WO2004031321A1

WO2004031321A1 - Oxygen sensing compounds, methods for production thereof and their uses

Info

Publication number: WO2004031321A1
Application number: PCT/CA2002/001478
Authority: WO
Inventors: Christopher Edward Brisbane Evans; Robert John Crutchley; Maria Cynthia Derosa; Peter John Mosher
Original assignee: National Research Council Of Canada; Carleton University
Priority date: 2002-10-02
Filing date: 2002-10-02
Publication date: 2004-04-15
Also published as: AU2002328731A1; AU2002328731A8

Abstract

Polymeric compounds comprising an iridium luminophore, having luminescence sensitive to oxygen concentration, covalently bound to a polymer are useful as oxygen sensors, particularly in pressure sensitive paints (PSPs). One embodiment for making such polymeric compounds involves a hydrosilation reaction between a hydride functionalized polysiloxane and a vinyl functionalized iridium complex.

Description

OXYGEN SENSING COMPOUNDS, METHODS FOR PRODUCTION THEREOF AND

THEIR USES

Field of the Invention

This invention relates to oxygen sensing compounds, methods for their production and uses therefor.

Background of the Invention

When a chemical compound absorbs light, the extra energy forces the molecule to enter an excited state which is less stable than its ground (most stable) state. The • excited molecule will attempt to return to its ground state by dissipating the extra energy through any available means. While the most common way for this extra energy to be dissipated is by converting it into heat, certain molecules can also dissipate the extra energy by emitting it as light. These two methods of losing energy are termed, respectively, non-radiative and radiative relaxation. The light emitted during radiative relaxation is known as luminescence, and the molecule itself as a luminophore. The emitted light is always of lower energy than the exciting light due to the nature of the emission process. (Lower energy light can equivalently be described as having a lower frequency, a longer wavelength, or of being red-shifted) . This causes an offset between the luminophore ' s absorption and emission spectra. The magnitude of the offset is called the Stokes' shift. Because the radiative, and non-radiative pathways are always in competition with each other, under any given conditions only a fraction of the absorbed light is ever emitted as luminescence. This fraction is called the luminophore ' s luminescence quantum yield (hereinafter referred to simply as quantum yield) . A luminophore ' s quantum yield is often sensitive to the presence of other molecules due to luminescence quenching, a non-radiative process in which the excited luminophore is relaxed by transferring energy to another molecule. The term dynamic quenching is used to describe the case where energy transfer is due to collisions between molecules of quencher and excited luminophore. Oxygen is well known as an effective quencher of luminescence, and many luminescent species may therefore be employed as oxygen sensors, e.g. for in vivo or ground water oxygen monitoring. Because the concentration of oxygen in air is largely invariant, oxygen sensors can also be used as pressure sensors under certain circumstances in a technique called luminescence barometry (the measuring of pressure through a change in luminescence of a luminophore) . The combination of an oxygen-quenchable luminophore dispersed within a gas- permeable matrix is known within the aerodynamics community as a Pressure Sensitive Paint (PSP) . (Note that in relation to PSPs, the term sensor is used to describe the PSP film itself, and not the combination of equipment used for data acquisition. )

PSPs are gaining increasing favour as tools for surface pressure measurements during wind tunnel testing. In this application the sensor is applied to the surface of interest as a thin film, and responds to local changes in pressure due to the (assumed) Henry's Law dependence of (equilibrium)^' oxygen concentration within the sensor film to pressure above the surface. As the oxygen concentration increases or decreases, the emission intensity conversely decreases or increases. While PSPs have demonstrated their ability to measure static pressures over surfaces accurately, a variety of challenges remain to be resolved. The simplest system for measuring oxygen concentration via luminescence quenching requires, in

addition to the sensor itself, a light source to excite the luminophore and a detector to measure the emitted radiation. Measurements can be made on the basis of luminescence intensity or lifetime. Hereinafter, the term "change in luminescence" encompasses "change in luminescence intensity", "change in luminescence lifetime", a change in another appropriate luminescence property, or any combination of the foregoing. Depending upon the spectral properties of the system's components, optical filters are usually used to reduce spectral overlaps . The excitation source is equipped with a filter to reduce any overlap between its spectrum and the luminophore ' s emission spectrum, and the detector is fitted with a cut-off filter opaque to the exciting light. Luminophores with large Stokes' shifts greatly simplify optical filtering.

A sensor's 'brightness' is a measure of its ability to convert exciting light to emitted light, and depends on the luminophore ' s efficiency in absorbing and emitting light. The latter efficiency is given by the quantum yield, while the former is given by the coefficient of molar absorptivity (often called the extinction coefficient) . It is advantageous for the luminophore to be as efficient as possible in converting light, since experimental conditions often limit the intensity and/or number of light sources used for excitation.

For a PSP to be effective it must exhibit a significant response to pressure changes, as measured by the degree to which the luminophore ' s emission is quenched

(diminished) by oxygen which has diffused into the permeable matrix. This requires, therefore, that the luminescence lifetime (i.e. in the absence of quencher (to)) be long enough to allow for meaningful quenching to occur. (There is no rigid benchmark to what constitutes 'long enough', but generally the longer the luminophore ' s lifetime, the more opportunity it will have to collide with an oxygen molecule and be quenched.) It also requires that the matrix allow gas sorption and desorption on a reasonable time-scale. (What constitutes a 'reasonable time-scale' depends on the application. For a blow-down wind tunnel, the paint should respond, minimally, on the order of tenths of seconds or seconds.) The response of a PSP to pressure is called its quenching sensitivity or its pressure sensitivity. While sensitivity to oxygen is the sole consideration for certain applications of luminescent oxygen sensors, there are a number of additional concerns when these sensors are to be used within wind tunnels as PSPs.

One example of a high-speed wind tunnel is of a type known as blow-down, indicating that airflow is achieved by the controlled release of compressed air. Data must be obtained during relatively short windows of stable airflow. This imposes on the sensor the requirement for a rapid response. During the test, dust and debris (which are ubiquitous to the tunnel environment) . impinge the sensor at test speeds, and the sensor must thus be sufficiently robust to withstand these impacts without significant degradation or delamination.

During a wind-tunnel experiment, the air flow can cause significant heat transfer to the model. This results in temperature gradients which occur across the model surface in conjunction with the pressure gradients. The PSP response, unfortunately, depends on several temperature- dependent quantities related to both luminophore and matrix. In the case of the luminophore, the lifetime of its excited state is dependent on a number of kinetic rates, including ^• the rates of bimolecular quenching and of non-radiative relaxation. The emission quantum yield is, thus, temperature dependent. In the case of the matrix, temperature changes affect not only the kinetic rates of gas sorption and desorption, but also the overall solubility of gases in the matrix. It is therefore important either to develop a sensor in which these temperature effects are minimal or quantifiable.

In addition, it is important that the PSP not interfere in the model's aerodynamics. For this to be the case a smooth, hard finish is desirable. The PSP film must also be thin, both to minimize interference with the airflow, and to allow faster equilibration to pressure changes (i.e. sensor response time) .

Sensor brightness is important to the PSP measurement as it determines the exposure time necessary for the camera to obtain a useful signal. For a given concentration of luminophore (within the matrix) , emission intensity is a function of film thickness. As the films are made thinner, it becomes necessary to increase the concentration of luminophore to maintain emission intensities sufficient for short exposure times . As the ^" luminophore concentration is increased, the possibility of luminophore molecules interacting with each other increases. These interactions can take the form of energy transfer (called self-quenching) or of association into pressure- insensitive aggregates. To ensure a homogeneous distribution of luminophore within the matrix, and to avoid the formation of aggregates, it is necessary that the matrix be a good solvent for the luminophore. Because singlet oxygen is a natural by-product of luminescence quenching by oxygen, reactions of either the luminophore or the matrix with reactive singlet oxygen may alter the PSPs behaviour. The question of sensor stability and reproducibility is therefore of concern. When only luminophore is consumed by these reactions (photobleaching) , an overall decrease in emission intensity is observed. It is important, minimally, that the rate at which photobleaching occurs be insignificant relative to the data acquisition times. If the matrix itself is significantly affected (altered) by reactions with singlet oxygen, an overall change in quenching sensitivity may occur (due, e.g., to changes in permeability). Fortunately, such effects are not usually observed.

Finally, when a suitable luminophore/matrix combination is identified, it is important that the resultant PSP composition can be reproduced on a batch-to- batch basis to ensure consistent sensor behaviour.

Terminology from the paints and coatings industry is often applied to the field of PSPs. Thus the PSP sensor system is a coating consisting of all the components applied to the surface. The ready-to-apply PSP mixture is called the paint's formulation, and includes any volatiles (solvents, stabilizers, etc.) used in the application process. The primary components of a coating are the dye (luminophore) and binder (matrix) . In addition, pigments (e.g. titania or silica) are sometimes added to provide mechanical rigidity to the coating. In isolation, 'PSP' typically refers to the coating.

Throughout the present specification, the term

"covalently bound" shall mean bonded by a form of chemical bond in which at least one pair of electrons is shared, equally or unequally, between two atoms, and shall be taken to encompass both non-polar and polar covalent bonds.

Summary of the Invention

In accordance with the present invention, there is provided a polymeric compound comprising an iridium luminophore, having luminescence sensitive to oxygen concentration, covalently bound to a polymer.

There is also provided the use of such a polymeric compound as an oxygen sensor, particularly as a pressure sensitive paint. There is further provided a pressure sensitive paint formulation comprising such a polymeric compound and an additive.

There is yet further provided a method for detecting and/or measuring the presence and/or amount of oxygen in an environment comprising contacting such a polymeric compound with the environment, detecting and/or measuring a change in luminescence of the polymeric compound, and correlating the change in luminescence to the presence and/or amount of oxygen in the environment.

Still further, there is provided a compound of formula (III) :

[Ir(C-N)₂LX] (F^x)_p , (III)

wherein C-N is a conjugated cyclometallating ligand, L is a monodentate ligand, X is a monoanionic monodentate ligand, or L and X taken together form a monoanionic bidentate ligand or a ^"C-N ligand, F¹ is a functional group suitable for bonding to a polymer or a monomer, and p is an integer from 1 to 3. Still yet further, there is provided a process comprising a hydrosilation reaction between a vinyl functionalized iridium complex and a hydride functionalized polysiloxane to form a polysiloxane bearing a covalently bound iridium complex. Likewise, there is provided a process comprising a hydrosilation reaction between a vinyl functionalized iridium complex and a hydride functionalized siloxane monomer to form a siloxane monomer bearing a covalently bound iridium complex, which can be then polymerized to form a polysiloxane bearing covalently bound iridium complexes .

