Light-emitting copper complexes

Abstract

A light-emitting compound comprising a cationic or non-ionic species of formula (I).

Description

DESCRIPTION Title: ELECTROLUMINESCENT COPPER COMPLEXES

[0001] The present invention relates to electroluminescent molecular materials based on copper complexes with spectral emission in the red and near infrared, as well as their use in devices such as solid-state light-emitting devices. State of the art

[0002] Photo- and / or electroactive metal complexes with particular photophysical and redox properties are attractive both from the point of view of fundamental research and technological applications. Their exceptional photophysical and electrochemical characteristics have enabled the fabrication of light-emitting electroluminescent devices and they are currently used commercially in devices of the "organic light-emitting diode" type, abbreviated as "OLED" (OLED meaning "organic light-emitting diode" in English). These materials allow improved performances in terms of efficiency, lifetime and purity of the emission color.

[0003] The triplet nature of the localized excited state on the active materials allows harvesting both singlet and triplet electrogenerated excitons by direct trapping or energy transfer processes in these electroluminescent devices. As a result, the theoretical internal quantum efficiency increases from 25%, which corresponds to purely fluorescent devices, up to 100%. The most widely used, and even commercially available, electroluminescent metal complexes with the highest performance are based on iridium and / or platinum complexes.

[0004] However, there is a strong desire to replace such metals with less rare, less toxic, and easier to extract or even purify. Currently, photoactive copper-based complexes with mononuclear, binuclear, or polynuclear structures have been studied, but their emission (photo- and electroluminescence) is typically in the blue to orange region. Only very rare examples of copper-based compounds emitting in the red and / or near infrared are known.

[0005] In particular, Cu(l)-based emitters are considered an interesting alternative to those containing platinum group metals, which are more rare and more expensive, for the development of (electro-)luminescent materials. Cu(l) complexes known in the literature generally display emission spectra covering the blue-green to orange region, while the design of compounds that emit efficiently in the deep red to The "near infrared", abbreviated as "NIR" (NIR stands for "near infrared" in English) is still very difficult and examples are still very rare, as described in the following articles: a) Hupp, B. et al. Inorg. Chem. 2017, 56, 8996; b) Gernert, M. et al. J. Am. Chem. Soc. 2020, 142, 8897.

[0006] Nevertheless, NIR emitters are very interesting for the fabrication of light-emitting devices for night vision displays, optical telecommunication technology, biomedical devices for phototherapy as well as biological imaging agents, for example. Recently, Costa and colleagues presented deep-red emitting mononuclear heteroleptic Cu(l) complexes [Cu(P A P)(N A N)]PF6 carrying a 4,4'-diethylester-2,2'-biquinoline ligand as N ligand A N, and mono- and diphosphines. The “light-emitting electrochemical cells” designated by the abbreviated formula “LEC” manufactured with these emitters provided electroluminescence with a “peak wavelength” designated by the symbol “ÀEL” having a value ÀEL = 671 nm, (Costa et al. Adv. Optical Mater. 2019, 7, 1900830). However, there is a need to develop Cu(l) complexes that emit well beyond 700 nm, for use as active materials in light-emitting devices.

[0007] The present invention aims to overcome the aforementioned drawbacks and to enable the preparation of complexes having improved NIR electroluminescence properties for copper complexes with a maximum electroluminescence wavelength greater than 700 nm when used as emitters in light-emitting devices such as OLED and LEC. Description of the invention

[0008] The present invention relates to an electroluminescent compound comprising a cationic or non-ionic species of formula (I): - in which the groups Ai and A2 are independently selected from the heteroatoms or functional groups -O-, -S-, -(NH)-, -(PH)-, and a group -(Rs-C-Re)-, Rs and Re being independently selected from at least one -H atom and a linear, cyclized or branched aliphatic chain; said aliphatic chain comprising at least one function chosen from an alkane, an alkene, an alkyne and an aromatic or heteroaromatic nucleus, said aliphatic chain possibly comprising at least one heteroatom selected from O, S, N and P, and said aliphatic chain possibly being substituted by at least one alcohol, ether, thiol, thioether, cyano, amine, amide, carboxylic acid, ester, thioester, carbamate, acrylate, carbonate, halogen, and phosphine function; - in which the groups E1, E2, Z and G are independently selected from the atoms or functional groups =N-, =P- and [-C=]'; - in which the J1- and J2- groups are integrated into an aromatic nucleus while being independently chosen from: > a heteroatom or functional group O-, -S-, -(NH)-, -(PH)-; and > a group -QI=Q2-, Q1 and Q2 being independently selected from the atoms -C=; =N-, =P-, and the at least one atom of -C= carrying a substituent R7 which being independently selected from at least one atom -H and a linear, cyclized or branched aliphatic chain; said aliphatic chain comprising at least one function chosen from an alkane, an alkene, an alkyne and an aromatic or heteroaromatic nucleus, said aliphatic chain possibly comprising at least one heteroatom selected from O, S, N and P, and said aliphatic chain possibly being substituted by at least one alcohol, ether, thiol, thioether, cyano, amine, amide, carboxylic acid, ester, thioester, carbamate function, acrylate, carbonate, halogen, and phosphine; - in which the groups Rs, R9, R10 and Ru are independently selected from at least one -H atom and a linear, cyclized or branched aliphatic chain; said aliphatic chain comprising at least one function chosen from an alkane, an alkene, an alkyne and an aromatic or heteroaromatic nucleus, said aliphatic chain possibly comprising at least one heteroatom selected from O, S, N and P, and said aliphatic chain possibly being substituted by at least one alcohol, ether, thiol, thioether, cyano, amine, amide, carboxylic acid, ester, thioester, carbamate, acrylate, carbonate, halogen, and phosphine function; - m being an integer chosen from 0 to 1, for m = 0 the group Ri is a bidendentate ligand, comprising at least two heteroatoms independently selected from O, S, N and P and linked to the copper atom, preferably Ri is a diphosphine; for m = 1 the groups Ri and R2 are monodentate ligands independently selected from a halogen, a ligand comprising at least one nitrogen atom capable of linking to the copper atom and preferably an amine, a phosphine, an alkyne, a carbene preferably selected from N-heterocyclic carbenes (NHC), and a thiocyanate; - m' being an integer chosen from 0 to 1, for m' = 0 the group R3 is a bidendentate ligand, comprising at least two heteroatoms independently selected from O, S, N and P and linked to the copper atom, preferably R3 is a diphosphine; for m' = 1 the groups R3 and R4 are monodentate ligands independently selected from a halogen, a ligand comprising at least one nitrogen atom capable of linking to the copper atom and preferably an amine, a phosphine, an alkyne, a carbene preferably selected from N-heterocyclic carbenes (NHC), and a thiocyanate; - n being an integer chosen from 0 to 2; and - at least one R7 group which can advantageously form with at least one of said Rs and Ru groups an aromatic nucleus condensed on the aromatic nucleus integrating J1 or J2.

[0009] For the purposes of the present invention, the term "condensed aromatic nucleus" is equivalent to the term "condensed aromatic cycle" and corresponds to the IUPAC definition, thus designating polycyclic aromatic hydrocarbons (PAHs) as organic compounds consisting of several aromatic cycles, some of the carbon atoms of which are common to two or three cycles.

[0010] Preferably, or according to one embodiment of the present invention, said cationic or non-ionic species is according to formula (II): - in which the groups Ai, A2, E1, E2, Z and G are identical to those defined for formula (I); - in which the L- and M- groups are independently chosen from an atom or functional group =N-, =P- and -HC=; - in which the groups R12 and R-is are independently selected from at least one -H atom and a linear, cyclized or branched aliphatic chain; said aliphatic chain comprising at least one function chosen from an alkane, an alkene, an alkyne and an aromatic or heteroaromatic nucleus, said aliphatic chain possibly comprising at least one heteroatom selected from O, S, N and P, and said aliphatic chain possibly being substituted by at least one alcohol, ether, thiol, thioether, cyano, amine, amide, carboxylic acid, ester, thioester, carbamate, carbonate, halogen, and phosphine function; - m being an integer selected from 0 to 1, for m = 0 the group Ri being as defined for formula (I); for m = 1 the groups Ri and R2 being as defined for formula (I); - m' being an integer selected from 0 to 1, for m' = 0 the group R3 being as defined for formula (I); for m' = 1 the groups R3 and R4 being as defined for formula (I); and -n being an integer chosen from 0 to 2.

