Background
Nowadays, active research and development is being carried out on different display devices, in particular those based on Electroluminescence (EL) from organic materials.
Electroluminescence (EL) is a non-thermal generation of light caused by the application of an electric field to a substrate, in contrast to photoluminescence (i.e., light emission from an active material due to absorption and relaxation of light by radioactive decay of an excited state). In the latter case, excitation is accomplished by recombination of charge carriers (electrons and holes) of opposite sign charge injected into an organic semiconductor in the presence of an external circuit.
A simple prototype of an Organic Light Emitting Diode (OLED), a single layer OLED, typically consists of a thin film of an active organic material sandwiched between two electrodes, one of which needs to be semi-transparent in order to observe the light emission from the organic layer. Generally, a glass substrate coated with an Indium Tin Oxide (ITO) is used as an anode.
If an external voltage is applied across the two electrodes, charge carriers (i.e. holes) at the anode and electrons at the cathode are injected into the organic layer beyond a certain threshold voltage depending on the organic material applied. In the presence of an electric field, the charge carriers move through the active layer and are discharged non-radiatively when they reach the oppositely charged electrode. However, if the holes and electrons meet each other as they drift through the organic layer, excited singlet (antisymmetric) and triplet (symmetric) states (so-called excitons) are formed. Light is thus generated in the organic material by the decay of the excited state (or exciton) of the molecule. For every three triplet excitons formed by electrical excitation in an OLED, only one symmetric state (singlet) of excitons is produced.
Many organic materials exhibit fluorescence (i.e., emit light from a process that allows symmetry) from singlet excitons. This process can be very efficient because it occurs between states with the same symmetry. Conversely, if the symmetry of the exciton is different from that of the ground state, the radioactive relaxation of the exciton is not allowed and the luminescence will be slow and inefficient. Because the ground state is usually antisymmetric, the decay from the triplet breaks the symmetry. This process is therefore not allowed and the efficiency of the EL is very low. Therefore, the energy contained in the triplet state is mostly wasted.
Luminescence from a symmetry-forbidden process is called phosphorescence. Characteristically, phosphorescence lasts for up to a few seconds after excitation, unlike fluorescence that occurs in rapid decay, due to the low probability of a transition.
However, only a few organic materials have been identified from which the triplet state shows effective room temperature phosphorescence.
Successful use of phosphorescent materials has great promise for organic electroluminescent devices. For example, one benefit of using phosphorescent materials is that all excitons (formed by the combination of holes and electrons in the EL) that are (partially) triplet-based in phosphorescent devices can participate in energy transfer and luminescence. This can be achieved by its own phosphorescent emission or by using phosphorescent materials to improve the efficiency of the fluorescence process.
In each case, it is important that the emissive material provide electroluminescent emission in a relatively narrow band centered about a selected spectral region corresponding to one of the three primary colors (i.e., red, green, and blue). This is why they can be used as a colored layer in an OLED.
As a means for improving the performance of light emitting devices, green light emitting devices using iridium complexes from ortho-metallation have been reported. (Ir (ppy) 3: Triplex in situ metallated complexes of Iridium (III) with 2-phenylpyridine (ppy.) appl. phys. lett.1999, vol.75, p.4.
