 12 carbon atoms. When the substituent R 1 is a hydrogen atom or a branched alkyl group, the polymerization reaction hardly proceeds, and it is impossible to obtain a GNR having a relatively high molecular weight (specifically, a weight average molecular weight (Mw) in terms of polystyrene measured under the conditions described in the Examples section below, for example, 3000 or more). Among the linear alkyl groups having 1 to 12 carbon atoms, a linear alkyl group having 2 to 8 carbon atoms is preferable, and a linear alkyl group having 4 carbon atoms (n-butyl group) is particularly preferable. Also, the substituents R 2a and R 2bis a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may have a branch, or a phenyl group. Examples of the alkyl group which may have a branch include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, etc. From the viewpoint of the ease of production of the silole compound represented by the above general formula (2), R 2a and R 2b are preferably a methyl group, an ethyl group or a phenyl group, and R 2a and R 2b are preferably the same substituent. These silole compounds can be used alone or in combination of two or more.

[0038] The silole compound represented by the above general formula (2) can be produced according to a known method (for example, the method described in Patent Document 1). Specifically, like the method described in the Examples section to be described later, a compound in which R 1 is a halogen atom (chlorine atom, bromine atom, iodine atom, etc.) instead of a linear alkyl group having 1 to 12 carbon atoms (for example, compound S23 in Synthesis Example 5 of Patent Document 1) is used as a substrate, and in the presence of an iron compound, according to the method of Synthesis Example 6 of Patent Document 1, it can be produced by reacting with a Grignard reagent having a linear alkyl group having 1 to 12 carbon atoms.

[0039] (1-2) Palladium compound In the present invention, palladium compounds and the like known as catalysts for the synthesis of polymer compounds and the like can be used, and among them, divalent palladium compounds are preferred. Examples of the palladium compounds that can be used include Pd(OH)2, Pd(OCOCH3)2, Pd2(dba)3, Pd(OCOCF3)2, Pd(acac)2, PdCl2, PdBr2, PdI2, Pd(NO3)2, Pd(CH3CN)4(SbF6)2, etc. Here, acac means acetylacetonate, and dba means dibenzylideneacetone. In the present invention, from the viewpoint of making it difficult to disintegrate the silole skeleton of the substrate and being more likely to obtain a higher molecular weight GNR by using a weakly cationic palladium compound, Pd(OH)2, Pd(OCOCH3)2, Pd(OCOCF3)2, PdBr2, PdI2, Pd(CH3CN)4(SbF6)2 are preferred, Pd(OCOCH3)2, Pd(OCOCF3)2, PdBr2, PdI2, Pd(CH3CN)4(SbF6)2 are more preferred, and Pd(OCOCH3)2 is particularly preferred. These palladium compounds can be used alone or in combination of two or more.

[0040] The amount of the palladium compound used is 0.01 to 0.4 mol, preferably 0.05 to 0.3 mol, per 1 mol of the silole compound. When the amount of the palladium compound used is less than 0.01 mol or more than 0.4 mol, a relatively high molecular weight GNR cannot be obtained.

[0041] (1 - 3) o-chloranil In the present invention, the amount of o-chloranil used is not particularly limited, but from the viewpoint of being more likely to obtain a relatively high molecular weight GNR, for example, it is 0.5 to 5.0 mol, preferably 1.0 to 3.0 mol, more preferably 1.5 to 2.5 mol, per 1 mol of the silole compound. When o-chloranil is not used, the polymerization reaction hardly proceeds and the GNR of the present invention cannot be obtained.

[0042] (1 - 4) Silver compound The silver compound used in the present invention is not particularly limited, and examples include organic silver compounds such as silver acetate, silver pivalate (AgOPiv), silver trifluoromethanesulfonate (AgOTf), silver benzoate (AgOCOPh); inorganic silver compounds such as silver nitrate, silver fluoride, silver chloride, silver bromide, silver iodide, silver sulfate, silver oxide, silver sulfide, silver tetrafluoroborate (AgBF4), silver hexafluorophosphate (AgPF6), silver hexafluoroantimonate (AgSbF6), etc. In the present invention, from the viewpoint of easily obtaining GNRs with a higher molecular weight, inorganic silver compounds are preferred, silver tetrafluoroborate (AgBF4), silver hexafluorophosphate (AgPF6), silver hexafluoroantimonate (AgSbF6), etc. are more preferred, silver tetrafluoroborate (AgBF4), silver hexafluoroantimonate (AgSbF6), etc. are even more preferred, and silver hexafluoroantimonate (AgSbF6) is particularly preferred. These silver compounds can be used alone or in combination of two or more.

