DE102011000282A1 - Shifting the emission wavelength of a metal complex emitting in a given wavelength, to a wavelength which is greater than the given wavelength, useful in e.g. organic diodes, comprises embedding the metal complex into a polymer matrix - Google Patents

Abstract

The invention relates to a method for increasing the Stokes shift of an emitting metal complex having a given geometry in the region of the metal center in the electronic ground state, which changes by optical excitation or excitation by a hole-electron recombination, and a polymeric matrix , which can influence the geometry change in the excited state.

Description

The invention relates to the use of mono- or binuclear metal complexes as emitters with variable emission colors, in particular in OLEDs (organic light-emitting diodes) and in other opto-electronic components.

introduction

Currently, new processes are being implemented in the area of screen and lighting technology. It will be possible to produce flat displays or illuminated areas with a thickness of less than 0.5 mm. These are distinguished by many fascinating properties. So z. B. lighting surfaces can be realized as wallpaper with very low energy consumption. But it is particularly interesting that color screens with hitherto unattainable color authenticity, brightness and viewing angle independence, with low weight and very low power consumption will be produced. The screens can be designed as micro-displays or large screens with several square meters of surface in rigid form or flexible, but also as transmission or reflection displays. Furthermore, it will be possible to use simple and cost-saving production methods such as screen printing or inkjet printing. As a result, a very inexpensive production is possible compared to conventional flat screens. This new technology is based on the principle of OLEDs, Organic Light Emitting Diodes. In addition, the use of special metal-organic materials (molecules) many new opto-electronic applications, eg. As in the field of organic solar cells, organic field effect transistors, organic photodiodes, etc. from.

Thus, it can be seen, especially for the OLED sector, that such arrangements are already economically significant, since mass production is to be expected shortly. Such OLEDs consist predominantly of organic layers, which are also flexible and inexpensive to manufacture. OLED components can be designed over a large area as lighting fixtures, but also as small pixels for displays.

Compared to conventional technologies, such as liquid crystal displays (LCDs), plasma displays or cathode ray tubes (CRTs), OLEDs have numerous advantages, such as a low operating voltage of a few volts, a thin structure of several hundred nm, high-efficiency self-luminous pixels , a high contrast and a good resolution as well as the possibility to display all colors. Furthermore, in an OLED light is generated directly when applying electrical voltage, instead of only modulating it.

An overview of the function of OLEDs can be found, for example H. Yersin, Top. Curr. Chem. 2004, 241, 1 and H. Yersin, "Highly Efficient OLEDs with Phosphorescent Materials"; Wiley-VCH, Weinheim, Germany, 2008 ,

Since the first reports on OLEDs (see eg Tang et al., Appl. Phys. Lett. 1987, 51, 913 ), these devices have been further developed, in particular with regard to the emitter materials used, in which so-called triplet or other phosphorescent emitters are of particular interest in recent years.

OLEDs are usually realized in layer structures. For better understanding is in 1 a basic structure of an OLED shown. Due to the applied external voltage on a transparent indium-tin-oxide anode (ITO) and a thin metal cathode are injected from the anode positive holes and the cathode negative electrons. These differently charged charge carriers enter the emission layer via intermediate layers, which may also include here not drawn hole or electron blocking layers. There, the oppositely charged charge carriers meet at or near doped emitter molecules and recombine. The emitter molecules are typically incorporated into matrix molecules or polymer matrices (eg, from 2 to 20% by weight), with the matrix materials chosen to also facilitate hole and electron transport. The selection of the matrix is of particular importance in the context of this invention, as will be explained below. The recombination produces excitons (= excitation states), which transfer their excess energy to the respective electroluminescent compound. This electroluminescent compound can then go into a specific electronic excited state, which is then converted as completely as possible and largely avoiding radiation-free deactivation processes by emitting light in the associated ground state.

As an electronic excitation state, which can also be formed by energy transfer from a suitable precursor exciton, there is, with a few exceptions, either a singleton or a triplet state consisting of three sub-states, into consideration. Since both states are usually occupied in a ratio of 1: 3 due to the spin statistics, it follows that for an emission from the singlet state, which is referred to as fluorescence, only a maximum of 25% of the excitons produced lead to emission again. In contrast, in a triplet emission, which is referred to as phosphorescence, all excitons are exploited, converted and emitted as light (triplet harvesting), so that in this case the internal quantum efficiency can reach the value of 100%, if the excited with and energetically over the triplet state singlet state completely relaxed in the triplet state (inter-system crossing, ISC) and radiationless competition processes remain meaningless. Thus, prior art triplet emitters are more efficient electro-luminophores and more suitable for providing high light output in an organic light emitting diode.

The triplet emitters suitable for triplet harvesting typically employ transition metal complex compounds in which the metal is selected from the third period of the transition metals. These are predominantly very expensive precious metals such as iridium or platinum. (See also H. Yersin, Top. Curr. Chem. 2004, 241, 1 and MA Baldo, DF O'Brien, ME Thompson, SR Forrest, Phys. Rev. B 1999, 60, 14422 ). The main reason for this is the high spin-orbit coupling (SBK) of the noble metal central ions (SBK constant Ir (III): ≈ 4000 cm ^-1 , Pt (II): ≈ 4500 cm ^-1 ; SL Murov, J. Carmicheal, GL Hug, Handbook of Photochemistry, 2nd Edition, Marcel Dekker, New York 1993, p. 338 ff ). By virtue of this quantum mechanical property, the triplet-singlet transition strictly forbidden for optical transitions without SBK is allowed and the short emission lifetime of a few μs required for the OLED application is achieved.

It would be of great economic benefit if these expensive precious metals could be replaced by cheap metals. In addition, a variety of previously known OLED emitter materials from an environmental point of view is not safe, so that the use of less toxic materials would be desirable. For this z. As copper (I) -, silver (I) - and gold (I) complexes into consideration. However, especially of these central ions Cu (I) and Ag (I) have a significantly lower SBK (SBK constants of Cu (I): 850 cm ^-1 , Ag (I): ≈ 1780 cm ^-1 , Au (I) : ≈ 5100 cm ^-1 ; Ref .: SL Murov, J. Carmicheal, GL Hug, Handbook of Photochemistry, 2nd Edition, Marcel Dekker, New York 1993, p. 338 ff ), as the above-mentioned central ions. Thus, the very important triplet-singlet transitions of Cu (I) or Ag (I) complexes would be relatively forbidden, and emission lifetimes would be too long for OLED applications with some 100 μs up to several ms. With such long emission decay times, saturation effects arise with increasing current densities and the resulting occupation of a majority or all of the emitter molecules. As a result, further charge carrier currents can no longer completely lead to the occupation of the excited and emitting states. This results in only stronger unwanted ohmic losses. As a result, as the current density increases, there is a significant drop in the efficiency of the OLED device (so-called "roll-off" behavior). The effects of triplet-triplet annihilation and self-quenching are similarly unfavorable (see, for example, H. Yersin, "Highly Efficient OLEDs with Phosphorescent Materials", Wiley-VCH, Weinheim 2008 and SR Forrest et al., Phys. Rev. B 2008, 77, 235215 ). Thus, in particular drawbacks in the use of such emitters for OLED lighting, where a high luminance, z. B. of more than 1000 cd / m ^{2 is} required. (Compare: J. Kido et al. Jap. J. Appl. Phys. 2007, 46, L10. In addition, molecules in electronically excited states tend to be more chemically reactive than molecules in ground states, thus increasing the likelihood of unwanted chemical reactions with the length of emission lifetime. Such undesirable chemical reactions will then reduce device lifetime. Another significant disadvantage is that with long emission lifetimes and the associated small radiative emission rate, radiationless processes usually predominate. As a result, the emission quantum yields become undesirably low.

