Use of a class of tetra-substituted tetrahydropyrimidine derivatives for the preparation of temperature-sensitive fluorescent materials

Abstract

The application discloses application of a kind of tetra-substituted tetrahydropyrimidine derivatives in preparing temperature-sensitive fluorescent material.Tetra-substituted tetrahydropyrimidine derivatives have the structure shown in the following formula (I): R 1 selected from C 1‑5 linear or branched alkyl or substituted C 1‑5 linear or branched alkyl; R 2 , R 3 each independently selected from hydrogen, C 5‑6 aromatic group, C 1‑8 linear or branched alkoxy, C 1‑8 linear or branched alkyl, trifluoromethyl, halogen.Tetra-substituted tetrahydropyrimidine derivatives have temperature range adjustable fluorescent characteristics and thermal-optical-size-adjusted two-color fluorescent conversion characteristics, and have excellent anti-counterfeiting effect.

Description

Technical Field

[0001] This invention belongs to the technical field of temperature-sensitive organic light-emitting materials, and more specifically, relates to the application of a class of tetrasubstituted tetrahydropyrimidine derivatives in the preparation of temperature-sensitive fluorescent materials. Background Technology

[0002] Temperature is one of the most fundamental parameters affecting physicochemical and biological metabolic processes. Therefore, temperature monitoring and measurement are indispensable in daily life, agriculture, industrial production, and scientific research. Fluorescent temperature probes have advantages such as ultra-high sensitivity, fast response speed, high spatial resolution, and safe and non-invasive detection signals, making them ideal temperature probes for real-time monitoring of microenvironment temperature and temperature distribution, and have attracted widespread attention. Currently reported temperature-sensing fluorescent materials include polymer fluorescent compounds (ChemSci 2020;11(1):141-47), small organic molecule fluorescent compounds (Nat. Commun. 2022, 13 (1), 5280), organometallic complexes (ACS Appl Mater Interfaces 2021;13(9):11078–88), and lanthanide transition metals (J.Am. Ceram. Soc. 2022, 105, 6184).

[0003] However, reported fluorescent temperature probes generally only exhibit high sensitivity within a narrow temperature range, meaning they can only be used within a specific temperature range. For example... Figure 1 Different types of fluorescent temperature-sensitive probes can only operate within a relatively narrow, specific temperature range (20-80°C). C, 20-50 C and 20-70 C) Sensitive changes occur, which to some extent limits the application of fluorescent temperature probes. To prepare fluorescent temperature probes for different temperature ranges, some researchers have attempted to change the size of the doped semiconductor nanocrystals (Nano Lett 2010;10(9):3670-74) (e.g. Figure 2 As shown), different molecular beacons are combined on gold nanoparticles (ACS Nano 2014;8(10):10372-82) (e.g. Figure 3 As shown), and the preparation of dihydrophenazine derivative (DPC) suspensions using ethanol-glycerol mixed solvents containing different proportions of glycerol (Mater. Horiz. 2020;7(2):615-623) (as shown). Figure 4As shown in the figure, the fluorescent temperature probe can sensitively detect fluorescence changes across different temperature ranges. However, it is obvious that these methods can only measure a few limited temperature ranges, or can only monitor one temperature range under certain conditions, and do not fundamentally solve the problem of the inability to adjust the temperature range of the fluorescent temperature probe.