[0011] Preferably, Ai and A2 are sulfur atoms, E1 and E2 are nitrogen atoms.

[0012] Preferably, L and M are independently selected from an atom or functional group =N- and -HC=.

[0013] Preferably, the integers m and m' are equal to 0, and the groups R1 and R3 are diphosphines comprising two phosphine functions linked by a carbon group comprising at least two aromatic nuclei.

[0014] Preferably, the groups R12 and R13 are aryls functionalized by at least two tert-butyl groups.

[0015] Preferably, the above-mentioned electroluminescent compound comprises a molecular structure selected from the formulas: and wherein L and M are selected from an atom or functional group =N- and -HC=.

[0016] Preferably, said electroluminescent compound comprises a molecular structure selected from the formulas:

[0017] According to a second embodiment of the present invention, also preferred, said cationic or non-ionic species is according to formula (V): in which: - L and M are independently selected from an atom or functional group =N- and -CH-; preferably L and M are both -CH-; - m being an integer selected from 0 to 1, for m = 0 the group Ri being as defined for formula (I); for m = 1 the groups Ri and R2 being as defined for formula (I); - m' being an integer selected from 0 to 1, for m' = 0 the group R3 being as defined for formula (I); for m' = 1 the groups Rs and R4 being as defined for formula (I); and -n being an integer chosen from 0 to 2; - R 8 and R11 are independently selected from at least one -H atom and a linear, cyclized or branched aliphatic chain; said aliphatic chain comprising at least one function chosen from an alkane, an alkene, an alkyne and an aromatic or heteroaromatic nucleus, said aliphatic chain possibly comprising at least one heteroatom selected from O, S, N and P, and said aliphatic chain possibly being substituted by at least one alcohol, ether, thiol, thioether, cyano, amine, amide, carboxylic acid, ester, thioester, carbamate, carbonate, halogen, and phosphine function, preferably at least Rs or Ru is a linear, cyclized or branched aliphatic chain.

[0018] Preferably, the integers m and m' are equal to 0, and the groups Ri and Rs are diphosphines comprising two phosphine functions linked by a carbon group comprising at least two aromatic nuclei.

[0019] Thus, still according to this second embodiment of the invention, said species is, advantageously, according to the following formula (VI): in which - L and M are independently selected from an atom or functional group =N- and -CH-; preferably L and M are both -CH-; - R 8 and R11 are independently selected from at least one -H atom and a linear, cyclized or branched aliphatic chain; said aliphatic chain comprising at least one function chosen from an alkane, an alkene, an alkyne and an aromatic or heteroaromatic nucleus, said aliphatic chain possibly comprising at least one heteroatom selected from O, S, N and P, and said aliphatic chain possibly being substituted by at least one alcohol, ether, thiol, thioether, cyano, amine, amide, carboxylic acid, ester, thioester, carbamate, carbonate, halogen, and phosphine function, preferably at least Rs or Ru is a linear, cyclized or branched aliphatic chain, for example is an alkyl group comprising 1 to 18 carbon atoms.

[0020] Examples of alkyl groups having 1 to 18 carbon atoms include alkyl groups having 1 to 3 carbon atoms such as methyl, ethyl, n-propyl, i-propyl, alkyl groups having 5 to 7 carbon atoms such as n-pentyl, n-hexyl, 2,2 dimethylpropyl, or n-heptyl.

[0021] Advantageously, said electroluminescent compound has the following molecular structure:

[0022] According to a third embodiment of the present invention, also one of the preferred embodiments, said cationic or non-ionic species is according to the formula (SEEN) : in which: - L and M are independently selected from an atom or functional group =N- and -CH-; preferably L and M are both -CH-; - m being an integer selected from 0 to 1, for m = 0 the group Ri being as defined for formula (I); for m = 1 the groups Ri and R2 being as defined for formula (I); - m' being an integer selected from 0 to 1, for m' = 0 the group R3 being as defined for formula (I); for m' = 1 the groups Rs and R4 being as defined for formula (I); and -n being an integer chosen from 0 to 2.

[0023] Preferably, the integers m and m' are equal to 0, and the groups R1 and R3 are diphosphines comprising two phosphine functions linked by a carbon group comprising at least two aromatic nuclei.

[0024] Thus, still according to this third embodiment of the invention, said species is, advantageously, according to the following formula (VIII): in which - L and M are independently selected from an atom or functional group =N- and -CH-; preferably L and M are both -CH-.

[0025] Advantageously, said electroluminescent compound has the following molecular structure:

[0026] The present invention also relates to a photoactive and electroactive material comprising at least one electroluminescent compound as described previously in the context of the present invention. Such a material may advantageously comprise said compound taken as a mixture in the solid state with at least one ingredient selected from another compound, a complex, a polymer, an ionic species and an ionic liquid. Said material may advantageously comprise at least one electroluminescent compound according to the invention solely on its surface, for example integrated into a surface layer of said material.

[0027] In the context of the invention the term “photoactive” means “capable of a chemical or physical change in response to an optical stimulus”.

[0028] In the context of the invention the term "electroactive" means "capable of a chemical or physical change in response to an electrical stimulus".

[0029] The present invention also relates to a solid-state light-emitting device comprising an electroactive layer comprising a photoactive and electroactive material as described in the context of said present invention. Said device may be mono- or multi-layer and said light emission may or may not be circularly polarized.

[0030] The present invention also relates to a use of a photoactive and electroactive material as described in the context of the present invention, implemented in the realization of one of the following applications: - in an optoelectronic device chosen between an organic light-emitting diode of the OLED type and a cell of the LEC type (light-emitting electrochemical cells); - to carry out photocatalysis reactions, preferably photopolymerization; - to perform medical imaging; and - for object detection by marking, such as counterfeiting and night vision. Brief description of the figures

[0031] [Fig. 1] Figure 1 shows the UV-visible absorption and photoluminescence spectra of the Ilia complex (triangles) and IVa (open squares) measured in dichloromethane at room temperature under excitation at a wavelength of 480 nm.

[0032] [Fig. 2] Figure 2 shows the UV-visible absorption and photoluminescence spectra of the Ilia complex (open circles) and IVa (squares) measured in the solid state at room temperature under excitation at a wavelength of 480 nm.

[0033] [Fig. 3] Figure 3 shows the UV-visible absorption and photoluminescence spectra of the IIIb complex (open triangles) and IVb (rhombus) measured in dichloromethane at room temperature under excitation at a wavelength of 500 nm.

[0034] [Fig. 4] Figure 4 shows the UV-visible absorption and photoluminescence spectra of the IIIb complex (circles) and IVb (empty rhombuses) measured in the solid state at room temperature under excitation at a wavelength of 480 nm.

[0035] [Fig. 5] Figure 5 shows the UV-visible absorption and photoluminescence spectra of the Via (circles) and Villa (open triangles) complex measured in dichloromethane at room temperature under excitation at a wavelength of 480 nm.

[0036] [Fig. 6] Figure 6 shows the UV-visible absorption and photoluminescence spectra of the Via (circles) and Villa (open triangles) complex measured in the solid state at room temperature under excitation at a wavelength of 480 nm.

[0037] [Fig. 7] Figure 7 shows the normalized electroluminescence spectra measured for LEC devices using the Ilia compound as emitter having an electroactive layer of 84 (curve b), 151 (curve c), and 289 (curve d) nm thickness under an electric potential difference of 4, 5, and 6 V, respectively. The photoluminescence spectrum is also shown (curve a) for comparison.

