JP6960624B2 - Optical up-conversion material - Google Patents

Description

The present invention relates to an optical up-conversion material.

Conventionally, an optical up-conversion light emitter that converts long-wavelength light into short-wavelength light has been known. As an optical up-conversion illuminant, an inorganic optical up-conversion illuminant using a rare earth element or the like is known. The inorganic light up-conversion illuminant has been applied to an IR card or the like that converts infrared laser light into visible light, and has already been put into practical use.

On the other hand, the organic light up-conversion illuminant using an organic compound uses the strong and wide absorption spectrum of the organic compound to increase the light with a wider wavelength and lower incident power than the inorganic light up-conversion illuminant. It is known that conversion is possible. Examples of applications of the organic light up-conversion illuminant include an organic solar cell. In organic solar cells, it is ultraviolet light and blue light that generate free charge carriers from sunlight. Therefore, by using an organic light up-conversion light emitter for the organic solar cell, it is possible to convert long wavelength light such as green and red into short wavelength light such as blue light and improve the photoelectric conversion efficiency of the organic solar cell. Expected. As described above, in recent years, organic light up-conversion illuminants have been attracting attention (see, for example, Patent Document 1, Non-Patent Documents 1 and 2).

The organic light up-conversion illuminant is generally used together with a photosensitizer and is used as an organic light up-conversion material. Examples of the optical up-conversion mechanism in the currently known organic optical up-conversion materials include the following mechanisms. First, the photosensitizer molecule ( ¹ A) in the ground state absorbs light energy and transitions to the excited singlet state ( ¹ A ^{* ) (1} A + hν → ¹ A ^* ). Next, intersystem crossing occurs rapidly to the excited triplet state ( ³ A ^{* ) (1} A ^* → ³ A ^* ), and energy is transferred from the excited triplet state of the photosensitizer molecule to the illuminant molecule. Is done. This causes the photosensitizer molecule to lose energy and return to its ground state. On the other hand, the luminescent molecule ( ¹ E) in the ground state changes to an excited triplet ( ³ E ^* ) (triplet-triplet energy transfer: ³ A ^* + ¹ E → ¹ A + ³ E ^* ). .. When the concentration of the luminescent molecule changed to the excited triplet state increases, the interaction between the luminescent molecules changed to the excited triplet state becomes efficient, and one of the luminescent molecules changed to the excited triplet state occurs. Energy is transferred from the other illuminant molecule. At this time, one luminescent molecule that has changed to the excited triplet state returns to the ground state, and the other changes to the excited singlet state (triplet-triplet annihilation process: ³ E ^* + ³ E ^* → ¹ E +. ¹ E ^* ). ^{Then, up-converted luminescence (1} E ^* → ¹ E + hν _f ) is generated as fluorescence from the luminescent molecule changed to the excited singlet state. Such mechanisms are called "triplet-triplet up-conversion", "photochemical up-conversion" and the like.

Considering the above mechanism, in the organic optical up-conversion material, the energy of the excited triplet state of the illuminant needs to be about half the energy of the excited singlet state. Therefore, as the luminescent material, a molecule having an aromatic ring skeleton or the like is used. Further, as the photosensitizer, an organometallic complex or the like that generates an excited triplet state with high efficiency is used.

For example, anthracene, 9,10-diphenylanthracene and the like are known as light up-conversion light emitters in the blue light emitting region. However, the optical up-conversion yield (conversion yield from long-wavelength light to short-wavelength light) using these illuminants is as low as about 3 to 5%, and a novel organic having a higher optical up-conversion yield. Development of system optical up-conversion materials is required.

Further, most of the conventional organic optical up-conversion materials are liquids as described later, and from the viewpoint of practical use, the development of solid organic optical up-conversion materials is also required.

Special Table 2008-506798 International Publication 2014/136619

Ceroni, P., Energy up-conversion by low-power excitation: new applications of an old concept. Chemistry (Weinheim an der Bergstrasse, Germany) 2011, 17, 9560-4. Trupke, T .; Shalav, a .; Richards, BS; Wurfel, P .; Green, M., Efficiency enhancement of solar cells by luminescent up-conversion of sunlight. Solar Energy Materials and Solar Cells 2006, 90, 3327-3338 ..

In organic light up-conversion materials, due to the principle of operation, energy transfer between the sensitizer and the illuminant and pair annihilation between the triplet illuminants are performed between the sensitizer and the illuminant or the triplet illuminant. Molecular collisions between each other are required. For this reason, conventionally, a high-efficiency material having an emission quantum yield of more than 10% is a liquid or a gel-like medium containing substantially a liquid, and there is a difficulty in handling and deviceization.

Furthermore, for solids that do not contain liquid, it is known that the sensitizer and the luminescent material crystallize separately in the vapor deposition method and the spin coating method from a solution (for example, in the paper "Monguzzi, A. Tubino, R .; Hoseinkhani, S .; Campione, M .; Meinardi, F., Low power, non-coherent sensitized photon up-conversion: modeling and perspectives. Phys. Chem. Chem. Phys. 2012, 14, 4322 -4332 "), there was a problem in that the energy transfer between the two was significantly hindered.

Furthermore, since the transfer of energy between the sensitizer and the luminescent material and the triplet luminescent material are inhibited by oxygen in the atmosphere, it is necessary to seal the sensitizer and the luminescent material in an inert gas to remove oxygen. In these respects, the same applies to the prior art of the present inventors (Patent Document 2).

Under such circumstances, it is a main object of the present invention to provide a solid organic optical up-conversion material that realizes a high optical up-conversion yield.

In order to overcome the problem that the sensitizer and the illuminant crystallize separately when the solvent is evaporated from the solution to solidify, the present inventor emits light faster than the sensitizers crystallize with each other. I got the idea that by allowing the body to crystallize, the sensitizer can be taken into the illuminant crystal and solidified without crystallizing. Therefore, by lowering the concentration of the sensitizer with respect to the luminescent material, further increasing the concentration of the luminescent material, and adjusting the solvent and volatile conditions, the luminescent material can be rapidly crystallized, thereby solving the above-mentioned problems. We made a diligent study to solve the problem. As a result, by using the compound represented by the above general formula (1) as an optical up-conversion illuminant and making it a solid together with a photosensitizer, the optical up-conversion having a very high optical up-conversion yield is achieved. It became clear that a conversion material could be obtained. The present invention is an invention completed by further studying based on such findings.

