Tunable luminescent organic-inorganic hybrid manganese-based compounds, methods of preparation and use

Abstract

The application belongs to the technical field of fluorescent materials, and particularly relates to a luminescent adjustable organic-inorganic hybrid manganese-based compound, a preparation method and application. 13 N2O) + , (C9H 13 N2O) + is obtained by protonating nitrogen in a morpholine ring of 4-morpholine pyridine. The (4-Mor-Py)2MnBr4 in the application is more sensitive to temperature change by the interaction of organic cations and inorganic frameworks, and still maintains high fluorescence stability at high temperature. The (4-Mor-Py)2MnBr4 in the application has simple preparation process, is easy to mass produce, has easily available raw materials, small environmental pollution and high fluorescence intensity. The compound can be used to comprehensively mark temperature by the double parameters of fluorescence peak intensity and half peak width change in the range of 80K-400K.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fluorescent materials, and particularly relates to a luminescent organic-inorganic hybrid manganese-based compound with adjustable luminescence, and a preparation method and application thereof. BACKGROUND

[0002] The luminescence temperature measurement technology has urgent demands in the fields of industrial equipment monitoring, chip in-situ temperature measurement and low-temperature physical research due to its remote, non-contact and high-precision characteristics. The application scenarios require that the material can realize stable response in a specific temperature range, especially in the medium and low temperature range, and meet the industrial requirements of simple detection operation and controllable cost. Among them, the temperature measurement method based on the changes of fluorescence parameters such as intensity, peak position and lifetime has become a research hotspot in recent years because it does not require complex calibration equipment.

[0003] The traditional temperature sensor has limitations, and the current mainstream temperature sensing technology such as thermocouple and semiconductor sensor has problems such as slow response speed, large environmental interference on precision and difficulty in miniaturization. The fluorescent temperature sensing technology has become a research hotspot due to its advantages such as high sensitivity, non-contact measurement and integrability. However, the existing fluorescent materials such as rare earth doped oxides and quantum dots have defects such as complex synthesis process, low fluorescence intensity and poor stability, which limit their practical application.

[0004] The organic-inorganic hybrid material combines the designability of organic molecules and the excellent optical performance of inorganic materials, and becomes an ideal choice to solve the above problems. Among them, the manganese-based hybrid material has attracted widespread attention in recent years because the manganese ion has the advantages of rich d-d transition luminescence characteristics, low toxicity and low cost. However, the traditional manganese-based hybrid material has two key problems, i.e., the non-radiative transition leads to low luminescence efficiency, and the distance between manganese ions is too close to easily cause energy quenching; the temperature response is single, and the existing materials mostly rely on the change of fluorescence intensity to calibrate the temperature, which is easily affected by light source fluctuation and material concentration. SUMMARY

[0005] In order to solve the above technical problems, the application provides a luminescent organic-inorganic hybrid manganese-based compound with adjustable luminescence and a preparation method thereof. The combination of fluorescence intensity and half peak width forms a double-parameter temperature response model, which solves the problem that a single parameter is easily affected by environmental interference.

[0006] The technical scheme of the application is as follows.

[0007] The first aspect of the application provides a luminescent organic-inorganic hybrid manganese-based compound with adjustable luminescence, and the structural formula is (4-Mor-Py)2MnBr4, 4-Mor-Py is (C9H 13 N2O) + , and (C9H 13 N2O) +is obtained by protonating the nitrogen in the morpholine ring of 4-morpholinopyridine.

[0008] The present application protonates the nitrogen in the morpholine ring of 4-morpholinopyridine, so that (C9H 13 N2O) + The lone pair of electrons is introduced in the presence of the nitrogen atom in the heterocyclic ring, which forms a conjugated system with the pyridine ring, further affecting the electron cloud distribution and energy level structure of the molecule, which is conducive to the generation of fluorescence, thereby forming a two-parameter temperature response, and therefore the present application selects 4-morpholinopyridine as an organic ligand.

[0009] In another preferred embodiment, the crystal cell parameters of the luminescence-adjustable organic-inorganic hybrid manganese-based compound are a=7.8986(15)Å, b=17.771(3)Å, c=9.2047(15)Å; alpha=90 degrees, beta=100.212(17) degrees, gamma=90 degrees, z=2.