Thus, US 2005214576(SERGEY LAMANSKY ET AL.)29/09/2005 discloses phosphorescent emitting organometallic compounds useful in the manufacture of organic light emitting devices, exemplified by: platinum (II) (2-phenylpyridine-N, C)2') (acetylacetonate) [ Pt (ppy) (acac)]Platinum (II) (2- (p-tolyl) pyridine-N, C2') (acetylacetonate) [ Pt (tpy) acrylic acid (acac)]Platinum (II) (7, 8-benzoquinazol-N, C)3') (Acetylacetonate) [ Pt (bzq) acid (acac)]Platinum (II) (2-benzylpyridine-N, C)2') (acetylacetonate) [ Pt (bzpy) Acc (ocac)]Platinum (II) (2- (2' -thienyl) pyridine-N, C3') (acetylacetonate) [ Pt (thpy) (acac)]Platinum (II) (2- (2 ' - (4 ', 5 ' -benzothienyl) pyridine-N, C)3') (acetylacetonate) [ Pt (btp) water (acac)]Platinum (II) (2- (4 ', 6' -difluorophenyl) pyridine-N, C2') (acetylacetonate) [ Pt (4, 6-F)2ppy)(acac)]Platinum (II) (2- (4 ', 5' -difluorophenyl) pyridine-N, C2') (acetylacetonate) [ Pt (4, 5-F)2ppy)(acac)]And platinum (II) (2- (4 ', 5' -difluorophenyl) pyridine-N, C2') (2-methylpyridine) [ Pt (4, 5-F)2ppy)(pico)]。
WO 2005/117159(CDT OXFORD LIMITED)8/12/2005 discloses a metal complex for light emission, represented by formula I given below: M-L wherein M is a metal, L is a ligand and L comprises a substituted or unsubstituted heteroaromatic ring Ar containing at least one phosphorus atom. This implies that L is preferably a bidentate ligand, such as bipyridyl.
WO 2005/117160(CDT OXFORD LIMITED)8/12/2001 discloses a charged metal complex useful for light emitting devices. The charged metal complex may be fluorescent or phosphorescent, the complex comprising a metal M and a coordinating ligand. Suitable metals M include lanthanide metals, d-block metals, and metals that form fluorescent complexes. Furthermore, the ligand L may be monodentate, bidentate or tridentate.
SPROUSE，S.，et al.Photophysical effects of metal-carbonσbonds in ortho-methylated complexes of Ir (III) and Rh (III). J.am; chem.Soc. 1984, vol.106, p.6647-6653 discloses [ M (L)2Cl]2Dichloro-bridged dimers of the type in which L is 2-phenylpyridine (ppy) or benzo [ h ]]Quinoline (bzq), and M is Rh (III) or Ir (III). The above references teach that such ortho-metalated ligands exhibit higher spectral effects and lower energy charge transfer transitions than rh (iii) and ir (iii) complexes of 2, 2' -bipyridine (bpy) and 1, 10-phenanthroline (phen).
SLINKER, Jason D., et al, effective yellow electroluminism from a single layer of a cyclometallated iridium complex, J.am.chem.Soc.2004, vol.126, p.2763-2767, discloses a charged iridium complex, [ Ir (ppy)2-(dtb-bpy)]+(PF6)-And its use as a multifunctional cyclometallated ligand. The charged iridium complex comprises 3 ligands, with two cyclometallated ligands (ppy: 2-phenylpyridine) being selected so as to coordinate with the iridium metal center to further increase the ligand field splitting energy. In addition, the third ligand, 4, 4 '-di-tert-butyl-2, 2' -bipyridine (dtb-bpy), ensures the reversibility of redox, reduces self-quenching, and improves the device characteristics.
LEPELTIER, Marc, et al. Synthesis, structure and electrochemical properties of cyclometallated iridium (III) complexes with functionalized dipyridine ligands Eur.J.Inorg.chem.2005, p.110-117 disclose a series of cationic diaminium (III) complexes, [ Ir (ppy-N, C)2(L-N，N)](PF6) (Hppy ═ 2-phenylpyridine, L ═ 4, 4' -tBu2dpbpy、4，4′-Me2dpbpy、4，4′-Me2pbpy、4，4′-Me2bpy), and their photophysical and electrochemical properties.
SLINKER, Jason d., et al, green electroluminiscence from ionic iridium complex, appl, phys, lett, 2005, vol.86, p.173506 disclose iridium complexes [ Ir (F-mppy) 2: (F-mppy)dtb-ppy)]+(PF6-) Wherein F-mppy is 2- (4 ' -fluorophenyl) -5-methylpyridine and dtb-bpy is 4, 4 ' -di-tert-butyl-2, 2 ' -bipyridine.