[0004] Chinese patent CN104845613A discloses racemic C6 unsubstituted tetrahydropyrimidines (THPs), whose solid form exhibits unique temperature-range-tunable (TRT) fluorescence characteristics: red-edge excitation wavelength ( λ rex The fluorescence intensity exhibits a positive linear dependence on temperature. By selecting an appropriate excitation wavelength, the fluorescence intensity can sensitively vary across different temperature ranges, showing a strong positive linear dependence. This allows for precise and sensitive measurement of temperatures within any approximately 30-degree range from -260 ºC to near the compound's melting point, such as 10-30 K, 30-60 K, ..., 400-430 K, i.e., -263 to -230 ºC, -243 to -213 ºC, ..., +127 to +157 ºC. Essentially, this achieves temperature-range-tunable (TRT) fluorescence temperature measurement. For example, the green-fluorescent polycrystalline form of THP-1 (THP-1g) (molecular structure and crystal structure are shown in...) Figure 5 Within the temperature range of 77-300 K, its red-edge excitation wavelength and fluorescence intensity change sensitively with temperature (see...). Figure 6 a) and exhibits a strong positive linear dependence on temperature, with its red-edge excitation wavelength... λ rex Sensitivity to temperature changes ( S λrex )See Figure 6 b and 6c. For example... Figure 7 As shown, by selecting different red-edge excitation wavelengths, THP-1g exhibits sensitive fluorescence intensity changes within a temperature range of 20-90 °C between 77-300 K, showing a strong positive dependence on temperature. This allows for the determination of temperatures across different temperature ranges. For example, selecting 420 and 445 nm as excitation wavelengths reveals sensitive changes in THP-1g fluorescence intensity with temperature, enabling precise and sensitive measurement of temperatures in the 80-120 K and 210-310 K ranges, respectively. Studies have shown the influence of molecular structure, molecular packing mode, and chiral structure on the unique RTR fluorescence properties of THPs. Dyes Pigments 2022, 197(109912), the results showed that the TRT fluorescence properties of THPs mainly depend on the molecular structure, rather than the packing pattern of their enantiomers, and the red-edge excitation wavelength λ rex Sensitivity to temperature changes ( S λrex The thermo-optical-size tunable fluorescence (TRT) is a key parameter determining the TRT fluorescence properties of THPs and the sensitivity of fluorescence intensity to temperature changes. However, the aforementioned patent does not mention that the compounds THPs possess thermo-optical-size tunable dual-color fluorescence properties that allow them to be loaded onto other materials to prepare excellent anti-counterfeiting materials.

[0005] The paper "Aggregation-induced emission and reversible mechanofluorochromic characteristics of tetra-substituted tetrahydropyrimidine derivatives" (Yingyu Lai, Junlong Huang) discloses a class of tetrasubstituted tetrahydropyrimidine compounds (TTHPs) exhibiting aggregation-induced emission (AIE) and reversible pressure-induced fluorescence. TTHPs are non-luminescent in solution but exhibit strong fluorescence upon aggregation, with a fluorescence quantum rate as high as 80%, demonstrating a strong AIE effect. Furthermore, these TTHPs compounds also possess reversible pressure-induced fluorescence, changing color after grinding. However, the paper does not mention the unique temperature-range-tunable (TRT) fluorescence properties of the TTHPs compounds, which could be used to prepare highly sensitive TRT ratiometric fluorescent temperature probes. Nor does it mention the thermo-optical-size-tunable dual-color fluorescence properties of the TTHPs compounds, which could be used to prepare excellent anti-counterfeiting materials. Summary of the Invention

[0006] To address the aforementioned technical problems, the primary objective of this invention is to provide the application of a class of tetrasubstituted tetrahydropyrimidine derivatives in the preparation of temperature-sensitive fluorescent materials. These tetrasubstituted tetrahydropyrimidine derivatives (TTHPs) possess temperature-range tunable fluorescence properties, making them suitable for preparing highly sensitive ratiometric fluorescence temperature probes. Furthermore, they exhibit thermo-optical-size-tunable dual-color fluorescence properties, enabling the preparation of excellent anti-counterfeiting materials. Under specific temperature and illumination (excitation wavelength), the dual-color fluorescence changes of the derivatives can be synergistically controlled, resulting in superior anti-counterfeiting effects.

[0007] A second object of the present invention is to provide the application of the said tetrasubstituted tetrahydropyrimidine derivative in the preparation of biological and / or chemical temperature fluorescence sensors or probes.

[0008] A third objective of this invention is to provide the application of the aforementioned tetrasubstituted tetrahydropyrimidine derivative in the preparation of anti-counterfeiting materials or products having temperature-range tunable fluorescence properties and / or temperature / light-induced dual fluorescence color change.

[0009] The fourth objective of this invention is to provide an anti-counterfeiting product.