［一般式（１）中、基Ａは、置換基を有することがある縮合環数が３〜５の多環芳香族化合物の２価の残基を示す。
基Ｂ¹及び基Ｂ²は、それぞれ独立して、下記一般式（２ａ）または（２ｂ）で表される３価の基を示す。

一般式（２ａ）及び（２ｂ）中、基Ｚが基Ａと結合しており、残りの２つの結合手がそれぞれ基Ｘ¹及び基Ｘ²と結合しており、基Ｚは、単結合、または飽和もしくは不飽和であり、直鎖もしくは分岐鎖のアルキレン基を示す。Ｒ_n ²は、０〜３個の置換基であって、ベンゼン環上の水素原子と置換しており、それぞれ独立に、アルキル基、アルコキシ基、フェニル基、水酸基、またはアミノ基を示す。
基Ｘ¹及び基Ｘ²は、それぞれ独立して、エーテル結合、エステル結合、アミド結合及びスルフィド結合からなる群から選択された少なくとも一種の結合を有することがある炭素数２以上の直鎖または分岐鎖のアルキレン基を示す。］
項２． 前記固体中の前記一般式（１）で表される化合物と、前記光増感剤との合計割合が、６０質量％以上である、項１に記載の光アップコンバージョン材料。
項３． 前記一般式（１）で表される化合物及び前記光増感剤により形成された結晶を含んでいる、項１または２に記載の光アップコンバージョン材料。
項４． 前記一般式（１）において、基Ａが、下記一般式（Ａ１）〜（Ａ２３）で表される多環芳香族化合物残基のいずれかである、項１〜３のいずれかに記載の光アップコンバージョン材料。

［一般式（Ａ１）〜（Ａ２３）中、２価の結合手は、それぞれ芳香環上の水素原子と置換可能な任意の位置に存在する。Ｒ_n ¹は、０個以上の置換基であって、それぞれ芳香環に結合した水素原子と置換しており、それぞれ独立に、アルキル基、アルコキシ基、フェニル基、水酸基、またはアミノ基を示す。］
項５． 前記一般式（１）において、基Ａが、下記一般式（Ａ１−１）、（Ａ１−２）、（Ａ２−１）、（Ａ３−１）、（Ａ４−１）、（Ａ５−１）、（Ａ５−２）、（Ａ６−１）、（Ａ９−１）、（Ａ９−２）、（Ａ９−３）、（Ａ９−４）、（Ａ１４−１）、（Ａ１４−２）、（Ａ１４−３）、及び（Ａ１４−４）で表される多環芳香族化合物残基のいずれかである、項１〜４のいずれかに記載の光アップコンバージョン材料。

［一般式（Ａ１−１）、（Ａ１−２）、（Ａ２−１）、（Ａ３−１）、（Ａ４−１）、（Ａ５−１）、（Ａ５−２）、（Ａ６−１）、（Ａ９−１）、（Ａ９−２）、（Ａ９−３）、（Ａ９−４）、（Ａ１４−１）、（Ａ１４−２）、（Ａ１４−３）、及び（Ａ１４−４）中、Ｒ_n ¹は、上記の一般式（Ａ１）〜（Ａ２３）と同様である。］
項６． 前記基Ｂ¹及び基Ｂ²は、それぞれ独立して、下記一般式（３ａ−１）〜（３ａ−４）で表される３価の基のいずれかである、項１〜５のいずれかに記載の光アップコンバージョン材料。

［一般式（３ａ−１）〜（３ａ−４）中、Ｒ_n ²は、一般式（２ａ）と同様である。］
項７． 前記一般式（１）において、基Ｘ¹及び基Ｘ²は、それぞれ独立して、エーテル結合、エステル結合、アミド結合及びスルフィド結合からなる群から選択された少なくとも一種の結合を有することがある炭素数が５〜１０の直鎖のアルキレン基である、項１〜６のいずれかに記載の光アップコンバージョン材料。
項８． 項１〜７のいずれかに記載の光アップコンバージョン材料に光を照射することにより、前記照射した光よりも短波長の光を発光させる、光波長の変換方法。
項９． 下記一般式（１）で表される化合物と、光増感剤とを含み、前記一般式（１）で表される化合物の溶液を、乾燥させる工程を備えている、光アップコンバージョン材料の製造方法。

［一般式（１）中、基Ａは、置換基を有することがある縮合環数が３〜５の多環芳香族化合物の２価の残基を示す。
基Ｂ¹及び基Ｂ²は、それぞれ独立して、下記一般式（２ａ）または（２ｂ）で表される３価の基を示す。

一般式（２ａ）及び（２ｂ）中、基Ｚが基Ａと結合しており、残りの２つの結合手がそれぞれ基Ｘ¹及び基Ｘ²と結合しており、基Ｚは、単結合、または飽和もしくは不飽和であり、直鎖もしくは分岐鎖のアルキレン基を示す。Ｒ_n ²は、０〜３個の置換基であって、ベンゼン環上の水素原子と置換しており、それぞれ独立に、アルキル基、アルコキシ基、フェニル基、水酸基、またはアミノ基を示す。
基Ｘ¹及び基Ｘ²は、それぞれ独立して、エーテル結合、エステル結合、アミド結合及びスルフィド結合からなる群から選択された少なくとも一種の結合を有することがある炭素数２以上の直鎖または分岐鎖のアルキレン基を示す。］
That is, the present invention provides the inventions of the following aspects.
Item 1. A solid optical up-conversion material containing a compound represented by the following general formula (1) and a photosensitizer.

[In the general formula (1), the group A represents a divalent residue of a polycyclic aromatic compound having a fused ring number of 3 to 5, which may have a substituent.
The group B ¹ and the group B ² independently represent a trivalent group represented by the following general formula (2a) or (2b).

