WO2004016708A1

WO2004016708A1 - Electroluminescent materials and devices

Info

Publication number: WO2004016708A1
Application number: PCT/GB2003/003610
Authority: WO
Inventors: Poopathy Kathirgamanathan; Subramaniam Ganeshamurugan; Alexander Kit Lay; Chamilla Wickramasinghe; Gnanamoly Paramaswara
Original assignee: Elam-T Limited
Priority date: 2002-08-19
Filing date: 2003-08-19
Publication date: 2004-02-26
Also published as: GB2407324B; GB0219253D0; GB0503352D0; AU2003263289A1; GB2407324A

Abstract

An electroluminescent β diketone incorporating a polymer.

Description

Electroluminescent Materials and Devices

The present invention relates to electroluminescent materials and- to electroVuminescent devices.

Materials which emit light when an electric current is passed through them are well known and used in a wide range of display applications. Liquid crystal devices and devices which are based on inorganic semiconductor systems are widely -used; however these suffer from the disadvantages of high energy consumption, high* cost of man facture, low quantum efficiency and the inability to make flat panel displays.

Organic polymers have been proposed as useful in electroluminescent devices, ^"but it is not possible to obtain pure colours; they are expensive to make and have a relatively low efficiency.

Another compound which has been proposed is aJuminium quinolate, but; this requires dopants to be used to obtain a range of colours and has a relatively low efficiency.

Typical electroluminescent devices which are commonly referred to as optical light emitting diodes (OLEDS) comprise an anode, normally of an electrically light transmitting material, a layer of a hole transmitting material, a layer of the electroluminescent material, a layer of an electron transmitting material and a metal cathode.

Patent application O98/58O37 describes a range of lanthanide complexes which can be used in electroluminescent devices which have improved properties and give better results. Patent Applications PCT/GB98/01773, PCT/GB99/03619, PCT/GB99/O4030, PCT/GB99/04024, PCT/GB99/04028, PCT/GBOO/00268 describe electrolumin.escent complexes, structures and devices using rare earth chelates. US Patent 5128587 discloses an electroluminescent device which consists of an organometallic complex of rare earth elements of the lanthanide series sandwiched between a transparent electrode of high work function and a second electrode of low work function with a hole conducting layer interposed between the electroluminescent layer and the transparent high work function electrode and an electron conducting layer interposed between the electroluminescent layer and the electron injecting low Λvork function anode. The hole conducting layer and the electron conducting layer are required to improve the working and the efficiency of the device. The hole transporting layer serves to transport holes and to block the electrons, thus preventing electrons from moving into the electrode without recombining with holes. The recombination of ca riers therefore mainly takes place in the emitter layer.

We have now invented, electroluminescent compounds and devices incorporating them.

According to the invention there is provided- electroluminescent compounds of formula (Lα)_nM where M is a transition metal, rare earth, lanthanide or an actinide, Lα is a β diketone and n is the valence state of M and Lp is a neutral ligand and in which at least one of Lα and Lp is substituted by a polymer, an oligomer or a endrimer.

Preferred electroluminescent compounds which can be used in the present invention are of formula

(L >M< In the polymer, oligomer or dendrimer substituted β diketone the substituents group can be directly linked to the diketone or can be linked through one or more - CH₂ groups i.e.

Polymer

or or

(I) (II)

Polym

or through phenyl groups e.g.

Polymer

CIHc) (Hid) where "polymer" can be a polymer, an oligomer or a dendrimer-, (there can be one or two substituted phenyl groups as well as three as shown in (ffic)) e.g.

Polymer Polymer

(IHe) (Illf)

and where R. is selected from hydrogen, and substituted and unsubstituted hydrocarbyl groups such as substituted and unsubstituted aliphatic groups, substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or th ophenyl groups; X is Se, S or O, Y is R or hydrogen, substituted or unsubstituted hydrocarbyl groups, such as substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorine, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups or nitrile.

R and Y can also form substituted and unsubstituted fused aroroatic, heterocyclic and polycyclic ring structures and can be copolymerisable with a monomer, e.g. styrene "polymer" is an organic polymer and can be linked to R and/or Y to form a ring structure "polymer" and which also includes oligomers and den lrimers, e.g. in which there are four or more repeating units forming a polymer drain, m is an integer preferably from 1 to 5 and Rl and R2 are the same or different R. moieties.

