A eutectic luminescent material based on pillararene, and its preparation method and application

Abstract

The present invention discloses a co-crystal luminescent material based on pillararenes, its preparation method, and application. Each unit cell in the material contains two different host-guest composite crystal structures bound together by weak interactions; one host-guest composite crystal structure comprises an EtP5 host molecule housing a TCNB guest molecule; the other host-guest composite crystal structure comprises an EtP5 host molecule housing a solvent molecule capable of host-guest recognition with the EtP5. The preparation method provided by the present invention results in a significantly red-shifted luminescence of the prepared material compared to the precursor molecule, and has the advantages of readily available host macrocyclic molecules, strong assembly driving force, simple crystallization operation, mild crystal growth conditions, and low equipment requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal luminescent materials, and in particular to a eutectic luminescent material based on pillararenes, a preparation method thereof, and an application thereof in a light-emitting device. Background Art

[0002] Organic eutectic engineering, as an emerging and convenient non-covalent strategy for constructing novel supramolecular solid materials, has become a research hotspot in various fields, including optoelectronics, bipolar charge transport materials, and biopharmacology. Compared to traditional covalent modification, the components of eutectics can assemble into highly ordered superstructures with the assistance of intermolecular non-covalent interactions. Through the synergistic effects of different building blocks, novel multifunctional applications that are difficult to achieve with a single component can be achieved. Therefore, eutectic engineering offers many advantages, such as environmental friendliness, high efficiency, and the avoidance of lengthy synthesis steps, for obtaining target materials. It demonstrates great scientific significance and practical application value in the construction of solid-state functional materials.

[0003] Among them, the construction of organic eutectic luminescent materials is an important part of eutectic materials. For example, eutectic luminescent materials with white light emission, two-photon absorption, nonlinear optical properties and phosphorescence properties have been widely used in different fields of materials science. Generally speaking, the common construction precursors of eutectic luminescent materials are organic small molecules, which are relatively simple in structure and molecular stacking. Scientists in different fields have conducted systematic and detailed exploration and research in this regard. A representative example (Adv. Mater. [J], 2012, 24 (39): 5345-5351) is a charge transfer complex constructed based on 1,2,4,5-tetracyanobenzene (TCNB). Due to the charge transfer transition from the π-conjugated electron donor to the TCNB electron acceptor, they can be assembled into a series of luminescent organic microtubes with absorption in the visible light region. However, the selection and matching of suitable electron donor / acceptor pairs have limited its further development.

[0004] Pillarene macrocyclic molecules are widely used in the preparation of solid-state functional materials due to their rich host-guest complexation characteristics. In recent years, the combination of pillararene supramolecular chemistry and eutectic engineering science has provided a method for effectively constructing solid-state supramolecular materials with valuable properties, and has been successfully applied to the preparation of functional materials with gas-induced color change and adsorption behavior. For example, Professor Li Chunju of Tianjin Normal University designed and constructed a macrocyclic eutectic based on pillar[5]arene and N,N'-bis(n-butyl)benzenetetramethyleneimine (Angew.Chem.,Int.Ed.[J],2020,59(49):22012-22016), which showed gas-induced color change response behavior to halogenated alkane vapor, but no corresponding eutectic fluorescence properties were reported. Professor Huang Feihe of Zhejiang University reported a host-guest crystal complex based on fully ethyl-substituted pillararenes and iodine molecules (J.Am.Chem.Soc.[J], 2017, 139(43):15320-15323), demonstrating its reversible iodine adsorption and release behavior. However, there is no report on the corresponding cocrystal fluorescence properties. From a structural point of view, pillararenes have a stable configuration of electron-rich annular cavities, which are very suitable as electron donors for the construction of luminescent cocrystal materials. However, although great progress has been made in the research of pillararene cocrystals, the development of cocrystal luminescent materials based on pillararenes remains a challenging research topic. Summary of the Invention

[0005] In view of the above technical problems, the present invention provides a co-crystal luminescent material based on pillar arene, a preparation method thereof and an application thereof in a light-emitting device. The present invention uses bisdiethoxy pillar[5]arene (hereinafter referred to as EtP5) and 1,2,4,5-tetracyanobenzene (hereinafter referred to as TCNB) as raw materials to synthesize a crystal material with a unique dual host-guest complex coexisting under specific and appropriate conditions, and in a specific embodiment, prepares The eutectic luminescent material generates red fluorescence with a wavelength of 630 nm under irradiation of ultraviolet light with a wavelength of 365 nm. The present invention also provides a preparation method of the material, which has a simple crystallization process, mild growth conditions, short crystallization time, and low equipment requirements.

