WO2015136306A1 - Metal cluster complexes - Google Patents

Abstract

The present invention provides a metal cluster complex of formula (lla) having the formula [M₆Q₈L₆], optionally together with a counter ion, where each M is a metal atom selected from Re, Mo and W; each Q is independently selected from a halogen or chalogen atom; and each L is a ligand, and at least one ligand L is U, where L' has an aromatic group and a polymerizable functionality. Also provided is a polymerizable composition comprising the metal cluster complex of formula (lla) and a polymer obtained or obtainable from the polymerization of the polymerizable composition. Also provided is a method of generating light, the method comprising the steps of providing an octahedral metal cluster complex of formula (I), and applying an electric field across the metal cluster complex at a voltage of 5 V or more, to generate light from the cluster, wherein the cluster complex (I) has the formula [M₆Q₈L₆], optionally together with a counter ion, where each M is a metal selected from Re, Mo and W; each Q is independently selected from a halogen atom or a chaicogen atom; and each L is a ligand.

Description

Metal Cluster Complexes

Related Application The present application claims priority to and the benefit of GB 1404591.8 filed on 14 March 2014, the contents of which are hereby incorporated by reference in their entirety.

Field of the Invention The invention relates to octahedral metal cluster complexes for use as electroluminescent materials, methods for generating light using octahedral metal cluster complexes, and devices containing octahedral metal cluster complexes. The invention also relates to polymers and polymerizab!e compositions comprising octahedral metal cluster complexes, such as incorporating metal cluster complexes, and the use of the polymers as

electroluminescent materials.

Background

Organic light emitting diodes contain an organic material, such as a polymer, having electroluminescent properties. Thus, in response to an applied electric field that material emits light. Such device now found use in common commercial devices, such as televisions and computer displays.

Organic light emitting diodes have found favour owing to their relative ease of preparation, lower power requirements, quantum yield and the mechanical and oxidative stability of the materials used within the diode, amongst many other advantages.

Within the industry there is a need to provide new devices having improved optical properties.

As described herein, the present inventors have found that a device incorporating an octahedral metal cluster complex may be used to generate light.

Summary of the Invention

The present inventors have found that octahedral metal cluster complexes, such as those possessing an organic ligand, are capable of emitting light in response to an applied electric field. The inventors have therefore developed products incorporating these octahedral metal cluster complexes and methods for generating light from the octahedral metal cluster complexes. The inventors have found that the metai cluster complexes emit light at wavelengths that are useful for display devices. The light emission occurs at practical voltages and with relatively high efficiencies. The maximum emission occurs at voltages that are different to standard electroluminescent polymers. The incorporation or dispersion of the metal cluster complexes into such polymers therefore advantageously allows for the emission of light at two different voltages. Where the wavelength of the emitted light from the metal cluster complex and polymer differ, as is shown herein, there is the opportunity to use a single light emitting device to produce a variety of colours. In a general aspect, the present invention provides an octahedral metal duster complex having electroluminescent properties, light-emitting devices containing an electroluminescent octahedral metal duster complex, and the use of the octahedral metal duster complex in methods for the generation of light. Additionally, the invention provides a polymer incorporating an octahedral metal cluster complex, and a po!ymerizab!e composition comprising the octahedral metal cluster complex optionally together with one or more co- polymerizable monomers. in a first aspect of the invention there is provided a method of generating light, the method comprising the steps of

(i) providing an octahedral metal cluster complex of formula (I); and

(ii) applying an electric field across the metal duster complex of sufficient voltage, such as a voltage of 5 V or more, to generate light from the cluster.

The method provides for the electroluminescent generation of light.

In one embodiment, the metal cluster complex is in the solid state. Thus, the complex is not provided in solution.

The octahedral metal duster complex of formula (I) is [MeQsLe], where the cluster is neutral or charged. Each M is independently Re, Mo or W. Each Q is independently selected from a halogen atom or a chalcogen atom. Each L is a iigand, including those organic ligands described herein. Where the cluster is charged it may be provided together with suitable counter ions. in one embodiment, the metal cluster complex of formula (I) is dispersed in an

electroluminescent polymer or is incorporated into an electroluminescent polymer. Here step (ii) may comprise applying an electric field across the metal cluster complex and the electroluminescent polymer of sufficient voltage, such as a voltage of 5 V or more, to generate light from the cluster and light from the electroluminescent polymer. Accordingly there is provided a method for generating light, the method comprising the steps of: (i) providing a metal cluster complex of formula (I) dispersed in an electroluminescent polymer, or a metal cluster complex of formula (II) incorporated into an electroluminescent polymer;

(ii) applying an electric field across the metal cluster complex and the

electroluminescent polymer of sufficient voltage, such as a voltage of 5 V or more, to generate light from the cluster and light from the electroluminescent polymer.

The metal cluster complex of formula (I) includes complexes of formula (II). As described in further detail herein, the complex of formula (II) has a iigand with poiymerizabie functionality.

In a second aspect of the invention there is provided a light-emitting device comprising the metal cluster complex of formula (I) disposed between electrodes, optionally wherein the device is a solid state device. in a third aspect of the invention there is provided a metal cluster complex of formula (II), such as a metal cluster complex of formula (iia). The metal cluster complex of formula (II) is an octahedral metal cluster complex having at least one Iigand with a poiymerizabie group. The metal cluster complex of formula (Iia) is an octahedral metal cluster complex having at least one iigand with a poiymerizabie group and an aromatic group.

Also provided in a fourth aspect of the invention is a poiymerizabie composition comprising a metal cluster complex of formula (II) and optionally one or more co-polymerizab!e

monomers, such as a composition comprising a metal cluster complex of formula (II) and optionally one or more co-polymerizable monomers.

In a fifth aspect of the invention, there is provided a polymer obtained or obtainable from the poiymerizabie composition of the fourth aspect of the invention.

In a sixth aspect of the invention there is provided a method of preparing a polymer of the fifth aspect of the invention, the method comprising the step of polymerizing the

poiymerizabie composition of the fourth aspect of the invention

The metal cluster complex of formula (Iia), including the metal cluster complex of formula (Iia) incorporated into the polymer of the fifth aspect of the invention, may be provided in the product of the second aspect, disposed between two electrodes.

In a further aspect there is provided a method of generating light, the method comprising the steps of providing an octahedral metal cluster complex of formula (I) and applying an electric field across the metal cluster complex of sufficient voltage, such as a voltage of 5 V or more, to generate light from the duster. Summary of the Figures

Figure 1 is a schematic showing the preparation of metal duster complexes 1 and 2, and the incorporation of those clusters into a polymer

Figure 2 is a series of ¹H N R spectra for metal complexes of the invention, for complex 1 (top) and complex 2 (bottom).

Figure 3 is a series of GPC traces for the polymers of the invention.

Figure 4 is an emission spectrum for complex 1 and 2 as powdered samples, where the top spectral line is the emission for 2.

Figure 5 are emission decay profiles for 1 (top) and 2 (bottom) as powdered samples.

Figure 6 are emission spectra for complexes 1 (top) and 2 (bottom) as dichloromethane samples.

Figure 7 is a schematic of a light-emitting device of the invention.

Figure 8 is a series of JV curves for light-emitting devices according to an embodiment of the present invention.

Figure 9 is a series of electroluminescent spectra for the light-emitting devices according to an embodiment of the present invention.

Figure 10 is the emission spectra for powdered PVK and PVK incorporating 1 (1 @PVK) and 2 (2@PVK), at differing quantities of 1 and 2, from 5 to 100 mg of cluster per g of monomer, as denoted in the superscript.

Figure 1 1 is a series of emission spectra for powdered PS and PS incorporating 1 (1@PS, at top) and 2 (2@PS, at bottom), at differing quantities of 1 and 2, from 5 to 100 mg of cluster per mL of monomer, as denoted in the superscript. Figure 12 is a series of emission spectra for powdered PMMA and PMMA incorporating 1 (1 @PMMA, at top) and 2 (2@PMMA, at bottom), at 10 mg of cluster per mL of monomer for 1 , and from 10 to 150 mg of cluster per mL of monomer for 2, as denoted in the superscript. Figure 13 is a pair of JV curves for fabricated light-emitting devices according to an embodiment of the invention, where the top JV curve Figure 14 is a series of emission spectra for fabricated light-emitting devices according to an embodiment of the invention, where the top spectrum. Also shown to the right of the spectra are images of the respective devices. Figures 4 to 6 and 10 to 12 are emission spectra showing the change in absorbance

(normalised intestity) with change in wavelength.

Detailed Description of the invention The present inventors have established that octahedral metal cluster complexes possess electroluminescent properties. Such properties are believed to be unrecognised in the art. The present invention therefore exploits the ability of an octahedral metal cluster complex to emit light in response to an applied electric field. Accordingly, the present invention provides methods for the generation of light from an octahedral metal cluster complex as a response to an applied electric field. The present invention also provides devices, particularly electrical devices, incorporating the metal cluster complex, which devices are used to generate light.

Octahedral metal cluster complexes are known in the art, and the photoluminescent properties of these clusters are known. Typically the octahedral metal cluster complexes emit red or near-infrared light. The quantum yields are often more than 0.5.

Molard et a/., Dorson et al. and WO 2011/064139 ail describe metal cluster complexes having photoluminescent properties. These documents do not describe the emission of light from a metal cluster complex in response to an applied electric field. in further aspects of the present case, the inventors have found that the octahedral metal cluster complexes may be dispersed or incorporated into a polymer, and light may be generated from such polymers in response to an applied electric field. The polymer may itself be a may be an electroluminescent polymer.

Molard et al. describe the preparation of polymers incorporating an octahedral metal cluster complex. However, there is no suggestion that the metal cluster complex, either alone, or incorporated into the polymer, has electroluminescent properties. The metal cluster complexes of Molard ef al. find use in some aspects of the present invention.

The present inventors have provided octahedral metal cluster complexes that have advantages over the octahedral metal cluster complexes of Molard ef a/. The inventors have noted that the clusters containing methyl methacryiate ligands have poor solubility in organic solvents. As such, it is difficult to process the metal cluster complex, for example it is difficult to incorporate the methyl methacryiate-containing cluster into a polymer. Thus, in certain aspects and embodiments, the invention relates to metal cluster complexes that are distinguished over the metal cluster complexes of Molard et al.

Mussell et al. (Inorg, Chem, 1990, 29, 3711) describe the electrogenerated

chemi!uminescence of hexanuclear molybdenum and tungsten clusters. The complexes described here are limited to those having exclusively halogen iigands, and organic ligands are not suggested for use. There is no mention of Re clusters. There is no suggestion that the complexes could or should be incorporated into a polymer or dispersed in a polymer. There is no suggestion that the complexes could or should be used in a device, such as a solid state device. The electrochemicai methods described are apparently limited to cyclic voltammetry only, where the clusters are retained in solution.