Examples of E. include aliphatic, aromatic and heterocyclic alkoxy, aryloxy and carboxy groups, substituted and substituted phenyl, fluorophenyl, biphenyl, phenanthrene, anthracene, naphthyl and. fluorene groups alkyl groups such as t-butyl, heterocyclic groups such as carbazole. Examples of polymers which can be used in the present invention include substituted and unsubstituted polyole ϊns such as polyethylene, polypropylene, polybutylene, polyvinyl chlorides etc. and their copolymers, substituted and unsubstituted polymers such as polystyrene and their copolymers, polyesters such as polyacrylates, polyurethanes etc. polyethers, polyamines, polysulphonates; examples of oligomers are shown in fig. 19 of the drawings where 2 <n< 20 and examples of dendrimers are shown in figs. 20 and 21 of^* the drawings; the groups R and Y can also be poLymers.

A class of polymers, oligomers or dendrimers which can be used with the present invention are electroluminescent light emitting organic polymers, oligomers or dendrimers. Examples of electroluminescent light emitting organic polymers are the conjugated organic polymers such as any of the conjugated polymers disclosed or referred to in US 5807627, PCT/WO90/13148 and PCT/WO92/03490.

The preferred conjugated polymers are poly <j phenylenevinylene)-PPN and copolymers including PPV. Other preferred polymers are poly(2,5 dialkoxyplienylene vinylene) such as poly (2-nιethoxy-5-(2-methoxyperιtyloxy-l,4-phenylene vinylene), poly(2-methoxypentyloxy)- ,4-phenylenevinylene), poly(2-methoxy-5-(2- dodecyloxy- 1,4-phenylenevinylene) and other poly(2,5 dialkoxyphenylenevinylenes) with at least one of the alkoxy groups being a long chain solubilising alkox y group, poly fluorenes and oligofluorenes, polypherrylenes and oligophenylenes, polyanthracenes and oligo anthracenes, polythiophenes and oligothiophenes.

In PPN the phenylene ring may optionally carry one) or more substituents, e.g. each independently selected from alkyl, preferably methyl, alkoxy, preferably methoxy or ethoxy.

Any poly(arylenevinylene) including substituted derivatives thereof can be used and the phenylene ring in poly(jp-phenylenevinylene) m-ay be replaced by a fused ring system such as an anthracene or naphthlyene ring and the number of vinylene groups in each polyphenylenevinylene moiety can be increased, e.g. up to 7 or higher.

The conjugated polymers can be made by the methods disclosed in US 5807627, PCT/WO90/13148 and PCT/WO92/03490.

The ligands Lα can be the same or different and there can be a plurality of ligands Lp which can be the same or different.

For example (Lι)(L₂)(L₃)(L..)M (Lp) where Λ is a rare earth, transition metal, lanthanide or an actinide and (Lι)(L )(L₃)(L... ) are the same or different organic complexes and (Lp) is a neutral ligand. The total charge of the ligands (Lι)(L )(L₃)(L..) is equal to the valence state of the metal M. Where there are 3 groups Lα which corresponds to the III valence state of M the complex has the formula (L (L₂)(L₃)M (Lp) and the different groups (L_Ϊ)(L₂)(L₃) may be the same or different.

Lp can be monodentate, bidentate or porydenxate and there can be one or more ligands Lp.

Preferably M is metal ion having an unfilled inner shell and the preferred metals are selected from Sm(ffl), Eu(II), Eu(III), Tb(III), Dy(III), Yb(ffl), Lu(III), Gd (HI), U(III), U(NI)O₂, Tm(III), Th(IV), Ce (III), Ce(IN), Pr(III), Νd(Hι), Pm(iπ), Dy<Tfl), Ho(IH), Er(III); when M is a transition metal the metal is preferably manganese, iron, ruthenium, osmium, cobalt, nickel, palladiuum(II), palladium(IN), platinum(Iι), platinum(IN), cadmium, chromium, titanium, vanadium, zirconium, tantalum, molybdenum, rhodium, iridium, titanium, niobium, scandium, yttrium. Further electroluminescent compounds which can be used in the present invention are of general formula (Lα)_qMιM₂ where i is the same as M above, M₂ is a non rare earth metal, Lα is a as above and q is the combined valence state of Mi and M₂. The complex can also comprise one or more neutral ligands Lp so th_e complex has the general formula (Lα)_q Mi M₂ (Lp), where Lp is as above. The metal M₂ can be any metal which is not a rare earth, transition metal, lanthanide or an actinide examples of metals which can be used include lithium, sodium, potassium, rubidium, caesium, beryllium, magnesium, calcium, strontium, barium, copper (I), copper (II), silver, gold, zinc, cadmium, boron, aluminium, gallium, indium, germanium, tin (II), tin (IN), antimony (II), antimony (IN), lead (TJ), lead (IN) and metals of the first, second and third groups of transition metals in different valence states e.g. manganese, iron, ruthenium, osmium, cobalt, nickel, palladium(II), palladiumCTV), platinum(II), platinum(IV), cadmium, chromium, titanium, vanadium, zirconium, tantulum, molybdenum, rhodium, iridium, titanium, mobium, scandium, yttrium.