[0010] To achieve the above objectives, the present invention is implemented through the following technical solution: Application of a class of tetrasubstituted tetrahydropyrimidine derivatives in the preparation of temperature-sensitive fluorescent materials, wherein the tetrasubstituted tetrahydropyrimidine derivatives have the structure shown in formula (I):

[0011] (I) Among them, R 1 Selected from C 1-5 Straight-chain or branched alkyl or substituted C 1-5 Straight-chain or branched alkyl groups; R 2 R 3 Each is independently selected from hydrogen and C. 5-6 Aromatic group, C 1-8 Straight-chain or branched alkoxy groups, C 1-8 Straight-chain or branched alkyl groups, trifluoromethyl groups, and halogens.

[0012] The inventors discovered through research that the aforementioned TTHPs possess temperature-range tunable fluorescence properties. Compared to existing TRT fluorescent temperature probes, TTHPs have a simpler molecular structure, a simpler synthesis method, and more sensitive TRT properties. The inventors found that the red-edge excitation wavelength of TTHPs (…) λ rex The redshift occurs with increasing temperature; different excitation wavelengths can be selected, at -195°C. The fluorescence intensity can change sensitively within any temperature range of approximately 30-60°C from C (78 K) to near the melting point of the compound, such as 78-120 K, 120-130 K, ..., 360-420 K. This range shows a strong linear dependence on temperature, allowing for precise and sensitive measurement of temperatures in different ranges. This results in temperature-range-tunable (TRT) fluorescence characteristics.

[0013] Furthermore, the inventors unexpectedly discovered that the aforementioned TTHPs also possess thermo-optical-size-tunable dual-color fluorescence conversion characteristics. These thermo-optical-size-tunable dual-color fluorescence conversion characteristics can be achieved within any temperature range from 78K to near the compound's melting point, and within any wavelength range from the excitation wavelength corresponding to the peak of the compound's excitation spectrum to the wavelength corresponding to approximately one-tenth of the peak of the red edge of the excitation spectrum. The dual-color fluorescence ratio of TTHPs can also be controlled by the nanoparticle size, and they can be loaded onto other materials. By controlling the ratio of the dual-color fluorescent components through concentration, excellent anti-counterfeiting materials with thermo-optical-coordinated dual-color fluorescence characteristics can be prepared. The application conditions are simple and repeatable, applicable to most everyday applications, and suitable for preparing various anti-counterfeiting materials or anti-counterfeiting patterns. Simultaneously, the fluorescence intensity ratio at the dual-color fluorescence peaks of the aforementioned TTHPs shows a strong dependence on temperature, and can also serve as a sensitive TRT ratio fluorescence temperature probe.

[0014] In some implementation schemes, R 1 Selected from C 1-3 Alkyl or substituted C 1-3 Alkyl; R 2 R 3 Each is independently selected from hydrogen, phenyl, C 1-3 Straight-chain or branched alkoxy groups, C 1-3 Straight-chain or branched alkyl groups, trifluoromethyl groups, fluorine, chlorine, and bromine.

[0015] In some implementations, the substituent R 2 and R 3 same.

[0016] In some implementations, when R 1 When selected from methyl, R 2 R 3 Selected from hydrogen, C 1-3 Straight-chain or branched alkoxy, trifluoromethyl, fluorine; when R 1 When selected from ethyl, R 2 R 3 Selected from hydrogen. Under this preferred structure, the tetrasubstituted tetrahydropyrimidine derivative exhibits higher sensitivity. S λrex .

[0017] In some embodiments, the tetrasubstituted tetrahydropyrimidine derivative is selected from any of the following structures: .

[0018] In some embodiments, the tetrasubstituted tetrahydropyrimidine derivative is selected from any of the following structures, with the preferred structure exhibiting higher sensitivity. S λrexThe sensitivity to temperature changes can reach up to 0.201 nm·K. -1 It is superior to existing TRT materials.

[0019] .

[0020] Furthermore, this invention claims protection for the use of the above-mentioned tetrasubstituted tetrahydropyrimidine derivatives in the preparation of biological and / or chemical temperature fluorescence sensors or probes.