In addition, the emitter materials usually each have fixed emission colors. Thus, special requirements for emission colors can not be met in many cases. Of particular technological importance is z. B. the realization of white-light emitters. For these, a very broad color spectrum superimposed from different primary colors has to be generated. Also in this area there is a deficit in the materials available so far.

It is an object of this invention to tailor the emission colors of particular emitters.

Brief description of the invention

In a first aspect, the invention relates to a method of shifting the emission wavelength of a metal complex emitting at a given wavelength to wavelengths that are larger as the given wavelength. In other words, the invention relates to a method for increasing the Stokes shift of an emitting metal complex.

The Stokes shift of an emitting metal complex is the wavelength difference between the lowest energy absorption (lowest energy absorption peak) and the main emission maximum (emission peak). The Stokes shift, for example, refers to the absorption from the singlet ground state to the lowest excited singlet state, as well as the emission from that excited singlet state to the singlet ground state.

In the process, at least one metal complex is used which has the following properties: It has a given geometry in the area of the metal center in the electronic ground state and, in the electronically excited state, it aims at a changed geometry. The change in geometry depends on the environment of the emitting complex, in particular on a surrounding polymeric matrix.

According to the invention, the method comprises the step of embedding the metal complex in a polymeric matrix. The polymeric matrix must be such that the geometry change of the embedded metal complex is possible as soon as it is electronically excited. The electronic excitation can be done for example by an optical light excitation or in an OLED by means of a hole-electron recombination, The nature of the geometry change is explained below.

In a second aspect, the invention relates to a composition which comprises a) at least one emitting metal complex having a geometry in the region of the metal center in the electronic ground state, which changes by electronic excitation and b) has a polymeric matrix. The metal complex is embedded in the polymeric matrix in such a way that the given geometry of the metal complex is changed by an electronic excitation (such as optical light absorption or hole-electron recombination).

In preferred embodiments of the invention, the following applies to both the method described in the beginning and the composition:
In a preferred embodiment of the invention, the metal complex used has a ΔE (S ₁ -T ₁ ) value between the lowest excited singlet (S ₁ ) and the underlying triplet (T ₁ ) state of less than 2500 cm ^-1 , preferably less than 1500 cm ^-1 , more preferably less than 1000 cm ^-1 , most preferably less than 500 cm ^-1 .

The emitting metal complex with a given geometry in the region of the metal center in the electronic ground state can be selected from the group consisting of mononuclear metal complexes and binuclear metal complexes. In preferred embodiments of the invention, the metal complex is a copper, gold or silver complex. Preferably, the mononuclear metal complex is a complex of Formula I and the binuclear metal complex is a complex of Formula II, shown below.

In the method, the change of the given geometry by the electronic excitation is, in particular, the change of a tetrahedral coordination in the direction of a square-planar coordination, which corresponds to a change with a Planarisierungstendenz.

The electronically excited metal complex used in the process and present in the composition preferably has an emission lifetime of at most 20 μs, preferably of at most 10 μs. It is further preferred that the electronically excited, geometrically hardly distorted metal complex, ie z. B. embedded in relatively rigid crystalline form, an emission quantum yield of the solid of greater than 30%, preferably greater than 50%, more preferably greater than 70%.

By the method, the Stokes shift can be increased by embedding the metal complex in the polymeric matrix by 10 nm, 50 nm, 100 nm, or 150 nm, so that a composition comprising a metal complex emitter can be provided having a correspondingly variable Stokes shift.

Likewise, by means of the method, the emission spectrum of the metal complex can be broadened by embedding in the polymeric matrix, in particular by 10 nm to 100 nm.

As the polymeric matrix, an amorphous, soft polymer (eg, polysiloxanes, polyethylene oxides), a medium-rigidity (eg, PMMA = polymethylmethacrylate, polycarbonates) or a very rigid polymer (e.g. Polyphenylene oxides) can be used. The rigidity can be greatly increased by using crosslinkable polymers, wherein the crosslinking can be triggered by thermal or UV activation. The appropriate degree of "hardness" or "softness" of the polymeric Martrix can also be changed by annealing, for example.

By the method, a change in the emission color of the metal complex can be achieved, with a change to white light is possible. In particular, a large Stokes shift with a strong broadening is advantageous for this purpose.

The composition results in an emitter with altered color emission compared to the metal complex as a solid. Particularly preferred are compositions in which the embedded metal complex emits white light.

In a third aspect, the invention relates to opto-electronic devices comprising a composition of the type described herein.

In particular in OLEDs, the composition according to the invention in the region of the emission layer is given by the ratio of the mass of the metal complex to the mass of the matrix material of between 1% by weight to 99% by weight. Preference is given to 2% by weight to 20% by weight.

In a fourth aspect, the invention relates to the use of a method of the type described herein or a composition of the type described herein in an opto-electronic device.

The term opto-electronic device used here refers to organic light emitting diodes (OLEDs), light emitting electrochemical cells (LEECs or LECs), OLED sensors, in particular non-hermetically shielded gas and vapor sensors, organic solar cells (OSCs), organic Field effect transistors, organic lasers, organic diodes, organic photodiodes and "down conversion" systems.

• – relativ kurze Emissionslebensdauer von nur wenigen μs,
• – hohe Emissionsquantenausbeuten von größer 30%,
• – Veränderbarkeit der Emissionsfarben,
• – Veränderbarkeit der Breite der Emissionsbanden.

Accordingly, the invention relates to the provision and provision of compositions and their use, the compositions in particular having the following properties:

• Relatively short emission life of only a few μs,
• High emission quantum yields of greater than 30%,
• - changeability of emission colors,
• - Changeability of the breadth of the emission bands.

Detailed description of the invention

Singlet Harvesting

It is of particular importance to relax the strong transitional ban from the excited triplet state T ₁ to the singlet state So and to develop emitter molecules with the shortest possible emission lifetime but nevertheless a high emission quantum yield. OLEDs using such emitters then show a significantly lower roll-off efficiency and allow a longer life of the opto-electronic device.

