Method for the preparation of a host-guest doped of a methyl phthalate derivative and its application in encryption and iron (iii) detection

Abstract

The application discloses a preparation method of host-guest doped methyl phthalate derivative and application of the host-guest doped methyl phthalate derivative in encryption and Fe(III) detection. The preparation method comprises the following steps: adding benzaldehyde, malononitrile, triethylamine, dimethyl butyne diacid and anhydrous dichloromethane into a reaction bottle, reacting at room temperature for 2 hours, and then obtaining the methyl phthalate derivative through separation and purification. The purified methyl phthalate derivative is doped with polymethyl methacrylate or polyvinyl alcohol at a weight ratio of 1:100, and then the doped material is uniformly mixed through dissolution, and the solvent is removed through heating at different temperatures to obtain a host-guest doped material with a double emission characteristic of thermal activation delayed fluorescence and room temperature phosphorescence. By using different phosphorescence emission wavelengths and afterglow life of the doped system, a high-level anti-counterfeiting pattern is constructed, and visual detection of Fe 3+ is realized.

Description

Technical Field

[0001] This invention belongs to the field of organic functional materials, specifically relating to the preparation of a small molecule of methyl phthalate and its thermal delayed fluorescence, room temperature phosphorescence, anti-counterfeiting properties, and iron (III) ion detection performance in the doping system. Background Technology

[0002] Organic dual-state emission (DSE) materials, exhibiting both thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP), have attracted widespread attention due to their potential in advanced optoelectronic applications such as anti-counterfeiting, sensing, and information encryption. DSE materials with long afterglow properties offer unique advantages for time-resolved visual inspection and dynamic information display. However, achieving efficient and tunable afterglow in purely organic systems remains challenging due to factors including non-radiative decay, triplet exciton quenching caused by molecular motion, and sensitivity to oxygen. Host-guest doping strategies, which immobilize phosphors in a rigid polymer matrix, suppress vibrational dissipation, and shield oxygen, are readily available for large-area fabrication and rapid screening of host and guest materials, and have become an efficient method for constructing organic long-afterglow materials. Although host-guest doping has made significant progress in enhancing afterglow performance, there is still an urgent need for simple and scalable methods to further enhance host-guest interactions to improve afterglow performance and expand practical applications. Furthermore, most current host-guest doping methods are physical doping, where dopant molecules may aggregate or migrate due to thermal motion or solvent erosion, leading to phosphorescence quenching or performance degradation and insufficient long-term stability. In contrast, covalent grafting between host and guest molecules through chemical reactions can form strong chemical bonds, "anchoring" phosphorescent molecules to the polymer chain and effectively preventing molecular migration and leakage.

[0003] Although DSE materials achieve the coexistence of TADF and RTP, the short TADF lifetime in most DSE materials makes it difficult to generate significant time-dependent dynamic afterglow. Extending the TADF lifetime and controlling the intensity ratio between TADF and RTP to achieve a dynamic afterglow lasting several seconds, enabling more complex information encryption, remains a challenge. Furthermore, current applications of DSE materials are highly focused on anti-counterfeiting and information encryption. Exploration of applications beyond anti-counterfeiting, such as environmental monitoring (other metal ions, pollutants), bioimaging, real-time monitoring of health indicators (e.g., blood glucose), and smart response devices, is severely lacking. Most research remains focused on demonstrating the photophysical properties of the materials themselves, failing to deeply integrate their unique dual-state emission and time-resolved characteristics with broader practical needs to achieve diversified functional integration. In summary, future research needs to focus on designing novel DSE molecules to optimize photophysical parameters, developing more refined matrix regulation strategies, and actively exploring innovative applications in interdisciplinary fields such as sensing and biology, thereby fully unleashing the enormous potential of this type of smart material. Summary of the Invention

[0004] The purpose of this invention is to enhance the interaction between host and guest molecules, induce transesterification between phosphor and polyvinyl alcohol, regulate the intensity ratio of TADF and RTP, increase the difficulty of counterfeiting anti-counterfeiting materials, and achieve the visual detection of metal ions by molecular design (introducing multifunctional groups such as ester, cyano, and amino groups), host-guest doping, and thermal annealing temperature.

[0005] The invention involves adding benzaldehyde, malononitrile, triethylamine, dimethyl butyryneidate, and anhydrous dichloromethane to a reaction flask and reacting at room temperature for 2 hours. The resulting methyl phthalate derivative is then purified. The purified methyl phthalate small molecules, polymethyl methacrylate / polyvinyl alcohol, and Fe... 3+ A series of host-guest doping systems were formed according to a weight ratio of 1:100:0 / 1 / 5 / 10. Then, utilizing the different afterglow colors and lifetimes of these doping systems, advanced anti-counterfeiting patterns were constructed to achieve Fe... 3+ Visual detection.