[0021] Furthermore, this invention seeks protection for the use of the above-mentioned tetrasubstituted tetrahydropyrimidine derivatives in the preparation of anti-counterfeiting materials or products having temperature-range tunable fluorescence properties and / or temperature / light-induced dual fluorescence color change.

[0022] In some implementations, the anti-counterfeiting product includes one or more of the following: anti-counterfeiting labels, anti-counterfeiting images, and anti-counterfeiting test strips.

[0023] Furthermore, this invention claims protection for an anti-counterfeiting product, comprising a carrier and an anti-counterfeiting material distributed on the carrier, said anti-counterfeiting material comprising a compound having the structure shown in formula (I):

[0024] (I) Among them, R 1 Selected from C 1-5 Straight-chain or branched alkyl or substituted C 1-5 Straight-chain or branched alkyl groups; R 2 R 3 Each is independently selected from hydrogen and C. 5-6 Aromatic group, C 1-8 Straight-chain or branched alkoxy groups, C 1-8 Straight-chain or branched alkyl groups, trifluoromethyl groups, and halogens.

[0025] The temperature range required for the anti-counterfeiting properties of the compound with structure (I) is from -195°C to the light temperature range required for the anti-counterfeiting properties. The light intensity range is any temperature between C (78 K) and close to the melting point of the compound, and the light wavelength range is any wavelength between the excitation wavelength corresponding to the peak of the excitation spectrum of the compound and the wavelength corresponding to about one-tenth of the peak of the red edge of the excitation spectrum.

[0026] In some implementation schemes, R 1 Selected from C 1-3 Alkyl or substituted C 1-3 alkyl; R 2 R 3 Each is independently selected from hydrogen, phenyl, C 1-3 Straight-chain or branched alkoxy groups, C 1-3Straight-chain or branched alkyl groups, trifluoromethyl groups, fluorine, chlorine, and bromine.

[0027] In some implementations, the substituent R 2 and R 3 same.

[0028] In some implementations, when R 1 When selected from methyl; R 2 R 3 Selected from hydrogen, C 1-3 Straight-chain or branched alkoxy, trifluoromethyl, fluorine; when R 1 When selected from ethyl; R 2 R 3 Selected from hydrogen.

[0029] Compared with the prior art, the present invention has the following beneficial effects: This invention provides the application of a class of tetrasubstituted tetrahydropyrimidine derivatives in the preparation of temperature-sensitive fluorescent materials. By selecting a suitable excitation wavelength, the fluorescence intensity of the tetrasubstituted tetrahydropyrimidine derivatives can be anywhere between approximately 30 and 60 K, from 78 K to near the melting point of the compound. The fluorescence intensity changes sensitively within a temperature range of approximately °C, exhibiting a strong linear dependence on temperature. This allows for precise and sensitive measurement of temperatures across different temperature ranges, demonstrating temperature-range-tunable fluorescence characteristics. Furthermore, the tetrasubstituted tetrahydropyrimidine derivative possesses thermo-optical-size-tunable dual-color fluorescence properties. Under specific temperature and illumination (excitation wavelength), the dual-color fluorescence changes of the derivative can be synergistically controlled, providing excellent anti-counterfeiting effects. Moreover, its application is simple, repeatable, and suitable for most everyday applications. Attached Figure Description

[0030] Figure 1 This report presents three different types of fluorescent temperature probes.

[0031] Figure 2 To modify inorganic doped nanocrystalline Zn 1-x Mn x The Se / ZnCdSe size enables ratio fluorescence temperature measurement results across a limited number of different temperature ranges.

[0032] Figure 3 To achieve fluorescence temperature determination structures for three different temperature ranges by labeling three fluorescent temperature-sensitive molecules on gold nanoparticles.

[0033] Figure 4 To achieve ratio fluorescence temperature determination results across a limited number of different temperature ranges by preparing dihydrophenazine derivative (DPC) suspensions using ethanol-glycerol mixtures with different glycerol ratios (fg).