[0010] The second aspect of the present application provides a preparation method of the luminescence-adjustable organic-inorganic hybrid manganese-based compound, comprising the following steps:

[0011] 4-morpholinopyridine and hydrobromic acid are subjected to protonation reaction in an organic reagent environment to obtain (C9H 13 N2O) + After adding MnBr2.4H2O, the solvent is volatilized and crystallized to obtain the luminescence-adjustable organic-inorganic hybrid manganese-based compound.

[0012] In another preferred embodiment, the molar volume ratio of 4-morpholinopyridine to hydrobromic acid is 5mmol~5.2mmol:2mL~2.4mL.

[0013] In another preferred embodiment, the organic reagent is methanol.

[0014] In another preferred embodiment, the temperature of the volatilized solvent is 25℃~28℃.

[0015] In another preferred embodiment, the (C9H 13 N2O) + The molar ratio of (C9H

[0016] The third aspect of the present application provides the application of the luminescence-adjustable organic-inorganic hybrid manganese-based compound in the preparation of fluorescent materials.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] This invention designs the structure of an organic-inorganic hybrid manganese-based compound, using 4-morpholinopyridine as the organic ligand. 4-morpholinopyridine contains a polar O atom in the morpholine ring and a conjugated N atom in the pyridine ring, and can interact with the Br atom of the inorganic framework via van der Waals forces. - This forms a strong interaction. This interaction can limit the lattice vibration amplitude of the [MnBr6] octahedron, causing Mn to exhibit different crystal structures at different temperatures. 2+ The coordination environment is more uniform, avoiding irregular broadening of the full width at half maximum (FWHM) due to vibrational disorder, allowing even minor temperature effects on the crystal field to be directly reflected in changes in FWHM. Furthermore, the cyclic structure of 4-morpholinopyridine, consisting of the morpholine and pyridine rings, has significant steric hindrance, which, when combined with the inorganic framework, can support the crystal lattice structure and suppress lattice distortion or collapse at high temperatures. Mn 2+ The fluorescence properties are highly dependent on the symmetry of its coordination environment [MnBr6] octahedron; a stable lattice can maintain the symmetry of Mn. 2+ The coordination state remains unchanged, avoiding fluorescence quenching caused by disruption of the coordination environment. Through the interaction between the organic cation and the inorganic framework, the half-peak width (HWHM) becomes more sensitive to temperature changes, maintaining high fluorescence stability even at high temperatures. The compound in this invention has a simple preparation process, is easy to mass-produce, uses readily available raw materials, causes minimal environmental pollution, and exhibits high fluorescence intensity. The temperature of this compound can be calibrated using a combination of fluorescence peak intensity and HWHM changes within the range of 80K to 400K. Attached Figure Description

[0019] Figure 1 The diagram shows the crystal structure of (4-Mor-Py)2MnBr4, where A is the schematic diagram of the smallest asymmetric unit and B is the packing diagram of (4-Mor-Py)2MnBr4.

[0020] Figure 2 The thermogravimetric analysis results of (4-Mor-Py)2MnBr4 are shown in the figure.

[0021] Figure 3 The image shows the fluorescence spectrum of (4-Mor-Py)2MnBr4, where Em represents the emission wavelength and Ex represents the excitation wavelength.

[0022] Figure 4 The fluorescence quantum yield spectrum of (4-Mor-Py)2MnBr4 is shown.

[0023] Figure 5 The results of temperature-dependent fluorescence testing of (4-Mor-Py)2MnBr4 are shown in Figure A. In Figure B, the fluorescence spectrum is a graph showing the intensity of fluorescence peaks at different temperatures. In Figure C, the fluorescence peak width at half maximum (HWHM) is a graph showing the intensity of fluorescence peaks at different temperatures.

[0024] Figure 6 The fluorescence chromaticity diagram of (4-Mor-Py)2MnBr4 is shown.

