1-lanthanide pyrenates exhibiting luminescent properties, luminescent material based on them, method for producing luminescent material and temperature sensor

Abstract

FIELD: organic chemistry.SUBSTANCE: new coordination compounds, namely complexes of lanthanides with organic ligands. Compound of the general formula Ln(pyr)3 is proposed, where , Ln is at least one La ion or lanthanide other than promethium. Also proposed are a luminescent material based on the above-mentioned compound, which is a powder or suspension of the said compound, a method for producing the luminescent material, and a temperature sensor based on the said luminescent material. The invention provides for the creation of a new lanthanide compound that exhibits luminescence and is suitable for use as a heat-sensitive material.EFFECT: provides the required luminescence intensity and temperature sensitivity of the material in an operating temperature range of up to 300 °C.10 cl, 1 dwg, 3 ex

Description

[0001] Field of technology to which the invention relates

[0002] The group of inventions relates to new coordination compounds, namely to complexes of lanthanides with organic ligands, and can find application in industry and medicine for the production of luminescent compounds, including as a basis for temperature sensors.

[0003] Technology Level

[0004] It is known that coordination compounds of lanthanides with organic ligands exhibit luminescent properties. The energy of the exciting radiation is most efficiently absorbed by the organic ligand, after which the energy is transferred to the lanthanide ion, which luminesces. Due to the high absorption of the ligand, this mechanism allows for achieving high luminescence intensity of coordination compounds compared to inorganic ones (Jean Claude G. Bünzli, “Lanthanide Luminescence: From a Mystery to Rationalization, Understanding, and Applications,” Handbook on the Physics and Chemistry of Rare Earths 50 (2016): 141-76, https: / / doi.org / 10.1016 / bs.hpcre.2016.08.003).

[0005] Fundamental features of lanthanide ion luminescence, such as long excited-state lifetimes, narrow luminescence bands, and the ability of some to emit in the IR range, ensure ease of detection of the luminescence signal. This makes lanthanide coordination compounds extremely interesting for research and potential applications. Ligands of different classes can be used as organic ligands, for example, aromatic carboxylates, beta-diketonates, phenolates, pyrazolonates, Schiff bases (Valentina V. Utochnikova et al., “Lanthanide Pyrazolecarboxylates for OLEDs and Bioimaging,” Journal of Luminescence 202, no. April (2018): 38–46, https: / / doi.org / 10.1016 / j.jlumin.2018.05.022; Hendrik Bußkamp et al., “Structural Variations in Rare Earth Benzoate Complexes: Part I. Lanthanum,” CrystEngComm 9, no. 5 (2007): 394–411, https: / / doi.org / 10.1039 / b700980a; Anna D. Fedichkina et al., “Ytterbium Complexes with 2-Tosylamino-4-Bromobenzylidene-Halogenbenzoyhydrazones for Highly NIR Emitting Solution-Processed OLEDs,” Journal of Luminescence 244, no. November 2021 (2022): 118702, https: / / doi.org / 10.1016 / j.jlumin.2021.118702; Koen Binnemans, “Rare-Earth Beta-Diketonates,” Handbook on the Physics and Chemistry of Rare Earths 35, no. 05 (2005): 107–272, https: / / doi.org / 10.1016 / S0168-1273(05)35003-3). Luminescent lanthanide compounds are widely used as labels for security purposes, bioimaging, as luminescent materials in optical devices and as sensitive components of sensors.

