P-xylylene-bis (4-amino-3-methylphenol) Schiff base single crystal and preparation method thereof

Abstract

The invention belongs to the field of synthesis and preparation of Schiff base single crystals, and particularly relates to a p-xylylene-bis (4-amino-3-methylphenol) Schiff base single crystal and a preparation method thereof. The p-xylylene-bis (4-amino-3-methylphenol) Schiff base single crystal is a Schiff base formed by condensation of one molecule of p-phthalaldehyde and two molecules of 4-amino-3-methylphenol, and is a completely symmetrical bis-Schiff base, and the molecular structural formula of the p-xylylene-bis (4-amino-3-methylphenol) Schiff base single crystal is C22H20N2O2. The compound has good optical performance, can be used as a reaction intermediate product for synthesis of epoxy resin, and has important significance for research of high-thermal-conductivity epoxy resin; and the new single crystal can show excellent photoelectric properties, thermal stability or magnetism, and promotes the innovation of photoelectric devices or spintronics devices.

Description

Technical Field

[0001] This invention belongs to the field of synthesis and preparation of Schiff base single crystals, specifically relating to a novel method for preparing terephthalimide-bis(4-amino-3-methylphenol) Schiff base single crystals. Background Technology

[0002] Schiff bases are a class of imine compounds formed by the condensation reaction of primary amines with aldehydes or ketones, with the general formula R1R2C=N-R3 (where R3 is an aryl or alkyl group). Since their first report by the German chemist Hugo Schiff in 1864, Schiff bases have become an important subject of study in the field of chemistry due to their unique structure and diverse properties.

[0003] The synthesis of Schiff bases is typically achieved through the condensation reaction of aldehydes / ketones with primary amines, requiring acidic or neutral conditions and often using anhydrous solvents (such as methanol or ethanol) or azeotropic dehydration. In recent years, green synthesis techniques have been developed, such as microwave-assisted synthesis, solvent-free grinding, or catalytic systems (such as Lewis acids), to improve efficiency and yield. Furthermore, there has been extensive research and exploration into catalytic systems such as metal-organic frameworks (MOFs).

[0004] Solid-state synthetic materials often appear in polycrystalline or amorphous forms. The emergence of single crystals reveals intramolecular and intermolecular interactions (such as hydrogen bonds, π-π stacking, van der Waals forces, and coordination bonds), providing a foundation for understanding the chemical properties and reactivity of substances. This invention successfully synthesizes Schiff base single crystals by reacting terephthalaldehyde with 4-amino-3-methylphenol. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a novel terephthalimide-bis(4-amino-3-methylphenol) Schiff base single crystal and its preparation method. The Schiff base single crystal compound synthesized by this invention provides data support and theoretical configuration for chemical engineering and related materials research, and promotes the theoretical research development and practical production application in related industries.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first technical objective of this invention is to provide a novel Schiff base single crystal, namely, terephthaloyl-bis(4-amino-3-methylphenol), with the molecular structural formula: C 22 H 20 The molecular structure of N2O2 crystal monomers is as follows:

[0008]

[0009] Specifically, the chemical formula of the terephthalimide-bis(4-amino-3-methylphenol) Schiff base single crystal TAM is:

[0010] C 22 H 20 N₂O₂, with a molar mass M = 344.40 g / mol, belongs to the orthorhombic crystal system, and the crystal size for the diffraction experiment is 0.12 × 0.1 × 0.08 mm. 3 The space group is Pbca, Z = 8, the number of electrons in the unit cell is F = 1456.0, and the R1 value for the observable diffraction point is 0.0363.

[0011] The second technical objective of this invention is to provide a method for preparing single crystals of terephthalimide-bis(4-amino-3-methylphenol) Schiff base as described above, the method specifically comprising the following steps:

[0012] Terephthalaldehyde and 4-amino-m-methylphenol were dissolved in ethanol to form mixture A, and zinc chloride was added to ethanol to form mixture B. Mixture B was added to mixture A, and the mixture was purged with argon gas for reaction. After the reaction was completed, the mixture was refrigerated and washed successively with methanol and ultrapure water. Waste liquid was removed by vacuum filtration. Subsequently, the mixture was vacuum dried and a yellow Schiff base single crystal, namely the terephthalimide-bis(4-amino-3-methylphenol) Schiff base single crystal, was obtained by gas-phase diffusion method.

[0013] Furthermore, in solution A, the molar ratio of terephthalaldehyde, 4-amino-m-methylphenol, and ethanol is 0.05 mol: 0.105 mol: 90 mL; and in solution B, the molar ratio of zinc chloride to ethanol is 0.0025 mol: 10 mL.

[0014] Furthermore, the reaction temperature was 30℃, the reaction time was 4 hours, the refrigeration time was 12 hours, and the vacuum drying temperature was 50℃ for 12 hours.