[0025] Figure 7 This is a schematic diagram of the structure of 4-morpholinopyridine. The circled N in the diagram represents the protonated nitrogen atom. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0028] Limitations of traditional temperature sensors: Current mainstream temperature sensing technologies, such as thermocouples and semiconductor sensors, suffer from slow response speeds, high susceptibility to environmental interference in accuracy, and difficulty in miniaturization. Fluorescent temperature sensing technology, with its advantages of high sensitivity, non-contact measurement, and integrability, has become a research hotspot. However, existing fluorescent materials, such as rare-earth-doped oxides and quantum dots, generally suffer from complex synthesis processes, low fluorescence intensity, and poor stability, limiting their practical applications.

[0029] Advantages of Organic-Inorganic Hybrid Materials: Organic-inorganic hybrid materials combine the designability of organic molecules with the excellent optical properties of inorganic materials, making them an ideal choice for solving the aforementioned problems. Among them, manganese-based hybrid materials have received widespread attention in recent years due to the abundant dd transition luminescence characteristics of manganese ions, low toxicity, and low cost. However, traditional manganese-based hybrid materials have two key problems: firstly, non-radiative transitions lead to low luminescence efficiency, and the close proximity of manganese ions can easily cause energy quenching; secondly, the temperature response is singular, with existing materials mostly relying solely on changes in fluorescence intensity for temperature calibration, making them susceptible to fluctuations in light source and material concentration.

[0030] The existing synthesis processes for organic-inorganic hybrid manganese-based luminescent materials are complex and demanding, making it difficult to balance low-cost scalability with the integrity of luminescent centers. The preparation of organic-inorganic hybrid manganese-based luminescent compounds often relies on non-mild conditions, such as high-temperature, high-pressure solvothermal reactions (120℃~200℃, 1MPa~5MPa), template-assisted synthesis requiring expensive organic templates like ionic liquids, and multi-step reflux / annealing treatments, all of which have significant drawbacks. Traditional manganese-based hybrid materials exhibit insufficient fluorescence stability at high temperatures and are prone to fluorescence quenching. Furthermore, they are dependent on a single parameter: existing technologies are mostly based on single parameters such as fluorescence intensity ratio or full width at half maximum (FWHM), failing to distinguish between temperature changes and interference factors such as light source fluctuations and material concentration.

[0031] This invention provides an organic-inorganic hybrid manganese-based luminescent compound and its preparation method. The compound's preparation process is simple, easy to mass-produce, uses readily available raw materials, has low environmental pollution, and exhibits high fluorescence intensity. The temperature of this compound can be calibrated using a two-parameter combined approach of fluorescence peak intensity and full width at half maximum (FWHM) variation within the 80K–400K range. This invention solves the problem of single-parameter susceptibility to environmental interference by combining fluorescence intensity and FWHM to form a two-parameter temperature response model, as detailed below:

[0032] Material Structure and Properties: While traditional manganese-based hybrid materials improve luminescence efficiency by separating the Mn-Mn distance using organic cations, they do not address the temperature response characteristics of the full width at half maximum (FWHM). The compounds of this invention further optimize the interaction between the organic cations and the inorganic framework in their structural design, making the FWHM more sensitive to temperature changes and maintaining high fluorescence stability at high temperatures. Specifically, 4-morpholinopyridine contains a polar O atom in the morpholine ring and a conjugated N atom in the pyridine ring, which can interact with the Br atom in the inorganic framework through van der Waals forces. - This forms a strong interaction. This interaction can limit the lattice vibration amplitude of the [MnBr6] octahedron, causing Mn to exhibit different crystal structures at different temperatures. 2+ The coordination environment is more uniform, avoiding irregular broadening of the full width at half maximum (FWHM) due to vibrational disorder, allowing even minor temperature effects on the crystal field to be directly reflected in changes in FWHM. Furthermore, the cyclic structure of 4-morpholinopyridine, consisting of the morpholine and pyridine rings, has significant steric hindrance, which, when combined with the inorganic framework, can support the crystal lattice structure and suppress lattice distortion or collapse at high temperatures. Mn 2+ The fluorescence properties are highly dependent on the symmetry of its coordination environment [MnBr6] octahedron; a stable lattice can maintain the symmetry of Mn. 2+ The coordination state remains unchanged, thus avoiding fluorescence quenching caused by disruption of the coordination environment.