For example (Lι)(L₂)(L₃)(L..)M (Lp) where M is a rare eartn, transition metal, lanthanide or an actinide and (Lι)(L₂)(L₃)(L...) and (Lp) are the same or different organic complex.es.

Some of the different groups Lα may also be the same or different charged groups such as carboxylate groups so that the group Li can be as defined above and the groups L₂, L₃... can be charged groups such as

(IN) where R is as defined above or the groups Li, L can be as defmecl above and L₃... etc. are other charged groups. R can also be

where X is , S, Se or H.

(V)

A preferred moiety R is trifluoromethyl CF₃ and examples of such diketones are, banzoyltrifluoroacetone, p-chlorobenzoyltrifluoroacetone, p-bromotrifluoroacetone, p-phenyltrifluoroacetone, 1 -naphthoyltrifluoroacetone, 2-n,aphthoyltrifluoroacetone, 2-phenathoyltrifluoroacetone, 3-phenanthoyltriflu-oroacetone, 9- anthroyltriflnoroacetonetrifluoroacetone, cinnamoyltrifluoroacetone, and 2- thenoyltrifluoroacetone.

The different groups Lα may be the same or different ligands of formulae

(VI)

where X is O, S, or Se and R_t and R₂ are the same or different and can be a polymer or can be as R as above. The different groups Lα may be the same or different quinolate derivatives such as

(VII) (VIII) where R is hydrocarbyl, aliphatic, aromatic or heterocyclic carboxy, aryloxy, hydroxy or alkoxy or a polymer, e.g. the 8 hydroxy quinolate derivatives or

Cix) (X) where R, Ri, and R₂ are as above or are H or F or a polymer, e.g. Ri and R₂ are alkyl or alkoxy groups

(XI) (XII) As stated above the different groups Lα may also be -the same or different carboxylate groups, e.g.

(XIII) where R₅ is a substituted or unsubstituted aromatic, polycyclic or heterocyclic ring a polypyridyl group, or a polymer, R₅ can also be a. 2-efhyl hexyl group so L_n is 2- ethylhexanoate or R₅ can be a chair structure so that L_π is 2-acetyl cyclohexcanoate or Lα can be

R (XIN) where R is as above, e.g. alkyl, allenyl, amino or a fused ring such as a cyclic or polycyclic ring or a polymer.

The different groups Lα may also be

(XV) (XVI)

M

(XVII) Λvhere R, Ri R₂ and R.₃ are as above or one or more of which is an oligomer or a dendrimer.

The groups Lp can be selected from

Ph Ph

O N Ph

Ph Ph (XVIII) where each Ph which can be the same or different and can be a phenyl (OPNP) or a substituted phenyl group, other substituted or unsubstituted aromatic group, a substituted or unsubstituted heterocyclic or polycyclic group, a substituted or unsubstituted fused aromatic group such as a naphthyl, anthracene, phenanthrene or pyrene group. The substituents can be for example an alkyl, aralkyl, alkoxy, aromatic, heterocyclic, polycyclic group, halogen such as fluorine, cyano, amino. Substituted amino etc. a polymer an oligomer or a dendrimer. Examples are given in figs. 1 and 2 of the drawings where R, Ri, R₂, R₃ and R4 can be the same or different and are selected from hydrogen, hydrocarbyl groups, substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups; R, Ri, R _; R₃ and i can also form substituted and unsubstituted fused aromatic, heterocyclic and polycyclic ring structures and can be copolymerisable with a monomer e.g. styrene. R, Ri, R₂, R3 and Rj can also be unsaturated alkylene groups such as vinyl groups or groups

-CH '2- ^:C ~H" '2, R where R is as above or is a polymer an oligomer or a dendrimer.

Examples in which the phenyl group in (XVIII) is substituted by a polymer, an oligomer or a dendrimer are shown in Fig. 17a of the drawings.

L_p can also be compounds of formulae

CXVIV) (XX) (XXI) where Ri, R₂ arid R₃ can be a polymer an oligomer or a dendrimer or as referred to above, for example bathophen shown in fig. 3 of the drawings in which R is as above or

where Ri, R₂ and R₃ are as referred to above or can be a polymer an oligomer or a dendrimer, examples of which are shown in figs. 17b, 17c, 17d 17e and in figs. 18a, 18b and 18c of the drawings where ''polymer" can be an oligomer or dendrimer . In fig. 18b one or more of R R _; R_3> R , R₅, and Rδ can be a polymer oligomer or dendrimer.

