JP4030382B2 - Highly efficient organic light-emitting compound - Google Patents

Description

【０００７】
一般式Ｃにおいて、Ｘ、Ｘ’、ＹおよびＹ’はそれぞれの環の水素原子に代えて置換した基であり、アルキル基、アシル基、アリール基およびハロゲン基からなる群から独立に選択され、ｍおよびｍ’は０または１〜４の整数、ｎおよびｎ’は０または１〜３の整数から独立に選択される。
【０００８】
一層好ましくは、前記一般式Ｃにおいてｍ、ｍ’、ｎおよびｎ’が全て０であることを特徴とする化合物１の高効率青色発光性化合物である。
【０００９】
【化４】

【００１０】
【本発明の実施の態様】
本発明をより詳細に説明する。
Ａ．本発明の基本は、各請求項に記載されている有機発光性化合物または有機発光材料であるが、有機発光材料としてのキー構造であることを説明するために、極めて高効率で強い発光を示した前記化合物１の５,５'-ビス-(１Ｈ−ベンズイミダゾール−２−イル)-〔２,２'〕ビピリジニル（以下、５，５’−Ｂｚｉｍ−ｂｐｙと表現する場合もある。）の発光特性を説明する。
【００１１】
５，５’−Ｂｚｉｍ−ｂｐｙはメタノール中、３５６ｎｍに極大をもつ強い吸収を示し、そのバンドを励起することにより４４５ｎｍに極大波長をもつ強い青色発光を示した（図１）。このような吸収・発光の特性は、２，２’−ビピリジン、１Ｈ−ベンズイミダゾール、およびこれらの混合溶液のいずれにおいても観測されなかった。因みに、５，５’−Ｂｚｉｍ−ｂｐｙ、２，２’−ビピリジニル（ｂｐｙ）, １Ｈ−ベンズイミダゾール（Ｂｚｉｍ）のＵＶスペクトル（メタノール中、２０℃)を図２に示す。５，５’−Ｂｚｉｍ−ｂｐｙのＭＯ計算(ＭＯＰＡＣ／ＡＭ１)による予備的な検討から、３５６ｎｍの強い吸収帯はベンズイミダゾールからビピリジンのπ^＊軌道への電荷移動（ＣＴ）性吸収帯であることが示唆された。
ここで同化合物の発光寿命(τ)をＨＯＲＩＢＡ ＮＡＥＳ−７００を用いて測定したところ、メタノール中、１．５ナノ秒（ｎｓ）と求められた。このように発光が短寿命であることと、その発光スペクトルが酸素の存在によって全く影響を受けなかったことから、同化合物の発光は一重項励起状態からの蛍光であると考えられる。さらに５，５’−Ｂｚｉｍ−ｂｐｙの蛍光量子収率(Φ)を、硫酸キニーネを基準物質（０．５Ｍ硫酸溶液中、１０^−４Ｍ以下の濃度で２５℃において、量子収率が５４．６％）として求めたところ、メタノール中、９３％であることが示され、同化合物が極めて高効率な青色発光（蛍光）化合物であることが示された（図３）。
【００１２】
５，５’−Ｂｚｉｍ−ｂｐｙのちょうど半分の構造のｐｙ−Ｂｚｉｍは蛍光量子収率(Φ)３９％を持つ。これらのことを、ｂｐｙの４，４’−位に１Ｈ−ベンズイミダゾール−２−イルを置換した化合物〔４，４’−ビス（１Ｈ−ベンズイミダゾール−２−イル）−（２，２’）ビピリジニル〕（ｂｐｙ−４，４’−Ｂｉｚｍ）の蛍光量子収率(Φ)がわずか３％であり、ｂｐｙの５，５’ −位に ４，５−ジヒドロ−１Ｈ−イミダゾール−２−イルを置換した化合物〔５，５’−ビス−（４，５−ジヒドロ−１Ｈ−イミダゾール−２−イル）（２，２’）ビピリジニル〕（２，２’−ｂｐｙ）がほとんど蛍光を示さないことと対比すると、ピリジン環の３−位、および２，２’−ビピリジンの５および／または５’−位における１Ｈ−ベンズイミダゾール−２−イル基との結合は新規なキー蛍光構造であることが判る。
【００１３】
【実施例】
ここでの説明は、本発明をより理解し易くするだけの目的であり、本発明を限定的に解釈するためのものではない。
【００１４】
実施例１
５,５'-ビス-(１Ｈ−ベンズイミダゾール−２−イル)-〔２,２'〕ビピリジニルの合成；