[0043] The usage amount of the silver compound is, for example, 0.1 to 3.0 moles per 1 mole of the palladium compound, and from the viewpoint of easily obtaining GNRs with a relatively high molecular weight, it is preferably 0.2 to 1.5 moles, more preferably 0.3 to 1.3 moles per 1 mole of the palladium compound.

[0044] (1-5) Others The present invention is preferably carried out in a solvent. Examples of usable solvents include aliphatic hydrocarbons such as pentane, hexane, heptane, cyclohexane; halogenated aliphatic hydrocarbons such as dichloromethane, dichloroethane (DCE), chloroform (CHCl3), carbon tetrachloride, trichloroethylene (TCE); halogenated aromatic hydrocarbons such as monochlorobenzene (PhCl), dichlorobenzene (PhCl2), bromobenzene (PhBr), 1,3,5-tribromobenzene (PhBr3), and the like. These solvents can be used alone or in combination of two or more. Among these solvents, halogenated aliphatic hydrocarbons and halogenated aromatic hydrocarbons are preferred, and monochlorobenzene (PhCl) and dichlorobenzene (PhCl2) are more preferred. In addition to the above components, additives can be appropriately used within a range that does not impair the effects of the present invention.

[0045] When using a solvent, the amount used is, for example, 2 to 20 parts by mass, preferably 5 to 15 parts by mass, based on 1 part by mass of the silyl compound.

[0046] The present invention is preferably carried out under anhydrous conditions and in an atmosphere of an inert gas (such as nitrogen gas, argon gas, etc.). The reaction temperature is, for example, 50 to 200 °C, preferably 80 to 150 °C, more preferably 90 to 130 °C.

[0047] After completion of the reaction, the GNR of the present invention can be taken out from the reaction solution by performing conventional methods such as concentration, crystallization, filtration, etc. Further, if necessary, purification may be carried out by removing metal components by silica gel column chromatography, separating or fractionating polymers by gel permeation chromatography (GPC), or the like.

[0048] (2) GNR of the present invention The GNR of the present invention has the following general formula (1):

[0049]

Chemical formula

[0050] (In the formula, R 1 represents a linear alkyl group having 1 to 12 carbon atoms. R 3 and R 4 are both hydrogen atoms, or R 3 and R 4 together form a group represented by -SiR 2a R 2b -. However, R 2a and R 2b are the same or different and represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may have a branch, or a phenyl group. n represents an integer of 1 or more.) has a structure represented by

[0051] The GNR of the present invention is produced by the method for producing the GNR of the present invention described above. By carrying out the production method, first, the general formula (1-1):

[0052]

Chemical formula

[0053] (In the formula, R 1 represents a linear alkyl group having 1 to 12 carbon atoms. R 2a and R 2b are the same or different and represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may have a branch, or a phenyl group. n a represents an integer of 1 or more.) a GNR (polymer) having a structure represented by is generated, and then, a desilylation reaction proceeds for part or all of the polymer, and the following general formula (1-2):

[0054]

Chemical formula

[0055] (In the formula, R 1 represents a linear alkyl group having 1 to 12 carbon atoms. n b represents an integer of 1 or more.) It is considered to form a GNR (polymer) having a structure represented by [the following formula]. Therefore, the GNR in the present invention can also be described as containing the GNR (polymer) represented by the above general formula (1-1) and / or (1-2).

[0056] In addition, the substituents R in the above general formulas (1), (1-1), and (1-2) 1 , R 2a and R 2b all correspond to the substituents R of the above-described silole compound 1 , R 2a and R 2b . Therefore, the types of substituents and preferred specific examples are the same. Further, according to the production method of the present invention described above, when a plurality of types of silole compounds are used in combination, GNRs having different substituents R 1 can also be produced. Further, according to the production method of the present invention, polymers other than the GNR (polymer) represented by the above general formulas (1), (1-1), and (1-2) can also be included in the GNR of the present invention.

[0057] According to the production method of the GNR of the present invention, it is possible to produce a GNR having a relatively high molecular weight. However, the number of repeating units of the GNR of the present invention (that is, the degree of polymerization n in the general formula (1), the degree of polymerization n a in the general formula (1-1), and the degree of polymerization n b in the general formula (1-2)) is not particularly limited and can be appropriately selected according to the required properties. For example, it can be 1 to 1000, preferably 3 to 500, and more preferably 5 to 100. The number of repeating units n, n a and n b can be calculated from the number average molecular weight (Mn) in terms of polystyrene by SEC measured under the conditions described in the Examples section described later.

