JP3967071B2 - Near-infrared light emitting materials by charge transfer complex formation of porphyrin fullerene films - Google Patents

Description

【００１７】
【表２】

【００１８】
△Ｇは、電子移動の自由エネルギー変化量、λsは、溶媒または外圏（outer-sphere）に由来する再配列エネルギー、λvは、ドナー−アクセプターの振動に由来する再配列エネルギー、そしてνvは振動因子である。ＣＴ（電荷移動）の発光バンドの形は前記４つのパラメーターにより決定されることが理論化されており〔文献；R.A,Marcus,J.Phys.Chem.93(1989)3078〕、実際のＣＴ発光系にも適用されている〔文献；I.R.Gould,R.H.Young,R.E.Moody,S.Farid,J.Phys.Chem.,95(1991)2068〕。そこで上記の解析法に従い、ポルフィリン・フラーレン混合膜中での電子移動パラメーターを算出した（図４）。驚くべきことにその全再配列エネルギー（λ＝λs＋λv）は0.17-0.20 eVと非常に小さな値となった。これは今までの連結系（I.R.Gould,S.Farid, Acc.Chem.Res.29(1996)522）および分子間系（G.L.Closs,J.R.Miller,Science,240(1988)440; T.Haberle,J.Hirsch,J.Pollinger,H.Heitele,M.E.Michel-Beyerle,C.Ander,A.Dohling,C.Krieger,A.Ruckemann,H.A.Staab,J.Phys.Chem.100(1996)18269;A.Osuka,G.Noya,S.Taniguchi,T.Okada,Y.Nishimura,I.Yamazaki,N.Mataga,Chem.Eur.J.6(2000)33.）のドナー・アクセプターの組み合わせの値（＞０．５ ｅＶ）としては最も小さな値であり、光合成の電荷分離の初期過程の小さな再配列エネルギー(０．２ｅＶ; The Photosynthetic Reaction Center, J.Deisenhofer,J.R.Norris,Eds.,Academic Press,1993)に匹敵するものである。すなわち、ポルフィリンとフラーレンの組み合わせが光合成型の電荷分離を人工的に行う上で理想的であることを明らかに示している。
【００１９】
【発明の効果】
以上述べたように、本発明で得られた有機フイルムは近赤外に発光を示し、再現性も良く安定した特性を示す。現在、緑色の有機ＥＬ素子は高輝度の材料が開発されているが、赤色の有機ＥＬ素子は十分な性能の材料が見い出されていないのが現状である。本発明は従来のホール・電子再結合による励起状態の形成とは全く異なった、ＣＴ状態を有機ＥＬに応用できる可能性を秘めており、またその他の発光材料としても期待できる。
【図面の簡単な説明】
【図１】 ａ）、微結晶フイルムの発光スペクトル：１はＨ_２Ｐ−Ｐ_３４−Ｃ_６０、２はＨ_２Ｐ−Ｐ_３４／Ｃ_６０−ＲＥＦの混合物、３はＨ_２Ｐ−Ｐ_３４／Ｃ_６０、４はＴＰＰ／Ｃ_６０−ＲＥＦのｂ）、ＬＢフイルム（膜）の蛍光スペクトル
【図２】 ａ）、ＬＢフイルムの表面圧（ｍＮ／ｍ）−平均分子面積相関曲線、ｂ)、１０層からなるＬＢフィルムの吸収スペクトル
【図３】 波長依存性の蛍光スペクトル（ＤＡＳ）、τは蛍光寿命（４成分解析によりフィティングされた）
【図４】 １０％Ｈ_２Ｐ−Ｐ_３４−Ｃ_６０／ＯＤＡ膜の発光スペクトル（連続線）と電子移動パラメーターを求めるために解析された曲線（点線）との対比[0001]
BACKGROUND OF THE INVENTION
The present invention is particularly a metal coordination or porphyrin such metal-free and fullerenes, mixtures (bimolecular system) or as present in the same molecule represented by the general formula C according to claim 1 wherein The present invention relates to an organic near-infrared light emitting material in which a porphyrin part and a fullerene part form a charge transfer state to form a bimolecular solid film or are dispersed in an LB film forming matrix to form a film.
[0002]
[Prior art]
C ₆₀ fullerene, has attracted much attention over the past ten years. Since C ₆₀ fullerene is a novel acceptor three-dimensional shape, photoexcited electrons movable donor - often been used in the acceptor system. The photochemistry of these systems has been studied primarily in the liquid phase. On the other hand, it was recently discovered that porphyrins and fullerenes form naturally organized eutectics. And it is known that porphyrin / fullerene takes a spatially very close relative arrangement by intermolecular interaction (intermolecular distance: 3.0-3.5Å).
(Reference: MMOlmstead, DACosta, K. Maitra, BCNoll, SLPhillips, PMVan.Calcar,
ALBalch, J. Am. Chem. Soc., 1999, 121, 7090-7097.). In the case of a covalently bonded bimolecular bond, that is, in the case of a compound having a porphyrin ring and a fullerene group in the same molecule, the adjacent arrangement of the porphyrin and fullerene moieties (in compound F, the amide is bonded to the ortho position of the benzene ring). The porphyrin and fullerene moieties cause the formation of a charge complex state in solution. These compounds are known to form efficient electron donor-acceptor complexes (Small Reorganization Energy of Electron Transfer in Porphyrin-Fullerene Dyads, H. Imahori, NV Tkachenko, V. Vehmanen, K Tamaki, H. Lemmetyinen, Y. Sakata, and S. Fukuzumi, Angew, Chem. Int. Ed). It is explained that the formation of such a charge complex (bimolecular solid) can be observed by the appearance of a new emission band in the near infrared region (NIR) 800-900 nm.
[0003]
However, precise molecular design and synthesis are required for the formation of closely adjacent porphyrin and fullerene moieties. Therefore, a new light-emitting material in which the porphyrin moiety and fullerene moiety form a charge transfer complex can be produced by a simpler method or a conventionally established film (sometimes called film) formation method. It was.
[0004]
[Problems to be solved by the invention]
In the process of studying a porphyrin-fullerene system composed of a solid film under such an idea, the present inventors have studied a bimolecular system (system that forms an electron donor-acceptor charge transfer complex). We observed strong fluorescence around 800 nm with the same origin as reported in. The inventors of the present invention have not observed the charge transfer luminescence of the porphyrin-fullerene complex in a mixed solution system or a linked system of porphyrins and fullerenes in a solution system in which both are separated from each other, but the solution is simply dried, We discovered a porphyrin-fullerene bimolecular solid system in which charge-transfer luminescence is observed just by drying (also called dreifilm).
[0005]
[Means for Solving the Problems]
A first aspect of the present invention is a mixture of a porphyrin represented by the general formula A according to claim 1 and a fullerene represented by the general formula B, or the general formula having a porphyrin ring and a fullerene group in the same molecule. A near-infrared light emitting material comprising a bimolecular solid film formed from a solution of compounds represented by C and having a charge transfer state in which a porphyrin portion and a fullerene portion are closely adjacent to each other.
