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Definitions

• This invention relates to metal-containing dendrimers and light-emitting devices containing them.
• a wide range of luminescent low molecular weight metal complexes are known and have been demonstrated as both light emitting and charge transporting materials in organic light emitting devices, in particular light emitting diodes (LEDs) also known as electroluminscent (EL) devices.
• LEDs light emitting diodes
• EL electroluminscent
• Analysis of spin statistics associated with the injection of oppositely charged carriers which pair to form excitons shows that only 25% of the excitons formed in the LED are in the singlet state. Although it has been suggested that the barrier of 25%) for singlet excitons may be exceeded under certain circumstances it is known to be far from 100%. For most organic materials only the singlet states can decay radiatively generating light, the triplet states decay non-radiatively.
• Dendrimers are highly branched macromolecules in which branched dendrons (also called dendrites) are attached to a core.
• the properties of the dendrimers make them ideal for solution processing and allow incorporation of metal complex chromophores, which have been demonstrated to be effective in light emitting devices (LEDs), into a solution processable system.
• the known examples of metal containing dendrimers fall into three classes (i) metal ion at the centre (ii) metal ions on the periphery (iii) metal ions at the branching points
• metal containing dendrimers which have metal ions as part of the branching points and coordinating groups linking the metal ions, (see, e.g., Chem.
• Concentration quenching in the solid state is a common occurrence.
• concentration quenching in the dendrimers with metals ions at the branching points there is a high density of chromophores which makes concentration quenching particularly likely.
• the metal ions in adjacent molecules will be close and again concentration quenching will be a problem.
• the current invention is directed towards dendrimers with metal ions as part of the core.
• metal ion chromophore When the metal ion chromophore is sited at the core of the molecule, it will be relatively isolated from the core chromophores of adjacent molecules, which minimizes possible concentration quenching or triplet-triplet annihilation.
• organometallic dendrimers already disclosed generally do not have conjugated dendrons, and so are unlikely to work well in an electroluminescent device.
• Ln lanthanide
• benzyl ether Frechet-type dendrons. These compounds were shown to give PL emission, but have not been proven in EL devices. Kawa, M.; Frechet, J.M.J. Thin Solid Films,
• the present invention provides a light emitting device which comprises a layer containing a metal ion containing dendrimer and, in particular, an organometallic dendrimer with a metal cation as part of its core, said core (or centre) not comprising a magnesium chelated porphyrin.
• the present invention is particularly directed towards the use of dendrimers containing one or more at least partially conjugated organic dendrons with a metal ion as part of the corel.
• dendrimers form another aspect of the present invention.
• the atoms or groups coordinating/binding to the metal typically form part of the core itself e.g. fac-tris (2-phenylpyridyl) iridum III.
• the dendrimers typically have the formula (I):
• each DENDRITE which may be the same or different, represents an inherently at least partially conjugated dendritic structure comprising aryl and/or heteroaryl groups or nitrogen and, optionally, vinyl or acetylenyl groups connected via sp 2 or sp hybridised carbon atoms of said (hetero)aryl vinyl and acetylenyl groups or via single bonds between N and (hetero)aryl groups, CORE terminating in the single bond which is connected to an sp 2 hybridised (ring) carbon atom of the first (hetero)aryl group or single bond to nitrogen to which more than one at least partly conjugated dendritic branch is attached, said ring carbon or nitrogen atom forming part of said DENDRITE.
• metal ion or "metal cation”, as used herein, describes the charge state the metal would have without any ligands attached (the oxidation state).
• metal cation the charge state the metal would have without any ligands attached (the oxidation state).
• the overall charge of the dendrimer is neutral and the metal-ligand bonding will have more or less covalent character depending on the metal and ligand involved.
• acetylenyl refers to acetylenyl groups that are di-valent
• vinyl refers to vinyl groups that are di- or tri-valent
• aryl refers to aryl groups that are di-, tri- or multivalent.
• the dendrites are conjugated.
• the dendrimers of the invention are preferably luminescent in the solid state.
• the luminescent moiety may be partially or wholly within the core itself.
• the luminescence is preferably from the metal complex.
• Suitable branching points include aryl and heteroaryl, which can be fused, aromatic ring systems and N.
• the links between branching points include bonding combinations such as aryl-aryl, aryl-viriyl-aryl, aryl-acetylenyl-aryl, aryl-aryl'-aryl (where aryl'. may be different from aryl), N-aryl and N-aryl'-N.
• An individual dendron may contain one or more of each type of branching point.