Nocera et al. (J. Am. Chem. Soc. 1984, 106, 824) describe the electrochemical reduction of o(li) halide clusters and the electrogenerated chemiluminescence of a MoeC!u species. As with the article above, the electrochemicaily active complex has halogen iigands only.

Chemiluminescence is not electroluminescence.

Octahedral Metal Cluster Complex

The octahedral metal cluster complexes for use in the invention are electroluminescent. The ability of a cluster to emit light in response to an applied electric field may be established using the techniques described herein. Broadly a metal cluster complex refers to an octahedral transition metal cluster complex having six metal atoms. The metal atoms are provided in the cluster in the form of a rigid core, [ ₆Q8]^m+, where is a metal atom and Q is independently selected from a halogen atom or a chalcogen atom. The metal cluster complex may be a 24 electron cluster. The metal atoms in the cluster may be Re, W and Mo.

The metal cluster complex may emit light in response to an applied voltage of 5 V or more, such as 8 V or more, such as 9 V or more.

The light emitted by the cluster in response to an applied electric field may include light having a wavelength in the visible range, such as light having a wavelength in the range 390 to 700 nm.

In light emitted by the cluster in response to an applied electric field may include light having a wavelength in the range 600 to 800 nm, such as 650 to 750 nm.

The present invention provides the use of metal cluster complexes of formula (I). A metal cluster complex of formula (I) may be a metal cluster complex of formula (II) or formula (iia), such as described below. Metal clusters of formula (I) have useful electroluminescence properties, and the cluster complexes may be used to generate light at useful wavelengths in the visible range, such as red light. The clusters may also be usefully incorporated or dispersed within polymers, such as transparent polymers, for use in a light emitting device. The clusters have an

electroluminescence response at useful voltages. Advantageously, the metal clusters may be incorporated or dispersed within electroluminescent polymers. Thus, the application of an applied field to the polymer, with the cluster present, produces an electroluminescent response from both the polymer and the metal cluster. The electroluminescent response may occur at different applied voltages, and the emission maxima for the polymer emission and the metal cluster emission may be different. This provides the opportunity to emit different coloured light from the polymer (containing the cluster) in response to a change in voltage. This is shown in the worked examples of the present case.

The metal cluster complex (I) is represented by the general formula [MeQe ], where the cluster is neutral or charged. Each M is independently Re, Mo or W. Each Q is

independently selected from a halogen atom or a chalcogen atom. Each L is a ligand, including those organic iigands described herein.

The group Q is an inner, face capping ligand in the cluster. The group L is an apical, terminal ligand in the cluster.

The eight Q groups in the cluster may be the same, or they may be a mixture of different halogen and/or chalcogen atoms.

in one embodiment, each Q is selected from S, Se, Te, i, CI and Br.

in one embodiment, each M is Re.

in one embodiment, each Q is selected from S and Se. In one embodiment, each Q is S or Se.

In one embodiment, at least one L is different to each Q.

In one embodiment, each L is different to Q.

A ligand L may be an inorganic or organic ligand. In one embodiment, at least one ligand L is not an inorganic ligand. in one embodiment, at least one ligand is not halogen, in one embodiment, at least on ligand is an organic ligand. An inorganic ligand may be selected from the group consisting of halogen (CI-, F^", Br, and CN-, SCN-, OCN-, N₃-, HO^" and H₂0.

An organic ligand may be an aromatic or aliphatic compound having suitable functionality for binding to a metal, such as carboxylate, oxy and sulfonate functionality. Organic groups having N-donor atoms are also suitable for use. An example includes a nitrogen-containing heteroaromatic ligand.

In one embodiment, the metal cluster is not [MoeClu]^2". In one embodiment, the metal cluster is not [MoeClu]^2", [W3CI14]^2", [W₆li4]^2", [WsClsBre]²-, and [WelsBre]^2".

For example, the organic ligand is an aromatic or aliphatic compound having functionality selected from the group carboxylate, sulfonate, phosphine, thiocarboxylatephosphine oxide, thiophosphine oxide, phosponate, thiophosphonate, phosphinic acid, nitrile, isocyanates, thiocyanate amide, thioamide, hydroxy, thiol, thiolate, optionally esters, optionally thioesters, sulfinic acid, arsine, arsine oxide, thioarsine oxide, arsinate, thioarsinates, arsinic acid, stibines, stibine oxides, thiostibine, antimonate, thioantimonate, stibinic acids

An organic ligand is a ligand containing an organic group such as an alkyl group and/or an aromatic group. Typically, the organic ligand has 2 or more carbon atoms, such as 3 or more carbon atoms, such as 4 or more carbon atoms, such as five or more carbon atoms, in one embodiment, an organic ligand has an aromatic group, such as a benzene group or a pyridine group. In one embodiment, four ligands may be organic ligand having an aromatic

A ligand may be a pyridine-containing ligand, such as an alkyl pyridine.

In one embodiment two of the six ligands L may be hydroxyl ligands. The remaining four ligands may be organic ligands.

in one embodiment each ligand L is an organic ligand.

Metal cluster complexes of formula (I) include metal cluster complexes known in the art, including, for example, the clusters described by Dorson et a/., Moiard et a!. and WO

2011/084139. However, the electroluminescent properties of the clusters are not described or suggested in this earlier work. Hence, the present inventors now provide for the use of such clusters, and others, in the generation of light, for example upon application of an applied electric field. it is noted that WO 20 1/064139 identifies b,vo octahedral metal complexes having photoluminescent properties. Thus, in response to an incident light having a wavelength in the range 300 nm to 550 nm, the clusters emit light having an emission maximum at 735 or 745 nm. This is not electroluminescence. Similarly, Moiard et al. describe the phosphorescence of a cluster. Here, incident light having a wavelength in the range 300 to 550 nm results in the emission of light having a emission maximum at 7 0 nm. Again, this is not electroluminescence, in one embodiment, the metal cluster complex contains two ligands L and U, where the total number of L and U is six.

Each L and U may be selected from the ligands described above, in on embodiment, L and U are different. Here, each L may differ, and each U may differ, so long as no L is the same as U. In one embodiment, the metal cluster complex has four ligands of one type L, and two ligands of type L\ Here, the metal cluster complex may be represented by the general formula [MeQsUL'a].

In one embodiment, the metal cluster complex has five ligands of one type L, and one ligand of another type L\

A ligand L^' may be a ligand as defined above for the ligands L. As described below, the ligand U may be a ligand having polymer!zab!e functionality. In one embodiment, U is a ligand comprising a polymerizable functional group, such as a vinyl group (-CH=CH2) or an ally! group

Clusters of this type are clusters of formula (II). The ligand U may also include an aromatic group, which is linked to the polymerizable functional group. Clusters of this type are Clusters of formula (Ha). The compounds of formula (II) and (lla) may be usefully incorporated into a polymer and such may be used within a light emitting device. in one embodiment, the ligand U comprises an aromatic group and a polymerizable functionality.

It is noted that WO 2011/084139 describes metal cluster ligands comprising aromatic groups. It is said that the aromatic groups may be linked via a linker and that linker may include functionality such as an ethylene group, among many other groups. WO

2011/084139 does not exemplify such compounds, and it is not clear how they should be prepared, and it is not dear how such ethylene functionality would be available for reaction in a polymerizable composition.

In the compounds of formula (lla) the polymerizable functionality must be available for reaction in a polymerizable reaction. Thus, the polymerizable functionality may be provided at a terminal of the ligand, which would locate the functionality at the outer edge of the metal cluster complex, available for reaction. In the present case the ethylene functionality is typically provided as a terminal group, such as a vinyl group.

Accordingly, in one aspect of the invention there is provided a metal cluster complex of formula (II), where the metal cluster complex is represented by the general formula

[MeQeUL^], which may be neutral or charged. Each M is independently Re, Mo or W. Each Q is independently a halogen atom or a chalcogen atom, as described above. Each L is a ligand, including those organic ligands described herein, and each U is a ligand having a polymerizable functional group optionally together with an aromatic group, such as benzene.

Where the metal cluster complex is provided with two ligands L' it will be appreciated that the metal cluster complex may be used as a crosslinker in a polymerizable composition to crosslink polymer stands. This is shown schematically in Figure 1 for a metal cluster complex of the invention.

In the clusters of formula (II), each and each Q is as discussed above for the clusters of formula (I). Each L in the cluster of formula (II) may be as discussed above for the clusters of formula (I).

The ligand U comprises a connecting group for linking the polymerizable functional group to a metal atom of the cluster, for example via an aromatic group.

The ligand U may be connected to a metal M atom through an oxygen atom of the ligand. The oxygen atom is or is part of the connecting group of the ligand L'. Examples of connecting groups include -COO-* (carboxy), -0-* (oxy) and -S(0)20-* (sulfonate), where the asterisk indicates the point of attachment to the metal atom. In one embodiment, the connecting group may be provided as a substituent to an aromatic group of the ligand L'. In this embodiment, it is preferred that the ring atoms of the aromatic group that are ortho to the connecting group are unsubstituted.

In addition to the connecting groups described above, the connecting group may be selected from the group consisting of phosphine, thiocarboxylatephosphine oxide, thiophosphine oxide, phosponate, thiophosphonate, phosphinic acid, nitrile, isocyanates, thiocyanate amide, thioamide, hydroxy, thiol, thiolate, optionally esters, optionally thioesters, sulfinic acid, arsine, arsine oxide, thioarsine oxide, arsinate, thioarsinates, arsinic acid, stilbines, stiibine oxides, thiostilbine, antimonate, thioantimonate, and stiibinic acids. Such functionality may be provided as a substituent to the aromatic group of the ligand L'. in this embodiment, it is preferred that the ring atoms of the aromatic group that are ortho to the connecting group are unsubstituted.

The ligand U may be connected to a metal through a nitrogen atom of the ligand. The nitrogen atom may be present as a ring atom on an aromatic group. For example, the nitrogen may be provided in a pyridine. Thus, the connecting group may be represented (-N*=, where the asterisk indicates the point of attachment to the metal atom).

The ligand U may be connected to a metal through an oxygen or sulfur atom of the ligand. The sulfur atom may be present as a ring atom on an aromatic group. For example, the sulfur may be provided in a furan or thiophene. Thus, the connecting group may be represented (-0*- or -S*-, where the asterisk indicates the point of attachment to the metal atom). The ligand U may be connected to a metal M through a phosphorus atom of the ligand. A connecting group, where present, may be linked to a polymerizable functional group directly or via a linker. A connecting group, where present, may be linked to an aromatic group directly or via a linker. Linkers are described in further detail below. In one embodiment, the Iigand includes an aromatic group. Such ligands are present in the clusters of formula (Ha). This aromatic group may be a carboaryl group, such as a

Ce-14 carboaromatic group, or a heteroaromatic group, such as a C5-14 heteroaromatic group. in one embodiment, an aromatic group is a carboaromatic group, such as a Ce- or

Ce-io carboaromatic group.