３００ｍＬナスフラスコに、５,５'−ジメチル−２,２'−ビピリジン５．００ｇ（２７ｍｍｏｌ）、過マンガン酸カリウム１５．６５ｇ（９９ｍｍｏｌ）、蒸留水１７５ｍＬを入れ、メカニカルスターラーを用いて撹拌しながら加熱還流を行った。４時間後、過マンガン酸カリウム１５．６５ｇ（９９ｍｍｏｌ） を追加し、さらに１晩加熱還流した。室温まで冷却後、生成した二酸化マンガンをよく蒸留水とエーテルで洗いながら吸引ろ過にて取り除いた。ろ液を５００ｍＬ分液ロートに移し替え、未反応原料をエーテル (５０ｍＬ×３回) で抽出した。水層に塩酸１０ｍＬを加え、析出した結晶（２,２'−ビピリジル−５,５'−ジカルボン酸）を吸引ろ過にて得た (３．７２ｇ)。
次に、５００ｍＬ三口フラスコにポリリン酸１０ｍＬとｏ−フェニレンジアミン０．９０ｇ（８．３０ｍｍｏｌ）と２,２'−ビピリジル−５,５'−ジカルボン酸１．０ｇ（４．１０ｍｍｏｌ） を入れ、１２０℃で数時間加熱した後、徐々に温度を２００℃まで上げて、１６時間加熱、反応させた。油浴の温度を１００℃程度まで下げた後、蒸留水３００ｍＬを加えたところ、溶液の色は黒から黄色へと変化し、黄色の固体が析出した。室温まで冷却した後、吸引ろ過し、得られた固体（リン酸塩）を乾燥させた(２．５０ｇ)。この固体を水酸化カリウム水溶液で溶かし、その溶液をｐＨ１１とし、溶け残った固体を吸引ろ過で集めることにより精製し、純粋な５,５'-ビス-(１Ｈ−ベンズイミダゾール−２−イル)-〔２,２'〕ビピリジニルを得た。
【００１５】
５，５’−Ｂｚｉｍ−ｂｐｙの特性；
淡黄色結晶、融点、＞３００℃、
ＮＭＲ特性；
^１Ｈ−ＮＭＲ（３００ ＭＨｚ,ＣＤＣｌ_３：ＴＦＡ １：１）δ９．８４７，９．２５５，８．９２３，７．９０７，７．８１６，^１３Ｃ−ＮＭＲ（３００ ＭＨｚ，ＣＤＣｌ_３：ＴＦＡ １：１）δ１４８．２７５，１４６．１４７，１４３．０６２，１４２．９３８，１３１．６７８，１２９．６０７，１２５．２６８，１２３．７５０，１１４．５９３．
ＭＳ ｍ／ｚ Ｍ^＋Ｃ_２４Ｈ_１５Ｎ_６としての計算値 ３８８．１４、実測値３８８
元素分析；分析値。Ｃ_２４Ｈ_１５Ｎ_６・Ｈ_２Ｏとしての計算値 Ｃ、７０．９２，Ｈ、４．４６、Ｎ，２０．６８、実測値 Ｃ、７１．０４、Ｈ、４．４７、Ｎ、２０．６４
【００１６】
５，５’−Ｂｚｉｍ−ｂｐｙの水素原子を他の置換基、例えば、前記発光特性の推論に基づいて、ベンズイミダゾールからビピリジンのπ^＊軌道への電荷移動（ＣＴ）性吸収を向上させる電子供与性置換基、さらには分子認識機能基など発光材料の機能性を付与する置換基とした化合物も同様に合成できる。
【００１７】
参考例１
２−ピリジン−３−イル−１Ｈ−ベンズイミダゾール（ｐｙ−Ｂｚｉｍ）の合成；
５００ｍＬ三口フラスコにポリリン酸１０ｍＬとｏ−フェニレンジアミン１．０ｇ（９．２５ｍｍｏｌ）とニコチン酸１．０ｇ（８．１２ｍｍｏｌ）を入れ、しばらく１２０℃で加熱した後、徐々に温度を２００℃まで上げた。８時間加熱した後、温度を１００℃以下に冷まし、 蒸留水３００ｍＬを加えた。室温まで冷却し、吸引ろ過を行い、ろ液に４倍量のエタノールを加えると、ピンク色に白濁した。吸引ろ過により固体を集め、乾燥させた （１．７１ｇ）。
【００１８】
ｐｙ−Ｂｚｉｍの物性；
状態 : ベージュ色結晶
融点 : ２５７℃
同定 : ^１Ｈ−ＮＭＲ（３００ MHz DMSO) δ９．３４１，８．６８２，８．４９７，７．６１８，７．２４８．^１３Ｃ−ＮＭＲ（４００ ＭＨｚ ＤＭＳＯ）δ １５０．４０６，１４８．５８３，１４７．３４５，１３８．８０７，１３３．７７５，１２５．７８９，１２３．９４２，１２２．５３９，１１５．１２３. ＭＳ ｍ／ｚ Ｍ^＋Ｃ_１２Ｈ_９Ｎ_３としての計算値１９５．０８、実測値 １９５．
【００１９】
ｐｙ−Ｂｚｉｍの吸収・発光特性データ；
ｐｙ−Ｂｚｉｍはメタノール中、３０６ｎｍに極大をもつ強い吸収を示し、そのバンドを励起することにより３６２ｎｍに極大波長をもつ強い紫色発光を示した（図４）。その蛍光量子収率(Φ)を、先のｂｐｙ−Ｂｚｉｍと同様に、硫酸キニーネを基準物質として求めたところ、メタノール中、３８％であることが示され、同化合物が充分に高効率な発光性有機化合物であることが示された。