There is also provided a process comprising a hydrosilation reaction between a silicon hydride functionalized iridium complex and a vinyl functionalized polysiloxane to form a polysiloxane bearing a covalently ' bound iridium complex.

The polymeric compounds of the present invention comprise an iridium luminophore covalently bound to a polymer to form a unimolecular compound. The polymer part of the compound serves as a matrix' material for the particular oxygen sensing application to which the compound is put. Polymeric compounds of the present invention are suited to pressure sensitive paints (PSPs) . The luminescence of the iridium luminophore depends on oxygen concentration, therefore a change in luminescence when the polymeric compound is exposed to an environment may be correlated to the presence and/or concentration of oxygen in the environment. Since oxygen quenches the luminescence of the luminophore, a loss of luminescence (e.g., intensity) is correlated to the presence of oxygen. Measurement of luminescence can be done by any standard method in the art. The polymeric -compounds of the present invention in which an iridium luminophore is covalently bound to a polymer may also be conveniently referred to as 'dye- attached' systems. Such systems have certain advantages over analogous materials in which the luminophore is dispersed or suspended in a polymer (matrix) material. Dye- attached systems are not as subject to dye-leaching, and provide other advantages with respect to ease of handling and selection of additives. In addition, dye-aggregation, a phenomenon leading to decreased sensitivity of the sensor, may also be reduced in a unimolecular paint of the present invention since the luminophore molecules cannot move independently of the polymer (matrix) material.

The polymeric compounds of the present invention may be synthesized by an appropriate reaction between an iridium luminophore and a polymer. The reaction, may be direct, or one or both of the iridium luminophore and the polymer may be suitably functionalized before the reaction. The nature and scope of possible reactions and suitable functional groups are virtually unlimited. For instance, one skilled in the art can -readily adapt standard syntheses as described in March (Jerry March, Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, Third Edition, 1985, Wiley-Interscience, New York) , which is hereby incorporated by reference. For example, addition, substitution and elimination reactions are just three examples of general types of reactions which may be used. Likewise, functional groups on the iridium luminophore and/or the polymer may be of very wide scope. The only limitation is that the iridium luminophore (whether functionalized or not) must be able to react with the polymer (whether functionalized or not) so that the iridium luminophore is covalently ^' bound to the polymer. When the iridium luminophore is reacted directly with the polymer, the luminophore and polymer will be linked by a direct covalent bond. If the iridium luminophore and/or the polymer are first functionalized with a functional group, the luminophore and polymer will be linked by a direct covalent bond or by a fragment of the functional group covalently bound to both the polymer and iridium luminophore. Reactions may be carried out between pairs of suitable functional groups on the iridium luminophore and polymer. Many types of reactions and appropriate reaction conditions are known to one skilled in the art. Examples of some appropriate functional groups are given below.

Alternatively, polymeric compounds of the present invention may be synthesized by first synthesizing a monomeric species by an appropriate reaction between an iridium luminophore and a monomer and then polymerizing the monomeric species by methods generally known in the art to form a polymer to which the iridium luminophore is covalently bound. The scope and nature of the possible reactions between the iridium luminophore and the monomer is similar to that described above for the reaction of the iridium luminophore with a polymer.

In one embodiment, a class of polymeric compounds suitable for the present invention is given by a compound of formula (I) :

P-(Z_m-U)_n (I),

wherein P is a polymer backbone, U is an iridium luminophore, Z is a linker between the polymer backbone and the iridium luminophore, m is an integer from 1 to 3, preferably 1, and n is an integer from 1 to 5000, or from 1 to 500, or from 1 to 100, or from 1 to 20, or from 1 to 2. When m is greater than 1, each Z may be the same or different. When n is greater than 1, each Z and/or each U may be the same or different.

The linker, Z, in one embodiment, comprises a direct covalent bond, a fragment of a functional group covalently bonded to both the polymer backbone and the iridium luminophore, or a combination thereof. The linker can be considered a structure derived from a reaction between a functional group on the polymer backbone and a functional group on the iridium luminophore, to create a covalent link between the polymer backbone and the iridium luminophore. Such a structure may be referred to as a fragment of a functional group. For -example, when one functional group comprises a vinyl group and the other functional group comprises a silicon hydride, the linker formed comprises an alkyl group, and the linker may also be referred to as a fragment of a vinyl . group and/or a fragment of a silicon hydride group. Where more than one iridium luminophore is bonded to the polymer backbone, the linker may be the same or different for each luminophore. Where more than one linker binds a single luminophore to the polymer backbone, the linkers may be the same or different for that luminophore. Some specific examples of suitable fragments which may serve as linkers are linkers that comprise a fragment of a vinyl, a carbonyl, a thiocarbonyl, a carboxylic acid, a carboxylate, a thiocarboxylic acid, a thiocarboxylate, an amine, an amide, a thiol, a hydroxyl, an epoxide, an alkyl halide, a silicon hydride, an anhydride, an acid chloride, an isocyanate, an isothicyanate group, etc. or a combination thereof. Table 1 below further illustrates some examples of linkers and corresponding functional groups of which the linkers are fragments. One skilled in the art will readily recognize other possible , combinations. Linkers that comprise a fragment of a vinyl group are preferred.

Table 1

The polymer backbone, P, may be the backbone of any polymer to which an iridium luminophore can be covalently bound. The nature of the polymer may be dictated by. the application for which the polymeric compound is intended. The polymer may be selected on the basis of its mechanical, electrical and/or other physical and chemical properties in order to fine-tune the behaviour of the resultant polymeric compound. For example, polymers with good gas permeability may be of particular value for oxygen sensing applications. The polymer may be, for example, a homopolymer, copolymer, terpolymer and/or any other polymeric form -and/or blend of polymers . Some suitable classes of polymers are, for example, polysiloxanes, polyolefins, polycarbonates, polyimides, polyethersulfones, polyetherketones, polypeptides, polynucleic acids, polymers of cellulose derivatives, polymers of phosphazene derivatives, among others, or combinations thereof.

In some embodiments, the polymer may be poly (dimethylsiloxane) (PDMS) , polystyrene (PS), poly (dimethylsiloxane) -polystyrene block copolymer (PDMS-b- PS) , poly (thionylphosphazene) (PTP) , poly (n-butylamino thionylphosphazene) (PATP) , polyvinyl chloride (PVC) , polyoxyethylene (PEO) , polyethylene (PE) , polypropylene (PP), polyacrylic acid (PAA) , polymethacrylic acid (PMA) , poly (methylmethacrylate) (PMMA) , poly-2-hydroxyethylmethacrylate, poly (fluoromethacrylate) , poly (tetrafluoroethylene) (PTFE) , poly (vinylacetate) (PVA) , poly (ethylene terephthalate) , cellulose acetate butyrate (CAB), high-Tg fluorinated alkylacrylate polymers (i.e. poly (fluoroalkylalkacrylates) ) , or a combination thereof.

Of particular interest are polysiloxanes (for example, poly (dimethylsiloxane) and poly (dimethylsiloxane) -polystyrene block copolymer), and, poly (fluoroalkylmethacrylates) (for example, poly (hexafluoroisopropyl-co-heptafluoro-n- butylmethacrylate) (FIB) ) .

As a class, polysiloxanes are very useful in PSPs since they tend to exhibit good gas permeability. Suitably functionalized polysiloxanes can react with suitably functionalized luminophores to produce polymeric compounds of the present invention. Functionalized polysiloxanes are generally known in the art and are commercially available, for example from Gelest. The following is an exemplary list of functionalized polysiloxanes:

hydride terminated polydimethylsiloxanes;

methylhydrosiloxane-dimethylsiloxane copolymers ;

polymethylhydrosiloxanes;

polyethylhydrosiloxanes ;

polyphenyl (dimethylhydrosiloxy) siloxane, hydride terminated;

methylhydrosiloxane-phenylmethylsiloxane copolymer, hydride terminated;

methylhydrosiloxane-octylmethylsiloxane copolymer;

vinyl terminated polydimethylsiloxanes;

vinyl terminated diphenylsiloxane-dimethylsiloxane copolymers;

vinyl terminated polymethylphenylsiloxane;

vinyl terminated trifluoropropylmethylsiloxane- dimethylsiloxane copolymer;

vinyl terminated diethylsiloxane-dimethylsiloxane copolymer;

vinylmethylsiloxane polymers;

vinylmethoxysiloxane polymers;

vinylmethylsiloxane-dimethylsiloxane copolymers, trimethylsiloxy terminated;

vinylmethylsiloxane-dimethylsiloxane copolymers, silanol terminated; vinylmethylsiloxane-dimethylsiloxane copolymers, vinyl terminated;

vinylmethylsiloxane-octylmethylsiloxane-dimethylsiloxane terpolymer;

vinylmethylsiloxane-phenylmethylsiloxane-dimethylsiloxane terpolymer;

a inopropyl terminated polydimethylsiloxanes;

aminopropylmethylsiloxane-dimethylsiloxane copolymers;

aminoethylaminopropylmethylsiloxane-dimethylsiloxane copolymers;

aminoethylaminoisobutylmethylsiloxane-dimethylsiloxane copolymers;

aminoethylaminopropylmethoxysiloxane-dimethylsiloxane copolymers;

epoxypropoxypropyl terminated polydimethylsiloxanes;

(epoxycyclohexylethyl)methylsiloxane-di ethylsiloxane copolymers;

carbinol (hydroxy) terminated polydimethylsiloxanes;

( carbinol functional ) methylsiloxane-dimethylsiloxane copolymers;

methacryloxypropyl terminated polydimethylsiloxanes;

acryloxy terminated polydimethylsiloxanes;

(methacryloxypropyl ) methylsiloxane-dimethylsiloxane copolymers;

(acryloxypropyl)methylsiloxane-dimethylsiloxane copolymers; ( ercaptopropyl)methylsiloxane-dimethylsiloxane copolymers;

(chloropropyl) methylsiloxane-dimethylsiloxane copolymers;

(carboxyalkyl) terminated polydimethylsiloxane;

succinic anhydride terminated polydimethylsiloxane;

chlorine terminated polydimethylsiloxanes;

diacetoxymethyl terminated polydimethylsiloxanes;

di ethylamino terminated polydimethylsiloxanes;

methoxy terminated polydimethylsiloxanes .

