Field of the Invention

The present invention relates to phosphorescent light-emitting compounds; compositions, solutions and light-emitting devices comprising said light-emitting compounds; and methods of making said light-emitting devices.

Background of the Invention

Electronic devices containing active organic materials are attracting increasing attention for use in devices such as organic light emitting diodes (OLEDs), organic photoresponsive devices (in particular organic photovoltaic devices and organic photosensors), organic transistors and memory array devices. Devices containing active organic materials offer benefits such as low weight, low power consumption and flexibility. Moreover, use of soluble organic materials allows use of solution processing in device manufacture, for example inkjet printing or spin-coating.

An OLED may comprise a substrate carrying an anode, a cathode and one or more organic light-emitting layers between the anode and cathode.

Holes are injected into the device through the anode and electrons are injected through the cathode during operation of the device. Holes in the highest occupied molecular orbital (HOMO) and electrons in the lowest unoccupied molecular orbital (LUMO) of a light- emitting material combine to form an exciton that releases its energy as light.

A light emitting layer may comprise a semiconducting host material and a light-emitting dopant wherein energy is transferred from the host material to the light-emitting dopant. For example, J. Appl. Phys. 65, 3610, 1989 discloses a host material doped with a fluorescent light-emitting dopant (that is, a light-emitting material in which light is emitted via decay of a singlet exciton).

Phosphorescent dopants are also known (that is, light-emitting dopants in which light is emitted via decay of a triplet exciton).

Suitable light-emitting materials include small molecule, polymeric and dendrimeric materials. Suitable light-emitting polymers include poly(arylene vinylenes) such as poly(p- phenylene vinylenes) and polyarylenes such as polyfluorenes. OLEDs containing red, green and blue light-emitting materials for applications such as displays and lighting are known.

OLEDs containing infrared emitting materials are also known as disclosed in, for example, Chuk-Lam Ho, Hua Li and Wai-Yeung Wong, "Red to near-infrared organometallic phosphorescent dyes for OLED applications", J. Organomet. Chem. 751 (2014), 261-285. However, a problem associated with infrared emitting OLEDs is low efficiency.

It is an object of the invention to improve the efficiency of infrared emitting OLEDs.

Summary of the Invention

In a first aspect the invention provides a compound of formula (I):

(I) wherein:

M is a transition metal;

Ar is a 5 or 6 membered heteroaryl ring or a polycyclic heteroaromatic group;

2

Ar is a polycyclic group comprising two or more rings selected from aromatic and heteroaromatic rings;

Ar 1 and Ar 2 may be linked by a direct bond or divalent linking group;

L is a ligand; x is at least 1 ; y is 0 or a positive integer; a is 0 or a positive integer; b is 0 or a positive integer;

R 1 , FT2 and R 3 ³ are each independently a substituent; and

(i) Ar ¹ is a polycyclic hetero aromatic group; or

(ii) Ar 1 is a 5 or 6 membered heteroaryl ring and Ar 2 is a polycyclic group comprising at least 3 rings selected from aromatic and heteroaromatic rings.

In a second aspect the invention provides a composition comprising a host material and a compound according to the first aspect.

In a third aspect the invention provides a solution comprising a compound or composition according to the first or second aspect dissolved in one or more solvents.

In a fourth aspect the invention provides an organic light-emitting device comprising an anode, a cathode and a light-emitting layer between the anode and cathode wherein the light- emitting layer comprises a compound or composition according to the first or second aspect.

In a fifth aspect the invention provides a method of forming an organic light-emitting device according to claim the fourth aspect, the method comprising the step of depositing the light- emitting layer over one of the anode and cathode, and depositing the other of the anode and cathode over the light-emitting layer.

Description of the Drawings

The invention will now be described in more detail with reference to the Figures, in which: Figure 1 illustrates an OLED according to an embodiment of the invention. Detailed Description of the Invention

Figure 1, which is not drawn to any scale, illustrates schematically an OLED 100 according to an embodiment of the invention. The OLED 100 is carried on substrate 107 and comprises an anode 101, a cathode 105 and a light-emitting layer 103 between the anode and the cathode. Further layers (not shown) may be provided between the anode and the cathode including, without limitation, hole-transporting layers, electron-transporting layers, hole- blocking layers, electron-blocking layers, hole-injection layers and electron-injection layers.

Exemplary OLED structures including one or more further layers include the following:

Anode / Hole-injection layer / Light-emitting layer / Cathode

Anode / Hole transporting layer / Light-emitting layer / Cathode

Anode / Hole-injection layer / Hole-transporting layer / Light-emitting layer / Cathode

Anode / Hole-injection layer / Hole-transporting layer / Light-emitting layer / Electron- transporting layer / Cathode.

Light-emitting layer 103 may contain a host material and a phosphorescent compound of formula (I).

The device may contain more than one light-emitting layer. The light-emitting layer or layers may contain the phosphorescent compound of formula (I) and one or more further light- emitting compounds, for example further phosphorescent or fluorescent light-emitting materials having a colour of emission differing from that of the compound of formula (I). Preferably, light-emitting layer 103 is the only light-emitting layer of the device. Preferably, at least 90 % or 95 % of the light emitted by the device when in use, more preferably all light, is light emitted from the compound of formula (I).

Compounds of formula (I) preferably have a photoluminescence spectrum with a peak of at least 650 nm, optionally in the range of 650-1000 nm, preferably 700-850 nm.

The photoluminescence spectrum of a compound of formula (I) may be measured by casting 5 wt % of the material in a polystyrene film onto a quartz substrate and measuring in a nitrogen environment using apparatus C9920-02 supplied by Hamamatsu.

Metal M of the phosphorescent compound of formula (I) may be any suitable transition metal, for example a transition metal of the second or third row of the d-block elements (Period 5 and Period 6, respectively, of the Periodic Table). Exemplary metals include Ruthenium, Rhodium, Palladium, Silver, Tungsten, Rhenium, Osmium, Iridium, Platinum and Gold. Preferably, M is iridium. The compound of formula (I) may contain one or more ligands L other than ligands of formula:

Ligand L, if present, may be a monodentate or polydentate ligand. Optionally, L is a bidentate ligand. Optionally, L is selected from 0,0 cyclometallating ligands; N,0 cyclometallating ligands, optionally picolinate; and N,N cyclometallating ligands.

L may be a ligand of formula:

wherein R in each occurrence is independently a substituent, preferably Ci_io alkyl and R is H or a substituent, preferably H or CMO alkyl; and wherein one R ¹⁶ and R ¹⁷ may be linked to form a ring, optionally a 6-10 membered aromatic or heteroaromatic ring that may be unsubstituted or substituted with one or more substituents, optionally one or more substituents selected from Ci_ ₂ o hydrocarbyl groups.

Preferably R ¹⁶ is CM alkyl, more preferably methyl or ieri-butyl.

Preferably, y is 0 or 1.

The compound of formula (I) comprises at least one ligand of formula:

In case (i) Ar 1 is a polycyclic heteroaromatic group and Ar 2 is a polycyclic group comprising at least 2 rings selected from aromatic and heteroaromatic rings.

By "polycyclic heteroaromatic group" as used herein is meant a polycyclic group comprising a heteroaromatic ring and further comprising one or more rings selected from aromatic and heteroaromatic rings. The rings of the polycyclic heteroaromatic group may consist of fused heteroaromatic or aromatic rings or may comprise one or more non-aromatic rings.

Preferably, all aromatic or heteroaromatic rings of the polycyclic heteroaromatic group are conjugated to each other directly or through one or more intervening aromatic or

heteroaromatic rings.

In case (ii) Ar 1 is a monocyclic 5 or 6 membered heteroaryl ring and Ar 2 is a polycyclic group comprising at least 3 rings selected from aromatic and heteroaromatic rings.

