JP2012188551A - Light emissive compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emissive compound exhibiting excellent light emissive efficiency in a single-molecule light emitting device.SOLUTION: The light emissive compound includes: a light emitting portion 1a; and a transport portion transporting electrons and holes. The light emitting portion 1a has a benzazole structure of a specific structure. The transport portion 1b has an oligothiophene molecular chain having an oligothiophene structure as a repetitive unit. The oligothiophene structure is replaced by a covering group existing in a space along the oligothiophene molecular chain so as to cover the entire length in the molecular chain direction of the oligothiophene structure and suppressing interaction among the oligothiophene structures, and a saturated hydrocarbon group.

Description

  The present invention relates to a light-emitting compound that can be used in a light-emitting device used in, for example, a display device. Specifically, the luminescent compound according to the present invention is a molecular light-emitting device that emits light by combining electrons injected from one electrode and holes injected from the other electrode between electrodes connected using organic molecules. Thus, it can be used for a single-molecule light emitting device in which electrodes are substantially connected with one molecule.

  Conventionally, light emitting devices using organic molecules have been formed to have characteristics as an electron transport layer, a light emitting layer, and a hole transport layer, respectively, using conjugated organic molecules mainly composed of aromatic groups. There has been known a stacked molecular light emitting device in which each layer is stacked between an electron injection electrode and a hole injection electrode in a thickness of about several tens of nanometers in the order described above from the electron injection electrode side. Patent Document 1). Such a stacked molecular light emitting device can exhibit excellent features such as thinness, smoothness, and flexibility, and thus is expected to be put to practical use as a new high-performance display device that can replace liquid crystal display devices. Has been. However, the conventional stacked molecular light emitting device has various problems for practical use.

  Specifically, the problems with stacked molecular light-emitting devices are: (1) the contact resistance between the injection electrode and the molecule is large, the injection efficiency of electrons and holes is low, and (2) the conduction mechanism between the molecules is tunnel conduction. Alternatively, since it is hopping conduction, the conduction efficiency is very low, the injected carriers are recombined in the middle and cannot necessarily contribute to light emission, and (3) the molecules that have reached the light emission center are molecules that contribute to light emission. The probability of excitation is low and the luminous efficiency does not increase. (4) The light emitted from the excited molecule is absorbed or reflected halfway, and the probability that it does not come out of the device is high, and the overall luminous efficiency is low. Is mentioned. From these facts, the theoretical efficiency of the laminated device is said to be 5%, and the actual efficiency is considered to be considerably lower than this. This is significantly lower than existing light-emitting devices, considering that the efficiency of fluorescent lamps is about 25%, for example. As described above, the conventional stacked molecular light emitting device has various problems for practical use.

  Therefore, with the aim of solving the above problems all at once and improving the light emission efficiency, a single molecule light emitting device in which a single organic light emitting molecule is directly bonded to each other between an electron injection electrode and a hole injection electrode is provided. It has been proposed (Patent Document 1). In this Patent Document 1, the theory that the conventional problems shown in the above (1) to (4) can be solved by such a single molecule light emitting device is explained as follows.

  That is, regarding the problem (1), in the conventional stacked molecular light emitting device, a molecular layer (electron transport layer, light emitting layer, hole transport layer) is formed on the electrode in air or in a low vacuum. In this case, an oxide layer on the electrode surface, contamination from the surroundings, and the like are formed between the electrode and the molecular layer, which causes the resistance to increase. Since the electrode and the organic molecule are connected by a chemical bond, the contact resistance can be sufficiently lowered, and as a result, the injection efficiency of electrons and holes can be increased.

  Regarding the above problem (2), the reason why the conduction efficiency in the molecular layer is low in the conventional stacked molecular light emitting device is that each molecule is independent and is not chemically bonded to each other. According to the single-molecule light emitting device in which the single molecule is bonded with a single molecule, since the electric conduction efficiency in the single molecule is high, sufficient electric conduction efficiency can be secured.

  Regarding the problem (3), the probability that the carrier that has reached the emission center in the conventional stacked molecular light emitting device excites the molecule that contributes to the emission decreases mainly due to the interaction between the molecules. This is presumably because phonons are released from the molecules in the state and deactivated. It is generally well known that the probability of emitting phonons in a stacked molecular light emitting device is high. On the other hand, in the single molecule light emitting device, the process of returning the excited state in the molecule to the ground state is predicted to occur with a certain probability, and it is possible to take the maximum value physically and chemically. The carriers that have reached the light emission center can contribute almost 100% to light emission.

  Regarding the problem (4) above, in the conventional stacked molecular light emitting device, the light emitted from the excited molecule may be reabsorbed by the adjacent molecule, but the single molecule light emitting device emits light. Since the wavelength is considered to be longer than the absorption wavelength, it is expected that the decrease in luminous efficiency due to such absorption is reduced.

JP-A-11-265786

I.E.E.Transaction of Electron Devices (IEEE Trans. Electron Devices), vol. 44, No. 8, 1997

However, the organic light emitting molecules specifically disclosed in Patent Document 1 are all organic light emitting molecules used in conventional stacked molecular light emitting devices. Therefore, the organic light-emitting molecules described in Patent Document 1 cannot solve the following problems (i) to (iii) unique to single-molecule light-emitting devices caused by connecting the electrodes with a single molecule. It was.
(I) It has heat resistance enough to withstand energy generated by collision when electrons injected from one electrode and holes injected from the other electrode are combined.
(Ii) To prevent the electrons from jumping out of the molecule while the electrons are transported in the molecule.
(Iii) A structure in which aggregation or entanglement between molecules is suppressed and the molecule can be easily isolated into one molecule.

  Specifically, with regard to the problem (i) above, collision energy is also generated in the conventional stacked molecular light emitting device, but in the conventional stacked molecular light emitting device, there are many molecules in the light emitting layer between the electrodes. For example, even if one of them is affected by heat, the luminous efficiency is not so much affected. However, in a single molecule light-emitting device, there is only one molecule between the electrodes, and if this single molecule is affected by collision energy, it immediately leads to a decrease in luminous efficiency.

Regarding the above problem (ii), electrons can be ejected even in a conventional stacked molecular light emitting device, but in the case of a stacked molecular light emitting device, many electrons and holes are injected. Even if some of them disappeared by jumping out, the luminous efficiency was not affected so much. However, in a single molecule light emitting device, since one electron and one hole are injected, it is important to surely avoid disappearance due to collision energy or electron jumping.
The above problem (iii) is a property necessary for connecting one molecule between electrodes in the production of a single molecule light emitting device.
As described above, solving the above-mentioned problems (i) to (iii) is indispensable for realizing good luminous efficiency that can be practically used in a single-molecule light-emitting device.

  The present invention has been made paying attention to the above-described circumstances, and the object thereof is to use a luminescent compound capable of exhibiting good luminous efficiency in a single-molecule light-emitting device, a synthesis method thereof, and the same. It is to provide a single molecule light emitting device.