[0006]
According to a second aspect of the present invention, a mixture of a porphyrin of the general formula A and the fullerene of the general formula B according to claim 1 or a compound having a porphyrin ring and a fullerene group in the same molecule is contained in the LB film-forming matrix. A film-like near-infrared light emitting material characterized in that a porphyrin portion and a fullerene portion are dispersed as a solid which is closely associated with each other in a charge transfer state. Preferably, the LB film-forming matrix material is octadecyl. The film-like near-infrared light-emitting material, which is an amine.
[0007]
Preferably, in each of the above inventions, the porphyrin compound is the compound D (hereinafter referred to as H ₂ P-P ₃₄ ), and the fullerene compound is expressed as the compound E (hereinafter referred to as C ₆₀ -REF). And a compound having a porphyrin ring and a fullerene group in the same molecule is the compound F (hereinafter referred to as H ₂ P—P ₃₄ —C ₆₀ ). It is.
[0008]
[Embodiments of the present invention]
The present invention will be described in more detail. In the present invention, near-infrared light emission must be present at the same time and adjacent to each other (to allow charge transfer), whether it is a mixture or a porphyrin ring and a fullerene group in the same molecule. is there.
A. The film of the present invention is produced by the following two methods.
1. Since the fullerene compound is soluble in chloroform, a mixture with porphyrin was prepared as a chloroform solution. The porphyrin / fullerene mixture solution (molar ratio 1: 2 of each compound in the solution) was applied on a glass substrate, and the solvent was evaporated to prepare a bimolecular microcrystal sample. A bimolecular microcrystal sample of a compound having a porphyrin ring and a fullerene group in the same molecule is also prepared from a chloroform solution.
2. Each compound used in the present invention lacks the amphiphilicity required for forming an LB film, and therefore, the functionality of the present invention is not achieved until it is combined with an LB film forming material that is an appropriate matrix for the compound. A film to be exhibited can be produced. The LB film can be prepared by a standard method using an LB5000 double barrier trough (KSV instrument, Helsinki, Finland).
[0009]
The synthesis and properties of the compound H ₂ P-P ₃₄ -C ₆₀ having a porphyrin ring and a fullerene group in the same molecule, and its reference compounds H ₂ P-P ₃₄ and C ₆₀ -REF fullerene have already been reported (for example, H. Imahori, M. Hagiwara, M. Aoki, T. Akiyama, S. Taniguchi, T. Okada, M. Shirakawa, Y. Sakata, J. Am. Chem. Soc., 118 (1996) 11771.). Incidentally, 5,10,15,20-tetraphenylporphyrin (TPP) is Aldrich (Aldrich) Co., _{buckminsterfullerene, C 60} is Fluka (Fluka, purity of greater than 98%) manufactured by, and octadecylamine Sigma The product made by the company (purity 99%) was used.
[0010]
Examples of the LB matrix material include amphiphilic compounds usually used for the formation of LB films, such as long-chain alkyl groups (at least 8 carbon atoms, preferably 15 to 24 carbon atoms), —NH ₂ groups, hydroxyl groups. Preferred examples include a compound having a hydrophilic group selected from the group consisting of a group, a thiol group, a carboxylic acid, a quaternary ammonium group, a phosphonium group, and the like, such as octadecylamine and octadecyl mercaptan. Further, as an amphiphilic compound, a known LB film-forming polymer compound, for example, a polymer containing N-substituted (meth) acrylamide (such as an alkyl group having 8 or more carbon atoms or a substituted phenyl group as a substituent) is preferable. Can be mentioned.
[0011]
【Example】
Description of measuring instruments Absorption spectra were recorded using a Shimadzu UV-2501PC ultraviolet-visible spectrophotometer.
2. Steady state fluorescence spectra were measured using a Fluorolog 3 fluorimeter (SPEX Inc.) equipped with a cooled infrared sensitive photomultiplier tube (Hamamatsu R2658), then Wavelength sensitivity was corrected. The fluorescence decay curve was measured by a known time correlated single photon counting method. The instrument response time is about 100 ps (fwhm) and the excitation wavelength is 590 nm. Attenuation correlation spectrum (DAS) is obtained by collecting attenuation data of different wavelengths over a certain integration time (typically 2 minutes) and fitting over multiple wavelengths using a multicomponent exponential approximation (usually This is a method of performing fluorescence lifetime analysis at a time over a certain wavelength range including wavelength dependency, whereas fluorescence lifetime measurement is performed with only one wavelength.) The pre-exponential term of the fluorescence decay spectrum was corrected according to the sensitivity spectrum of the microchannel plate photomultiplier tube (Hamamatsu R3809U-50).
[0012]
Example 1 and Symmetric Example Preparation of bimolecular films of porphyrin-fullerene single molecules and mixtures, and membranes of C ₆₀ mixtures.