[0006] From the point of view of use, including as a temperature-sensitive material, aromatic lanthanide carboxylates, which have high stability (chemical, optical, thermal), are of particular interest. Thus, in the work of Anastasia V. Orlova et al., “NIR Luminescence Thermometers Based on Yb-Nd Coordination Compounds for the 83-393 K Temperature Range,” Dalton Transactions 51, no. 14 (2022): 5419-25, https: / / doi.org / 10.1039 / d2dt00147k; Mikhail B. Vialtsev et al., “Lanthanide Complexes for Elevated Temperature Luminescence Thermometry: Mixture vs Bimetallic Compound,” Journal of Alloys and Compounds 924 (2022): 166421, https: / / doi.org / 10.1016 / j.jallcom.2022.166421, show compounds that are stable up to 300°C and retain their thermometric properties up to 120°C.However, among aromatic lanthanide carboxylates, there are extremely few compounds that emit efficiently in the IR region of the spectrum, which is often attributed to the fact that most known organic ligands have significantly higher triplet energy levels, as well as to the susceptibility of IR emitters to many types of quenching (Christine Do et al., “Understanding the Quenching Effects of Aromatic C - H- and C - D- Oscillators in Near-IR Lanthanoid Luminescence,” 2012; Shun Omagari et al., “Origin of Concentration Quenching in Ytterbium Coordination Polymers: Phonon-Assisted Energy Transfer,” European Journal of Inorganic Chemistry 2018, no. 5 (2018): 561–67, https: / / doi.org / 10.1002 / ejic.201701040).

[0007] Luminescent materials based on lanthanide coordination compounds are used to measure temperature based on the temperature dependence of their luminescent characteristics (emission intensity, intensity ratios of different bands, lifetimes). For use in optically dense media, including biological systems, and for long-distance thermometric signal transmission, materials that luminesce in the IR range are the most promising.

[0008] The closest analogue of the claimed inventions of the group is a technical solution that discloses coordination compounds emitting in the IR range with other organic ligands, such as benzene tricarboxylate (BTC) (Mariangela Oggianu et al., “Insights into NdIII to YbIII Energy Transfer and Its Implications in Luminescence Thermometry,” Chemistry of Materials 36 (2024): 3452-63, https: / / doi.org / 10.1021 / acs.chemmater.4c00362). A complex with the specified ligand of the composition Nd 0.89 Yb 0.11 (BTC)(H2O)6 exhibits temperature-dependent neodymium-ytterbium luminescence and is intended for use in biological systems. The closest analogue has several drawbacks. It has insufficient temperature sensitivity (0.94% / K). -1), insufficient luminescence intensity for accurate detection, due to low absorption of lanthanide ions and the lack of interaction with the organic ligand, as well as insufficient thermal stability: the compound decomposes at temperatures of 90-100°C. These shortcomings limit the applicability of this analogue, determining its insufficient temperature resolution and the impossibility of its use in industry, where temperatures reach 200-300°C.

[0009] Thus, the technical problem solved by the group of inventions consists of eliminating the shortcomings of the closest analogue, consisting of insufficient signal intensity, temperature sensitivity and maximum operating temperature, and in developing a luminescent material free of such shortcomings.

[0010] Disclosure of the essence of the invention

[0011] The technical result of the invention is the creation of a new lanthanide compound that has luminescent properties and is suitable for use as a heat-sensitive material, as well as achieving the required luminescence intensity and temperature sensitivity of such a material in an operating temperature range of up to 300°C, as well as the creation of a temperature sensor based on a material made from the new compound.

[0012] The technical result is achieved by the first invention of the group - a coordination compound of the general formula Ln(pyr)3, where

[0013] pyr=

[0014] where Ln is at least one La ion or lanthanide, except Pm promethium, exhibiting luminescent properties.

[0015] In a particular case, in the compound, Ln is selected from the group: La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Lu, and the compound exhibits luminescent properties in the green region of the spectrum.

[0016] In another particular case, in the compound Ln is selected from the group: Tm, Er, and the compound exhibits luminescent properties in the IR range.

[0017] In another particular case, in the compound Ln is selected from the group: Yb or a mixture of ions of the composition Yb x Gd 1-x , where x is the fraction of ytterbium, x=0.1-1, and the compound exhibits luminescent properties and has a luminescence quantum yield in the IR range from 1.5 to 6.1%. At x=1, the value of the subscript expression (1-x) is equal to zero, and, accordingly, Yb x Gd 1-x when x=1 is Yb.