[0015] Furthermore, the method for preparing single crystals by vapor-phase diffusion infiltration is operated as follows:

[0016] Dissolve 2 mg of sample in 1 ml of tetrahydrofuran, transfer the solution to a 2 ml glass bottle, slowly add 0.5 ml of chloroform, then transfer the 2 ml glass bottle to a 20 ml glass bottle containing 5 ml of n-hexane solution, tighten the cap, and let stand for 1 day.

[0017] Specifically, the preparation steps of the above-mentioned terephthalimide-bis(4-amino-3-methylphenol) Schiff base single crystal are as follows:

[0018] In a 250 mL three-necked flask, 0.05 mol of terephthalaldehyde, 0.105 mol of 4-amino-m-methylphenol, and 90 mL of ethanol were added sequentially. 0.0025 mol of ZnCl₂ was dissolved in 10 mL of ethanol and added to the flask all at once. Argon gas was introduced and stirring was initiated at 30 °C for 4 hours. After stirring, the flask was refrigerated for 12 hours. The sample was then washed sequentially with methanol and ultrapure water, and waste liquid was removed by vacuum filtration. The sample was vacuum dried at 50℃ for 12 hours, and then single crystals were prepared by vapor-phase diffusion percolation. 2 mg of sample was dissolved in 1 ml of tetrahydrofuran (THF), and the solution was transferred to a 2 ml glass bottle. 0.5 ml of chloroform (CHCl3) was slowly added, and then the 2 ml glass bottle was transferred to a 20 ml glass bottle containing 5 ml of n-hexane solution. The bottle cap was tightened, and the bottle was left to stand for 1 day to obtain yellow Schiff base single crystals. The prepared Schiff base single crystals were labeled as TAM.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] This invention designs and synthesizes a novel terephthalimide-bis(4-amino-3-methylphenol) Schiff base single crystal. This compound has good thermal conductivity and can be used as a reaction intermediate in the synthesis of epoxy resins, which is of great significance for the research of high thermal conductivity epoxy resins.

[0021] (1) Breakthroughs in materials science

[0022] Schiff bases, due to their unique conjugated structure and coordination ability, are frequently used in the design of optical, magnetic, and semiconductor materials. New single crystals can exhibit excellent photoelectric properties, thermal stability, or magnetic properties, driving innovation in optoelectronic devices and spintronic devices. Referring to current research on Schiff base single crystals, Ghosh et al. first reported on elastic organic crystals of Schiff bases under mechanical stress in 2015, providing 17 Schiff base single crystals from E1 to E17. Due to the properties of Schiff bases, these single crystals all exhibit good photoelectric properties and show promising performance in optoelectronic devices such as optical waveguides and resonators.

[0023] (2) Advancement of basic theoretical research

[0024] The structural data from the new single crystals can provide a benchmark for quantum chemical calculations or molecular dynamics simulations, verify the accuracy of theoretical models, and promote a deeper understanding of intermolecular forces (such as coordination bonds and hydrogen bond networks).

[0025] (3) Potential value in industrial applications

[0026] The emergence of this single-crystal preparation method can promote its large-scale production and accelerate the transformation from laboratory to practical application. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 This is the synthetic route for single crystals of the Schiff base of the compound p-phenylenedimethylene-bis(4-amino-3-methylphenol).

[0029] Figure 2 It is the crystalline monomer molecular structure of the compound terephthalimide-bis(4-amino-3-methylphenol) Schiff base single crystal (TAM).

[0030] Figure 3 It is a three-dimensional stacked structure of a single crystal (TAM) of the compound terephthalimide-bis(4-amino-3-methylphenol) Schiff base.

[0031] Figure 4 It is the UV-Vis absorption spectrum of a single crystal of the compound p-phenylenedimethylene-bis(4-amino-3-methylphenol) Schiff base.

[0032] Figure 5 This is the infrared spectrum of single-crystal TAM of the compound p-phenylenedimethylene-bis(4-amino-3-methylphenol) Schiff base.

[0033] Figure 6 It is the 1H NMR spectrum of a single crystal TAM of the compound p-phenylenedimethyl-bis(4-amino-3-methylphenol) Schiff base.

[0034] Figure 7 This is the carbon NMR spectrum of a single crystal TAM of terephthalimide-bis(4-amino-3-methylphenol) Schiff base. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0037] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0038] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0039] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0040] This invention discloses a novel method for preparing single crystals of terephthalimide-bis(4-amino-3-methylphenol) Schiff base.