EVANS, Rachel c., et al. Evaluation of the iridium as triplet elements in organic light emitting diodes.2006, vol.150, p.2093-2126 disclose several iridium (III) complexes, these complexes contain cyclometallated ligands such as 4- (4 ' -chlorophenyl) -6 ' -phenyl-2, 2 ' -bipyridine (clpby), 4 ' - (4-carboxyphenyl) -6 ' -phenyl-2, 2 ' -bipyridine (cppbpy), 4 ' -dibutyl-2-2 ' -bipyridine (dbbpy), 4- (4-hydroxyphenyl) -6 ' -phenyl-2, 2 ' -bipyridine (hppyy) or 4 ' - (4-tolyl) -6 ' -phenyl-2, 2 ' -bipyridine and derivatives thereof.
However, since the above prior art luminescent materials do not show pure colors, i.e. their emission bands (generally limited to green) cannot be concentrated around a selected spectral region (corresponding to one of the three primary colors: red, green and blue), their range of applications as OLED active compounds is narrow. It is therefore desirable to develop luminescent materials that are capable of emitting light of other colors, especially in the red region.
Red light emitters with good color coordinates, high efficiency and long lifetime are a currently recognized drawback in the field of organic electroluminescent devices.
Disclosure of Invention
It is therefore an object of the present invention to provide a luminescent material comprising an ortho-metalated complex with ancillary ligands as shown below.
Another object of the present invention is the use of said light emitting material and to provide an organic light emitting device comprising said light emitting material.
As described above, the present inventionIt is an object of the invention to provide a luminescent material comprising a neutral complex of formula (I):wherein: m represents a transition metal having an atomic number of at least 40, preferably in groups 8 to 12, more preferably Ir or Pt, and most preferably Ir; e1Represents an aromatic or heteroaromatic ring, optionally condensed with a plurality of further aromatic moieties or non-aromatic rings, wherein said ring optionally has one or more substituents, and optionally with a substituent comprising E2Form a fused structure, and wherein said ring utilizes an sp2The hybridized carbon is coordinated to the metal M; e2Represents a N-containing aromatic ring, optionally condensed with a plurality of additional aromatic moieties or non-aromatic rings, wherein said ring optionally has one or more substituents, and optionally with a compound comprising E1Form a fused structure, and wherein said ring utilizes an sp2The hybridized nitrogen is coordinated with the metal M; r' is the same or different at each occurrence and is selected from the group consisting of: -H, -F, -Cl, -Br, -NO2CN, -a straight or branched C1-20Alkyl radical, one C3-20Cycloalkyl, one straight or branched C1-20Alkoxy radical, a C1-20Dialkylamino group, one C4-14Aryl radical, a C4-14Heteroaryl, which groups may be substituted by one or more non-aromatic groups, wherein the substituents R', on the same ring or on two different rings, may together form another mono-or polycyclic ring system, optionally aromatic; x1、X2、X3、X4、X5And X6Each occurrence is the same or different and is independently selected from the group consisting of hydrogen, alkyl, aryl, heteroaryl, and alkyl, each of which may be substituted with at least one substituent; a. the-Is a counter anion; and n is1、n2、m1And m2Each occurrence is the same or different and represents an integer from 0 to 4Wherein n is1+m14 and n2+m2Provided that n is 41And n2Cannot be simultaneously zero.
As indicated by formula (I) above, two chelating monoanionic ligands are bonded to the metal through carbon and nitrogen atoms and include E1And E2And (4) partial. Such ligands are generally denoted as ortho-metalated ligands ("C ^ N ligands").
Chelate bidentate bipyridine ligands bonded to metals through two nitrogen atoms are roughly represented as ancillary ligands ("N ^ N ligands").