[0058] The GNR of the present invention has a weight average molecular weight (Mw) in terms of polystyrene measured by SEC under the conditions described in the Examples section described later of, for example, 2000 or more, preferably 3000 to 50000, and more preferably 4000 to 20000.

[0059] The GNR of the present invention is a GNR having no unit derived from an initiator compound, which could not be produced by a conventionally known method. Therefore, since the GNR of the present invention has a more single structure, it is expected that its properties are improved or different properties are exhibited as compared with conventionally known GNRs.

[0060] The GNR of the present invention may be a condensed-ring type GNR (armchair type GNR described in conventionally known literature) by condensing rings by a conventionally known method (for example, oxidation reaction, Scholl reaction, etc.) if necessary. This method can be carried out, for example, in accordance with the method described in Patent Document 1.

Examples

[0061] The present invention will be specifically described below with reference to examples and the like, but the present invention is not limited thereto at all.

[0062] (1) NMR measurement 1 1H-NMR and 13 13C-NMR were recorded using tetramethylsilane as an internal standard and deuterated chloroform (CDCl3) as a solvent on a JEOL-ESC600 ( 1 1H 600 MHz, 13 13C 150 MHz) or a JEOL-ESC400 ( 1 1H 400 MHz, 13 13C 100 MHz) spectrometer. Each data was described as follows.

[0063] Chemical shift, multiplicity (s = singlet, d = doublet, dd = doublet of doublets, t = triplet, sext = sextet, m = multiplet), coupling constant (Hz), and integration.

[0064] (2) Measurement of the molecular weight (weight average molecular weight (Mw), number average molecular weight (Mn)) of GNR using size exclusion chromatography (SEC) Analysis was performed under the following conditions using the following apparatus. Apparatus: Acquity (Advanced Polymer Chromatography) Column: Waters ACQUITY APC XT 125 2.5μm 4.6×150mm ACQUITY APC XT 200 2.5μm 4.6×150mm Measurement temperature: 40 °C Solvent: Tetrahydrofuran Standard molecular weight: Based on standard polystyrene.

[0065] <Synthesis example of the silole compound represented by formula (3-1) in Example 1>

[0066] [Chemical formula] (In the formula, n-Bu represents an n-butyl group. Acac represents an acetylacetonate group. THF represents tetrahydrofuran.)

[0067] Under a nitrogen atmosphere, to a 20 mL round-bottom flask containing a magnetic stir bar, the compound represented by formula (5) (1.475 g, 5.0 mmol), tris(acetylacetonato)iron(III) (Fe(acac)3; 44.5 mg, 0.25 mmol), tetrahydrofuran (THF; 5.5 mL), and N-methyl-2-pyrrolidone (NMP; 3.4 mL) were added. The reaction mixture was cooled to 0 °C, and n-butylmagnesium bromide (1.0 M in THF, 7.5 mL, 7.5 mmol) was added at 0 °C. Then, the temperature was raised to room temperature, and the mixture was stirred at room temperature for 14 hours.

[0068] Thereafter, water was added to quench the reaction, ethyl acetate (15 mL) was added, and the organic matter was extracted. After repeating this extraction operation three times in total, the organic layers were combined and washed with saturated brine, and then Na2SO4 was added and the organic layer was dried by allowing it to stand overnight. After drying, Na2SO4 was removed by filtration, and the solvent was removed under reduced pressure to obtain a crude product. The obtained crude product was purified by chromatography on silica gel (eluent: hexane) to obtain (11,11-dimethyl-9-butyl-11H-benzo[b]naphtho[2,1-d]silole (the compound represented by formula (3-1)) as colorless crystals (535 mg, 34%). The 1 1H-NMR and 13 13C-NMR analysis results were as follows. Also, 1 1H-NMR and 13 13C-NMR spectra are shown in Figures 1 to 2. 1 1H-NMR (400 MHz, CDCl3) δ 7.95 (d, J = 8.7 Hz, 1H), 7.91 (d, J = 8.7 Hz, 1H), 7.87-7.82 (m, 2H), 7.80 (d, J = 7.8 Hz, 1H), 7.53-7.47 (m, 2H), 7.46-7.40 m, 1H), 7.28 (dd, J = 1.8, 7.8 Hz, 1H), 2.68 (t, J = 7.3 Hz, 2H), 1.71-1.62 (m, 2H), 1.42 (sext, J = 7.3 Hz, 2H), 0.97 (t, J = 7.3 Hz, 3H), 0.58 (s, 6H). 13 13C-NMR (100 MHz, CDCl3) δ 146.9, 145.7, 142.1, 139.2, 136.8, 136.5, 132.84, 132.81, 130.8, 130.3, 128.9, 128.3, 126.5, 125.2, 120.8, 119.7, 35.6, 33.8, 22.5, 14.0, -2.7 (2C).