L_p can also be

^>h

Ph Ph _or Ph Ph

(XXIV) (XXV) where Ph is as above or can be substituted with a polymer an oligomer or a_ dendrimer.

Other examples of L_p chelates are as shown in figs. 4 and fluorene and fluorene derivatives, e.g. a shown in figs. 5 and compounds of formulae as shown in figs. 6 t 8. Polymer substituted chelates are shown in figs. 17 and 18 o f the drawings.

Specific examples of Lα and Lp are tripyridyl and TMHD, and TMHD complexes, α, α', α" tripyridyl, crown ethers, cyclans, cryptans phthalocyanans, porphoryins- ethylene diamine tetramine (EDTA), DCTA, DTPA and T HA. Where TMHD is 2,2,6,6-tetramethyl-3,5-heptanedionato and OPNP is diphenylphosphonimide triphenyl phosphorane. The formulae of the polyamines are s iown in fig. 11.

The invention also provides an electroluminescent device wliich comprises (i) a first electrode, (ii) a layer of a rare earth chelate electroluminescent compound ass described above and (iii) a second electrode. The first electrode can function as the anode and the second electrode can function as the cathode and preferably there is> a layer of a hole transporting material between tlie anode and the layer of the electroluminescent compound.

The hole transporting material can be any of the hole transporting materials used in electroluminescent devices.

The hole transporting material can be an amine complex such as poly (vinylcarbazole), N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1' -biphenyl -4,4'- diamine (TPD), an unsubstituted. or substituted polymer of an amino substituted aromatic compound, a polyarxiline, substituted polyanilines, polythiophenes, substituted polythiophenes, polysilanes etc. Examples of polyanilines are polymers of

where R. is in the ortho - or meta-position and is hydrogen., Cl-18 alkyl, Cl-6 alkoxy, amino, chloro, bromo, hydroxy or the group

where R. is alky or aryl and R' is hydrogen, Cl-6 alkyl or aryl with at least one otlier monomer of formula I above. Or the hole transporting material can be a polyaniline; polyanilines which can be used in the present invention have the general formula

(XXVII) where p is from 1 to 10 and n is from 1 to 20, R is as defined above and X is an anion, preferably selected from Cl, Br, SO₄, BF₄, PF₆, H₂PO₃, H₂PO₄, arylsulphonate, arenedicarboxylate, polystyrer±esulphonate, polyacrylate alkysvxlphonate, vinylsulphonate, vinylbenzene sulplnonate, cellulose sulphonate, campbor sulphonates, cellulose sulphate or a perfluorinated polyanion.

Examples of arylsulphonates are p-toluenesulphonate, benzenesulphonate, 9,10- anthraquinone-sulphonate and anthracenesulphonate; an example of an arenedicarboxylate is phthalate and an example of arenecarboxylate is benzoate.

We have found that protonated polymers of the unsubstituted or substituted polymer of an amino substituted aromatic compound such as a polyaniline are difficult to evaporate or cannot be evaporated, however we have surprisingly found that if the unsubstituted or substituted polymer of an amino substituted aromatic compotmnd is deprotonated then it can be easily evaporated i.e. the polymer is evaporable.

Preferably evaporable deprotonated polymers of unsubstituted or substituted polymer of an amino substituted aromatic compound are used. The de-proto>nated unsubstituted or substituted polymer of an amino substituted aromatic compound can be formed by deprotonating the polymer by treatment with an alkali such as ammonium hydroxide or an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide.

The degree of protonation can be controlled by forming a protonated polyaniline and de-protonating. Methods of preparing polyanilines are described in the article by A. G- MacDiarmid and A. F. Epstein, Faraday Discussions, Chem Soc.88 P 19 1989.

The conductivity of the polyaniline is dependent on the degree of protonation with the maximum conductivity being when the degree of protonation is between 40 and 60%, e.g. about 50% for example .

Preferably the polymer is substantially fully deprotonated.

A. polyaniline can be formed of octamer units, i.e. p is four, e.g.

^"^ ^⁼^ ^^{=/^ ~~} ^"^ ^⁼^ ^⁼^

The polyanilines can have conductivities of the order of 1 x 10^"1 Sie en cm^"1 or higher.

The aromatic rings can be unsubstituted or substituted, e.g. by a Cl to 20 alkyl group such as ethyl.

The polyaniline can be a copolymer of aniline and preferred copolymers are the copolymers of aniline with o-anisidine, m-sulphanilic acid or o-aminophenol, or o- toluidine with o-aminophenol, o-ethylaniline, o-phenylene diamine or with amino anthracenes.