• aryl-vinyl-aryl and aryl-acetylenyl-aryl linkages within the dendron there may be one or more aryl- vinyl or aryl-acetylenyl link between the branching points. Indeed there may be more than one vinyl or acetylenyl or aryl moiety between two aryl groups but preferably no more than three. Further, there can be advantages in using an asymmetric dendrimer i.e. where the dendrons are not all the same.
• dendrimers may be ones having the formula (II):
• CORE represents a metal ion or a group containing a metal ion
• n and m which may be the same or different, each represent an integer of at least 1
• each DENDRITE 1 which may be the same or different when n is greater than 1
• each DENDRITE 2 which may be the same or different when m is greater than 1
• each DENDRITE which may be the same or different, represents an inherently at least partially conjugated dendritic molecular stracture which comprises aryl and/or heteroaryl or N and, optionally, vinyl and/or acetylenyl groups connected via sp 2 or sp hybridized carbon atoms of said (hetero)aryl, vinyl and acetylenyl groups or via single bonds between N and (hetero)aryl groups, and wherein the links between adjacent branching points in said DENDRITE are not all the same, CORE terminating in the single bond which is connected to a sp 2 hybridized (ring) carbon atom of the first
• DENDRITE (hetero)aryl group or N to which more than one dendritic branch is attached, said ring carbon atom or N forming part of said DENDRITE, the CORE and/or DENDRITE being luminescent.
• DENDRITE, DENDRITE 1 and/or DENDRITE 2 does not include N as a branching point and is conjugated. It is to be understood that in formulae I, II and III CORE does not, comprise a magnesium chelated porphyrm.
• conjugated dendrons indicate that they are made up of alternating double and single bonds, apart from the surface groups. However this does not mean that the ⁇ system is fully delocalised. The delocalisation of the ⁇ system is dependent on the regiochemistry of the attachments. In a conjugated dendron any branching nitrogen will be attached to 3 aryl groups.
• the dendrimer may have more than one luminescent moiety.
• the dendrimer incorporates at least two inherently luminescent moieties which moieties may or may not be conjugated with each other, wherein the dendron includes at least one of the said luminescent moieties.
• the luminescent moiety or moieties further from the core of the dendrimer have a larger HOMO-LUMO energy gap than the luminescent moiety or moieties closer to or partly or wholly within the core of the dendrimer.
• the HOMO-LUMO energy gap is substantially the same although the surface groups may change the HOMO-LUMO energy gap of the chromophores at the surface of the dendrite.
• the surface group makes the chromophore at the distal end of the dendrite of lower HOMO-LUMO energy compared to that of the next one in.
• the relative HOMO-LUMO energy gaps of the moieties can be measured by methods known er se using a UN- visible spectrophotometer.
• One of the luminescent moieties may be, or be (partly or wholly) within, the core itself, which will thus preferably have a smaller inherent HOMO-LUMO gap energy than the other luminescent moiety or moieties in the dendron.
• the dendrons themselves may each contain more than one luminescent moiety, in which case those further from the core will again preferably have larger inherent HOMO-LUMO gap energies than those closer to the core.
• the core itself need not be luminescent, although luminescent cores are generally preferred.
• Suitable surface groups for the dendrimers include branched and unbranched alkyl, especially t-butyl, branched and unbranched alkoxy, for example 2-ethylhexyloxy, hydroxy, alkylsilane, carboxy, carbalkoxy, and vinyl.
• a more comprehensive list includes a further-reactable alkene, (meth)acrylate, sulphur-containing, or silicon- containing group; a sulphonyl group; polyether group; a -to-C ⁇ alkyl (preferably t- butyl) group; an amine group; a mono-, di- or amine group; a -COOR group wherein R is hydrogen or C r to-C 15 alkyl; an -OR group wherein R is hydrogen, aryl, or C to-C 15 alkyl or alkenyl; an -O 2 SR group wherein R is C r to-C 15 alkyl or alkenyl; an -SR group wherein R is aryl, or C r to-C ⁇ 5 alkyl or alkenyl; an -SiR 3 group wherein the R groups are the same or different and are hydrogen, C r to-C 15 alkyl or alkenyl, or an -SR' group (R' is ary
• t-butyl and alkoxy groups are used. Different surface groups may be present on different dendrons or different distal groups of a dendron. It is preferred that the dendrimer is solution processable i.e. the surface groups are such that the dendrimer can be dissolved in a solvent.
• the surface group can be chosen such that the dendrimer can be photopatterned.
• a cross-linkable group is present which can be cross-linked upon irradiation or by chemical reaction.