[0041] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0042] Example 1

[0043] like Figure 1 As shown, a novel method for preparing single crystals of terephthalimide-bis(4-amino-3-methylphenol) Schiff base specifically includes the following steps:

[0044] Place a 250 ml three-necked flask on a rack, and add 0.05 mol of terephthalaldehyde, 0.105 mol of 4-amino-3-methylphenol, and 90 ml of ethanol sequentially. Dissolve 0.0025 mol of ZnCl2 in 10 ml of ethanol and add it to the three-necked flask all at once. Purge with argon gas and stir at 30°C for 4 hours. After stirring, place the three-necked flask in the refrigerator's crisper compartment (8°C) for 12 hours. After refrigeration, wash the sample sequentially with methanol and ultrapure water, and remove the waste liquid by vacuum filtration. Then, dry the sample under vacuum at 50°C for 12 hours. Finally, single crystals were prepared using a gas-phase diffusion method. 2 mg of the sample was dissolved in 1 ml of tetrahydrofuran (THF), and the solution was transferred to a 2 ml glass bottle. 0.5 ml of chloroform (CHCl3) was slowly added, and the 2 ml bottle was then transferred to a 20 ml glass bottle containing 5 ml of n-hexane solution. The bottle cap was tightened, and the solution was allowed to stand for one day to obtain yellow Schiff base single crystals. The prepared Schiff base single crystals were labeled TAM.

[0045] The selection of solvents and additives is shown in Table 1.

[0046] Table 1. Solvent Screening Table for the Preparation of Single-Crystal TAM

[0047]

[0048] (I) Compound TAM, or terephthalimide-bis(4-amino-3-methylphenol) Schiff base single crystal, is a Schiff base formed by the condensation of one molecule of terephthalaldehyde and two molecules of 4-amino-3-methylphenol. It is a completely symmetrical bis-Schiff base. This Schiff base is a yellow, needle-like crystal, insoluble in water, but soluble in anhydrous methanol, anhydrous ethanol, acetonitrile, tetrahydrofuran, and other organic solvents (as shown in Table 2).

[0049] The crystalline monomer molecular structure of compound TAM is as follows: Figure 2 Its three-dimensional stacking structure is as follows Figure 3 .

[0050] Table 2. Solubility of compound TAM

[0051]

[0052]

[0053] (II) Ultraviolet-Vis absorption spectroscopy characterization:

[0054] This experiment used anhydrous methanol solution to adjust the baseline and scanned the wavelength range of 200-800 nm to perform UV-Vis spectral analysis on anhydrous methanol solution of 1 mg / mL terephthalimide-bis(4-amino-3-methylphenol) Schiff base single crystals. Figure 4As can be seen, there is a strong absorption peak at 209 nm, which is mainly caused by the π→π* transition of the C=N double bond; and the maximum wavelength of the ultraviolet absorption of aromatic aldehydes is around 248 nm, but due to the large π-electron conjugation system in the Schiff base molecule, the ultraviolet absorption is red-shifted to 289 nm; while the absorption peak near 383 nm is mainly caused by the n→π* transition of the C=N double bond and the red shift.

[0055] (III) Fourier Transform Infrared Spectroscopy Characterization (FT-IR):

[0056] The surface organic functional groups of the synthesized Schiff base single crystals were analyzed by Fourier transform infrared spectroscopy. A suitable amount of dried sample powder was ground uniformly with KBr in an agate mortar, pressed into a pellet, and then tested. The infrared spectrum of the terephthalimide-bis(4-amino-3-methylphenol) Schiff base single crystal TAM is shown below. Figure 5 The infrared spectrum of compound TAM shows a characteristic absorption peak for C=N, along with a characteristic absorption peak for the hydroxyl group, indicating the formation of a Schiff base. The infrared spectrum of TAM shows -CHO (1693 cm⁻¹). -1 ) and -NH2(3393cm -1 The characteristic peaks of ) disappear, and C=N(1620cm) appears. -1 ), -OH(3168cm) -1 Ph-O (1223cm) -1 The characteristic peaks of the ) all prove the formation of Schiff bases.

[0057] (iv) Nuclear magnetic resonance (NMR) 1H and 1C spectra analysis:

[0058] The synthesized Schiff base compounds were characterized by nuclear magnetic resonance (NMR) spectroscopy. Deuterated DMSO was used as the solvent, and the 1H and 1C NMR spectra of the Schiff base single crystals were measured, respectively. (See [reference needed]). Figure 6 and Figure 7 .

[0059] 1 HNMR (400MHz, DMSO-d6):

[0060] δ9.39(s,2H),8.57(s,2H),8.02(s,4H),7.08(d,J=8.5Hz,2H),6.71-6.62(m,4H),2.32(s,6H).

[0061] 13 CNMR (101MHz, DMSO-d6):

[0062] δ156.25,155.78,141.35,138.63,134.45,128.60,118.26,116.94,113.40,17.81.

[0063] The carbon and hydrogen NMR spectra of compound TAM show that there are virtually no impurity peaks, indicating that the synthesized compound has high purity. The presence of characteristic C=N absorption peaks in both the carbon and hydrogen NMR spectra indicates that the Schiff base was successfully synthesized.