Methods for producing a variety of end- functionalized and side-chain functionalized silicones are also given in Brook (Michael A. Brook, Silicon in Organic, Organometallic, and Polymer Chemistry, 2000, John Wiley & Sons, Inc., NY), which is hereby incorporated by reference.

The iridium luminophore, U, may be any iridium- containing compound which luminesces. Electrically neutral iridium luminophores are advantageous .

In one embodiment, the iridium luminophore may be a complex of iridium with an organic ligand, for example, a ^• complex of iridium with a bidentate and/or tridentate organic ligand. The bidentate or tridentate ligand is preferably conjugated. Some examples of bidentate or tridentate organic ligands are 2-phenylpyridinato, 4, 7-diphenyl-l, 10 ' -phenanthroline, coumarin 6, 2- (2 ' -thienyl) pyridinato, 2-phenyloxazolinato, 2, 2 ' -bipyridine, 2- (2 ' -benzothienyl) pyridinato,

2, 4-diphenyloxazolato, 2- (1-naphthyl) behzooxazolato, 2- (2-naphthyl) benzothiazolato, etc. In one embodiment, iridium luminophores are iridium complexes of formula (II) :

[Ir(C-N)₂LX] (II),

wherein C-N is a conjugated cyclometallating ligand, L is a monodentate ligand and X is a monoanionic monodentate ligand, or L and X taken together form a monoanionic bidentate ligand or a C-N ligand.

Cyclometallating ligands are ligands that form at least one carbon-metal bond and form a ring which includes the metal. The cyclometallating ligand preferably comprises at least one aromatic moiety. Specific examples are complexes of formula (II) , wherein each C-N is independently selected from the group consisting of 2-phenylpyridinato, coumarin 6, 2- (2 ' -thienyl) pyridinato, 2-phenyloxazolinato, 2- (2 ' -benzothienyl) pyridinato, 2, 4-diphenyloxazolato,

2- (1-naphthyl) benzooxazolato, 2- (2-naphthyl) benzothiazolato, 7, 8-benzoquinolinato, 2-phenylbenzothiozolato, 2- (4-tolyl) pyridinato, 2-phenylquinolinato, and 2- (1-naphthyl) benzylthiozolato) .

L may be a monodentate ligand. Neutral organic monodentate ligands are preferred. There are a wide variety of possible ligands which are suitable, a non-limiting example of which is vinylpyridine .

X may be a monoanionic monodentate ligand. X may be an inorganic ligand, such as a halide, for example chloride or bromide, particularly chloride.

When L and X are taken together, LX may form a monoanionic bidentate ligand or a C-N ligand as defined above. Monoanionic bidentate ligands are preferably β-diketonate ligands, such as 2, 4-pentanedionate (acac) and 3-substituted acac, wherein the substituent may be, for example, alkyl (e.g. methyl, ethyl, propyl or butyl), or any other suitable substituent.

In polymeric compounds of formula (I) which comprise iridium complexes of formula (II), the linkers may be covalently bound to the iridium complex through one or more of the C-N ligands and/or through the monoanionic bidentate ligand (LX) or the monodentate ligand (L) .

In one embodiment, there is provided functionalized iridium compounds of formula (III):

[Ir(C-N)₂LX] (F^x)_p (III) ,

wherein C-N, L and X are as defined for complexes of formula (II) , F¹ is a functional group suitable for bonding to a polymer or a monomer, and p is an integer from 1 to 3, preferably 1. Compounds of formula (III) may be suitable for reaction with a polymer or a functionalized polymer to form a polymeric compound of the present invention. (Note: it is to be understood that the functional group, F¹, may be suitable for reaction with a monomer or a functionalized monomer to form a monomeric species which can then be polymerized into a polymer. Reference to 'polymer' in this regard is therefore applicable as well to monomers which will be subsequently polymerized.) Reaction of the functional group F¹ with the polymer or functionalized polymer yields a polymeric compound of formula (I) wherein the linker Z is a fragment of the functional group F¹ together with a fragment of the functional group on the polymer with which F¹ may have reacted. Functional groups, F¹, may be bonded to one or more of the C-N ligands and/or to the monoanionic bidentate ligand (LX) or the monodentate ligand (L) . Where p is 2 or 3, the functional group, F¹, may be the same or different in each instance. Furthermore, each F¹ may covalently bind to the same or different polymer strand.

The nature of the functional group, F¹, is virtually unlimited since, as indicated previously, there are a large variety of possible reactions which one skilled in the art can use to covalently link functional groups together. One skilled in the art can readily determine appropriate functional groups suitable for a binding strategy to a given polymer or functionalized polymer. Some examples, among others, of suitable functional groups are given above in Table 1.

Synthetic strategies for preparing compounds of formula (III) are adaptable from standard synthetic sequences, for instance, from synthetic sequences described in March (Jerry March, Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, Third Edition, 1985, Wiley-Interscience, New York) , which is hereby incorporated by reference. For example, a vinyl group may be introduced on to the luminophore by way of a Wittig reaction, an elimination reaction or a nucleophilic substitution. Such a vinylization may be done on a ligand prior to or after forming ligand-iridium bonds. After vinylization other functional groups may be prepared readily from the vinyl group by known methods.

Hydrosilation reactions are a particularly suitable type of reaction for the formation of polymer bound iridium luminophores . Hydrosilation reactions involve the reaction of a vinyl group with a silicon hydride to form a Si-C covalent bond. Either the polymer or the iridium luminophore may bear the vinyl functional group with the other bearing the silicon hydride functional group. Conveniently, the vinyl group may be on the iridium . luminophore while the silicon hydride is on the polymer, although the reverse is possible. Uncharged iridium complexes are particularly useful in this type of reaction. Hydrosilation reactions typically employ a catalyst. One skilled in the art knows of a variety of suitable catalyst, with platinum complexes or salts being preferred. Karstedt's and Speiers ' catalysts are two well known catalysts for hydrosilation reactions.

Many suitable hydride functionalized silicon containing polymers are known in the art and are available commercially, for example from Gelest. Methodology for synthesizing hydride terminated polysiloxanes is given in Brook (Michael A. Brook, Silicon in Organic, Organometallic, and Polymer Chemistry, 2000, John Wiley & Sons, Inc., NY), which is hereby incorporated by reference) , which is hereby incorporated by reference. The following are examples of some suitable commercially available hydride functionalized polysiloxanes :

hydride terminated polydimethylsiloxanes;

methylhydrosiloxane-dimethylsiloxane copolymers;

polymethylhydrosiloxanes ;

polyethylhydrosiloxanes;

polyphenyl (dimethylhydrosiloxy) siloxane, hydride terminated;

methylhydrosiloxane-phenylmethylsiloxane copolymer, hydride terminated;

methylhydrosiloxane-octylmethylsiloxane copolymer .

In one embodiment, there is provided vinyl functionalized iridium compounds of formula (IV) : [ Ir ( C-N ) ₂LX] ( F² ) _q ( IV) ,

wherein C-N, L and X are as defined for complexes of formula (II), F² is a functional group comprising a vinyl group, and q is an integer from 1 to 3, preferably 1. Compounds of formula (IV) may be prepared by generally known vinylization reactions, such as Wittig reactions, elimination reactions^' and nucleophilic substitution reactions, as generally described in March (Jerry March, Advanced Organic Chemistry: Reactions-, ^■ Mechanisms, and Structure, Third Edition, 1985, Wiley-Interscience, New York) , which is hereby incorporated by reference. Such a vinylization may be done on a ligand prior to or after forming ligand-iridium bonds. F² may be bound to one or more of the C-N ligands and/or to the monoanionic bidentate- ligand (LX) or the monodentate ligand (L) : F² is preferably a vinyl, allyl or allyloxy group and q ^•is preferably 1.

In one embodiment, a hydrosilation reaction between a vinyl functionalized iridium complex and a hydride - functionalized polysiloxane produces a polysiloxane bearing covalently bound iridium complexes. If a hydride terminated polysiloxane such as hydride terminated poly (dimethylsiloxane) is used, there will be a maximum of two iridium complexes covalently bound to each polymer. The number of bound iridium complexes per polymer can be controlled by using polysiloxanes having different amounts of hydride functionalization.

In another embodiment, a hydrosilation reaction between a vinyl functionalized iridium complex and a hydride functionalized siloxane monomer produces a siloxane monomer bearing a covalently bound iridium complex. Polymerization may then be effected to yield a polysiloxane bearing covalently bound iridium complexes. For example, a vinyl functionalized iridium complex may be reacted with a hydride functionalized siloxane monomer and the resulting product polymerized to give a polysiloxane with covalently bound iridium complexes. Polymerization can be accomplished by adapting the process disclosed in Paulasaari, J.K., Weber, W. P. Macromolecules, (1999) 32, 6574-6577, hereby incorporated by reference, for the polymerization of PDMS .

Alternatively, a siloxane monomer bearing a covalently bound iridium complex may be copolymerized with another monomer to yield a copolymer bearing covalently bound iridium complexes. Any suitable comonomer may be used, for example, olefinic monomers such as ethylene, propylene, butylene and styrene. For example, when cyclic hexamethylsiloxane is copolymerized with styrene by living anionic polymerization, a block copolymer is formed (see

Lee, J.; Hogen-Esch, T. E. Macromolecules, (2001) 34, 2095- 2100, the disclosure of which is hereby incorporated by reference) .

Luminophores of all kinds may be covalently linked to polymers by way of hydrosilation reactions disclosed herein. Ruthenium analogues, pyrenes, perylenes and porphyrins are all examples of luminophores that may be functionalized with a vinyl group and bound to a polymer through reaction with a hydride functionalized polysiloxane (or vice versa) . Alternatively, as described above, the functionalized luminophore may be reacted with a functionalized siloxane monomer to form a siloxane monomer bearing a covalently bound luminophore, which is then polymerized to form a polysiloxane bearing a covalently bound luminophore.