The polycyclic group Ar may consist of fused heteroaromatic or aromatic rings or may comprise one or more non-aromatic rings. Preferably, all aromatic or heteroaromatic rings of the polycyclic group Ar are conjugated to each other directly or through one or more intervening aromatic or heteroaromatic rings.

A polycyclic group Ar 1 or Ar 2 may be a 10-30 membered polycyclic group.

In case (i), Ar ¹ is optionally a 10-membered polycyclic heteroaromatic of C and N atoms, optionally a polycyclic heteroaromatic of pyridine or pyrazine fused to any of benzene, pyridine or pyrazine. Ar ¹ is preferably selected from quinoline or isoquinoline. Optionally, the ligand Ar 1 -Ar 2 is selected from the following ligands wherein the quinoline or isoquinoline group is substituted with a triazine group as illustrated in Formula (I) and optionally with one or more substituents R 1 and wherein Ar 2 is unsubstituted or substituted with one or more substituents R ,:

In case (i),optionally Ar 2 is selected such that ligand Ar 1 -Ar2 is selected from the following ligands wherein Ar 1 may be substituted with one or more substituents R 1 and wherein Ar2 is unsubstituted or substituted with one or more substituents R :

wherein X in each occurrence is independently CR 2 ₂ , SiR 2 ₂ , NR 2 , O or S wherein R 2 independently in each occurrence is a substituent. In case (ii), Ar is a monocyclic 5 or 6 membered heteroaromatic ring, preferably a 6- membered heteroaromatic ring of C and N atoms, preferably pyridine, and Ar is preferably a polyaromatic group, optionally a C 10-20 poly aromatic compound. Preferably, Ar of case (ii) is a polyaromatic hydrocarbon of 3 or more fused benzene rings, preferably phenanthrene, that may be unsubstituted or substituted with one or more substituents R .

In either case (i) or (ii) there may be a direct bond or divalent linking group between Ar ¹ and

2 1 2

Ar (in addition to the C-C bond shown in Formula (I) between Ar and Ar ).

R 1 and R 2 , if present, may independently in each occurrence be selected from the group consisting of:

Ci_2o alkyl wherein one or more non-adjacent C atoms of the Ci_ ₂ o alkyl may be replaced with -0-, -S-, C=0 or -COO- and one or more H atoms may be replaced with F; and

3 3

a group of formula -(Ar )p wherein Ar in each occurrence is a C ₆ -2o aryl group or a 5-20 membered heteroaryl group that may be unsubstituted or substituted with one or more substituents; and p is at least 1, optionally 1, 2 or 3.

Substituents of Ar , if present, are optionally selected from the group consisting of F, CN, N0 ₂ and Ci_ ₂ o alkyl wherein one or more non-adjacent C atoms of the Ci_ ₂ o alkyl may be replaced with -0-, -S-, C=0 or -COO- and one or more H atoms may be replaced with F. If present, the one or more substituents of Ar are preferably selected from C _1-2 o alkyl.

Optionally, R in each occurrence is independently selected from the group consisting of:

Ci_ ₂ o alkyl wherein one or more non-adjacent C atoms of the Ci_ ₂ o alkyl may be replaced with -0-, -S-, C=0 or -COO- and one or more H atoms may be replaced with F; and a group of formula -(Ar ⁴ )q wherein Ar ⁴ in each occurrence is a C ₆ - ₂ o aryl group or a 5-20 membered heteroaryl group that may be unsubstituted or substituted with one or more substituents; and q is at least 1.

Substituents of Ar ⁴ , if present, are optionally selected from the group consisting of F, CN, N0 ₂ and C _1-2 o alkyl wherein one or more non-adjacent C atoms of the C _1-2 o alkyl may be replaced with -0-, -S-, C=0 or -COO- and one or more H atoms may be replaced with F. If present, the one or more substituents of Ar4 are preferably selected from Ci_ ₂ o alkyl.

Preferably, R is phenyl that may be unsubstituted or substituted with one or more substituents.

The triazine substituent of formula (I) may be bound to any available position of Ar ¹ , preferably an aromatic carbon atom of Ar ¹ . Preferably, the triazine substituent is bound to an atom meta-to the N atom of Ar ¹ that is bound to M.

Exemplary compounds of formula (I) according to case (i) include the following:

10

11

12 Exemplary compounds of formula (I) according to case (ii) include the following:

Host Material

The host material has a triplet excited state energy level Ti that is no more than 0.1 eV lower than, and preferably at least the same as or higher than, the phosphorescent compound of formula (I) in order to allow transfer of triplet excitons from the host material to the phosphorescent compound of formula (I).

The triplet excited state energy levels of a host material and a phosphorescent compound may be determined from the energy onset of its phosphorescence spectrum measured by low temperature phosphorescence spectroscopy (Y.V. Romaovskii et al, Physical Review Letters, 2000, 85 (5), pl027, A. van Dijken et al, Journal of the American Chemical Society, 2004, 126, p7718).

The host material preferably has a lowest unoccupied molecular orbital (LUMO) level of at least 2.5 eV from vacuum.

The host material may be a polymer or a non-polymeric material.

The compound of formula (I) may be blended with or covalently bound to the host material.

The metal complex of formula (I) may be provided in an amount in the range of 0.1-40 wt % in a composition comprising a mixture of the host and the metal complex of formula (I).

In the case of a host polymer the compound of formula (I) may be provided as a side-group or end group of the polymer backbone or as a repeat unit in the backbone of the polymer. In this case, repeat units comprising a compound of formula (I) may form 0.1-40 mol % of the repeat units of the polymer.

A host polymer may comprise a repeat unit of formula (V):

(V) wherein Ar ⁵ and Ar ⁶ are each independently aryl or heteroaryl that may be unsubstituted or substituted with one or more, optionally 1, 2, 3 or 4, substituents; u and v in each occurrence is independently at least 1, optionally 1, 2 or 3, preferably 1; R ⁶ is a substituent; and Y is N or CR ⁹ , wherein R ⁹ is H or a substituent, preferably H or CMO alkyl and with the proviso that at least one Y is N.

Preferably, Ar ⁵ and Ar ⁶ and are each independently unsubstituted or substituted C ₆ - ₂ o aryl, more preferably Cio- ₂ 0 aryl- Exemplary groups Ar ⁵ and Ar ⁶ are phenyl and naphthyl, preferably naphthyl.

Preferably, R ⁶ is a C _1-2 o alkyl group or a group of formula -(Ar ⁷ )w wherein Ar ⁷ independently in each occurrence is an aryl or heteroaryl group that may be unsubstituted or substituted with one or more, optionally 1, 2, 3 or 4, substituents and w is at least 1, optionally 1, 2 or 3. Preferably, each Ar is independently selected from unsubstituted or substituted phenyl, pyridyl, pyrimidine, pyrazine and triazine.

Substituents of Ar ⁵ , Ar ⁶ and Ar ⁷ may be selected from substituted or unsubstituted alkyl, optionally Ci_ ₂ o alkyl, wherein one or more non-adjacent C atoms may be replaced with O, S, C=0 or -COO- and one or more H atoms may be replaced with F.

In one preferred embodiment, all 3 groups Y are N.

Preferably, u and v are each 1.

Preferably, w is 1, 2 or 3. Exemplary repeat units of formula (V) have the following structures which may be unsubstituted or substituted with one or more substituents, preferably one or more Ci_ ₂ o alkyl groups:

A host polymer may comprise a repeat unit of formula (XI):

(XI) wherein each R ¹¹ is independently H or a substituent. Optionally, substituents R ¹¹ are independently selected from C ₆ - ₂ o aryl that may be unsubstituted or substituted with one or more substituents, optionally one or more CMO alkyl groups, and C _1-2 o alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, COO or CO and one or more H atoms may be replaced with F. Preferably, each R ¹¹ is independently selected from H and Ci_ ₂ o alkyl. A host polymer may comprise a repeat unit of formula (VI):

(VI) wherein Ar ⁸ , Ar ⁹ and Ar ¹⁰ in each occurrence are independently selected from substituted or unsubstituted aryl or heteroaryl, g is 0, 1 or 2, preferably 0 or 1, R independently in each occurrence is a substituent, and d, e and f are each independently 1, 2 or 3.