[0034] Figure 5 The molecular structure of the TRT fluorescent temperature probe THP-1 and a polycrystalline THP-1g emitting green light (emission wavelength 496 nm) are shown.

[0035] Figure 6 The red-edge excitation wavelength and fluorescence intensity of THP-1g change with temperature from 77 K to 300 K, and exhibit a linear relationship with temperature. Figure 6 a) is the excitation spectrum as a function of temperature (the gray dashed line represents the excitation spectrum measured under cyclic temperature), with an emission wavelength of 496 nm; Figure 6 b) The fluorescence intensities are respectively I F1 and I F2 The corresponding red-edge excitation wavelength λ rex Linear relationship with temperature, λ rex Sensitivity to temperature changes S λrex 0.16 nm·K -1 and 0.135 nm·K -1 ; Figure 6 c) is the red-edge excitation wavelength. λ rex They are respectively λ rex1 (420 nm) λ rex2 (430 nm) λ rex3 The fluorescence intensity corresponding to (430 nm) I F A graph showing the positive linear relationship dependence of temperature across different temperature ranges.

[0036] Figure 7 To select different excitation wavelengths, the fluorescence intensity of THP-1g can undergo sensitive changes within different temperature ranges and is positively correlated with temperature; among which... Figure 7 a) and Figure 7 b) These are the emission spectra of THP-1g under 420 nm excitation in the range of 80-120 K, and the linear relationship between the fluorescence intensity of the emission peak and temperature as a power function. Figure 7 c) and Figure 7 d) These are the emission spectra of THP-1g under 445 nm excitation in the range of 210-300 K, and the linear relationship between the fluorescence intensity of the emission peak and temperature as a power function.

[0037] Figure 8 The TRT fluorescence characteristics of compound 5f crystals were measured in the range of 78-420 K; among which, Figure 8 a represents the excitation spectrum of compound 5f crystal as a function of temperature; Figure 8 b is Figure 8 Fluorescence intensity in a I rF The red-edge excitation wavelengths corresponding to 0.1, 0.22, and 0.55. λ rex Linear relationship with temperature, and λ rex Sensitivity to temperature changes S λrex (nm·K) 1 )as well as I rF The function expression = 0.22 λ rex Maximum sensitivity to temperature variation S λrex 0.201 nm·K 1 ; Figure 8 c is the emission spectrum of the 5f crystal as a function of temperature in different temperature ranges (78-120 K, 240-300 K and 360-420 K); Figure 8 d is a graph showing the linear relationship between the peak fluorescence intensity of the emission spectrum of the 5f crystal and temperature in different temperature ranges.

[0038] Figure 9 The excitation spectrum of TTHPs-5a-5k solid as a function of temperature in the range of 210-330 K and λ rex Sensitivity to temperature changes S λrex (nm·K) 1 The emission wavelength was measured as the peak emission value of each compound.

[0039] Figure 10 The dual-color fluorescence of compound 5f powder changes with excitation wavelength at different temperatures; among which, Figure 10 The emission spectra of 5F powder at 78 K, 120 K and 180 K are converted as the excitation wavelength of the crystal changes. Figure 10 df are respectively Figure 10 The chromaticity coordinates of the AC emission spectrum.

[0040] Figure 11 The ratio of the two-color fluorescence intensity of compound 5f powder varies with temperature under different excitation wavelengths and in different temperature ranges; among which, Figure 11a is the emission spectrum of compound 5f under excitation at a wavelength of 415 nm as a function of temperature; Figure 11 b is Figure 11 The color coordinate diagram of the emission spectrum in a; Figure 11 c represents the ratio of the two-color fluorescence intensity of compound 5f under excitation at 376 nm, 394 nm, and 415 nm in different temperature ranges of 78-113 K, 185-205 K, and 250-295 K. I F435 / I F510 Linear relationship with temperature.