In one embodiment, a carboaryl group is benzene or naphthalene, such as benzene. in one embodiment, an aromatic group is a heteroaromatic group, such as a C5-10 or C5-7 heteroaromatic group.

in one embodiment, a heteroaromatic group is pyridine, quinolone or isoquinoline, such as pyridine.

The aromatic group may contain one ring or two or more fused rings, where at least one ring, such as each ring, is aromatic.

The aromatic group is linked to the polymerizable functionality. Where a connecting group is present, the aromatic group is also linked to the connecting group. The polymerizable functionality may link to the connecting group via the aromatic group. As explained in further detail below, the aromatic group may be linked directly to the polymerizable functionality or may be linked via a linker group. in the present case, the term link may be given to mean covalently linked, such as by a covalent bond or via a covalent linker group. The Iigand L^' is provided with polymerizable functionality. Such functionality is suitable for reaction in a polymerization reaction. The functionality may be suitable for forming a polymer selected from the group consisting of a polyethylene (particularly substituted polyethylene), polyacetylene (particularly substituted polyacetylene), polyester, poiyamide, polyurethane, polyanhydride, and polysiloxane.

In one embodiment, the polymerizable functionality is for the formation of substituted polyethylene, for example polystyrene.

The polymerizable functionality may be suitable for forming a polyethylene, particularly substituted polyethylene. Here, the polymerizable functionality is an ethylene group

(>C=C<), including a vinyl group (-CH=CH2), a methyl vinyl group -CH=CH(CH3), a dimethyl vinyl group (-CH=C(CH3)2). The vinyl groups may be part of an ailyl group (e.g.

The ethylene group is suitable for reaction in a polymerizable composition further comprising a monomer having an ethylene group.

The ethylene group may be may be selected from the group consisting of a vinyl group, an alkyl vinyl group (such as methyl vinyl group a dimethyl vinyl group), a vinyl ether group (-OCH=CH2), an alkyl vinyl ether group (such as methyl vinyl ether,

a vinyl halide group (-CH=CH(Hai)), a vinyl ester group (-C(0)OCH=CH₂), an alkyl vinyl ester group (such as -C(0)OCH=CH(CH3)), an acrylate group (-OC(0)CH=CH₂), an aikyiacrylate group (such as methacryiate, -OC(0)C(CH₃)=CH₂), an alkyl acrylate group (such as methyl acrylate

and an alkyl aikyiacrylate group (such as methyl

methacryiate -OC(0)C(CH₃)=CH(CH₃)). in the monomers above the reference to alkyl may be a reference to Ci-e alkyl, such as

Ci-4 alkyl, such as methyl or ethyl, such as methyl.

The ethylene group, such as groups discussed above, may be directly connected to the aromatic ring.

In one embodiment, the polymerizable functionality is a vinyl group or an alkyl vinyl group, such as a methyl vinyl group.

The polymerizable functionality may be suitable for forming a polyacetylene. Here, the polymerizable functionality may be an ethylene group that is provided within a cyclic ring, such as a cycioaikenyi group (optionally for reaction with a monomer having an ethylene group that is provided within a cyclic ring). Polyacetyienes are typically formed by ring opening metathesis reactions.

The polymerizable functionality may be suitable for forming a polyester. Here, the polymerizable functionality is a diol (for reaction with a diacid monomer), or a diacid (for reaction with a diol monomer) or the functionality includes a hydroxy! group and a carboxy! group (optionally for reaction with a monomer having a hydroxy! group and a carboxy! group).

The po!ymerizabie functionality may be suitable for forming a polyamide. Here, the polymerizable functionality is a diamine (for reaction with a diacid monomer), or a diacid (for reaction with a diamine monomer) or the functionality is an amino acid (optionally for reaction with a monomer having amino acid functionality).

The polymerizable functionality may be suitable for forming a po!yurethane. Here, the polymerizable functionality is a dio! (for reaction with a diisocyanate monomer), or a diisocyanate (for reaction with a diol monomer). Where the polymerizable functionality is suitable for forming a polyurethane, it is preferred that the ligand includes diol functionality. The polymerizable functionality may be suitable for forming a polysiloxane. Here, the polymerizable functionality is a disilanol (optionally for reaction with a monomer having disilanol functionality),

The cycloalkenyl, dioi, diacid, diamine, disilanol, diisocyanate, hydroxyl, carboxyl and amino acid groups may be directly connected to the aromatic ring.

The aromatic group is optionally further substituted. In one embodiment, the aromatic group is optionally substituted with one or more substituents selected from the group consisting of halo, -OH, -COOH, -S(0)20H, C1-30 aikyi, and C1-30 alkoxy, C1-30 acyl, C1-30 oxyacyl and C1-30 carboxy where one or more methylene groups in the alkyl group is optionally replaced with a group independently selected from -0-, -C(O)-, -S-, -C(0)0-, -C(0)NH-, an aromatic group, or a cycloaikyiene group, and the aikyi group is optionally substituted with one or more substituents selected from the group consisting of halo, -OH, -COOH, -S(0)₂OH.

The aromatic group may also be provided with additional polymerizable functionality. Such functionality may be used to crosslink a polymer or may be the location for the later functionalization of a prepared polymer, e.g. as a site for grating a further polymer.

A ligand L' may include one or more aromatic groups. In one embodiment, U has one aromatic group.

A ligand U may be provided with a linker to link the polymerizable functionality to the aromatic group. Alternatively, the polymerizable functionality may be directly connected to the aromatic group.

The ligand U may be provided with a linker to link the aromatic group to the connecting group, where present. Where the polymerizable functionality includes two functional groups (e.g. a diol or diacid) a single linker may connect the aromatic group to these functional groups. Alternatively, each functional group may be independently connected to the aromatic group by a separate linker. In one embodiment, a linker is a C1-30 alkylene group, wherein one or more methylene groups is optionally replaced with a group independently selected from -0-, -C(O)-, -S-, -C(0)0-, -C(0)NH-, an aromatic group, or a cycloaikyiene group, and one or more hydrogen atoms in the alkylene group is optionally replaced with halo. The aromatic group in a linker, where present, is in addition to the aromatic group that is required in the linker of formula (II). The aromatic group of the linker may be selected from those aromatic groups that are listed above. For example, aromatic group of the linker may be benzene.

The cycloalkylene group of the linker may be selected from C*-? cycloalkylene, such as cyclohexene. in one embodiment, a ligand U may be represented thus:

-CG-L-Ar-L-PF where CG is a bond or a connecting group and the asterisk is the point of attachment to a metal M; each L is a linker as described above or a covalent bond; Ar is an optionally substituted aromatic group, such as a carboaromatic group or a heteroaromatic group, and PF is a polymerizable functionality. Where CG is a bond, L is also a bond and the aromatic group is provide with suitable functionality for attachment to a metal atom, for example a nitrogen aromatic ring atom.

Typically each L' is the same. In some embodiments, the ligands L' may differ. The two ligands L' may be arranged cis or trans to the other four ligands L, In one embodiment, the two ligands L^" are arranged trans. The present inventors have found that clusters having a very high proportion of the trans isomer may be prepared. In the worked examples clusters are prepared where the trans isomer makes up more than 95% of the product material. In contrast, the work of Dorson et a!. describes metal cluster complexes where the trans isomer is present only at ca. 90% of the product material. The work of

Moiard et al. describes the metal cluster complexes where the trans isomer is present only at ca. 80% of the product material.

The synthesis of products having a high trans content minimises the need for multiple successive recrystallization steps to purify the product. In the present case, the amount of cis isomer present is sufficiently low as to allow the reaction product to be used without further purification. in one embodiment, the metal cluster complex is a neutral cluster.

Where a cluster is charged, suitable counter ions may be provided.

In one embodiment, the metal cluster complex of formula (I la) is [MeQeUL^], where each M is Re, each Q is S or Se, each L is 4-alkylpyridine, such as 4-fe/f-butylpyridine, and each U is as defined above. In one embodiment each U is

where the asterisk indicates the point of attachment to the metal atom. In one embodiment, the groups *-OC(0)- and

are arranged para (1 ,4-substituted) about the aromatic ring. In one embodiment, a ligand L is a ligand L\

Preparation of Metal Complexes

Octahedral clusters of formula (I) are known in the art, and may be prepared using the techniques described in, for example, Dorson et a/., Molard ef al. and WO 2011/064139.

The compounds of formula (II) may be prepared, for example, by the methods described by Dorson et al. and Molard ei al Thus, the compounds of formula (II) may be prepared from a cluster [MeQe OH^]. This cluster may be reacted directly with an appropriate compound ligand U to form the cluster of formula (II). The ligand may be connected to the metal via a ligand oxygen, nitrogen or phosphorus atom. Thus, the compound used in the reaction may have a group -COOH, -OH, or -S(O ₂0H, thereby to form a carboxy, oxy or sulfonate connection to the metal.

Additionally or alternatively a ligand U is provided with a nitrogen atom or phosphorous atom.

The compounds of formula (iia) may be prepared by adapting the methods described above, such as described in the worked examples.

Light-Emitting Device The metal cluster complex of formula (I) may be included within a light-emitting device. The metal cluster complex may be provided for the generation of light from an applied electric field. Accordingly, the metal cluster of formula (I) is disposed between electrodes of the device, such as cathode and anode electrodes. In one embodiment, the light-emitting device is an organic light-emitting device. Thus, the device includes an organic material, such as organic compounds and/or polymers that are suitable for generating light and/or are conductive.

The device is provided with a suitable power supply for applying a voltage across the metal cluster complex. The power supply is able to provide a voltage suitable for generating an electroluminescent response from the metal cluster complex.

In one embodiment, the metal cluster complex is not provided in solution. The electrodes and the metal cluster complex may together form a solid-state device. The metal cluster complex (I) may be provided in a layer of material that is disposed between the electrodes of the device. The metal cluster complex may be dispersed in a polymer, such as an electroluminescent polymer, for example a PVK polymer (polyvinyl carboazole)).

The metal cluster complexes of formula (II) may be incorporated into a polymer, such as described herein. The polymer itself may be provided between the electrodes.

The layer containing the metal duster complex may be multi-layered, with the metal cluster complex contained in at least one layer ("the emission layer")- Other layers may be provided, including a conductive layer and a coupling layer, as is common in the art.

The conductive layer, where present, may be provided on the anode, for example between the anode and the layer containing the metal cluster complex. The conductive layer is a conductive polymer layer. Such conductive layers are well known.

in one embodiment, the conductive layer is or comprises PEDOT:PSS (poly(3,4- ethyienedioxythiophene) poly(styrenesulfonate)).

The coupling layer, where present, may be provided on the cathode, for example between the cathode and layer containing the metal cluster complex. in one embodiment, one electrode of the device is transparent to visible light, in one embodiment, one electrode is at least transparent to red light, such as light in the range 650 to 750 nm.