  The present inventors have intensively studied to solve the above problems. As a result, by providing in one molecule a light-emitting site that functions as a light-emitting layer, and a transfer site that functions as an electron transport layer and a hole transport layer, the light-emitting site has a specific benzazole structure. The heat-resistance is improved and the transfer site is composed of oligothiophene molecular chains, and the oligothiophene structure that is the structural unit is aligned with the oligothiophene molecular chain so as to cover the entire length of the oligothiophene structure in the molecular chain direction. By introducing a substituent (coating group) that exists in the space and suppresses the interaction between oligothiophene molecular chains, the above-mentioned coating group exists so as to cover the oligothiophene molecular chain that is the transfer site. As a result, the coating group prevents the electrons injected from the electrode from jumping out, and suppresses aggregation and entanglement between the molecules, so that one molecule can be easily separated. It found to be a possible way, which resulted in the completion of the present invention.

  That is, the luminescent compound of the present invention has a luminescent site and a transport site for transporting electrons and holes, the luminescent site has a benzazole structure represented by the following formula (1), and the transport site is: An oligothiophene molecular chain having an oligothiophene structure as a repeating unit, and the oligothiophene structure exists in a space along the oligothiophene molecular chain so as to cover substantially the entire length of the oligothiophene structure in the molecular chain direction. It is characterized by being substituted with a covering group that suppresses the interaction between chains and a saturated hydrocarbon group.

[In Formula (1), A ¹ and A ² are each independently

It is group represented by these. One of X and Y is a nitrogen atom, and the other is an oxygen atom, a sulfur atom or a —NR ¹ — group, wherein R ¹ is a hydrogen atom, a straight or branched chain having 1 to 12 carbon atoms An alkyl group, a benzyl group, a p-tert-butylphenyl group, a p-tert-butylbenzyl group, a phenyl group or a phenethyl group. However, X and Y belonging to one 5-membered ring may be replaced with each other. ]

In the present invention, the light emitting site is a part that emits light by combining electrons and holes, and is a part that functions as a light emitting layer in a conventional stacked molecular light emitting device.
The light emitting site has a benzazole structure represented by the formula (1). Such a benzazole structure has good heat resistance, so even if collision energy occurs when electrons and holes are combined at the light emitting site, the molecules are damaged and the luminous efficiency is reduced. Absent.

In the formula (1), it is preferable that at least one of A ¹ and A ² has a methylene group (—CH ₂ —). As a result, the transferred electrons can be trapped in the light emitting site, and the electrons and holes can be more reliably combined to increase the light emission efficiency.
In the above formula (1), a linear or branched alkyl group having 1 to 12 carbon atoms, which is an example of R ¹ of the —NR ¹ — group that can be X and Y, is a straight chain having 1 to 12 carbon atoms. It is a chain or branched monovalent hydrocarbon group, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a tert-butyl group, a pentyl group, a hexyl group, and a dodecyl group. A linear hydrocarbon group is preferable, and the number of carbon atoms is preferably 4 or more.

  In the present invention, the transfer site is a part that transports carriers (electrons and holes) injected from the electrode to the light emitting site, and functions as an electron transport layer and a hole transport layer in a conventional stacked molecular light emitting device. It is a part that fulfills. Therefore, the transfer site is disposed at both ends of the light emitting site. In the present invention, by combining a light-emitting site in one molecule with a transfer site having an electron transport function and a hole transport function, higher luminous efficiency is obtained compared to the case where only one light-emitting site is present in one molecule. It becomes possible. In the case where the transfer site is not provided, the light-emitting site is chemically bonded to the electrode, so that the molecular orbital of the luminescent compound (light-emitting site) is affected by the electrode, and the current as set may not be obtained. By providing a transfer site between the electrode and the light emitting site, the influence of such an electrode can be eliminated and the desired current can be obtained.

  The transfer site is composed of an oligothiophene molecular chain having an oligothiophene structure substituted with a specific coating group and a saturated hydrocarbon group as a repeating unit. That is, the oligothiophene molecular chain is a chain in which the covering group and the saturated hydrocarbon group are substituted on the main chain composed of thiophene. Thus, when the oligothiophene structure is substituted with a saturated hydrocarbon group, the solubility of the luminescent compound in the solvent can be increased. On the other hand, by being substituted with the coating group, there is a bulky coating group in the space around the main chain, so that the electrons transported in the main chain can be prevented from jumping out and saturated. Even if the hydrocarbon group is substituted, aggregation and entanglement of molecules due to interaction between molecular chains can be prevented, and one molecule can be easily isolated.

  In the present invention, the “coating group” is a substituent that exists in a space along the oligothiophene molecular chain so as to cover substantially the entire length of the oligothiophene structure in the molecular chain direction and suppresses the interaction between the oligothiophene molecular chains. . Specifically, the covering group only needs to have a three-dimensional bulkiness so as to cover the entire length of the oligothiophene structure in the molecular chain direction. For example, the covering group is a hydrocarbon group containing a nitrogen atom and a silicon atom. Examples include a group that replaces two hydrogen atoms of thiophene. Note that covering substantially the entire length of the oligothiophene structure in the molecular chain direction does not necessarily mean that one coating group has a size sufficient to cover the entire length of the oligothiophene structure in the molecular chain direction. When a plurality of coating groups are substituted on the same, even if one coating group does not cover the entire length of the oligothiophene structure in the molecular chain direction, the plurality of coating groups cover the entire length of the oligothiophene structure in the molecular chain direction. It only has to be able to get. The covering group is preferably a non-conjugated substituent in order to prevent electrons from jumping out.

  Examples of the saturated hydrocarbon group include aliphatic and alicyclic hydrocarbon groups. The carbon number is preferably 1 or more and 20 or less, more preferably 2 or more, further preferably 6 or more, more preferably 20 or less, and still more preferably 16 or less. For example, linear, branched or cyclic alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, tert-butyl group, pentyl group, hexyl group, cyclohexyl group and dodecyl group can be mentioned. A straight-chain hydrocarbon group is preferable, and preferred examples include a hexyl group and a dodecyl group.

  The number of thiophenes in the repeating unit (oligothiophene structure) of the oligothiophene molecular chain is preferably 2 or more and 10 or less, and more preferably 3 or more and 5 or less. In addition, the number of the covering group and the saturated hydrocarbon group that are substituted with the main chain in which thiophene is continuous may be one or plural. The covering group and the saturated hydrocarbon group are preferably substituted with separate thiophenes. For example, a saturated hydrocarbon group is substituted on one or both thiophenes of the thiophene on which the covering group is substituted. Are preferred.