• the surface group comprises a protecting group which can be removed to leave a group which can be cross-linked.
• the surface groups are selected so the dendrimers are soluble in solvents suitable for solution processing.
• the aryl groups within the dendrons can be typically benzene, napthalene, biphenyl (in which case an aryl group is present in the link between adjacent branching points) anthracene, fluorene, pyridine, oxadiazole, triazole, triazine, thiophene and where appropriate substituted variations.
• the aryl groups at the branching points are preferably benzene rings, preferably coupled at ring positions 1, 3 and 5, pyridyl or triazinyl rings.
• the dendrons themselves can contain a, or the, fluorescent chromophore.
• one or more of the dendrons attached to the core can be unconjugated.
• dendrons include ether-type aryl dendrons, for example where benzene rings are connected via a methyleneoxy link.
• generation level is determined by the number of sets of branching points). It may be advantageous for at least one dendron to be of the second, or higher, generation to provide the required solution processing properties.
• the cores typically comprise a metal cation and attached ligands; the metal is typically central in the core and the core is typically luminescent. If it is not luminescent one or more of the dendrons should contain a luminescent group.
• the core comprises a metal cation and attached ligands it is typically a complex of a metal cation and one, two' or more coordinating groups, at least one, and preferably at least two, of the coordinating groups being bound to a dendron. Typically the luminescence of the dendrimer will derive from that complex.
• CORE in formula (I), (II) or (III) above represents a group containing a metal cation
• CORE is typically a complex of a metal cation and two or more coordinating groups, at least one and preferably two or more of the said groups each being bound to a DENDRITE,
• DENDRITE 1 or DENDRITE 2 moiety as defined in formulae (I), (II) or (III), respectively, by the single bond in which CORE in these formulae terminates.
• CORE may be represented as a complex of the following formula (IV):
• each [X-], which are the same or different, is a coordinating group X attached to a single bond in which CORE terminates
• each Y which may be the same or different, is a coordinating group
• q is an integer and r is 0 or an integer, the sum of (a.q) + (b.r) being equal to the number of coordination sites available on M, wherein a is the number of coordination sites on [X-] and b is the number of coordination sites on Y.
• the single bond in the, or each, [X-] moiety being a bond in which CORE terminates, connects to a dendron.
• a dendron Preferably there are at least two dendrons in a dendrimer, in which case q in formula (IV) is an integer of 2 or more.
• the said two or more dendrons typically have the structures represented by DENDRITE, DENDRITE ! and/or DENDRITE 2 as defined in formulae (I) to (III) above.
• the coordinating groups Y when present, are neutral or charged chelated ligands which are not attached to dendrons and which serve to fulfil the coordination requirements of the metal cation.
• Suitable metals include: lanthanide metals: such as cerium, samarium, europium, terbium, dysprosium, thulium, erbium and neodymium, d-block metals, especially those' in rows 2 and 3 i.e. elements 39 to 48 and 72 to
• Suitable substituents Y, for rhenium in particular, include CO and halogen such as chlorine.
• the part of the ligands attached to the metal is preferably a nitrogen- containing heteroaryl, for example pyridine, attached to a (hetero) aryl where aryl can be a fused ring system, for example substituted or unsubstituted phenyl or benzothiophene. It should also be noted that the pyridine can also be substituted.
• Platinum dendrimers and especially platinum dendrimers with a porphyrin core with stilbene-based dendrons attached in the meso position are generally less preferred.
• the light emission can be either fluorescent or . phosphorescent depending on the choice of metal and coordinating groups.
• Suitable coordinating groups for the f-block metals include oxygen or nitrogen donor systems such as carboxylic acids, 1,3-diketonates, hydroxy carboxylic acids, Schiff bases including acyl phenols and iminoacyl groups.
• luminescent lanthanide metal complexes require sensitizing group(s) which have the triplet excited energy level higher than the first excited state of the metal ion. Emission is from an f-f transition of the metal and so the emission colour is determined by the choice of the metal. The sharp emission is generally narrow, resulting in a pure colour emission useful for display applications. Due to the ability to harvest triplet excitons i.e. phosphorescence, the potential device efficiency can be higher than for fluorescent systems.
• Main group metal complexes show ligand based, or charge transfer emission. The emission colour is determined by the choice of ligand as well as the metal.
• a wide range of luminescent low molecular weight metal complexes are known and have been demonstrated in organic light emitting devices [see, e.g., Macromol. Sym. 125 (1997) 1-48, US-A 5,150,006, US-A 6,083,634 and US-A 5,432,014].