[0018] In the following particular case, in the compound Ln is selected from the group: Nd or a mixture of ions of the composition Yb x Nd 1-x , where x is the fraction of ytterbium, x=0.001-0.2, Nd x Gd 1-x, where x is the fraction of neodymium, x=0.1-1, and the compound exhibits luminescent properties and has luminescence in the IR range, sensitive to temperature changes in the range from 20 to 300°C. At x=1, the value of the subscript expression (1-x) is equal to zero, and, accordingly, Nd x Gd 1-x when x=1 is Nd.

[0019] The following properties of the compound are achieved by using coordination compounds of lanthanides with 1-pyrenecarboxylic acid - pyrenates of the general formula Ln(pyr)3, where Ln is a lanthanide other than promethium, or lanthanum, or at least one lanthanide ion.

[0020] Nd Compounds 3+ , Yb 3+ , Tm 3+ , Er 3+They exhibit intense, narrow-band luminescence that is easy to detect and therefore suitable for use as a sensor signal. High accuracy and ease of detection are ensured, on the one hand, by the narrow width of the characteristic luminescence (ff), and on the other, by the use of the ligand, 1-pyrenate, which exhibits intense absorption and efficient energy transfer to IR-emitting lanthanides.

[0021] Neodymium compounds, as well as bimetallic compounds, exhibit high temperature sensitivity across various temperature ranges. This is due to the selection of a ligand, 1-pyrenate, which is involved in temperature-dependent energy transfer processes. The ability to use the resulting compounds for both cellular measurements and high-temperature applications is ensured by the metal ratios selected for each application, ensuring easily detectable changes in the spectral shape.

[0022] All the resulting compounds are stable and retain their properties after cycling with simultaneous heating and ultraviolet irradiation up to 350°C. This high stability is due to the polymeric structure of the carboxylates and the absence of solvent in the complex.

[0023] The technical result is achieved by the second invention of the group - a luminescent material based on any of the above-mentioned compounds, which is a powder or suspension of the said compound.

[0024] The technical result is achieved by the third invention of the group—a method for producing a luminescent material in powder form, involving the synthesis of any of the aforementioned compounds, which comprises the following steps. An aqueous solution of potassium 1-pyrenate is added to an aqueous solution of a soluble lanthanide salt. The resulting precipitate is boiled with stirring, separated by filtration, then washed with water and dried by heating to 100°C.

[0025] The technical result is achieved by the fourth invention of the group - a temperature sensor including the above-mentioned luminescent material obtained on the basis of any of the above-mentioned compounds by the above-described method, and an optical system for exciting luminescence and recording its signal.

[0026] In a particular case, in the temperature sensor, the said luminescent material is applied to the end of the optical fiber, and the exciting radiation source and the luminescent signal detector are connected to the opposite end of the said optical fiber.

[0027] In another particular case, in a temperature sensor, a luminescent material is applied to the inner walls of a measuring flask into which an optical fiber is inserted, and the source of exciting radiation and the detector of the luminescent signal are connected to the free end of said optical fiber.

[0028] Brief description of drawings

[0029] Fig. 1 shows the compositions of the obtained complexes and the data of thermogravimetric analysis, X-ray phase analysis, and luminescence spectroscopy.

[0030] Implementation of the invention

[0031] The compounds can be obtained, for example, by reacting solutions of potassium 1-pyrenate and a soluble lanthanide salt in water with boiling for 10 minutes (Scheme I). This quantitatively forms anhydrous lanthanide 1-pyrenate, which precipitates:

[0032] 3K(pyr) + LnX3⋅nH2O ⇒ 3Ln(pyr)3↓+ KCl + nH2O (I)

[0033] where X- =Cl - , NO3 - ; n=4-7.

[0034] The complexes are prepared according to scheme (I) as follows. A solution of 3 mmol of potassium 1-pyrenate in 50 ml of water is added to a solution of 1 mmol of a soluble lanthanide salt in 10 ml of water. The resulting precipitate is boiled for 10 minutes with stirring, separated by filtration, washed with water, and dried by heating to 100°C.