[0033] Synthesis Method: Existing methods such as antisolvent methods and mechanical grinding methods require strict temperature control or the use of toxic solvents. The synthesis process of this invention is simpler and can potentially achieve large-scale preparation through a one-step solution method. The raw materials, manganese salts and organic amines, are inexpensive and readily available. The process requires no special equipment and can be directly scaled up for industrial production.

[0034] The following is a detailed description of an organic-inorganic hybrid manganese-based compound with tunable luminescence, its preparation method, and its applications.

[0035] 1. Preparation of organic-inorganic hybrid manganese-based compounds.

[0036] 5 mmol of 4-morpholinopyridine (C9H) 12 N₂O was added to a 50 mL beaker, followed by 15 mL of anhydrous methanol. After the reactants were fully dissolved, 2 mL of 40% hydrobromic acid was added for protonation. Specifically, the nitrogen atom on the morpholine ring of 4-morpholinopyridine was protonated.Figure 7 As shown. 2.5 mmol of manganese bromide tetrahydrate was added to a beaker and dissolved completely to obtain a pale yellow transparent solution. The solution was placed in a glove box at 25°C to evaporate the solvent and crystallize. After two days, green transparent blocky crystals were obtained, which are the organic-inorganic hybrid manganese-based compound, hereinafter referred to as (4-Mor-Py)2MnBr4.

[0037] 2. Structural characterization.

[0038] The obtained (4-Mor-Py)₂MnBr₄ crystal was analyzed, and structural measurements were performed on a Rigaku SCX-mini single-crystal diffractometer with dimensions of (0.20 × 0.21 × 0.23) mm. 3 The nitrogen protonation of the morpholine ring in crystalline pyridine was used for single-crystal structure analysis, and diffraction data were collected at 293 K. The crystal structure was solved using Olex2 software. First, the coordinates of all non-hydrogen atoms were determined using the difference Fourier function method and the least squares method, and the positions of hydrogen atoms were obtained using the theoretical hydrogenation method. Then, the crystal structure was refined anisotropically using the least squares method. The crystal structure diagram was drawn using Diamond software.

[0039] (4-Mor-Py)₂MnBr₄ crystallizes in the monoclinic crystal system, space group P21, with cell parameters a = 7.8986(15) Å, b = 17.771(3) Å, c = 9.2047(15) Å; α = 90°, β = 100.212(17)°, γ = 90°, z = 2. The two 4-morpholinopyridine bicyclic rings are arranged sequentially along the b-axis and c-axis, respectively; [MnBr₄] 2- It has a tetrahedral structure, with each tetrahedron independent of the others, forming a 0-dimensional structure. Specifically, as shown... Figure 1 The figures shown are the minimum asymmetric unit cell and the packing diagram of (4-Mor-Py)2MnBr4, respectively.

[0040] 3. Thermogravimetric analysis and fluorescence test.

[0041] 1) Thermogravimetric analysis: Thermogravimetric analysis was performed on (4-Mor-Py)₂MnBr₄ using a PerkinElmer TGA 8000 thermogravimetric analyzer. The results showed that the thermal stability of (4-Mor-Py)₂MnBr₄ reached 568K. Figure 2 As shown.

[0042] 2) Fluorescence Properties: Fluorescence excitation and emission spectra of (4-Mor-Py)₂MnBr₄ were measured at 25℃. The compound was excited using excitation light at wavelengths of 330 nm, 360 nm, 370 nm, 380 nm, 390 nm, 435 nm, 445 nm, 450 nm, and 455 nm, with an emission peak wavelength of 525 nm for all wavelengths. Excitation spectroscopy of the 525 nm emission peak was performed, revealing five excitation peaks within the 300 nm to 470 nm band, with the optimal excitation wavelength for the 525 nm emission peak being 450 nm. The fluorescence spectrum of (4-Mor-Py)₂MnBr₄ is shown below. Figure 3 As shown, (4-Mor-Py)2MnBr4 exhibits single-band green emission at 525 nm at 25℃, with the highest excitation efficiency at 450 nm; the narrow peak and no shift indicate that it has excellent fluorescence properties with high color purity, no self-absorption, and flexible excitation selection.