In another embodiment, an iridium luminophore may be covalently bound to a high-T_g fluorinated alkylmethacrylate polymer commonly used in PSPs (for example, poly (hexafluoroisopropyl-co-heptafluoro-n- butylmethacrylate) (FIB)) . To form such a polymeric compound, a hydroxyl functionalized iridium luminophore may be reacted, for example, with poly (hexafluoroisopropyl-co- heptafluoro-n-butylmethacrylate) (FIB) in a trans- esterification reaction to form the polymeric compound. Alternatively, a hydroxyl functionalized iridium luminophore may be reacted, for example, with heptafluoro-n- butylmethacrylate monomer to form a monomeric species having the iridium luminophore covalently bound to it, which can be subsequently copolymerized with hexafluoroisopropylmethacrylate to form a polymeric compound. Trans-esterification reactions may be acid or base catalyzed in a manner generally known in the art.

Polymeric compounds of the present invention in which an iridium luminophore is covalently bound to a polymer are useful as oxygen sensors in a variety of applications. Additionally, luminescent iridium complexes of formulas (II), (III) and (IV) even when not bound to a polymer may be used for oxygen sensing applications . Oxygen sensors may be used to detect and/or measure the amount of oxygen in a variety of different environments. In vivo and ■ in solvento (e.g. ground water) oxygen monitoring applications and pressure sensitive paints (PSP) are some examples .

Pressure sensitive paint is one application of particular interest. When used to measure pressure distributions over surfaces, a PSP is applied to the model of interest as a thin film, typically using an airbrush to apply the coating. There are a number of different PSPs currently being used for luminescence barometry. These paints are typically composites of either siloxane or fluoromethacrylate polymers or porous sol-gel glasses as the binder, and either a metalloporphyrin, a polypyridyl transition metal complex, or a polycylic aromatic molecule as the luminophore. In particular, platinum tetrakis (pentafluorophenyl) porphyrin (PtTPFPP) , [Ru (dpp) ₃] Cl₂ (dpp = 4, 7-diphenylphenanthroline) , and pyrene are all used as luminophores in extant formulations.

Each luminophore has characteristic absorption and emission spectra, and thus specific wavelengths with which it can be excited and at which it emits . Each dye-matrix combination has different overall properties of pressure and temperature sensitivity. Depending upon the specific application, greater or lesser pressure sensitivities are desirable, and greater or lesser temperature sensitivities are tolerable.

In low-speed tests, for example, sensor responses due to temperature and pressure fluctuations are often of similar magnitude (since the pressure changes are quite small) . In such tests it is therefore .important to correct accurately for temperature changes. In contrast, the large pressure variations in high-speed tests mean that the magnitude of the sensor's response to pressure is often much larger than its response to temperature. In these tests temperature corrections are less significant, but there are much higher demands for sensor robustness.

The majority of PSPs currently being used are 'dye-dispersed' systems in which the binder acts as, solvent for the dye. To a greater or lesser extent, depending upon the specific matrix material, the luminophore molecules may move within the matrix. This mobility allows for dye partitioning (leaching) whenever an alternate solvent for the luminophore is present, and is particularly worrisome for in vivo and in solvento applications of oxygen sensors. Dye-leaching can also be a drawback for PSP sensors.

In wind-tunnel applications, the surface of interest is typically coated with a white primer layer to provide both improved reflectivity and homogeneity of the background. With some PSPs, problems have been noted with dye leaching into these primer coats, seemingly due to partial solvation of the primer coating by the solvents used during application of the PSP. While such dye leaching can be reduced (by judicious selection of the primer, or in certain cases by curing the primer coating) this reduces generality- and ease-of-application of the sensor.

In the case of pyrene-based paints, which are desirable because of their low temperature sensitivity, a diffusion-related problem with the dye-dispersed formulations is the sublimation of dye from the matrix over time. This problem is particularly detrimental to these - sensors because the sensitivity (and not simply the signal intensity) of pyrene-based paints is dependent on the concentration of dye within the matrix.

With ruthenium-based paints using luminophores such as [Ru (dpp) ₃] Cl₂, dye aggregation is one of the most commonly encountered problems. Not only does this create an inhomogeneous distribution of dye in the sensor film, but the aggregates themselves are not sensitive to pressure. Aggregation is especially problematic in siloxane polymers. It is worth noting that the aggregation problems of ruthenium dyes may be related to their being ionic species, and hence difficult to dissolve in low-dielectric matrices. Certain PSP formulations are designed for ease of application and durability of the sensor films. Questions of paint adhesion and durability can often be addressed with additives, but whenever the paint formulation is modified, dye partitioning is a concern (i.e. will the dye be preferentially solva.ted by the additive?). For example, in order to improve a paint's durability, a blend of the permeable polymer with a second (film-forming) polymer may be desirable. If the luminophore is more soluble in the film-forming polymer than in the permeable polymer, however, the resultant sensor may lose sensitivity and/or have a slower response time.

Polymeric compounds of the present invention in which an iridium luminophore is covalently bound to a polymer may alleviate one or more of the problems associated with prior art PSPs. In addition, certain cyclometallated iridium complexes, even when not polymer bound, may alleviate one or more of the problems encountered by prior art PSPs. For example, iridium complexes, as opposed to ruthenium complexes, are uncharged and have higher quantum yields . Covalently bonding the iridium luminophore to the matrix material will reduce dye mobility and consequently reduce mobility-related drawbacks.

Reduction in mobility drawbacks permits greater flexibility in PSP formulation and the unimolecular nature of the polymeric compounds simplifies PSP formulation procedure since there is only one molecule with a single set of solubility parameters. In addition, dye aggregation is reduced since the tethered dye molecules will not be capable of translational motion independent of the matrix itself.

Blending of additional polymers with the polymeric compounds of the- present invention may be done to improve the characteristics of the resultant sensor (for example, film forming characteristics, adhesion, anti-fouling characteristics, etc.). For example, blending good film forming polymers, such as polystyrene, polymethacrylate, poly (methylmethacrylate) , nylon, polyethylene, etc., may be done to improve the film forming characteristics of the PSP formulation while maintaining a fast response time for the sensor.

In addition to additional blend polymers, other additives such as solvents, stabilizers, pigments (e.g. titania, silica, etc.), temperature sensors, etc. may be added to improve the properties of the PSP.

Brief Description of the Drawing

In order that the invention may be more clearly understood, preferred embodiments thereof will now be described in detail by way of example, with reference to the accompanying drawing in which:

Figure 1 depicts Stern-Volmer Calibration Curves for a dye-attached compound of the present invention and an unattached dye in various systems .

Description of Preferred Embodiments

A . Abbreviations

C 6 coumarin 6

DMPSEpy 4 - ( 2- ( dimethylphenylsilyl ) ethyl ) pyridine ppy 2 -phenylpyridine fppy 4 - ( 2-pyridyl ) benzaldehyde vacac allylacetoacetate vpy 4 -vinylpyridine vppy 2- ( 4 -vinylphenyl) pyridine or 2- ( 4 -styryl ) pyridine dpp 4 , 7 -diphenylphenanthroline phen 1 , 10-phenanthroline

PDMS polydimethylsiloxane

PS polystyrene

B . Materials

All reagents were used as received unless otherwise specified. All reagents and solvents were purchased from Aldrich, with the following exceptions: iridium (III) chloride hydrate (Strem); Karstedt's catalyst (platinum divinyltetramethyldisiloxane complex in xylene, 2.1-2.4% Pt) ; hydride terminated polydimethylsiloxane (Mn 55,000 - 70,000) (Gelest); and 2-ethoxyethanol (Caledon) .

Solvents were purified as follows: acetone (ACS Reagent grade) was distilled before use; diethyl ether (Anhydrous) and hexanes (Spectrograde) were dried over sodium and distilled and stored under nitrogen; dichloromethane (Laboratory grade) dried over calcium hydride and distilled and stored under nitrogen before use.

[Ir (ppy) ₂C1] ₂ and [Ir(C₆)₂Cl]₂ were prepared as outlined in Lamansky, S.; Djurovich, P.; Murphy, D.; Abdel- Razzaq, F.; Lee, H.-E.; Adachi, C; Burrows, P. E.; Forrest, S. R.; Thompson, M. E. J. Am . Chem . Soc , (2001), 123, 4304- 4312.

C. Synthesis of Unbound Iridium Complexes •

Example 1 : [Ir (ppy)•_ ( py) CI] , 1

4-Vinylpyridine (0.05 mL, 0.46 mmol, F.W. 105.14 g-mol^-1) was added to [Ir (ppy) ₂C1] ₂ (0.25 g, 0.23 mmol, F.W. 1072.11 g-mol^-1) in dichloromethane (20 mL) , and the resultant solution was refluxed under nitrogen for 3 days. After cooling to room temperature, toluene (20 mL) was added, the volume was reduced to 20 mL, and the solution was cooled for several hours in^' a freezer. The yellow microcrystalline product was collected by vacuum filtration, rinsed with 5 mL aliquots of toluene and hexanes, and dried in vacuo . [Ir (ppy) ₂ (vpy) CI] , 1 (0.21 g, 0.33 mmol, 70% yield, F.W. 641.19 g-mol^-1).

Elemental analysis as the monohydrate C₂₉H₂₃ClIrN₃-H₂0: %Calc'd C 52.68, H 4.12, N 6.35; %Found C 53.01, H 3.74, N 5.93.