R 13 , which may be the same or different in each occurrence when g is 1 or 2, is preferably selected from the group consisting of alkyl, optionally C _1-2 o alkyl, Ar ¹¹ and a branched or linear chain of Ar ¹¹ groups wherein Ar ¹¹ in each occurrence is independently substituted or unsubstituted aryl or heteroaryl.

Any two aromatic or heteroaromatic groups selected from Ar ⁸ , Ar ⁹ , and, if present, Ar ¹⁰ and Ar ¹¹ that are directly bound to the same N atom may be linked by a direct bond or a divalent linking atom or group. Preferred divalent linking atoms and groups include O, S; substituted N; and substituted C.

8 10

Ar and Ar are preferably C ₆ - ₂ o aryl, more preferably phenyl, that may be unsubstituted or substituted with one or more substituents.

In the case where g = 0, Ar ⁹ is preferably C ₆ - ₂ o aryl, more preferably phenyl, that may be unsubstituted or substituted with one or more substituents.

In the case where g = 1, Ar ⁹ is preferably C ₆ - ₂ o aryl, more preferably phenyl or a polycyclic aromatic group, for example naphthalene, perylene, anthracene or fluorene, that may be unsubstituted or substituted with one or more substituents.

R ¹³ is preferably Ar ¹¹ or a branched or linear chain of Ar ¹¹ groups. Ar ¹¹ in each occurrence is preferably phenyl that may be unsubstituted or substituted with one or more substituents. Exemplary groups R include the following, each of which may be unsubstituted or substituted with one or more substituents, and wherein * represents a point of attachment to N:

d e and f are preferably each 1.

Ar ⁸ , Ar ⁹ , and, if present, Ar ¹⁰ and Ar ¹¹ are each independently unsubstituted or substituted with one or more, optionally 1, 2, 3 or 4, substituents. Exemplary substituents may be selected from substituted or unsubstituted alkyl, optionally Ci_ ₂ o alkyl, wherein one or more non-adjacent C atoms may be replaced with optionally substituted aryl or heteroaryl (preferably phenyl), O, S, C=0 or -COO- and one or more H atoms may be replaced with F.

Preferred substituents of Ar ⁸ , Ar ⁹ , and, if present, Ar ¹⁰ and Ar ¹¹ are Ci_ ₄ o hydrocarbyl, preferably Ci_ ₂ o alkyl.

Preferred repeat units of formula (VI) include unsubstituted or substituted units of formulae (VI-1), (VI-2) and (VI-3):

1 2 3

A host polymer may comprise arylene repeat units, preferably C ₆ - ₂ o arylene repeat units, which may be unsubstituted or substituted with one or more substituents. Exemplary arylene repeat units are phenylene, fluorene, indenofluorene and phenanthrene repeat units, each of which may be unsubstituted or substituted with one or more substituents. Preferred substituents are selected from CI_ ₄ Q hydrocarbyl groups. Arylene repeat units may be selected from formulae (VII)

wherein t in each occurrence is independently 0, 1, 2, 3 or 4, preferably 1 or 2; R

independently in each occurrence is a substituent; s in each occurrence is independently 0, 1 or 2, preferably 0 or 1; and R independently in each occurrence is a substituent wherein two R groups may be linked to form an unsubstituted or substituted ring.

Where present, each R 7 and R 8 may independently be selected from the group consisting of: alkyl, optionally C _1-2 o alkyl, wherein one or more non-adjacent C atoms may be replaced with optionally substituted aryl or heteroaryl, O, S, substituted N, C=0 or - COO-, and one or more H atoms may be replaced with F; aryl and heteroaryl groups, preferably C ₆ - ₂ o aryl groups, more preferably phenyl, that may be unsubstituted or substituted with one or more substituents; and a linear or branched chain of aryl or heteroaryl groups, preferably C ₆ - ₂ o aryl groups, more preferably phenyl, each of which groups may independently be substituted, optionally a group of formula -(Ar 12 ) _r wherein each Ar 12 is independently an aryl or heteroaryl group and r is at least 2, preferably a branched or linear chain of phenyl groups. In the case where R 7 or R 8 comprises an aryl or heteroaryl group, or a linear or branched chain of aryl or heteroaryl groups, the or each aryl or heteroaryl group may be substituted with one or more substituents R selected from the group consisting of: alkyl, for example C _1-2 o alkyl, wherein one or more non-adjacent C atoms may be replaced with O, S, substituted N, C=0 and -COO- and one or more H atoms of the alkyl group may be replaced with F;

NR ⁹ ₂ , OR ⁹ , SR ⁹ , SiR ⁹ ₃ and fluorine, nitro and cyano; wherein each R ⁹ is independently selected from the group consisting of alkyl, preferably Ci_ ₂ o alkyl; and aryl or heteroaryl, preferably phenyl, optionally substituted with one or more Ci_ ₂ o alkyl groups.

Substituted N, where present, may be -NR ¹⁰ - wherein R ¹⁰ is a substituent and is optionally a Ci_ ₄ o hydrocarbyl group, optionally a Ci_ ₂ o alkyl group.

Preferred substituents of aryl or heteroaryl groups of R 7 or R 8 are selected from Ci_ ₂ o alkyl.

In the case where two groups R form a ring, the one or more substituents of the ring, if present, are optionally selected from C _1-2 o alkyl groups.

Preferably, each R 7 , where present, and R 8 is independently selected from Ci_ ₄ o hydrocarbyl. Preferred Ci_ ₄ o hydrocarbyl groups are Ci_ ₂ o alkyl; unsubstituted phenyl; phenyl substituted with one or more C _1-2 o alkyl groups; and a linear or branched chain of phenyl groups, wherein each phenyl may be unsubstituted or substituted with one or more C _1-2 o alkyl groups.

A host polymer may comprise or consist of repeat units of formula (V), (VI) and / or (XI) and one or more arylene repeat units as described herein, optionally one or more arylene repeat units of formulae (VII) -(X).

Repeat units of formulae (V), (VI) and / or (XI) may each be provided in the host polymer in an amount in the range of 1-50 mol %, optionally 5-50 mol %.

Arylene repeat units may form 1-99 mol %, preferably 10-95 mol % of the repeat units of a host polymer. Polymers as described herein including, without limitation, host polymers polymers, may have a polystyrene-equivalent number- average molecular weight (Mn) measured by gel permeation chromatography in the range of about 1x10 3 to 1x108, and preferably 1x103 to 5xl0 ⁶ . The polystyrene-equivalent weight- average molecular weight (Mw) of the polymers described herein may be 1x10 3 to 1x108 , and preferably 1x104 to 1x107.

Polymers as described herein including, without limitation, host polymers, are preferably amorphous.

Charge transporting and charge blocking layers

A hole transporting layer may be provided between the anode of an OLED and a light- emitting layer containing a compound of formula (I).

An electron transporting layer may be provided between the cathode of an OLED and a light- emitting layer containing a compound of formula (I).

An electron blocking layer may be provided between the anode and the light-emitting layer.

A hole blocking layer may be provided between the cathode and the light-emitting layer.

Transporting and blocking layers may be used in combination. Depending on its HOMO and LUMO levels, a single layer may both transport one of holes and electrons and block the other of holes and electrons.