[0043] 3) Fluorescence quantum yield: The fluorescence quantum yield of (4-Mor-Py)₂MnBr₄ was measured at 25℃ using the integrating sphere method. The measured quantum yield of (4-Mor-Py)₂MnBr₄ was 53.49%. Figure 4 As shown.

[0044] 4) Temperature-dependent fluorescence assay: With a fixed excitation wavelength of 450 nm, temperature-dependent fluorescence assays were performed on (4-Mor-Py)₂MnBr₄. The results showed that within the temperature range of 80 K to 400 K, the fluorescence intensity and full width at half maximum (FWHM) of (4-Mor-Py)₂MnBr₄ changed with temperature. Integrating the fluorescence peaks at each temperature, the results showed that with increasing temperature, the fluorescence peak intensity gradually decreased, while the FWHM gradually increased. Combining these two values ​​allows for temperature calibration. (Specific details are as follows...) Figure 5 The figures show the temperature-dependent fluorescence spectra of (4-Mor-Py)2MnBr4, and the integral results of the peak intensity and half-width at each temperature.

[0045] Linear fitting was performed on the fluorescence peak intensity to obtain the relationship between fluorescence peak intensity (y-axis) and temperature (x-axis): y = -32055.50x + 1.86 × 10⁻⁶ 7 Goodness of fit R 2 The value is 0.9993, proving that the fitting formula matches the test results well. Polynomial fitting was performed on the half-width at half-maximum (WHM) of the fluorescence peak, yielding the relationship between the WHM of y and temperature (x-axis): y = (-8.60 × 10⁻⁵)x 2 +0.10x+24.64, goodness of fit R 2 The value is 0.9999, which proves that the test results of the fitting formula are in good agreement.

[0046] 5) Fluorescence chromaticity diagram: The position of the emitted color on the color wheel is calculated and plotted using CIE software based on the fluorescence data, such as... Figure 6 As shown, the results indicate that the emission color of (4-Mor-Py)2MnBr4 gradually changes with increasing temperature. The crystal structure, fluorescence properties, and low-temperature fluorescence thermosensitivity of (4-Mor-Py)2MnBr4 demonstrate that this organic-inorganic hybrid manganese-based luminescent compound has promising applications in temperature sensing.

[0047] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A luminescent organic-inorganic hybrid manganese-based compound, characterized in that, The structural formula is (4-Mor-Py)2MnBr4, where 4-Mor-Py is (C9H 13 N2O) + ; The (C9H) 13 N2O) + It is obtained by protonation of the nitrogen atom on the morpholine ring in 4-morpholine pyridine.

2. The luminescent organic-inorganic hybrid manganese-based compound according to claim 1, characterized in that, The cell parameters of the luminescent tunable organic-inorganic hybrid manganese-based compound are a=7.8986(15)Å, b=17.771(3)Å, c=9.2047(15)Å; α=90°, β=100.212(17)°, γ=90°, z=2.

3. A method for preparing the luminescent organic-inorganic hybrid manganese-based compound of claim 2, characterized in that, Includes the following steps: 4-morpholinopyridine and hydrobromic acid were protonated in an organic reagent environment to give (C9H) 13 N2O) + MnBr2·4H2O was added to carry out the reaction. After the solvent evaporated, crystals precipitated, which is the luminescent organic-inorganic hybrid manganese-based compound.

4. The preparation method according to claim 3, characterized in that, The molar volume ratio of the 4-morpholinopyridine to the hydrobromic acid is 5 mmol to 5.2 mmol: 2 mL to 2.4 mL.

5. The preparation method according to claim 3, characterized in that, The organic reagent is methanol.

6. The preparation method according to claim 3, characterized in that, The (C9H) 13 N2O) + The molar ratio of MnBr2·4H2O is 2~2.2:0.9~1.

7. The preparation method according to claim 3, characterized in that, The solvent evaporates at a temperature of 25°C to 28°C.

8. The application of the luminescence-tunable organic-inorganic hybrid manganese-based compound of claim 2 in the preparation of fluorescent materials.

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