K NMR (CD₂C1₂, 400 MHz): 9.77 (N6, IH, d, 5.8 Hz), 8.8 (V2,6, 2H, br) , 8.04 (N6', IH, d, 5.8 Hz), 7.85 (N3', 1H, d, 7.9 Hz), 7.70 (N3, IH, m) , 7.65 (N4', IH, m) , 7.64 (N4, IH, m) , 7.51 (P3'- IH, dd, 7.7 Hz), 7.46 (P3, IH, dd, 7.7 Hz), 7.15 (N5, IH, m) , 7.12 (V3,5, 2H, br . m) , 7.00 (N5", IH, ddd, 6.6 Hz), 6.81 (P4, IH, ddd, 7.5 Hz), 6.76 (P4', IH, ddd, 7.5 Hz), 6.71 (P5, IH, ddd, 7.4 Hz), 6.64

(P5', IH, ddd, 7.4 Hz), 6.53 (VA, IH, dd, 17.6 10.9Hz), 6.25 (P6, IH, d, 7.6 Hz), 6.08 (P6', IH, d, 7.6 Hz), 5.91 (VC, IH, d, 17.6 Hz), 5.46 (VB, IH, d, 10.9 Hz). Example 2a: 2- (4-vinylphenyl) pyridine, vppy

n-Butyllithium (18 mL, 1.5 M solution) was added dropwise through a septum into a flame-dried 3-necked round bottom flask containing a cloudy white suspension of methyl triphenylphosphonium bromide (9.75 g, 27 mmol, F.W. 357.24 g-mol^-1) in ether (20 mL) . The yellow mixture was stirred for 0.5 h. A solution of 4- (2-pyridyl) benzaldehyde (5g, 27 mmol, F.W. 183.21 g-mol^-1) in ether (20mL) was then added slowly over ten minutes, and the solution was refluxed for 0.5 hour under a nitrogen atmosphere. The solution was cooled, gravity filtered, and washed with ether (150 mL) . The filtrate was extracted with distilled water (3 x 100 mL) and the ether layer was collected and dried over MgS0₄. Solvent stripping to dryness resulting in a pale yellow oil (1.0 g, 5.5 mmol, 20% yield, F.W. 180.23 g-mol^-1).

^XH NMR (CD₂C1₂, 400 MHz): 8.66 (IH, m) , 8.00 (2H, d,.8.3 Hz), 7.77 (2H, m) , 7.53 (2H, d, 8.5 Hz), 7.23 (IH, m) , 6.78 (IH, dd, 17.6 Hz, 10.9 Hz), 5.85 (IH, dd, 17.6 Hz, 0.8 Hz), 5.30 (IH, dd, * Hz, 0.9 Hz) * couldn't be obtained due to overlap with signal due to solvent.

Example 2b : Alternate preparation of vppy

Potassium-tert-butoxide (21.8 mL, 1.0 M solution in THF) was added dropwise through a septum into a flame- dried Schlenk containing a cloudy white suspension of methyl triphenylphosphonium bromide (3.9 g, 10.91 mmol, F.W. 357.24 g-mol^-1) in ether (100 mL) . The yellow mixture was cooled in an ice/water bath and stirred for 0.5 hour. A solution of 4- (2-pyridyl) benzaldehyde (1 g, 5.46 mmol, F.W. 183.21 g-mol^-1) in ether (15 mL) was then added slowly over ten minutes via cannula. The resultant solution was shielded from light, allowed to gradually warm to room temperature, and stirred overnight. Distilled water (50 mL) was added to the solution, and the ether layer was separated and washed three times with aliquots of distilled water (3 x 50 mL) . The yellow ether layer was then dried over MgS0₄. Solvent stripping to dryness resulted in a pale yellow oil which was purified by column chromatography on silica gel, eluting with 15% ether in hexanes (0.47 g, 2.6 mmol, 47% yield, F.W. 180.23 g-mol^-1). Spectral analysis identical with the product of Example 2a.

Example 2c: [Ir (ppy) ₂ (vppy) ] , 2

2- (4-vinylphenyl) pyridine from Example 2a (l.Og, 5.5 mmol, F.W. 180.23 g-mol^-1), [Ir (ppy) ₂C1]₂ (0.8g, 0.75 mmol, F.W. 1072.11 g-mol^-1, and silver triflate (0.38 g, 1.5 mmol, 256.06 g-mol^-1) were all dissolved in 2-ethoxyethanol (15 mL) and heated under nitrogen on an oil bath to 95°C overnight. The deep yellow solution was cooled and gravity filtered to remove AgCl . The filtrate was solvent-stripped to dryness and was purified by column chromatography (silica gel) using 2:1 hexanes/ether as the eluent to remove unreacted vppy. The mobile phase was switched to 1:1 hexanes/ether to elute the bright yellow product band, which was solvent-stripped to dryness to yield [Ir (ppy) ₂ (vppy) ] 2 (0.09 g, 0.13 mmol, 18% yield, F.W. 680.83 g-mol^-1).

Elemental analysis as the monohydrate C₃5H₂N₃Ir-H₂0: %Calc'd C 60.15, H 4.04, N 6.01; %Found C 60.56, 4.12, 5.64) .

²H NMR (CD₂C1₂, 400 MHz): 7.91 (t, 3H, 8.3 Hz), 7.62 ( , 9H) , 7.00 (m, IH) , 6.89 (m, 5H) , 6.43 (dd, 1 H, 17.6 and 10.9 Hz), 5.45 (dd, IH, 17.6 and 2.7 Hz), 4.99 (dd, IH, 10.8 and 1.2 Hz) . Example 2d: [Ir (ppy) ₂ (vppy) ] , 2'

An attempt to synthesize [Ir (ppy) ₂ (vppy) ] using the procedure outlined in Example 3 (substituting vppy for vacac) yielded a product (2') in 70% yield having the following ^XH NMR:

^lΑ NMR (CD₂C1₂, 400 MHz): 8.12 (d, IH, 5.9 Hz), 7.93 (m, 2H) , 7.84 (d, 2H, 8.1 Hz), 7.68 (m, 6H) , 7.55 (m, 2H) , 7.09 (dd, IH, 8.3 and 1.9 Hz), 6.93 (m, 6H) , 6.83 (td, IH, 7.5 and 1.5 Hz), 6.77 (m, 2H) - 6.59 (d, IH, 6.9 Hz), 6.48 (dd, IH, 17.6 and 11.0 Hz), 6.43 (m, IH) , 5.49 (dd, IH, 17.6 and 1.3 Hz), 5.03 (dd, IH, 10.8 and 1.3 Hz) ppm.

Compound 2 as prepared in Example 2c has been assigned, on the basis of its ^XH NMR, as the facial isomer fac- [Ir (ppy) ₂ (vppy) ] . Compound 2' has a ^""-H NMR consistent with the meridional isomer mer- [Ir (ppy) ₂ (vppy) ] .

Example 3 : [Ir (ppy) ₂ (fppy) ] , 3

4- (2-Pyridyl) benzaldehyde (fppy) (1.0 g, 5.5 mmol, F.W. 183.21 g-mol^-1), [Ir (ppy) ₂C1] 2 (0.40 g, 0.37 mmol, F.W. 1072.11 g-mol^-1, and silver triflate (0.19 g, 0.75 mmol, 256.92 g-mol^-1) were all dissolved in 2-ethoxyethanol (25 L) and heated under nitrogen on an oil bath to 95°C overnight. The deep red solution was cooled and suction filtered through a fritted glass filter to collect a red product mixed with AgCl . Extraction of the mixed solids with CH₂CI₂ resulted in a deep red solution which was solvent stripped to dryness yielding a dark red powder. Column chromatography on silica gel with CH₂C1₂ eluted a yellow band of unknown composition. Continued elution with acetone yielded a red band which, upon solvent stripping and drying overnight in vacuo yielded [Ir (ppy) ₂ (fppy) ] 3 (0.26 g, 0.38 mmol, 51% yield, F.W. 682.80 g-mol^-1). ^XH NMR (CD₂C1₂, 400 MHz): 9.58 (s, IH) , 7.93 (d, IH, 8.1 Hz), 7.84 (d, 2H, 8.2 Hz), 7.71 (d, IH, 8.1 Hz), 7.6 (m, 6H) , 7.47 (m, 2 H) , 7.29 (dd, IH, 8.1 and 1.8 Hz), 7.17 (d, IH, 1.7 Hz), 6.94 ( , IH) , 6.8 (m, 7H) , 6.59 (dd, IH, 7.6 and 1 Hz) .

FTIR v(C=0) 1682 cm^-1.

Example 4 : [Ir (ppy) ₂ (vacac) ] , 4

[Ir (ppy)₂Cl]₂ (0.5g, 0.47 mmol, F.W. 1072.11 g-mol^-1), and silver triflate (0.13 g, 0.94 mmol, 256.06 g-mol^-1) were dissolved in acetone (40 mL) and refluxed under nitrogen for 2 hours . The cloudy yellow solution was cooled . and gravity filtered to remove AgCl . To the filtrate was added allylacetoacetate (vacac) (174 μL, 1.18 mmol) and triethylamine (0.5 mL) . The solution was then stirred overnight at room temperature under nitrogen. After solvent-stripping to dryness the dark yellow solid was purified on a short silica gel column, eluting with dichloromethane. The first bright yellow band was collected and solvent-stripped to dryness. The product was recrystallized by slow diffusion of hexanes into a concentrated dichloromethane solution, yielding a golden yellow microcrystalline solid [Ir (ppy) ₂ (vacac) ] 4 (330 mg, 0.514 mmol, 55% yield, F.W. 641.75 g-mol^-1) .

Elemental analysis as the semihydrate C₃₅H₂₆N₃Ir-0.5H₂O: %Calc'd C 53.53, H 4.03, N 4.30; %Found C 53.41, 3.83, 4.34) .

^XH NMR (d⁶-acetone, 400 MHz): 8.64 (m, 2H) , 8.08 (m, 2H) , 7.93 (m, 2H) , 7.65 (d, 2H, 8 Hz), 7.35 (m, 2H) , 6.76 (t, 2H, 7.6 Hz), 6.60 (m, 2H) , 6.23 (d, 2H, 7.6 Hz), 5.67 (m, IH) , 4.98 (m, 2H) , 4.73 (s, IH) , 4.25 (qtd, 2H, 12 Hz, 5.6 Hz, 1.5 Hz), 1.72 (s, 3H) . Example 5 : [Ir (C6) ₂ (vacac) ] , 5

[Ir(C6)₂Cl]₂ (0.2 g, 0.17 mmol, F.W. 1154.20 g-mol^-1, and silver triflate (0.09 g, 0.35 mmol, 256.06 g-mol^-1) were dissolved in acetone (40 mL) and refluxed under nitrogen for two hours. The cloudy orange solution was cooled and gravity filtered to remove AgCl . To the filtrate was added allylacetoacetate (vacac) (64 μL, 0.43 mmol) and triethylamine (0.5 L) . The solution was stirred overnight at room temperature under nitrogen. Solvent-stripping to dryness yielded a deep orange solid which was purified using a short silica gel column, eluting with ether. The first bright orange band was collected and solvent-stripped to dryness. The product was recrystallized by slow diffusion of hexanes into a concentrated dichloromethane solution, yielding red-orange. X-ray quality crystals [Ir (C6) ₂ (vacac) ] 5 (120 mg, 0.12 mmol, 34% yield, F.W. 1032.23 g-mol^"1).-

Elemental analysis as the monosolvate C35H_{26 3}Ir-CH₂Cl₂: %Calc'd C 51.61, H 4.06, N 5.02; %Found C 51.94, 4.02, 5.17) .