[0035] The composition of the target product is determined based on a combination of thermal analysis data with mass spectrometry of the outgoing gases (STA 409 thermal analyzer, NETZSCH, Germany, in the temperature range of 40-1000°C in an air flow, heating rate of 10° / min, initial mass of ~5 mg, QMS 403 quadrupole mass analyzer (NETZSCH, Germany); IR spectroscopy (Thermo Scientific™ Nicolet™ iS50 spectrometer); powder diffractometry; MALDI mass spectrometry (Bruker Autoflex II, nitrogen laser excitation at 337 nm). The presence and region of luminescence are determined by recording the luminescence spectra upon excitation at a wavelength of 365 nm using an Ocean Optics Maya 2000 luminescence spectrometer (response curve 200-1100 nm). The obtained results show that all the obtained compounds are formed as anhydrous complexes and exhibit luminescence.Of particular interest are neodymium, ytterbium, erbium, and thulium complexes, as well as bimetallic compounds containing them, as they exhibit ionic luminescence in the IR range, sensitized by the selected ligand. Moreover, luminescence efficiencies are high for IR-emitting coordination compounds: quantum yields reach 6.1% for Yb. 0.6 Gd 0.4 (pyr)3(τ=40 μs), 1.5% for Yb(pyr)3(τ=25 μs), 0.1±0.2% for compounds of Nd composition x Gd 1-x (pyr)3, where x varies in the range from 0.1 to 1 for mixed-cation compounds with similar properties.

[0036] The results of studying the crystal structure of the complexes revealed the following. According to X-ray powder diffraction data, the Ce-Yb complexes are isostructural, while the lanthanum and lutetium complexes are amorphous. Therefore, the mechanisms for excited-state formation during photoexcitation of pyrenates of all lanthanides except lutetium are similar. For the Ho(pyr)3 complex, the structure was also determined from X-ray diffraction data, confirming the composition determined by TGA and the polymeric structure of the complex.

[0037] Examples of the invention implementation

[0038] The following examples of specific implementation illustrate the inventions of the group, but do not limit them.

[0039] Example 1. Obtaining a compound-complex of the composition Yb(pyr)3 and studying the change in its properties upon heating

[0040] 1) 1 mmol of a hot (~90°C) aqueous solution of a soluble ytterbium salt (YbCl3 6H2O) is added to a hot (~90°C) aqueous solution containing 3 mmol of potassium pyrenecarboxylate (K(pyr)), obtained in situ by the reaction of 1-pyrenecarboxylic acid with an equimolar amount of KOH, with vigorous stirring (400-600 rpm). The resulting suspension is boiled for 10 minutes with gentle stirring (~100-200 rpm), the resulting yellow precipitate is separated by centrifugation, washed three times with water and dried in air by heating to 100°C (e.g. 80°C or 95°C). The yield is 95%.

[0041] 2) Thermogravimetric analysis (TGA) shows that the complex is anhydrous and thermally stable up to 400°C, after which decomposition of the organic fragment begins. After heating to 1000°C, only pure Yb2O3 oxide remains, the mass of which is consistent with the ytterbium content of the original complex.

[0042] 3) The resulting complex exhibits intense IR luminescence with a maximum at 975 nm (excitation at 365 nm), which is typical of ytterbium compounds. When heated in the range of 25-300°C, the emission intensity decreases monotonically, while cyclic heating of the powder in an air atmosphere demonstrates complete reproducibility of the intensity-temperature curves during heating and cooling, confirming the high thermal stability and photostability of the material. The relative temperature sensitivity (Sᵣ) in this range is ~0.15% K -1 .

[0043] Thus, the example demonstrates the possibility of obtaining, using the claimed method, a thermally stable coordination compound of ytterbium with 1-pyrenate ion, which has IR luminescence that changes reproducibly with temperature.