Surprisingly, the problem described above can be solved by the present invention by using emitter molecules that have specific electronic structures or singlet-triplet energy distances and that exhibit the singlet harvesting effect. In 2a For example, an energy level scheme for transition metal complexes with little or little impact spin-orbit coupling (eg, metal complexes of the first and second period of the transition metals or metal complexes with largely ligand-centered triplet states, including the third period) is schematic shown. Based on this scheme, the photo-physical electroluminescence properties of these molecules will be explained. The hole-electron recombination, as is done for example in an opto-electronic device or an opto-electronic device, leads to a statistical average of 25% for the occupation of the singlet state (1 singlet path) and 75% for the occupation of ΔE ₁ (S ₁ -T ₁ ) deeper triplet state (3 triplet paths). The excitation that enters the S ₁ state relaxes to the T ₁ state due to the inter-system crossing (ISC) process, which is usually faster for transition-metal-organic complexes than for 10 ^-12 s. The radiative emission lifetime of the triplet state is very long for these metal complexes (eg 50 μs to 1000 μs or longer). Emitters with such long decay times are hardly suitable for OLED applications.

The disadvantage of the prior art described above can be avoided by choosing metal complexes having a ΔE ₂ (S ₁ -T ₁ ) value between the lowest excited singlet (S ₁ ) and the underlying triplet (T ₁ ). Condition of less than 2500 cm ^-1 have. That's through the in 2 B illustrated energy level diagram for illustrated. This energy difference is small enough to permit a thermal reoccupation of the S ₁ state from the T ₁ state according to a Boltzmann distribution or according to the thermal energy k _B T. This can be a thermally activated light emission from the S ₁ state. This process takes place according to equation (1) Int (S ₁ → S ₀ ) / Int (T ₁ → S ₀ ) = k (S ₁ ) / k (T ₁ ) exp (-ΔE (S ₁ -T ₁ ) / k _B T) (1)

Here, Int (S ₁ -S ₀ ) / Int (T ₁ -S ₀ ) represents the intensity ratio of the emission from the S ₁ state and the T ₁ state, k _B is the Boltzmann constant, and T is the absolute temperature , k (S ₁ ) / k (T ₁ ) is the rate ratio of the (radiative) transition processes into the electronic ground state S ₀ . For example, for Cu (I) complexes, this ratio is between 10 ² to 10 ⁴ . Particularly preferred according to the invention are molecules with a rate ratio of 10 ³ to 10 ⁵ . ΔE (S ₁ - T ₁ ) represents the energy difference ΔE ₂ (S ₁ - T ₁ ) according to 2 B ,

The described process of thermal reoccupation opens an emission channel via the singlet state S ₁ from the occupied triplet. Since the transition from the S ₁ to the S ₀ state is strongly allowed, the triplet excitation energy is recovered almost completely as light emission via the singlet state. This effect is the more pronounced the smaller the energy difference ΔE (S ₁ -T ₁ ). Therefore, preference is given to Cu (I) complexes (and also Ag (I) and Au (I) complexes) which have a ΔE (S ₁ -T ₁ ) value between the lowest excited singlet and the underlying triplet State of less than 1500 cm ^-1 , preferably of less than 1000 cm ^-1 and more preferably of less than 500 cm ^-1 .

Based on a numerical example, this effect will be explained. For a typical energy difference of ΔE (S ₁ -T ₁ ) = 800 cm ^-1 , an intensity ratio according to equation (1) results for room temperature applications (T = 300 K) with k _B T = 210 cm ^-1 and a rate ratio of 10 ^3. This means that the singlet emission process dominates very strongly for a molecule with these example values.

The emission lifetime of this example molecule also changes significantly. The thermal reoccupation results in a mean lifetime τ _av . This can be described approximately according to equation (2) τ _av ≈ τ (S ₁ ) · exp (ΔE (S ₁ -T ₁ ) / k _B T) (2)

Herein, τ (S ₁ ) is the fluorescence lifetime without reoccupation, and τ _{av is} the emission lifetime determined by the two states T ₁ and S ₁ when the reoccurrence channel is opened (see FIG 2 B ). The other sizes have been defined above.

Equation (2) should again be explained by a numerical example. For the assumed energy difference of ΔE (S ₁ - T ₁ ) = 800 cm ^-1 and a decay time of the fluorescent S ₁ state of 50 ns results in an emission decay time (of the two states) of τ _av 2 μs. This cooldown is shorter than most of the very good Ir (III) or Pt (II) triplet emitters known in the art.

In summary, therefore, using this singlet harvesting method for complexes, in particular according to Formulas I and II below, ideally almost all, i. H. capture a maximum of 100% of the excitons and convert it into light via a singlet emission. In addition, it is possible to shorten the emission decay time drastically below the value of the pure triplet emission of these complexes, which is generally a few hundred μs to ms. Therefore, the inventive use of corresponding complexes for opto-electronic components - such as OLEDs - particularly suitable.

Complexes with the above-described properties, ie inter alia with a small singlet-triplet energy difference .DELTA.E (S ₁ - T ₁₎ are preferred to describe in the below general formulas I and II. The electronic transitions, which control the optical behavior of these complexes, show a pronounced metal-to-ligand charge-transfer character. With this transition type is a relatively small value of connected to the expert known quantum mechanical exchange integral. This then results in the desired small energy difference ΔE (S ₁ -T ₁ ).

In a further aspect, the invention relates to a method for the selection of complexes whose ΔE (S ₁ -T ₁ ) value between the lowest excited singlet (S ₁ ) and the underlying triplet state (T ₁ ) is less than 2500 cm ^-1 , preferably less than 1500 cm ^-1 , more preferably less than 1000 cm ^-1 , most preferably less than 500 cm ^-1 .

The determination of the ΔE (S ₁ -T ₁ ) value can be carried out both by quantum mechanical calculations by means of the computer programs known in the prior art (for example by means of turbomole programs using TDDFT and CC2 calculations) or as explained below - be carried out experimentally.

The energy difference ΔE (S ₁ -T ₁ ), in particular the complexes described by the formulas I and II, can be described approximately quantum mechanically by the so-called exchange integral multiplied by the factor 2. Its value depends directly on the expressiveness of the so-called charge-transfer character involving the metal d orbitals and the ligand π * orbitals. That is, an electronic transition between the different orbitals represents a metal to ligand charge transfer (CT) transition. The smaller the overlap of the molecular orbitals described above, the more pronounced is the electronic charge transfer character. This is then associated with a decrease in the exchange integral and thus a decrease in the energy difference ΔE (S ₁ -T ₁ ). Because of these photophysical (quantum mechanical) properties, the energy differences according to the invention can be achieved with ΔE (S ₁ -T ₁ ) of less than 2500 cm ^-1 or less than 1500 cm ^-1 or less than 1000 cm ^-1 or even less than 500 cm ^-1 .