[0006] The objective of this invention is achieved through the following technical solution.

[0007] The synthesis method of small molecule methyl phthalate includes the following preparation process: Benzaldehyde, malononitrile, triethylamine, dimethyl butyryne dimethyl ester and anhydrous dichloromethane were added to a reaction vessel under atmospheric conditions. The mixture was stirred and reacted at room temperature for 2 hours. The crude product was purified by column chromatography to obtain the methyl phthalate small molecule.

[0008] Furthermore, the preparation equation for small molecule methyl phthalate (Me-ADBD) is shown below:

[0009] In the above preparation method, the molar ratio of benzaldehyde, malononitrile, triethylamine, and dimethyl butyryne diacetate is 1: 2:0.1:1.

[0010] In the above preparation method, the organic solvent is anhydrous dichloromethane, and 6.5 mL of anhydrous dichloromethane is used for 1 mol of benzaldehyde.

[0011] The principle of this invention is as follows: By introducing ester, cyano, and amino functional groups into a phosphor, a donor-acceptor structure is formed (the benzene ring is the electron donor, and the dicyanoaniline unit is the electron acceptor), endowing the molecule with significant intramolecular charge transfer (ICT) properties. This structure is beneficial for narrowing the singlet-triplet band gap (ΔE). STThe process involves enhancing spin-orbit coupling to achieve DSE emission with coexistence of TADF and RTP. Phosphors are then doped into rigid polymer matrices such as polymethyl methacrylate (PMMA) or polyvinyl alcohol (PVA). The hydrogen bonding network or hydrophobic environment of the matrix suppresses molecular vibrational and non-radiative decay, while isolating oxygen to provide a stable hypoxic microenvironment for triplet excitons, thus extending the lifetimes of TADF and RTP. Simultaneously, different host matrices are used to modulate the intensity ratio of TADF and RTP, forming dynamic afterglow and constructing complex information encryption. Subsequently, thermal annealing initiates an ester exchange reaction between the phosphor ester groups and PVA hydroxyl groups, forming covalent bonds, further rigidifying the molecule, reducing energy dissipation, and significantly improving afterglow lifetime. Multiple coordination sites of the phosphor (cyano, amino, ester groups) specifically bind to metal ions (such as Fe³⁺), modulating the afterglow lifetime through electron energy transfer or exciton quenching mechanisms, enabling visual detection.

[0012] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The afterglow performance is significantly improved and adjustable: Existing DSE materials often have short phosphorescence lifetimes due to molecular motion or oxygen quenching. However, this invention extends the afterglow lifetime to 10 s (after heat treatment of the PVA doped film at 150℃) through host-guest doping and heat treatment, and achieves dynamic adjustment of the TADF / RTP intensity ratio and color. This provides a longer observation window and color variability for time-resolved encryption and dynamic display, surpassing traditional static anti-counterfeiting materials.

[0013] (2) Simple and efficient matrix engineering: This invention achieves performance optimization by inducing covalent anchoring of phosphors to a PVA matrix solely through heat treatment, without the need for additional crosslinking agents. This method is simple, low-cost, and easily scalable, avoiding the dependence on harsh conditions inherent in traditional methods, improving the water resistance of the film, and expanding the practical application range of the material.

[0014] (3) Multifunctional integration and extended applications: Existing DSE materials are mainly limited to anti-counterfeiting. This invention is the first to use phosphors for visual detection of Fe³⁺, achieving semi-quantitative analysis without instruments through the afterglow quenching effect. This broadens the application of DSE materials in the field of ion detection. Attached Figure Description

[0015] Figure 1 , Figure 2 and Figure 3 These are the proton, carbon, and mass spectra of the target product Me-ADBD obtained in Example 1; Figure 4 (ab) are the target product Me-ADBD obtained in Example 1 in different solvents (10⁻ 5Normalized UV-Vis absorption and fluorescence emission spectra of Me-ADBD in a glassy tetrahydrofuran solution (10⁻⁻¹) at 77 K. 5 Fluorescence and phosphorescence spectra of Me-ADBD in glassy dimethyl sulfoxide solution (10⁻ 5 Variable temperature phosphorescence spectrum in M).