[0044] Example 2. Obtaining and studying the bimetallic ytterbium-neodymium pyrenate (2%Yb 3+ ) for high-temperature thermometry

[0045] 1) The complex is synthesized using a procedure similar to Example 1. The starting reagents are a mixture of ytterbium and neodymium chlorides (YbCl3⋅6H2O and NdCl3⋅6H2O) in a molar ratio of Yb:Nd = 2:98, with the ratio being achieved by adding an aliquot of an aqueous solution of ytterbium chloride (800 μl of a 0.025 M solution) to 0.98 mmol of neodymium chloride. Hot (60-90°C) solutions of the chloride mixture and the potassium salt of the ligand are mixed and the resulting suspension is boiled for 10 minutes. The resulting light yellow precipitate is separated by centrifugation, washed three times with water and dried in air at 60-100°C.

[0046] 2) The obtained complex, according to thermogravimetric analysis and X-ray diffraction data, has the composition Yb 0.02 Nd 0.98(pyr)3. X-ray diffraction (XRD) analysis in the range of 30–350°C demonstrates no changes in the diffraction patterns, confirming the preservation of the complex's crystalline structure during cyclic heating. Thermogravimetric analysis indicates the onset of decomposition at temperatures above 400°C, as with monometallic analogs.

[0047] 3) The luminescence spectrum of the complex at room temperature (excit. 365 nm) contains characteristic bands of neodymium (808, 890, 1060 nm) and ytterbium (980 nm). When heated from 25 to 300 °C, a change in the shape of the luminescence spectrum is observed: the intensity of the band at 808 nm gradually increases, and the bands at 890 and 980 nm, on the contrary, decrease in intensity, while the rate of decrease of the ytterbium band is higher. As a thermometric signal, both the ratio of the two neodymium bands and the bands of neodymium and ytterbium can be used. Both ratios demonstrate a strong temperature dependence, increasing more than 5 times in the specified range. The curves of the dependences of the band intensity ratio on temperature are reproducible for at least 5 consecutive heating-cooling cycles. The maximum relative temperature sensitivity reaches 5.0%K -1 .

[0048] Thus, this example confirms that the introduction of 2% ytterbium into neodymium pyrenate creates a material with exceptional stability and high ratiometric sensitivity in the high-temperature range, making it suitable for precision thermometry in industrial processes. Furthermore, the ability to use two different band sets provides additional flexibility in the design of the final device's optical circuit.

[0049] Example 3. Obtaining and studying a suspension of bimetallic ytterbium-neodymium pyrenate (0.5%Yb 3+ ) for intracellular thermometry

[0050] 1) The complex is synthesized by an exchange reaction similar to the examples described above. An aqueous solution of a mixture of ytterbium and neodymium chlorides (YbCl3⋅6H2O and NdCl3⋅6H2O) in a molar ratio of Yb:Nd = 0.5:99.5 was mixed with a concentrated aqueous solution of sodium pyrenate while heating. The resulting mixture was heated for 10 minutes while being dispersed in an ultrasonic bath, then diluted with water to a concentration of 0.5 mg / ml and redispersed.

[0051] 2) The suspension obtained by the described method, according to dynamic light scattering data, contains complex particles up to 55 nm in size and a polydispersity index below 0.2, which is a low value and indicates an average size deviation of 44% and sufficient stability of the colloidal system for use in cellular systems. According to TGA and X-ray diffraction data, the particles, washed to remove sodium chloride and dried, have a composition and structure similar to those of powders obtained without dispersion.

[0052] 3) The nanoparticle suspension exhibits characteristic luminescence of neodymium (890 and 1060 nm) and ytterbium (975 nm), with a 0.5% ytterbium content providing comparable band intensities for these ions at room temperature in aqueous media and biological fluids. When the suspension is heated in the physiological temperature range (25-45°C), the ratio of the ytterbium and neodymium bands changes reproducibly with a sensitivity of 1.5%K. -1 The signal intensity is sufficient for detection by standard confocal microscopes.

[0053] 4) The resulting suspension is suitable for measuring temperature in cells and has low toxicity, as demonstrated by more than 85% survival of human fibrosarcoma HT1080 cells after 24-hour incubation with the suspension as assessed by the MTT test."