The determination of AE (S ₁ - T ₁₎ value can be made experimentally as follows: For a given complex, the energy difference .DELTA.E leaves (S ₁ - T ₁₎ using the above equation (1) simply determine. A transformation results in: In {Int (S ₁ → S ₀ ) / Int (T ₁ → S ₀ )} = In {k (S ₁ ) / k (T ₁ )} - (ΔE (S ₁ -T ₁ ) / kB) (1 / T) (3)

For the measurement of the intensities Int (S ₁ → S ₀ ) and Int (T ₁ → S ₀ ), any commercially available spectrophotometer can be used. A graphical plot of the (logarithmic) intensity ratios In {Int (S ₁ → S ₀ ) / Int (T ₁ → S ₀ )} measured at different temperatures against the inverse of the absolute temperature T generally yields a straight line. The measurement is carried out in a temperature range from room temperature (300 K) to 77 K or to 4.2 K, wherein the temperature is adjusted by means of a cryostat. The intensities are determined from the (corrected) spectra, where Int (S ₁ → S ₀ ) and Int (T ₁ → S ₀ ) represent the integrated fluorescence or phosphorescence band intensities which are determined by means of the programs belonging to the spectrophotometer to let. The respective transitions (band intensities) can be easily identified since the triplet band is at lower energy than the singlet band and gains in intensity with decreasing temperature. The measurements are carried out in oxygen-free dilute solutions (about 10 ^-2 mol L ^-1 ) or on thin films of the corresponding molecules or on films doped with the corresponding molecules. If a solution is used as the sample, it is advisable to use a solvent or solvent mixture which forms glasses at low temperatures, such as 2-methyltetrahydrofuran, butyronitrile, toluene, ethanol or aliphatic hydrocarbons. If a film is used as a sample, the use of a matrix having a significantly higher singlet and triplet energy than that of the metal complexes (emitter molecules) according to the formulas I or II, z. B. PMMA (polymethylmethacrylate). This film can be applied from solution.

The line slope is -ΔE (S ₁ -T ₁ ) / k _B. With k _B = 1.380 10 ^-23 JK ^-1 = 0.695 cm ^-1 K ^-1 , the energy gap can be determined directly.

A simple, approximate estimate of the ΔE (S ₁ -T ₁ ) value can also be made by reading the fluorescence and phosphorescence spectra at low temperature (eg 77 K or 4.2 K using a cryostat) be registered. The ΔE (S ₁ -T ₁ ) value then corresponds approximately to the energy difference between the high-energy rising edges of the fluorescence or phosphorescence band.

Another method of determining the ΔE (S ₁ -T ₁ ) value is by measuring the emission decay times with a commercial meter. Here, the emission lifetime τ _av as a function of temperature with the help of a cryostat for the range between 4.2 K or z. B. 20 K and 300 K measured. By using the formula (4) and the emission lifetime for the triplet state τ (T ₁ ) measured at low temperature, it is possible to fit the measured values with the formula (4), and the ΔE (S ₁ -T ₁ ) is obtained. -Value. (Note: The τ (T ₁ ) value is often determined by the plateau obtained when the measured values are plotted, and if such a plateau is formed, cooling to 4.2 K is generally no longer necessary).

The more pronounced the CT character of an organic molecule, the more the electronic transition energies change as a function of solvent polarity. For example, a pronounced polarity dependence of the emission energies indicates that there are small ΔE (S ₁ - T ₁ ) values.

Flexibilization of the molecular structure and the immediate environment

The four-coordinate complexes according to formulas I and II have an approximately tetrahedral coordination in the region of the metal center in the electronic ground state. Upon optical excitation or excitation by hole-electron recombination into an electronic state with pronounced metal-to-ligand charge-transfer character and the associated formal oxidation of the metal atom, there are significant changes in the geometry of the complex in the direction of a square Planar coordination, ie towards a "planarization" of the molecule based on a metal center of the formulas I and / or on both metal centers of the formula II. By this process, the energies of the emitting states are lowered. Due to the geometry change of the excited state compared to the ground state, an increase in the Stokes shift results between absorption and emission. As a result, the emission is shifted to longer wavelengths (eg, blue to green or to yellow or to red) and the spectral widths of the emission bands are increased (eg, 10 to 100 nm). In the event that the emission covers both the spectral blue, green and red range, a white-light emission can also be generated. Examples of color changes are in 3 shown and illustrated in Tables 1 to 6.

Another aspect of the invention is that the geometry change that occurs through the excitation process can be controlled. That is, a vanishingly small geometry change leads to a likewise small shift of the emission colors and comparatively small broadening of the emission bands, so that the emission behavior of the metal complex can correspond approximately to that of the very rigid solid or the behavior in frozen solutions. For medium geometry changes, the z. For example, as a result of steric hindrances, color shifts and broadening of the emission bands by a few tens of nanometers are obtained, while in very "soft" environments of the emitter molecules (eg, even in fluid solutions) very large changes in geometry and hence large color shifts (e.g. 200 nm) as well as band broadening (eg up to 100 nm) (see also in 1 shown example.)

The control of the possible by the electronic excitation saliency of the geometry change in the process for increasing the Stokes shift can be done according to the invention by two strategies, namely by an intra-molecular substitution and / or by changing the rigidity of the polymeric matrix into which Embedded metal complex:

Intra-molecular substitution

By varying the steric demand of the ligands or their substituents R or their size (compare formulas I and II), the molecularly possible twists can be influenced within wide limits, but also largely suppressed. The extent of the possible distortions can be determined on the one hand by quantum mechanical calculations using the computer programs known in the prior art (eg by means of turbomole or Gaussian programs with execution of DFT or TDDFT directions). On the other hand, the determination of the emission band shift and broadening can also be done experimentally. For this purpose, the emission behavior of the complex in solid and then tested in solution. The comparison of the emission spectra then leads directly to the desired statement about the severity of the emission band change.

Change in the rigidity of the matrix

High rigidity is present when using the crystalline solid (eg as a 100% emitter material, such as in an OLED). The examples given show ( 3 , Table 1) that on this basis a blue light emission is easily achievable.

In many applications, the emitter molecules are doped in polymer matrices, for example in concentrations of 2 to 20 percent by weight. Such dopants are used, for example, in emission layers for efficient OLEDs. In the case of a doping, the individual environment of an emitter molecule is decisive for whether the maximum possible change in geometry predetermined by the chemical structure of the complex can actually take place. In principle, this individual environment in a given matrix is not identical for each emitter molecule. That is, the distribution of installation situations is very inhomogeneous. In other words, there will be emitter complexes in relatively small or rigid mounting gap, but also (other) complexes will find a relatively large space. This eventually leads to a range of geometry modification possibilities. As a result, as desired, areas of color shifts and hence emission band broadening will result.

The center of gravity of a color shift and the width of the associated emission band is given by the polymeric matrix used. Thus, the most different size distributions of the gaps in the matrices and the most diverse rigidities can be achieved by a variation and / or pretreatment of the polymers. For example, as known in the art, amorphous, soft polymers (eg, polysiloxanes, polyethylene oxides) or mid-rigid (eg, polymethylmethacrylates (PMMA), polycarbonates), but also very rigid polymers (e.g. Polyphenylene oxides) can be used. The rigidity can also be greatly increased by using crosslinkable polymers, wherein the crosslinking is triggered by thermal or UV activation.