A charge-transporting layer or charge -blocking layer may be crosslinked, particularly if a layer overlying that charge-transporting or charge-blocking layer is deposited from a solution. The crosslinkable group used for this crosslinking may be a crosslinkable group comprising a reactive double bond such and a vinyl or acrylate group, or a benzocyclobutane group. The crosslinkable group may be provided as a substituent pendant from the backbone of a charge- transporting or charge-blocking polymer. Following formation of a charge-transporting or charge blocking layer, the crosslinkable group may be crosslinked by thermal treatment or irradiation.

If present, a hole transporting layer located between the anode and the light-emitting layer containing the compound of formula (I) preferably contains a hole-transporting material having a HOMO level of less than or equal to 5.5 eV, more preferably around 4.8-5.5 eV as measured by cyclic voltammetry. The HOMO level of the hole transporting material of the hole-transporting layer may be selected so as to be within 0.2 eV, optionally within 0.1 eV, of the compound of formula (I) in order to provide a small barrier to hole transport.

A hole-transporting material of a hole-transporting polymer may be a polymer comprising a repeat unit of formula (VI) as described herein, optionally a homopolymer of a repeat unit of formula (VI) or a copolymer comprising a repeat unit of formula (VI) and one or more co- repeat units, optionally one or more arylene co-repeat units as described herein. One or more repeat units of such a hole-transporting polymer may be substituted with a crosslinkable group, optionally a crosslinkable double bond group and / or a crosslinkable

benzocyclobutane group, that may be crosslinked following deposition of the hole- transporting polymer to form the hole-transporting layer.

If present, an electron transporting layer located between the light-emitting layers and cathode preferably has a LUMO level of around 2.5-3.5 eV as measured by square wave cyclic voltammetry. A layer of a silicon monoxide or silicon dioxide or other thin dielectric layer having thickness in the range of 0.2-2 nm may be provided between the light-emitting layer nearest the cathode and the cathode.

An electron transporting layer may contain a polymer comprising a chain of optionally substituted arylene repeat units, such as a chain of fluorene repeat units.

HOMO and LUMO levels as described herein may be measured by cyclic voltammetry (CV) as follows.

The working electrode potential is ramped linearly versus time. When cyclic voltammetry reaches a set potential the working electrode's potential ramp is inverted. This inversion can happen multiple times during a single experiment. The current at the working electrode is plotted versus the applied voltage to give the cyclic voltammogram trace.

Apparatus to measure HOMO or LUMO energy levels by CV may comprise a cell containing a tert-butyl ammonium perchlorate/ or tertbutyl ammonium hexafluorophosphate solution in acetonitrile, a glassy carbon working electrode where the sample is coated as a film, a platinium counter electrode (donor or acceptor of electrons) and a reference glass electrode no leak Ag/AgCl. Ferrocene is added in the cell at the end of the experiment for calculation purposes. (Measurement of the difference of potential between Ag/AgCl/ferrocene and sample/ferrocene).

Method and settings: 3mm diameter glassy carbon working electrode

Ag/AgCl/no leak reference electrode

Pt wire auxiliary electrode

0.1 M tetrabutylammonium hexafluorophosphate in acetonitrile

LUMO = 4.8 - ferrocene (peak to peak maximum average) + onset

Sample: 1 drop of 5mg/mL in toluene spun @3000rpm LUMO (reduction) measurement:

A good reversible reduction event is typically observed for thick films measured at 200 mV/s and a switching potential of -2.5V. The reduction events should be measured and compared over 10 cycles, usually measurements are taken on the 3 cycle. The onset is taken at the intersection of lines of best fit at the steepest part of the reduction event and the baseline.

Hole injection layers

A conductive hole injection layer, which may be formed from a conductive organic or inorganic material, may be provided between the anode and the light-emitting layer or layers to assist hole injection from the anode into the layer or layers of semiconducting polymer. A hole transporting layer may be used in combination with a hole injection layer.

Examples of doped organic hole injection materials include optionally substituted, doped poly(ethylene dioxythiophene) (PEDT), in particular PEDT doped with a charge-balancing polyacid such as polystyrene sulfonate (PSS) as disclosed in EP 0901176 and EP 0947123, polyacrylic acid or a fluorinated sulfonic acid, for example Nafion ®; polyaniline as disclosed in US 5723873 and US 5798170; and optionally substituted polythiophene or poly(thienothiophene). Examples of conductive inorganic materials include transition metal oxides such as VOx, MoOx and RuOx as disclosed in Journal of Physics D: Applied Physics (1996), 29(11), 2750-2753.

Cathode

The cathode is selected from materials that have a work function allowing injection of electrons into the light-emitting layer or layers. Other factors influence the selection of the cathode such as the possibility of adverse interactions between the cathode and the light- emitting materials. The cathode may consist of a single material such as a layer of aluminium. Alternatively, it may comprise a plurality of metals, for example a bilayer of a low work function material and a high work function material such as calcium and aluminium as disclosed in WO 98/10621. The cathode may contain a layer containing elemental barium, for example as disclosed in WO 98/57381, Appl. Phys. Lett. 2002, 81(4), 634 and WO 02/84759 or a layer containing elemental magnesium. The cathode may contain a thin (e.g. 1-5 nm thick) layer of metal compound between the light-emitting layer(s) of the OLED and one or more conductive layers of the cathode, such as one or more metal layers. Exemplary metal compounds include an oxide or fluoride of an alkali or alkali earth metal, to assist electron injection, for example lithium fluoride as disclosed in WO 00/48258; barium fluoride as disclosed in Appl. Phys. Lett. 2001, 79(5), 2001; and barium oxide. In order to provide efficient injection of electrons into the device, the cathode preferably has a work function of less than 3.5 eV, more preferably less than 3.2 eV, most preferably less than 3 eV. Work functions of metals can be found in, for example, Michaelson, J. Appl. Phys. 48(11), 4729, 1977.

The cathode may be opaque or transparent. Transparent cathodes are particularly

advantageous for active matrix devices because emission through a transparent anode in such devices is at least partially blocked by drive circuitry located underneath the emissive pixels. A transparent cathode comprises a layer of an electron injecting material that is sufficiently thin to be transparent. Typically, the lateral conductivity of this layer will be low as a result of its thinness. In this case, the layer of electron injecting material is used in combination with a thicker layer of transparent conducting material such as indium tin oxide.

It will be appreciated that a transparent cathode device need not have a transparent anode (unless, of course, a fully transparent device is desired), and so the transparent anode used for bottom-emitting devices may be replaced or supplemented with a layer of reflective material such as a layer of aluminium. Examples of transparent cathode devices are disclosed in, for example, GB 2348316.

Encapsulation

Organic optoelectronic devices tend to be sensitive to moisture and oxygen. Accordingly, the substrate 101 preferably has good barrier properties for prevention of ingress of moisture and oxygen into the device. The substrate is commonly glass, however alternative substrates may be used, in particular where flexibility of the device is desirable. For example, the substrate may comprise a plastic as in US 6268695 which discloses a substrate of alternating plastic and barrier layers or a laminate of thin glass and plastic as disclosed in EP 0949850. The device may be encapsulated with an encapsulant (not shown) to prevent ingress of moisture and oxygen. Suitable encapsulants include a sheet of glass, films having suitable barrier properties such as silicon dioxide, silicon monoxide, silicon nitride or alternating stacks of polymer and dielectric as disclosed in, for example, WO 01/81649 or an airtight container as disclosed in, for example, WO 01/19142. In the case of a transparent cathode device, a transparent encapsulating layer such as silicon monoxide or silicon dioxide may be deposited to micron levels of thickness, although in one preferred embodiment the thickness of such a layer is in the range of 20-300 nm. A getter material for absorption of any atmospheric moisture and / or oxygen that may permeate through the substrate or encapsulant may be disposed between the substrate and the encapsulant.