One electrode, such as the anode, may be an indium tin oxide (ITO) electrode. The other electrode, such as the cathode, may be the same or different. In one embodiment, the other electrode is an aluminium or aluminium-containing electrode. An electrode may have a thickness of at most 1 ,000 nm, at most 500 nm, at most 200 nm or at most 100 nm. An electrode may have a thickness of at least 10 nm, at least 20 nm or at least 50 nm.

Where the metal cluster complex is provided in a layer between two electrodes, the thickness of the metal duster complex-containing layer may be at most 1 ,000 nm, at most 500 nm, at most 200 nm, at most 100 nm or at most 60 nm. The thickness of the metal cluster complex-containing layer may be at least 10 nm, at least 20 nm or at least 40 nm. Where the metal cluster complex layer is provided alongside other layers, such as conductive and coupling layers, the thickness of the metal cluster complex layer may refer to the thickness of the layer containing the metal cluster complex and not the total thickness of ail the layers between the electrodes. An electrode is present, such as a transparent electrode, may be provided as a iayer on a substrate, such as a transparent substrate, such as a glass substrate. The substrate may provide structural stability to the device and provides a base from which electrode layers and metal cluster complex-containing layers may be built. Where a transparent electrode is present, this may be provided on a transparent substrate.

The substrate may have a thickness of at most 5 mm, at most 2 mm, at most 1 mm or at most 0.5 mm.

The substrate may have a thickness of at least 0.1 mm or at least 0.2 mm.

The light-emitting device may be optionally provided with a power supply in electrical connection with the electrodes. in a further aspect there is provided an optical product comprising a light-emitting device of the invention which is suitable for emitting light at a first wavelength in the visible range, such as a wavelength in the range 600 to 800 nm, such as 650 to 750 nm, together with a second light-emitting device suitable for emitting light at a second wavelength in the visible range, which second wavelength is different to the first wavelength. Optionally a further

light-emitting device is provided, which device is suitable for emitting light at a third wavelength in the visible range, which third wavelength is different to the first and second wavelengths. Wavelength may be taken as the wavelength of the emission maximum.

The second and third light-emitting devices may be light-emitting devices of the invention or they may be alternative devices, including LEDs such as OLEDs.

In one embodiment, the light-emitting device of the invention emits light in the red region of the visible spectrum, for example in the range 600 to 800 nm. The second device and the third device may be suitable for emitting light in the green and blue regions of the visible spectrum. Such a combination may be used as an RGB display. in a further aspect there is provided an optical product comprising a plurality of light-emitting devices of the invention. The light-emitting devices may be provided as an array.

The optical product may be a screen, such as a television, computer or telephone screen, for example.

The light-emitting devices according to the invention may be prepared using standard techniques for the preparation of organic light-emitting diodes (OLEDs). For example, standard spin coating techniques may be used to deposit a Iayer of cluster-containing material (such as a polymer as describe herein) onto the surface of an electrode or the surface of a conductive Iayer. Methods of Light Generation

The inventors have found that compounds of formula (I) emit light in response to an applied electric field. The metal cluster complexes of the present invention are therefore suitable for use in electroluminescent methods.

The method of the invention may be suitable for the generation of red light or near-infrared light. Thus, the light has a wavelength selected from the range from 600 to 2,500 nm, such as from the range 600 to 800 nm, such as 650 to 750 nm. In one embodiment the emission maximum is located in the range from 600 to 2,500 nm, such as from the range 600 to 800 nm, such as 650 to 750 nm in one embodiment, the light is not monochromatic.

Accordingly, the present invention provides a method of generating light, the method comprising the steps of providing an octahedral metai cluster complex of formula (I) and applying an electric field across the metal cluster complex of sufficient voltage, such as a voltage of 5 V or more, to generate light from the cluster. The metai cluster complex of formula (I) may be disposed between electrodes which are suitable for applying an appropriate voltage across the metal cluster complex. in one embodiment, the voltage is 5 V or more, 8 V or more, or 9 V or more,

in one embodiment, the voltage is at most 15 V, at most 12 V or at most 1 1 V. It has been found that higher voltages, such as those above 11 V, may lead to the degradation of the device into which the cluster is incorporated. Thus, voltages below 11 V are preferred.

In the methods of light generation, a light-emitting device as described above may be used. Thus, the electrodes may be used to supply an electric field across the metal cluster complex that is provided between the electrodes.

The electrochemical properties of metal cluster complexes have previously been studied. For example olard et a/, describe the electrochemical analysis of a methyl methacryiate- containing octahedral metal cluster complex. However, the experiments described are cyclic voltammetry analyses of the metal cluster complex. There is no suggestion that the voltages used were in any way sufficient to elicit an electroluminescent response. The reported oxidation step for the dissolved octahedral metal cluster complex is located at 0.76 V vs SCE, far below the voltages required to elicit an electroluminescent response from the complex. Indeed, the authors do not report an electroluminescent response. Thus, the electroluminescent properties of octahedral metal cluster complex of formula (I) are unrecognised in the art. In the methods of the present case, the methods of light generation make use of a metal complex that is not provided in solution. Typically, the metal complex is provided in a Iayer of material (such as a polymer Iayer) which is disposed between electrodes. In one embodiment, the metal complex is provided in a solid state device.

The methods of the invention also provide for the generation of light at two different wavelengths using a single light-emitting device. The clusters of formula (I) are found to emit red light in response to an applied voltage in the region of 10 V. The cluster may be incorporated into or dispersed in an electroluminescent polymer, such as PVK. The electroluminescent polymer may emit light at a different wavelength and optionally in response to a different applied voltage to that of the metal cluster complex. For example, PVK emits light having a maximum emission at a wavelength of ca. 465 nm in response to an applied voltage in the region of 9 V, Accordingly there is provided a method for generating light having, the method comprising the steps of:

(i) providing a metal cluster complex of formula (I) dispersed in an electroluminescent polymer, or a metal cluster complex of formula (II) incorporated into an electroluminescent polymer;

(ii) applying an electric field across the metal cluster complex and the

electroluminescent polymer of sufficient voltage, such as a voltage of 5 V or more, to generate light from the cluster and light from the electroluminescent polymer. in one embodiment, the applied voltage in step (ii) may be altered.

In one embodiment, the light emitted from the metal cluster complex has an emission maximum that is different to the light emitted from the electroluminescent polymer.

In other aspects of the invention, there is provided the use of a metal cluster complex or a polymer of the invention as an electroluminescent material. in one embodiment, the method comprises the steps of:

(i) providing a metal cluster complex of formula (I) dispersed in an electroluminescent polymer, or a metal cluster complex of formula (II) incorporated into an electroluminescent polymer, such as a polymer obtained or obtained by the methods described herein;

(ii) applying an electric field across the polymer at a first voltage of 5 V or more, to generate light from the polymer; and

(ii) applying an electric field across the polymer at a second voltage of 5 V or more, which voltage is different to the first voltage to generate light from the polymer. in one embodiment, the light emitted in response to the first voltage has an emission maximum that is different to the emission maximum of the light emitted in response to the second voltage. In one embodiment, the first and second voltages differ by at least 0.25 V, at least 0.5 V, at least 1.0 V, or at least 1.5 V. Polymenzable Composition

The metal cluster complex of formula (II) may be provided in a polymenzable composition. The polymenzable composition may be used to prepare a polymer of the invention. In one embodiment, the metal cluster complex is a metal cluster complex of formula (ila)

According to one aspect of the invention, the polymenzable composition comprises the metal cluster complex of formula (II) optionally together with one or more co-polymerizable monomers. In one embodiment, the polymenzable composition comprises the metal cluster complex of formula (II) and one or more co-polymerizable monomers. Optionally, the polymenzable composition further comprises one or more of catalysts, crosslinking agents and polymerisation initiator, such as known to a person of skill in the art.

The present inventors have found that the metal cluster complexes of formula (lia) have excellent solubility in organic solvents, including for example chlorobenzene. As such, the metal cluster complexes of formula (Ila) are readily useable in a polymenzable composition, in contrast, the inventors have found that the methacrylate-containing dusters of

olard et al. do not have good solubility, and the processing of these clusters in a

polymerizable composition is not easy. Without wishing to be bound by theory, the inventors believe that the presence of additional aromatic functionality in the metal cluster complex is sufficient to increase the solubility of the metal cluster complex in organic solvents. More generally, an increase in the organic content of the metal cluster complex is believed to be helpful in this way. A metal cluster complex of formula (II) may be provided without other co-poiymerizabie monomers. This is less preferred. Typically, the polymerizable composition comprises one co-polymerizable monomer, and optionally more than one co-polymerizable monomer.

A co-polymerizable monomer is suitable for reaction with the metal cluster complex of formula (II) in a polymerization reaction.

Described above are suitable functionalities for reaction with the polymerizable functionality of the ligand, A co-polymerizable monomer possesses functionality that is suitable for reaction with that polymerizable functionality, for example in a radical polymerization reaction. Suitable functionality is discussed above in relation to the polymerizable

functionality. The co-polymerizable monomer (or monomers) may together with the metal cluster complex of formula (II) be suitable for forming a polymer that is selected from the group consisting of a polyethylene (particularly substituted polyethylene), polyacetylene (particularly substituted polyacetylene), polyester, polyamide, polyurethane, polyanhydride, and polysiloxane.

In one embodiment, the co-polymerizab!e monomer (or monomers) may together with the metal cluster complex of formula (II) be suitable for forming a polyethylene (including substituted polyethylene). Thus, where the metal cluster complex includes a ligand U having an ethylene group, the co-polymerizable monomer is also provided with an ethylene group.

In one embodiment, a co-polymerizab!e monomer has an ethylene group, including a substituted ethylene group.

In one embodiment, the ethylene group of the co-polymerizable monomer is selected from the group consisting of a vinyl group, an alkyl vinyl group, a vinyl ether group, an aikyi vinyl ether group, a vinyl haiide group, a vinyl ester group, an aikyi vinyl ester group, an acrylate group, an alkylacrylate group, an alkyl acrylate group, and an alkyl alkylacryiate group, in one embodiment, the ethylene group of the co-polymerizable monomer is a vinyl group. in one embodiment, the co-polymerizable monomer (or monomers) is a monomer that, when polymerized, yields a transparent polymer. A transparent polymer may refer to a polymer that is transparent to visible light, such as light in the range 390 to 700 nm, in the present case, the inventors have demonstrated the use of the metal duster complexes with polymers prepared from methyl methacrylate, styrene and N-vinyi carbazole monomers. The polymers prepared from these monomers are known to have excellent transparency. in one embodiment, the co-polymerizable monomer is selected from the group consisting of methyl methacrylate, styrene and N-vinyl carbazole. The metal cluster complex is typically provided at a low wt % and/or moi % with respect to the total amount of co-polymerizable monomers present in the poiymerizab!e composition. Thus, the polymer that is obtained from the polymerizabie composition has the gross characteristics of the polymer obtained from the co-polymerizable monomers. In one embodiment, the metal cluster complex is provided in the polymerizabie composition in an amount that is at most 5 %, at most 2 %, at most 1 %, or at most 0.5 % with respect to the total amount of polymerizabie monomers present.