[0038] [Fig. 8] Figure 8 shows the normalized electroluminescence spectra measured for LEC devices using compound IVa as emitter having an electroactive layer of 73 (curve b), 160 (curve c), and 278 (curve d) nm thickness under an electric potential difference of 4, 5, and 6 V, respectively. The photoluminescence spectrum is also shown (curve a) for comparison.

[0039] Other advantages, aims and particular characteristics of the present invention will emerge from the examples which follow, given for explanatory and in no way limiting purposes. Experimental Part

[0040] Protocol and experimental conditions

[0041] Photophysical measurements

[0042] Steady-state emission spectra were recorded on a Horiba Jobin-Yvon IBH FL-322 Fluorolog 3 spectrometer equipped with a 450 W xenon arc lamp, dual grating excitation and emission monochromators (2.1 nm mm -1 dispersion; 1200 mm grooves -1) and a Peltier-cooled red-sensitive Hamamatsu R13456 PMT detector. The emission and excitation spectra were corrected for source intensity (lamp and grating) and emission spectral response (detector and grating) by standard correction curves. Time-resolved measurements were performed using either the Time-Correlated Single-Photon Counting (TCSPC) or Multi-Channel Scaling (MCS) electronics option of the TimeHarp 260 board installed on a PicoQuant FluoTime 300 fluorometer (PicoQuant GmbH, Germany), equipped with a PDL 820 laser pulse driver. A pulsed laser diode LDH-PC-375 (= 375 nm) or LDH-PC-440B (= 440 nm) with a pulse width at half-maximum < 50 ps, ​​a repetition rate of 200 kHz-40 MHz was used to excite the sample and mounted directly on the sample chamber at 90°. Photons were collected by a PMA Hybrid-07 single-photon counting detector. Data were acquired using the commercial software EasyTau II (PicoQuant GmbH, Germany), while data analysis was performed using the integrated software FluoFit (PicoQuant GmbH, Germany). For solution samples, luminescence quantum yields were measured in optically dilute solutions (optical density <0.1 at the excitation wavelength).Absolute photoluminescence quantum yields (PLQYs) for both solution and solid-state samples were measured on a Hamamatsu Quantaurus-QY C11347-11 integrating sphere under equilibrium conditions in air using an empty quartz tube as a reference when exciting at a wavelength between 400 and 500 nm. All solvents were of spectrophotometric grade. Samples were prepared by the freeze-pump-thaw technique using a homemade quartz cuvette equipped with a Rotaflo stopcock.

[0043] For time-resolved measurements, data fitting was performed using maximum likelihood estimation (MLE) methods and goodness of fit was assessed by inspection of the reduced function % 2and weighted residuals. For multi-exponential decays, it was assumed that the intensity, namely l(t), was decreasing as was the sum of the individual exponential decays (Eq. 2):

[0044] where TÎ is the decay time and ai is the amplitude of the component at t = 0. In the tables, the percentages of the pre-exponential factors, ai, are given after normalization.

[0045] Fabrication and characterization of LEC devices

[0046] For device fabrication, standard cleaning and UV / ozone treatment were performed on the indium tin oxide (ITO) coated glass substrates. After cleaning, the substrates were spin-coated with a layer of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) (40 nm) at 3500 rpm and were then baked at 150 °C for 30 minutes in ambient air. The mixture of complex (Ilia or IVa) (80 wt%) and 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM + (PFe)'] (20 wt%) in acetonitrile solution was spun onto the PEDOT:PSS layer. The ionic liquid [BMIM + (PFe)'] was added to provide additional mobile ions to accelerate the device response. Different solution concentrations (40, 60 and 80 mg mL' 1) were used to deposit different emissive layer thicknesses to optimize device performance. Spin-coating of all emissive layers was performed at 2000 rpm in ambient air. The emissive layer thicknesses were measured by ellipsometry (see Table 1 and 2). After deposition of the emissive layers, the samples were baked at 60°C for 8 hours in a vacuum oven to remove residual solvent. Finally, a silver top contact was deposited by thermal evaporation in a vacuum chamber (approximately 10 -6torr). The electroluminescence (EL) properties of these light-emitting electrochemical cell (LEC) devices were measured using source measurement units (B2901A, Keysight) and a calibrated Si photodiode. The EL spectra of these LECs were acquired with a calibrated fiber optic spectrometer (USB2000+, Ocean Optics). All LEC devices were measured under constant bias voltages. Device measurements were performed in a nitrogen glove box to reduce the device degradation rate.

[0047] Synthetic route

[0048] 5-Bromopicolinaldehyde, (3,5-di-tert-butylphenyl)boronic acid, dithiooxamide, oxy-di-2,1-phenylene)bis(diphenylphosphine) (DPEPhos), and 9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphine) (Xantphos) are commercially available and were used as received. Commonly available solvents and other reagents were purchased and used without further purification. 2-(5-bromopyridin-2-yl)-1,3-benzothiazole was synthesized as reported in the literature (E.S. Barskaya et al. Russ. Chem. Bull. Int. Ed. 2015, 8, 1975-1977). Silica gel for column chromatography was purchased from Sigma-Aldrich. NMR spectra 1 H, 13 C{ 1 H} and 31 P{ 1H} were recorded at 298 K on a Bruker AV500 spectrometer in deuterated solvents and the residual solvent peak was used as an internal reference. All chemical shifts (5) are reported in ppm. High-resolution electrospray mass spectrometry (HR-ESI-MS) was carried out by the Mass Spectrometry Service of the Chemistry Federation "Le Bel" FR2010 of the University of Strasbourg.

[0049] Comparative examples:

[0050] Synthesis of 2-(5-(3-(tert-ôuty / )-5-isopropylphenyl)pyridin-2- yl)benzo[d]thiazole (3):

[0051] A mixture of 2-(5-bromopyridin-2-yl)-1,3-benzothiazole (1) (0.5 g, 1.7 mmol), Na2COs (0.55 g, 4.7 mmol), and (3,5-di-tert-butylphenyl)boronic acid (2) (0.52 g, 2.2 mmol) in 28 mL of 1,4-dioxane / H2O (3:1 v / v) was degassed by regular bubbling with argon for 20 minutes. Pd(PPh3)4 (0.02 g, 0.018 mmol) was added, and the mixture was refluxed for 7 hours under argon. After cooling, the mixture was extracted with CH2Cl2 (3x40 mL). The combined organic layers were washed with brine, dried over MgSC and evaporated in vacuo. The residue was purified by silica gel column chromatography with petroleum ether / CH2Cl2 ranging from 100:0 to 50:50 as eluent to provide the target compound 3 as a white solid (0.6 g, 87% yield).

[0052] NMR 1H (CDCI3, 500 MHz) 5 : 8.97 (d, 1 H, J = 5 Hz), 8.47 (d, J = 10 Hz, 1 H), 8.15 (d, 1 H, J = 10 Hz), 8.07 (dd, J = 5 Hz, J = 10 Hz, 1 H), 7.97 (d, 1 H, J = 10 Hz), 7.56-7.44 (m, 5H), 1.43 (s, 18H). MRI 13 C (CDCI3, 125 MHz) 5 : 169.3, 154.3, 151.8, 149.7, 148.3, 139.4, 136.5, 136.1, 135.4, 126.3, 125.6, 123.5, 122.8, 122.0, 121.6, 120.6, 35.1, 31.5. HR-MS (ESI) : m / z [M + H] + calculated for C26H29N2S [M + H] + 401 .2046, found 401 .2047.

[0053] Synthèse du [Cu(DPEPhos)(2)]PF6 (Ml) : [Cu(DPEPhos)(3)]PF6(M1) [Cu(xanthophos)(3)]PF6(M2)

[0054] Under a stream of argon, [Cu(CHsCN)4]PF6 (104 mg, 0.28 mmol) was added to a stirred 15 mL solution of DCM containing DPEPhos (150 mg, 0.28 mmol) at room temperature. After 5 minutes, compound 3 (0.111 mg, 0.277 mmol) was added and the mixture was stirred for 4 hours at room temperature. The orange mixture was almost completely evaporated to dryness under reduced pressure and diethyl ether was added to give an orange powder. The complex was obtained by filtration, washed with diethyl ether and dried (0.175 g, 63% yield).