In one general formula (2a) and (2b), it is bonded group Z is a group A, which binds the remaining two bonds are respectively groups X ¹ and group X ^2, group Z is a single bond , Or saturated or unsaturated, indicating a linear or branched alkylene group. R _n ² is 0 to 3 substituents, which are substituted with a hydrogen atom on the benzene ring, and each independently represents an alkyl group, an alkoxy group, a phenyl group, a hydroxyl group, or an amino group.
Group X ¹ and group X ² may each independently have at least one bond selected from the group consisting of ether bonds, ester bonds, amide bonds and sulfide bonds. Indicates the alkylene group of the chain. ]
Item 2. Item 2. The optical up-conversion material according to Item 1, wherein the total ratio of the compound represented by the general formula (1) and the photosensitizer in the solid is 60% by mass or more.
Item 3. Item 2. The optical up-conversion material according to Item 1 or 2, which comprises a compound represented by the general formula (1) and crystals formed by the photosensitizer.
Item 4. Item 2. The light according to any one of Items 1 to 3, wherein in the general formula (1), the group A is any of the polycyclic aromatic compound residues represented by the following general formulas (A1) to (A23). Up-conversion material.

[In the general formulas (A1) to (A23), the divalent bond exists at an arbitrary position on the aromatic ring that can be replaced with a hydrogen atom. R _n ¹ is 0 or more substituents, each of which is substituted with a hydrogen atom bonded to an aromatic ring, and independently represents an alkyl group, an alkoxy group, a phenyl group, a hydroxyl group, or an amino group. ]
Item 5. In the general formula (1), the group A is the following general formulas (A1-1), (A1-2), (A2-1), (A3-1), (A4-1), (A5-1). , (A5-2), (A6-1), (A9-1), (A9-2), (A9-3), (A9-4), (A14-1), (A14-2), ( Item 4. The optical up-conversion material according to any one of Items 1 to 4, which is any of the polycyclic aromatic compound residues represented by A14-3) and (A14-4).

[General formulas (A1-1), (A1-2), (A2-1), (A3-1), (A4-1), (A5-1), (A5-2), (A6-1) , (A9-1), (A9-2), (A9-3), (A9-4), (A14-1), (A14-2), (A14-3), and (A14-4) , R _n ¹ is the same as the above general formulas (A1) to (A23). ]
Item 6. Item 1 to 5, wherein the group B ¹ and the group B ² are independently any of the trivalent groups represented by the following general formulas (3a-1) to (3a-4). Optical up-conversion material described in.

[In the general formulas (3a-1) to (3a-4), R _n ² is the same as that of the general formula (2a). ]
Item 7. In the general formula (1), the group X ¹ and the group X ² may each independently have at least one bond selected from the group consisting of an ether bond, an ester bond, an amide bond and a sulfide bond. Item 2. The optical up-conversion material according to any one of Items 1 to 6, wherein the number is 5 to 10 and is a linear alkylene group.
Item 8. A method for converting an optical wavelength, which comprises irradiating the light up-conversion material according to any one of Items 1 to 7 with light having a wavelength shorter than that of the irradiated light.
Item 9. Production of an optical up-conversion material containing a compound represented by the following general formula (1) and a photosensitizer and comprising a step of drying a solution of the compound represented by the general formula (1). Method.

[In the general formula (1), the group A represents a divalent residue of a polycyclic aromatic compound having a fused ring number of 3 to 5, which may have a substituent.
The group B ¹ and the group B ² independently represent a trivalent group represented by the following general formula (2a) or (2b).

In one general formula (2a) and (2b), it is bonded group Z is a group A, which binds the remaining two bonds are respectively groups X ¹ and group X ^2, group Z is a single bond , Or saturated or unsaturated, indicating a linear or branched alkylene group. R _n ² is 0 to 3 substituents, which are substituted with a hydrogen atom on the benzene ring, and each independently represents an alkyl group, an alkoxy group, a phenyl group, a hydroxyl group, or an amino group .
Group X ¹ and group X ² may each independently have at least one bond selected from the group consisting of ether bonds, ester bonds, amide bonds and sulfide bonds. Indicates the alkylene group of the chain. ]

According to the present invention, it is possible to provide a solid light up-conversion light emitting material that realizes a high light up-conversion yield.

A laser beam having an optical output power of 4 mW is applied to the solid sample obtained in Example 1 to enlarge the beam diameter using a convex lens, and the solid sample spread in a circle is irradiated so as to be excited, and the solid sample is irradiated through a notch filter to prevent scattering of the irradiation light. It is a photograph of what was visually observed. 6 is a microscopic image of crystal grains (PtOEP: C7-sDPA molar ratio of 1: 720) contained in the solid sample obtained in Example 2. It is a photograph of the light emission from the crystal grains obtained in Example 2 observed with a CCD camera through a notch filter. It is an emission spectrum of the solid sample (crystal solid in the center of FIG. 3) obtained in Example 2. It is a photograph of the light emission from the crystal grains obtained in Example 4 observed with a CCD camera through a notch filter. It is an emission spectrum of the solid sample (crystal solid in the center of FIG. 5) obtained in Example 4. It is a photograph of the light emission from the crystal grains obtained in Example 5 observed with a CCD camera through a notch filter. It is an emission spectrum of the solid sample (crystal solid in the center of FIG. 7) obtained in Example 5.

The optical up-conversion material of the present invention contains a compound represented by the following general formula (1) and a photosensitizer, and is characterized by being a solid.

Here, the compound represented by the following general formula (1) is a compound that functions as an optical up-conversion illuminant in the optical up-conversion material of the present invention. Further, in the present invention, the "optical up-conversion illuminant" refers to a compound that emits light having a shorter wavelength than the absorbed light. In the optical up-conversion material of the present invention, the photosensitizer functions as an acceptor and the optical up-conversion illuminant functions as a donor. Hereinafter, the optical up-conversion light emitting material of the present invention will be described in detail.

[Light up-conversion illuminant]
The optical up-conversion light emitter is a compound represented by the above general formula (1), and has a function of emitting light having a shorter wavelength than the light absorbed by the optical up-conversion material of the present invention. In the general formula (1), the group A is bonded to the ^{group B 1} and the group B ^2. Further, the group B ¹ , the group X ¹ , the group B ² , and the group X ² are bonded in this order to form a ring, and the group A is located in this ring.

In the general formula (1), the group A represents a divalent residue of a polycyclic aromatic compound having a fused ring number of 3 to 5, which may have a substituent. Examples of the aromatic ring constituting the group A include a benzene ring, a cyclopentadienyl ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, a furan ring, a thiophene ring, and a siror ring.

Specific examples of the group A include polycyclic aromatic compound residues represented by the following general formulas (A1) to (A23).