【００２０】
【発明の効果】
以上述べたように、本発明により提供されたピリジンの３位並びに２，２’−ビピリジンの５−および５’−と１Ｈ−イミダゾール−２−イルとの結合による新規なキー蛍光構造は、種々の機能性材料である多くの誘導体の開発の可能性をもたらした点で、優れた効果をもたらすことは明らかである。
【図面の簡単な説明】
【図１】 実施例１の５，５’−Ｂｚｉｍ−ｂｐｙの吸収−発光特性
【図２】 Ｂｚｉｍ−ｂｐｙ、２，２’−ビピリジニル（ｂｐｙ）, １Ｈ−ベンズイミダゾール（Ｂｚｉｍ）のＵＶスペクトル
【図３】 実施例１の５，５’−Ｂｚｉｍ−ｂｐｙとキニーネの吸収−発光特性の比較
【図４】 参考例１のｐｙ−Ｂｚｉｍの吸収−発光特性[0001]
BACKGROUND OF THE INVENTION
The present invention is replacement or unsubstituted 2,2'-bipyridine 5 and 5 '- was replaced by the substituted or unsubstituted 1H- benzimidazol-2-yl group, novel to the light with high efficiency It relates to organic luminescent compounds.
[0002]
[Prior art]
In the case of organic light-emitting compounds, not only excitation and emission wavelengths can be changed by derivatization by introducing substituents, but various functions can be enhanced such as addition of recognition functions for compounds to be measured and polymerization. Is possible. Therefore, the discovery of a novel basic skeleton structure (key structure) that exhibits luminescence results in various developments, and has been energetically studied. As organic light emitting materials, biological, biochemical, and local environmental changes around luminescent molecules are considered as changes in luminescent properties such as luminescence intensity and luminescence time. For example, as an intracellular fluorescent probe Use as a light emitter for organic EL (electroluminescence) that emits light in the wavelength range necessary for the expression of natural color images, and use as dyes corresponding to various wavelengths of dye lasers. In particular, the development of preferable materials has been intensively performed.