An example of the dependence on the polymer pretreatment is given. PMMA is a semi-crystalline polymer in small areas. By annealing (raising the temperature to about 70 ° C to 90 ° C and then cooling), the crystalline areas grow and the matrix material becomes more rigid. This has an effect on the color shift occurring in relation to the dye emission. This can be reduced by annealing by several nm alone.

In general, the rigidity of a polymer matrix can be described by the glass transition temperature T _g . The lower this is, the more flexible the matrix and thus also the immediate environment of the doped chromophore / emitter. T _g values can be found in the literature. (See, for example, Wolfgang Kaiser, "Polymer Chemistry for Engineers", Carl Hanser Verlag, Munich 2006 and Z. B. Hans-Georg Elias "Macromolecules, Volume 2: Physical Structures and Properties", 6th ed., Wiley-VCH, Weinheim 2001, p. 452 ff. )

In addition, as noted above, polymer matrices are characterized by voids between the (very large) polymer molecules. The sizes and distributions of these free spaces vary with the type of polymer, the pretreatment and the temperature difference relative to _Tg . Statements about these properties are important for many technological areas (eg rates of drug release). As a result, extensive investigations and classifications have been carried out for more than five decades (eg H. Fujita, Adv. Polym. Sci. 1961, 3, 1 ; D. Ehlich, H. Sillescu, Macromolecules 1990, 23, 1600 ; MT Cicerone, FR Blackburn, MD Ediger, Macromolecules 1995, 28, 8224 ). The expressiveness (frequency and size) of the free spaces can be z. B. with measurably accessible diffusion coefficients of small molecules in the polymer matrix correlate (see, for example: D. Ehlich, H. Sillescu, Macromolecules 1990, 23, 1600 ; MT Cicerone, FR Blackburn, MD Ediger, Macromolecules 1995, 28, 8224 ). Polymer matrices having a desired micro-range flexibility of the doped emitter molecules may be named accordingly.

Metal complexes suitable for color shift (emitter molecules)

mit
M = Cu, Ag oder Au
L – Lⁱⁱⁱ: geeignete Liganden, die weiter unten definiert werden. Die Liganden können entweder gleich oder verschieden sein. Die Liganden können entweder einzähnige Liganden sein oder miteinander verbunden sein und mehrzähnige, insbesondere zweizähnige, Liganden bilden. Die Formeln I und II enthalten entweder vier einzähnige Liganden oder zwei zweizähnige Liganden oder einen zweizähnigen und zwei einzähnige Liganden.Formula I and II

With
M = Cu, Ag or Au
L - L ⁱⁱⁱ : suitable ligands, which are defined below. The ligands can be either the same or different. The ligands can either be monodentate ligands or be interconnected and form polydentate, especially bidentate, ligands. Formulas I and II contain either four monodentate ligands or two bidentate ligands or one bidentate and two monodentate ligands.

There are in particular mono- and bidentate phosphine and Arsanliganden and ligands having at least one N-donor atom use. The ligands can be either neutral or simply negatively charged.

X in formula II is a suitable bridge, such as. B. the anions Cl ^- , Br ^- , I ^- , SCN ^- , CN ^- , RS ^- , RSe ^- , R ₂ N ^- , R ₂ P ^- , RC≡C ^- ,
in which
R = alkyl (e.g., Me, Et, n-Pr, i-Pr, n-Bu, t-Bu, adamantyl), aryl (e.g., phenyl, tolyl, naphthyl, C ₆ F ₅ ), heteroaryl (eg, furyl, thienyl, pyridyl, pyrimidyl), alkenyl (eg CR = CR''R '''), alkynyl (-C≡C-R'), -OR ', -NR'₂; R ', R'',R''' are defined as R and can also be H.

The alkyl, aryl, alkenyl and alkynyl radicals may also be deuterated, halogenated or substituted in some other way (eg with other alkyl, aryl, alkenyl and alkynyl functions).

The bridge can also be:

Depending on the charge of the ligand, the complexes may have the following charges: -1, 0, and +1. The charge is compensated by a suitable counterion.

As cations can be used: metal cations, in particular alkali metals, NH ₄ ⁺ , NR ₄ ⁺ , PH ₄ ⁺ , PR ₄ ⁺ ,
with R = alkyl (eg Me, Et, n-Pr, i-Pr, n-Bu, t-Bu, adamantyl), aryl (eg phenyl, tolyl, naphthyl, C ₆ F ₅ ), Heteroaryl (eg furyl, thienyl, pyridyl, pyrimidyl), alkenyl (eg CR = CR''R '''), alkynyl (-C≡C-R'), -OR ', -NR' ₂ .

As anions may be used: halides, PF ₆ -, BF ₄ -, AsF ₆ -, SbF ₆ -, ClO ₄ -, NO ₃ -, BR ₄ -,
with R = alkyl (eg Me, Et, n-Pr, i-Pr, n-Bu, t-Bu, adamantyl), aryl (eg phenyl, tolyl, naphthyl, C ₆ F ₅ ), Heteroaryl (eg furyl, thienyl, pyridyl, pyrimidyl), alkenyl (eg CR = CR''R '''), alkynyl (-C≡C-R'), -OR ', -NR' ₂ . R ', R''andR''' are defined as R and can also be H.

Definition of Ligands (L to L ⁱⁱⁱ in Formulas I and II)

Neutral monodentate phosphine ligands

R ₃ P with the same or different R = alkyl (eg Me, Et, Pr, i-Pr, n-Bu, t-Bu, adamantyl), aryl (eg phenyl, tolyl, naphthyl, C ₆ F ₅ ), heteroaryl (eg furyl, thienyl, pyridyl, pyrimidyl), alkenyl (eg CR = CR''R '''), alkynyl (-C≡C-R'), -OR ' , -NR ' ₂ .

R ', R'',R''' are defined as R and also H.

The alkyl, aryl, alkenyl and alkynyl radicals may also be deuterated, halogenated or substituted in some other way (eg with other alkyl, aryl, alkenyl and alkynyl functions).

Neutral bidentate phosphine ligands

The ligands shown below are bound via the phosphorus atoms to the metal ion of the metal complex. R is an organic radical, in particular R = alkyl (for example Me, Et, n-Pr, i-Pr, n-Bu, t-Bu, adamantyl), aryl (for example phenyl, tolyl, naphthyl, C ₆ F ₅ ), heteroaryl (eg furyl, thienyl, pyridyl, pyrimidyl), alkenyl (eg CR = CR''R '''), alkynyl (-C≡C-R'), OR ', -NR' ₂ . R ', R''andR''' are defined as R and also H.

The R's in the structures may be the same or different.

Charged phosphine ligands

The charged phosphine ligands may be, for example, the compounds shown below. The radical R is an organic substituent and, like the radical R, defines the neutral monodentate phosphine ligands. The R's in the structures may be the same or different. One or both of the phosphorus atoms may be oxidized to a phosphine oxide (R ₂ R'P = O).