In the general formulas (A1) to (A23), the position of the divalent bond is not particularly limited, and each exists at an arbitrary position on the aromatic ring that can be replaced with a hydrogen atom. The divalent bonds are preferably present on the same or adjacent aromatic rings, respectively. It is considered that this makes it possible to reduce the size of the ring, facilitate the interaction between the illuminants, and further increase the optical up-conversion yield. Further, the divalent bond is preferably located at a position where radicals are likely to be generated when there is no bond. The presence of a bond at such a position prevents the generation of radicals at these positions, and the radical reaction causes the illuminants to react with each other to form a dimer, resulting in a decrease in the optical up-conversion yield. Can be suppressed.

In the general formulas (A1) to (A23), R _n ¹ is 0 or more substituents, each of which is substituted with a hydrogen atom bonded to an aromatic ring. The upper limit of the number of R _n ¹ varies depending on the number of hydrogen atoms bonded to the aromatic rings of the general formulas (A1) to (A23), but is usually about 0 to 8, preferably about 0 to 4. 0 or more R _n ¹ independently represent an alkyl group, an alkoxy group, a phenyl group, a hydroxyl group, or an amino group. When R _n ¹ is an alkyl group or an alkoxy group, the number of carbon atoms is not particularly limited, but from the viewpoint of reducing the steric hindrance of the group A and facilitating the interaction between the luminescent materials, 1 to 1 is preferable. About 10 can be mentioned.

In the general formula (1), preferred groups A include the following general formulas (A1-1), (A1-2), (A2-1), (A3-1), (A4-1), and (A5-1). ), (A5-2), (A6-1), (A9-1), (A9-2), (A9-3), (A9-4), (A14-1), (A14-2), Examples thereof include polycyclic aromatic compound residues represented by (A14-3) and (A14-4). Since the group A has these structures, the illuminant has a structure in which a ring formed by ^{the group B 1} , the group X ¹ , the group B ² , and the group X ^{2 surrounds the group A in the central portion of the group A.} Become. It is considered that interactions are likely to occur between light emitters having such a structure, and it is possible to further increase the optical up-conversion yield. Further, the two bonds of the group A having these structures are located on carbon atoms on which radicals are likely to be generated in the absence of the bonds. That is, in these structures, the two bonds of group A prevent radicals from being generated at these positions. Therefore, it is considered that the radical reaction causes the illuminants to react with each other to form a dimer, and the decrease in the optical up-conversion yield is effectively suppressed.

General formulas (A1-1), (A1-2), (A2-1), (A3-1), (A4-1), (A5-1), (A5-2), (A6-1), In (A9-1), (A9-2), (A9-3), (A9-4), (A14-1), (A14-2), (A14-3), and (A14-4), R _n ¹ is the same as the above general formulas (A1) to (A23).

In the general formula (1), the group B ¹ and the group B ² independently represent a trivalent group represented by the following general formula (2a) or (2b).

In the general formulas (2a) and (2b), the group Z is bonded to the two bonds of the group A, respectively. Further, the remaining two bonds of the general formulas (2a) and (2b) are bonded to the group X ¹ and the group X ^{2 of the} general formula (1), respectively.

In the general formulas (2a) and (2b), the group Z is a single bond, saturated or unsaturated, and represents a linear or branched alkylene group. Further, in the general formula (2a), R _n ² is 0 to 3 substituents, which are substituted with a hydrogen atom on the benzene ring, and are independently an alkyl group, an alkoxy group, a phenyl group, and the like. Indicates a hydroxyl group or an amino group. When R _n ² is an alkyl group or an alkoxy group, the number of carbon atoms is not particularly limited, but ^{the steric hindrance of the group B 1} and the group B ² is reduced, the interaction between the luminescent materials is facilitated, and the increase From the viewpoint of achieving both increasing compatibility with the sensitizer, preferably about 1 to 10, more preferably about 5 to 10.

Specific examples of the group B ¹ and the group B ² include trivalent groups represented by the following general formulas (3a-1) to (3a-4) independently of each other.

R _n ² of the general formula (3a-1) ~ (3a -4) are respectively the same as R _n ² of the general formula (2a) and (2b).

In the general formula (1), one of the divalent bonds ^{of the group X 1} and the group X ^{2 is bonded to the group B 1} and the other is bonded to the ^{group B 2, respectively.} Group X ¹ and group X ² may each independently have at least one bond selected from the group consisting of ether bonds, ester bonds, amide bonds and sulfide bonds. It is an alkylene group of the chain. To reduce the steric hindrance of the radicals X ¹ and group X ^2, from the viewpoint of easily occur interactions between emitters, groups X ¹ and group X ² is preferably an ether bond, an ester bond, an amide bond and a sulfide Examples thereof include a linear alkylene group having 5 to 10 carbon atoms, which may have at least one bond selected from the group consisting of bonds, and more preferably a linear alkylene group having 5 to 10 carbon atoms or an ether. Examples thereof include a linear alkylene group having a bond and having 5 to 10 carbon atoms.

Examples of the compound represented by the general formula (1) include the following general formulas (1a-1) to (1a-3), (1b-1) to (1b-3), (1c-1) to (1c-3). ) Is particularly preferable.

In the general formulas (1a-1) to (1a-3), (1b-1) to (1b-3), (1c-1) to (1c-3), R ¹¹ and R ¹² are independent of each other. It represents a hydrogen atom, an alkyl group, an alkoxy group, a phenyl group, a hydroxyl group, or an amino group. When R ¹¹ and R ¹² are alkyl groups or alkoxy groups, respectively, the number of carbon atoms is not particularly limited, but from the viewpoint of facilitating the interaction between the illuminants, it is preferably about 1 to 10, more preferably. Is about 5 to 10. Further, R ²¹ and R ²² independently represent a hydrogen atom, an alkyl group, an alkoxy group, a phenyl group, a hydroxyl group, or an amino group. When R ²¹ and R ²² are alkyl groups or alkoxy groups, respectively, the number of carbon atoms is not particularly limited, but from the viewpoint of facilitating the interaction between the illuminants, it is preferably about 1 to 10, more preferably. Is about 5 to 10.

Specific examples of the compound represented by the general formula (1) include compounds represented by the following formulas (1a), (1b) and (1c).