[0041] Figure 12 Application of compound 5f in the preparation of anti-counterfeiting materials; Figure 12 Ac was used to prepare patterns with different fluorescent colors and intensities on filter paper by controlling the loading amount of compound 5F on the filter paper. Figure 12 a) The disappearance and reappearance of the blue circle flower center in a flower pattern with green fluorescent petals and blue fluorescent circle flower center under the synergistic effect of different temperatures and excitation wavelengths; Figure 12 b represents the disappearance and reappearance of the green fluorescent leaves in the blue fluorescent rose pattern under the combined effect of a certain temperature and excitation wavelength. Figure 12 c is a form of... Figure 10 and Figure 11 Blue fluorescent petals exhibiting temperature-light synergistic regulation of dual-color fluorescence properties. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0043] Example 1: Preparation of tetrasubstituted tetrahydropyrimidine derivatives Reference Tetrahedron 2010, 66 (21), 3651-3654, Synthesis 2010, 2010 (16), 2823-2827 and Organic letters The method reported in 2007, (21), 4111-4113, was used to prepare tetrasubstituted tetrahydropyrimidine derivatives 5a~5k.

[0044] The following reaction formulas and Table 1 show the multi-component reaction synthesis formulas, molecular structures, maximum emission wavelength λem of the solid, and the sensitivity (S) of the red-edge excitation wavelength reflecting the temperature-tunable (TRT) fluorescence properties as a function of temperature.λrex ), and the melting point of the compound.

[0045]

[0046] Table 1

[0047] a Maximum emission wavelength; b Absolute fluorescence quantum rate determined by integrating sphere method; c Sensitivity of red-edge excitation wavelength to temperature variation.

[0048] All compounds in the table were synthesized according to the multi-component reaction synthesis method reported by the inventors. Tetrahedron 2010, 66 (21), 3651-3654). The properties and structural characteristics of the tetrasubstituted tetrahydropyrimidine derivatives 5a and 5d-5k have been disclosed in the aforementioned literature, while the properties and structural characteristics of TTHP-5b and TTHP-5c are shown below: TTHP-5b, Dimethyl 1,3-bis(4-biphenyl)-1,2,3,6-tetrahydropyrimidine-4,5-dicarboxylate(5b)78%yield,yellow crystal, Mp: 150.2–150.6 C; IR (KBr) ν max =3031, 1742, 1698, 1636, 1607, 1521, 1258, 763 cm -1 ; 1 H NMR (400 MHz, Chloroform- d ) δ = 7.61 – 7.42 (m, 11H), 7.42 – 7.27 (m, 3H), 7.17 – 7.07 (m,2H), 7.06 – 6.94 (m, 2H), 5.03 (s, 2H), 4.36 (s, 2H), 3.80 (s, 3H), 3.66 (s,3H); 13 C NMR (101 MHz, Chloroform- d ) δ= 166.00 , 164.57 , 147.36 , 146.28 ,142.70 , 140.52 , 139.88 , 139.13 , 133.78 , 128.82 , 128.72 , 128.70 ,127.89 , 127.85 , 127.70 , 127.49 , 127.31 , 127.02 , 126.89 , 126.87 ,126.84 , 126.67 , 126.53 , 124.92 , 122.92 , 119.43 , 117.79 , 100.95 , 68.46, 52.61 , 51.60 , 48.21 , 47.56; HRMS (ESI) calculated for C 25 H 23 NO4[M+H] + :505.2100; found: 505.2065. TTHP-5c, Dimethyl 1,3-bis(4-ethoxyphenyl)-1,2,3,6-tetrahydropyrimidine-4,5-dicarboxylate (5c)60%yield, white solid, Mp: 133.4–134.0 ℃; IR (KBr) ν max = 2980, 1744, 1696, 1577, 1508, 1477, 1435, 765 cm -1 ; 1 HNMR (400 MHz, Chloroform- d ) δ = 7.05 – 6.65 (m, 8H), 4.79 (s, 2H), 4.19 (s,2H), 4.06 – 3.90 (m, 4H), 3.74 (s, 3H), 3.58 (s, 3H), 1.47 – 1.25 (m, 6H); 13 CNMR (101 MHz, Chloroform- d ) δ= 166.23 , 164.52 , 157.57 , 153.98 , 142.13 ,135.84 , 127.30 , 120.25 , 115.12 , 114.69 , 97.19 , 70.61 , 63.67 , 63.55 ,52.35 , 51.31 , 47.64 , 14.84 , 14.71; HRMS (ESI) calculated for C 25 H 23 NO4[M+H] + : 441.2000; found: 441.1953. Test Example 1: TRT Characterization Test of Tetrasubstituted Tetrahydropyrimidine Derivatives (1) The temperature was controlled from 420 to 78 K using an Oxford Optistat DN2 liquid nitrogen cryostat, and the excitation spectrum of the tetrasubstituted tetrahydropyrimidine TTHP-5f prepared in the example was accurately determined using an FLS980 fluorescence spectrometer at the maximum emission wavelength of 453 nm. Figure 8 a) The red-edge excitation wavelength λ of the excitation spectrum rex It has a positive linear relationship with temperature. Figure 8 b), λ rex Sensitivity S as a function of temperature λrex It is a key parameter for evaluating temperature-tunable (TRT) fluorescence properties. Figure 8 a and Figure 8 As can be seen from b, by selecting an appropriate excitation wavelength, the fluorescence intensity of the compound can undergo sensitive changes in intensity within different temperature ranges, thus serving as a unique TRT fluorescence temperature probe.