  The number of repeating units (oligothiophene structure) in the oligothiophene molecular chain may be appropriately set so that the molecular length of the luminescent compound can be connected between the electrodes of the molecular light emitting device to be applied, Usually, it is 1-128, preferably 2 or more, more preferably 4 or more, further preferably 6 or more, preferably 100 or less, more preferably 50 or less, and still more preferably 20 or less.

  As a specific example of the oligothiophene structure, for example, a structure represented by the following formula (2) is preferably exemplified.

[In Formula (2), at least one of R ^{2 to} R ⁵ is a saturated hydrocarbon group having 1 to 20 carbon atoms, and the remainder is a hydrogen atom or a saturated hydrocarbon group having 1 to 20 carbon atoms. R ^{6 to} R ¹³ are each independently an alkyl group having 1 to 3 carbon atoms. n is an integer of 1 to 128. B ¹ and B ² are each independently

Wherein k is an integer of 2-12. ]

In the formula (2), the saturated hydrocarbon group having 1 to 20 carbon atoms, which is an example of R ^{2 to} R ⁵ , includes a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms. Examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a tert-butyl group, a pentyl group, a hexyl group, a cyclohexyl group, and a dodecyl group.
In the formula (2), two of R ^{2 to} R ⁵ are preferably saturated hydrocarbon groups, and the remaining two are preferably hydrogen atoms, and more preferably one of R ² and R ³ is saturated. A mode in which the hydrocarbon group, the other is a hydrogen atom, one of R ⁴ and R ⁵ is a saturated hydrocarbon group, and the other is a hydrogen atom is preferred.

In the oligothiophene structure represented by the formula (2), when the number of n is 2 or more, the repeating unit represented by the formula (2) is continuously bonded in the state described on the paper surface. In some cases (specifically, thiophene substituted with R ² and R ^{3 in the} n-th repeating unit binds to thiophene substituted with R ⁴ and R ⁵ in the (n−1) -th repeating unit). However, when some of the repeating units are bonded to another repeating unit in a state where the notation of the paper is reversed (specifically, thiophene substituted with R ² and R ³ in the nth repeating unit is (n -1) when R ² and R ³ in the first repeating unit are bound to a substituted thiophene).

In the formula (2), examples of the alkyl group having 1 to 3 carbon atoms as examples of R ^{6 to} R ¹³ include a methyl group, an ethyl group, and a propyl group, and among them, a methyl group is preferable. R ^{6 to} R ¹³ may be different from each other but are preferably the same.

In the formula (2), k which is a repeating unit of the group represented by B ¹ and B ² is preferably 10 or less, more preferably 5 or less, further preferably 3 or less, and most preferably 2.

  The single-molecule light-emitting device of the present invention is characterized in that the light-emitting compound of the present invention is a single molecule connecting a pair of electrodes having a nanogap.

  The method for synthesizing the luminescent compound of the present invention comprises a benzazole compound having halogen atoms at both ends represented by (a) in the following formula (4), and a trialkyltin at one end represented by (b) in the following formula (4). It includes a step of coupling reaction with an oligothiophene having a group.

[In Formula (4), R ¹⁴ and R ¹⁵ are each independently

Wherein Z is a halogen atom. One of X and Y is a nitrogen atom, and the other is an oxygen atom, a sulfur atom or a —NR ¹ — group, wherein R ¹ is a hydrogen atom, a straight or branched chain having 1 to 12 carbon atoms An alkyl group, a benzyl group, a p-tert-butylphenyl group, a p-tert-butylbenzyl group, a phenyl group, or a phenethyl group. However, X and Y belonging to one 5-membered ring may be replaced with each other. R ¹⁶ is a linear or branched alkyl group having 1 to 12 carbon atoms. At least one of R ^{2 to} R ⁵ is a saturated hydrocarbon group having 1 to 20 carbon atoms, and the remainder is a hydrogen atom or a saturated hydrocarbon group having 1 to 20 carbon atoms. R ^{6 to} R ¹³ are each independently an alkyl group having 1 to 3 carbon atoms. n is an integer of 1 to 128. B ¹ and B ² are each independently

Wherein k is an integer of 2-12. A ¹ and A ² are each independently

It is group represented by these. m and l are each independently an integer of 1 to 128. ]

In the formula (4), examples of the halogen atom represented by Z in the examples of R ¹⁴ and R ¹⁵ include Cl, Br, I and the like, and Br is preferable from the viewpoint of reactivity.
In the formula (4), the linear or branched alkyl group having 1 to 12 carbon atoms, which is an example of R ¹⁶ , is a linear or branched monovalent hydrocarbon group having 1 to 12 carbon atoms. Examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, and a dodecyl group. A tributyltin group (—SnBu ₃ ) in which R ¹⁶ is a butyl group is preferable from the viewpoints of reactivity and availability.
In addition, about R < ¹ > -R < ¹³ > in the said Formula (4), it is synonymous with the said Formula (1) or the said Formula (2).

  The transfer sites are provided at both ends of the light-emitting site, respectively. The transfer site at one end (electron injection electrode side) is for electron transport, and the transfer site at the other end (hole injection electrode side) is positive. Although it functions for hole transport, the structure of the oligothiophene molecular chain that constitutes the transfer site on the electron injection electrode side and the structure of the oligothiophene molecular chain that constitutes the transfer site on the hole injection electrode side may be different. It may be the same or the same. In order to efficiently combine the injected electrons and holes, it is preferable that both oligothiophene molecular chains have the same or similar structures.

It is preferable that the luminescent compound of the present invention includes connection sites for connecting to the electrodes at both ends of the transfer site. The connection site may be a group that can be chemically bonded to the constituent elements of the electrode, and may be set as appropriate according to the electrode. For example, —SCN group, —SH group, —SCOCH ₃ group, —SCCH ₂ CH ₃ A group selected from the group consisting of a group, -SCH ₂ CH ₂ CN group, -SCH ₂ CH ₂ Si (CH ₃ ) ₃ group, -SeOH group, -TeOH group, -COOH group, and -OH group. Is preferred. Particularly, for the gold electrode, -SCN group, -SH group, -SCOCH ₃ group, -SCCH ₂ CH ₃ group, -SCH ₂ CH ₂ CN group, -SCH ₂ CH ₂ Si (CH ₃ ) ₃ group are preferable. For gold and silver electrodes, -SeOH group and -TeOH group are preferable, and for silicon electrode, -COOH group and -OH group are preferable. The connection site on the electron injection electrode side and the connection site on the hole injection electrode side may be the same or different.

  Since the luminescent compound of the present invention has a specific benzazole structure as a light-emitting site, it has excellent heat resistance, and the oligothiophene structure, which is a repeating unit of the oligothiophene molecular chain serving as a transfer site, covers the molecular chain. Therefore, it is possible to prevent the electrons from jumping out during transfer and to easily isolate one molecule. This makes it possible to achieve good light emission efficiency in a single molecule light emitting device, and can make a great progress in the practical application of organic light emitting devices. Furthermore, if the luminous efficiency can be increased as in such a single molecule light emitting device, the electric field strength can be sufficiently lowered, so that an effect of becoming a practical organic light emitting device from the viewpoint of reliability can also be obtained.