Surprisingly, it has been found that the neutral chelating ligand (N ^ N), also referred to as ancillary ligand, advantageously participates in the emission process when said ligand comprises a 2, 2' -bipyridine with conjugated ethylenically unsaturated substituents, thus having suitable electron accepting properties. That is, the ligand significantly shifts emission to lower energies (red-shift) and substantially improves the complex [ C ^ N]2M[N^N]Emission efficiency in the red region.
Furthermore, by means of chelate ligands (N ^ N) having conjugated ethylenically unsaturated substituents, it is possible to obtain chelate ligands comprising [ C ^ N ] of formula (I)]2M[N^N]A highly phosphorescent light emitting material of a complex having an emission maximum between 650nm and 750nm and thus corresponding to a red emission.
Preferably, the luminescent material of the present invention comprises a complex having the formula (II):wherein: x1、X2、X3、X4、X5、X6、R′、n1、n2、m1、m2And A-Have the same meaning as defined above; x is selected from the group consisting of: -CH-, -CR-, N-H, N-R1O, S and Se, wherein X is preferably selected from-CH-, -CR-CH-or S; y is selected from the group consisting of: -CH-, -CR-, N-H, N-R1O, S and Se, wherein Y is preferably selected from-CH ═ CH-, -CR ═ CH-, or S; r is identical or different on each occurrence and represents-F, -Cl, -Br, -NO2CN, -a straight or branched C1-20Alkyl radical, one C3-20Cycloalkyl, one straight or branched C1-20Alkoxy radical, a C1-20Dialkylamino, a vinyl group, which groups may be substituted by one or more aromatic or non-aromatic groups, a C4-14Aryl radical, a C4-14Heteroaryl, which groups may be substituted by one or more non-aromatic groups, wherein the substituents R, on the same ring or on two different rings, may together form another mono-or polycyclic ring system, optionally aromatic; a is an integer from 0 to 4; and b is an integer from 0 to 4.
More preferably, the luminescent material of the present invention comprises a complex of formula (IIA): \ AWherein: x1、X2、X3、X4、X5、X6、X、Y、R、R′、n1、n2、m1、m2A and A-Have the same meaning as defined above; x7、X8And X9Each occurrence is the same or different and is independently selected from the group consisting of hydrogen, alkyl, aryl, heteroaryl, and alkyl, each of which may be substituted with at least one substituent; r' is identical or different at each occurrence and represents-F, -Cl, -Br, -NO2CN, -a straight or branched C1-20Alkyl radical, one C3-20Cycloalkyl, one straight or branched C1-20Alkoxy radical, a C1-20Dialkylamino group, one C4-14Aryl radicals or a C4-14Heteroaryl, which groups may be substituted by one or more nonaromatic radicals, in which a plurality of substituents R' are on the same ring orOn two different rings, another mono-or polycyclic ring system may be formed together, optionally aromatic; b is an integer from 0 to 3; and w is an integer from 1 to 4.
Among the complexes of the invention, the preferred complex is that wherein X1、X2、X3、X4、X5And X6Each is independently selected from hydrogen and unsubstituted or substituted aryl groups.
More preferred complexes are those wherein: x1、X2And X3Two of (a) are hydrogen, the remaining one is a benzoic acid group; x4、X5And X6Two of (a) are hydrogen, the remaining one is a benzoic acid group; or X7、X8And X9Two of which are hydrogen and the remaining one is a benzoic acid group.
The complexes of formula (III) shown below give excellent results:wherein A is-Have the same meaning as defined above.
Complexes of formula (III) comprising a 2-phenyl-N-pyridine (ppy) ortho-metallated ligand and a bidentate bipyridine (bpy) bearing conjugated ethylenically unsaturated substituents as ancillary ligands are particularly advantageous for the present invention, due to their high color purity of emission in the red region.