The following examples are intended to illustrate the above general ligand formulas:

In all structures of the phosphane ligands shown, the phosphorus can be replaced by an arsenic atom.

Neutral, monodentate N-donor ligands

wobei Z1–Z5 = N oder CR(X)
mit R(X) = organischer Rest.Neutral monodentate N-donor ligands are either nitriles RC≡N or imines, especially heterocyclic imines of the following form:

where Z1-Z5 = N or CR (X)
with R (X) = organic radical.

These organic groups R (X) and R, R 1, R ₂ and R 3 can be identical or independent and can be selected from the group comprising: hydrogen, halogen and groups which are represented by oxygen - (- OR), nitrogen - (- NR ₂ ) or silicon atoms (-SiR ₃ ), as well as alkyl, aryl, heteroaryl and alkenyl groups or substituted alkyl, aryl, heteroaryl and alkenyl groups having substituents such as halogens or deuterium, alkyl groups and others in general known donor and acceptor groups such as tertiary amines, carboxylates and their esters, and CF ₃ groups. The organic groups can also lead to annellated ring systems.
X = running digit.

Neutral, bidentate N-donor ligands

Particular preference is given to α-diimine ligands which advantageously have the following structure:

α-Diimine ligands, as used herein, can consist of both five- or six-membered rings whose components Z1-Z4 are either the fragments CR (X) or N.

With R (X) = organic radical. These organic groups R (X) and also R 1, R 2 and R 3 can be identical or independent of one another and can be selected from the group comprising: hydrogen, halogen and groups which are bonded via oxygen - (- OR) , Nitrogen - (- NR ₂ ) or silicon atoms (-SiR ₃ ) are bonded, and alkyl, aryl, heteroaryl and alkenyl groups or substituted alkyl, aryl, heteroaryl and alkenyl groups having substituents such as halogens or deuterium, alkyl groups and other well known donor and acceptor groups such as tertiary amines, carboxylates and their esters, and CF ₃ groups. The organic groups can also lead to annellated ring systems.
X = running number,
Y can be either NR, O or S.

This definition also includes the possibility that A or B do not form a cycle but are open-chain. ("#" Denotes the atom attached to the second unit. "*" Denotes the atom that undergoes complex binding). The units A and B can also be connected by an additional bridge so that a new aromatic or aliphatic cycle is formed.

The above formulaic representation of α-diimine ligands is illustrated by the following examples.

R (X) and R1-R10 are each organic groups R which may be the same or different. These organic groups can be selected from the group comprising: hydrogen, halogen and groups which are bonded via oxygen - (- OR), nitrogen atoms (-NR ₂ ) or silicon (-SiR ₃ ), and also alkyl, aryl, heteroaryl and alkenyl groups or substituted alkyl, aryl, heteroaryl and alkenyl groups having substituents such as halogens or deuterium, alkyl groups and other well-known donor and acceptor groups, such as tertiary amines, carboxylates and their esters, and CF ₃ groups. The organic groups can also lead to annellated ring systems.

It is crucial that the substituents directly adjacent to the coordinating N atoms (ie R1 and R8) are sterically less demanding groups, so that sufficient flexibility of the metal complexes remains. In particular, substituents which consist of only one atom (eg H, Cl, Br, I) and methyl and ethyl groups are sterically less demanding. larger Substituents lead to an excessive stiffening of the complexes and greatly reduce the molecular flexibility or even prevent the corresponding effect. Particularly preferred are substituents whose space requirement or size does not significantly exceed that of a methyl group.

Simply negatively charged, bidentate N-donor ligands

- Anionic ligands N-B-N

wobei Z1–Z3 = N oder CR(X),
mit R(X) = organischer Rest. Diese organischen Gruppen R(X) können identisch oder voneinander unabhängig sein und ausgewählt werden aus der Gruppe enthaltend: Wasserstoff, Halogen und Gruppen, die über Sauerstoff-(-OR), Stickstoff-(-NR₂) oder Siliziumatome(-SiR₃) gebunden sind, sowie Alkyl-, Aryl-, Heteroaryl- und Alkenyl-Gruppen bzw. substituierte Alkyl-, Aryl-, Heteroaryl- und Alkenyl-Gruppen mit Substituenten wie Halogenen oder Deuterium, Alkylgruppen und weitere allgemein bekannte Donor- und Akzeptor-Gruppen, wie beispielsweise tertiäre Amine, Carboxylate und deren Ester, und CF₃-Gruppen. Die organischen Gruppen können auch zu annellierten Ringsystemen führen.
X = laufende Ziffer
Y = O, S oder NR.

where Z1-Z3 = N or CR (X),
with R (X) = organic radical. These organic groups R (X) can be identical or independent and are selected from the group comprising: hydrogen, halogen and groups which are represented by oxygen - (- OR), nitrogen - (- NR ₂ ) or silicon atoms (-SiR ₃ ) are bonded, and alkyl, aryl, heteroaryl and alkenyl groups or substituted alkyl, aryl, heteroaryl and alkenyl groups having substituents such as halogens or deuterium, alkyl groups and others well known donor and acceptor groups such as tertiary amines, carboxylates and their esters, and CF ₃ groups. The organic groups can also lead to annellated ring systems.
X = running digit
Y = O, S or NR.

The bridge B denotes the fragment R ' ₂ B, z. H ₂ B, Ph ₂ B, Me ₂ B, (R ₂ N) ₂ B, etc. (where Ph = phenyl, Me = methyl);
"*" Indicates the atom that forms the complex bond.
"#" Denotes the atom connected to the second unit via B.

These ligands will be referred to hereinafter as NBN. The single negatively charged N-donor ligand may be one of the molecules shown below:

- Anionic ligands N-B'-N and NN

wobei
Z1–Z4 = N oder das Fragment CR(X),
mit R(X) = organischer Rest. Diese organischen Gruppen R(X) sowie R, R1 und R2 können identisch oder voneinander unabhängig sein und ausgewählt werden aus der Gruppe enthaltend: Wasserstoff, Halogen und Gruppen, die über Sauerstoff-(-OR), Stickstoff-(-NR₂) oder Siliziumatome(-SiR₃) gebunden sind, sowie Alkyl-, Aryl-, Heteroaryl- und Alkenyl-Gruppen bzw. substituierte Alkyl-, Aryl-, Heteroaryl- und Alkenyl-Gruppen mit Substituenten wie Halogenen oder Deuterium, Alkylgruppen und weitere allgemein bekannte Donor- und Akzeptor-Gruppen, wie beispielsweise tertiäre Amine, Carboxylate und deren Ester, und CF₃-Gruppen. Die organischen Gruppen können auch zu annellierten Ringsystemen führen.
X laufende Ziffer,
Y entweder O, S oder NR ist.

in which
Z1-Z4 = N or the fragment CR (X),
with R (X) = organic radical. These organic groups R (X) and R, R 1 and R 2 can be identical or independent of one another and can be selected from the group comprising: hydrogen, halogen and groups which are bonded via oxygen (- OR) , Nitrogen - (- NR ₂ ) or silicon atoms (-SiR ₃ ) are bonded, and alkyl, aryl, heteroaryl and alkenyl groups or substituted alkyl, aryl, heteroaryl and alkenyl groups having substituents such as halogens or deuterium, alkyl groups and other well known donor and acceptor groups such as tertiary amines, carboxylates and their esters, and CF ₃ groups. The organic groups can also lead to annellated ring systems.
X running number,
Y is either O, S or NR.