Solution processing

Suitable solvents for forming solution processable formulations of the light-emitting metal complex of formula (I) and compositions thereof may be selected from common organic solvents, such as mono- or poly-alkylbenzenes such as toluene and xylene and mono- or poly-alkoxybenzenes, and mixtures thereof.

Exemplary solution deposition techniques for forming a light-emitting layer containing a compound of formula (I) include printing and coating techniques such spin-coating, dip- coating, roll-to-roll coating or roll-to-roll printing, doctor blade coating, slot die coating, gravure printing, screen printing and inkjet printing.

Coating methods, such as those described above, are particularly suitable for devices wherein patterning of the light-emitting layer or layers is unnecessary - for example for lighting applications or simple monochrome segmented displays.

Printing is particularly suitable for forming a patterned light-emitting layer. A device may be inkjet printed by providing a patterned layer over the first electrode and defining wells for printing. The patterned layer is preferably a layer of photoresist that is patterned to define wells as described in, for example, EP 0880303.

As an alternative to wells, the ink may be printed into channels defined within a patterned layer. In particular, the photoresist may be patterned to form channels which, unlike wells, extend over a plurality of pixels and which may be closed or open at the channel ends. The same coating and printing methods may be used to form other layers of an OLED including (where present) a hole injection layer, a charge transporting layer and a charge blocking layer.

Applications

An organic light-emitting diode containing a compound of formula (I), preferably an infrared emitting compound of formula (I) may be used, without limitation, in night vision goggles, sensors and CMOS chips

Examples

Compound Example 1

Compound Example 1 was prepared according to Scheme 1

Scheme 1

2-Bromo-9-(3,5-dihexylphenyl)-9-methyl-9H-fluorene

An oven dried 3L four neck flask fitted with nitrogen inlet, overhead stirrer and dropping funnel was charged with 2,7-dibromo-9-(3,5-dihexylphenyl)-9-methyl-9H-fluorene (71.0g, 121.90 mmol). Air was replaced with nitrogen for 30 min. Anhydrous THF (710ml) was added and the flask was cooled down to -78°C using dry ice/acetone bath. A solution of n- BuLi (2.5M, 40.0 ml, lOOmmol, 0.82 equivt.) was added dropwise over a period of 30 min and stirred for 1 hr. GC-MS analysis of crude sample showed that it contained -30% starting dibromide. A further of 0.41 equivt of nBuLi (2.5M, 20.0ml, 50mmol) was added and stirred continued for 1.5 hr at -78°C. GC-MS analysis showed no starting material left. The reaction mixture was allowed to warm to -45°C and quenched with careful dropwise addition of 100ml of water then allowed to increase temperature to RT overnight. The reaction was stopped and transferred to a separatory funnel. Heptane (500ml) and water (200ml) were added and allowed to separate. The organic layer was successively washed with 10% NaCl (aq.) solution (100mlx3) and with water (200mlx3) then dried over MgS0 ₄ and filtered. The solvent was evaporated to about 150ml then passed through a small pad of silica and eluted with heptane. The crude material was purified by column chromatography using heptane as eluent (30.8g, colourless oil, 49.8% yield, 98.8% HPLC). 1H-NMR (600MHz, CDCI ₃ , TMS): δ= 7.74 (m, 1H), 7.61(m, 1H), 7.45(m, 1H), 7.34(m, 2H), 7.21 (m, 2H), 6.8(m, 3H), 2.46(t, 4H), 1.82(s, 3H), 1.47 (m, 4H), 1.26(m, 12H), 0.86(t, 6H).

2-(9-(3,5-Dihexylphenyl)-9-methyl-9H-fluoren-2-yl)-4,4,5, 5-tetramethyl-lJ -dioxaborolane

In a 1L three neck flask fitted with nitrogen inlet and condenser were placed 2-bromo-9-(3,5- dihexylphenyl)-9-methyl-9H-fluorene (30.7g, 60.97 mmol) and bis(pinacolato)diboron (17.03g, 67.06mmol, 1.10 equivt). Anhydrous dioxane (300ml) was added and nitrogen was bubbled through the solution for 30min. A suspension of dppf (l.Olg, 1.83 mmol) and PdCi ₂ (dppf).CH ₂ Ci ₂ (1.49g, 1.83mmol) was added to the reaction mixture. Nitrogen bubbling was continued for another 30 min. Potassium acetate (17.95g, 182.9 mmol, 3.0 equivt) was added as solid and the reaction mixture was heated to 110°C for 16 hr. The reaction was stopped and allowed to cool to room temperature. It was then diluted with 200ml EtOAc and transferred to a separatory funnel and allowed to separate. The organic layer was then washed with water (500ml x3) and brine (200ml x 3) and dried over MgS0 ₄ . Evaporation of solvent and purification by silica column using 40% CH ₂ Cl ₂ /heptane gives the ester, (20.3g, 97.61% HPLC, 61.5% yield) a viscous liquid which solidified on standing for few days.

1H-NMR (600MHz, CDC1 ₃ , TMS): δ= 7.82 (m, 1H), 7.70(m, 1H), 7.46(m, 1H), 7.35(m, 2H), 7.20 (m, 2H), 6.82(m, 3H), 2.46(t, 4H), 1.88(s, 3H), 1.48 (m, 4H), 1.42 (s, 12H), 1.22(m, 12H), 0.85(t, 6H). 1 ,4-Dibromoisoquinoline

In a 250ml three neck flask fitted with overhead stirrer and condenser which is also connected to a scrubber solution, 1-hydroxyisoquinoline (lO.g, 68.89mmol) and PBrs (53.38g, 124 mmol) were taken. The reaction mixture was gradually heated to 140°C. At about 125°C - 130°C the solid melts and a deep read solution obtained which on further heating converts to yellowish solid at ~135°C. The reaction mixture was heated at this temperature for lOmin then allowed to cool to room temperature. The pale yellow solid was crushed and added in portions into ice with stirring to obtain a pale yellow powder which was filtered and washed with water (150ml) and dried in an oven at 50°C under vacuum. The crude solid was purified by recrystallisation from EtOAc/heptane (14. lg, 99.93% HPLC, 71.3% yield). 1H-NMR (600MHz, CDC1 ₃ , TMS): S= 8.47 (s, 1H), 8.32(d, 1H), 8.19 (m, 1H), 7.72(m, 1H).

4-Bromo-l-(9-(3,5-dihexylphenyl)-9-methyl-9H-fluoren-2-yl )isoquinoline

In a 1L three neck flask fitted with nitrogen bubbler, overhead stirrer and condenser were taken 2-(9-(3,5-dihexylphenyl)-9-methyl-9H-fluoren-2-yl)-4,4,5,5-t etramethyl-l,3,2- dioxaborolane (20. Og, 36.32mmol), 1,4-dibromoisoquinoline (10.42g, 36.32mmol), toluene (200ml), t-BuOH (100ml) and THF (130ml). To this mixture 40% aq. solution of n- Bu4NOH (100ml, 145mmol) was added followed by water (50ml). Nitrogen was bubbled through the reaction mixture for 1 hr. The catalyst, Pd(Ph ₃ P) ₄ (1.26g, 1.09mmol) was to the reaction mixture and heated to 50oC for 16hr. The reaction was stopped and transferred to a separatory funnel and diluted with 200ml of EtOAc and allowed to separate. The aqueous layer was extracted with EtOAc and the combined organic layer was washed with water (200ml x 3) and brine (200ml x 2). It was then dried over MgS0 ₄ , evapourated to dryness and purified by silica column using 50% CH ₂ Cl ₂ /heptane as eluent (18.2, 99.13% HPLC, 79.4% yield, viscous liq.). 1H-NMR (600MHz, CDC1 ₃ , TMS): S= 8.77 (s, 1H), 8.27(d, 1H), 8.02 (d, 1H), 7.92(d, 1H), 7.85 (d, 1H), 7.77(m, 1H), 7.68 (d, 1H), 7.53(m, 2H), 7.39 (m, 1H), 7.30(d, 2H), 6.81 (m, 3H), 2.46(t, 4H), 1.92(s, 3H), 1.48 (m, 4H), 1.21(m, 12H), 0.8 l(t, 6H). l-(9-(3,5-Dihexylphenyl)-9-methyl-9H-fluoren-2-yl)-4-(4,4,5, 5-tetramethyl-l,3,2- dioxaborolan-2-yl)isoquinorine