The method for producing the compound represented by the general formula (1) is not particularly limited, and the compound can be produced by a known synthetic method. The method for producing the compound represented by the general formula (1) will be described by taking the compound represented by the above formula (1a) as an example. As shown in Scheme 1 below, first, anthraquinone (1a1) is reacted with 2,6-dimethyloxyphenyllithium to obtain a compound represented by the formula (1a2). The compound is then dehydrated to give 9,10-bis (2,6-dimethoxyphenyl) anthracene (1a3). Dehydration can be performed, for example, by heating to about 120 ° C. in the presence of _{NaI, NaH 2} PO ₂ · H _{2 O, and AcOH.} Next, _{using BBr 3} , demethylation of 9,10-bis (2.6-dimethoxyphenyl) anthracene (1a3) is performed to obtain a compound represented by the formula (1a4). Finally, the compound of the formula (1a4) is obtained by reacting the compound of the formula (1a4) with 1,7-dibromoheptane.

Further, the compound represented by the general formula (1) can also be produced by the method shown in Scheme 2 below. This production method will be described by taking the compound represented by the formula (1a) as an example. First, 9,10-dibromoanthracene (1a5) and 2,6-dimethoxyphenylboronic acid are combined by a Suzuki-Miyaura coupling reaction to form 9,10-bis (2,6-dimethoxyphenyl) anthracene (1a3). To get. After that, the compound of the formula (1a) is obtained in the same manner as in Scheme 1 above.

In the optical up-conversion material described later, the optical up-conversion illuminant of the present invention may be used alone or in combination of two or more.

The optical up-conversion material of the present invention contains a photosensitizer in addition to the compound represented by the general formula (1) (optical up-conversion illuminant). The photosensitizer is not particularly limited as long as it can absorb light energy and transfer the light energy to the light up-conversion illuminant of the present invention, and a known photosensitizer is used. Can be done.

From the viewpoint of suitably transferring light energy to the light up-conversion light emitter of the present invention, the photosensitizer preferably includes an organic metal complex. The metal constituting the organic metal complex is not particularly limited, but for example, Li, Mg, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ru, Pd, Ag, Re, Os. , Ir, Pt, Pb and the like, preferably Pt and Pd. Specific examples of the organic metal complex include a metal complex of porphyrin or a substitute thereof, a metal complex of phthalocyanine or a substitute thereof, and among these, a metal complex of porphyrin or a substitute thereof is preferably mentioned.

Particularly preferred photosensitizers include palladium complexes of porphyrins or their substitutions, and platinum complexes of porphyrins or their substitutions. Specific examples of the palladium complex of porphyrin or a substitute thereof include palladium tetrabenzoporphyrin, palladium tetraphenyltetrabenzoporphyrin, palladium octaethyl porphyrin, palladium cyclohexenoporphyrin and the like. Specific examples of the platinum complex of porphyrin or a substitute thereof include platinum tetrabenzoporphyrin, platinum tetraphenyltetrabenzoporphyrin, platinum octaethylporphyrin, platinum cyclohexenoporphyrin and the like.

In the optical up-conversion material of the present invention, one type of photosensitizer may be used alone, or two or more types may be used in combination.

In the optical up-conversion material of the present invention, the compounding ratio (molar ratio) of the compound represented by the general formula (1) and the photosensitizer is not particularly limited, but the up-conversion emission quantum yield is effective. The amount of the compound represented by the general formula (1) is preferably about 10 to 10000 mol, more preferably about 200 to 2000 mol, with respect to 1 mol of the photosensitizer.

In the optical up-conversion material of the present invention, the total ratio of the compound represented by the general formula (1) and the photosensitizer is not particularly limited, but from the viewpoint of effectively increasing the up-conversion emission quantum yield. Therefore, preferably 60% by mass or more, more preferably 90% by mass or more.

Further, the optical up-conversion material of the present invention contains a compound represented by the general formula (1) and crystals formed by the photosensitizer from the viewpoint of effectively increasing the up-conversion emission quantum yield. It is preferable to have. This is because, in the optical up-conversion material of the present invention, the luminous efficiency of the crystalline portion is particularly high.

In the present invention, the up-conversion emission quantum yield (Φuc) is calculated by the following mathematical formula (A).
Φuc ＝ 2 × Φstd × (Astd / Auc) × (Iuc / Istd) × (Nuc / Nstd) ² (A)

In the above formula, Astd and Auc are the absorbances of the standard substance and the sample under test at the excitation wavelength, respectively. In addition, Istd and Iuc are integrated emission intensities obtained by integrating the emission intensities of the standard substance and the sample to be measured at wavelengths over the entire light emitter, respectively. In particular, for the sample to be measured for up-conversion, it is the integrated emission intensity for the up-conversion emission band having a wavelength shorter than that of the excitation light. Nstd and Nuc are the refractive indexes of the solvent or ambient medium at the emission wavelengths of the standard substance and the sample to be measured, respectively.

As a standard substance, any substance that can be excited at the same wavelength and optical arrangement as the sample to be measured and whose reliable fluorescence quantum yield has been reported can be used. For example, in the examples described later, an ethylene glycol solution (100 μM) of rhodamine 101 was used as a standard substance, and its fluorescence quantum yield of 0.94 was used as Φstd. This fluorescence quantum yield value is based on the paper "C. Wurth, C. Lochmann, M. Spieles, J. Pauli, K. Hoffmann, T. Schuttrigkeit, T. Schuttrigkeit, T. Franzl, U. Resch-Genger, Appl. Spectroscop. 2010, 64, 733. ”, The fluorescence quantum yield of the dilute solution is 0.89, which is a value determined by using Φstd in the following formula (B).
Φfl ＝ Φstd × (Astd / Auc) × (Iuc / Istd) × (Nuc / Nstd) ² (B)

In addition, by directly measuring the ethylene glycol solution (100 μM) of rhodamine 101 by the method described in the paper “Shiina, S. Oishi, S. Tobita, Phys. Chem. Chem. Phys. 2009, 11, 9850.” It also matched the obtained values within an error of 3%.

The temperature at which the optical up-conversion material of the present invention is solid is not particularly limited as long as it is solid at the time of use, and is solid at least at 125 ° C. or lower, more preferably 80 ° C. or lower.

The method for producing the optical up-conversion material of the present invention is not particularly limited, but includes the compound represented by the above general formula (1) and the photosensitizer, and the compound represented by the general formula (1). The solution can be produced by a method comprising a step of drying. By adopting such a manufacturing method, an optical up-conversion material having particularly excellent luminous efficiency can be obtained.