For use as a light-emitting material, a material capable of combining a sufficient amount of light emission and a balance with other light-emitting materials suitable for color reproduction is desired. In addition, as a fluorescent material, it is basically desirable that the emission quantum yield is high. As a probe material, the distinction between excitation light and fluorescence is good. In biological measurement, the excitation wavelength is measured. What does not damage the material is desired.
[0003]
Therefore, for the development of a light emitting material having a new basic skeleton structure (key structure), it is important to be able to provide a compound having a chemical structure in which derivatives suitable for the various applications can be easily synthesized. Discovery of a new key structure capable of emitting blue light because there is not much high-efficiency light-emitting compound, especially high-efficiency blue light-emitting compound, and blue laser is used for high-density recording such as compact disc (CD). Is desired. Known organic low molecular blue light emitting materials are found in distyryl biphenyl light emitting materials, aryl ethynylbenzene light emitting materials, sexiphenyl light emitting materials, benzimidazole derivative light emitting materials, etc. It cannot be said that it is a light-emitting material with high brightness and high efficiency.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a novel high efficiency which is relatively easy to synthesize and has characteristics that improve the disadvantages of the above-mentioned conventional materials as a high-luminance, high-efficiency organic light-emitting compound, particularly a blue light-emitting organic compound. An organic light emitting compound or a light emitting material is provided.
Since bipyridine derivatives have been used as chemically useful ligands, their synthesis techniques have been established, and it is easy to obtain raw materials for synthesis. Bipyridine derivatives are also being studied for use as fluorescent receptors. However, the fluorescence characteristics of the bipyridine derivative itself have not been studied at all. The present inventors have paid attention to the ease of synthesis of bipyridine derivatives and the like, and are not attractive as ligands in terms of chemical structure, particularly compounds combining bipyridine derivatives, particularly bipyridine and benzimidazole. An unsuccessful synthesis of a compound in which benzimidazole was bonded to the 5,5′-position of bipyridine at the 2-position, and its emission characteristics were examined, it was found that it showed extremely high efficiency and strong blue emission. The problems of the present invention have been solved. In addition, 2-pyridin-3-yl-1H-benzimidazole (py-Bzim) having a half structure of the above structure has also been found to have considerably excellent luminescent properties, 2-pyridin-3-yl, 5,5 ′ -Binding of bipyridyl and benzimidazol-2-yl was confirmed to provide a novel key fluorescent structure.
[0005]
[Means for Solving the Problems]
The first of the present invention is a highly efficient luminescent compound characterized by having a chemical structure represented by the general formula C.
[0006]
[Chemical 3]

[0007]
In the general formula C, X, X ′, Y and Y ′ are groups substituted for hydrogen atoms of the respective rings, and are independently selected from the group consisting of alkyl groups, acyl groups, aryl groups and halogen groups, m and m ′ are independently selected from 0 or an integer of 1 to 4, and n and n ′ are independently selected from 0 or an integer of 1 to 3.
[0008]
More preferably, it is a high-efficiency blue light-emitting compound of Compound 1, wherein m, m ′, n and n ′ in the general formula C are all 0.
[0009]
[Formula 4]

[0010]
[Embodiments of the present invention]
The present invention will be described in more detail.
A. The basis of the present invention is the organic light-emitting compound or organic light-emitting material described in each claim, but in order to explain the key structure as the organic light-emitting material, it exhibits extremely high efficiency and strong light emission. In addition, 5,5′-bis- (1H-benzimidazol-2-yl)-[2,2 ′] bipyridinyl (hereinafter sometimes referred to as 5,5′-Bzim-bpy) of Compound 1 above. The light emission characteristics will be described.
[0011]
5,5′-Bzim-bpy exhibited a strong absorption with a maximum at 356 nm in methanol, and showed a strong blue emission with a maximum wavelength at 445 nm by exciting the band (FIG. 1). Such absorption and emission characteristics were not observed in any of 2,2′-bipyridine, 1H-benzimidazole, and mixed solutions thereof. In this connection, FIG. 2 shows UV spectra (5 ° C. in methanol) of 5,5′-Bzim-bpy, 2,2′-bipyridinyl (bpy), and 1H-benzimidazole (Bzim). From a preliminary study by MO calculation (MOPAC / AM1) of 5,5′-Bzim-bpy, the strong absorption band at 356 nm is a charge transfer (CT) absorption band from benzimidazole to the π ^* orbital of bipyridine. Was suggested.