FIG. 1 is a schematic view showing a main part (interelectrode part) of a single molecule light emitting device of the present invention.

  An example of a preferred structure of the luminescent compound of the present invention is as shown in the following formula (3).

[In the formula ^{(3), A 1, A} 2, X and Y are as defined in the formula ^{(1), R 2 ~R 5} , R 6 ~R 13, B 1 and B ² are the formula (2) It is synonymous with. m and l are each independently an integer of 1 to 128. Q ¹ and Q ² are each independently a hydrogen atom or —SCN group, —SH group, —SCOCH ₃ group, —SCCH ₂ CH ₃ group, —SCH ₂ CH ₂ CN group, —SCH ₂ CH ₂ Si ( CH ₃ ) ₃ groups, —SeOH groups, —TeOH groups, —COOH groups, and —OH groups, or an organic group provided with the one species. ]

In the formula (3), the organic group as an example of Q ¹ and Q ² is a conjugated group having a substituent selected from the above group. For example, when Q ¹ and Q ² are the organic group, a substituent selected from the above group (that is, —SCN group, —SH group, —SCOCH ₃ group, —SCCH ₂ CH ₃ group, —SCH ₂ CH _2). A CN group, —SCH ₂ CH ₂ Si (CH ₃ ) ₃ group, —SeOH group, —TeOH group, —COOH group, —OH group) serve as a connection site to form a chemical bond with the constituent atoms of the electrode. Therefore, the group interposed between the connection site and the transfer site must be a conjugated group capable of transporting carriers injected from the electrode, such as an aromatic ring or thiophene. Specific examples of the organic group as an example of Q ¹ and Q ² include a substituted thienyl group or a substituted phenyl group having at least a substituent selected from the above group. This substituted thienyl group or substituted phenyl group may have another substituent in addition to the substituent selected from the above group. In the above formula (3), when Q ¹ and Q ² are hydrogen atoms, a connection site is introduced into the luminescent compound and then used for connection with the electrode.

In the above formula (3), the oligothiophene structural unit having a repeat number of m and the oligothiophene structural unit having a repeat number of 1 are described with the same structure (symbol) for convenience. The structures of both units may be the same or different (in other words, R ^{2 to} R ⁵ in the oligothiophene structural unit having the number of repetitions m and the number having the number of repetitions 1). R ^{2 to} R ⁵ in the oligothiophene structural unit are not necessarily the same).

Hereinafter, a method for synthesizing the luminescent compound of the present invention when Q ¹ and Q ² in the formula (3) are hydrogen atoms (a method for synthesizing the luminescent compound of the present invention) will be described. In this synthesis method, as shown in the scheme shown in the formula (4), a benzazole compound having halogen atoms at both ends shown in the formula (4) (a) and the formula (4) (b). A step of coupling reaction with oligothiophene having a trialkyltin group at one end is essential.

  First, the benzazole compound used as a raw material in the coupling reaction is a compound in which halogen atoms are introduced into both ends of a benzazole structure that serves as a light-emitting site of a desired light-emitting compound. Benzazole compounds (A) to (I) to be used.

  The benzazole compound can be easily prepared by a conventional method. For example, a benzene derivative in which an amino group, a hydroxyl group, a thiol group or the like is substituted at the 1-position, 2-position, 4-position and 5-position of the benzene ring (for example, 1,2,4,5-tetraaminobenzene, 4,6- Carboxyl group-containing compounds having a halogen atom (for example, 4-bromobenzoic acid, 4-bromomethylbenzoic acid, 4-bromophenylacetic acid, etc.) with respect to diaminoresorcinol, 2,5-diamino-1,4-benzenedithiol, etc. ) May be reacted and condensed. According to this method, a benzazole compound having a desired structure can be synthesized by appropriately changing the combination of the benzene derivative and the carboxyl group-containing compound to be used. At this time, the use ratio of the benzene derivative and the carboxyl group-containing compound may theoretically be such that the carboxyl group-containing compound is 2 moles per mole of the benzene derivative. On the other hand, the carboxyl group-containing compound is preferably 1.5 mol or more and 2.8 mol or less, more preferably 1.8 mol or more and 2.5 mol or less, still more preferably 1.9 mol or more, 2.2 mol It is below the mole. This reaction is preferably performed in an inert gas atmosphere, and polyphosphoric acid, dehydrated N-methyl-2-pyrrolidone, dehydrated N, N-dimethylformamide, dehydrated dimethyl sulfoxide and the like can be used as the solvent. However, it is preferable to use polyphosphoric acid because a benzazole compound can be obtained with good yield. When polyphosphoric acid is used as the solvent, its concentration is preferably 110 to 120% by mass, more preferably 112 to 116% by mass in terms of orthophosphoric acid. If the polyphosphoric acid is less than 110% by mass, the yield tends to be low. If the polyphosphoric acid exceeds 120% by mass, the polyphosphoric acid may be viscous and difficult to operate. In the reaction, the temperature is preferably set in the range of usually 40 ° C. or higher and 200 ° C. or lower, more preferably 50 ° C. or higher and 150 ° C. or lower. Heating during the reaction can be performed in one step up to a predetermined temperature, but it is preferable to increase the temperature in two steps in order to obtain a benzazole compound with good yield.

  The oligothiophene used as a raw material in the coupling reaction is a compound in which a trialkyltin group is introduced at one end of an oligothiophene structure that serves as a transfer site for a desired luminescent compound and a hydrogen atom is introduced at the other end. Yes, specifically, for example, oligothiophenes (J) to (M) described later in the examples. These oligothiophenes are known compounds and can be appropriately synthesized according to the method described in, for example, “Synthetic Metals”, 2001, Vol. 119, p67-p68.

The coupling reaction between the benzazole compound and the oligothiophene can be performed by heating and refluxing in the presence of a catalyst in a solvent in an inert gas atmosphere. Examples of the catalyst include Pd (PPh ₃ ) ₂ Cl _2, Pd (PPh ₃ ) ₄ , Pd ₂ (dba) ₃ , (dba) ₂ Pd, PdCl ₂ , (C ₆ H ₅ CN) ₂ PdCl ₂ , Pd A lithium compound such as lithium chloride can be used in combination with a palladium catalyst such as (dppf) ₂ Cl ₂ , Pd (OAc) ₂ , Pd (C ₁₇ H ₁₄ O) _2, or CuCl, CsF, or the like can be used (here , “Ph” means phenyl, “dba” means dibenzylideneacetone, “dppf” means diphenylphosphinoferrocene, and “Ac” means acetyl). The amount of the catalyst used may be appropriately set. For example, it is preferably 0.01 mol% or more and 20 mol% or less, more preferably 0.02 mol% or more and 18 mol% or less, with respect to 1 mol of the benzazole compound. More preferably, it is 0.03 mol% or more and 16 mol% or less. If the amount of the catalyst used is less than 0.01 mol%, the yield of the target product may be reduced. On the other hand, even if it is used in excess of 20 mol%, no further catalytic effect is expected and the reaction cost is high. Tend to be disadvantageous. As the reaction solvent, chlorobenzene, toluene, tetrahydrofuran, N-methyl-2-pyrrolidone, N, N-dimethylformamide, dimethyl sulfoxide and the like can be used. What is necessary is just to set reaction temperature suitably, It is set as the temperature which can be heated and refluxed according to a solvent, or it is preferable to set it as the temperature of room temperature vicinity. Such a coupling reaction produces a luminescent compound in which oligothiophene molecular chains are bonded to both ends of the benzazole structure. The product after the coupling reaction may be extracted and extracted with an appropriate organic layer, and then separated and purified by column chromatography or the like.