[0055] NMR 1 H (CDCIs, 500 MHz) 5: 8.48 (s, 1 H), 8.24 (d, J = 5 Hz, 2H), 7.98 (d, J = 10 Hz, 1 H), 7.68 (d, J = 10 Hz, 1 H), 7.55 (t, J = 5 Hz, 1 H), 7.45 (td, J = 5 Hz, J = 10 Hz, 1 H), 7.31 -7.26 (m, 5H), 7.22 (t, J = 10 Hz, 2H), 7.16-7.12 (m, 10H), 7.10-7.00 (m, 12H), 6.92-6.89 (m, 2H), 1.40 (s, 6 p.m.). NMR 13C (CDCI3, 125 MHz) 5: 164.8, 158.3 (t, Jp-c ~ 10 Hz), 152.0, 150.0, 147.8, 146.1, 141.1, 137.1, 134.7, 134.5, 134.2, 133.1 (t, JP-C = 7.5 Hz), 132.7 (t, J P.C = 7.5 Hz), 131.4, 132.2, 130.6 (t, J P.C = 17.6 Hz), 130.4, 130.3 (t, JP-C = 17.6 Hz), 130.2, 130.1, 128.8 (dt, J P.C = 5 Hz, J P.C = 15 Hz), 127.5, 127.2, 125.3, 124.7, 123.9 6 (t, J P.C = 15 Hz), 123.6, 122.8, 122.3, 121.4, 120.2, 35.0, 31.4. NMR 31 P (121.5 MHz, CDCI3) 5: -11.5 (wide), -143.9 (sep, 1 I P.F = 708 Hz). HR-MS (ESI): m / z [M + H] + calculated for C62H57CUN2OP2S, [M + H] + 1002.2912, found 1002.2900.

[0056] Synthesis of [Cu(Xantphos)(3)]PFe (M2):

[0057] This compound was prepared by a synthetic procedure similar to that of [Cu(DPEPhos)(3)]PF6 except that Xantphos was used instead of DPEPhos. Color: orange, 0.160 g, yield 60%.

[0058] NMR1 H (CDCI3, 500 MHz) 5 : 8.74 (s, 1 H), 8.28 (s, 2H), 8.02 (d, J = 5 Hz, 1 H), 7.70 (d, J = 5 Hz, 2H), 7.57 (s, 1 H), 7.40-7.30 (m, 3H), 7.30-7.15 (m, 14H), 7.05-7.15 (m, 4H), 6.95-6.87 (m, 1 H), 6.75-6.79 (m, 4H), 6.67-6.60 (m, 3H), 1.99, (s, 3H), 1.64 (s, 3H), 1.39 (s, 18H). RMN 13 C (CDCIs , 125 MHz) 5 : 165.2, 155.0 (t, J P.C = 10 Hz), 152.3, 149.9.0, 147.5, 146.0, 141.2, 137.4, 134.9, 134.6, 133.9, 132.9 (t, J P.C = 7.5 Hz), 132.5 (t, J P .c = 7.5 Hz), 131.4 (t, J P.C = 16 Hz), 131.2, 131.0 (t, J P.C = 16 Hz), 130.3, 130.0, 129.0, 128.9, 128.8, 127.4, 127.3, 123.8, 123.2, 121.4, 120.0 (t, J P.C = 16 Hz), 36.2 35.1 , 31.4, 31.1 , 25.8. RMN 31 P (121.5 MHz, CDCI3 ) 5 : -11 ,5 (large), - 143,9 (sep, 1 J P-F = 708 Hz). HR-MS (ESI) : m / z [M + H] + calculé pour C65H61CUN2OP2S, [M + H] + 1042.3225, trouvé 1042.3239. [00591 Examples of synthesis of bimetallic copper complex according to the invention

[0060] Synthesis of 5-(3,5-di-tert-butylphenyl)picolinaldehyde (5):

[0061] A mixture of 5-bromopicolinaldehyde 4 (1.0 g, 5.3 mmol), (3,5-di-tert-butylphenyl)boronic acid 2 (1.51 g, 6.4 mmol), and K2CO3 (1.48 g, 10.7 mmol) in 20 mL of DMF was degassed by regular bubbling with argon for 20 minutes. Pd(PPhs)4 (0.02 g, 0.018 mmol) was added to the mixture, and the mixture was allowed to stir for 24 hours at 90°C under an argon atmosphere. Then, the mixture was evaporated to dryness under reduced pressure and extracted with CH2Cl2 (2x50 mL). The combined organic layers were washed with brine, dried over MgSC, and evaporated in vacuo. The residue was purified by silica gel column chromatography with CH2Cl2 / petroleum ether ranging from 50:50 to 100:0 as eluent to provide the target compound 5 as a white solid (0.6 g, 38% yield).

[0062] NMR 1H (CDCh, 500 MHz) 5: 10.12 (s, 1 H), 8.98 (s, 1 H), 8.02 (s, 2H), 7.53 (d, J = 2 Hz, 1 H), 7.42 (d, J = 2Hz, 2H), 1.37 (s, 18H). NMR 13 C (CDCh, 125 MHz) 5: 193.1, 152.0, 151.2, 148.9, 142.0, 136.0, 135.5, 123.4, 121.9, 121.8, 35.1, 31.5. HR-MS (ESI): m / z [M + H] + calculated for C20H26NO [M + H] + 296.2009, found 296.2000.

[0063] Synthesis of 2,5-bis(5-(3,5-di-tert-butylphenyl)pyridin-2-yl)thiazolo[5,4- djthiazole (6).

[0064] Compound 5 (0.50 g, 1.7 mmol) and dithiooxamide (0.10 g, 0.83 mmol) were dissolved in 15 mL of DMF and the resulting mixture was refluxed overnight under an argon atmosphere. The reaction mixture was cooled to room temperature and the desired compound 6 was obtained as a yellow precipitate after filtration. The solid was washed with MeOH and dried in vacuo (0.35 g, 62% yield). Yellow crystals were obtained by slow evaporation of the CH2Ch / EtOH solution.

[0065] NMR 1 H (CDCh, 500 MHz) 5: 8.89 (d, J = 2 Hz, 2H), 8.29 (d, J = 8.5 Hz, 2H), 8.03 (dd, J = 2 Hz, J = 8.5 Hz, 2H), 7.51 (s, J = 10 Hz, 2H); 7.46 (d, J = 2 Hz, 4H); 1.38 (s, 36H). NMR 13 C (CDCh, 125 MHz) 5: 170.5, 153.4, 151.9, 149.7, 148.3, 139.2, 136.4, 135.6, 122.9, 121.5, 119.8, 35.1, 31.5. HR-MS (ESI): m / z [M + H] + calculated for C42H49N4S2 [M + H] + 673.3393, found 673.3396.

[0066] Synthesis of [Cu2(DPEPhos)2(6)](PF6)2 of formula (Ilia): 6 Illa

[0067] Under a stream of argon, [Cu(CHsCN)4]PF6 (69 mg, 0.18 mmol) was added to a stirred 15 mL solution of DCM containing DPEPhos (100 mg, 0.18 mmol) at room temperature. After 5 min, compound 6 (62 mg, 0.09 mmol) was added and the mixture was stirred for 4 h at room temperature. The red mixture was almost completely evaporated to dryness under reduced pressure and diethyl ether was added to give a red powder. The Ilia complex was obtained by filtration, washed with diethyl ether and dried (obtained 0.19 g, quantitative yield).