[0016] Figure 5 (a) Photographs of Me-ADBD in a PMMA matrix with doping concentrations of 0.1%, 1%, and 5% (excitation wavelength λ). ex = 365 nm). (b) Normalized fluorescence and phosphorescence spectra of 1% Me-ADBD@PMMA film. (c) Temperature-varying phosphorescence spectrum of 1% Me-ADBD@PMMA film. (d) Phosphorescence lifetime decay curves of 1% Me-ADBD@PMMA film at 441 nm and 522 nm.

[0017] Figure 6 (a) Photographs of Me-ADBD in a PVA matrix with doping concentrations of 0.1%, 1%, and 5% (excitation wavelength λ). ex = 365 nm). (b) Normalized fluorescence and phosphorescence spectra of 1% Me-ADBD@PVA film. (c) Temperature-varying phosphorescence spectra of 1% Me-ADBD@PVA film. (d) Phosphorescence lifetime decay curves of 1% Me-ADBD@PVA film at 437 nm and 493 nm.

[0018] Figure 7 (a) Photographs of 1% Me-ADBD@PVA films after heat treatment at different temperatures (60-180°C) for 30 minutes (excitation wavelength λex = 365 nm). (b) Normalized fluorescence and phosphorescence spectra of 1% Me-ADBD@PVA films after heat treatment at 150°C, and (c) their phosphorescence lifetime decay curves. (de) Infrared spectra of 1% Me-ADBD@PVA films before and after heat treatment at 150°C.

[0019] Figure 8 (a) Digital photographs of 1% Me-ADBD@PVA films before and after different perchlorate treatments; (b) Digital photographs of 1% Me-ADBD@PVA films before and after different equivalents of ferric perchlorate treatment.

[0020] Figure 9(ab) Anti-counterfeiting photographs prepared from 1% Me-ADBD@PMMA film and 1% Me-ADBD@PVA film under environmental conditions; (c) Information encryption achieved using 0.1% Me-ADBD@PMMA, 5% Me-ADBD@PMMA, 1% Me-ADBD@PVA and 1% t-Me-ADBD@PVA film.

[0021] Figure 10 (a) Photograph of a 1%Me-ADBD@PVA film dissolved in 2 mL of deionized water. (b) Photograph of a cross-linked 1%Me-ADBD@PVA film of the same size as the 1%Me-ADBD@PVA film, heat-treated at 150°C, dissolved in 2 mL of deionized water. (c) Photograph of a 1%Me-ADBD@PVA film dissolved in 2 mL of deionized water for 5 hours. (d) Photograph of a cross-linked 1%Me-ADBD@PVA film (treated at 150°C) dissolved in 2 mL of deionized water for 5 hours. Detailed Implementation

[0022] The present invention will be further described below through specific embodiments, but the scope of protection and implementation of the present invention are not limited thereto.

[0023] Example 1 Benzaldehyde (1 mmol), malononitrile (2 mmol), and triethylamine (0.1 mmol) were mixed in anhydrous dichloromethane (5 mL). Then, a solution of dimethyl acetyl dicarboxylate (1 mmol) in anhydrous dichloromethane (1.5 mL) was slowly added dropwise to the reaction mixture at room temperature, and the mixture was stirred continuously at ambient temperature for 2 hours. The product was purified by column chromatography using petroleum ether / ethyl acetate (4:1 v / v) as the eluent. After solvent removal, colorless crystals were obtained in 65% yield with a melting point of 180 °C.

[0024] Example 2 Preparation of PMMA thin films (taking 1% Me-ADBD@PMMA doped thin films as an example): A mixture of PMMA (200 mg) and Me-ADBD (2 mg) powders was dissolved in dichloromethane (4 mL) and stirred at room temperature until completely dissolved. The solution was then poured into a pre-made mold and dried at room temperature for 30 minutes to obtain a 1% doped thin film.

[0025] Example 3 Preparation of PVA films (taking 1% Me-ADBD@PVA doped films as an example): PVA (2 g) was dissolved in deionized water (40 mL), heated and stirred at 95°C for 1 hour, and filtered to obtain an aqueous PVA solution for later use. Me-ADBD powder (2 mg) was dissolved in tetrahydrofuran (3 mL) and dissolved by sonication at room temperature. Then, the tetrahydrofuran solution of Me-ADBD (3 mL) was mixed with the aqueous PVA solution (4 mL), sonicated for 2 hours, and allowed to stand for 1 hour. Finally, the mixed solution was poured into a mold and dried at 60°C for 6 hours to obtain a 1% Me-ADBD@PVA film.

[0026] Example 4 Preparation of PVA crosslinked films: Five identical 1% Me-ADBD@PVA films were prepared according to Example 3 above. The dried films were then heat-treated in ovens at 60°C, 90°C, 120°C, 150°C and 180°C for 30 minutes to obtain the crosslinked film with the best final performance (heat treatment at 150°C).