  The method for synthesizing the luminescent compound of the present invention comprises a step of further extending the oligothiophene molecular chain of the product obtained by the above-described coupling reaction (the luminescent compound in which the oligothiophene molecular chain is bonded to both ends of the benzazole structure). May be included. In order to extend the oligothiophene molecular chain, after the first-stage coupling reaction described above, the obtained product is further added to a halogen compound (for example, if it is a bromine compound, N-bromosuccinimide, bromine, tetrabutyl). Ammonium tribromide, perbromic acid, etc.) are reacted to introduce a halogen atom at the end of the oligothiophene molecular chain, and this is then subjected to a predetermined reaction having a trialkyltin group at one end as in the first-stage coupling reaction. The second-stage coupling reaction may be performed by heating and refluxing in the presence of a catalyst in a solvent together with the oligothiophene. By repeating the coupling reaction in this manner, the oligothiophene molecular chain of the luminescent compound can be extended to an arbitrary length. The oligothiophene used in the coupling reaction at each stage may be the same. For example, if different oligothiophenes are used in the coupling reaction at each stage, the oligothiophene molecular chain is designed to have a desired structure and length. be able to.

The luminescent compound synthesized as described above (Q ¹ and Q ² in the above formula (3) are hydrogen atoms) is for connecting to the electrode at the alpha position of the thiophene ring at the end of the oligothiophene molecular chain. Connection site (for example, —SCN group, —SH group, —SCOCH ₃ group, —SCCH ₂ CH ₃ group, —SCH ₂ CH ₂ CN group, —SCH ₂ CH ₂ Si (CH ₃ ) ₃ group, —SeOH group, 1 type selected from the group consisting of -TeOH group, -COOH group, and -OH group) can be introduced. As a method for introducing the connecting site, a conventional method may be adopted as appropriate depending on the type of substituent to be introduced. For example, the —SCOCH ₃ group was described in “Chemistry Letters”, 2000, p570-p571. It can be easily introduced according to a known method. Further, for example, in the case of introducing a —SCH ₂ CH ₂ CN group, both ends of the luminescent compound (Q ¹ and Q ² in the formula (3) are hydrogen atoms) are lithiated with n-butyllithium or the like, Subsequently, both ends can be converted into tributyltin by reacting with Bu ₃ SnCl and the like, and then a —SCH ₂ CH ₂ CN group can be introduced by a coupling reaction of 4- (2-cyanoethylthio) bromobenzene. The reaction when lithiating both ends of the luminescent compound is preferably performed, for example, in a solvent such as tetrahydrofuran under an inert gas atmosphere, and, if necessary, before reacting with n-butyllithium or the like. The luminescent compound may be preliminarily reacted with a halogen compound (for example, N-bromosuccinimide, bromine, tetrabutylammonium tribromide, perbromic acid, etc.) to brominate both ends. 4- (2-Cyanoethylthio) bromobenzene is a known compound and can be synthesized, for example, according to a known method described in “Organic Letters”, 2001, Vol. 3, p271-p273.

Incidentally, those having a protecting group the connection site to the end (e.g., -SCN group, -SCOCH ₃ group, -SCCH ₂ CH _{3 group,} -SCH 2 _CH 2 CN _{group, -SCH 2 CH 2 Si (CH} 3) _{In the case of three} groups, for example, when the luminescent compound having the connection site introduced therein is used for connection to the electrode, for example, a strong base (preferably, a mixed solvent of lithium diisopropylamide and tetrahydrofuran, diazabicycloundecene , Diazabicyclononene, etc.) to remove the protecting group and convert it to thiolate or the like.

  The luminescent compound of the present invention can be applied to, for example, a conventional stacked molecular light emitting device, but the luminescent compound of the present invention has characteristics required for a single molecular light emitting device as described above. Therefore, it is desirable to use for a single molecule light emitting device as described below.

The single-molecule light-emitting device of the present invention is a device in which a pair of electrodes having a nanogap with a single molecule is connected between the light-emitting compound of the present invention.
FIG. 1 schematically shows the main part (interelectrode part) of a single molecule light emitting device. In FIG. 1, the luminescent compound 1 is connected to the electron injection side electrode 2 and the hole injection side electrode 3 through the connection part 1c. The connection portion 1c and the electrodes 2 and 3 are connected by chemical bonding.

The distance between the electron injection side electrode 2 and the hole injection side electrode 3 is preferably 5 nm to 100 nm, more preferably 7 nm to 60 nm, and still more preferably 9 nm to 30 nm.
The electron injection side electrode 2 and the hole injection side electrode 3 are made of, for example, gold, silver, silicon or the like, and may be the same or different. The thickness of each electrode 2, 3 is not particularly limited, but is usually about 0.1 nm to 100 nm, preferably about 1 nm to 20 nm.

  In order to fabricate the above single molecule light emitting device, for example, the light emitting compound of the present invention having a connecting site is added to a suitable solvent (for example, chlorobenzene, dichlorobenzene, toluene, benzene, tetrahydrofuran, etc.) at a predetermined concentration. After preparing a dissolved solution (electrode binding solution) and supplying the electrode binding solution between a pair of electrodes, the solvent may be removed. The means for supplying the electrode binding solution is not particularly limited as long as it is appropriately selected, for example, dropping the electrode binding solution between the pair of electrodes or immersing the pair of electrodes in the electrode binding solution for a certain period of time. The concentration of the electrode binding solution is 0.5 μmol / L or more and 100 mmol / L or less, preferably 1 μmol / L or more and 90 mmol / L or less, more preferably 5 μmol / L or more and 80 mmol / L or less. When the pair of electrodes is immersed in the electrode binding solution, the immersion time is about 0.1 to 48 hours, preferably about 0.2 to 36 hours, more preferably about 0.5 to 24 hours. The removal of the solvent is not particularly limited, but is preferably performed at room temperature under a nitrogen stream, for example. Moreover, a single molecule light emitting device can also be produced by vacuum-depositing the light emitting compound of the present invention having a connection site toward an electrode.