In one embodiment, the metal cluster complex is provided in the polymerizabie composition in an amount that is at least 0.01 %, at least 0.05 %, or at least 0.1 %.

The % value may refer to the wt % or the mole %. In one embodimeni, the polymerizable composition comprises a polymerization initiator. The polymerization initiator is selected based on the nature of the polymerizable functionality in the metal cluster complex and the co-polymerizable monomers. The polymerization initiator may be a heat- or light-initiated polymerization initiator,

For example, the polymerization initiator may be a radical generator, such as for use in the polymerization of ethyiene-containing monomers. For example, the polymerization initiator is A!BN. In one embodiment, the polymerization initiator is provided in the polymerizable composition in an amount that is at most 5 %, at most 2 %, at most 1 %, or at most 0.5 % with respect to the total amount of polymerizable monomers present.

In one embodiment, the polymerization initiator is provided in the polymerizable composition in an amount that is at least 0.01 %, at least 0.05 %, or at least 0.1 %.

The % value may refer to the wt % or the mole %.

Other components may be present in the polymerizable composition to optimise the physical and chemical properties of the formed polymer, or to assist in the processing of the formed polymer material. For example, crosslinkers may be provided to increase the crossiinking between polymer strands. Catalysts may be provided to control the stereochemistry and tacticity of the form polymer product. Mold release agents may also be present to assist the removal of the formed product from the mold. The use of such components is commonplace and well known to those of skill in the art. in one embodiment, the polymerizable composition is provided as a solution in an organic solvent, such as chiorobenzene.

Polymer The present invention provides a polymer incorporating the metal cluster complex of formula (II), such as a polymer incorporating the metal cluster complex of formula (iia). Here, the metal cluster complex is incorporated into the backbone of the polymer.

The polymer is obtained or obtainable from the polymerizable composition of the invention, using such techniques as are familiar to those of skill in the art. Thus, the polymer is obtained by the polymerization of a polymerizable composition as described herein. in one embodiment, the polymerization of the polymerizable composition is performed at elevated temperature, for example at a temperature above 30°C, above 50°C, above 60°C. The polymer may be analysed by standard methods, including IR, DSC, GPC, Tg and NMR to determine the properties of the polymer and the presence of the metal duster complex within the polymer. In one embodiment, the Tg value of the polymer is at least 80, at least 90, or at least 100°C. Tg is recorded as described in the worked examples.

Also provided by the present invention is a metal complex of formula (I) that is dispersed in a polymer. Here, the metal cluster complex is not incorporated into the backbone of the polymer. Rather the metal complex is mixed with the polymer. A polymer having a metal complex dispersed within it may be used as a layer of material in the light-emitting device of the invention. in one embodiment, the metal cluster complex of formula (I) is dispersed in a mixture of polymers. in one embodiment, the metal complex of formula (I) is dispersed in a polymer that is an electroluminescent polymer. Such a polymer is capable of emitting light in response to an applied electric field. Polymers of this type are known in the art and find use in

OLED-containing devices. Thus, both the dispersed metal complex and the polymer emit light in response to an applied electric field. In one embodiment, the polymer is selected from poly(N-vinyi carbazole), poiy(p-phenylene vinyiene) and polyfiuorene. in one embodiment, the polymer is transparent to visible light. Thus, the polymer is transparent to light having a wavelength in the range 390 to 700 nm.

Additional and Alternative Embodiments

As described above, the complexes of formula (I) emit light in response to an applied electric field. Conversely, the present inventors have established that the complexes described herein may find use in photovoltaic devices, thus the complexes of formula (I) may be used to develop an electrical current in response to light incident upon the complex.

Accordingly, in a further aspect of the invention there is provided a photovoltaic device, such as a solar cell or a solar concentrator, comprising a metal cluster complex of formula (I). The metal cluster complex may be a complex of formula (II), such as a complex of formula (I la).

Alternatively, there is provided a photovoltaic device, such as a solar ceil or a solar concentrator, comprising a polymer that is obtained or obtainable from a polymerizable composition comprising the metal cluster complex of formula (II), optionally together with a co-poiymerizable monomer. The metal cluster complex may be a complex of formula (Ha). As used herein, a reference ΐο a photovoltaic device may be a reference to a device comprising a semiconductor material. The complex may be, or may be provided within, a semiconductor material, it follows that the complexes described herein may find use in methods of light harvesting, for example where the complexes are used to convert incident light to electrical current within a photovoltaic device, such as a solar cell or a solar concentrator. In a further aspect of the invention there is provided a method for the generation of electrical current, the method comprising the steps of:

(i) providing a photovoltaic device, such as the device described above;

(ii) exposing the photovoltaic device to light, such as sunlight, thereby to generate an electrical current within the solar cell.

Without wishing to be bound be theory, the present inventors believe that the complexes of the invention provide a contribution to charge transport and charge percolation within a photovoltaic device. The complex (I) or a polymer obtained or obtainable from the complex (II) may be provided as a layer within the photovoltaic device. The complex or polymer may be evenly dispersed throughout the layer, or the complex or polymer may be provided in regions within the layer, that are separated from other regions of the complex or polymer. Other Embodiments

Each and every compatible combination of the embodiments described above is explicitly disclosed herein, as if each and every combination was individually and explicitly recited. Various further aspects and embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure.

"and/or" where used herein is to be taken as specific disclosure of each of the two specified features or components with or without the other. For example "A and/or B" is to be taken as specific disclosure of each of (i) A, (ii) B and (iii) A and B, just as if each is set out individually herein.

Unless context dictates otherwise, the descriptions and definitions of the features set out above are not limited to any particular aspect or embodiment of the invention and apply equally to ail aspects and embodiments which are described. Certain aspecis and embodimenis of the invention wili now be illustrated by way of exampie and with reference to the figures described above.

Experimental

Materials

Tra/7s-Re₆Q8(TBP}4(OH)₂ was obtained according to the earlier work of Dorson ef al. and Moiard ef al. Ail other reactants were purchased from either Fisher or Aldrich. Styrene and methyimethacry!ate were purified from inhibitors by washing with 2 M NaOH solution and dried over magnesium sulphate. AIBN and N-vinylcarbazole were reerysta!!ized twice from methanol. Other reactants were used as received. Dialysis tubing (Mw cut-offs 3500 and 7000 D) were purchased from Mediceli Ltd.

Instrumentation:

NMR spectra were recorded on a Bruker Avance 300 NMR spectrometer equipped with a solution-state dual channel probe working at 300.13 MHz for ¹H and 75 MHz for ¹³C. NMR spectra were measured in CDC (5H = 7.26, 5c = 77.16) in standard way using zg30 pulse programm for ¹H and waitz16 pendant pulse program for ¹³C. MS analysis of compounds 1 and 2 was conducted using WATERS Micromass LCT (ESI) mass spectrometer in methanol in presence of Nal. Elemental analyses were obtained from Euro Vector EA3000 Elemental Analyser. FTIR was recorded on Bruker Vertex 80 as KBr pellets. Absorption spectra of 1 were recorded in diapason 300-700 nm on a PerkinElmer Lambda35 UV/Vis spectrometer. The thermal transition temperatures were determined under N2 atmosphere using a Mettler Toledo DSC 1 differential scanning calorimeter. The heating and cooling rates were kept at 20°C/min, the samples weight: 4.0 to 8.0 mg. Indium was utilized as reference for calibrating the temperature. Tg was estimated to be the midpoint temperature of the endothermic baseline shift. Polymer molecular weights (M„) were determined using gel permeation chromatography (GPC) using a degassed THF eluent system containing 2% TEA and 0.05% (w/v) BHT through three PL gel 5 μητι 300 x 7.5 mm mixed C columns. The system, operating at 40°C with the eluent flow rate of 1 mL min^-1, was calibrated against narrow polystyrene standards (M ranged from 162 to 6,035,000 g moh¹).

Photoluminescence Measurements

For emission measurements, the powdered samples of the complexes trans- [Re6Q8(TBP)₄(VB)2] (Q = S or Se) and the cluster co-polymers based on them were placed between two non-fluorescent glass plates. The absorbance of dichioromethane solutions of fra/7s-[Re6Qe(TBP)4(VB)2] was set < 0.1 at 355 nm. The solutions were poured into quartz cuvettes. For deaeration, an Ar-gas stream was purging through the solutions for 30 min and then the cuvettes were sealed. Measurements were carried out at 298 K. The samples were excited by 355-nm laser pulses (8 ns duration, LOTIS Til, LS-2137/3). Corrected emission spectra were recorded on a red-light-sensitive multichannel photodetector

(Hamamatsu Photonics, P A-11). For emission decay measurements, the emission was analyzed by a streakscope system (Hamamatsu Photonics, C4334 and C5094). The emission quantum yields ( em) for the solutions were estimated by using [Ru(bpy)3](PFe)2 as a standard: <t>em = 0.095 in deaerated acetonitrile [K. Suzuki, A. Kobayashi, S. Kaneko, K. Takehira, T. Yoshihara, H. Ishida, Y. Shiina, S. Oishic and S. Tobita, Phys. Chem. Chem. Phys., 2009, 11, 9850-9880]. The emission quantum yields of the powdered samples were determined by an Absolute Photo-Luminescence Quantum Yield Measurement System

(Hamamatsu Photonics, C9920-03), which comprised an excitation Xenon light source (the excitation wavelength was set at 380 nm), an integrating sphere, and a red-sensitive multichannel photodetector (Hamamatsu Photonics, PMA-12). Table 1 - Emission Decay - Powdered Samples

Table 2 - Emission Decay - Dichloromethane Solutions

Sample iem / nm r_em / μ8 (A)

(relative quantum yield)

Aerated solution:

τ-ι = 4,8 (0.55) Aerated solution: τ₂ = 1.9 (0.45) 0.023

[Re₆S₈(TBP)₄(VB)₂] - 710

Deaerated solution: Deaerated solution: τ = 18.8 (0.80) 0.075 T2 = 5,9 (0.20)

Aerated solution:

xi = 8.5 (0.85) Aerated solution: 12 = 3,5 (0.15) 0.049

[Re₆Se₈(TBP)₄(VB)₂] ~ 710

Deaerated solution: Deaerated solution: xi = 17.7 (0.65) 0.095 τ₂ = 9.5 (0.35) Electroluminescence Measurements For the fabrication light-emitting devices films of the active layer, i.e. ¹⁰@PVK hybrid materials in combination with PBD and TPD were spin-coated onto glass substrates covered with ITO electrodes (100 nm) from dichlorobenzene in two combinations: 1) 5 mg/mL of 1¹⁰@PVK, 2.5mg/mL of PBD and 1 mg/mL of TPD; and 2) 4 mg/mL of copolymerized cluster, 2 mg/mL of PBD and 0.8 mg/mL of TPD. The prepared films were dried in air at 120<C before further processing and characterisation. The thicknesses of the films were around 40 nm as determined by profilmeter Dektak measurements. The ITO substrates were cleaned just before the deposition of the organic layer by washing with acetone,

1-isopropanol, 2 % heimanex solution in water and deionised water. The 0.7 nm thick layer of LiF was deposited by evaporation onto the active layer. Finally, 100 nm-thick Al cathodes were prepared by evaporation. The electrical characteristics were measured by multimeter Keithley 2401. The electroluminescence spectra were recorded with SpectraScan 655. The emission was found to be uniform throughout the area of each device.