1. A mixture bimolecular microcrystalline film of H ₂ P-P ₃₄ and C ₆₀ -REF was prepared by applying a chloroform solution of these compounds (molar ratio 1: 2) onto a glass substrate and evaporating the solvent.
2. A microcrystalline film of H ₂ P—P ₃₄ —C ₆₀ was prepared by applying a chloroform solution on a glass substrate and evaporating the solvent.
3. From _{H 2 P-P 34 / C} 60 mixed bilayer microcrystalline film toluene solution, and _TPP / C 60 Microcrystalline film of -REF bilayer were prepared from a chloroform solution. The emission spectra of these microcrystalline films are shown in FIG. 1 _{H 2 P-P 34 -C 60} , 2 is a mixture of _{H 2 P-P 34 / C} 60 -REF, 3 is _H 2 _P-P 34 _{-C 60} and 4 fine of _TPP / C 60 -REF The emission spectrum of a crystalline film is shown. Near-infrared light emission showing a light emission maximum at 770-810 nm is observed. From this,
(1) For the appearance of light emission in the 800 nm region, it is essential that fullerene and porphyrin are simultaneously present.
(2) Near-infrared (NIR) emission is not observed in solution (test with a maximum concentration of 1 mM).
[0013]
Example 2
Preparation of LB (Langmuir Brodget) film with good optical properties. Basically, in the case of the LB method, a monomolecular film can be formed, and the molecule needs to be amphiphilic in order to obtain a sufficient film volume (multilayer film). The porphyrins and fullerenes used in the present invention do not have amphiphilic properties that enable the formation of the LB film. However, by mixing the compounds with a suitable LB film-forming matrix molecules such as octadecyl Amin (ODA), it was found that it is possible to form a film (film) using the LB method. Then, the film | membrane of this invention was prepared using the LB method using octadecylamine (ODA). The LB film was prepared by an ordinary standard method using an LB5000 double barrier trough. That is, H ₂ P-P ₃₄ -C ₆₀ / ODA, ODA / C ₆₀ -REF and H ₂ P-P ₃₄ / ODA mixtures were each dissolved in chloroform, and the resulting solution was developed on the water surface to form a single molecule. Film is formed and transferred to the glass surface. By repeating this, a multilayer film having an appropriate thickness can be formed. The magnitude of light absorption of the film is proportional to the thickness (stacking degree) of the film. The surface pressure (π) -average molecular area (nma) curve (isotherms) of the mixed film is shown in FIG. Nma is 1 nm ² about a single layer of fullerenes, it is known to vary between 0.8-2Nm ² for porphyrins. The nma of the LB film from the above mixture is the same value as that of a pure octadecylamine (ODA) layer, about 0.2 m ² (FIG. 2), and H ₂ P—P ₃₄ —C ₆₀ / ODA or C ₆₀ on the water surface. The REF / ODA mixture does not form a good LB film incorporated in the monolayer.
[0014]
That is, in the film formed from H ₂ P-P ₃₄ -C ₆₀ / ODA and ODA / C ₆₀ -REF, H ₂ P-P ₃₄ -C ₆₀ or C ₆₀ -REF molecules are not successfully incorporated into the LB matrix film. The structure is located at the end portion. In contrast, the membrane formed from the H ₂ P-P ₃₄ / ODA mixture has a structure in which the average molecular area value (mma) gradually increases, that is, the H ₂ P-P ₃₄ molecule has a matrix ODA. It is taken in and forms a single film structure. The formed film was optically uniform and reproducible. FIG. 1-b) shows the emission spectrum of 10% H ₂ PP ₃₄ -C ₆₀ / ODA, LB film. This emission spectrum has emission characteristics similar to those of the bimolecular microcrystalline film of the mixture of H ₂ P-P ₃₄ / C ₆₀ -REF in Example 1 (the curve 2 in FIG. 1-a). From this, it is understood that neither the characteristics of the LB film nor the characteristics of the microcrystalline film are essentially changed. That is, it is possible to arrange the porphyrin and fullerene close to each other even in the LB film. As understood from the absorption spectrum (OD) in FIG. 2B, an appropriate amount of chromophores is transferred to the surface of the glass substrate.
[0015]
Table 1 below shows the emission quantum efficiency φ and the average fluorescence lifetime τ _av [multi-component exponential approximation fitting, that is, τ _av = Σaiτi / Σai (where τi is the fluorescence lifetime, and ai is the pre-exponential factor). )], And Table 2 shows the electron transfer parameters calculated from the charge transfer emission of the various donor-acceptor combinations. The luminous efficiency of the sample was determined using TPP (5,10,15,20-tetraphenylporphyrin) as a comparative sample. Further, the light emission amount was obtained by integrating in the range of 620-1000 nm. Fluorescence of 10% H ₂ P-P ₃₄ -C ₆₀ / ODA, LB film shows medium lifetime with short life component (τ ₁ = 45 ps) showing the same emission spectrum as H ₂ P-P ₃₄ , LB film Analysis with the light emission component from the intermediate (τ ₂ = 215 ps) and the two components with long lifetime (τ ₃ = 1.17 ns, τ ₄ = 3.4 ns) that emit light in the long wavelength region (700 to 800 nm) did it. The latter life is longer than H ₂ P-P ₃₄ / ODA (0.8 ns), C ₆₀ -REF / ODA (0.6 ns), therefore 10% H ₂ P-P ₃₄ -C ₆₀ / ODA In the LB film, the excited singlet of porphyrin is efficiently quenched, and a new emission band appears near 800 nm.
[0016]
[Table 1]