In a 1L three neck flask fitted with nitrogen inlet and condenser 4-bromo-l-(9-(3,5- dihexylphenyl)-9-methyl-9H-fluoren-2-yl)isoquinoline (21.96g, 34.81 mmol), bis(pinacolato)diboron (9.72g, 38.29mmol, 1.10 equivt) and potassium acetate (10.25g, 104.43 mmol, 3.0 equivt) were taken. Anhydrous dioxane (220ml) was added and nitrogen was bubbled through the solution for 45min. A suspension of PdCl ₂ (dppf).CH2C12 (0.850g, 1.04 mmol, 0.03 equivt) in dioxane was added into the reaction flask and nitrogen bubbling was continued for another 15 min. The reaction mixture was heated to 110°C, the progress of reaction was monitored by HPLC analysis. After 16 hrs it still contained starting material, bis(pinacolato)diboron (0.886g, 3.48mmol, 0.1 equvt) and fresh catalyst (0.01 eqvt) were added and heated for additional 24 hr. HPLC analysis showed no starting material left then the reaction was stopped and allowed to cool to room temperature. It was then diluted with 200ml EtOAc and transferred to a separatory funnel. It was then washed with water (400ml x3) and brine (200ml x 3) and dried over MgS0 ₄ . Evaporation of solvent gave a dark brown tar which was redissoved in EtOAc (200ml) and treated with charcoal (40g) twice and filtered. Evaporation of the solvent gives light brownish oil (20.92g, 97.11% HPLC, 88.5% yield). 1H-NMR (600MHz, CDC1 ₃ , TMS): δ= 9.02 (s, 1H), 8.74(d, 1H), 8.02 (d, 1H), 7.92 (d, 1H), 7.84(d, 1H), 7.69 (m, 2H), 7.57(s, 1H), 7.40 (m, 2H), 7.29(m, 2H), 6.8 (m, 3H), 2.46(t, 4H), 1.92(s, 3H), 1.49 (m, 4H), 1.43 (s, 12H), 1.20(m, 12H), 0.83 (t, 6H).

4-(4,6-bis(4-(tert-butyl)phenyl) J,5-triazin-2-yl)-l-(9-(3,5-dihexylphenyl)-9-methyl-9H- fluoren-2-yl)isoquinoline

In a 1L three neck flask fitted with nitrogen bubbler, overhead stirrer and condenser l-(9- (3,5-dihexylphenyl)-9-methyl-9H-fluoren-2-yl)-4-(4,4,5,5-tet ramethyl-l,3,2-dioxaborolan-2- yl)isoquinoline (20.92g, 30.87mmol), 2,4-bis(4-(tert-butyl)phenyl)-6-chloro-l,3,5-triazine( 10.55g, 27.78mmol, 0.9 equivt), toluene (200ml) and 20% aq. solution of n-Et ₄ NOH (90ml, 123mmol) was added. Nitrogen was bubbled through the reaction mixture for 1 hr. To the reaction mixture Pd(Ph ₃ P) ₄ (1.07g, 0.93mmol) was added and nitrogen bubbling was continued for another 15 min then heated to 70°C for 16hr. Sampling showed no 2,4-bis(4- (tert-butyl)phenyl)-6-chloro-l,3,5-triazine left then the reaction was stopped, cooled down to room temperature and transferred to a separatory funnel. The aqueous layer was extracted with EtOAc and the combined organic layer was washed with water (200ml x 3) and brine (200ml x 2). It was then dried over MgS0 ₄ , evaporated to dryness and purified by silica column using 30% CH ₂ Cl ₂ /heptane as eluent giving pale yellowish liquid. The product was further purified and solidified by stirring in methanol and repeatedly precipitated from CH ₂ Cl ₂ /MeOH (13.5g, pale yellow powder, 99.5% HPLC, 51.5% yield). 1H-NMR (600MHz, CDCI3, TMS): S= 9.62 (s, 1H), 9.30(d, 1H), 8.7 (d, 4H), 8.17(d, 1H), 7.97 (d, 1H), 7.88(d, 1H), 7.81 (m, 2H), 7.68(s, 1H), 7.62 (d, 4H), 7.54(m, 1H), 7.41 (m, 1H), 7.32(m, 2H), 6.8 (m, 3H), 2.47(t, 4H), 1.96(s, 3H), 1.51 (m, 4H), 1.41 (s, 18H), 1.25(m, 12H), 0.83 (t, 6H).

I _r {4-(4,6-bis(4-(tert-butyl)phenyl)-lJ,5 riazin-2-yl)-l-(9-(3,5-dihexylphenyl)-9-methyl-9H- fluoren-2-yl)isoquinoline|2acac

In a 250ml three neck flask fitted with overhead stirrer, nitrogen inlet and condenser 4-(4,6- bis(4-(tert-butyl)phenyl)-l,3,5-triazin-2-yl)-l-(9-(3,5-dihe xylphenyl)-9-methyl-9H-fluoren-2- yl)isoquinoline (6.5g, 7.26mmol), IrC13.3H20 (1.02g, 2.90mmol), 2-ethoxy ethanol (70ml) and water (23ml) were taken. Nitrogen was bubbled through the reaction mixture for 1 hr then heated to 120°C for 16 hr before cooldown to room temperature. The solid was filtered, washed with water and dried in oven at 50°C under vacuum. The material was used for the next step without further purification. A 250ml three neck flask fitted with overhead stirrer, nitrogen inlet and condenser was charged with the material from previous step (6.5g, 2.96mmol), acetyl acetone (8.890g, 88.8mmol, 30 equivt) and 2-ethoxy ethanol (100ml). Nitrogen was bubbled through the reaction mixture for 1 hr then solid Na ₂ C0 ₃ (2.83g, 26.64mmol, 9 equivt) was added into the flask. The reaction mixture was heated to 120°C for 16 hr before cooldown to room temperature. Water (60ml) was added to precipitate the solid which was filtered, washed with water and dried in oven at 50°C under vacuum. The material was purified by silica gel column chromatography using 30% CH ₂ Cl ₂ /heptane as eluent. The main diastereomer was collected and further purified by precipitation from CH ₂ Cl ₂ /MeOH (1.56g, >99.5% HPLC).

1H-NMR (600MHz, THF-d ₈ ): S= 9.75 (s, 1H), 9.72(s, 1H), 9.67 (s, 1H), 9.66(s, 1H), 8.97 (m, 2H), 8.73(m, 8H), 8.23 (s, 1H), 8.19(s, 1H), 7.94 (m, 2H), 7.82(m, 2H), 7.61(m, 8H), 7.06(m, 14H), 6.75 (s, 1H), 6.73(s, 1H), 5.43 (s, 1H), 2.39(m, 8H), 1.82(m, 12H), 1.47(m, 8H), 1.37 (m, 36H), 1.2 (m, 24H), 0.83 (t, 6H), 0.79 (t, 6H).