Preparation of benzazole compound (Production Example 1-Preparation of benzazole compound (A))
In an argon atmosphere, 4.0 g of 1,2,4,5-tetraaminobenzenetetrahydrochloride and 5.8 g of 4-bromobenzoic acid were added to 58.5 g of polyphosphoric acid (concentration 116 mass% in terms of orthophosphoric acid). In addition, after stirring at 60 ° C. for 30 minutes, the mixture was further stirred at 120 ° C. for 5 hours. The obtained reaction solution was poured into 5 L of water and re-precipitated, and the powder was taken out by suction filtration. The powder was thoroughly washed with water and then vacuum-dried to obtain a benzazole compound (A) shown in Table 1.

(Production Example 2-Preparation of benzazole compound (B))
To 58.5 g of polyphosphoric acid (concentration 116 mass% in terms of orthophosphoric acid), 4.0 g of 1,2,4,5-tetraaminobenzenetetrahydrochloride and 6.2 g of 4- (bromomethyl) benzoic acid under argon atmosphere And stirred at 60 ° C. for 30 minutes, and further stirred at 120 ° C. for 5 hours. The obtained reaction liquid was poured into 5 L of water and re-precipitated, and the powder was taken out from the suction filtration. This powder was thoroughly washed with water and then vacuum-dried to obtain a benzazole compound (B) shown in Table 1.

(Production Example 3-Preparation of benzazole compound (C))
300 g of N, N-dimethylformamide was added to 4.7 g of the benzazole compound (A) obtained in Production Example 1 under an argon atmosphere, and after stirring at room temperature for a while, 0.5 g of sodium hydride was added. Thereafter, a mixed solution of 3.7 g of 1-iodobutane and 30 mL of N, N-dimethylformamide was added dropwise and stirred at room temperature for 17 hours, and then poured into 5 L of water to cause reprecipitation to obtain a white solid. After adding methanol 100mL to this white solid 5.0g and heating and refluxing, it cooled to room temperature, the depositing solid was suction-filtered, and the benzazole compound (C) shown in Table 1 was obtained.

(Production Example 4-Preparation of benzazole compound (D))
300 g of N, N-dimethylformamide was added to 4.7 g of the benzazole compound (A) obtained in Production Example 1 under an argon atmosphere, and after stirring at room temperature for a while, 0.5 g of sodium hydride was added. Thereafter, a mixed solution of 5.9 g of 1-iodododecane and 30 mL of N, N-dimethylformamide was added dropwise and stirred at room temperature for 17 hours, and then poured into 5 L of water to cause reprecipitation to obtain a white solid. . After adding methanol 100mL to this white solid 5.0g and heating and refluxing, it cooled to room temperature, the depositing solid was suction-filtered, and the benzazole compound (D) shown in Table 1 was obtained.

(Production Example 5-Preparation of benzazole compound (E))
In an argon atmosphere, 4.0 g of 1,2,4,5-tetraaminobenzenetetrahydrochloride and 6.2 g of 4-bromophenylacetic acid were added to 58.5 g of polyphosphoric acid (concentration 116 mass% in terms of orthophosphoric acid). In addition, after stirring at 60 ° C. for 30 minutes, the mixture was further stirred at 120 ° C. for 5 hours. This reaction solution was poured into 5 L of water and re-precipitated, and the powder was taken out by suction filtration. The powder was thoroughly washed with water and then vacuum-dried. Next, to 5.0 g of this powder, 300 mL of N, N-dimethylformamide was added under an argon atmosphere, and after stirring at room temperature for a while, 0.5 g of sodium hydride was added. Thereafter, a mixed solution of 3.7 g of 1-iodobutane and 50 mL of N, N-dimethylformamide was added dropwise and stirred at room temperature for 17 hours, and then the mother liquor obtained by suction filtration was poured into 5 L of water and reprecipitated. To give a white solid. After adding methanol 100mL to this white solid 6.95g and heating and refluxing, it cooled to room temperature, the depositing solid was suction-filtered, and the benzazole compound (E) shown in Table 1 was obtained.

(Production Example 6-Preparation of benzazole compound (F))
To 58.5 g of polyphosphoric acid (concentration 116 mass% in terms of orthophosphoric acid), 3.0 g of 4,6-diaminoresorcinol dihydrochloride and 5.8 g of 4-bromobenzoic acid are added under an argon atmosphere, For 30 minutes, and further stirred at 120 ° C. for 5 hours. This reaction solution was poured into 5 L of water and re-precipitated, and the powder was taken out by suction filtration. The powder was thoroughly washed with water and then vacuum-dried to obtain a benzazole compound (F) shown in Table 1.

(Production Example 7-Preparation of benzazole compound (G))
To 58.5 g of polyphosphoric acid (concentration 116 mass% in terms of orthophosphoric acid), in an argon atmosphere, 3.0 g of 4,6-diaminoresorcinol dihydrochloride and 6.2 g of 4-bromophenylacetic acid were added, and 60 ° C. For 30 minutes, and further stirred at 120 ° C. for 5 hours. The obtained reaction liquid was poured into 5 L of water and re-precipitated, and the powder was taken out from the suction filtration. The powder was thoroughly washed with water and then vacuum-dried to obtain a benzazole compound (G) shown in Table 1.

(Production Example 8-Preparation of benzazole compound (H))
To 58.5 g of polyphosphoric acid (concentration 116 mass% in terms of orthophosphoric acid), 3.4 g of 2,5-diamino-1,4-benzenedithiol dihydrochloride and 5.8 g of 4-bromobenzoic acid under an argon atmosphere The mixture was stirred at 60 ° C. for 30 minutes, and further stirred at 120 ° C. for 5 hours. The obtained reaction liquid was poured into 5 L of water and re-precipitated, and the powder was taken out from the suction filtration. The powder was thoroughly washed with water and then vacuum-dried to obtain a benzazole compound (H) shown in Table 1.

(Production Example 9-Preparation of benzazole compound (I))
To 58.5 g of polyphosphoric acid (concentration 116 mass% in terms of orthophosphoric acid), 4.0 g of 1,2,4,5-tetraaminobenzene tetrahydrochloride and 5-bromo-2-pyridinecarboxylic acid 5 in an argon atmosphere 0.9 g was added and stirred at 60 ° C. for 30 minutes, and further stirred at 120 ° C. for 5 hours. The obtained reaction liquid was poured into 5 L of water and re-precipitated, and the powder was taken out from the suction filtration. The powder was thoroughly washed with water and then vacuum-dried. Next, to 5.0 g of the obtained powder, 300 mL of N, N-dimethylformamide was added under an argon atmosphere, and after stirring for a while at room temperature, 0.5 g of sodium hydride was added. Thereafter, a mixed solution of 5.9 g of 1-iodododecane and 50 mL of N, N-dimethylformamide was dropped, and the mixture was stirred at room temperature for 17 hours, then poured into 5 L of water and reprecipitated to obtain a white solid. . After adding methanol 100mL to this white solid 5.0g and heating and refluxing, it cooled to room temperature, the depositing solid was suction-filtered, and the benzazole compound (I) shown in Table 1 was obtained.