[0017]
[Table 2]

[0018]
ΔG is the amount of change in free energy of electron transfer, λs is the rearrangement energy derived from the solvent or outer-sphere, λv is the rearrangement energy derived from the donor-acceptor vibration, and νv is the vibration Is a factor. It has been theorized that the shape of the emission band of CT (charge transfer) is determined by the above four parameters [Literature: RA, Marcus, J. Phys. Chem. 93 (1989) 3078]. It is also applied to the system [Literature: IRGould, RHYoung, REMoody, S. Farid, J. Phys. Chem., 95 (1991) 2068]. Therefore, electron transfer parameters in the porphyrin / fullerene mixed film were calculated according to the above analysis method (FIG. 4). Surprisingly, the total rearrangement energy (λ = λs + λv) was as small as 0.17-0.20 eV. This is based on the conventional linkage system (IRGould, S. Farid, Acc. Chem. Res. 29 (1996) 522) and intermolecular system (GLCloss, JRMiller, Science, 240 (1988) 440; T. Haberle, J. Hirsch. , J. Pollinger, H. Heitele, MEMichel-Beyerle, C. Ander, A. Dohling, C. Krieger, A. Ruckemann, HAStaab, J. Phys. Chem. 100 (1996) 18269; A. Osuka, G. Noya , S. Taniguchi, T. Okada, Y. Nishimura, I. Yamazaki, N. Mataga, Chem. Eur. J. 6 (2000) 33.) as the value of donor-acceptor combination (> 0.5 eV) Is the smallest value, comparable to the small rearrangement energy (0.2 eV; The Photosynthetic Reaction Center, J. Deisenhofer, JRNorris, Eds., Academic Press, 1993) in the initial process of photosynthesis charge separation. That is, it clearly shows that the combination of porphyrin and fullerene is ideal for artificially performing photosynthetic charge separation.
[0019]
【The invention's effect】
As described above, the organic film obtained according to the present invention emits light in the near infrared, exhibits reproducibility and stable characteristics. Currently, a high-brightness material has been developed for the green organic EL element, but a material with sufficient performance has not been found for the red organic EL element. The present invention has a possibility that the CT state can be applied to the organic EL, which is completely different from the formation of the excited state by the conventional hole-electron recombination, and can be expected as other light emitting materials.
[Brief description of the drawings]
[1] a), emission spectrum of the microcrystalline film: 1 _{H 2 P-P 34 -C 60} , 2 is _{H 2 P-P 34 / C} 60 mixture -REF, 3 is _H 2 _{P-P 34} / _{C 60,} 4 is the _TPP / C 60 -REF b), fluorescence spectra [Figure 2] a of LB film (film)), the surface pressure of the LB film (mN / m) - average molecular area correlation curve, b) Absorption spectrum of LB film consisting of 10 layers [Figure 3] Wavelength-dependent fluorescence spectrum (DAS), τ is fluorescence lifetime (fitted by 4 component analysis)
FIG. 4 is a comparison between the emission spectrum (continuous line) of a 10% H ₂ PP ₃₄ -C ₆₀ / ODA film and the curve (dotted line) analyzed to determine the electron transfer parameter.