Other polymers of an amino substituted aromatic compound which can be used include substituted or unsubstituted polyaminonapthalenes, polyaminoanthracenes, polyaminophenanthrenes, etc. and polymers of any other condensed polyaromatic compound. Polyamino anthracenes and methods of making them are disclosed in US Patent 6,153,726. The aromatic rings can be unsubstituted or substituted, e.g. by a group R as defined above.

Other hole transporting materials are conjugated polymer and t ie conjugated polymers which can be used can be any of the conjugated polymers disclosed or referred to in US 5807627, PCT/WO90/13148 and PCT/WO92/03490.

The preferred conjxxgated polymers are poly (p-phenylenevinylene)-PPV and copolymers including PPV. Other preferred polymers are poly(2,5 diaTJ oxyphenylene vinylene) such as poly (2-methoxy-5-(2-methoxypentyloxy-l,4-phenylene vinylene), poly(2-methoxypentyloxy)-l,4-phenylenevinyLene), poly(2— methoxy-5-(2- dodecyloxy- 1,4-phenylenevinylene) and other poly(2,5 dialkoxyphenylenevinylenes) with at least one of the alkoxy groups being a long chain solubilisingς alkoxy group, poly fluorenes and oligofluorenes, polyphenylenes and oLigophenylenes, polyanthracenes and oligo anthracenes, ploythiophenes and oligothiopraenes.

In PPV the phenylene ring may optionally carry one or more substituents, e.g. each independently selected from alkyl, preferably methyl, alkoxy, preferably methoxy or ethoxy.

Any poly(arylenevinylene) including substituted derivatives thereof can be used and the phenylene ring in pofy(p-phenylenevmylene) may be replaced h>y a fused ring system such as an anthracene or a naphthlyene ring and the number of vinylene groups in each polyphenylenevinylene moiety can be increased, e.g. u to 7 or higher.

The conjugated polymers can be made by the methods disclosed in US 5807627, PCT/WO90/13148 and PCT/WO92/03490. The thickness of the hole transporting layer is preferably 20nm to 2O0nm.

The polymers of an amino substituted aromatic compound sucli as polyanilines referred to above can also be used as buffer layers with or in conjunction with other hole transporting materials.

The structural formulae of some other hole transporting materials are shown in Figures 12, 13, 14, 15 and 16 of the drawings, where R_1; R₂ and R₃ can be the same or different and are selected from hydrogen, and substituted and unsubstituted hydrocarbyl groups such as substituted and unsubstituted aliphatic groups, substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups; R_1; R₂ and R₃ can also form substituted and unsubstituted fused aromatic, heterocyclic and polycyclic ring structures and can be copolymerisable with a monomer, e.g. styrene. X is Se, S or O, Y can be hydrogen, substituted or unsubstituted hydrocarbyl groups, such as substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorine, fluorocarbons sucli as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups or nitrile.

Examples of Ri and/or R₂ and/or R₃ include aliphatic, aromatic and heterocyclic alkoxy, aryloxy and carboxy groups, substituted and substituted phenyl, fluorophenyl, biphenyl, phenanthrene, anthracene, naphthyl and fluorene groups alkyl groups such as t-butyl, heterocyclic groups such as carbazole.

Optionally there is a layer of an electron injecting material between the cathode and the electroluminescent material layer, the electron injecting material is a material which will transport electrons when an electric current is passed through electron injecting materials include a metal complex such as a metal quinolate, e.g. an aluminium quinolate, lithium quinolate, Mx(T)BM)n where Mx is a metal and DBM is dibenzoyl methane and n is the valency of Mx, e.g Mx is chromium, a cyano anthracene such as 9,10 dicyano anthracene, cyano substituted aromatic compounds, tetracyanoquinidodimethane a polystyrene sulphonate or a compound with the structural formulae shown in figures 9 or 10 of the drawings in which the phenyl rings can be substituted with substituents R as defined above. Instead of being a separate layer the electron injecting material can be mixed with the electroluminescent material and co-deposited with it.

Optionally the hole transporting material can be mixed with the electroluminescent material and co-deposited with it.

The hole transporting materials, the electroluminescent material and the electron injecting materials can be mixed together to form one layer, whiich simplifies the construction.

The first electrode is preferably a transparent substrate such as a conductive glass or plastic material which acts as the anode. Preferred substrates are conductive glasses such as indium tin oxide coated glass, but any glass which is conductive or has a conductive layer such as a metal or conductive polymer can be used. Conductive polymers and conductive polymer coated glass or plastics materials can also be used as the substrate.

The cathode is preferably a low work function metal, e.g. aluminium, calcium, lithium, magnesium and alloys thereof such as silver/magnesium alloys, rare earth metal alloys etc; aluminium is a preferred metal. A metal fluoride such as an alkali metal, rare earth rnetal or their alloys can be used as the second electrode for example by having a metal fluoride layer formed orr a metal.