Light-Emitting Devices

Several light-emitting devices were prepared with clusters falling within the general formula (I). The general structure of the device is shown in Figure 7.

The glass substrate, 1 mm thick, was obtained with a pre-patterned 100 nm ITO layer on its upper surface. The ITO layer was plasma treated in order to polarize the surface and to smooth the upper surface. PEDOT:PSS (Heraeus GmBH, 4083) was filtered then spin-coated onto the upper surface of the ITO layer to a thickness of about 50 nm. Onto the upper surface of the PEDOT: PSS layer was spin coated to a thickness of 40-60 nm an active layer as described below. Onto the upper surface of the active layer was deposited a layer of LiF (0.7 nm) then a layer of Al (100 nm). These upper two layers were deposited by evaporation.

The active layer was prepared from the following solutions: Sample X1 : PVK 2.5 mg/mL, PBD 1.25 mg/mL, TBD 0.5 mg/mL Re₆Se₈(TBP)₄(OH)2 10 mg/mL in CB;

Sample X2: PVK 2.5 mg/mL, PBD 1.25 mg/mL, TBD 0.5 mg/mL Re₆Se₈(TBP)₄(OH)₂ 20 mg/mL in CB;

Sample X3: PVK 5 mg/ml, PBD 2.5 mg/mL, TBD 1 mg/mL Re₆Se₈(TBP)4(OH)₂40 mg/mL in CB;

Sample X4: PVK 0 mg/mL, PBD 5 mg/mL, TBD 2 mg/mL Re₆Se₈(TBP)4(OH)₂40 mg/mL in CB; Sample X5: PVK 5 mg/mL, PBD 2.5mg/mL, TBD 1 mg/mL Re₆Se₈(TBP)4(OH)220 mg/mL in CB;

where PBD is 2-(biphenyl-4-yl)-5-phenyl-1 ,3,4-oxadiazole), TBD is N,N -Bis(3- methylphenyl)-N,N -diphenylbenzidine) and CB is chlorobenzene.

The JV curves for each device are shown in Figure 8.

The electroluminescent spectra of the OLEDs X1 , X4 and X5 were taken with a SpectraScan 855. They are shown in Figure 7.

General Synthesis of Clusters

Two clusters of the type irans- Re6Q8(TBP)4(VB)2 were prepared, where Q = S (cluster 1) or Q = Se (cluster 2), TBP is 4-ferf-butyipyridine and VB is 4-vinyl benzoic acid.

Tra/?s-Re₆Q8(TBP)4(OH)₂ (0.20 mmol) was dissolved in 30 mL of chlorobenzene by sonication. Then 4-vinyl benzoic acid (2.70 mmol) was added to the solution. The reaction mixture was heated at 90°C for 48 hours. The solvent was removed under reduced pressure. The obtained solid was washed 3 times with diethyl ether (30 mL) in an ultrasound bath and separated by centrifugation. The product was collected as a fine powder and dried under vacuum.

Cluster 1 : Yield: 96%. Elemental analysis (%): Found N 2.5, C 29.0, H 3.1 ; Calculated for C₅4H66N₄04Re6S8: N 2.5, C 29.4, H 3.0; δ H: 9.39 (8H, d, J = 6.5 Hz, 4*H ortho pyridine),

8.12 (4H, d, J = 8.2 Hz, 2*H2 vinyl benzoate), 7.39 (4H, d, J = 8.2 Hz, 2*H3 vinyl benzoate), 7.21 (8H, d, J = 6.5 Hz, 4^*H meta pyridine), 6.75 (2H, dd, J = 10.6, 7.0 Hz, 2*CH), 5.79 (2H, d, J = 17.5Hz, 2*CHH), 5.26 (2H, d, J = 1 1.1 Hz, 2*CHH), 1.27 (36H, s, 12*CH3); δ C: 30.22, 35.28, 1 14.5, 121.8, 126,1 , 130.3, 134.1 , 136.9, 139.4, 160.9, 164,4, 174.2; ESI-MS (+) Found for [Na-1]+: 2235.0.

Cluster 2: Yield: 92%. Elemental analysis (%): Found: N 2.2, C 25.4, H 2.7; Calculated for C₅4H66N404Re₆Se8: N 2.2, C 25.1 , H 2.6; δ H 9.65 (8H, d, J =6 .6 Hz, 4*H ortho pyridine), 8.09 (4H, d, J = 8.3 Hz, 2^*H2 vinyl benzoate), 7.49 (4H, d, J = 8.3 Hz, 2*H3 vinyl benzoate), 7.09 (8H, d, J = 6.6 Hz, 4*H meta pyridine), 6.75 (2H, dd, J = 10.7, 6.6 Hz, 2*CH), 5.79 (2H, d, J = 17.4Hz, 2*CHH), 5,26 (2H, d, J = 10,6 Hz, 2*CHH), 1.26 (36H, s, 12*CH3); δ C: 30.26, 35.26, 1 14.3, 122.0, 125.5, 130,1 , 135.0, 137,0, 139.2, 160,9, 164.4, 172,8; FT!R: ESI-MS (+) Found for [Na-2]+: 2607.2: Calc. 2607.1. Synthesis and Characterisation of Clusters

Complexes of the type [Re6Qs(TBP)4(VB)2] were obtained according to an adaptation of a recently developed synthetic approach, in which neutral complex irans-[Re₆Q8(TBP)4(OH)2] is treated by an excess of a relevant carboxyiic acid to allow the metathesis between two hydroxyl-groups of the cluster complex and corresponding carboxyiate anions of the vinyiic compounds. Thus, treatment of fra/is-[Re6G8(TBP)4(OH)2] (Q= S or Se) with an excess amount of 4-vinylbenzoic acid in chiorobenzene, heated for 2 days, gave the neutral complexes [Re6Q₈(TBP)4(VB)2j (Q = S (1), Se (2)) (Scheme 1) with yields of over 90% after precipitation in and washing by diethylether.

As expected, upon coordination of VB, the signals from aromatic ring protons are shifted in the lower field in the ¹ H N R spectra in comparison with the free acid form, ¹H NMR also showed that during the reaction some trans to c/^'s isomerisation occurred producing less than 5% of cis-isomers (Fig S). Such unusual isomerisation was reported earlier for the cluster [Re₆Q₈(TBP)4( AC)2] (MAC = methacrylate anion). Though the detailed mechanism of the isomerisation is not established, it is assume that during the reaction OH groups are protonated, which is followed by the elimination of H₂0 producing a reactive species with only five outer ligands. At this stage the trans to c/s isomerisation can happen, if one of TBP ligands changes its position.

The isomers were not separated in view of the very low percentage of c/s isomers in the products.

Data obtained by ESi- S spectroscopy also confirmed the formation of 1 and 2. Namely, in the positive area of mass-spectra molecular peaks that correspond to [Re₆Qs(TBP)4(VB)2] were observed together with their dissociation daughter species [ReeGsC BPHVB^] and [Re₆Q₈(TBP)4(VB)]+. Elemental analysis data of 1 and 2 were in a good agreement with the formula compositions proposed above, and supported by NMR and ESI-MS analysis.

The product complexes were further characterized by FTIR spectroscopy. FTIR spectra of 1 and 2 show several changes in comparison with the spectra for the vinyl benzoic acid and cluster starting material. For the product clusters there are two distinct bands at 1314 and 1299 cm^-1 that correspond to vs(COO) in carboxyiate groups. These bands are slightly shifted from those of 4-vinylbenzoic acid (1334 and 1298 cm^-1), at the same time the stretching vibration C=0 of the free acid (1684 cm ¹) disappears. Further, v(C=0) is not observed as a defined band in the infrared spectra of the products, as it most likely coincides with a band 1615 cnr¹ that is present in the complex fra/?s-Re6Q8(TBP)4(OH)2, which is associated with the ring stretching vibrations for te/t-buthyl pyridine. Among octahedral complexes of Moe, We and Ree there are examples of complexes with aromatic carboxylic acids are described in literature. These include the earlier work of Dorson et al, describing relative compounds frans-ReeSsi BP iL"^ (where L" is

3,4,5-trimethoxybenzoic acid or its derivative, i.e. gallate like derivatives), in which a very similar vibration band around 1615 cm ¹ was assigned to vibrations (C=0), shifted as a result of coordination to the cluster complex. In that work, however, the overlap of these vibrations with those from aromatic ring stretching is not mentioned. In other work describing complexes (nB^NM oeBrsL'^] with similar L" acid anions, infrared spectroscopy showed (C=0) to be shifted from 1684 cm^-1 to 1630 cm^-1. This also follows the general tendency for u(C=0) from coordinated COO to show up at lower wave numbers and therefore agrees well with the assumption made for clusters 1 and 2.

T_g Measurements it was note that there was little change in Tg when the clusters were incorporated

(co-po!ymerised) into the polymer. This is expected: the amount of clusters in the polymerizable composition and therefore the polymer is relatively low.

General Synthesis of Polymers

Polymers were prepared from a polymerizable composition comprising a cluster 1 or 2 together with methyl methacry!ate, styrene or polyvinylcarbazole.

Test tubes were charged with chlorobenzene, in which monomer (1 % v/v M A, or 1 % v/v styrene or 1 % w/v N-vinyicarbazole, relative to solvent) and either duster 1 or 2 (0.25-10% wt/wt % (for PVK system) or wt/v % (for P A and PS systems) - relative to monomer) were fully dissolved by ultrasound. AIBN (1 mol %) was added to the reaction mixture. The tubes were sealed with a rubber septum and degassed by purging with nitrogen for 30 min. The polymerisation reactions took place over 18 h. (PMMA), 24 h. (PS) or 72 h. (PVK) at 70°C. Finally, the chlorobenzene was evaporated and polymers were dissolved in toluene and precipitated in methanol. All polymers were additionally purified by dialysis in toluene.