The synthesis of complexes of formula (I), i.e., metal complexes comprising two ortho-metalated ligands (C ^ N ligands) and a neutral bidentate bipyridine ligand (N ^ N), can be accomplished by any known method. Details of synthetic methods suitable for preparing complexes of formula (I) are well disclosed in the following documents: "inorg. chem.," No.30, pg.1685 (1991); "Inorg.chem.," No.27, pg.3464 (1988); "Inorg.chem.," No.33, pg.545 (1994); "Inorg.chem.acta," No.181, pg.245 (1991); "J.organomet.chem.," No.35, pg.293 (1987); and "J.Am.chem.Soc", "No. 107, pg.1431 (1985).
In general, according to a first embodiment of the invention, those complexes conforming to formula (I) can be prepared according to the following reaction scheme:
the acid forms of the ortho-metalated ligands (H-C ^ N ligands) and ancillary ligands (N ^ N) are either commercially available or can be synthesized very easily by using well known organic synthesis reaction pathways.
Specifically, ortho-metalated ligands (H-C ^ N) can be prepared in good to excellent yields by Suzuki Coupling reactions using substituted pyridine compounds with The corresponding arylboronic acids (described in Olivier Lohse, et al, (The Palladium catalyst Suzuki Coupling of 2-and 4-chloropyridines. Syn. Lett. 1999, No.1, pgs.15-18) and U.S. Pat. No. 6670645(DU PONT DE NEMOURS) 30/12/2003).
Synthetic methods particularly suitable for the preparation of fluorinated ortho-metalated ligands (H-C ^ N) are described in JP 2003113164A (MITSUBISHI MATERIALS CORP)18/04/2003 and JP 2003113163A (MITSUBISHI MATERIALS CORP) 18/04/2003.
If the transition metal is iridium, compounds of the iridium (III) trihalide type, such as IrCl3·H2O, iridium (III) hexahalide compound such as M °3IrX°6(wherein X is a halogen (preferably Cl) and M.degree is a basic metal (preferably K)), and Iridium (IV) hexahalides such as M.degree2IrX°6(wherein X ° is a halogen, preferably Cl, and M ° is a basic metal, preferably K) ("Ir halogenated precursor") can be used as starting material for the synthesis of the complex of formula (I).
[C^N]2Ir(μ-X°)2Ir[C^N]2Complexing agentCompound VI, where M ═ Ir), where X ° is halogen (preferably Cl), can be prepared by using procedures already disclosed in the literature (s.sprouse, k.a.king, p.j.spelle, r.j.watts, j.am.chem.soc., 1984, 106, 6647-; m.e. thompson et al, inorg. chem., 2001, 40(7), 1704; m.e. thompson et al, j.am. chem.soc., 2001, 123(18), 4304-.
Preferably, the reaction is carried out by employing an excess of the neutral form of the ortho-metalated ligand (H-C ^ N). In addition, solvents with high boiling temperatures are preferred.
The term "high boiling temperature solvent" is intended to mean a solvent having a boiling point of at least 80 ℃, preferably at least 85 ℃ and more preferably at least 90 ℃. For example, suitable solvents are methoxyethanol, ethoxyethanol, glycerol, Dimethylformamide (DMF), N-methylpyrrolidone (NMP), Dimethylsulfoxide (DMSO), and the like, wherein the solvent may be used as such or in a mixture with water.
Optionally, the reaction may be carried out at a suitable Bronsted base(s) ((R))base), such as metal carbonates, in particular potassium carbonate (K)2CO3) Metal hydrides, in particular sodium hydride (NaH), metal ethoxylates or metal methoxides, in particular NaOCH3、NaOC2H5Alkyl ammonium hydroxides, in particular tetramethyl ammonium hydroxide, or imidazolium hydroxide.
Nucleophilic substitution of a metal atom with a suitable ligand (N ^ N) to form the corresponding [ C ^ N]2Ir[N^N])+A-(formula I, wherein Me ═ Ir) is preferably carried out by coarsely contacting a stoichiometric ligand N ^ N with a bridging intermediate (VI) in a suitable solvent.