Here, when the emission lifetime (τ) of the compound was measured using HORIBA NAES-700, it was determined to be 1.5 nanoseconds (ns) in methanol. Since the emission is short-lived and the emission spectrum is not affected at all by the presence of oxygen, the emission of the compound is considered to be fluorescence from a singlet excited state. Further, the fluorescence quantum yield (Φ) of 5,5′-Bzim-bpy was changed from quinine sulfate to a reference substance (0.5 M sulfuric acid solution at a concentration of 10 ⁻⁴ M or less at 25 ° C. and a quantum yield of 54. 6%), it was found to be 93% in methanol, indicating that the compound was a very high-efficiency blue luminescent (fluorescent) compound (FIG. 3).
[0012]
Py-Bzim, which is exactly half the structure of 5,5′-Bzim-bpy, has a fluorescence quantum yield (Φ) of 39%. These compounds are obtained by substituting 1H-benzimidazol-2-yl for 4,4′-position of bpy [4,4′-bis (1H-benzimidazol-2-yl)-(2,2 ′)]. Bipyridinyl] (bpy-4,4′-Bizm) has a fluorescence quantum yield (Φ) of only 3%, and 4,5-dihydro-1H-imidazol-2-yl is added to the 5,5′-position of bpy. The substituted compound [5,5′-bis- (4,5-dihydro-1H-imidazol-2-yl) (2,2 ′) bipyridinyl] (2,2′-bpy) exhibits little fluorescence; In contrast, it can be seen that the bond with the 1H-benzimidazol-2-yl group at the 3-position of the pyridine ring and at the 5 and / or 5′-position of 2,2′-bipyridine is a novel key fluorescent structure. .
[0013]
【Example】
The description here is only for the purpose of making the present invention easier to understand, and is not intended to limit the present invention.
[0014]
Example 1
Synthesis of 5,5′-bis- (1H-benzimidazol-2-yl)-[2,2 ′] bipyridinyl;
In a 300 mL eggplant flask, 5.00 g (27 mmol) of 5,5′-dimethyl-2,2′-bipyridine, 15.65 g (99 mmol) of potassium permanganate and 175 mL of distilled water were added and stirred using a mechanical stirrer. Heating to reflux was performed. After 4 hours, 15.65 g (99 mmol) of potassium permanganate was added, and the mixture was further heated to reflux overnight. After cooling to room temperature, the produced manganese dioxide was removed by suction filtration while thoroughly washing with distilled water and ether. The filtrate was transferred to a 500 mL separatory funnel, and the unreacted raw material was extracted with ether (50 mL × 3 times). Hydrochloric acid (10 mL) was added to the aqueous layer, and the precipitated crystals (2,2′-bipyridyl-5,5′-dicarboxylic acid) were obtained by suction filtration (3.72 g).
Next, 10 mL of polyphosphoric acid, 0.90 g (8.30 mmol) of o-phenylenediamine and 1.0 g (4.10 mmol) of 2,2′-bipyridyl-5,5′-dicarboxylic acid were placed in a 500 mL three-necked flask. After heating at 0 ° C. for several hours, the temperature was gradually raised to 200 ° C. and heated for 16 hours to react. When the temperature of the oil bath was lowered to about 100 ° C. and 300 mL of distilled water was added, the color of the solution changed from black to yellow, and a yellow solid was deposited. After cooling to room temperature, suction filtration was performed, and the resulting solid (phosphate) was dried (2.50 g). This solid was dissolved in aqueous potassium hydroxide solution, the solution was adjusted to pH 11, and the solid that remained undissolved was purified by collecting with suction filtration to obtain pure 5,5′-bis- (1H-benzimidazol-2-yl)- [2,2 ′] bipyridinyl was obtained.