[0027] Example 5 Me-ADBD / PVA / Metal Ions (M n ⁺) Thin film preparation: First, dissolve 0.2 g of PVA film in 2 mL of deionized water and stir at 85°C for 1 hour; weigh 2 mg of Me-ADBD compound and dissolve it in 2 mL of THF solution, sonicating until completely dissolved; weigh the corresponding metal compound according to the molar ratio of metal ions (a series of perchlorates) to Me-ADBD of 10:1, dissolve it in deionized water and sonicate to dissolve it. Mix the above three solutions, sonicate for 2 hours, let stand for 1 hour, pour into a mold and dry at 60°C for 6 hours to obtain a transparent film.

[0028] Example 6 Anti-counterfeiting and encryption: The peacock's wings are made of 1% Me-ADBD@PMMA film, while its body is made of 1% Me-ADBD@PVA film. When the UV light is on: A peacock with its tail feathers fully extended can be observed. When the UV light is off: The peacock's body (PVA film) emits a blue afterglow, and the wings (PMMA film) emit a green afterglow. Evolution over time: The tail feathers gradually retract, closing completely after 6 seconds. Finally, the peacock's body disappears completely after 7 seconds. The branches and twigs are made of 1% Me-ADBD@PMMA film. The chameleon itself is made of 1% Me-ADBD@PVA film. Under 365 nm UV light: The entire pattern emits a uniform blue light, and the chameleon also appears blue. When the UV light is off: The branches and leaves turn green, and the chameleon begins to gradually change color over time, slowly transitioning to green. Finally, as the glow from the branches and leaves diminishes, the chameleon also slowly disappears. Pattern composition: The pentagram, equilateral triangle, square, and circle are fabricated from 5% Me-ADBD@PMMA, 0.1% Me-ADBD@PMMA, 1% Me-ADBD@PVA, and 1% t-Me-ADBD@PVA (PVA films heat-treated at 150°C), respectively. Under 365 nm UV light, all patterns collectively display the word "WANT". For the first 3 seconds after the UV light is turned off, the "WANT" image continues to appear, creating a decoy effect. From the 4th second onwards, the afterglow dynamically evolves: over time, it successively transforms into "LIKE", "GOGO", and "HHHH". These characters collectively convey the core message: "Follow your heart, give it your all, and live happily!" The structural characterization data of the target product Me-ADBD are shown below: 1 H NMR (500 MHz, CDCl3) δ 7.50 – 7.46 (m, 3H), 7.33 – 7.29 (m, 2H), 5.60 (s, 2H), 3.99 (d, J = 1.9 Hz, 3H), 3.50 (d, J = 1.9 Hz, 3H). 13 C NMR (126MHz, CDCl3) δ 165.76, 164.35, 152.25, 150.09, 138.63, 135.34, 129.88, 128.71,128.06, 123.79, 114.17, 113.78, 100.53, 95.25, 55.57, 54.53, 53.76, 52.70.HRMS (MALDI-TOF): m / z 358.0801 [[M +Na] + , Calculated value 358.0798]. Based on the above characterization data, the structure of the target compound is inferred as follows:

Claims

1. A method for preparing a host-guest doped methyl phthalate derivative, characterized in that, The material exhibiting dual emission characteristics of thermally activated delayed fluorescence and room-temperature phosphorescence is a host-guest doping system of methyl phthalate (MTBF) and polymethyl methacrylate (PMMA) or polyvinyl alcohol (PVA). The doping weight ratio of 3,5-dicyanopyridine (DPBF) to PMMA or PVA is 1:

100. The mixture is dissolved in CH2Cl2 or THF-H2O, ultrasonically mixed, and then the solvent is removed by heating to 60-150°C to obtain the doped system. This system is then applied to anti-counterfeiting and Fe... 3+ Visual detection revealed the following structural formula for the small molecule of methyl phthalate: .

2. The application of the doping system according to claim 1 in anti-counterfeiting, characterized in that: By utilizing polymethyl methacrylate and polyvinyl alcohol, and different doping systems constructed at different processing temperatures, different fluorescence and afterglow colors and afterglow lifetimes are generated, and time-resolved patterns are constructed.

3. A doping system according to claim 1 in Fe 3+ Its application in visual detection is characterized by: Small molecule methyl phthalate, polyvinyl alcohol, Fe 3+ Based on a doping system formed in a ratio of 1:100:0 / 1 / 5 / 10, afterglow at 7s, 4s, 2s, and 1s is presented, respectively, to achieve Fe... 3+ Visual detection.

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