[0068] NMR 1 H (CDCIs, 500 MHz) 5: 8.47 (s, 2H), 8.28 (d, J = 8 Hz, 2H), 8.15 (d, J = 8 Hz, 2H), 7.56 (s, 2H), 7.37 (t, J = 8 Hz, 4H), 7.26 (t, J = 8 Hz, 4H), 7.22-6.96 (m, 48H), 6.72-6.78 (m, 4H), 1.37 (s, 36H). NMR 13C (CDCI3, 125 MHz) 5: 167.6, 158.3 (t, JP-C = 6 Hz), 152.2, 150.2, 148.4, 144.9, 142.1, 137.5, 134.6, 134.4, 133.2 (t, J P.C = 7.5 Hz), 132.9 (t, JP-C = 7.5 Hz), 132.5, 130.5, 130.4, 130.2 (d, JP-C = 5.6 Hz), 130.1 (d, JP-C = 5.6 Hz), 125.4, 124.0, 123.9, 123.1, 123.2, 123.1, 122.9, 121.5, 120.7, 35.0, 31.1. NMR 31 P (121.5 MHz, CDCIs) 5: -11.6 (wide), -143.9 (seven, 1 I P.F = 708 Hz). HR-MS (ESI): m / z [M + PFe] + calculated for C114H105CU2F6N4O2P5S2, 2019.4779, found 2019.4734.

[0069] Synthesis of [Cu2(Xantphos)2(6)](RFe)2 of formula (IVa): IVa

[0070] This compound IVa was prepared by a synthetic procedure similar to that of Ilia except that Xantphos was used instead of DPEPhos. Color: red, obtained 0.18 g, quantitative yield.

[0071] NMR 1H (CDCI3, 500 MHz) 5 : 8.58 (s, 2H), 8.33 (d, J = 8 Hz, 2H), 7.87 (d, J = 8 Hz, 4H), 7.67 (d, J = 8 Hz, 2H), 7.55 (s, 2H), 7.22-7.28 (m, 12H), 7.16 (s, 4H), 7.00- 7.07 (m, 24H), 6.80-6.84 (m, 8H), 6.66-6.80 (m, 4H), 1.94, (s, 6H), 1.70 (s, 6H), 1.32 (s, 36H). RMN 13 C (CDCI3 , 125 MHz) 5 : 167.6, 155.0 (t, J P.C = 6 Hz), 152.4, 149.7, 148.1 , 144.4, 142.4, 137.9, 134.5, 134.2, 132.9 (t, J P.C = 7.5 Hz), 132.3 (t, J P.C = 7.5 Hz), 131.3, 130.7, 130.6, 130.4, 130.5, 130.2, 129.1 (d, J P -c = 17.7 Hz), 128.2, 125.6, 124.2, 123.5, 121.5, 121 .5, 119.4, 119.2, 119.1 , 36.2, 34.9, 31.1 , 29.6, 27.0. RMN 31 P (121.5 MHz, CDCI3 ) 5 : -11 ,5 (large), -143,9 (sep, 1 J P.F = 708 Hz) HR-MS (ESI) : m / z [M + PFe] + calculé pour C120H112CU2F6N4O2P5S2, 2099.5405, trouvé 2099.5405.

[0072] Synthèse du composé (8) :

[0073] Compound 8 was prepared by a synthetic procedure similar to that of 5, except that 5-chloropyrazine-2-carbaldehyde 7 was used as the aldehyde (86% yield).

[0074] 1 H NMR (CDCI3, 500 MHz) 5: 10.17 (s, 1 H), 9.18 (d, J = 1 Hz, 1 H), 9.14 (d, j = 1 Hz, 1 H), 7.91 (d, J = 2 Hz, 2H), 7.61 (t, J = 2 Hz, 1 H), 1.38 (s, 6 p.m.). 13C NMR (CDCI3, 125 MHz) 5: 192.3, 157.1, 152.0, 144.8, 143.0, 142.2, 134.7, 125.6, 122.1, 35.1, 31.5. HR-MS (ESI): m / z [M + H] + calcd for C 19 H 25 N2O, [M + H] + 297.1961, found 297.1954.

[0075] Synthesis of compound (9):

[0076] Compound 9 was prepared by a similar synthetic procedure as compound 6, except for the use of aldehyde 8 instead of 5 (86% yield).

[0077] NMR 1H (CDCIs, 500 MHz) 5: 9.48 (s, 2 H); 9.02 (s, 2 H); 7.90 (d, J = 2 Hz, 4 H); 7.59 (t, J = 2 Hz, 2 H); 1.40 (s, 36 H). 13 C NMR (CDCI3, 125 MHz) 5: 168.8, 154.6, 153.9, 151.9, 144.4, 141.5, 140.7, 135.2, 124.9, 121.5, 35.1, 31.5. HR-MS (ESI): m / z [M + H] + calculated for C40H47N6S2, [M + H] + 675.3298, found 675.3290.

[0078] Synthesis of the compound [Cu2(DPEPhos)2(9)](PF6)2 of formula (lllb): 9 Hlb

[0079] Under a stream of argon, [Cu(CHsCN)4]PF6 (69 mg, 0.18 mmol) was added to a stirred 15 mL solution of DCM containing DPEPhos (100 mg, 0.18 mmol) at room temperature. After 5 min, compound 9 (63 mg, 0.09 mmol) was added and the mixture was stirred for 4 h at room temperature. The red mixture was almost evaporated to dryness under reduced pressure and diethyl ether was added, to give the target compound Hlb as a red powder. The complex was obtained by filtration, washed with diethyl ether and dried (obtained 0.19 g, quantitative yield).

[0080] 1 H NMR (CD2CI2, 400 MHz) 5: 9.25 (s, 2H), 8.35 (s, 2H), 7.58 (t, J = 2 Hz, 2H), 7.48 (s, 4H), 7.26-7.32 (m, 8H), 7. 22 (t, J = 7.5 Hz, 8H), 7.18-7.04 (m, 12H), 6.94- 7.04 (m, 14H), 6.80-6.90 (m, 8H), 6.68-6.76 (m, 4H), 1.32 (s, 36H). 13C NMR (CDCI3, 125 MHz) 5: 158.0, 151.8, 134.5, 133.7, 132.4, 132.0, 131.2, 130.1, 129.6, 129.4, 128.8, 125.6.121.7, 120.3, 35.1, 31.4. NMR 31 P (121.5 MHz, CDCI3) 5: -11.6 (wide)), -143.9 (sep, 1 JP-F = 708 Hz).

[0081] Synthesis of the compound [Cu2(xantphos)2(9)](RFe)2 of formula (IVb): 9 IVb

[0082] Compound (IVb) was prepared by a similar synthetic procedure as (IIIb), except for the use of Xantphos instead of DPEPhos. The target compound was obtained as a red powder (0.18 g, quantitative yield).

[0083] 1 H NMR (CD2CI2, 400 MHz) 5: 8.77 (s, 2H), 8.58 (s, 2H), 7.77 (d, J = 7.5 Hz, 4H), 7.58-7.55 (m, 6H), 7.24-7. 20 (m, 12H), 7.16 (s, 4H), 6.90-7.30 (m, 24H), 6.80- 6.84 (m, 8H), 6.70-6.90 (m, 12H), 1.34 (s, 12H), 1.27 (s, 36H). 13C NMR (CDCI3, 125 MHz) 5: 154.8, 152.2, 132.3, 132.1, 132.0, 131.5, 129.5, 129.4, 129.1, 125.5, 121.7, 118.9, 36.1, 35.1, 31.4, 26.9. NMR 31 P (121.5 MHz, CDCI3) 5: -11.5 (wide)), -143.9 (sep, 1 JP-F = 708 Hz).

[0084] Synthesis of the compound 2,5-bis(6-methylpyridin-2-yl)thiazolo[5,4-d]thiazole (11): 10 11

[0085] Under an argon atmosphere, 6-methylpyridine-2-carboxaldehyde (10) (2 g, 16.5 mmol) and dithiooxamide (1 g, 8.26 mmol) were dissolved in 15 mL of DMF and the resulting mixture was refluxed overnight. The reaction mixture was cooled to room temperature and the desired compound 11 was obtained as a yellow precipitate after filtration. This sol ide was washed with MeOH and dried in vacuo (1.4 g, 52% yield).