Specifically, it contains a photosensitizer and has a high concentration of the compound (illuminant) represented by the general formula (1), specifically, a concentration of 1/10 or more of the saturation concentration. Further, a solution having 100 mol or more, more preferably 500 mol or more of luminescent substance molecules per 1 mol of the sensitizer molecule is prepared, and the solvent is rapidly volatilized from the solution to form a solid form. Optical up-conversion material can be manufactured quickly. As a method for rapidly volatilizing, a method such as using a highly volatile polar solvent such as tetrahydrofuran to drop dry on the surface of a glass substrate having good wettability can be exemplified. By producing the optical up-conversion material in this way, it is possible to quickly shift to the solid form in a state where the mutual dispersibility between the light emitter and the photosensitizer is high. As a result, aggregation of the light emitters or the photosensitizers during the transition from the liquid to the solid is suppressed, and the light emitters and the photosensitizers adjacent to each other are dispersed in the solid. Conceivable. Therefore, it is considered that the triplet energy transfer from the photosensitizer to the adjacent illuminant is efficiently performed in the solid, and as a result, a high up-conversion emission quantum yield is obtained. In Patent Document 2, a solution in which a photosensitizer and a compound (illuminant) represented by the general formula (1) are dissolved in a solvent is prepared, but the solvent is not dried and the solution is prepared. Is used as an optical up-conversion material. In Patent Document 2, a solution is assumed as a material system that realizes the highest up-conversion efficiency, and as shown in Non-Patent Document 3, the sensitizer and the illuminant are crystallized separately when volatilized from the solution. It was known that this did not cause up-conversion.

The solvent is not particularly limited, and for example, an organic solvent, water, or the like can be used. Specific examples of the organic solvent include nitrile solvents such as acetonitrile and benzonitrile, halogen solvents such as chloroform, dichloromethane, 1,2-dichloroethane, 1,1,2-trichloroethane, chlorobenzene and o-dichlorobenzene; tetrahydrofuran, Ether-based solvents such as dioxane; aromatic hydrocarbon-based solvents such as benzene, toluene, and xylene; cyclohexane, methylcyclohexane, n-pentane, n-hexane, n-heptan, n-octane, n-nonane, n-decane. Other aliphatic hydrocarbon solvents; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone; ester solvents such as ethyl acetate, butyl acetate, ethyl cell solve acetate; ethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, Polyhydric alcohols such as ethylene glycol monomethyl ether, dimethoxyethane, propylene glycol, diethoxymethane, triethylene glycol monoethyl ether, glycerin, 1,2-hexanediol and derivatives thereof; methanol, ethanol, propanol, isopropanol, cyclohexanol, etc. Alcohol-based solvent; sulfoxide-based solvent such as dimethyl sulfoxide; amide-based solvent such as N-methyl-2-pyrrolidone, N, N-dimethylformamide, etc. Among these, diacetone is preferable because of its high volatile nature. , Tetrahydrofuran, chloroform, dichloromethane, cyclohexane, but this is not the case depending on the volatile conditions. The solution can be dried by, for example, an inkjet method, a spray-drying method, or the like.

The optical up-conversion material of the present invention may be contained in a resin, glass, or the like. The resin is not particularly limited and can be appropriately set according to the intended use. For example, (meth) acrylic resin, polyester resin, polyurethane resin, epoxy resin, polyolefin resin, polyamide resin, polystyrene resin, cellulose resin, imide Known resins such as resins, polyvinyl chloride resins, fluororesins, silicone resins, polycarbonate resins, polysulfone resins, cyclic polyolefin resins, polylactic acid resins, and vinyl ester resins can be used. The shape of the resin is not particularly limited and can be appropriately set according to the intended use, and examples thereof include a film shape, a sheet shape, and a fibrous shape.

The glass is not particularly limited and can be appropriately set according to the intended use. For example, quartz glass, borosilicate glass, soda glass, alumina silicate glass, soda lime glass, non-alkali glass and the like can be used. can. The shape of the glass is not particularly limited and can be appropriately set according to the intended use, and examples thereof include a film shape, a sheet shape, and a fibrous shape.

In the optical up-conversion material of the present invention, the absorption intensity peaks at positions where the wavelength of the absorbed light is usually about 480 to 560 nm, preferably about 490 to 510 nm and about 525 to 540 nm. In the optical up-conversion material of the present invention, the emission intensity peaks at a position where the wavelength of the emitted light is usually about 400 to 550 nm, preferably about 400 to 480 nm. Further, the light irradiation power (mW) of the light irradiating the light up-conversion material of the present invention can be appropriately set according to the use of the light up-conversion material, and examples thereof include about 0.01 to 10 mW.

Since the optical up-conversion material of the present invention can efficiently convert the wavelength incident on the optical up-conversion material into a short wavelength, solar cells such as organic solar cells, natural light illumination, LEDs, organic EL elements, biomarkers, etc. It can be suitably used for applications such as displays, printing, security certification, optical data storage devices, and sensors. The optical up-conversion material of the present invention can be suitably used as a light wavelength conversion method that emits light having a wavelength shorter than that of the irradiated light by irradiating the light.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the examples.

[Example 1]
Pt-octaethylporphyrin (PtOEP) represented by the following formula (4) was added as a photosensitizer to a medium composed of tetrahydrofuran (THF) to prepare a predetermined concentration solution. Next, a powder of the compound (C7-sDPA) represented by the following formula (1a) was added as a light emitter to the predetermined concentration solution of PtOEP, and the mixture was uniformly stirred to obtain a solution. At this time, the molar ratio of the luminescent material to the photosensitizer was 720 mol of the luminescent material with respect to 1 mol of the photosensitizer, and the concentration of C7-sDPA was the saturation concentration at room temperature (23 ° C.). .. Next, the obtained solution was taken in a dropper, a drop was dropped on the surface of a slide glass, and the mixture was left to dry at room temperature (23 ° C.) for 1 minute in the air to obtain a solid sample spread in a circle. (See FIG. 1). The diameter of the circularly expanding portion was about 2 cm. The total ratio of the compound represented by the general formula (1a) and the photosensitizer in the solid sample is 100% by mass.