[0049] Figure 8 c shows three examples of temperature measurements within different temperature ranges. An Oxford Optistat DN2 liquid nitrogen cryostat was used for temperature control, with 380 nm, 407 nm, and 428 nm selected as excitation wavelengths. An FLS980 fluorescence spectrometer was used to accurately measure the emission spectra at different temperatures within the ranges of 78-120 K, 240-300 K, and 360-420 K. It can be seen that the fluorescence intensity of the compound changes sensitively across different temperature ranges. Furthermore, the peak fluorescence intensity of the compound's emission spectra in different temperature ranges shows a strong linear dependence on temperature. Figure 8 d), therefore, TTHP-5f can be used as a sensitive fluorescence intensity change temperature probe over different temperature ranges. TTHP-5a to 5e and TTHP-5g to 5k have the same properties as TTHP-5f.

[0050] (2) From 330 to 210 K, the excitation spectra of each compound at different temperatures were measured using the peak emission wavelength. Figure 9 The data in the figure represent the sensitivity S of the red-edge excitation wavelength λrex of the excitation spectrum as a function of temperature. λrex nm·K –1 As shown in the figure, TTHPs with different molecular structures have different S λrex value.

[0051] Test Example 2: Thermo-optic Synergistic Two-Color Fluorescence Conversion Characteristics of Tetrasubstituted Tetrahydropyrimidine Derivatives (1) By changing the excitation wavelength, TTHP-5f powder can undergo sensitive switching between blue fluorescence (453 nm) and green fluorescence (510 nm) at different temperatures. For example, the emission wavelength λ of the compound changes from excitation wavelengths of 365 nm to 380 nm, from 370 nm to 394 nm, and from 385 nm to 400 nm. em It can be transformed from 453 nm to approximately 510 nm at temperatures of 78 K, 120 K, and 180 K, respectively. Figure 10 (ac), meaning the fluorescent color changes from blue to green ( Figure 10 (de color chart). This two-color fluorescence conversion is reversible and can be used to prepare anti-counterfeiting maps.