Preparation of Oligothiophene Oligothiophenes (J) to (M) shown in Table 2 were prepared according to the method described in “Synthetic Metals”, 2001, Vol. 119, p67-p68.

Example 1
Under an argon atmosphere, 23 mg of benzazole compound (A), 262 mg of oligothiophene (J), 3 mg of palladium catalyst (Pd (PPh ₃ ) ₂ Cl ₂ ) and 4 mg of lithium chloride as a catalyst were added to the flask, and then 3 mL of chlorobenzene And heated to reflux at 145 ° C. for 3 hours. Thereafter, diethyl ether and saturated brine were added to the reaction solution for liquid separation, the organic layer was separated, and the collected organic layer was dried over sodium sulfate. Then, the solvent was distilled off, and the residue was separated using column chromatography (silica gel: “NH-DM1020” manufactured by Fuji Silysia Chemical Ltd., eluent: toluene / ethyl acetate = 1/1 (v / v)). Purification gave an oil.
Next, 90 mg of the obtained oily substance and 11 mg of N-bromosuccinimide were placed in a 5 mL vial and dissolved by adding 1 mL of tetrahydrofuran, and then kept at −10 ° C. in air and stirred for 145 minutes. Thereafter, the solvent was distilled off, and diethyl ether and saturated brine were added to the residue for liquid separation, the organic layer was separated, and the collected organic layer was dried over sodium sulfate.

Next, 263 mg of oligothiophene (K), ₂ mg of palladium catalyst (Pd (PPh ₃ ) ₂ Cl ₂ ) and 9 mg of lithium chloride as catalyst were added to the dried organic layer, and then 10 mL of chlorobenzene. And heated to reflux at 135 ° C. for 5 hours. Thereafter, diethyl ether and saturated brine were added to the reaction solution for liquid separation, the organic layer was separated, and the collected organic layer was dried over sodium sulfate. Thereafter, the solvent was distilled off, and the residue was subjected to column chromatography (silica gel: “NH-DM1020” manufactured by Fuji Silysia Chemical Ltd., eluent: hexane / ethyl acetate = 19/1 (v / v) to hexane / ethyl acetate. = 4/1 (v / v) gradually increased in polarity), and the oily substance obtained was recycled using a GPC column (“JAIGEL-2H” manufactured by Nihon Analytical Industries). (Equipment: “LC-9201” manufactured by Nippon Analytical Industries, eluent: toluene) to obtain a luminescent compound (N) having the structure shown below.

(Example 2)
In Example 1, except that 25 mg of benzazole compound (B) was used in place of benzazole compound (A), operation was performed up to the point of recycling fractionation as in Example 1 (recycling fractionation using a GPC column was performed). No), and an oily substance (compound in which a hexamer of an oligothiophene molecular chain was bonded to both ends of the benzazole compound (B)) before being subjected to recycling fractionation using a GPC column was obtained.
100 mg of the obtained oily substance and 11 mg of N-bromosuccinimide were placed in a 5 mL vial and dissolved by adding 2 mL of tetrahydrofuran, and then kept at −10 ° C. in air and stirred for 145 minutes. Thereafter, the solvent was distilled off, and diethyl ether and saturated brine were added to the residue for liquid separation, the organic layer was separated, and the collected organic layer was dried over sodium sulfate.

Next, 263 mg of oligothiophene (K), ₂ mg of palladium catalyst (Pd (PPh ₃ ) ₂ Cl ₂ ) and 9 mg of lithium chloride as catalyst were added to the dried organic layer, and then 10 mL of chlorobenzene. And heated to reflux at 135 ° C. for 5 hours. Thereafter, diethyl ether and saturated brine were added to the reaction solution for liquid separation, the organic layer was separated, and the collected organic layer was dried over sodium sulfate. Thereafter, the solvent was distilled off, and the residue was subjected to column chromatography (silica gel: “NH-DM1020” manufactured by Fuji Silysia Chemical Ltd., eluent: hexane / ethyl acetate = 19/1 (v / v) to hexane / ethyl acetate. = 4/1 (v / v) gradually increased in polarity), and the oily substance obtained was recycled using a GPC column (“JAIGEL-2H” manufactured by Nihon Analytical Industries). (Equipment: “LC-9201” manufactured by Nippon Analytical Industries, eluent: toluene) to obtain a luminescent compound (O) having the structure shown below.

(Example 3)
In Example 1, 29 mg of benzazole compound (C) was used instead of benzazole compound (A), 313 mg of oligothiophene (L) was used instead of oligothiophene (J), and oligothiophene (K) was used instead of oligothiophene (K). M) A luminescent compound (P) having the structure shown below was obtained in the same manner as in Example 1 except that 318 mg was used.

Example 4
In Example 2, 40 mg of benzazole compound (D) was used instead of benzazole compound (B), 313 mg of oligothiophene (L) was used instead of oligothiophene (J), and oligothiophene (K) was used instead of oligothiophene (K). M) A luminescent compound (Q) having the structure shown below was obtained in the same manner as in Example 2 except that 318 mg (× 2 times) was used.

(Example 5)
In Example 3, a luminescent compound (R) having the structure shown below was obtained in the same manner as in Example 3, except that 30 mg of benzazole compound (E) was used instead of benzazole compound (C).

The ¹ H spectrum data of the luminescent compound (5) obtained in Example 5 was as follows.
¹ H-NMR (400 MHz, tetrahydrofuran-d8); −0.23 (s, 12H), −0.16 (s, 12H), −0.13 (s, 120H), 0.38 (s, 12H), 0.40 (s, 12H) , 0.44 (s, 12H), 0.45 (s, 120H), 0.60-076 (m, 96H), 0.83-0.89 (m, 78H), 1.27 (br s, 436H), 1.57-1.80 (m, 52H), 2.62−2.70 (m, 48H), 4.13 (br s, 4H), 4.46 (br s, 4H), 6.96 (d, J = 5.1 Hz, 2H), 7.10−7.15 (m, 21H), 7.25 (s, 2H), 7.35 (d, J = 5.1 Hz, 2H), 7.40 (d, J = 7.8 Hz, 4H), 7.57 (d, J = 7.8 Hz, 4H), 9.15 (s, 1H).
MALDI-TOFMS (DIT) m / z 11222.81 (M +)

(Example 6)
In Example 4, except that 30 mg (× 2 times) of benzazole compound (E) was used in place of benzazole compound (D), a luminescent compound (S )

(Example 7)
In Example 3, a luminescent compound (T) having the structure shown below was obtained in the same manner as in Example 3, except that 24 mg of benzazole compound (F) was used instead of benzazole compound (C).