¹H NMR (d⁶-acetone, 400 MHz): 7.98 (t, 2H, 8Hz) ,

^■ 7.58 (d, IH, 8Hz), 7.46 (d, IH, 8Hz), 7.23 (m, 4H) , 6.19 (t, 2H, 2 Hz), 6.02 (dd, 2H, 9Hz, 2Hz),-5.91 ( , 2H) , 5.65 (m, IH) , 4.97 (m, 2H) , 4.38 (qtd, 2H, 17 Hz, 5 Hz, 1.5 Hz), 4.28 (s, IH) , 3.21 (dq, 8H,' 7 Hz, 2.6 Hz), 1.55 (s, 3H) , 0.90 (dt, 12H, 7 Hz, 2.5 Hz).

Example 6: [Ir (ppy) ₂ (DMPSEpy) CI] , 6

Dimethylphenylsilane (50 μL, 0.33 mmol, F.W. 136.27 g-mol^-1) was added to a solution of 1 (100 mg, 0.16 mmol, F.W. 641.19 g-mol^-1) in CH₂C1₂ (12 L) with Karstedt's catalyst (20 μL, 2.1% Pt solution in xylenes, ca. 1% relative to vinyl) . The resultant solution was refluxed under nitrogen for 24 hours. The product was then slightly concentrated and precipitated into hexanes to remove unreacted silane. The yellow precipitate was collected by vacuum filtration and purified by column chromatography on silica gel using 2:1 hexanes/acetone as the mobile phase, collecting the first yellow band. The eluate was solvent stripped to dryness and the yellow product dried in vacuo [Ir (ppy)₂(DMPSEpy)Cl] 6 (31 mg, 0.04 mmol, 25% yield, F.W. 777.46 g-mol^-1) .

Elemental analysis as the monohydrate

C₃₇H₃₅ClIrN₃Si-H₂0: %Calc'd C 55.87, H 4.69, N 5.28; %Found C 55.49, H 4.45, N 5.16.

^XH NMR (CD₂C1₂, 400 MHz): 9.85 (N6, IH, d, 5.2 Hz), 8.8 (V2,6, 2H, br), 8.10 (N6', IH, d, 5.1 Hz), 7.92 (N3', IH, d, 8.3 Hz), 7.78 (N3, IH, m) , 7.74 (N4 ' , IH, m) , 7.72 (N4, IH, m) , 7.60 {P3', IH, dd, 7.8 Hz), 7.54 (P3, IH, dd, 7.7 Hz), 7.48 (Si-P.2, IH, m) , 7.34 (Si-Pn, 2H, m) , 7.23 (N5, IH, m) , 7.07 (N5', IH, m) , 7.02 (V3,5, 2H, br) , 6.88 (P4, IH, ddd, 7.5 Hz), 6.84 (P4', IH, ddd, 7.6 Hz), 6.78 (P5, IH, ddd, 7.4 Hz), 6.72 (P5^', IH, ddd, 7.4 Hz), 6.33 (P6, IH, d, 7.6 Hz), 6.16 (P6", IH, d, 7.6 Hz), 2.54 (C___CH₂Si, 2H, m) , 1.03 (CH₂CJΪ₂Si, 2H, m) , 0.26 (Si-Cffe, 6H, s) .

^•29Si (de-acetone, 80 MHz) -5.8

D. Synthesis of Polymer Bound Iridium Complexes

Example 7 : Attachment of 1 to hydride terminated PDMS, yielding dye-attached polymer 7

A solution of 1 (50 mg,. 0.08 mmol, F.W. 641.19 g-mol^-1) in CH₂C1 (5 mL) was added to a solution of hydride terminated polydimethylsiloxane (PDMS) (4 g, 0.06 mmol, Mn=55-70 kDa) in CH₂C1₂ (10 mL) with Karstedt's catalyst (10 μL, ca. 1% relative to vinyl). The resultant solution was stirred at reflux under nitrogen for 2 days and solvent stripped to dryness. The product was dissolved in a small volume of hexanes and was filtered sequentially through 1.0 μm and 0.45 μm Gelman Acrodiscs™ to remove unreacted complex. A clear, yellow solid was obtained by dropwise addition of the filtered solution to rapidly stirred methanol. Precipitation of concentrated hexanes solutions into methanol were performed two or three times . The supernatant liquors typically appear colourless. When this was not the case, serial precipitations were continued until a colourless supernatant was obtained.

Example 8 : Attachment of 2 to hydride terminated PDMS, yielding dye-attached polymer 8

Preparation of dye-attached polymer 8 based on compound 2 was done in a similar manner to Example 7.

Example 9 : Attachment of 3 to hydride terminated PDMS, yielding dye-attached polymer 9

A solution of 3 (38 mg, 0.056 mmol, F.W. 682.80 g-mol^-1) in CHC1₂ (5 L) was added to a solution of aminopropyl terminated polydimethylsiloxane (PDMS) (3 g, 0.11 mmol, Mn=27 kDa) in CH₂C1₂ (10 mL) . The resultant solution was stirred at reflux under nitrogen for 2 days and solvent stripped to dryness. The product was dissolved in a small volume of hexanes and was filtered sequentially through 1.0 μm and 0.45 μm Gelman Acrodiscs™ to remove unreacted complex. A clear, red-orange solid was obtained by dropwise addition of the filtered solution to rapidly- stirred methanol. Precipitation of concentrated hexanes solutions into methanol were performed three times. The colour of the supernatant liquors were faint red initially and colourless after the final precipitation.

Example 10: Attachment of 4 to hydride terminated PDM_.S, yielding dye-attached polymer 10

Preparation of dye-attached polymer 10 based oh compound 4 was done in a similar manner to Example 7.

Example 11: Attachment of 5 to hydride terminated PDMS, yielding dye-attached polymer 11

Preparation of dye-attached polymer 11 based on compound 5 was done in a similar manner to Example 7.

Example 12 : Attachment of 1 to PDMS-PS block copolymer

A solution of 1 in CH₂C1₂ is added to a solution of hydride functionalized dimethylsiloxane (DMS) monomer in CH₂CI₂ with Karstedt's catalyst (ca. 1% relative to vinyl). The resultant solution is stirred at reflux under nitrogen and the solvent eventually stripped to dryness. Solid dimethylsiloxane monomer bearing covalently bound iridium complex is copolymerized with styrene by sequential anionic polymerization in a manner similar to the one described in Lee, J.; Hogen-Esch, T. E. Macromolecules, (2001) 34, 2095- 2100, which is herein incorporated by reference. The resulting poly (dimethylsiloxane) -polystyrene block copolymer bearing covalently bound iridium complexes is recovered. The block copolymer is blended with additional polystyrene to improve mechanical characteristics of the paint. E . Mechanical Mixtures of Iridium Complexes and Polymers

Example 13: Dissolution/precipitation of a mixture of 1 and PDMS

A mixture of solid compound 1 and hydride- terminated PDMS were dissolved in CH₂Cl₂ to form a homogeneous solution which was subsequently solvent stripped to dryness resulting in a cloudy yellowish suspension of complex in polymer. Dissolution of the mixture in hexanes resulted in a cloudy solution which was microfilte ed through a 1.0 μm Gelman Acrodisc™ (or filtered through a kimwipe plug in a pasteur pipette) . A clear, colourless siloxane fluid was obtained after solvent-stripping.

Example 14 : Dissolution/precipitation of a mixture of 4 and PDMS

The procedure of Example 13 was repeated for compound 4 except that a clear yellow solid was formed instead of a cloudy yellowish suspension when the initial CHC1₂ solution was solvent stripped to dryn'ess. After dissolution in hexanes and filtration, a clear colourless silicone fluid was obtained.

In both Examples 13 and 14, the siloxane fluid contains suspended iridium complexes 1 or 4, rather than iridium complexes covalently bound to the polymer as described in Examples 7-12. However, the mixtures formed in Examples 13 and 14 can also be used as a pressure sensitive paint . The following is a summary of the numbering scheme used to label various compounds of the examples:

1 [Ir(ppy)₂(vpy)Cl]

2 [Ir (ppy) ₂ (vppy) ] 3 . [Ir (ppy) ₂ (fppy) ]

4 _. [Ir (ppy) ₂ (vacac) ]

5 [Ir(C6)₂(vacac) ]

6 [ Ir (ppy) ₂ ( DMPSEpy) Cl ]

7 . 1-PDMS (indicating dye attached to PDMS) 8 2-PDMS (indicating dye attached to PDMS)

9 3-PDMS (indicating dye attached to PDMS)

10 4-PDMS (indicating dye attached to PDMS)

11 5-PDMS (indicating dye attached to PDMS)

F. Evaluation of 1-6 and 7-11 as Oxygen Sensors

The oxygen sensitivity of the attached and unattached luminophores was compared by evaluating samples of 1-5 dispersed within the same siloxane polymer to which they were attached to form 7-11 with samples 7-11. The oxygen sensitivity of sample 6 was evaluated dispersed in the PDMS, PS or a 1:1 PDMS/PS mixture. A corresponding dye- attached system for sample 6 was not evaluated. Samples of 1-6 were combined with an appropriate amount of polymer such that the concentration of luminophore by weight of polymer was equivalent in related attached and unattached systems (i.e. 1 and 7, 2 and 8, etc.) . Because 1-6 are not soluble in toluene, those samples were dissolved (with the siloxane polymer) in CH₂C1₂ whereas the samples of 7-11 were dissolved in toluene. In all other respects the dispersed and attached samples were treated equivalently. Where blends with polystyrene (or additional PDMS) were made all components were dissolved to make a homogeneous solution in ' a single solvent before application. The mass ratios of the two components are indicated in Table 2.