The electroluminescent devices of the present invention can be used as both active and passive displays. Examples

The invention is illustrated in the examples.

Preparative Methods 1. Europιum IIIu\aphthylcarboxalate)^(Acrylic acid)_n(Styrene)_m (Eu(Naph AA n (Styrene)J

To a mixture of recrystallised naphthoic acid (0.93 g, 5.4 x 10^'3 oles) in ethanol (20 ml) and distilled acrylic acid (0.19 g, 23 x 10^" moles) in ethanol (10 ml) was added sodium hydroxide (NaOH) (0.32 g, 8.1 ? 10^"3 moles) in water (10ml) and stirred for ten minutes.

Europium chloride (EuCl₃.6H₂0) (0.92 g, 2.7 x 10^"3 moles) in ethanokwater (20 ml, 2:1) was then slowly added to the above mixture and refluxed wnile stirring for three hours to yield a pale brown colour product [Eu(Naph)₂(AA)] . The product was filtered off and washed thoroughly with water, followed by ethanol and vacuum dried for five hours. Yield: 0.8 g (52%). Melting point: > 260 °C.

Eu(Naph-COO)₂(AA) (0.2 g) was dissolved in methanol (2 ml) and mixed with styrene (4 g). The homogeneous solution was placed in a tube and 1,1'- azobis(cycloheχane carbonitrile) (0.02 } was added. The- solution was degassed by three freeze-thaw cycles under vacuum, then sealed and heated in an oil bath at 60°C. for four hours. The viscous homogeneous solution was then dissolved in tetrahydrofurari (THF) and purified by reprecipitating with methanol, and dried under vacuum for a day. Melting point: 293 °C (Differential Scanning Calorimetry, DSC).

The complex had the structure below where m and n had an average value greater than 5.

The photolumine scent spectrum was measured and the results shown in fig. 23.

Dimethylaminopyridine (DMAP) polymer-bound (2% crosslinked poly(styrene), typical DMAP loading 5.5 - 6.6 mmol N/g) (0.5 g) and terbium(IIi)[tris(2,2,6,6- tetramethyl-3,5-heptanedionate)]₃ (0.7 g, 0.99 mmol) were heated together in a boiling mixture of dichloromethane (CH₂C1₂) and toluene (1 -1, 50 ml) for ten minutes. The solution was cooled to room temperature and the orange solid filtered under vacuum and washed with 100 ml of CH₂C1 . The solid was dried in a vacuum oven overnight to give a light orange solid with green photoluminescence. Analysis (ICP-AES) shows terbium loading at 9.9 %). The complex had the structure below where m and n had an average value greater than 5.

The photolun inescent spectrum was measured and the results shown in fig. 24.

Photoluminescence data is set out in the table where the eolour coordinates are according to the CIE colour chart.

Table

Device Structure

A device of structure shown in figure 22 was fabricated where (1) is an ITO anode, (2) is a hole transporting layer, (3) is the electroluminescent layer, (4) is an electron transmitting layer and (5) is the aluminium cathode. The device had the structure :-

ITO(100Ω cmNPEDOT(170nm) Eu(Naph)₂(AA)„(Styrene)„₁.(50 nm)/ BCP(6nm)/Al, where PEDOT is a hole transporting layer of polystyrene doped with poly(3,4- ethylenedioxythiophene) and BCP is an electron transmitting layer (hole blocking layer) of bathocupron.

An ITO coated glass piece (1 x 1cm ) had a portion etctred out with concentrate*! hydrochloric acid to remove the ITO and was cleaned and dried. The device w&_s fabricated by spin coating the indium tin oxide (ITO) layer in two stages.

The Hole Transporting Layer

Poly(styrene-sulphonate) doped with PEDOT (PEDOT-PSS), as a solution in water, was spin coated on the etched ITO as the first layer. Spin coating conditions for this layer were as follows.

The Emissive Layer A solution of Eu(Naph)₂(AA) (Styrene)m was prepared in HF (10 mg solid in 5 rnl solvent) as above. Spin coating conditions were as follows.

The Hole Blocking Layer

Bathocupron (BCP) was used as a hole-blocker and vacuum evaporated onto the device, followed by aluminium (Al) layer as a top cathode.

The electroluminescent properties of the device of exanrple was measured. The 3TO electrode was always connected to the positive terminal. An electric current was passed through the structure and the light emitted was a reddish orange light typical of europium (III) complexes. A plot of current density against voltage is shown int fig. 25.

Claims

1. An electroluminescent compound of formula (Lc _nM where M is a transition metal, rare earth, lanthanide or an actinide, Lα is a β diketone substituted by a polymer, an oligomer or a dendrimer and n is the valence state of M.