(Example 8)
In Example 3, a luminescent compound (U) having the structure shown below was obtained in the same manner as in Example 3, except that 25 mg of benzazole compound (G) was used instead of benzazole compound (C).

Example 9
In Example 3, a luminescent compound (V) having the structure shown below was obtained in the same manner as in Example 3, except that 25 mg of benzazole compound (H) was used instead of benzazole compound (C).

(Example 10)
In Example 4, a luminescent compound (W) having the structure shown below was obtained in the same manner as in Example 4 except that 40 mg of benzazole compound (I) was used instead of benzazole compound (D).

(Examples 11 to 20)
Using the luminescent compounds (N) to (W) obtained in Examples 1 to 10, a pair of gold electrodes is connected to produce a single molecule light emitting device.
That is, first, the luminescent compound obtained in each example was brominated by reacting with N-bromosuccinimide in tetrahydrofuran under an inert gas atmosphere, and then reacted with n-butyllithium. , The alpha position of the thiophene ring at both ends (ends of oligothiophene molecular chain) of each luminescent compound is lithiated. Subsequently, Bu ₃ SnCl was added to tributyltin both ends, and then 4- (2-cyanoethylthio) bromobenzene was added to cause a coupling reaction. The SCH ₂ CH ₂ CN group is introduced. 4- (2-Cyanoethylthio) bromobenzene is prepared according to the method described in “Organic Letters”, 2001, Vol. 3, p271-p273.

  Next, diazabicycloundecene was added to each of the luminescent compounds into which the connection sites obtained above were introduced to deprotect both cyanoethyl groups to convert them into thiolates. An electrode binding solution is prepared by dissolving in a solvent (chlorobenzene) so as to have a concentration of L. After immersing a pair of gold electrodes whose distance between the electrodes is as shown in Table 3 in this electrode binding solution for a certain period of time, the solvent is removed at room temperature under a nitrogen stream to produce a single molecule light emitting device. .

DESCRIPTION OF SYMBOLS 1 Luminescent compound 1a Light emission site | part 1b Transfer site 1c Connection site | part 2 Electron injection side electrode 3 Hole injection side electrode

Claims (9)

Having a light emitting site and a transport site for transporting electrons and holes;
The light emitting site has a benzazole structure represented by the following formula (1):
The transfer site is composed of an oligothiophene molecular chain having an oligothiophene structure as a repeating unit, and the oligothiophene structure exists in a space along the oligothiophene molecular chain so as to cover the entire length of the oligothiophene structure in the molecular chain direction. And a luminescent compound substituted with a coating group that suppresses an interaction between oligothiophene molecular chains and a saturated hydrocarbon group.
[In Formula (1), A ¹ and A ² are each independently
It is group represented by these. One of X and Y is a nitrogen atom, and the other is an oxygen atom, a sulfur atom or a —NR ¹ — group, wherein R ¹ is a hydrogen atom, a straight or branched chain having 1 to 12 carbon atoms An alkyl group, a benzyl group, a p-tert-butylphenyl group, a p-tert-butylbenzyl group, a phenyl group or a phenethyl group. Here, X and Y belonging to one 5-membered ring may be interchanged. ]   The luminescent compound according to claim 1, wherein the coating group is a non-conjugated substituent. The luminescent compound according to claim 1 or 2, wherein the oligothiophene structure is a structure represented by the following formula (2).
[In Formula (2), at least one of R ^{2 to} R ⁵ is a saturated hydrocarbon group having 1 to 20 carbon atoms, and the remainder is a hydrogen atom or a saturated hydrocarbon group having 1 to 20 carbon atoms. R ^{6 to} R ¹³ are each independently an alkyl group having 1 to 3 carbon atoms. n is an integer of 1 to 128. B ¹ and B ² are each independently
Wherein k is an integer of 2-12. ] The luminescent compound according to any one of claims 1 to 3, wherein in the formula (1) showing the benzazole structure, at least one of A ¹ and A ² has a methylene group.   The luminescent compound according to any one of claims 1 to 4, further comprising connection sites for connecting to electrodes at both ends of the transfer site. The connecting site is -SCN group, -SH group, -SCOCH ₃ group, -SCCH ₂ CH ₃ group, -SCH ₂ CH ₂ CN group, -SCH ₂ CH ₂ Si (CH ₃ ) ₃ group, -SeOH group, The light-emitting compound according to claim 5, comprising one kind selected from the group consisting of —TeOH group, —COOH group, and —OH group. The luminescent compound according to any one of claims 1 to 6, which has a structure represented by the following formula (3).
[In the formula ^{(3), A 1, A} 2, X and Y are as defined in the formula ^{(1), R 2 ~R 5} , R 6 ~R 13, B 1 and B ² are the formula (2) It is synonymous with. m and l are each independently an integer of 1 to 128. Q ¹ and Q ² are each independently a hydrogen atom or —SCN group, —SH group, —SCOCH ₃ group, —SCCH ₂ CH ₃ group, —SCH ₂ CH ₂ CN group, —SCH ₂ CH ₂ Si ( CH ₃ ) ₃ groups, —SeOH groups, —TeOH groups, —COOH groups, and —OH groups, or an organic group provided with the one species. ]   A single-molecule light-emitting device, wherein the luminescent compound according to claim 1 is connected between a pair of electrodes having a single molecule and a nanogap. A benzazole compound having a halogen atom at both ends represented by (a) in the following formula (4) and an oligothiophene having a trialkyltin group at one end represented by (b) in the following formula (4) are subjected to a coupling reaction. A method for synthesizing a luminescent compound comprising a step.
[In Formula (4), R ¹⁴ and R ¹⁵ are each independently
Wherein Z is a halogen atom. One of X and Y is a nitrogen atom, and the other is an oxygen atom, a sulfur atom or a —NR ¹ — group, wherein R ¹ is a hydrogen atom, a straight or branched chain having 1 to 12 carbon atoms An alkyl group, a benzyl group, a p-tert-butylphenyl group, a p-tert-butylbenzyl group, a phenyl group, or a phenethyl group. Here, X and Y belonging to one 5-membered ring may be interchanged. R ¹⁶ is a linear or branched alkyl group having 1 to 12 carbon atoms. At least one of R ^{2 to} R ⁵ is a saturated hydrocarbon group having 1 to 20 carbon atoms, and the remainder is a hydrogen atom or a saturated hydrocarbon group having 1 to 20 carbon atoms. R ^{6 to} R ¹³ are each independently an alkyl group having 1 to 3 carbon atoms. n is an integer of 1 to 128. B ¹ and B ² are each independently
Wherein k is an integer of 2-12. A ¹ and A ² are each independently
It is group represented by these. m and l are each independently an integer of 1 to 128. ]