Preparation of Cluster Co-Polymers In contrast to the earlier reported polymerizable complex irans-[Re6Se8(TBP .(MAC)2], compounds 1 and 2 have relatively good solubility of up to 15 mg/mL in chlorinated solvents and therefore they can be easily co-polymerised with organic monomers using solution based techniques. This also allows co-polymers with a higher content of the Re cluster to be obtained compared to the previously known Re cluster-containing co-polymers. Clusters 1 and 2 were used to prepare soluble photo- and electroluminescent polymers based on PM A, PS and N-PVK polymers. The photo- and electro-physical properties of these polymers are described below (see also Figure 1). Several samples of polymers with various contents of clusters were obtained by free radical copolymerization reactions of 1 or 2 (0-0.015 w/v of A or styrene; 0, 0.5, 1 , 2, 10 wt % N-PVK) with the corresponding monomers dissolved in dissolved 10-fold excess of chlorobenzene and initiated by AIBN (1 mol % corresponding to a monomer). Chlorobenzene was chosen as the solvent due to its high boiling temperature and ability to dissolve 1 and 2, but also due to its non-coordinating nature, which means complexes 1 and 2 are not likely to be destroyed during the polymerization reaction. The maximum amount of the complexes was finally limited to 0,010 (wt/wt % for PVK system, wt/v % for PMMA and PS systems) as the products containing higher load of the cluster had low solubility due to the higher level of cross-linking. The time of reaction at 70°C was set as 18 h. for PMMA, 24 h. for PS and 72 h. for N-PVK, as after this time, both GPC and NMR showed only trace amount of the monomer remained, i.e. substantially full conversion had occurred. The polymer products were evaporated and dissolved in toluene giving clear coloured solutions, precipitated in methanol, and the PMMA and PS-based polymers were additionally purified by dialysis in toluene.

To show that the vinyibenzoate ligands do take part in co-polymerisation reaction, a control experiment was performed using 5 wt % fra/7s-ReeS8(TBP) (OH)2 instead of cluster 1 in copolymerization with MMA. The reaction product, after dissolution, did not provide a clear solution in either toluene or THF. The ¹H NMR of the precipitate coincided with that of the starting material, frans-Re₆S8(TBP)4(OH)₂.

Characterization of Co-Polymers

Obtained organic polymers containing complexes 1 and 2 with concentrations up to 10% (w/v for PMMA and PS polymers and w/w for PVK) show good solubility in relevant organic solutions including those in which starting cluster compounds are not soluble (e.g. THF, toluene). That shows both the successful copoiymerisation of complexes 1 and 2 with the polymerizable monomers, as well as that the level of crosslinking obtained by the solution polymerization method is not significant enough to produce highly cross-linked insoluble polymers.

The co-polymers were characterised by GPC using THF as an eiuent. The obtained data (Figure 3 and Table 3) show that the average molecular weight M_n and the molecular weights distribution of the co-polymers (containing complexes 1 or 2) are close to those determined for the reference PMMA, PS and PVK polymers. There is, however, a clear (almost linear) tendency for polymers with the higher loads of complexes to have higher molecular weights.

The IR spectra for the reference P MA, PS and PVK polymers and the co-polymers were quite similar due to the low molar concentration of the complexes in the samples. In the aromatic region of ¹H NMR spectra, however, the signals of the aromatic protons from the pyridine ligands coordinated to the cluster complex were clearly observable. Also observable was the signal for the fe/f-butyl group at 1.19 ppm. As expected, these signals were stronger in samples with higher load of complexes in the polymer samples.

Differential scanning calorimetry (DSC) and TGA measurements were performed on all samples. The results indicate that the introduction of the complexes had a limited effect on the thermal properties of the polymers, as well as general molecular mass of the polymer. Namely, T_g for all duster containing samples are close to those detected for the reference neat polymers. Similarly, the molecular weights (M_n) and molecular weight distributions determined by GPC were also close to that of the reference samples.

Table 3 - Thermal data and molecular masses of co-polymer samples

Molar cluster

concentration

Sampie Mn kD

fmoie %} (°C)

x 10

1¹⁰@P A 0.5 90 24.3

2¹⁰@P A 0.4 110 23.8

2¹²-⁵@P MA 0.5 127 23.7

2²⁰@PMMA 0.8 109 24.5

2³⁰@P MA 1.2 110 23.3

2⁴⁰@P MA 1.6 110 26.4

2¹⁰⁰@Ρ Α 4.1 - 19.8

PMMA^Ref 0 11 1 22.8

1⁵©PS 0.3 100 10.5

1¹⁰@PS 0.5 104 9.5

1²⁵@PS 1.3 119 1 1.6

1¹⁰⁰@PS 5.2 100 9.0

2⁵@PS 0.2 96 1 1.7

2¹⁰@PS 0.4 83 1 1.8

2²⁵@PS 1.1 80 10.9

2¹⁰⁰@PS 4.4 107 8.9 pgRef - 110 1 1.5

1⁵@PVK 0.4 227 26.1 Molar cluster

concentration Tg

Sample M_n kD

(mole %) (°C)

x 10

1¹⁰@PVK 0.9 229 29.4

1²⁰@PVK 1.7 227 30.3

1 ⁰⁰@PVK 8.7 235 25.3

2⁵@PVK 0.4 233 28.2

2¹⁰@PVK 0.7 230 28.6

2²⁰@PVK 1.5 237 28.8

2¹⁰⁰@PVK 7.4 228 26.2

p_{V K}Ref - 222 33.4 where a sample is represented by n^x@PM where n refers to the presence of cluster 1 or 2 in the polymer, x refers to content of the cluster (mg) per 1 mL (for A and styrene) or per 1 g (for vinyicarbazole) of the monomer material, and PM refers to the type of the organic polymer e.g. polystyrene, PS. ^Ref refers to a polymer prepared without the duster present.

Characterisation of Phoiophysicai Properties: The normalised emission spectra of complexes 1 and 2 in the solid state and in solution are shown in Figures 4, 5 and 6, whilst the emission maximum wavelengths ( _em), quantum yields ( ¾_m), and lifetimes (r_em) are summarised in Tables 1 and 2 above. Luminescence of compound 1 was studied in the solid state and in both aerated and deaerated

dichloromethane solutions. Shapes of the emission spectra of the aerated and deaerated solutions are identical, however the deaerated solution is characterised by a slightly higher quantum yield and a longer lifetime than the aerated one (Table 2). This difference is readily explained by the fact that luminescence of hexarhenium complexes is well known to be quenched efficiently by oxygen. Altogether, the observed photophysicai parameters of 1 and 2 are in excellent accord with other complexes based on the {ReeQs}²⁺ cluster core.

To enable the rational development of rhenium cluster-containing materials it is important to understand the impact that the incorporation of the cluster into a polymer (in this particular case co-polymerisation of the cluster's outer ligands with co-monomers to obtain the final polymer) has on the photophysicai properties of these incorporated clusters. The work herein shows that powdered samples of the polymers incorporating 1 and 2 have similar emission profiles to 1 and 2 in the region 550-900 nm (see Figures 10-12 and Tables 4 and 5).

The emission quantum yields and excited state life times for the polymers incorporating 1 and 2 are slightly higher than those for powdered samples of 1 and 2 and similar to those found for diaerated solutions of 1 and 2. This observation clearly indicates the strong shielding effect that the polymer matrices PS and P MA confer against oxygen quenching of the photo!uminescence emission associated with the {ReeQs} cluster core.

These data also signify that during the polymerisation reaction the complexes fully retain their photoiuminescent properties and their chemical unity, i.e. no significant change in chemical environment around the duster cores occurs. This is in a good agreement with the proposed reaction scheme, in case of PVK system two emission maxima in the spectra have been observed that are associated with the fluorescence of PVK (420 nm) and the phosphorescence of the cluster units (-710 nm).

Table 4 - Emission Decay - PMMA Polymers Incorporating 1 or 2

where a sample is represented by n^x@PMMA where n refers to the presence of cluster 1 or 2 in the polymer, x refers to the amount, in mg, of the duster per 1 mL of the monomer material (MMA), and PMMA refers to the type of the organic polymer i.e.

poly(methyl methacrylate). Table 5 - Emission Decay - PS Polymers Incorporating 1 or 2

where a sample is represented by n^x@PS where n refers to the presence of cluster 1 or 2 in the polymer, x refers to the amount, in mg, of the cluster per 1 mL of the monomer materia! (styrene), and PS refers to the type of the organic polymer e.g. polystyrene.

Electroluminescent Properties of Polymers

PVK is known for its use in OLEDs, with typical working voltages in the range 5-7 V [see, for example, www.sigmaaidrich.com/catalog/product/aldrich/368350]. In the present case the hybrid material 1¹⁰@PVK was evaluated for use in an OLED. The structure of OLEDs that were fabricated is presented at the Figure 7, where two various compositions of active layer were used. The addition of PBD and TPD into active layer was important for improving charge carrier transport. PBD is widely as an electron transport layer, and TPD as a hole transport layer.

The JV curves of both devices (Figures 13) show that the working voltage of the fabricated devices coincides with those reported for other PVK based OLEDs. The electroluminescent spectra of the devices recorded at voltages from 6-1 1 V show two distinctive emission peaks associated with emission of PVK, having an emission maximum at 465 nm, and a broad signal between 650 nm and 750 nm associated with the Re duster (see Figure 14).

The overall emission intensity of the devices is at its highest when the voltage applied is between 8-9 V, A voltage increase to above 1 1 V leads to the degradation of the device and a decline in the electroluminescent intensity. The data also show that the intensities of the cluster or the PVK polymer (into which the cluster is incorporated) do not change evenly with the increase of the voltage. Namely, with the increase of voltage the emission intensity of PVK increases to reach its maxima at 9 V, while the incorporated cluster reaches its maxima at 10 V. For the device with the active layer 2 the maximal emission was achieved at 8 V. At the same time the respective intensities between PVK and cluster complex sub-systems do not show constancy in dependence to voltage applied, i.e. at lower voltages, emission from PVK dominates over the emission of the cluster while at the higher voltages (where performance of PVK is poor) emission from the cluster dominates.

Altogether these findings suggest that the complex and the polymer behave independently, i.e. there is no intersystem crossing between "singlet" polymer material and "triplet" complex and energy transfer from blue emitting PVK to ReeSs clusters is absent or not significant. The observations show that excitons form in both subsystems independently.

The pure rhenium complexes (without an electroluminescent polymer host) have

electroluminescent properties and can be considered useful for the design of red

light-emitting devices. As expected the device with the active layer 1 , i.e. made from the more concentrated solution shows more intensive emission. Interestingly though, the signal in the red region in case of devise 1 is notably more intensive in relation to those from PVK then in device 2.