2. An electroluminescent compound of formula

( Rr- ^÷— where M is a rare earth, transition metal, lanthanide or an actinide, Lα is a β diketone and n is the valence state of M and Lp is a neutral ligand and in which at least one of Lα and Lp is substituted by a polymer, an oligomer or a dendrimer.

3. An electroluminescent compound as claimed in claim 2 or 3 in which the ligands Lot can be the same or different.

4. An electroluminescent compound as claimed in any one of claims 1 to 3 in which Lp can be monodentate, bidentate or polydentate and there are a plurality of ligands Lp which can be the same or different.

5. An electroluminescent compound as claimed in any one of the preceding claims of formula (Lα)_q (Mi)_r (M₂)_s where Mi is the same as M above, M₂ is M or a non rare earth metal, Lα is as above, r is at least one s is at least one and q is the combined valence state of r(Mι) and s(M ) and the metals MLi can be the same or different and the metals M₂can be the same or different.

6. An electroluminescent compound as claimed in any one of claims 1 to 5 which has the general formula (Lα)_q Λι)_r (M₂)_s (Lp), where Lp is as above and where M is the same as M above, M₂ is M or a non rare earth metal, Lα is a as above, r is at least one, s is at least one and q is the combined valence state of r(M and s( ₂.) and the metals Mi can be the same or different and the metals M₂ can be the same or different.

7. An electroluminescent compound as claimed in any one of claims 2 to 6 in which Lp has the formula (XVIH) to (XXN) herein or of figures 1 to 8, 17 or 18 of the drawings.

8. An electroluminescent compound as claimed in any one of claims 1 to 7 in which Lot has the formula

(I) (II)

Polyme

(Ilia) (fflb) or Polymer

Polymer

Polymer or

(Illc) (Hid)

where the term polymer includes oligomers and dendrimers, and where R is selected from hydrogen, and substituted and unsvibstituted hydrocarbyl groups such as substituted and unsubstituted aliphatic grou s, substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups X is Se, S or O, Y is R or hydrogen, substituted or unsubstituted hydrocarbyl groups, such as substituted and unsubstituted aromatic, heterocyclic and. polycyclic ring structures, fluorine, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups or nitrile, R and Y can also form substituted and unsubstituted fused aromatic, heterocyclic and polycyclic ring structures and can be copolymerisable with a monomer, e.g. styrene and the polymer is an organic polymer, oligomers or dendrimer and can he linked to R and/or Y to form a ring structure m is an integer preferably from 1 to 5 and Ri and Rz are the same or different R moieties.

9. An electroluminescent compound as claimed in any one of claims 1 to 8 in which the polymer, oligomer and dendrimer is selected from substituted and unsubstituted polyolefins such as polyethylene, polypropylene, polybutylene, polyvinyl chlorides and their copolymers, substituted and unsubstituted polymers such as polystyrene and their copolymers, polyesters such as polyacrylates, polyuretlianes polyethers, polyamines, polysυlphonates. 0

10. An electrolu inescent compound as claimed in claim 4 or 5 in which the polymer, oligomer and dendrimer is selected electroluminescent light emitting organic polymers, oligomers and dendrimers.

_5 11. An electroluminescent compound as claimed in claim 10 in whvich the polymer is selected from poly (p-phenylenevinylene)-PPN and copolymers including PPV.

12. An electroluminescent compound as claimed in claim 10 in which the polymer is selected from poly(2,5 dialkoxyphenylerxe vinylene) such as poly (2-methoxy-5-(2- 0 methoxypentyloxy-l,4-phenylene vinylene), poly(2-methoxypentyloxy)- 1,4- phenylenevinylene), poly(2-methoxy-5-(2-dodecyloxy-l ,4-phenylenevinylene) and other poly(2,5 dialkoxyphenylenevinylenes) with at least one of the alkoxy groups being a long chain solubilising alkoxy group, poly fluorenes and oligofluorenes, polyphenylenes and oligophenylenes, polyanthracenes and oligo anthracenes, 5 ploythiophenes and oligothiophenes and copolymers thereof.

13. An electrolu inescent compound as claimed in any one of claims 1 to 12 in which the metal M is selected from Sm(TII), Eu(II), Eu(III), Tb(III), Dy(fll), Yb(III), Lu(III), Gd (Ifl), ^"U(III), U(NI)O₂, Tm(HI), Th(PV), Ce (III), Ce(rV), Pr(III), Νd(Iϊι), 0 Pm(III), Dy(III), Ho(III), Er(III), manganese, iron, ruthenium, osmium, cobalt, nickel, palladium(II), palladium(rV), platinumtll), platinum(IV), cadmium, chromium, titanium, vanadium, zirconium, tantulu n, molybdenum, rhodium, iridium, titanium, niobium, scandium, yttrium.