• Suitable ligands for di or trivalent metals are shown in Figure 1; they include oxinoids (I) e.g.
• oxygen-nitrogen or oxygen-oxygen donating atoms generally a ring nitrogen atom with a substituent oxygen atom, or a substituent nitrogen atom or oxygen atom with a substituent oxygen atom such as 8 -hydroxy quinolate (I A) and hydroxy quinoxalinol (I B), 10-hydroxybenzo(h)quinolinato (II), benzazoles (III), schiff bases (V), azoindoles (IV), chromone derivatives (VI), 3-hydroxyflavone (VII), and carboxylic acids such as salicylato (VIII) amino carboxylates (IX) and ester carboxylates (X).
• the substituents including the R and X groups are typically halogen, alkyl, alkoxy, haloalkyl, cyano, amino, amido, sulfonyl, carbonyl, aryl or heteroaryl on the (hetero)aromatic rings which may modify the emission colour.
• the R groups in formulae V and X are typically alkyl or aryl.
• the alkyl groups are typically alkyl groups of 1 to 6 carbon atoms, especially 1 to 4 carbon atoms such as methyl, ethyl, propyl and butyl.
• the aryl groups are typically phenyl groups.
• the d-block metals form organometallic complexes with carbon or nitrogen donors such as porphyrin, 2-phenyl-pyridine, 2-thienylpyridine, benzo(h)quinoline, 2- ' phenylbenzoxazole, 2-phenylbenzothiazole or 2-pyridylthianaphthene and iminobenzenes.
• the (hetero)aromatic rings can be substituted for example as for the R and X groups given above.
• the emission of d-block complexes can be either ligand based or due to charge transfer. For the heavy d-block elements, strong spin-orbit coupling allows rapid intersystem crossing and emission from triplet states (phosphorescence) .
• the dendrimers can be built in a convergent or divergent route, but a convergent route is preferred.
• the dendrons are attached to the appropriate ligands and these are subsequently attached to the metal cation to form the dendritic metal complex.
• other non-dendritic ligands can subsequently be attached to said complex.
• a ligand with a suitably reactive functional group can be complexed to the metal ion, and then reacted with appropriately functionalised dendrons. In this latter method, not all ligands have to have the reactive functional groups, and thus this method . allows the attachment of dendrons to some but not all of the ligands complexed to the metal.
• a key property of the dendrons is to impart solution processibility to the metal complex and therefore allow the formation of good quality thin films suitable for use in light-emitting diodes.
• the dendritic metal complexes may be homoleptic or contain more than one type of dendritic ligand, as discussed above.
• the metal complex may contain one or preferably more than one, e.g. 2 or 3, dendritic ligands plus one or more non- dendritic ligands.
• dendritic ligands may be homoleptic or contain more than one type of dendritic ligand, as discussed above.
• the metal complex may contain one or preferably more than one, e.g. 2 or 3, dendritic ligands plus one or more non- dendritic ligands.
• terbium complexes it is possible to have three dendritic ligands terminating in a carboxylate moiety for complexing to the metal plus one or more coligands to satisfy the co-ordination sphere of the metal cation.
• Suitable neutral co-ligands include 1,10-phenanthroline, bathophenanthroline, 2,2'-bipyridyl, benzophenones, pyridine N-oxide and derivatives of these. Also for iridium it is possible to have two dendritic phenylpyridine ligands with the third ligand a non- dendritic phenylpyridine ligand. It is desirable that the number of dendritic ligands is sufficient to provide the required solution processing. In the case of the dendritic metal complexes where all the ligands are different the method of preparation may give rise to a statistical mixture of all complex types. This is not necessarily disadvantageous providing that the optical, electronic, and processing properties are satisfactory.
• the moieties forming the attachment point to metal are all the same or have similar binding constants.
• at least one should desirably be a conjugated dendron.
• the conjugated dendrons can be comprised of a number of different types of branching points.
• the surface groups and dendrites can be varied so the dendrimers are soluble in solvents, such as toluene, THF, water and alcoholic solvents such as methanol, suitable for the solution processing technique of choice. Typically t-butyl and alkoxy groups have been used.
• the choice of dendron and/or surface group can allow the formation of blends with dendrimers (organic or organometallic), polymer or molecular compounds.
• a phosphorescent dendrimer possessing an organometallic core and a dendrimer which possesses the same dendron type but a different core.
• the organometallic dendrimer can be incorporated into a light emitting device as either a homogeneous layer or as a blend with another dendrimer (organic or organometallic), polymer or molecular compound.
• a d- block phosphorescent material being used as a homogenous light emitting layer in an LED.