[0015]
5,5′-Bzim-bpy properties;
Pale yellow crystals, melting point,> 300 ° C.,
NMR properties;
¹ H-NMR (300 MHz, CDCl ₃ : TFA 1: 1) δ 9.847, 9.255, 8.923, 7.907, 7.816, ¹³ C-NMR (300 MHz, CDCl ₃ : TFA 1: 1) δ 148.275, 146.147, 143.062, 142.938, 131.678, 129.607, 125.268, 123.750, 114.593.
_{^{MS m / z M + C 24}} H 15 Calculated 388.14 as _{N 6,} Found 388
Elemental analysis; analysis value. _{C 24 H 15 N 6 · H} 2 O Calculated C of, 70.92, H, 4.46, N , 20.68, Found C, 71.04, H, 4.47, N, 20. 64
[0016]
Electron donation to improve the charge transfer (CT) absorption of the hydrogen atom of 5,5′-Bzim-bpy to other substituents, for example, from the benzimidazole to the π ^* orbital of bipyridine based on the inference of the luminescent property A compound having a functional group and a substituent that imparts the functionality of the luminescent material such as a molecular recognition functional group can be synthesized in the same manner.
[0017]
Reference example 1
Synthesis of 2-pyridin-3-yl-1H-benzimidazole (py-Bzim);
In a 500 mL three-necked flask, add 10 mL of polyphosphoric acid, 1.0 g (9.25 mmol) of o-phenylenediamine and 1.0 g (8.12 mmol) of nicotinic acid, and after heating at 120 ° C for a while, the temperature is gradually raised to 200 ° C. It was. After heating for 8 hours, the temperature was cooled to 100 ° C. or lower, and 300 mL of distilled water was added. After cooling to room temperature, suction filtration was performed, and when 4-fold amount of ethanol was added to the filtrate, it became cloudy in pink. The solid was collected by suction filtration and dried (1.71 g).
[0018]
Physical properties of py-Bzim;
Condition: Beige crystal Melting point: 257 ° C
Identification: ¹ H-NMR (300 MHz DMSO) δ 9.341, 8.682, 8.497, 7.618, 7.248. ¹³ C-NMR (400 MHz DMSO) δ 150.406, 148.583, 147.345, 138.807, 133.775, 125.789, 123.942, 122.539, 115.123. MS m / z Calculated value 195.08 as M ⁺ C ₁₂ H ₉ N ₃ , measured value 195.
[0019]
Absorption / emission characteristic data of py-Bzim;
py-Bzim showed strong absorption having a maximum at 306 nm in methanol, and showed strong violet emission having a maximum wavelength at 362 nm by exciting the band (FIG. 4). When the fluorescence quantum yield (Φ) was determined using quinine sulfate as a reference material in the same manner as in the previous bpy-Bzim, it was found to be 38% in methanol, and the compound emitted sufficiently high efficiency. It was shown to be an organic compound.
[0020]
【The invention's effect】
As mentioned above, 5 and 5 'of the 3-position and 2,2'-bipyridine are provided pyridine by the present invention - a novel key fluorescent structure by binding of the 1H- imidazol-2-yl is Obviously, it has an excellent effect in terms of the possibility of developing many derivatives which are various functional materials.
[Brief description of the drawings]
1 is an absorption-emission characteristic of 5,5′-Bzim-bpy of Example 1. FIG. 2 is a UV spectrum of Bzim-bpy, 2,2′-bipyridinyl (bpy), 1H-benzimidazole (Bzim). 3 shows a comparison of absorption-emission characteristics of 5,5′-Bzim-bpy and quinine of Example 1. FIG. 4 shows absorption-emission characteristics of py-Bzim of Reference Example 1 .

Claims (2)

Emitting light compound you characterized by having a chemical structure represented by the general formula C.

In the general formula C, X, X ′, Y and Y ′ are groups substituted for hydrogen atoms of the respective rings, and are independently selected from the group consisting of alkyl groups, acyl groups, aryl groups and halogen groups, m and m ′ are independently selected from 0 or an integer of 1 to 4, and n and n ′ are independently selected from 0 or an integer of 1 to 3. A blue light-emitting compound of Compound 1 , wherein m, m ′, n and n ′ are all 0 in the general formula C.

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