14. An electroluminescent compound as claimed in any one of claims 5 to 14 in which the metal M₂ is a non rare earth metal selected from lithium, sodium, potassium, rubidium, caesium, beryllium, magnesium, calcium, strontium, barium, copper (I), copper (II), silver, gold, zinc, cadmium, boron, aluminium, gallium, indium, germanium, tin (II), tin (IV), antimony (II), antimony (IV), lead (II), lead (IN) and metals of the first, second and t aird groups of transition metals in different valence states, e.g. manganese, iron, ruthenium, osmium, cobalt, nickel, palladium(II), palladium(TV), platinurn(II), platinum(IV), cadmium, chromium, titanium, vanadium, zirconium, tantulurn, molybdenum, rhodiur , iridium, titanium, niobium, scandium, yttrium.

15. An electroluminescent device whic i comprises (i) a first electrode, (ii) a layer of electroluminescent compound as claimed in any one of claims 1 to 14 and (iii) a second electrode.

16. An electroluminescent device as claimed in claim 15 in which there is a layer of a hole transmitting material between the first electrode and toe electroluminescent layer.

17. An electroluminescent device as claimed in claim 16» in which the hole transmitting material is an aromatic amine complex.

18. An electroluminescent device as claimed in claim 16 in which the hole transmitting material is polyaromatic amine complex.

19. An electroluminescent device as claimed in claim 16 in which the hiole transmitting material is a film of a polymer selected from, poly(vinylcarbazole), N_^N'- diphenyl-N,N'-bis (3-methylρhenyl) -1,1' -biphenyl -4,4'-diamine (TPD), polyaniline, substituted polyanilines, polythiophenes, substituted polythiophenes, polysilanes and substituted poly ilanes.

20. An electroluminescent device as claimed in claim 17 in which the hiole transmitting material is a film of a compound of formula (XXVI) or (XXVII) herein or as in figures 12 to 16 of the drawings.

21. An electroluminescent device as claimed in claim 17 in which the Eiole transmitting material is a copolymer of aniline, a copolymer of aniline witha o- anisidine, m-sulphanilic acid or o-aminophenol, or o-toluidine with o-aminophe=nol, o-ethylaniline, o-phenylene diamine or with an amino anthracene.

22. An electroluminescent device as claimed in claim 17 in which the liole transmitting material is a conjugated polymer.

23. An electroluminescent device as claimed in claim 22 in which the conjugiated polymer is selected from poly (p-phenylenevinylene)-PPV and copolymers including

PPV, poly(2,5 dialkoxyprienylene vinylene), poly (2-methoxy-5-(2- methoxypentyloxy- 1 ,4-phenylene vinylene), poly(2-methoxypentyloxy)— 1 ,4- phenylenevinylene), pory(2-methoxy-5-(2-dodecyloxy- 1,4-phenylenevinylene) and other poly(2,5 dialkoxyphenylenevinylenes) with at least one of the alkoxy groups being a long chain solubilising alkoxy group, poly fluorenes and oligofluorenes, polyphenylenes and oligophenylenes, polyanthracenes and oligo anthracenes, ploythiophenes and oligothiophenes.

24. An electroluminescent device as claimed in any one of claims 16 o 23 in which the electroluminescent compound is mixed with the hole transmitting material.

25. An electroluminescent device as claimed in any one of claims 17 to 2A in which there is a layer of an electron transmitting material between the cathode and the electroluminescent compound layer.

26. An electroluminescent device as claimed in claim 25 in which the electron transmitting material is a metal quinolate.

27. An electroluminescent device as claimed in claim 26 in which the metal quinolate is an aluminium quinolate or lithium quinolate.

28. An electroluminescent device as claimed in claim 25 in which the electron transmitting material is of formula Mx(DBM)_n where Mx is a metal and DBM is dibenzoyl methane and n is the valency of Mx.

29. An electroluminescent device as claimed in claim 25 in which the electron transmitting material is a cyano anthracene snch as 9,10 dicyano anthracene, a polystyrene sulphonate or a compound of formulae shown in figures 9 or 10 of the drawings.

30. An electroluminescent device as claimed in any one of claims 25 to 29 in which the electron transmitting material is mixed with the electroluminescent corrapound.

31. An electroluminescent device as claimed in any one of the claims L 7 to 30 in which the first electrode is a transparent electricity conducting glass electro* de.

32. An electroluminescent device as claimed in any one of the claims L 7 to 31 in which the second electrode is selected from alunαinium, calcium, lithium, magnesium and alloys thereof and silver/magnesium alloys.