Compound Example 2

Compound Example 2 was prepared according to Scheme 2:

AcOK, Dioxane

Scheme 2

1 ,3-dihexyl-5-iodobenzene

An oven dried 2L four neck flask fitted with nitrogen inlet, overhead stirrer and dropping funnel was charged with l-bromo-3,5-dihexylbenzene (50.0g, 153.69 mmol). Air was replaced with nitrogen for 30 min. Anhydrous THF (400ml) was added and the flask was cooled down to -78°C using dryice/acetone bath. A solution of n-BuLi (2.5M, 80.0 ml, 200mmol, 1.3 equivt.) was added dropwise over a period of 30 min and stirred for 1 hr at - 78°C. A THF solution (150ml) of iodine (50.71g, 200mmol) was added dropwise into the reaction mixture at -78°C then allowed to warm to room temperature and stirred for 16 hr. The reaction was quenched with aqueous sodium thiosulphate solution (200ml) then transferred to a separatory funnel. The aqueous layer was extracted with heptane and the combined organic layers were washed with water (200mlx2) and brine (200mlx2). It was then dried over MgS0 ₄ and concentrated to about 200ml then passed through a pad of silica and eluted with heptane. The solvent was evaporated and dried in oven at 50°C under vacuum (49.5g, 64% yield). GC-MS analysis shows it contains traces of starting bromide. The material was used for the next step without further purification. 1H-NMR (600MHz, THF-d ₈ ): δ= 7.34 (s, 2H), 6.92(s, 1H), 2.50(t, 4H), 1.56 (m, 4H), 1.2 (m, 12H), 0.88 (t, 6H).

2-bromo-9-(3,5-dihexylphenyl)-9H-carbazole

A 2L flask fitted with overhead stirrer and condenser was charged with l,3-dihexyl-5- iodobenzene (9.0g, 36.57mmol) and 2-bromocarbazole (27.23g, 73.14mmol, 2 equivt). O- xylene (370ml) was added and stirred. Nitrogen was bubbled through the suspension for 1 hr then KOH pellets (5.13g, 91.42mmol, 2.5 equivt) was added and stirred for 10 min. CuCl (1.08g, 10.9mmol, 0.3 equivt) was added followed by 1,10-phenanthroline (3.95g, 21.91 mmol, 0.6 equivt), a brownish cloudy solution obtained. The reaction mixture heated to 100°C for 1 hr then the rest of CuCl( 0.73g, 7.37mmol, , 0.2 equivt) and 1,10-phenanthroline (2.64g, 14.34 mmol, 0.4 equivt) were added. The temperature of the reaction mixture was increased to 140°C and heated for 20 hr. TLC showed no bromocarbazole remained. The reaction was allowed to coolto room temperature which resulted in the formation of a large amount of black precipitate. Water (300ml) was added and stirred for 10 min then transferred to a separatory funnel and allowed to separate. The aqueous layer was extracted with EtOAc and the combined organic layer was washed with water (200ml x2) and brine (200mlx2), dried over MgS04, evaporated to dryness, a brownish liquid which was purified by silica colulmn using heptane as eluent (17.05g, colorless oil, 99.75% HPLC, 95% yield).

1H-NMR (600MHz, CDC1 ₃ , TMS): δ= 8.10 (d, 1H), 7.98(d, 1H), 7.52 (d, 1H), 7.42(m, 1H), 7.37 (m, 2H), 7.29(m, 1H), 7.13 (m, 3H), 2.69(t, 4H), 1.68(m, 4H), 1.36(m, 12H), 0.90(t, 6H). 9-(3,5-Dihexylphenyl)-2-(4,4,5,5-tetramethyl-l,3,2-dioxaboro lan-2-yl)-9H-carbazole

In a 1L three neck flask fitted with nitrogen inlet and condenser 2-bromo-9-(3,5- dihexylphenyl)-9H-carbazole (17. Og, 34.66 mmol) and bis(pinacolato)diboron (9.68g, 38.12mmol, 1.10 equivt) were taken. Anhydrous dioxane (300ml) was added and nitrogen was bubbled through the solution for 30min. A suspension of dppf (0.58g, 1.04 mmol) and PdCi ₂ (dppf).CH ₂ Ci ₂ (0.85g, 1.04mmol) was added to the reaction mixture. Nitrogen bubbling was continued for another 30 min. Potassium acetate (10.20g, 103.97 mmol, 3.0 equivt) was added as solid and the reaction mixture was heated to 110°C for 16 hr, a pale brownish solution obtained. The reaction was stopped and cooldown to room temperature. It was then diluted with 200ml EtOAc and transferred to a separatory funnel and allowed to separate. The organic layer was washed with water (200ml x3) and brine (150ml ) and dried over MgS0 ₄ . The solvent was evaporated to dryness giving a pale brown liquid which was diluted with heptane and passed through a pad of celite/florosil (20g/20g) and eluted with heptane. Evaporation of solvent gives light yellowish liquid (17.08g, 99.4% HPLC, 92% yield).

1H-NMR (600MHz, CDC1 ₃ , TMS): S= 8.15 (m, 2H), 7.8(s, 1H), 7.73 (m, 1H), 7.40(m, 2H), 7.2 (m, 1H), 7.16(s, 2H), 7.10 (s, 1H), 2.69(t, 4H), 1.69(m, 4H), 1.37(m, 24H), 0.89(t, 6H).

2-(4-bromoisoquinolin-l-yl)-9-(3,5-dihexylphenyl)-9H-carb azole

In a 1L three neck flask fitted with nitrogen bubbler, overhead stirrer and condenser were taken 9-(3,5-Dihexylphenyl)-2-(4,4,5,5-tetramethyl-l,3,2-dioxaboro lan-2-yl)-9H-carbazole (17.08g, 30.94mmol), 1,4-dibromoisoquinoline (9.26g, 32.27mmol), toluene (170ml), t- BuOH (85ml) and THF (111ml). To this mixture 40% aq. solution of n-Bu ₄ NOH (80ml, 123mmol) was added followed by water (42ml). Nitrogen was bubbled through the reaction mixture for 1 hr. The catalyst, Pd(Ph ₃ P) ₄ (1.07g, 0.93mmol) was to the reaction mixture and heated to 50°C for 16hr. The reaction was stopped and transferred to a separatory funnel and diluted with 200ml of EtOAc and allowed to separate. The aqueous layer was extracted with EtOAc and the combined organic layer was washed with water (200ml x 3) and brine (200ml x 2). It was then dried over MgS0 ₄ , evaporated to dryness and purified by silica column using 40% CH ₂ Cl ₂ /heptane as eluent (16.2, 99.65% HPLC, 83% yield, pale brown oil).

1H-NMR (600MHz, CDC1 ₃ , TMS): S= 8.78 (s, 1H), 8.23(m, 4H), 7.81 (m, 1H), 7.71(s, 1H), 7.56 (m, 2H), 7.4(m, 2H), 7.32 (m, 1H), 7.21(s, 2H), 7.05 (s, 1H), 2.64(t, 4H), 1.62(m, 4H), 1.33(m, 4H), 1.24(m, 8H), 0.84(t, 6H).

9-(3,5-dihexylphenyl)-2-(4-(4^,5,5-tetramethyl-l,3,2-diox aborolan-2-yl)isoquinolin-l-yl)-

9H-carbazole

In a 1L three neck flask fitted with nitrogen inlet and condenser 2-(4-bromoisoquinolin-l-yl)- 9-(3,5-dihexylphenyl)-9H-carbazole (15.86g, 25.68 mmol), bis(pinacolato)diboron (7.17, 28.24mmol, 1.10 equivt) and potassium acetate (7.56g, 77.03 mmol, 3.0 equivt) were taken. Anhydrous dioxane (160ml) was added and nitrogen was bubble through the solution for 45min. A suspension of PdCl ₂ (dppf).CH ₂ Cl ₂ (0.630g, 0.77 mmol, 0.03 equivt) in dioxane was added into the reaction flask and nitrogen bubbling was continued for another 15 min. The reaction mixture was heated to 110°C, the progress of reaction was monitored by HPLC analysis and once no starting material left then it was stopped and cooldown to room temperature. It was then diluted with 150ml EtOAc and transferred to a separatory funnel. It was then washed with water (300ml x3) and brine (150ml x 2) and dried over MgS0 ₄ . Evaporation of solvent giving brown tar which was redissoved in toluene (100ml) and passed through a pad of celite/florosil (30g/ 50g) and eluted with 1L of toluene. Evaporation of the solvent gives light brownish oil (12g, 97% HPLC, 67% yield). The material was used for the next step without further purification.