A solution of the sample was applied to an aluminum plate previously covered with a layer of Tristar Starpoxy™ fluid resistant white epoxy primer (DHMS C4.01 Ty3) using a conventional airbrush and compressed nitrogen as the propellant. The painted plate was then mounted in an in-house designed pressure chamber. Pressure was controlled via a Scanivalve Corp model PCC100 Pressure Calibrator/Controller in manual mode, and the temperature of the mounting plate was controlled via a thermoelectric cooler coupled to a model LFI-3551 Temperature Controller using a model TCS650 thermistor in the 10 μA range, both from Wavelength Electronics. Excitation in the UV was provided by a Hamamatsu Lightningcure™ LC5 200W model L8333 Hg/Xe source via a 10 m x 8 mm Oriel UV-Vis Liquid Light Guide (transmission window 300-650 nm) . The source was equipped with 011FG09 and 300FS40 filters by Melles-Griot , transmitting approximately in the range 280-320 nm. Excitation in the blue was provided by a Photonics Research Systems PRS100B blue LED lamp equipped with a 420-500 nm bandpass filter (03-FIV-28, Melles Griot) . The stability of the intensity of both excitation sources has been previously established. Emission was measured with a 512x512 Photometries CH350 12 bit CCD camera with an appropriate filter: e.g. for 1 and 7 a 500 ± 40 nm bandpass filter (500FS80-50, Melles Griot); for 5 and 11 a 600 ± 40 nm bandpass filter (03-FIB-012, Melles Griot) . Measurements were taken at various pressures in the range 0.05-45 psi and at various temperatures in the range 10-30 °C. For each calibration, a second reading was obtained at 15 psi at the end of each experiment to determine whether the sample was photodegrading on the timescale of the experiment. Spectra were also collected for various calibrations using an Acton Research Corporation Spectrumm CCD Detection System consisting of a SpectraPro-150 Imaging Dual Grating Monochromator/Spectrograph with a 16 bit Hamamatsu 1024x256 CCD. The spectral signal was captured using a fiber optic. Unless otherwise indicated, the spectra were obtained using a 450 nm cutoff filter (Kodak #3 long-pass filter) . Additional (bandpass) filters were occasionally used if these did not overly alter the emission bandshape.

Table 2 illustrates results obtained. Comparative example UT1 is a dye-dispersed paint of [Ru (dpp) ₃] Cl₂ in poly (thionylphosphazene) . Comparative example UT2 is a [Ru (phen) ₃] (PFβ)₂ luminophore attached to polysiloxane using the same hydrosilation as used for iridium paints 7-11 of the present invention. UT2 is thus a very close analogue of paint 8. Comparative example FIB7 is a commercial pressure sensitive paint based on platinum tetrafluorophenyl porphyrin.

Table 2 - Oxygen Sensitivity Data

Table 2 - continued

Table 2 - continued

Table 2 - continued

[Ir(ρpy)₃] dispersed samples can be directly compared to 8, as the dye is of the same form in each sensor.

[Ru (phen) ₂ (vphen) ] Cl₂ is the dye used to make UT2, and is approximately equivalent to [Ru (phen) ₃] CI₂.

ml is the slope of the Stern-Volmer plot between 0 and 5 psi, m2 the slope between 10 and 20 psi, and m3 the slope from 25-45 psi.

Qs is the slope of the Stern-Volmer-type plot of Iref/I vs. P/Pref. It is generally a number between 0 and 1, although it may be greater than 1, and is a measure of the percent intensity loss per atmosphere of total pressure when the luminophore is exposed to air. That is, it may be considered a quenching factor. The Q_s value is referenced to 1 atm (actually to 15.0 psi) . Qs is determined from a linear regression of either a linear part of the Stern-Volmer-type plot or a best fit straight _.line drawn through the data points. A high Q_s value indicates significant loss of luminescence intensity due to the presence of oxygen. A high Qs value is generally good as a large difference in intensity between the unquenched and quenched luminophore is easier to detect. However, if the Qs value is too high, then the absolute luminescence intensity is too low to measure. Therefore, a Q_s value between 0.4 and- 0.7 is considered ideal. The optimum Q_s value depends to some extent on the use to which the luminophore is put.

R² is the linear regression linearity of the Stern- Vol er plot. Many plots exhibit downward curvature resulting in low R² values .

Oxygen sensitivity (Q_s) of 7 was- measured on thin films of 7 itself as well as on films of 7 blended with polystyrene in both 1:1 and 1:9 ratios. These data were compared with calibrations on 1 dispersed in the same hydride-terminated PDMS used in the synthesis of 7, in polystyrene, and in a 1:1 mixture of PDMS and PS. The quenching sensitivity data are listed in Table 2 and the

Stern Volmer calibration curves are illustrated in Figure 1.

The sensitivity of the sensor was highest at low pressures, and became essentially linear at total pressures above 25 psi. The maximal sensitivity (see Table 2) of a freshly prepared sample of 7 was 0.619 in the low pressure range 0-5 psi, decreasing to 0.152 in the range 10-20 psi, and finally flattening out to a linear response of 0.0663 at pressures of 25 psi and greater. Such downward curvature may be ascribed to the dye being solvated in different microenvironments within the polymer matrix having different accessibility to oxygen. Thus at low pressures only the most accessible luminophore molecules interact with oxygen, leading to high sensitivity, whereas at higher pressures the easily accessible luminophore molecules are largely quenched.

From Table 2, it is clear the oxygen sensitivity of the PDMS-bound luminophore 7 is much higher throughout the pressure ranges than the oxygen sensitivity for unbound luminophore 1 dispersed in PDMS. The same relationship holds when polystyrene is additionally used as a blend polymer. The results clearly indicate that binding an iridium luminophore to a polymeric, compound improves the oxygen sensitivity of a pressure sensitive paint.

In addition, the advantage of having the iridium luminophore covalently bound to a polymeric compound is further demonstrated by the improvement in the sensor 7's behaviour upon blending with polystyrene. Not only are the sensor's film forming properties improved upon blending, but also their oxygen sensitivity. This latter improvement was a valuable and unanticipated benefit of luminophore attachment .

When comparing 1 blended with polystyrene to 1 blended with both polystyrene and PDMS, it is evident from Table 2 that the oxygen sensitivity is similar to the data for 1 in polystyrene when both PDMS and polystyrene are present in the blend. This is likely due to the preferential solubility of 1 in polystyrene. However, when 1 is attached to PDMS (i.e. sensor 7) rather than blended with PDMS, the oxygen sensitivity only increases in a polystyrene blend.

Roughly equivalent behaviour can be inferred for 11 in comparison with sensors based on dispersions of 5.

Here,- again, blending 11 with polystyrene leads to dramatic improvement in sensitivity. To our knowledge, compound 5 has never been previously investigated for oxygen sensing, and demonstrates significant sensitivity when dispersed in PS. Polystyrene blends of 11 are roughly equivalent in sensitivity to dispersions of 5 in PS, but have significantly faster response times, due to the presence of the highly permeable PDMS, which must remain in intimate contact with the luminophore due to their covalent link. Polystyrene has a very low permeability to oxygen, and thus forms sensors with extremely slow (several tens of seconds to minutes) response times.

Directly comparing a given iridium sensor with an analogous ruthenium sensor (e.g. 8 with UT2) indicates that the iridium luminophore provides a significantly higher oxygen sensitivity than a structurally similar ruthenium complex when both are attached to the same polymer. At the same time, 8 has a significantly higher quantum yield than the [Ru(phen)₃] (PF6) luminophore used in UT2, resulting in greater sensor brightness for roughly equivalent luminophore concentrations. It can also be seen that the paint UTl, which is a luminophore-dispersed paint using the very sensitive complex [Ru (dpp) ₃] Cl₂, has a lower sensitivity than 8. However, the matrix polymer used in UTl (polythionlylphosphazene) is not the same as that used for 8. [Ru (dpp) ₃] Cl₂ is more sensitive to oxygen in polythionlylphosphazene than in PDMS.

Since a given luminophore' s sensitivity is dependent upon its microenvironment (i.e. the polymer in which it finds itself) , the benefit of attaching a luminophore is best assessed by comparing data in a given matrix material. Similarly, in a given matrix material comparisons are best drawn between members of the same broad class of luminophores (e.g. transition metal complexes, etalloporphyrins, or polycyclic aromatic hydrocarbons) owing to the great differences in the physical properties of members of each of these classes.

In general, it is evident from Table 2 that iridium-based luminophores generally perform well and can outperform related ruthenium-based luminophores in several different ways. Furthermore, it is evident from Table 2 that the quenching sensitivity of luminophore-attached compounds of the present invention are significantly and unpredictably improved in relation to the corresponding non- attached luminophores .

Having thus specifically described the invention, it will be evident to one skilled in the art that modifications may be made which are encompassed by the scope of the invention claimed hereafter.

Claims

CLAIMS :

1. A polymeric compound comprising an iridium luminophore, having luminescence sensitive to oxygen concentration, covalently bound to a polymer.

2. A compound according to claim 1 of formula (I) :

P-(Z_rU)n (I),

wherein P is a polymer backbone, U is an iridium luminophore, Z is a linker between the polymer backbone and the iridium luminophore, m is an integer from 1 to 3, and n is an integer from 1 to 5000.

3. A compound according to claim 2, wherein m is 1.

4. A compound according to claim 2 or 3, wherein n is an integer from 1 to 500.

5. A compound according to claim 2 or 3, wherein n is an integer from 1 to 100.

6. A compound according to claim 2 or 3, wherein n is an integer from 1 to 2.

7. A compound according to any one- of claims 2 to 6, wherein the linker is a covalent bond, a fragment of a functional group covalently bonded to both the polymer backbone and the iridium luminophore, or a combination thereof.

8. A- compound according to any one of claims 2 to 6, wherein the linker comprises a fragment of a vinyl, a carbonyl, a thiocarbonyl, a carboxylic acid, a carboxylate, a thiocarboxylic acid, a thiocarboxylate, an amine, an amide, a thiol, a- hydroxyl, an epoxide, an alkyl halide, a hydride, an anhydride, an acid chloride, an isocyanate or an isothiocyanate group, or a combination thereof.

9. A compound according to any one of claims 2 to 6, wherein the linker comprises a fragment of a vinyl group.

10. A compound according to any one of claims 2 to 6, wherein the linker is an alkyl, an ether, an amine, an i ine, a urea, a thiourea, a urethane, an amide, an ester, or an imide group or a combination thereof.

11. A compound according to any one of claims 1 to 10, wherein the iridium luminophore is a complex of iridium with an organic ligand.