• a phosphorescent organometallic dendrimer is blended with a fluorescent host the emission spectrum may depend on the driving frequency of electrical pulsing.
• a device can be driven by applying voltage (or current) pulses with a certain duration and period (together describing the driving frequency).
• the emission spectrum may be sensitive to the driving frequency.
• it has been found that it is advantageous to blend the dendrimer with a charge transporting material.
• the presence of a hole-transporting and/or a bipolar material and/or electron transporting material is advantageous.
• the bipolar material should contain carbazole units.
• Another embodiment has one or more of each type of charge transporting material.
• the organometallic dendrimers can be incorporated into an LED in a conventional manner.
• an organic light emitting or electroluminescent device can be formed from a light emitting layer sandwiched between two electrodes, at least one of which must be transparent to the emitted light.
• a device can have a conventional arrangement comprising a transparent substrate layer, a transparent electrode layer; a light emitting layer and a back electrode.
• the standard materials can be used.
• the transparent substrate layer is typically made of glass although other transparent materials such as PET, can be used.
• the anode which is generally transparent, is preferably made from indium tin oxide (ITO) although other similar materials including indium oxide/tin oxide, tin oxide/antimony, zinc oxide/aluminum, gold and platinum can also be used.
• ITO indium tin oxide
• Conducting polymers such as PANT (polyaniline) or PEDOT can also be used.
• the cathode is normally made of a low work function metal or alloy such as Al, Ca, Mg, Li, or MgAl or optionally with an additional layer of LiF.
• a low work function metal or alloy such as Al, Ca, Mg, Li, or MgAl or optionally with an additional layer of LiF.
• other layers may also be present, including a hole transporting material and/or an electron transporting material.
• the dendrimer is a phosphorescent emitter, it has been found that it is particularly beneficial to have a hole-blocking/electron-transporting layer between the light emitting dendrimer layer and the cathode.
• the substrate may be an opaque material such as silicon and the light is emitted through the opposing electrode.
• An advantage of the present invention is that the layer containing the dendrimer can be deposited from solution.
• Conventional solution processing techniques such as spin coating, printing, and dip-coating can be used to deposit the dendrimer layer.
• a solution containing the dendrimer is applied over the transparent electrode layer, the solvent evaporated, and then subsequent layers applied.
• the film thickness is typically lOnm to lOOOnm, preferably less than 200nm, more preferably 30-
• Figure 1 shows coordinating groups for di- or tri-valent metals
• Figure 2 shows the structure of first generation lanthanide dendrimers
• Figure 3 shows a reaction sheme for synthesis of first generation 1-arylpyridine ligands
• Figure 4 shows a reaction scheme for synthesis of tris[2-(Ar)pyridine]iridium (III) complex
• Figure 5 shows the stracture of Fac tris[2-(4'-Gl-phenyl)pyridine]iridium (III) complex
• Figure 6 shows the structure of Fac tris[2-(3'-Gl-phenyl)pyridine]iridiurn (III) complex
• Figure 7 shows the stracture of Pt Gl -porphyrin dendrimer
• Figure 8 shows the stracture of Pt G2-porphyrin dendrimer
• Figure 9 shows structures of Dendrimer A and Dendrimer B
• Figure 10 shows film absorption spectra of neat dendrimer films (A, B and 12);
• Figure 11 shows luminescence of films of dendrimer A and B doped with guest dendrimer 12 in both EL and PL, a) Blend A.12 PL excited at 320 nm ( ), PL excited at 420 nm (o) and EL ( ), b) Blend of B : 12, PL excited at 320 nm ( ), PL excited at 420 nm (o) and EL ( );
• Figure 12 shows EL spectra of host (B), guest (10) and blends under different operating conditions. Neat host emission (a), neat guest emission (b), 200 nm blend device pulsed
• Figure 13 shows the EL spectra of dendrimers 10 and 11;
• Figure 14 shows the PL spectrum of 12 compared to the EL spectrum of dendrimer 13.
• Figure 15 shows a reaction scheme for the synthesis of the (Glppy) 2 btpIr(III) dendrimer.
• Figure 16 shows a reaction scheme for the synthesis of tricarbonyl-chloro- ⁇ 3,5-[4'-(2"- ethylhexyloxy)phenyl]phenyl ⁇ phenanthroline rhenium.
• Figure 17 shows a reaction scheme for the synthesis of the second generation 2- arylpyridine ligands.
• Figure 18 shows a reaction scheme for the synthesis of tris(4- ⁇ 3",6"-di[4"'-(2""- ethylhexyloxy)phenyl]carbaxolyl ⁇ phenyl)amine.