The overall performance of the device is still quite poor in comparison with the famous PVK/iridium system (PVK doped with tns[2-phenyipyridinato-C2,N]iridium(H i) (lr(ppy)₃)

[M.-J. Yang, T Tsutsui, Jpn. J Appl. Phys. 2000, 39, 828.] and indicates possible problems of transport of charge carriers. However, we still consider the observation made on both devices to be significant, as they are the first direct experimental proof of electroluminescent properties of rhenium clusters. Moreover, to the best of our knowledge no

electroluminescent data has been published to date for any member of the family of 24-electron complexes eGsLe (where M=Mo, W, Re).

References

A number of publications are cited above in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Full citations for these references are provided below. The entirety of each of these references is incorporated herein.

WO 2011/064139

Moiard et al. (Chem. Eur. J. 2010, 16, 5613)

Dorson et al. (Dalton Trans. 2009, 1297)

Musse!l et al. (Inorg. Chem. 1990, 29, 3711)

Nocera et al. (J. Am. Chem. Soc. 1984, 106, 824)

Suzuki et al. (Phys. Chem. Chem. Phys., 2009, 11, 9850-9860)

Yang et al. (J. Appl. Phys. 2000, 39, 828)

Claims

Claims:

I . A metal cluster complex of formula (lla) having the formula [ΜβΟβΙ-β], optionally together with a counter ion,

where each M is a metal atom selected from Re, Mo and W;

each Q is independently selected from a halogen or chalogen atom; and

each L is a ligand, and at least one ligand L is L', where L' has an aromatic group and a polymerizable functionality.

2. The metal cluster complex of claim 1 , wherein each M is Re.

3. The metal cluster complex of claim 2 or claim 3, wherein each Q is selected from S and Se.

4. The metal cluster complex of any one of claims 1 to 3, wherein the metal cluster complex is neutral.

5. The metal cluster complex of any one of claims 1 to 4, wherein each L is an organic ligand.

6. The metal cluster complex of any one of claims 1 to 5, wherein L' has a benzene group and a polymerizable functionality.

7. The metal cluster complex of any one of claims 1 to 6, wherein the aromatic group of ligand L' is covalently linked to the polymerizable functionality.

8. The metal cluster complex of any one of claims 1 to 6, wherein the aromatic group of ligand L' is connected to the polymerizable functionality via a linker.

9. The metal cluster complex of any one of the preceding claims, wherein the ligand L' is connected to a metal M via an oxygen, nitrogen or sulfur atom of the ligand L'.

10. The metal cluster of claim X, wherein the ligand L' is connected to a metal M via a carboxy, oxy or sulfonate group of the ligand L'.

I I . The metal cluster complex of any one of the preceding claims, wherein two of the ligands L are ligands L'.

12. The metal cluster complex of claim 11 , wherein the two ligands U are arranged trans in the cluster complex.

13. The metal cluster complex of any one of the preceding claims wherein each L' is -0(0)C-C₆H₄-CH=CH₂.

14. The metal cluster complex of any one of the preceding claims having four ligands L each containing an aromatic group, such as a heteroaromatic group.

15. The metal cluster complex of claim 14, wherein the aromatic group is a pyridine group.

16. The metal cluster complex of any one of claims 1 to 15, wherein the polymerizable functionality is suitable for forming a polymer selected from the group consisting of polyethylene (including substituted polyethylene), polyacetylene (including substituted polyacetylene), polyester, polyamide, polyurethane, polyanhydride, and polysiloxane.

17. The metal cluster complex of claim 16, wherein the polymerizable functionality is suitable for forming a polyethylene (including substituted polyethylene).

18. The metal cluster complex of claim 17, wherein the polymerizable functionality is an ethylene group, including a substituted ethylene group.

19. The metal cluster complex of claim 18, wherein the ethylene group is selected from the group consisting of selected from the group consisting of a vinyl group, an alkyi vinyl group, a vinyl ether group, an alkyi vinyl ether group, a vinyl halide group, a vinyl ester group, an alkyi vinyl ester group, an acrylate group, an alkylacrylate group, an alkyi acrylate group, and an alkyi alkylacrylate group.

20. The metal cluster complex of claim 19, wherein the ethylene group is a vinyl group.

21. The metal cluster of any one of claims 1 to 20, where the ligand L' is connected to a metal atom of the cluster via a carboxy, oxy or sulfonate connecting group.

22. The metal cluster of claim 21 , wherein the carboxy, oxy or sulfonate connecting group is a substituent to the aryl group.

23. The metal cluster of any one of claims 1 to 20, wherein the polymerizable

functionality is a substituent to the aryl group or the polymerizable functionality is connected to the aryl group via a linker.

24. The metal cluster of claim 23, wherein the polymerizable functionality is a substituent to the aryl group.

25. The metal cluster of claim 23, wherein the linker is a Ci-3o alkylene group, wherein one or more methylene groups is optionally replaced with a group independently selected from -0-, -C(O)-, -S-, -C(0)0-, -C(0)NH-, an aromatic group, or a cycloalkylene group, and one or more hydrogen atoms in the alkylene group is optionally replaced with halo.

26. A polymerizable composition comprising a metal cluster complex of formula (I la) according to any one of claims 1 to 25, optionally together with a co-polymerizable monomer.

27. The polymerizable composition comprising a metal cluster complex of formula (lla) according to claim 26 together with a co-polymerizable monomer.

28. The polymerizable composition according to claim 26 or 27, wherein the metal cluster complex of formula (lla) comprises a ligand having the polymerizable functionality is an ethylene group, including a substituted ethylene group, and the co-polymerizable monomer has polymerizable functionality for co-polymerization of the monomer with the metal cluster complex.

29. The polymerizable composition according to claim 28, wherein the co-polymerizable monomer has an ethylene group, including a substituted ethylene group.

30. The polymerizable composition according to claim 29, wherein the ethylene group is selected from the group consisting of a vinyl group, an alkyi vinyl group, a vinyl ether group, an alkyi vinyl ether group, a vinyl halide group, a vinyl ester group, an alkyi vinyl ester group, an acrylate group, an alkylacrylate group, an alkyi acrylate group, and an alkyi alkylacrylate group.

31. The polymerizable composition according to claim 29, wherein the ethylene group is a vinyl group.

32. A polymer obtained or obtainable from the polymerizable composition of any one of claims 26 to 3 .

33. A method of preparing a polymer, the method comprising the step of polymerizing a polymerizable composition of any one of claims 26 to 31.

34. A method of generating light, the method comprising the steps of providing an octahedral metal cluster complex of formula (I), and applying an electric field across the metal cluster complex at a voltage of 5 V or more, to generate light from the cluster,

wherein the cluster complex (I) has the formula [ΜβΟβΙ-β], optionally together with a counter ion,

where each M is a metal selected from Re, Mo and W; each Q is independently selected from a halogen atom or a chalcogen atom; and each L is a ligand.

35. The method of claim 34, wherein the voltage is 9 V or more.

36. The method of claim 34 or 35, wherein each ligand L is an organic ligand.

37. The method of any one of claims 33 to 36, wherein the metal cluster complex (I) is a metal cluster complex (II) having the formula

where each M is a metal selected from Re, Mo and W;

each Q is independently selected from a halogen atom or a chalcogen atom; and each L is a ligand; and

each L' is a ligand having a polymerizable functionality.

38. The method of claim 34, wherein the wherein the metal cluster complex (II) is a metal cluster complex (Ma) as defined in any one of claims 1 to 25.

39. A method of generating light, the method comprising the steps of providing a polymer and applying an electric field across the polymer at a voltage of 5 V or more, to generate light from the polymer, and

the polymer is a polymer obtainable or obtained from a polymerizable composition comprising a metal cluster complex of formula (II), optionally together with a

co-polymerizable monomer,

wherein metal cluster complex (II) has the formula [MeQeUL^],

where each M is a metal selected from Re, Mo and W;

each Q is independently selected from a halogen atom or a chalcogen atom; and each L is a ligand; and

each L' is a ligand having a polymerizable functionality.

40. The method of claim 39, wherein the metal cluster complex (II) is a metal cluster complex (lla) as defined in any one of claims 1 to 25.

41. A light-emitting device comprising a metal cluster complex of formula (I) disposed between electrodes, wherein the device is a solid state device, wherein the cluster complex (I) has the formula [MeQeLe], optionally together with a counter ion,

where each M is a metal selected from Re, Mo and W;

each Q is independently selected from a halogen atom or a chalcogen atom; and each L is a ligand.

42. The light-emitting device according to claim 41 , wherein the metal cluster complex of formula (I) is dispersed in a polymer that is disposed between the electrodes.

43. A light-emitting device comprising a polymer disposed between electrodes, wherein the polymer is a polymer obtainable or obtained from a polymerizable composition comprising a metal cluster complex of formula (II), optionally together with a

co-polymerizable monomer,

wherein metal cluster complex (II) has the formula [MeQeUL'sJ,

where each M is a metal selected from Re, Mo and W;

each Y is a halogen atom or a chalcogen atom; and

each L is a ligand; and

each L' is a ligand having a polymerizable functionality.

44. The light-emitting device according to claim 43, wherein the metal cluster complex (II) is a metal cluster complex (Ha) as defined in any one of claims 1 to 25.

45. A method of generating light, the method comprising the step of providing a light- emitting device according to any of claims 41 to 44, and applying a voltage between the electrodes, to generate light from the device.

46. A method of generating light, the method comprising the steps:

(i) providing a polymer; and

(ii) applying an electric field across the polymer at a first voltage of 5 V or more, to generate light from the polymer; and

(ii) applying an electric field across the polymer at a second voltage of 5 V or more, which voltage is different to the first voltage to generate light from the polymer,

wherein the polymer is an electroluminescent polymer, and a metal complex of formula (I) is dispersed within the polymer, or the polymer is obtained or obtainable from a polymerizable composition comprising a metal cluster complex of formula (II), optionally together with a co-polymerizable monomer,

wherein metal cluster complex (II) has the formula [MeQeUL^],

where each M is a metal selected from Re, Mo and W;

each Q is independently selected from a halogen atom or a chalcogen atom; and each L is a ligand; and

each L' is a ligand having a polymerizable functionality.

47. The method of claim 46, wherein the light emitted in response to the first voltage has an emission maximum that is different to the emission maximum of the light emitted in response to the second voltage.

48. The method of claim 46 or claim 47, where in the first and second voltages differ by at least 0.5 V.

49. The method of any one of claims 46 to 48, wherein the compound of formula (II) is a compound of formula (lla) as set out in any one of claims 1 to 25.

50. A photovoltaic device comprising a metal cluster complex of formula (I) or a polymer obtained or obtainable from a polymerizable composition comprising a metal cluster complex of formula (I), optionally together with a co-polymerizable monomer.

51. The photovoltaic device of claim 50 which is a solar cell or a solar concentrator.

52. A method for generating an electrical current, the method comprising the steps of:

(i) providing a photovoltaic device according to claim 50 or claim 51 ; and

(ii) exposing the photovoltaic device to light, such as sunlight, thereby to generate an electrical current within the photovoltaic device.