12. A compound according to any one of claims 1 to 10, wherein the iridium luminophore is a complex of iridium with a bidentate and/or a tridentate organic ligand.

13. A compound according to claim 11 or 12, wherein the organic ligand is conjugated.

14. A compound according to any one of claims 1 to 13, wherein the iridium luminophore is electrically neutral.

15. A compound according to any one of claims 1 to 10, wherein the iridium luminophore is an iridium complex of formula (II) :

[Ir(C-N)₂LX] (II),

16. A compound according to claim 15, wherein the C-N ligands comprise at least one aromatic moiety.

17. A compound according to any one of claims 15 to 16, wherein L and X together form a monoanionic monodentate ligand which is a β-diketonate ligand.

18. A compound according to claim 17, wherein the β-diketonate ligand is 2, 4-pentanedionate (acac) or 3- substituted-2, 4-pentanedionate, wherein the substituent is methyl, ethyl, propyl or butyl.

19. A compound according to any one of claims 15 to

18, wherein the linker is covalently bound to the iridium complex through the monoanionic bidentate ligand.

20. A compound according to any one of claims 15 to

19, wherein the linker is covalently bound to the iridium complex through one or more of the C-N ligands .

21. A compound according to any one of claims 1 to 10, wherein the iridium luminophore is a complex of iridium comprising one or more ligands selected from the group consisting of 2-phenylpyridinato, 4 , 7-diphenyl-l, 10 ' - phenanthroline, coumarin 6, 2, 2-bipyridine, 2- (2 ' -thienyl) pyridinato, 2-phenyloxazolinato, 2- (2 ' -benzothienyl) pyridinato, 2, 4-diphenyloxazolato, 2- (1-naphthyl) enzooxazolato and 2- (2-naphthyl) enzothiazolato.

22. A compound according to any one of claims 1 to 21, wherein the polymer is a homopolymer, copolymer and/or terpolymer of a polysiloxane, a polyolefin, a polycarbonate, a polyimide, a polyethersulfone, a polyetherketone, a polypeptide, a polynucleic acid, a polymer of a cellulose derivative, a polymer of a phosphazene derivative, or a combination thereof.

23. A compound according to any one of claims 1 to 21, wherein the polymer is poly (dimethylsiloxane) , polystyrene, poly (dimethylsiloxane) -polystyrene block copolymer, poly (thionylphosphazene) , poly (n-butylamino thionylphosphazene) , polyvinyl chloride, polyoxyethylene, polyethylene, polypropylene, polyacrylic acid, polymethacrylic acid, poly (methylmethacrylate) , poly-2-hydroxyethylmethacrylate, poly (fluoromethacrylate) , poly (tetrafluoroethylene) (PTFE) , poly (vinylacetate) (PVA) , poly (ethylene terephthalate), cellulose acetate butyrate (CAB) , poly (hexafluoroisopropyl-co-heptafluoro-n- butylmethacrylate) (FIB), or a combination thereof.

24. A compound according to any one of claims 1 to 21, wherein the polymer is a polysiloxane or a poly (fluoroalkylmethacrylate) .

25. A compound according to any one of claims 1 to 21, wherein the polymer is pol (dimethylsiloxane) or poly (dimethylsiloxane) -polystyrene block copolymer).

26. A compound according to any one of claims 1 to 21, wherein the polymer is pol (hexafluoroisopropyl-co- heptafluoro-n-butylmethacrylate) (FIB) .^'

27. Use of a compound according to any one of claims 1 to 26 as an oxygen sensor.

28. Use of a compound according to any one of claims 1 to 26 as a pressure sensitive paint.

29. An oxygen sensor formulation comprising a compound according to any one of claims 1 to 26 and an additive.

30. An oxygen sensor formulation according to claim 29, wherein the additive is a solvent, a stabilizer, a pigment, a blend polymer, a temperature sensor, or a combination thereof.

31. An oxygen sensor formulation according to claim 30, wherein the blend polymer is polystyrene, polymethacrylate, poly (methylmethacrylate) ,. nylon, polyethylene or a combination thereof.

32. A method for detecting and/or measuring the presence and/or amount of oxygen in an environment comprising:

(a) contacting a compound according to any one of claims 1 to 26 or a paint according ^"to any one of claims 29 to 31 with an environment;

(b) detecting and/or measuring a change in luminescence of the compound; and,

(c) correlating the change in luminescence to the presence and/or amount of oxygen in the environment.

33. A method according to claim 32, wherein the

, presence and/or amount of oxygen is correlated to pressure of oxygen in the environment.

34. A method according to claim 33, wherein the pressure of oxygen is correlated to total pressure of a gas or mixture of gases in the environment.

35. A compound of formula (III):

[Ir(C-N)₂LX] (F^x)_p (III)

wherein C-N is a conjugated cyclometallating ligand, L is a monodentate ligand, X is a monoanionic monodentate ligand, or L and X taken together form a monoanionic bidentate ligand or a C-N ligand, F¹ is a functional group suitable for bonding to a polymer or monomer,, and p is an integer from 1 to 3.

36. The compound according to claim 35, wherein p is 1.

37. A compound according to claim 35 or 36, wherein the C-N ligands comprise at least one aromatic moiety.

38. - A compound according to claim 35 or 36, wherein each C-N is independently selected from the group consisting of 2-phenylpyridinato, coumarin 6, 2- (2 ' -thienyl) pyridinato, 2-phenyloxazolinato, 2- (2 ' -benzothienyl) pyridinato,

2, 4-diphenyloxazolato, 2- (1-naphthyl) benzooxazolato, and 2- (2-naphthyl) benzothiazolato.

39. A compound according to any one of claims 35 to 38, wherein L and X together form a monoanionic monodentate ligand which is a β-diketonate ligand.

40. A compound according to claim 39, wherein the β-diketonate ligand is 2, 4-pentanedionate (acac) or 3-substituted-2, 4-pentanedionate, wherein the substituent is methyl, ethyl, propyl or butyl.

41. A compound according to any one of claims 35 to

40, wherein F¹ comprises a vinyl, a carbonyl, a thiocarbonyl, a carboxylic acid, a carboxylate, a thiocarboxylic acid, a thiocarboxylate, an amine, an amide, a thiol, a hydroxyl, an epoxide, an alkyl halide, a silicon hydride, an anhydride, an acid chloride, an isocyanate or an isothiocyanate group, or a combination thereof.

42. A compound according to any one of claims 35 to 40, wherein F¹ comprises a vinyl group.

43. A process comprising a hydrosilation reaction between a vinyl functionalized iridium complex and a hydride functionalized polysiloxane to form a polysiloxane bearing covalently bound iridium complexes.

44. A process comprising a hydrosilation reaction between a vinyl functionalized iridium complex and a hydride functionalized siloxane monomer to form a siloxane monomer bearing a covalently bound iridium complex.

45. A process according to claim 44, further comprising polymerizing the siloxane monomer bearing a covalently bound iridium complex to form a polysiloxane bearing covalently bound iridium complexes.

46. A process according to claim 45, wherein the siloxane monomer bearing a covalently bound iridium complex is copolymerized with another monomer to form a copolymer bearing covalently bound iridium complexes .

47. A process according to claim 46, wherein the other monomer is styrene.

48. A process according to any one of claims 44 to 47, wherein the siloxane monomer is dimethylsiloxane.

49. .A process according to any one of claims 43 to 48, wherein a catalyst is used to catalyze the hydrosilation reaction .

50. A process according to claim 49, wherein the catalyst is a platinum complex or salt.

51. A process according to any one of claims 43 to 50, wherein the iridium complex is a luminophore having luminescence sensitive to oxygen concentration.

52. A process according to any one - of claims 43 to 50, wherein, the iridium complex is a compound of formula (IV) :

[Ir(C-N)₂LX] (F²)_q (IV)

wherein C-N is a conjugated cyclometallating ligand, L is a monodentate ligand, X is a monoanionic monodentate ligand, or L and X taken together form a monoanionic bidentate ligand or a C-N ligand, F² is a functional group comprising a vinyl group, and q is an integer from 1 to 3.

53. The process according to claim 52, wherein q is 1.

54. A process according to claim 52 or 53, wherein the C-N ligands comprise at least one aromatic moiety.

55. A process according to claim 52 or 53, wherein each C-N is independently selected from the group consisting of 2-phenylpyridinato, coumarin 6, 2- (2 ' -thienyl) pyridinato, 2-phenyloxazolinato, 2- (2 ' -benzothienyl) pyridinato,

2, 4-diphenyloxazolato, 2- (1-naphthyl) benzooxazolato and 2- (2-naphthyl) benzothiazolato.

56. A process according to any one of claims 52 to 55, wherein L and X together form a monoanionic monodentate ligand which is a β-diketonate ligand.

57. A process according to claim 56, wherein the β-diketonate ligand is 2, 4-pentanedionate (acac) or 3-substituted-2, 4-pentanedionate, wherein the substituent is methyl, ethyl, propyl or butyl.

58. A process according to any one of claims 52 to 57, wherein F² comprises a vinyl group bound to a C-N ligand.

59. A process according to any one of claims 52 to 57, wherein F² comprises a vinyl group bound to the monoanionic bidentate ligand.

60. Iridium bis (2-phenylpyridine) (4-vinylpyridine) chloride .

61. Iridium bis (2-phenylpyridine) (2-(4- vinylphenyl) pyridine) .

62. Iridium bis (2-phenylpyridine) (allylacetoacetate) .

63. Iridium bis (coumarin 6) (allylacetoacetate) .

64. A polymeric compound which is a reaction product between a compound according to any one of claims 60 to 63 and a hydride functionalized polysiloxane.

65. The compound according to claim 64, wherein the polymer is hydride terminated polydimethylsiloxane.

66. A monomeric compound which is a reaction product between a compound according to any one of claims 60 to 63 and a hydride functionalized siloxane.

67. A polymeric compound formed by polymerization of the monomeric compound according to claim 66.

68. A polymeric compound formed by copolymerization of the monomeric compound according to claim 66 and styrene.

69. A pressure sensitive paint formulation comprising a compound according to claim 64, 65, 67 or 68 and an additive.

70. The formulation according to claim 69, wherein the additive is a solvent,- a stabilizer, a pigment, a blend polymer, a temperature sensor, or a combination thereof.

71. The formulation according to claim 70, wherein the blend polymer is polystyrene.