[0069] <Production Examples of GNRs for Examples 2 to 6 and Comparative Examples 1 to 5>

[0070]

Chemical formula

[0071] <Production Example of GNR in which R in the GNR represented by the general formula (1) is 1 an n-butyl group> Under a nitrogen atmosphere, into a 20 mL Schlenk tube containing a magnetic stir bar, a monomer (a compound represented by the formula (3-1), that is, in the above general formula (2), R 1 is an n-butyl group, R 2a = R 2b = a methyl group compound) (500 mg, 1.58 mmol), AgSbF6 (108.6 mg, 0.316 mmol), Pd(OCOCH3)2 (70.9 mg, 0.316 mmol), o-chloranil (777 mg, 3.159 mmol) and 1,2-dichlorobenzene (3.5 mL) were added. Then, the temperature was raised to 120 °C and stirred at 120 °C for 40 hours to obtain a reaction mixture.

[0072] After cooling the obtained reaction mixture to room temperature, it was passed through a short pad column of silica gel and a metal scavenger (metal capturer) while washing with CH2Cl2. Then, the solvent was removed under reduced pressure, methanol was added and suspended, and then filtration and drying were performed to obtain GNR.

[0073] When the obtained GNR was analyzed by size exclusion chromatography (SEC), Mn = 4,118, Mw = 7,385, and Mw / Mn (PDI) = 1.79.

[0074] <Examples 3 to 5, Comparative Examples 1 to 4> The monomer is such that R in the above general formula (2) 1 = the substituents shown in Table 1 below, R 2a = R 2bThe procedure was the same as in Example 2 except that the compound was changed to a compound having a methyl group, and GNR was obtained. The analysis results of the obtained GNR by SEC are shown in Table 1 below.

[0075]

Table 1

[0076] <Example 6> The procedure was the same as in Example 2 except that the amount of Pd(OCOCH3)2 used was changed to 0.158 mmol (0.1 equivalent based on the monomer (the compound represented by formula (3-1))), and the amount of AgSbF6 used was changed to 0.158 mmol (0.1 equivalent based on the monomer (the compound represented by formula (3-1))), and GNR was obtained. The analysis results of the obtained GNR by SEC are shown in Table 2 below.

[0077] <Comparative Example 5> The procedure was the same as in Example 2 except that the amount of Pd(OCOCH3)2 used was changed to 0.79 mmol (0.5 equivalent based on the monomer (the compound represented by formula (3-1))), and the amount of AgSbF6 used was changed to 0.79 mmol (0.5 equivalent based on the monomer (the compound represented by formula (3-1))), and GNR was obtained. The analysis results of the obtained GNR by SEC are shown in Table 2 below.

[0078]

Table 2

Claims

1. General formula (1): 【Chemical 1】 (wherein R １ represents a linear alkyl group having 1 to 12 carbon atoms. R ３ and R ４ are both hydrogen atoms, or R ３ and R ４ together form a group represented by -SiR ２ａ R ２ｂ -. However, R ２ａ and R ２ｂ are the same or different and represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may have a branch, or a phenyl group. n represents an integer of 1 or more.) A graphene nanoribbon represented by

2. General formula (1-1): 【Chemical 2】 (wherein, R １ represents a linear alkyl group having 1 to 12 carbon atoms. R ２ａ and R ２ｂ are the same or different and each represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may have a branch, or a phenyl group. n ａ represents an integer of 1 or more.) and / or General formula (1-2): 【Chemical Formula 3】 (wherein, R １ represents a linear alkyl group having 1 to 12 carbon atoms. n ｂ represents an integer of 1 or more.) The graphene nanoribbon according to Claim 1, represented by

3. A method for producing the graphene nanoribbon according to Claim 1 or 2, comprising General formula (2): 【Chemical Formula 4】 (wherein, R １ , R ２ａ and R ２ｂ are the same as described above.) A production method in which a silyl compound represented by general formula (2) is polymerized in the presence of 0.01 to 0.4 mol of a palladium compound, o-chloranil, and a silver compound with respect to 1 mol of the silyl compound represented by general formula (2).

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