[0086] NMR 1 H (CDCI3, 500 MHz) 8: 8.07 (d, J = 10 Hz, 2H), 7.74 (t, J = 10 Hz, 2H), 7.24 (d, J = 10 Hz, 2H), 2.67 (s, 6H). NMR13 C (CDCI3, 125 MHz) 8: 170.9, 158.8, 153.2, 150.6, 137.2, 124.7, 117.1, 24.3. SM-HR (ESI): m / z [M + H] + calculated for C16H12N4S2 [M + H] + 325.0503, found 325.0576.

[0087] Synthesis of the compound [Cu2(DPEPhos)2(11)](PF6)2 of formula (Via): via Under an argon atmosphere, to a stirred 15 mL solution of DCM containing [CU(CHSCN4]PF6 (0.27 g, 0.74 mmol) at room temperature was added DPEPhos (0.4 g, 0.74 mmol). After 15 min, compound 11 (0.12 g, 0.37 mmol) was added to the solution and the mixture was stirred for 4 h at room temperature. The red colored mixture was almost evaporated to dryness under reduced pressure and diethyl ether was added, this allowed the formation of a red precipitate. The target complex (Via) was obtained by filtration, washed with diethyl ether, and then dried (0.67 g, quantitative yield). NMR 1H (CD2CI2, 500 MHz) 5 : 8.07 (t, J = 7.8 Hz, 2H), 7.77 (d, J = 7.8 Hz, 2H), 7.36- 7.40 (m, 10H), 7.26 (t, J = 7.1, 1.2, 8). 7.13 (t, J = 7.8 Hz, 4H), 7.08 (t, J = 7.8 Hz, 4H), 7.00 (t, J = 7.8 Hz, 8H), 6.85-6.91 (m, 12H), 2.54 (s, 6H). NMR 13 C (CD2CI2, 125 MHz) 5 : 170.6 (t, J P.C = 5 Hz), 161.3, 159.8 (t, J P.C = 5 Hz), 151.8, 148.3, 141.9, 136.1 , 135.4 (t, J P.C = 7.5 Hz), 134.5 (t, J P.C = 7.5 Hz), 132.6 (t, J P.C = 17.5 Hz), 132.6, 131.8 (t, J P.C = 17.5 Hz), 131.9, 130.9 (t, J P.C = 7.5 Hz), 130.6 (t, J P.C = 7.5 Hz), 129.9, 127.3, 125.5 (t, J P.C = 17.5 Hz), 123.2, 122.7, 28.0. NMR 31 P (121.5 MHz, CDCI3) 5 : −11 .6 (large), −143.9 (sep, 1 J P.F = 708 Hz). SM-HR (ESI): m / z [M+PFe] + calculated by C88H68CU2F6N4O2P5S2, 1671.1962, found

[0088] Synthesis of the compound 2,5-di(quinolin-2-yl)thiazolo[5,4-d]thiazole (13): This compound (13) was prepared as a yellow powder (60% yield) following the same procedure for the synthesis of 2,5-bis(6-methylpyridin-2-yl)thiazolo[5,4- d]thiazole (11). The NMR data of the prepared compound 13 correspond to those described in the reference. [RC Knighton, et al. Tetrahedron Lett., 2010, 51, 5419- 5422.]

[0089] Synthesis of the compound [Cu2(DPEPhos)2(13)](PF6)2 of formula (Villa): Villa Under argon atmosphere, to a stirred solution of 15 ml of DCM containing [CU(CHSCN4]PF6 (0.2 g, 0.55 mmol) at room temperature was added DPEPhos (0.3 g, 0.55 mmol). After 15 min, compound 13 (0.11 g, 0.27 mmol) was added to the solution and the mixture was stirred for 4 h at room temperature. The red colored mixture was almost evaporated to dryness under reduced pressure and diethyl ether was added, this allowed the formation of a red precipitate. The target complex (Villa) was obtained by filtration, washed with diethyl ether and dried (0.5 g, quantitative yield). NMR 1 H (CD2CI2, 500 MHz) 5: 8.60 (d, J = 10 Hz, 2H), 8.21 (d, J = 10 Hz, 2H), 7.91 (d, J = 10 Hz, 2H), 7.88 (d, J = 10 Hz, 2H), 7.52 (t, J = 10 Hz, 2H), 7.31 -7.35 (m, 6H), 7.14-7.17 (m, 8H), 7.08 (t, J = 10 Hz, 4H), 7.03 (t, J = 10 Hz, 4H), 6.95-6.99 (m, 16H), 6.89-6.93 (m, 20H). NMR 13 C (CD2CI2, 125 MHz) 5: 168.4, 158.3 (t, J P.C= 5 Hz), 150.9, 146.6, 145.8, 140.7, 134.3, 132.9 (t, J P.C = 7.5 Hz), 132.6 (t, J P.C = 7.5 Hz), 132.6, 131.6, 130.6, 130.5, 130.4, 130.2, 130.0, 129.9, 129.8, 129.7, 129.5, 128.9, 128.8, 128.8, 128.7, 128.2, 125.5, 123.4 (t, J P.C = 17.5 Hz), 120.6, 119.6, 65.6. NMR 31 P (121.5 MHz, CDCI3) 5: -11.6 (wide), -143.9 (sep, 1 I P.F = 708 Hz). HR-MS (ESI): m / z [M+PFe] + calculated for C94H68CU2F6N4O2P5S2 1745.2002, found 1745.1977.

[0090] Photophysical analysis:

[0091] The optical properties of these new near-infrared emitting dinuclear complexes, including IIIa-IIIb, IVa-IVb, Via and Villa, were studied in a dilute solution (3x10 -5M) of CH2CI2 at room temperature, both under aerated conditions and after degassing and compared with those of mononuclear derivatives M1-M2. The corresponding photophysical data are listed in Table 1. In Table 2, the photophysical data measured in the solid state for compounds IIIa-IIIb, IVa-IVb, Via and Villa are listed. The absorption and emission spectra of dinuclear compounds IIIa-IIIb and IVa-IVb in dichloromethane solution as well as in the solid state are presented in Figures 1, 2, 3, 4, 5 and 6.

[0092] As for the bimetallic complexes Ilia and IVa, their electronic absorption spectra have quite similar characteristics and they are characterized by three main bands. On the high energy side, an intense band with molar extinction coefficient (s) of £ = 4.1 x 10 4 M -1 cm -1at Δabs = 280 nm is attributable to electronic transitions of intraligand singlet-manifold nature ( 1 IL) involving both arylphosphines and ligand 6. The remarkably intense and narrow band observed at a wavelength of 407 nm (s = 5.8x 10 4 M' 1 cm' 1 for the compound Ilia) can be confidently attributed to processes of IL character 1 attributable to a metal-disturbed TT - TT absorption mainly localized on the scaffold of ligand 6, in agreement with the latter's absorption spectrum. On the lower energy side, the much less intense band (£ = 5.8x 10 4 M' 1 cm' 1 for the compound Ilia) can be attributed to a transition with singlet-type charge transfer from the metal to the ligand (abbreviated 1 MLCT = Metal-to-Ligand Charge Transfer, in English) and charge transfer from one ligand to another ligand (abbreviated 1LLCT = Ligand-to-Ligand Charge Transfer) mixed with the character d(Cu)- *TT(ligand 6) and TT(P-aryl)- *TT(ligand 6), respectively. This band is hypsochromically shifted by about 3690 cm -1 (Àabs = 425 nm, £ = 3.3x 10 3 M' 1 cm -1 ) in the corresponding mononuclear derivative M1, whereas it is absent in the spectra of ligand 6, which confirms this spectral assignment.