• rert-butyl lithium (1.7 M, 66.0 cm 3 , 112 mmol) was added carefully to a cold (dry- ice/acetone bath) solution of GO-Br Rl (20.0 g, 70.1 mmol) in 300 cm 3 of anhydrous THF under an argon atmosphere.
• the mixture was stirred at -78 °C for 1 h and then tri- methyl borate (57.2 cm 3 , 421 mmol) was added slowly to the cold mixture.
• the reaction was stirred at -78 °C for 2 h before being removed from the dry-ice/acetone bath.
• the mixture was then stirred at room temperature for further 2.5 h before being quenched with 3 M HCl (aq) (30 cm 3 ). The two layers were separated.
• either compound 4A or 4B can be used in the reaction to form the next generation dendrons.
• 4k or 4B being a dimer the number of protons in the ⁇ NMR should be considered as a ratio.
• C 105 H 135 TbO 12 requires C, 72.1; H, 7.8 %; for C 105 H 137 TbO 13 requires C, 71.4; H, 7.8 %); ⁇ max /nm (thin film) 270, and 330.
• Gl-COO-Tb 1,10-phenanthroline; ⁇ nm (thin film) 270, and 326;
• H NMR is similar to the reported by M. van der Sluis, V. Beverwijk, A. Termaten, F. Bickelhaupt, H. Kooijman, A. L. Spek, Organometallics, 1999, 18, 1402- 11407.
• the brown yellow mixture was purified by column chromatography over silica gel with DCM-ethyl acetate-light petroleum (0: 1 : 10 to 1 : 1 : 10) as eluent to give 200 mg (49% for two steps referring to IrCl 3 3H 2 O) of 10 as an orange yellow solid;
• the brown yellow mixture was purified on silica gel column with eluent of DCM-ethyl acetate-light petroleum (0 : 1 : 10 to 1 : 1 : 10) as eluent to give 95 mg (39% for two steps referring to IrCl 3 -3H 2 O) of orange yellow solid as 11 ; TGA (5%) 400 °C; (Found: C, 76.7; H, 7.2, N, 2.1.
• Impure fractions were combined and further purified by column chromatography with DCM-light petroleum (1 :4) as eluent.
• the combined material was recrystallised from a DCM-MeOH mixture to give 42.0 mg (77 %) of 12 as a brick-red solid; mp > 295 °C (decomp.) (Found: C, 81.6; H, 7.9; N, 2.1.
• LEDs were fabricated by the following method. Patterned indium tin oxide (ITO) substrates were cleaned with acetone and 2-propanol in an ultrasound bath. A hole injecting layer of PEDOT (Bayer) was then spin-coated from water at 1000 rpm onto the cleaned ITO substrate and dried at 80 °C on a hot plate for 5 minutes. Dendrimer solutions were subsequently spin-coated onto the PEDOT layer at speeds of 800 rpm to give films typically 100 nm thick, and an aluminium cathode was then evaporated giving devices with active areas of 2 mm 2 .
• PEDOT hole injecting layer of PEDOT
• Dendrimer solutions were subsequently spin-coated onto the PEDOT layer at speeds of 800 rpm to give films typically 100 nm thick, and an aluminium cathode was then evaporated giving devices with active areas of 2 mm 2 .
• Device testing was performed in vacuum using a Keithley source measure unit for dc operation as well as a Hewlett Packard pulse generator (rise time ⁇ 10 ns) for pulsed operation.
• the RC value of the devices defining the time required for charging the LED, was estimated to be in the order of 100 ns and driving conditions were chosen appropriately.
• the emission spectra were measured using an ISA Spectrum One CCD spectrometer.
• PL and PL excitation (PLE) spectra were obtained on an ISA Fluoromax fluorimeter. All emission spectra were corrected for the instrument response. As a crosscheck, PL spectra were also recorded on the CCD and found to be identical to those obtained on the fluorimeter.
• Example 14 Device Results for Gl-Pt-porphyrin 12 Films and LED devices were made using 12 blended with either dendrimer A or dendrimer B (fig 9). Films of 12 / host blends were formed by spin-coating THF solutions of the two dendrimers (10 mg/ml) in a w/w ratio of host to guest of 10:1 corresponding to a molar ratio of approximately 3:1. No phase separation was observed with these spin-coated films and their absorption was found to be a sum of the components. The films of the blends appeared to be of comparable quality to films prepared of the individual materials
• Dendrimer B was obtained as follows:
• Tris[(4'-formylstyryl)phenyl]benzene (51.5 mg, 0.07 mmol), Reference example 7A (759 mg, 0.30 mmol) in dry tetrahydrofuran (20 mL) heated at reflux. The solution was heated at reflux for 18 h and then allowed to cool. Water (50 mL) and dichloromethane (50 mL) were added and the organic layer separated. The aqueous layer was extracted with dichloromethane (50 mL) and then brine (50 mL) was added to the aqueous layer before a final extraction with dichloromethane (50 mL).