1H-NMR (600MHz, CDC1 ₃ , TMS): S= 9.03 (s, 1H), 8.70(d, 1H), 8.23 (m, 3H), 7.17 (m, 2H), 7.49(m, 4H), 7.32 (m, 1H), 7.22(s, 2H), 7.03 (s, 1H), 2.63(t, 4H), 1.61(m, 4H), 1.44(s, 12H), 1.32(m, 4H), 1.24(m, 8H), 0.84(t, 6H).

2-(4-(4,6-bis(4-(tert-butyl)phenyl)-l,3,5-triazin-2-yl)is oquinolin-l-yl)-9-(3,5-dihexylphenyl)-

9H-carbazole

In a 1L three neck flask fitted with nitrogen bubbler, overhead stirrer and condenser 9-(3,5- dihexylphenyl)-2-(4-(4,4,5,5-tetramethyl-l,3,2-dioxaborolan- 2-yl)isoquinolin-l-yl)-9H- carbazole (l l.OOg, 14.54mmol), 2,4-bis(4-(tert-butyl)phenyl)-6-chloro-l,3,5-triazine (5.52g, 14.54mmol, 1.0 equivt), toluene (110ml) and 20% aq. solution of n-4NOH (42ml, 58.16mmol) was added. Nitrogen was bubbled through the reaction mixture for 1 hr. To the reaction mixture Pd(Ph ₃ P) ₄ (0.5g, 0.44mmol) was added and nitrogen bubbling was continued for another 15 min then heated to 70°C for 16hr. Sampling shows no starting materials left then the reaction was stopped, cool down to RT and transferred to a separatory funnel. The aqueous layer was extracted with EtOAc and the combined organic layer was washed with water (100ml x 3) and brine (100ml x 2). It was then dried over MgS0 ₄ , evaporated to dryness and purified by silica column using 30% CH ₂ Cl ₂ /heptane as eluent giving pale pale yellowish liquid. The product was further purified and solidified by stirring in methanol and repeatedly precipitated from CH ₂ Cl ₂ /MeOH (11.8g, pale yellowish powder, 99.49% HPLC, 81.5% yield).

¹ H-NMR (600MHz, CDC1 ₃ , TMS): S= 9.03 (s, 1H), 8.76(d, 1H), 8.22 (m, 4H), 7.70(m, 3H), 7.58 (m, 1H), 7.45(m, 4H), 7.31 (m, 1H), 7.25(m, 6H), 7.16 (m, 1H), 7.03(s, 1H),

2.63(t, 4H), 1.62(m, 4H), 1.44(m, 12H), 1.27(m, 18H), 0.84(t, 6H).

Ir|2-(4-(4,6-bis(4-(tert-butyl)phenyl)-lJ,5 riazin-2-yl)isoquinolin-l-yl)-9-(3,5- dihexylphenyl)-9H-carbazole|2 acac

In a 100ml three neck flask fitted with overhead stirrer, nitrogen inlet and condenser 2-(4- (4,6-bis(4-(tert-butyl)phenyl)-l,3,5-triazin-2-yl)isoquinoli n-l-yl)-9-(3,5-dihexylphenyl)-9H- carbazole (1.3g, 1.47mmol), IrCl ₃ .3H20 (0.24g, 0.67mmol), 2-ethoxy ethanol (25ml) and water (8ml) were taken. Nitrogen was bubbled through the reaction mixture for 1 hr then heated to 120°C for 16 hr before cooldown to room temperature. The solid was filtered, washed with water and dried in oven at 50°C under vacuum. The material was used for the next step without further purification.

A 100ml three neck flask fitted with overhead stirrer, nitrogen inlet and condenser was charged with the material from previous step (1.42g, 0.64mmol), acetyl acetone (1.92g, 19.21mmol, 30 equivt) and 2-ethoxy ethanol (40ml). Nitrogen was bubbled through the reaction mixture for 1 hr then solid Na ₂ C0 ₃ (0.61g, 5.76mmol, 9 equivt) was added into the flask. The reaction mixture was heated to 120°C for 16 hr before cooldown to room temperature. Water (50ml) was added to precipitate the solid which was filtered, washed with water and MeOH and dried in oven at 50°C under vacuum. The material was purified by silica gel column chromatography using 40% CH ₂ Cl ₂ /heptane as eluent. The product further purified by precipitation from CH ₂ Cl ₂ /MeOH (0.34g, 99.5% HPLC, 26% yield).

1H-NMR (600MHz, CDC13, TMS): S= 9.75 (s, 2H), 9.55(d, 2H), 9.03 (d, 2H), 8.72(d, 8H), 8.42 (s, 2H), 7.86(m, 2H), 7.72 (m, 2H), 7.56(m, 10H), 7.31 (s, 2H), 7.19(m, 8H), 7.04(s, 2H), 6.89(m, 2H), 5.40 (s, 1H), 2.60(t, 8H), 1.87(s, 6H), 1.70(m, 8H), 1.35 (m, 66H), 0.90 (t, 6H).

Device Examples

Devices having the following structure were prepared:

ITO / HIL (65 nm) / HTL (22 nm) / LEL (80-140 nm)/ Cathode in which ITO is an indium tin oxide anode; HIL is a hole-injection layer; HTL is a hole- transporting layer; and LEL is a light-emitting layer.

To form the device, a substrate carrying ITO was cleaned using UV / Ozone. The hole injection layer was formed by spin-coating an aqueous formulation of a hole-injection material and heating the resultant layer. The hole transporting layer was formed by spin- coating Hole-Transporting Polymer 1 and crosslinking the polymer by heating. The light- emitting layer was formed by spin-coating composition of Compound Example 1 (7.5 wt %) and Host 1, 2 or 3 (92.5 wt %) from toluene solution. The cathode was formed by evaporation of a first layer of sodium fluoride to a thickness of about 4 nm, a second layer of magnesium to a thickness of about 1 nm and a third layer of silver to a thickness of about 100 nm.

Hole Transporting Polymer 1 was formed by Suzuki polymerisation as described in WO 00/53656 of fluorene repeat units of formula (VIII); amine repeat units of formula (VI- 1); and crosslinkable repeat units of formula (VIII). Host 1 is the polymer "F8BT" formed by Suzuki polymerisation as described 00/53656 and having formula:

Hosts 2 and 3 are polymers that were formed by Suzuki polymerisation as described 00/53656 of the monomers set out in Table 1.

Table 1

A comparative device was formed by the same process except that Compound Example 1 was replaced with Comparative Compound 1 :

Comparative Compound 1

Device performance is summarised in Table 2, in which voltages, external quantum efficiencies and power density were measured at a current density of 50 mA/cm .

Table 2

Device 1 Compound 1

Device Host 1 Compound 11.1 1.10 0.92

Example 1 Example 1

Device Host 2 Compound 9.9 3.12 2.60

Example 2 Example 1

Device Host 3 Compound 11.07 8.02 6.67

Example 3 Example 1

In all cases, the exemplary devices require lower drive voltage and have higher efficiency and power density than Comparative Device 1 at the reference current density.

Although the present invention has been described in terms of specific exemplary

embodiments, it will be appreciated that various modifications, alterations and/or

combinations of features disclosed herein will be apparent to those skilled in the art without departing from the scope of the invention as set forth in the following claims.