The bridge B 'is a neutral bridge, such as -CH ₂ -, -CR ₂ -, -SiR ₂ -, -NH-, -NR-, -O-, or -S; (R is again generally an organic group and defined as described above for the neutral monodentate phosphane ligands.)
"*" Indicates the atom that forms the complex bond;
"#" Denotes the atom that is linked via B or directly to the second unit.

Nitrogen ligands containing the bridge B 'are abbreviated as N-B'-N, and those not containing the bridge as NN.

The following examples illustrate this ligand type:

characters

1 : Basic structure of an OLED. The illustration is not drawn to scale.

2 : To explain the electroluminescence behavior. a transition metal complexes with small or only relatively small impacting spin-orbit coupling and comparatively large energy difference ΔE ₁ (S ₁ -T ₁ ), ie, for example, greater than 3000 cm ^-1 , between the lowest excited triplet state and the overlying singlet state. The value given for τ (T ₁ ) represents an example. b Diagram for explaining the electroluminescence behavior of metal complexes with comparatively small energy difference ΔE ₂ (S ₁ -T ₁ ), ie, for example, less than 2500 cm ^-1 , between the lowest stimulated triplet state and the singlet state lying above it. An example of b is in 3 presented. τ ₁ (ISC) and τ ₂ (ISC) represent the inter-system crossing times.

The 3 shows the absorption spectrum and emission spectra of Cu (POP) (pz ₂ BH ₂ ).

Examples

Examples of the formula I.

Example A Cu (POP) (pz ₂ BH ₂ )

The 3 shows absorption and emission spectra of Cu (POP) (pz ₂ BH ₂ ). These were taken at room temperature. Embedded in a polymeric matrix (shown in the figure) results in a strong color shift of the emission.

Absorption and emission in CH ₂ Cl ₂ : c = 5 × 10 ^-5 mol / L. Emission in PMMA: c ≈ 0.5% by weight. Emission of powder with c = 100%. Table 1. Emission data of Cu (POP) (pz ₂ BH ₂ ) in different matrices Powder ^a PMMA ^a CH ₂ Cl ₂ ^b Emission maximum λ _max [nm] 436 462 535 Emission lifetime τ [μs] 20 22 1.3 Quantum yield φ _PL [%] 45 35 CIE color coordinates 0.15; 0.11 0.17; 0.21 0.35; 0.47 ^a Measured under N ₂ atmosphere. ^b Measured after final degassing. ^c The color coordinates are usually used to describe the visual color impression (eg see T. Smith, J. Guild; Trans. Opt. Soc. 1931/1932, 33, 73 ).

Tabelle 2. Emissionsdaten von Cu(POP)(pz₂Bph₂) im Feststoff und in CH₂Cl₂ Pulver^a CH₂Cl₂ ^b Emissionsmaximum λ_max[nm] 468 498 Emissionslebensdauer τ[μs] 13 1,8 Quantenausbeute ϕ_PL[%] 90 ≈ 10 CIE Farbkoordinate^c 0,16; 0,22 0,25; 0,39 ^a Unter N₂ Atmosphäre gemessen. ^b Nach Endgasunggemessen. ^c Die Farbkoordinaten werden in der Regel zur Beschreibung des visuellen Farbeindrucks verwendet (z. B.: T. Smith, J. Guild; Trans. Opt. Soc. 1931/1932, 33, 73 ).From investigations of the temperature dependence of the emission lifetime, the following values for the powder can be determined using formula (4): ΔE (S ₁ -T ₁ ) = 1300 cm ^-1 ; τ (S ₁ ) = 30 ns; τ (T ₁ ) = 600 μs, τ _av = 20 μs. These data prove the occurrence of the singlet harvesting effect for Cu (POP) (pz ₂ BH ₂ ). Example B Cu (POP) (pz ₂ Bph ₂ )

Table 2. Emission data of Cu (POP) (pz ₂ Bph ₂ ) in the solid state and in CH ₂ Cl ₂ Powder ^a CH ₂ Cl ₂ ^b Emission maximum λ _max [nm] 468 498 Emission lifetime τ [μs] 13 1.8 Quantum yield φ _PL [%] 90 ≈ 10 CIE color coordinate ^c 0.16; 0.22 0.25; 0.39 ^a Measured under N ₂ atmosphere. ^b Measured after degassing. ^c The color coordinates are usually used to describe the visual color impression (eg: T. Smith, J. Guild; Trans. Opt. Soc. 1931/1932, 33, 73 ).

Tabelle 3. Emissionsdaten von Cu(POP)(pz₄B) in verschiedenen Matrizen Pulver^a PMMA^a CH₂Cl₂ ^b Emissionsmaximum λ_max[nm] 451 457 500 Emissionslebensdauer τ[μs] 22 24 0,5 Quantenausbeute ϕ_PL[%] 90 30 2 CIE Farbkoordinaten^c 0.14; 0.11 0,17; 0,18 0,26; 0,38 ^a Unter N₂ Atmosphäre gemessen. ^b Nach Endgasung gemessen. ^c Die Farbkoordinaten werden in der Regel zur Beschreibung des visuellen Farbeindruckes verendet (z. B. siehe T. Smith, J. Guild; Trans. Opt. Soc. 1931/1932, 33, 73 ).Emission life was also measured at T = 77K. The value for the powder is 475 μs. At a value of φ _PL = 90% at T = 300 K, it can be concluded that the singlet harvesting is present due to the very large increase in the lifetime due to cooling. Example C Cu (POP) (pz ₄ B)

Table 3. Emission data of Cu (POP) (pz ₄ B) in different matrices Powder ^a PMMA ^a CH ₂ Cl ₂ ^b Emission maximum λ _max [nm] 451 457 500 Emission lifetime τ [μs] 22 24 0.5 Quantum yield φ _PL [%] 90 30 2 CIE color coordinates ^c 0:14; 12:11 0.17; 0.18 0.26; 0.38 ^a Measured under N ₂ atmosphere. ^b Measured after final degassing. ^c The color coordinates are usually used to describe the visual color impression (eg see T. Smith, J. Guild; Trans. Opt. Soc. 1931/1932, 33, 73 ).

Emission life was also measured at T = 77K. The values are 450 μs (powder) and 680 μs (complex in PMMA). Due to the very strong increase in the lifetime by cooling can be concluded that the presence of singlet harvesting.