Claims (4)

Mixtures of metal coordination or metal-free porphyrins represented by general formula A and fullerenes represented by general formula B or solutions of compounds represented by general formula C having a porphyrin ring and a fullerene group in the same molecule A near-infrared light-emitting material comprising a bimolecular solid film in which a porphyrin part and a fullerene part form a charge transfer state closely adjacent to each other.

(In General Formula A , M is a diatomic H or metal, and Ar1 to Ar4 are unsubstituted or a phenyl group having a substituent independently selected from the group consisting of an alkyl group, an alkoxy group, a halogen, and an amide group; Yes, other hydrogens in the porphyrin ring are independent of the group consisting of alkyl group, alkoxy group, phenyl group, nitro group, amino group, halogen group, cyano group, carboxyl group, ester group, amide group, formyl group, sulfonic acid group It may be substituted by a group selected by

[General Formula B is selected from (a) to (c), and each R _{1 to} R ₄ is hydrogen or alkyl group, alkoxy group, phenyl group, nitro group, amino group, halogen group, cyano group, carboxyl Represents a group independently selected from the group consisting of a group, an ester group, an amide group, a formyl group, and a sulfonic acid group. n represents the degree of substitution, ranging from 0 to 6 substitutions. The fullerene part is C60, C70, C76, C78, C80, C82, C84, C86, C88, C90.

[In the general formula C, Ar has the same meaning as Ar 1 in the general formula A, and X is a group selected from —NH—CO—, —CO—NH—, —Ph—, —O—, —CO—O—. Represents. ). And the general formula porphyrins and one general formula porphyrin moiety and the fullerene moiety compounds is in LB film-forming matrix having a mixture or a porphyrin ring and fullerene group fullerenes in the same molecule of B of A according to claim 1 A film-like near-infrared light-emitting material characterized in that is dispersed as a solid that is closely associated in the charge transfer state.  The film-like near-infrared light-emitting material according to claim 2, wherein the LB film-forming matrix material is octadecylamine. 4. The mixture according to claim 1, wherein the porphyrin compound is the following compound D and the fullerene is the compound E , and the compound having a porphyrin ring and a fullerene group in the same molecule is the compound F. Near-infrared light emitting material.

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