[0054] Confocal microscopy confirms the efficient capture of nanoparticles and their accumulation in cellular endosomes. Accumulating in cells, the complex retains its luminescent thermometric properties.

[0055] The above-described method was used to obtain luminescent materials based on complex compounds of the composition Yb(pyr)3, Yb 0,02 Nd 0,98 (pyr)3, which are powders or suspensions of the specified compounds.

[0056] Using this material, a temperature sensor was fabricated, comprising the aforementioned luminescent material and an optical system, which in some cases may include an LED, an optical fiber, and a detector for exciting luminescence and recording its signal. In one particular case, the luminescent material is deposited on the end of the optical fiber. The excitation source and luminescence signal detector are connected to the opposite end of the optical fiber.

[0057] A temperature sensor with another implementation was also manufactured. The aforementioned luminescent material is applied to the inner walls of a measuring flask, into which an optical fiber is inserted. The excitation source and luminescence signal detector are connected to the free end of the optical fiber.

[0058] During experiments, both temperature sensor variants made from the above-mentioned material demonstrated results that allow them to be considered suitable for safe and highly sensitive temperature measurement inside living organisms. The thermometer's sensitivity is 3.5% / K over an operating range of up to 300°C, and the response curve is maintained over ten measurement cycles.

[0059] The presented examples demonstrate the potential for adapting the claimed complex compounds for biomedical applications. The low ytterbium content ensures a high signal for both ions in the cellular environment and an effective channel for ratiometric measurements, while ultrasonic dispersion allows for the production of stable nanoparticles suitable for safe and highly sensitive temperature measurement inside living cells.

[0060] These examples allow us to draw a conclusion about the possibility of obtaining all the claimed compounds, as well as a luminescent material based on these compounds, as well as a temperature sensor, and the presence of the properties specified in the technical result.

Claims

1. A compound of the general formula Ln(pyr)3, where pyr = where Ln is at least one La ion or lanthanide other than promethium, Pm, exhibiting luminescent properties.

2. The compound according to claim 1, wherein Ln is selected from the group: La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Lu, exhibiting luminescent properties in the green region of the spectrum.

3. The compound according to claim 1, wherein Ln is selected from the group: Tm, Er, exhibiting luminescent properties in the IR range.

4. The compound according to claim 1, wherein Ln is selected from the group: Yb or a mixture of ions of the composition Yb x Gd 1-x , where x is the proportion of ytterbium, x=0.1-1, exhibiting luminescent properties and having a quantum yield of luminescence in the IR range from 1.5 to 6.1%.

5. The compound according to claim 1, wherein Ln is selected from the group: Nd or a mixture of ions of the composition Yb x Nd 1-x , where x is the fraction of ytterbium, x=0.001-0.2, Nd x Gd 1-x, where x is the proportion of neodymium, x=0.1-1, exhibiting luminescent properties and possessing luminescence in the IR range, sensitive to temperature changes in the range from 20 to 300°C.

6. A luminescent material based on a compound according to any one of paragraphs 1-5, which is a powder or suspension of the said compound.

7. A method for producing a luminescent material in powder form, which comprises synthesizing a compound according to any one of paragraphs 1-5, including the following steps: - an aqueous solution of potassium 1-pyrenate is added to an aqueous solution of a soluble lanthanide salt, - the precipitate is boiled while stirring, - separated by filtration, - rinse with water, - dried by heating to 100°C.

8. A temperature sensor comprising a luminescent material according to paragraph 6 and an optical system for exciting luminescence and recording its signal.

9. A temperature sensor according to claim 8, characterized in that said luminescent material is applied to the end of the optical fiber, and the source of exciting radiation and the detector of the luminescent signal are connected to the opposite end of said optical fiber.

10. A temperature sensor according to claim 8, characterized in that said luminescent material is applied to the inner walls of a measuring flask into which an optical fiber is inserted, and wherein the source of exciting radiation and the detector of the luminescent signal are connected to the free end of said optical fiber.

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