[0093] After excitation with a wavelength between 400 and 500 nm, solution samples of both binuclear complexes exhibit broad and featureless NIR photoluminescence at room temperature, with emission maxima (λem) centered at λem = 746 and 732 nm for the Ilia and IVa derivatives, respectively, with a photoluminescence quantum yield (abbreviated PLQY) of 0.13% and 0.06% under degassed conditions. The steady-state emission spectrum appears to be wavelength independent, but it exhibits a slight bathochromic shift under air-equilibration conditions. The excited state decay traces after picosecond pulsed laser excitation show a bi-exponential decay with n = 81.6 (64%) and 12 = 38.9 (36%) ns, for the Ilia derivative, and even shorter lifetimes (T = lifetime) are recorded for the IVa analogues (see Table 3).The deexcitation decays were weakly dependent on the presence of triplet oxygen, as expected for a diffusion-controlled quenching process competing with such a short-lived excited state. The spectrum of the Via derivative shows a hypsochromic shift. Also, the spectrum of the Villa derivative shows an emission peak similar to that observed for compound IVb (see Table 1).

[0094] Conversely, the mononuclear complexes M1 and M2 exhibit shifted emission at a wavelength of 700 nm, due to the much shorter conjugation length TT of the chromophoric ligand, as well as a prolonged excited state and a higher PLQY, i.e., T = 319 ns and 0.5%, respectively, for M1 in the degassed condition.

[0095] Overall, the bi-exponential decay and oxygen dependence observed in the photoluminescence of binuclear compounds indicate the presence of two excited states that are energetically close, but not yet fully equilibrated on the time scale of global radiative processes, with a triplet character that can be tentatively described with a mixed charge transfer character between the metal and the ligand (abbreviated 3 MLCT = Metal-to-Ligand Charge Transfer, in English) as well as between a ligand and another ligand (abbreviated 3 LLCT = Ligand-to-Ligand Charge Transfer, in English).

[0096] For binuclear complexes, a hypsochromic emission shifted by about 1350 cm' 1 as well as the appearance of a clear vibronic progression are observed when lowering the temperature to 77 K in a matrix frozen in CH2CI2 (see Table 1). The observed spacing of about 1350 cm' 1is attributable to intramolecular C=C and C=N vibrational modes, based on related data on organic thiazolo[5,4-d]thiazole emitters (Dyes and Pigments, Pinto MR et al, J Photochem Photobiol A: Chemistry 2001;143:119; Woodward AN et al, J Am Chem Soc 2017;139:8467). This effect is accompanied by an extension of the excited state lifetime that reaches a value as long as T 1 = 356.5 LIS (68%) and T 2 = 123.1 is (32%) for Ilia. Similar results are observed for IVa (see Table 3). Overall, this effect indicates a change in the nature of the emissive excited state that becomes considerably 3 LC in nature and mainly involves the scaffold of the 6 n-conjugated ligand. In contrast, the mononuclear derivatives M1 and M2 retain the broad and featureless emission profile at low temperatures, indicating a character 3 MLCT still important mixed with the component 3LLCT of the emitter excited state.

[0097] Table 1.: Photophysical data recorded for the Ilia—lllb, IVa, IVa-IVb, Via, Villa, and M1-M2 complexes in dilute CH2 Cl2 solution both at room temperature and in a frozen matrix at 77 K. sh denotes a shoulder. table 1] composed [ L n aerated degassed aerated degassed aerated degassed 77 K 43.7 38.9 626, 320.6 279 (41.5) (52%) (36%) (72%) Illa 685, 407 (57.7) 763 746 0.09 0.13 88.4 81.6 752, 81.6 504s / 7, (3.0) (48%) (64%) 840 (sh) (28%) 272 (55.6) 624, 82.8 14.5 15.6 408, (57.7) 683, (29%) 746 732 0.03 0.06 (96%) (86%) 504s / ? (3.3) 753, 322.3 658 8.0 842 (sh) (71%) (4%) (14%) 265 (47.3) 168.4 665, 431 (64%) lllb , (64.8) 790 790 401 966 731 , 530S / 7, (3.6) 56.7 812 (36%) 267, (53.4) 70.1 658, IVb 427, (61.1 ) (43%) 777 791 82 724, 528s / 7 (1.9) 92 183.6 800 (57%) 33.234 35.121 597, 252.9 280 (sh), (39.7) (90%) (87%) 653, (33%) Via 774 765 400, (51.0) 0.13 0.13 169.37 223.49 715, 600.1 (10%) (13%) 791 (67%) 275 (sh), (36.4) 213 620 376, (37.0) (50%) Villa 712 701 680 390 (sh), (30.6) 0.45 0.5 193 106 751 452, (3.8) (50%) 39.7 260s / 7, (25.9) (42%) 284s / 7, (22.2) 398.1 M1 699 699 624 352, (28.8) 0.5 215.3 318.6 (15%) 425s / 7, (3.3) 139.0 (42%) 112.5 261 , (27.8) (44%) 278, (28.7) 32.9 M2 693 695 621 351 , (27.5) 0.6 207.9 273.8 (40%) 425s / 7, (3.2) 311.8

[0098] Table 2. Photophysical data recorded for the Ilia, IVa, lllb - IVb, Via and Villa complexes in the solid state: [Table 2] [00991 Example of devices prepared from the bimetallic complexes according to the invention: LECs based on the complexes of formulas (Ilia) and (IVa):

[0100] LECs employing the Ilia and IVa complexes were fabricated and measured to test their EL properties. The EL characteristics of these LECs are summarized in Table 3. The EL spectra of LECs based on these complexes are shown in Figures 7 and 8, respectively. Both complexes showed a similar thickness-dependent evolution in the EL spectra, despite the fact that the Ilia complex provided a slightly red-shifted EL emission. The LECs The thinnest (approximately 70-80 nm) exhibited dark red EL spectra (maximum emission wavelength >650 nm). With a thicker emissive layer (approximately 150-160 nm), the EL spectra shifted toward the NIR spectral region (maximum emission wavelength >730 nm). A further increase in the emissive layer thickness (approximately 270-280 nm) shifted the EL spectra toward the shorter wavelength spectral region. The thickness-dependent EL spectra of these LECs result from the modified microcavity effect when adjusting the device optical structure (J. -H. Hsu, H.-C. Su, Phys. Chem. Chem. Phys. 2016, 18, 5034.; H.-C. Su, ChemPlusChem 2018, 83, 197; Z. -P. Yang, H.-C. Su,Adv. Funct. Mater. 2020, 30, 1906788.) These data reveal that adjusting the device thickness is essential to achieve greater NIR EL emission from these LECs.To the best of our knowledge, this work demonstrates the first NIR LECs based on copper complexes.

[0101] Table 3: Summary of EL characteristics of LECs based on Ilia, IVa, Via and Villa complex (80% by weight) and [BMIM + (PFe)'] (20% by weight). Table 3] a Concentration of the solution for spin coating. b Maximum stabilized wavelength of EL emission. c Maximum output power of the light. d Maximum external quantum efficiency. e Energy efficiency.

[0102] The bias voltage for each device of different thickness was chosen to achieve the optimized device efficiency. After applying a bias, the mobile ions in the emissive layer of the LEC drifted toward the electrodes and led to the gradual formation of p- and n-type doped layers electrochemically. These doped layers facilitated carrier injection and thus the device current increased with time. The device current decreased rapidly after reaching the maximum value, probably due to the increased resistance of the degraded material. The light output power initially followed the increase in device current. However, the light output power decreased faster than the device current.In addition to material degradation, exciton quenching due to the extension of doped layers toward the emitting region was responsible for the reduction of light output power before the device current decreased (S. van Reenen, RAJ Janssen, M. Kemerink, Adv. Funct. Mater. 2015, 25, 3066). Due to the improved device carrier balance induced by the growth of doped layers, the EQE increased rapidly after applying a bias. After reaching the maximum value, the EQE gradually decreased for the same reasons responsible for the reduction of light output power over time. Among the tested Ilia complex-based LECs, the optimized emissive layer thickness was 151 nm and the peak EQE reached 0.32%. The same strategy was used to optimize complex IVa-based LECs.The IVa complex-based LECs also showed a similar time evolution trend of EL characteristics as the Ilia complex-based LECs. However, the optimized EQE of the IVa complex-based LECs (160 nm) was lower (0.17%). These EL characteristics confirm that the LECs employing the proposed copper complexes can offer NIR EL emission from the device (see Table 3).