[0064] (v) X-ray single-crystal diffraction analysis:

[0065] X-ray single-crystal diffraction is an experimental method for analyzing crystal structures. This experiment used single-crystal diffraction analysis to determine the crystal structure of synthesized Schiff base crystals. The specific procedure was as follows: Single crystals of suitable size, solid, with smooth surfaces free of cracks and nicks, were selected under a stereomicroscope and analyzed using a Bruker D8 VENTURE dual-wavelength Mo / Cu diffractometer. During data collection, the crystals were maintained at 100.00 K. Olex2 software was used, and the SHELXT structure solver was employed with intrinsic phase, and the SHELXL refinement package was used for least-squares minimization. The chemical formula of the single-crystal TAM of the terephthalimide-bis(4-amino-3-methylphenol) Schiff base is C1. 22 H 20 N₂O₂ (M = 344.40 g / mol) belongs to the orthorhombic crystal system, and the crystal size for the diffraction experiment is 0.12 × 0.1 × 0.08 mm. 3 The space group is Pbca, Z = 8, the number of electrons in the unit cell is F = 1456.0, and the R1 value for the observable diffraction point is 0.0363.

[0066] Table 3 Crystallographic data

[0067]

[0068] Table 4 Bond Lengths

[0069]

[0070]

[0071] Table 5 Bond Angles

[0072]

[0073] Furthermore, epichlorohydrin was used to epoxidize the terephthalimide-bis(4-amino-3-methylphenol) Schiff base single-crystal compound synthesized in this invention, producing an epoxy resin called terephthalimide bis(4-amino-3-methylphenol) diglycidyl ether (DGETAM). Due to the use of TAM as an intermediate, this epoxy resin exhibits excellent thermal conductivity. Without loaded fillers, its thermal conductivity reaches 0.38 W / m K, which is twice that of the currently mainstream epoxy resin E51.

[0074] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A single crystal of terephthalimide-bis(4-amino-3-methylphenol) Schiff base, characterized in that, The molecular structural formula is: C 22 H 20 The molecular structure of N2O2 crystal monomers is as follows:

2. The single crystal of terephthalimide-bis(4-amino-3-methylphenol) Schiff base according to claim 1, characterized in that, The chemical formula of the terephthalimide-bis(4-amino-3-methylphenol) Schiff base single crystal TAM is C 22 H 20 N₂O₂, with a molar mass M = 344.40 g / mol, belongs to the orthorhombic crystal system, and the crystal size for the diffraction experiment is 0.12 × 0.1 × 0.08 mm. 3 The space group is Pbca, Z = 8, the number of electrons in the unit cell is F = 1456.0, and the R1 value for the observable diffraction point is 0.0363.

3. A method for preparing single crystals of terephthalimide-bis(4-amino-3-methylphenol) Schiff base as described in claim 1, characterized in that, The method specifically includes the following steps: Terephthalaldehyde and 4-amino-m-methylphenol were dissolved in ethanol to form mixture A, and zinc chloride was added to ethanol to form mixture B. Mixture B was added to mixture A, and the mixture was purged with argon gas for reaction. After the reaction was completed, the mixture was refrigerated and washed successively with methanol and ultrapure water. Waste liquid was removed by vacuum filtration. Subsequently, the mixture was vacuum dried and a yellow Schiff base single crystal, namely the terephthalimide-bis(4-amino-3-methylphenol) Schiff base single crystal, was obtained by gas-phase diffusion method.

4. The method for preparing single crystals of terephthalimide-bis(4-amino-3-methylphenol) Schiff base according to claim 3, characterized in that, In solution A, the molar ratio of terephthalaldehyde, 4-amino-m-methylphenol, and ethanol is 0.05 mol: 0.105 mol: 90 mL; in solution B, the molar ratio of zinc chloride to ethanol is 0.0025 mol: 10 mL.

5. The method for preparing single crystals of terephthalimide-bis(4-amino-3-methylphenol) Schiff base according to claim 3, characterized in that, The reaction temperature was 30℃ and the reaction time was 4 hours; the refrigeration time was 12 hours; the vacuum drying temperature was 50℃ and the drying time was 12 hours.

6. The method for preparing single crystals of terephthalimide-bis(4-amino-3-methylphenol) Schiff base according to claim 3, characterized in that, The method for preparing single crystals by vapor-phase diffusion infiltration is as follows: Dissolve 2 mg of sample in 1 ml of tetrahydrofuran, transfer the solution to a 2 ml glass bottle, slowly add 0.5 ml of chloroform, then transfer the 2 ml glass bottle to a 20 ml glass bottle containing 5 ml of n-hexane solution, tighten the cap, and let stand for 1 day.

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