[0006] A pillararene-based eutectic luminescent material, wherein each unit cell of the pillararene-based eutectic luminescent material contains two different host-guest composite crystal structures bound together by weak interactions;

[0007] Among them, one of the host-guest composite crystal structures is a 1,2,4,5-tetracyanobenzene guest molecule contained in a bis-diethoxy pillar[5]arene host molecule, that is,

[0008] Another host-guest complex crystal structure is a bis-diethoxy pillar[5]arene host molecule containing a solvent molecule that can undergo host-guest recognition with the bis-diethoxy pillar[5]arene;

[0009] The chemical structural formula of the bisdiethoxy pillar[5]arene is as follows:

[0010]

[0011] The chemical structural formula of the 1,2,4,5-tetracyanobenzene is as follows:

[0012]

[0013] The pillararene-based eutectic luminescent material generates red fluorescence with a wavelength of 630 nm under the irradiation of ultraviolet light with a wavelength of 365 nm.

[0014] When the host-guest composite crystal structure is a bis-diethoxy pillar[5]arene host molecule containing two tetrahydrofuran (hereinafter referred to as THF) guest molecules, the corresponding pillararene-based eutectic luminescent material is

[0015] The pillararene-based eutectic luminescent material It belongs to the triclinic system, the space group is P-1, and its unit cell parameters are: α=101.532°(2), β=91.316°(2), γ=95.222°(2),

[0016] When the host-guest composite crystal structure is a bis-diethoxy pillar[5]arene host molecule containing a n-hexane (hereinafter referred to as Hex) guest molecule, the corresponding pillararene-based eutectic luminescent material is

[0017] The pillararene-based eutectic luminescent material It belongs to the triclinic system, the space group is P-1, and its unit cell parameters are: α=101.605°(2), β=91.232°(2), γ=95.326°(2),

[0018] The present invention also provides two methods for preparing the pillararenes-based eutectic luminescent materials.

[0019] In the preparation method of the pillararene-based co-crystal luminescent material, the EtP5 macrocyclic molecule is first synthesized, and the prepared EtP5 is recrystallized and then vacuum-dried to obtain a pure EtP5 compound. The recrystallization solvent is tetrahydrofuran, but is not limited thereto.

[0020] Then, one of the preparation methods of the eutectic luminescent material based on pillar arene is to dissolve bisdiethoxy pillar[5]arene and 1,2,4,5-tetracyanobenzene in a good solvent A, and volatilize and crystallize at room temperature; the good solvent molecule A can undergo host-guest recognition with bisdiethoxy pillar[5]arene.

[0021] The preparation method utilizes the strong host-guest complexation recognition site and complexation ability of the bisdiethoxy pillar[5]arene cavity and the electron-rich characteristics of the pillar arene skeleton to achieve the preparation of the cocrystal. The electron-deficient acceptor TCNB and EtP5 are constructed through host-guest interaction and charge transfer interaction. During the cocrystal growth process, the growth solvent was good solvent A. After the TCNB molecules were completely encapsulated by EtP5 molecules, the excess EtP5 molecules, along with the good solvent molecules that could undergo host-guest recognition, formed another host-guest complex crystal structure. The two host-guest complex crystals were bound together by C–H…π interactions, ultimately forming this unique crystal structure containing two different host-guest complexes.

[0022] Preferably, the good solvent A is tetrahydrofuran, and the corresponding pillararene-based eutectic luminescent material is

[0023] Another method for preparing a co-crystal luminescent material based on pillar arene is to dissolve bisdiethoxy pillar[5]arene and 1,2,4,5-tetracyanobenzene in a good solvent B, place the mixed solution in a poor solvent atmosphere for diffusion and penetration, and crystallize it at room temperature; the poor solvent molecules can undergo host-guest recognition with bisdiethoxy pillar[5]arene.