Polar aprotic solvents are generally preferred for useThis reaction was carried out. One solvent that gives particularly good results is methylene Chloride (CH)2Cl2)。
The invention also relates to the use of the light-emitting material in the emission layer of an organic light-emitting device (OLED).
The invention further relates to the use of a luminescent material as a dopant in a host layer, thereby functioning as an emissive layer in an organic light emitting device.
If the luminescent material is used as a dopant in a host layer, it is generally used in an amount of at least 1% wt, preferably at least 3% wt, and more preferably at least 5% wt, relative to the total weight of the host layer and the dopant. Furthermore, it is generally used in an amount of up to 25% wt, preferably up to 20% wt, and more preferably up to 15% wt.
The invention is also directed to an Organic Light Emitting Device (OLED) comprising an emissive layer (EML) comprising the above light emitting material. The OLED may optionally comprise a host material (wherein the light emitting material is preferably present as a dopant), wherein said host material is adapted to emit light upon application of a voltage across the device structure.
The OLED generally includes: a glass substrate; a generally transparent anode, such as an Indium Tin Oxide (ITO) anode; a Hole Transport Layer (HTL) an emissive layer (EML) an Electron Transport Layer (ETL) a cathode that is generally metallic, such as an Al layer.
For a hole-conducting emission layer, it may have an excitation-blocking layer, in particular a hole-blocking layer (HBL), between the emission layer and the electron-transport layer. For an electron-conducting emission layer, it may have an excitation-blocking layer, in particular an electron-blocking layer (EBL), between the emission layer and the hole-transport layer. The emissive layer may be equal to the hole transport layer (in which case the exciton blocking layer is near or on the anode) or the electron transport layer (in which case the exciton blocking layer is near or on the cathode).
The emissive layer may be formed from a host material in which the light emitting material resides as a guest. Alternatively, the emissive layer may substantially comprise the luminescent material itself. In the former case, the host material may be a hole transport material selected from the group consisting of substituted triarylamines. Preferably, the emissive layer is formed from a host material in which the light-emitting material resides as a guest. The host material may be an electron transport material selected from the group consisting of: metal quinolinides (metal quinololates) (e.g. aluminum quinolate (Alq)3) Lithium quinolinate (Liq)), oxadiazoles, and triazoles. An example of a host material is 4, 4 '-N, N' -dicarbazole-biphenyl [ "CBP"]It can be characterized by the following formula:
CBP。
optionally, the emissive layer may also comprise a polarising molecule which is present as a dopant in said host material and has a dipole moment which generally affects the wavelength of the emitted light when said luminescent material acting as a dopant emits light.
A layer formed of an electron transporting material is used to transport electrons into an emissive layer comprising the luminescent material and optionally a host material. The electron transport material may be an electron transport matrix selected from the group consisting of: metal quinolinides (e.g. Alq)3And Liq), oxadiazoles, and triazoles. An example of an electron transport material is a material having the formula [ "Alq [ ]3”]Tris- (8-quinolinolato) aluminum of (a):
a layer formed of a hole transport material is used to transport holesInto an emissive layer comprising the luminescent material and optionally a host material. An example of a hole transport material is 4, 4' -bis [ N- (1-naphthyl) -N-phenylamino]Biphenyl [ "alpha-NPD"]。
It is highly preferred to use an exciton blocking layer ("barrier layer") to confine excitons within the light-emitting layer ("light-emitting region"). For a hole transporting host, the blocking layer may be disposed between the emissive layer and the electron transporting layer. An example of a material for such a barrier layer is 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline (also known as bathocuproine (bathocuproine) or "BCP"), which has the following formula:
the OLED preferably has a multilayer structure (as depicted in fig. 1), wherein: wherein 1 is a glass substrate; 2 is an ITO layer; 3 is an HTL layer comprising α -NPD; 4 is an EML comprising CBP as host material and luminescent material as dopant in an amount of about 8% wt relative to the total weight of host plus dopant; 5 is an HBL comprising BCP; 6 is a compound containing Alq3ETL of (2); and 7 is an Al layer cathode.