• the absorption spectra of the materials A, B and 12 are shown in Fig. 10.
• the stilbene moieties are found to give rise to an absorption peak at 320 nm.
• the core gives rise to an additional absorption at 420 nm, whilst in B the core gives rise to an absorption at 370 nm and for 12 absorption bands are observed at 420 nm, 514 nm and 544 nm, corresponding to the Soret and Q-bands of the Gl-Pt-porphyrin 12.
• Figure 11 shows PL and EL spectra of blends of the materials under continuous excitation.
• the emission of A appears green and peaks at 495 nm
• the emission of B is in the blue and peaks at 470nm
• the guest dendrimer 12 emits in the red to near IR with peaks at 662 nm and 737 nm.
• the emission of the host dendrimers A and B is attributed to fluorescence, whereas the emission of the guest 12 is believed to be due to phosphorescence.
• the host PL emission is much stronger than the guest PL emission.
• Devices containing the novel Ir dendrimer 10 were fabricated using the standard method described above. Devices were made with a neat Ir dendrimer layer and with a layer containing the Ir dendrimer blended with a mixture of dendrimer B and PBD (2-(4- biphenylyl)-5-(4-tert-butylphenyl)-l,3,4-oxadiazole)). The structures of the two types of device were:
• ITO / PEDOT / dendrimer B 10 : PBD / Al where in the blend the ratio of dendrimer B: 10 : PBD is 1 : 0.1 : 0.4 by weight, and two devices were formed one with a blended layer thickness of 150nm and the other with a blended layer 200 nm thick .
• the emission spectra of the neat materials as well as the blends are shown in Fig. 12.
• the iridium dendrimer (10) exhibits broad EL in the green (peak at 535 nm with features at 577 nm and 623 nm).
• the benzene cored dendrimer (B) emits in the blue (peak at 460 nm).
• the EL spectrum of the blend is not a mere superposition of the guest and host.
• the emission band of the host cannot be identified, yet there is significant unstructured emission below the band of the iridium dendrimer. Most significantly, a new emission band is observed at 660 nm, which forms the emission maximum in some cases. This band is not immediately visible in neat 10 devices.
• the EL spectra of the dendrimers 11 and 10 are shown in Figure 13.
• the spectrum of 11 is slightly broader and exhibits less vibronic stracture.
• the emission peaks at 518 nm, whereas the emission for 10 peaks at 532 nm and has a vibronic feature at 569 nm.
• the device consisting of 10 was more efficient than that containing 11.
• the brown yellow mixture was purified by column chromatography over silica gel with DCM- ethyl acetate-light petroleum (0 : 1 : 10 to 1 : 1 : 10) as eluent to give 200 mg (49% for two steps referring to IrCl 3 -3H 2 O) of 10 as an orange yellow solid; TGA (5%) 410 °C; (Found: C, 76.8; H, 7.5, N, 2.0.
• Example 19 and 20, leading to the formation of a Re dendrimer, are illustrated in Figure 16.
• Tricarbonyl-chloro- ⁇ 3.5-r4'-(2"-ethylhexyloxy)phenyl]phenyl>phenanthroline rhenium Amixture ofthe phenanthroline ligand 31 (126 mg, 0.190 mmol) and pentacarbonylchloro rhenium (681 mg, 0.190 mmol) in 10 cm 3 of toluene was heated at reflux for 1.5 h. The mixture became yellow then orange. The reaction was allowed to cool to ambient temperature and the solvent was removed under reduce pressure.
• ert-butyl lithium (1.7 M, 36.6 cm 3 , 62.1 mmol) was added to a cold (dry-ice/acetone bath) solution of 6 (8.10 g, 34.6 mmol) in 130 cm 3 of anhydrous THF under an argon atmosphere.
• the mixture was stirred at -78 °C for 2 h and then 2-isopropoxy-4,4,5,5-tetramethyl-l,3,2- dioxaborolane (9 cm 3 ) was added rapidly to the cold mixture.
• the reaction was stirred at -78 °C for 2 h and the dry-ice/acetone bath was removed.