Next, a laser beam with an optical output power of 4 mW (center wavelength of incident light 532 nm, green, continuous light) is used on the obtained solid sample to expand the beam diameter using a convex lens so that the solid that spreads in a circle is excited. When visually observed through a notch filter that prevents the scattering of the irradiation light, the circumference of the solid that spread out in a circle emitted blue light (the photograph in FIG. 1 was taken under that condition). The laser beam diameter at the irradiation site exceeds 2 cm, the laser beam used has a Gaussian spatial profile with high light intensity at the center, and the irradiation light intensity at the circumference that emits blue light is 2.3 mW / Less than cm ^2.

[Example 2]
A solid sample composed of Pt-octaethylporphyrin (PtOEP, formula (4)) and a compound (C7-sDPA) represented by the formula (1a) prepared by the same method as in Example 1 was collected under an optical microscope. It was observed with (objective lens 20 times). As a result, it was shown that the solid sample consisted of granular crystals of various shapes (Fig. 2). Further, through the same objective lens, a green laser beam (continuous light) having a wavelength of 532 nm was irradiated to the crystal grains of the solid sample in the center of the microscope observation field (light intensity 6.0 W / cm ² at the irradiation site). In this state, the light emission from the solid sample was observed with a CCD camera through a notch filter, and the light emission spectrum was observed with a fiber spectroscope. As a result, it was confirmed that the crystal grains emitted bright blue light (Fig. 3). The obtained spectrum is shown in FIG. The total ratio of the compound represented by the general formula (1a) and the photosensitizer in the solid sample is 100% by mass.

[Example 3]
A region of a circularly expanded solid sample composed of Pt-octaethylporphyrin (PtOEP) prepared by the same method as in Example 1 and a compound (C7-sDPA) represented by the formula (1a) was passed through an 80 μm spacer. A sample covered with a cover glass was prepared (Sample 3-air). The total ratio of the compound represented by the general formula (1a) and the photosensitizer in the solid sample is 100% by mass.

Furthermore, although the sample was prepared by the same method, only the step of covering with the cover glass was performed in a high-purity argon (99.998% or more) atmosphere, and the periphery of the cover glass was sealed with an ultraviolet curable resin (sealing). In this case, the solid sample was masked so as not to be irradiated with ultraviolet rays.) A sample (Sample 3-Ar) in which the solid sample was in an argon gas environment was prepared.

In addition, although it is the same as sample 3-air, in the process of placing the cover glass, imaging oil (manufactured by Olympus, refractive index 1.404) was dropped so as to cover the solid sample before the cover glass was applied, and then the cover glass was placed. A sample (Sample 3-oil) was prepared.

Three types of samples prepared by the above procedure were prepared, and these were sequentially observed under an optical microscope (objective lens 20x), and the selected crystal grains were selected by using a fiber spectroscope connected to the microscope, and the same objective was used as it was. The emission spectrum is measured by irradiating the transmission and absorption spectrum of the crystal grain with a lens and green laser light (continuous light, light intensity 6.0 W / cm ^{2 at the irradiation site) with a wavelength of 532 nm and measuring through a notch filter.} Was measured. Furthermore, using the same spacer, slide glass, and cover glass as the above three samples, a sample filled with an ethylene glycol solution (100 μM) of Rhodamine 101 between the two glasses is used as a reference sample, and the permeation absorption is performed under the same conditions as the above three samples. The spectrum and emission spectrum were measured. From these data, the emission quantum yield of the crystal grains of each sample was determined based on the above-mentioned mathematical formula (A). The obtained emission quantum yield varies from crystal grain to crystal grain, but Table 1 shows the average value and standard deviation of 10 crystal grains for each sample.

As shown in Table 1, the up-conversion emission quantum yield exceeds 10% in all the samples. At present, no more than 10% of solid materials have been reported for optical up-conversion based on triplet-triplet annihilation. Of the three types of samples, sample 3-Ar has the highest average value, but considering the standard deviation, there is no significant difference from sample 3-oil. Immersion oil has the effect of promoting refractive index matching with the surface of solid crystals and reducing loss due to scattering and reflection of solid samples. On the other hand, in sample 3-Ar, the periphery of the solid sample is a gas, and the refractive index matching is not sufficiently obtained. However, since the difference between these samples is not remarkable, it can be concluded that the error due to insufficient refractive index matching is smaller than the individual difference of crystal grains. In addition, it can be said that the sample 3-air, whose ambient environment is air, is not much different from the other two samples in consideration of the error. It is known that the up-conversion emission quantum yield of a liquid optical up-conversion material is significantly reduced in the presence of oxygen, but the solid sample of this example is not significantly affected even in air. ing.

The up-conversion emission yield (maximum) of the dimethylsulfoxide solution containing the Pt-octaethylporphyrin (PtOEP, formula (4)) and the compound (C7-sDPA) represented by the formula (1a) shown in Patent Document 2. Although the measurement conditions were different from 15.1%), the up-conversion emission yield of the solid optical up-conversion material obtained in this example was a high value.

[Comparative Example 1]
In the same manner as in Example 3, the compound (DPA) represented by the following formula is used instead of the compound (C7-sDPA) represented by the formula (1a) as the light emitting body, and the light emitting body and photosensitizer at this time are further used. The molar ratio with the sensitizer is the same as in Example 3 except that the luminescent material is 1000 mol with respect to 1 mol of the photosensitizer (Sample 4-air, Sample 4-Ar, Sample 4). -Oil, and the environment surrounding the solid sample is air, argon gas, and imaging oil, respectively), and the up-conversion emission quantum yield was measured by the same procedure and method as in Example 3. As a result, the results shown in Table 2 were obtained as the average value and standard deviation of the up-conversion emission quantum yields for 10 crystal grains for each sample. Obviously, these comparative examples are inferior to Example 3 shown in Table 1.

[Example 4]
2,6-Dioctyl-C7s-DPA (general formula (1a-) represented by the following formula in the same manner as in Example 1 and instead of the compound (C7-sDPA) represented by the formula (1a) as a light emitter. 1), and the molar ratio of the luminescent material to the photosensitizer at this time is the same as that of Example 3 except that the luminescent material is 1000 mol with respect to 1 mol of the photosensitizer. In the same manner, a solid sample spread in a circle was obtained. Next, the light emission of the solid sample was observed in the same manner as in Example 2 except ^{that the excitation light intensity at the irradiation site was 3.0 W / cm 2.} As a result, it was confirmed that the crystal grains emitted bright blue light (FIG. 5). The obtained spectrum is shown in FIG. 6, and the compound of the following formula is shown. Was synthesized by using 2,6-dibromoanthraquinone instead of anthraquinone in the method described in paragraph [0036] of International Publication 2014/136619A1. Further, only the step of covering with a cover glass was performed in the air. When the emission quantum yield was measured by the same method as in Example 3 except for some cases, the average value for 8 crystal grains for each sample was 0.20 and the standard deviation was 0.06, although there were variations for each crystal grain. The up-conversion emission amount yield of the solid photo-up-conversion material obtained in Example 4 was a high value even when compared with Comparative Example 1. It is represented by the following formula in the solid sample. The total ratio of the compound and the photosensitizer is 100% by mass.