Examples of the invention
Synthesis of 2-phenyl-4- (2, 5-dimethoxystyryl) pyridinea)tBuOK，DMF，rt
To a mixture of 2-phenyl-4-methylpyridine hydrochloride (1g, 4.9mmol) and 2, 5-dimethoxybenzaldehyde (1.2g, 7.3mmol) in anhydrous DMF (40ml) was added solid t-BuOK (2g, 18 mmol). The resulting mixture was stirred under nitrogen at 80 ℃ overnight. After evaporation of DMFTo which Et was added2O, and the precipitate was filtered off and washed with water. Subjecting the solid to column chromatography (SiO)2，CH2Cl2MeOH, 99/1) to give 0.6g (39%) of the desired compound as a yellow solid.
[ (2-phenyl-4- (2, 5-dimethoxystyryl) pyridine)2IrCl]2Synthesis of (2)b)IrCl3·H2O，EtOCH2CH2OH/H2O，Δ.
1 equivalent of IrCl3·3H2O and 2.5 equivalents of 2-phenyl-4- (2, 5-dimethoxystyryl) pyridine were heated overnight at 110 ℃ under nitrogen in a mixture of 2-ethoxyethanol and water (3/1, v/v). After cooling to room temperature, the precipitate formed is filtered off and successively washed with methanol (and then Et)2O) washing and finally drying to obtain the desired dimer. Because of the low solubility of this compound, it1H-NMR in DMSO-d6Wherein is used as [ C ^ N]2Ir (cl) (dmso) derivatives.
1H-NMR(DMSO-d6，298K，200MHz，δppm)3.80(s，12H)，3.88(s，12H)，5.85(d，J＝7Hz，1H)，6.31(d，J＝7Hz，1H)，6.70-7.90(m，42H)，8.26(s，1H)，8.32(s，1H)，9.45(d，J＝7Hz，1H)，9.75(d，J＝7Hz，1H)。
[ (2-phenyl-4- (2, 5-dimethoxystyryl) pyridine)2Ir (4, 4 '-dicarboxylic acid 2, 2' -bipyridine)]Synthesis of (comparative Complex (VII))Mixing [ (2-phenyl-4- (2, 5-dimethoxystyryl) pyridine)2IrCl]2(122mg, 0.071mmol), 2 '-bipyridine 4, 4' -dicarboxylate (40mg, 0.164mmol), and tetrabutylammonium hydroxide 30 hydrate (261mg, 0.326mmol) in argonUnder CH2Cl2(100ml) was refluxed for 6 hours. The resulting orange solution was concentrated to 5mL and crystallized by slow diffusion of ethanol. The pale yellow precipitate was filtered off and Et2O washed and air dried to give 50mg of the desired complex (yield: 33%).
[ (2-phenyl-4- (2, 5-dimethoxystyryl) pyridine)2Ir (4, 4 '-dicarboxylic acid styryl) -2, 2' -bipyridine][ Complex (III)]Synthesis of (2)
Mixing [ (2-phenyl-4- (2, 5-dimethoxystyryl) pyridine)2IrCl]2(83mg, 0.048mmol), (4, 4 '-p-dicarboxylic styryl) -2, 2' -bipyridine (44mg, 0.095mmol), and tetrabutylammonium hydroxide 30 hydrate (194mg, 0.242mmol) were refluxed in DMF (30ml) under argon for 8 hours. The resultant solution was evaporated to dryness, and the resultant solid was recrystallized from methanol to give 100mg of the desired complex (yield: 80%).
The emission spectrum of complex (III) shows its maximum at about 710nm (corresponding to red emission), with an emission intensity that largely exceeds that of the reference complex (VII) and a red shift of approximately 20nm with respect to the reference complex (VII), thus enabling pure red emission to be obtained.