• the mixture was then stirred at room temperature for further 20 h before being quenched with H 2 O (30 cm 3 ) .
• the two layers were separated.
• the aqueous layer was extracted with ether (3 x 40 cm 3 )* .
• the organic layer and the ether extracts were combined and dried over anhydrous sodium sulfate and the solvents were
• the mixture was diluted with water (4 cm 3 ) and ether (10 cm 3 ). The two layers were separated. The aqueous layer was extracted with ether (3 x 10 cm 3 ). The organic layer and the ether extracts were combined, washed with brine (1 x 30 cm 3 ), dried (Na 2 SO 4 ) and the solvents were removed to leave a light yellow oil.
• the oil was purified by column chromatography over silica gel using ethyl acetate-light petroleum (0: 1 to 1 :30) and then DCM-light petroleum (1 :20 to 1 : 10) as eluent to give 2.97 g (73%) of 25 as a white foam; (Found: C, 84.8; H, 8.7, N, 1.1.
• the brown yellow mixture was dissolved in 50 cm 3 of DCM and then concentrated to about 10 cm 3 before being purified on silica gel column with eluent of DCM-light petroleum (1 :20) as eluent to give >750 mg (>40% for two steps referring to IrCl 3 -3H 2 O) of 27 as a yellow solid; TGA (5 o /o) 400 °C; (Found: C, 80.7; H, 8.0, N, 1.1.
• step 6 typically a solution concentration of 20 mg/ml was used to achieve a film thickness of 100-120 nm, and a concentration of 5 mg/ml was used to achieve aa film thickness of 45-50 nm.
• the solvent was usually ChCl 3 and the spin rate 2000 rpm for 60 sec.
• TCTA is tris(carbazolyl)triphenylamine
• EHP-TCTA was prepared as in Example Z.
• CBP is 4, 4'-N,N'-dicarbazole-biphenyl.
• BCP is 2, 9-dimethl-4, 7-diphenyl- 1,10-phenanthroline.
• TPBI is 2, 2', 2" -(l,3,5-phenylene(tris[l-phenyl-lH-benzimidazole].
• Devices for 1 If and 27f were prepared in the following manner. ITO substrates were patterned by photolithographic methods, cut into squares 1" x 1" and cleaned sequentially in detergent, NH 3 : H 2 O 2 , 1 : 1 and deionized water ' for 1 hour in an ultrasonic bath before drying in a stream of dry nitrogen.
• the dry substrates were transferred into a dry N 2 atmosphere glove-box where they were subjected to O 2 plasma treatment (Emitech KI 050X plasma unit) at 60 W for 4 mins. Films of the dendrimer doped CBP or TCTA were deposited on the substrates by spin-coating inside the glove-box. Spin- coating was performed using solutions in CHC1 3 (CBP and TCTA) or toluene (TCTA) at a concentration of 5 mg/ml with spin rate 2000 rpm for 1 min. The dried spin-coated films were then transferred to the chamber of a vacuum evaporator without exposure to air for vacuum-deposition of subsequent organic charge transport layers and/or metal electrodes at low pressure ( ⁇ 10" 6 torr). The thickness of the evaporated layers was monitored by an in-situ quartz crystal microbalance and material was deposited at a rate of 0.1 -0.5 nm/s.
• Devices based on 11 and 27 emit green light with C.I.E. co-ordinates around (0.31 , 0.63) whilst devices based on 111 emit red light with C.I.E. co-ordinates around (0.64, 0.35).
• Tris(4- ⁇ 3".6"-Dir4'"-(2""-ethvhexyloxyrohenyl]carbazolvUphenvnamine Tris(dibenzylideneacetone)di-palladium(0) [Pd 2 (dba) 3 ] 14mg, 0.015 mmol) andtri-tert- butylphosphine (10% in hexane, 0.01 cm 3 ) were added to a degassed (Schlenk line, evactuated and back-filled with argon) mixture of carbazolyl compound (3,6-di[4'-(2 M - ethylhexyloxy)phenyl] carbazole; DEHP-Car) (860 mg, 1.49 mmol), tris(4- bromophenyl)amine (200 mg, 0.415 mmol), sodium tert-butoxide (240 mg, 2.49 mmol), and distilled toluene (1.0 cm 3
• DEHP-Car was prepared as follows:
• Example 26 This example of a blue emitting Ir dendrimer is illustrated in figure 19 and reference numbers apply accordingly.
• the PL data for this dendrimer are as follows:
• a thin film of a blend of compound 8 and CBP (20 wt% of compound 8) was prepared

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