The compounds [Au (dppb) ₂ ] BF ₄ (λ _max = 490 nm, φ _PL = 90%) and [Ag (dppb) ₂ ] NO ₃ (λ _max = 445 nm) are known to exhibit blue powder emissions. The emission shifts z. For example, for [Ag (dppb) ₂ ] NO ₃ in methanol at λ _max = 680 nm. With a correspondingly wide color shift range, white light generation is also possible when the molecules are incorporated into polymer matrices.

Examples of the formula II

Tabelle 4. Emissionsdaten von Cu₂Br₂(PPh₃)₂(py)₂ im Feststoff und in PMMA Pulver^a PMMA^a Emissionsmaximum λ_max[nm] 485 517 Emissionslebensdauer τ[μs] 19 12 Quantenausbeute ϕ_PL[%] 70 10 a Unter N₂ Atmosphäre gemessen.Example D Cu ₂ Br ₂ (PPh ₃ ) ₂ (py) ₂

Table 4. Emission data of Cu ₂ Br ₂ (PPh ₃ ) ₂ (py) ₂ in solid and in PMMA Powder ^a PMMA ^a Emission maximum λ _max [nm] 485 517 Emission lifetime τ [μs] 19 12 Quantum yield φ _PL [%] 70 10 a Measured under N ₂ atmosphere.

Tabelle 5. Emissionsdaten von Cu₂Br₂(PPh₃)₂(4-MeO-py)₂ in verschiedenen Matrizen Pulver^a PMMA^a Emissionsmaximum λ_max[nm] 450 490 Emissionslebensdauer τ[μs] 7 6 Quantenausbeute ϕ_PL[%] 30 ^a Unter N₂ Atmosphäre gemessen. Beispiel F Cu₂Br₂(PPh3)₂(4-tBu-py)₂

Tabelle 6. Emissionsdaten von Cu₂Br₂(PPh₃)₂(4-tBu-py)₂ in verschiedenen Matrizen Pulver^a PMMA^a Emissionsmaximum λ_max[nm] 465 505 Emissionslebensdauer τ[μs] 17 11 Quantenausbeute ϕ_PL[%] 70 < 10 ^a Unter N₂ Atmosphäre gemessen.The emission lifetime at T = 2 K (measured in powder) is 630 μs. Due to the very strong increase in the lifetime by cooling can be concluded that the presence of singlet harvesting. Example E: Cu ₂ Br ₂ (PPh ₃ ) ₂ (4-MeO-py) ₂

Table 5. Emission data of Cu ₂ Br ₂ (PPh ₃ ) ₂ (4-MeO-py) ₂ in various matrices Powder ^a PMMA ^a Emission maximum λ _max [nm] 450 490 Emission lifetime τ [μs] 7 6 Quantum yield φ _PL [%] 30 ^a Measured under N ₂ atmosphere. Example F Cu ₂ Br ₂ (PPh 3) ₂ (4-t Bu-py) ₂

Table 6. Emission data of Cu ₂ Br ₂ (PPh ₃ ) ₂ (4-tBu-py) ₂ in different matrices Powder ^a PMMA ^a Emission maximum λ _max [nm] 465 505 Emission lifetime τ [μs] 17 11 Quantum yield φ _PL [%] 70 <10 ^a Measured under N ₂ atmosphere.

The emission lifetime at T = 2 K (measured in powder) is 650 μs. Due to the very strong increase in the lifetime by cooling can be concluded that the presence of singlet harvesting.

As shown by the experimental data shown, the metal complexes described herein can also be used as emitters 100%, ie without the presence of a polymeric matrix. They are then present in a microcrystalline structure and can be characterized in particular by high emission quantum yields. Preferably, the emission quantum yield in the solid is at least 45% (eg Cu (POP) (pz ₂ BH ₂ ), preferably at least 70% (eg Cu ₂ Br ₂ (PPh ₃ ) ₂ (py) ₂ ) , more preferably at least 90% (eg, Cu (POP) (pz ₄ B) and Cu (POP) (pz ₂ Bph ₂ )).

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

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Claims (17)

Method for shifting the emission wavelength of a metal complex emitting at a given wavelength to wavelengths greater than the given wavelength, the metal complex - Has a given geometry in the area of the metal center in the electronic ground state, and - strives for a changed geometry in the electronically excited state, comprising the step of embedding the metal complex in a polymeric matrix permitting a change in the given geometry. The method of claim 1, wherein the metal complex has a ΔE (S ₁ -T ₁ ) value between the lowest excited singlet (S ₁ ) and the underlying triplet (T ₁ ) state of less than 2500 cm ^-1 . The method of claim 1 or 2, wherein the metal complex is a mononuclear metal complex of formula I or a dinuclear metal complex of formula II. The method of claim 1 to 3, wherein the change in the given geometry is the alteration of a tetrahedral coordination towards a square-planar coordination. The method of claim 1 to 4, wherein the metal complex in the electronically excited state has an emission lifetime of at most 20 microseconds. The method of claim 1 to 5, wherein the metal complex in the solid has an emission quantum yield of greater than 30%. The method of claim 1 to 6, wherein the shift of the emission wavelength by the embedding is at least 10 nm. The method of claim 1 to 7, wherein the emission spectrum of the metal complex is broadened by embedding in the polymeric matrix by at least 10 nm. The method of claims 1 to 8, wherein the embedded metal complex emits white light. Composition comprising: An emitting metal complex, the - Has a given geometry in the area of the metal center in the electronic ground state, and - In the electronically excited state seeks an altered geometry, and A polymeric matrix, wherein the metal complex is embedded in the polymeric matrix such that the given geometry of the metal complex is altered by electronic excitation. The composition of claim 10, wherein the metal complex has a ΔE (S ₁ -T ₁ ) value between the lowest excited singlet (S ₁ ) and the underlying triplet (T ₁ ) state of less than 2500 cm ^-1 . A composition according to claim 10 or 11, wherein the metal complex is a mononuclear metal complex of formula I or a dinuclear metal complex of formula II. The composition of claim 11, wherein the change in the given geometry is the alteration of a tetrahedral coordination towards a square-planar coordination. The composition of claims 10 to 13, wherein the metal complex in the electronically excited state has an emission lifetime of at most 20 μs. A composition according to claim 10 to 14, wherein the metal complex in the solid has an emission quantum yield of greater than 30%. Opto-electronic device comprising a composition according to claim 10 to 15, wherein the opto-electronic device is selected from the group consisting of organic light emitting diodes (OLEDs), light emitting electrochemical cells (LEECs or LECs), OLED sensors, in particular non-hermetically shielded gas and vapor sensors, organic solar cells (OSCs), organic field effect transistors, organic lasers, organic diodes, organic photodiodes, and down conversion systems. Use of a method according to claim 1 to 9 or a composition according to claim 10 to 15 in an optoelectronic device, wherein the optoelectronic device is selected from the group consisting of organic light emitting diodes (OLEDs), light emitting electrochemical cells (LEECs or LECs) , OLED sensors, in particular non-hermetically outwardly shielded gas and vapor sensors, organic solar cells (OSCs), organic field effect transistors, organic lasers, organic diodes, organic photodiodes and "down conversion" systems.

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