[0024] The preparation method utilizes the strong host-guest complexation recognition site and complexation ability of the bisdiethoxy pillar[5]arene cavity and the electron-rich characteristics of the pillar arene skeleton to achieve the preparation of the cocrystal. The electron-deficient acceptor TCNB and EtP5 are constructed through host-guest interaction and charge transfer interaction. During the eutectic growth process, the growth solvent is good solvent B. The poor solvent diffuses into the good solvent B containing EtP5 molecules. After the TCNB molecules are completely encapsulated by the EtP5 molecules, the excess EtP5 molecules and the poor solvent molecules, which can undergo host-guest recognition, form another host-guest complex crystal structure as described above. The two host-guest complex crystals are bound together by C–H…π interactions, ultimately forming this unique crystal structure containing two different host-guest complexes.

[0025] Preferably, the good solvent is chloroform, the poor solvent is n-hexane, and the corresponding pillararene-based eutectic luminescent material is

[0026] Preferably, in the above two preparation methods, the molar ratio of the bisdiethoxy pillar[5]arene to 1,2,4,5-tetracyanobenzene is 2:0.5-1.

[0027] In a preferred embodiment, the preparation method of the pillararene-based eutectic luminescent material is specifically as follows:

[0028] Weigh EtP5 and TCNB (molar ratio of 2:0.5-1) in a glass vial, add tetrahydrofuran and sonicate until the solid is completely dissolved, and filter to remove insoluble impurities. Cover the glass vial with a sealing film and leave several small holes. Place the mixed solution at room temperature and slowly evaporate to precipitate the eutectic, thus obtaining the pillararene-based eutectic luminescent material.

[0029] In a preferred embodiment, the preparation method of the pillararene-based eutectic luminescent material is specifically as follows:

[0030] Weigh EtP5 and TCNB (molar ratio of 2:0.5-1) in a glass vial, add chloroform and sonicate until the solid is completely dissolved, and filter to remove insoluble impurities. Place the glass vial in an n-hexane atmosphere. As the n-hexane slowly penetrates into the chloroform solution of the mixture, blocky eutectics will slowly precipitate, thus obtaining the pillararene-based eutectic luminescent material.

[0031] The present invention also provides the use of the pillararene-based eutectic luminescent material or the pillararene-based eutectic luminescent material prepared by the preparation method in a light-emitting device.

[0032] Compared with the prior art, the present invention has at least the following advantages:

[0033] 1. The present invention provides a novel eutectic luminescent material with a unique and novel structure. In this eutectic luminescent material, two discrete host-guest complexes are bound together by C–H…π interactions, forming a unique stacking arrangement. Unlike a simple stacking crystal structure, this unique crystal structure enables the material to produce red fluorescence at a wavelength of 630 nm under irradiation with ultraviolet light at a wavelength of 365 nm, whereas a simple stacking crystal structure would likely produce no fluorescence.

[0034] 2. The present invention provides a method for preparing the material. The method is not only an innovative exploration and expansion of the field of pillararene crystal engineering, but also can be used to prepare a new type of eutectic luminescent material. Solvent guest molecules.

[0035] 3. The preparation method of the material provided by the present invention, through co-crystallization engineering, produces a narrowed band gap in the charge transfer co-crystal prepared, resulting in a significant red-shifted emission of the prepared co-crystal material compared to the precursor molecule, achieving the modulation of fluorescence from the ultraviolet region to the visible region, and has broad application prospects in the field of optics. Furthermore, it provides relevant insights into the possibility of changing the emission wavelength of solid materials through co-crystallization strategies, thereby changing their fluorescence properties. In specific implementations, the feasibility and universality of the co-crystal strategy in constructing pillararene co-crystals with multiple host-guest recognition motifs have also been confirmed.

[0036] 4. The preparation method of the pillararene-based co-crystal luminescent material also has the advantages of easy availability of precursor macrocyclic molecules, strong assembly driving force, simple crystallization process operation, mild crystal growth conditions, and low equipment requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 1H NMR spectra of the EtP5 macrocyclic molecule and the TCNB guest molecule synthesized in Example 1.

[0038] Figure 2 For Example 4 The crystal structure diagram and the stacking arrangement diagram of two discrete host-guest complexes.

[0039] Figure 3 For Example 5 The crystal structure diagram and the stacking arrangement diagram of two discrete host-guest complexes.

[0040] Figure 4 For EtP5 and eutectic material in Example 6 and eutectic materials Fluorescence emission curve of .

[0041] Figure 5This is the eutectic material tested in Example 6 and eutectic materials Fluorescence lifetime curves. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings and specific examples. It should be understood that these examples are intended to illustrate the present invention and are not intended to limit the scope of the invention. The operating methods in the following examples where no specific conditions are specified are generally performed under conventional conditions or as recommended by the manufacturer.