Claims

Claims

1. An electroluminescent compound comprising a cationic or non-ionic species of formula (I): - in which the groups Ai and A2 are independently selected from the heteroatoms or functional groups -O-, -S-, -(NH)-, -(PH)-, and a group -(Rs-C-Re)-, Rs and Re being independently selected from at least one -H atom and a linear, cyclized or branched aliphatic chain; said aliphatic chain comprising at least one function chosen from an alkane, an alkene, an alkyne and an aromatic or heteroaromatic nucleus, said aliphatic chain possibly comprising at least one heteroatom selected from O, S, N and P, and said aliphatic chain possibly being substituted by at least one alcohol, ether, thiol, thioether, cyano, amine, amide, carboxylic acid, ester, thioester, carbamate, carbonate, halogen, and phosphine function; - in which the groups E1, E2, Z and G are independently selected from the atoms or functional groups =N-, =P- and [-0=]'; - in which the J1- and J2- groups are integrated into an aromatic nucleus while being independently chosen from: > a heteroatom or functional group -O-, -S-, -(NH)-, -(PH)-; and > a group -QI=Q2-, Q1 and Q2 being independently selected from the atoms -C=; =N-, =P-, and the at least one atom of -C= carrying a substituent R7 which being independently selected from at least one atom -H and a linear, cyclized or branched aliphatic chain; said aliphatic chain comprising at least one function chosen from an alkane, an alkene, an alkyne and an aromatic or heteroaromatic nucleus, said aliphatic chain possibly comprising at least one heteroatom selected from O, S, N and P, and said aliphatic chain possibly being substituted by at least one alcohol, ether, thiol, thioether, cyano, amine, amide, carboxylic acid, ester, thioester, carbamate, carbonate, halogen, and phosphine function; - in which the groups Rs, R9, R10 and Ru are independently selected from at least one -H atom and a linear, cyclized or branched aliphatic chain; said aliphatic chain comprising at least one function chosen from an alkane, an alkene, an alkyne and an aromatic or heteroaromatic nucleus, said aliphatic chain possibly comprising at least one heteroatom selected from O, S, N and P, and said aliphatic chain possibly being substituted by at least one alcohol, ether, thiol, thioether, cyano, amine, amide, carboxylic acid, ester, thioester, carbamate, carbonate, halogen, and phosphine function; - m being an integer chosen from 0 to 1, for m = 0 the group Ri is a bidendentate ligand, comprising at least two heteroatoms independently selected from O, S, N and P and linked to the copper atom, preferably Ri is a diphosphine; for m = 1 the groups Ri and R2 are monodentate ligands independently selected from a halogen, a ligand comprising at least one nitrogen atom capable of linking to the copper atom of and preferably an amine, a phosphine, an alkyne, an N-heterocyclic carbene and a thiocyanate; - m' being an integer chosen from 0 to 1, for m' = 0 the group R3 is a bidendentate ligand, comprising at least two heteroatoms independently selected from O, S, N and P and linked to the copper atom, preferably R3 is a diphosphine; for m' = 1 the groups R3 and R4 are monodentate ligands independently selected from a halogen, a ligand comprising at least one nitrogen atom capable of linking to the copper atom and preferably an amine, a phosphine, an alkyne, an N-heterocyclic carbene and a thiocyanate; - n being an integer chosen from 0 to 2; and - at least one R7 group which can form with at least one of said Rs and Ru groups an aromatic nucleus condensed on the aromatic nucleus integrating Ji or J2.

2. A compound according to claim 1, wherein the cationic or non-ionic species is of formula (II): - in which the groups Ai, A2, E1, E2, Z and G are identical to those defined for formula (I); - in which the L- and M- groups are independently chosen from an atom or functional group =N-, =P- and -HC=; - in which the groups R12 and R-is are independently selected from at least one -H atom and a linear, cyclized or branched aliphatic chain; said aliphatic chain comprising at least one function chosen from an alkane, an alkene, an alkyne and an aromatic or heteroaromatic nucleus, said aliphatic chain possibly comprising at least one heteroatom selected from O, S, N and P, and said aliphatic chain possibly being substituted by at least one alcohol, ether, thiol, thioether, cyano, amine, amide, carboxylic acid, ester, thioester, carbamate, carbonate, halogen, and phosphine function; - m being an integer selected from 0 to 1, for m = 0 the group Ri being as defined for formula (I); for m = 1 the groups Ri and R2 being as defined for formula (I); - m' being an integer selected from 0 to 1, for m' = 0 the group R3 being as defined for formula (I); for m' = 1 the groups R3 and R4 being as defined for formula (I); and - n being an integer chosen from 0 to 2.

3. A compound according to claim 1 or 2, wherein Ai and A2 are sulfur atoms, Ei and E2 are nitrogen atoms.

4. A compound according to any one of claims 1 to 3, wherein L and M are independently selected from an atom or functional group =N- and -HC=.

5. Compound according to one of claims 1 to 4, in which the integers m and m' are equal to 0, and the groups R1 and R3 are diphosphines comprising two phosphine functions linked by a carbon group comprising at least two aromatic nuclei.

6. Compound according to one of claims 2 to 5, in which the groups R12 and R13 are aryls functionalized by at least two tert-butyl groups.

7. A compound according to any one of claims 1 to 6, wherein the electroluminescent compound has a molecular structure selected from the formulae: and wherein L and M are selected from an atom or functional group =N- and -CH-.

8. A compound according to claim 1, wherein the cationic or non-ionic species is of formula (V): in which: - L and M are independently selected from an atom or functional group =N- and - CH-; - m being an integer selected from 0 to 1, for m = 0 the group Ri being as defined for formula (I); for m = 1 the groups Ri and R2 being as defined for formula (I); - m' being an integer selected from 0 to 1, for m' = 0 the group R3 being as defined for formula (I); for m' = 1 the groups Rs and R4 being as defined for formula (I); and -n being an integer chosen from 0 to 2; - R 8 and R11 are independently selected from at least one -H atom and a linear, cyclized or branched aliphatic chain; said aliphatic chain comprising at least one function chosen from an alkane, an alkene, an alkyne and an aromatic or heteroaromatic nucleus, said aliphatic chain possibly comprising at least one heteroatom selected from O, S, N and P, and said aliphatic chain possibly being substituted by at least one alcohol, ether, thiol, thioether, cyano, amine, amide, carboxylic acid, ester, thioester, carbamate, carbonate, halogen, and phosphine function.

9. Compound according to claim 8, in which the integers m and m' are equal to 0, and the groups R1 and R3 are diphosphines comprising two phosphine functions linked by a carbon group comprising at least two aromatic nuclei.

10. A compound according to claim 1, wherein the cationic or non-ionic species is of formula (VII): in which: - L and M are independently selected from an atom or functional group =N- and - CH-; - m being an integer selected from 0 to 1, for m = 0 the group Ri being as defined for formula (I); for m = 1 the groups Ri and R2 being as defined for formula (I); - m' being an integer selected from 0 to 1, for m' = 0 the group R3 being as defined for formula (I); for m' = 1 the groups Rs and R4 being as defined for formula (I); and -n being an integer chosen from 0 to 2.

11. Compound according to claim 10, in which the integers m and m' are equal to 0, and the groups R 1 and R 3 are diphosphines comprising two phosphine functions linked by a carbon group comprising at least two aromatic rings.

12. A compound according to claim 1, wherein the compound has a molecular structure selected from the formulae: (Villa)

13. Photoactive and electroactive material comprising at least one compound according to one of claims 1 to 8.

14. A solid state light emitting device having an electroactive layer comprising a photoactive and electroactive material according to claim 9.

15. Use of a photoactive and electroactive material according to claim 9, implemented in the realization of one of the following applications: - in an optoelectronic device chosen between an organic light-emitting diode of the OLED type and a cell of the LEC type (light-emitting electrochemical cells); - to carry out photocatalysis reactions, preferably photopolymerization; - to perform medical imaging; and - for object detection by marking, such as counterfeiting and night vision.

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