[Example 5]
C7s-bis (4-octylphenyl) anthracene (general formula 1a) represented by the following formula in the same manner as in Example 1 and instead of the compound (C7-sDPA) represented by the formula (1a) as a light emitter. -2), and the molar ratio of the luminescent material to the photosensitizer at this time is Example 3 except that the luminescent material is 1000 mol with respect to 1 mol of the photosensitizer. In the same manner as above, a solid sample spread in a circle was obtained. Next, at a light intensity of 6.0 W / cm ² at the irradiated site, luminescence was observed by the same method as in Example 2, and the luminescence spectrum was measured. As a result, it was confirmed that the crystal grains emitted bright blue light (Fig. 7). The obtained spectrum is shown in FIG. The compound of the following formula is synthesized by using 2,6-dimethoxy-4-octylphenyllithium instead of 2,6-dimethoxyphenyllithium in the method described in paragraph [0036] of International Publication 2014/136619A1. bottom. Further, when the emission quantum yield was measured by the same method as in Example 3 except that the step of covering with the cover glass was performed only in the atmosphere, the emission quantum yield was measured. The average value for 9 crystal grains was 0.059, and the standard deviation was 0.004. Even when compared with Comparative Example 1, the up-conversion emission yield of the solid optical up-conversion material obtained in Example 5 was a high value. The total ratio of the compound represented by the following formula and the photosensitizer in the solid sample is 100% by mass.

Claims (8)

It includes a compound represented by the following general formula (1), and a photosensitizer, Ri solid der,
A compound represented by the general formula in said solid (1), the total proportion of the photosensitizer, Ru der least 60 wt%, optical upconversion material.

[In the general formula (1), the group A represents a divalent residue of a polycyclic aromatic compound having a fused ring number of 3 to 5, which may have a substituent.
The group B ¹ and the group B ² independently represent a trivalent group represented by the following general formula (2a) or (2b).

In the general formulas (2a) and (2b), the group Z is bonded to the group A, the remaining two bonds are bonded to the group X ¹ and the group X ² , respectively, and the group Z is a single bond. Alternatively, it is saturated or unsaturated and exhibits a linear or branched alkylene group. R _n ² is 0 to 3 substituents, which are substituted with a hydrogen atom on the benzene ring, and each independently represents an alkyl group, an alkoxy group, a phenyl group, a hydroxyl group, or an amino group.
Group X ¹ and group X ² may each independently have at least one bond selected from the group consisting of ether bonds, ester bonds, amide bonds and sulfide bonds. Indicates the alkylene group of the chain. ] It contains crystals formed by the compound and the photosensitizer represented by the general formula (1), optical upconversion material according to claim 1. The optical up-conversion according to claim 1 or 2 , wherein in the general formula (1), the group A is any of the polycyclic aromatic compound residues represented by the following general formulas (A1) to (A23). material.

[In the general formulas (A1) to (A23), the divalent bond exists at an arbitrary position on the aromatic ring that can be replaced with a hydrogen atom. R _n ¹ is 0 or more substituents, each of which is substituted with a hydrogen atom bonded to an aromatic ring, and independently represents an alkyl group, an alkoxy group, a phenyl group, a hydroxyl group, or an amino group. ] In the general formula (1), the group A is the following general formulas (A1-1), (A1-2), (A2-1), (A3-1), (A4-1), (A5-1). , (A5-2), (A6-1), (A9-1), (A9-2), (A9-3), (A9-4), (A14-1), (A14-2), ( The optical up-conversion material according to any one of claims 1 to 3 , which is any of the polycyclic aromatic compound residues represented by A14-3) and (A14-4).

[General formulas (A1-1), (A1-2), (A2-1), (A3-1), (A4-1), (A5-1), (A5-2), (A6-1) , (A9-1), (A9-2), (A9-3), (A9-4), (A14-1), (A14-2), (A14-3), and (A14-4) , R _n ¹ is the same as the above general formulas (A1) to (A23). ] Any of claims 1 to 4 , wherein the group B ¹ and the group B ² are independently any of the trivalent groups represented by the following general formulas (3a-1) to (3a-4). Optical up-conversion material described in Crab.

[In the general formulas (3a-1) to (3a-4), R _n ² is the same as that of the general formula (2a). ] In the general formula (1), the group X ¹ and the group X ² may each independently have at least one bond selected from the group consisting of an ether bond, an ester bond, an amide bond and a sulfide bond. The optical up-conversion material according to any one of claims 1 to 5 , which is a linear alkylene group having a number of 5 to 10. A method for converting an optical wavelength, which comprises irradiating the light up-conversion material according to any one of claims 1 to 6 with light to emit light having a wavelength shorter than that of the irradiated light. The method for producing an optical up-conversion material according to any one of claims 1 to 6.
Production of an optical up-conversion material containing a compound represented by the following general formula (1) and a photosensitizer and comprising a step of drying a solution of the compound represented by the general formula (1). Method.

[In the general formula (1), the group A represents a divalent residue of a polycyclic aromatic compound having a fused ring number of 3 to 5, which may have a substituent.
The group B ¹ and the group B ² independently represent a trivalent group represented by the following general formula (2a) or (2b).

In the general formulas (2a) and (2b), the group Z is bonded to the group A, the remaining two bonds are bonded to the group X ¹ and the group X ² , respectively, and the group Z is a single bond. Alternatively, it is saturated or unsaturated and exhibits a linear or branched alkylene group. R _n ² is 0 to 3 substituents, which are substituted with a hydrogen atom on the benzene ring, and each independently represents an alkyl group, an alkoxy group, a phenyl group, a hydroxyl group, or an amino group.
Group X ¹ and group X ² may each independently have at least one bond selected from the group consisting of ether bonds, ester bonds, amide bonds and sulfide bonds. Indicates the alkylene group of the chain. ]

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