[0052] (2) By selecting a suitable excitation wavelength, the ratio (RF453 / 510) of the two-color fluorescence intensity of TTHP-5f powder can change with temperature in different temperature ranges, and has a good linear dependence on temperature. It can be used as a ratiometric fluorescence temperature probe, and also for preparing anti-counterfeiting maps. For example, with excitation wavelengths of 376 nm, 394 nm, and 415 nm, the compound can exhibit sensitive two-color fluorescence changes in different temperature ranges of 78-113 K, 185-205 K, and 250-295 K, respectively. Figure 11 a and 11b are the emission spectra and color charts of the two-color fluorescence changes at 250-295 K, respectively. The ratio of the two-color fluorescence intensities RF453 / 510 has a good linear dependence on temperature. Figure 11 c). (3) Anti-counterfeiting patterns with different fluorescent colors, different fluorescence intensities, and temperature and excitation wavelength synergistically controlled dual-color fluorescence characteristics of TTHP-5f can be prepared by utilizing the size-dependent dual-color fluorescence properties. For example Figure 12As shown in Figure ac, by controlling the amount of TTHP-5f loaded onto the filter paper, patterns with different fluorescent colors, fluorescence intensities, and thermo-optical synergistic modulation characteristics can be prepared by dropping TTHP-5f onto the filter paper. These patterns can only be displayed and changed under specific temperatures and excitation wavelengths. For example, a flower pattern with green fluorescent petals and a blue fluorescent ring in the center can only have the blue fluorescent ring disappear and appear under certain conditions. Figure 12 a), while the leaves are green fluorescent and the flower is bright blue fluorescent, forming a rose pattern. The green leaves exhibit changes in light and dark under certain conditions. Figure 12 b). TTHP-5a to 5e and TTHP-5g to 5k have the same properties as TTHP-5f.

[0053] The foregoing examples are merely illustrative, used to explain some features of the method described in this invention. The appended claims are intended to claim the broadest possible scope, and the embodiments presented herein are demonstrated by the applicant's actual experimental results. Therefore, the applicant intends that the appended claims are not limited by the selection of examples illustrating the features of the invention. Some numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. The application of a class of tetrasubstituted tetrahydropyrimidine derivatives in the preparation of temperature-sensitive fluorescent materials, characterized in that, The tetrasubstituted tetrahydropyrimidine derivative has the structure shown in formula (I): （I） Among them, R 1 Selected from C 1-5 Straight-chain or branched alkyl groups; R 2 R 3 Each is independently selected from hydrogen and C. 5-6 Aromatic group, C 1-8 Straight-chain or branched alkoxy groups, C 1-8 Straight-chain or branched alkyl groups, trifluoromethyl groups, and halogens.

2. The application according to claim 1, characterized in that, R 1 Selected from C 1-3 alkyl; R 2 R 3 Each is independently selected from hydrogen, phenyl, C 1-3 Straight-chain or branched alkoxy groups, C 1-3 Straight-chain or branched alkyl groups, trifluoromethyl groups, fluorine, chlorine, and bromine.

3. The application according to claim 2, characterized in that, Substituent R 2 and R 3 same.

4. The application according to claim 3, characterized in that, When R 1 When it is methyl, R 2 R 3 Selected from hydrogen, C 1-3 Straight-chain or branched alkoxy, trifluoromethyl, fluorine; when R 1 When selected from ethyl, R 2 R 3 Selected from hydrogen.

5. The application according to claim 1, characterized in that, The tetrasubstituted tetrahydropyrimidine derivative is selected from any of the following structures: 。 6. The application according to claim 5, characterized in that, The tetrasubstituted tetrahydropyrimidine derivative is selected from any of the following structures: 。 7. The application according to claim 1, characterized in that, Application of the tetrasubstituted tetrahydropyrimidine derivatives in the preparation of biological and / or chemical temperature fluorescence sensors or probes.

8. The application according to claim 1, characterized in that, Application of the tetrasubstituted tetrahydropyrimidine derivatives in the preparation of anti-counterfeiting materials or products with temperature-range tunable fluorescence properties and / or temperature / light-induced dual fluorescence color change.

9. The application according to claim 8, characterized in that, The anti-counterfeiting product is one or more of the following: anti-counterfeiting label, anti-counterfeiting image, and anti-counterfeiting test paper.

10. An anti-counterfeiting product, characterized in that, Includes a carrier and anti-counterfeiting materials distributed on the carrier, said anti-counterfeiting materials comprising compounds having the structure shown in formula (I): （I） Among them, R 1 Selected from C 1-5 Straight-chain or branched alkyl groups; R 2 R 3 Each is independently selected from hydrogen and C. 5-6 Aromatic group, C 1-8 Straight-chain or branched alkoxy groups, C 1-8 Straight-chain or branched alkyl groups, trifluoromethyl groups, and halogens.

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