[0043] Example 1

[0044] Preparation of bisdiethoxy [5]arene crystals: Weigh 2 g of bisdiethoxy [5]arene and place it in 20 mL of tetrahydrofuran. Heat the solution to boiling and add the tetrahydrofuran solution dropwise until all the solids are dissolved. After filtering while hot, store the solution at room temperature overnight. Collect the precipitated crystals by filtration and dry them in vacuum at 80°C to obtain a white powder, which is recorded as EtP5.

[0045] The H-NMR analysis of this example shows the synthesis of the target compound, and the specific results are as follows:

[0046] EtP5, 1 H NMR (600MHz, CDCl3, 298K) δ (ppm): 6.71 (s, 10H), 3.80-3.84 (q, 20H), 3.76 (s, 10H), 1.25 (t, 30H).

[0047] The results of the H NMR spectra of the prepared bis-diethoxy column [5] aromatic material and the commercial TCNB material are shown in Figure 2. Figure 1 shown.

[0048] Example 2

[0049] Preparation of co-crystals by growing compound EtP5 and TCNB The specific process is as follows: EtP5 (17.8 mg, 0.02 mmol) and TCNB (1.78 mg, 0.01 mmol) were weighed in a 4 mL culture bottle, dissolved in 3 mL of tetrahydrofuran and sonicated until the solids were completely dissolved. Insoluble impurities were removed by filtration using an organic microporous filter membrane (0.22 μm). The mouth of the culture bottle was covered with a sealing film, leaving 3-4 small holes. The clear mixed solution was placed at room temperature and slowly evaporated for 2-3 days to obtain a yellow eutectic, which was recorded as

[0050] Example 3

[0051] Preparation of co-crystals by growing compound EtP5 and TCNB The specific process is as follows: EtP5 (17.8 mg, 0.02 mmol) and TCNB (1.78 mg, 0.01 mmol) were weighed in a 4 mL culture bottle, 2 mL of chloroform was added and ultrasonicated until the solid was completely dissolved, insoluble impurities were removed by filtering with an organic microporous filter membrane (0.22 μm), and the filtrate was divided equally in two 4 mL culture bottles. The above culture bottles were placed in two 20 mL culture bottles with 2 mL of n-hexane solution, and the 20 mL culture bottles were sealed to create a closed environment. At room temperature, as n-hexane slowly penetrated into the chloroform solution of the mixture, light yellow block single crystals slowly precipitated after 7 days, which was recorded as

[0052] Example 4

[0053] eutectic X-ray single crystal diffraction analysis of . Its unit cell parameters are: α=101.532°(2), β=91.316°(2), γ=95.222°(2), The single crystal structure shows that two different host-guest complexes coexist in a solid-state eutectic superstructure, which is extremely unique in the field of solid-state supramolecular chemistry. In addition, two types of EtP5 molecules were observed in this superstructure. The first type of EtP5 molecule has a regular pentagonal conformation, and its cavity encloses two THF molecules ( Figure 2 a), where multiple CH…O hydrogen bonds are the main driving force for the formation of this [2] pseudorotaxane. The second type of EtP5 molecule has a deformed pentagonal conformation, and its cavity encapsulates a TCNB molecule ( Figure 2 b), where C–H…π and C–H…N interactions stabilize the formation of this [2] pseudorotaxane. Overall, two discrete host-guest systems are held together by C–H…π interactions ( Figure 2 c).

[0054] Example 5

[0055] eutectic X-ray single crystal diffraction analysis of . Its unit cell parameters are: α=101.605°(2), β=91.232°(2), γ=95.326°(2), The specific single crystal structure shows that Similarly, through unique crystal engineering design, two different host-guest complexes coexist in a solid-state eutectic superstructure ( Figure 3). Among them, a TCNB molecule is encapsulated in the cavity of the macrocyclic EtP5 through C–H…π and C–H…N interactions. On the other hand, a n-hexane is encapsulated in the cavity of another EtP5 adjacent to the above-mentioned pseudorotaxane [2] through multiple C–H…π interactions. Crystal The stacking method in The molecular arrangement in the crystal superstructure is exactly the same. The above results provide important evidence that the basic unit of this eutectic structure can be used as an excellent building block to accommodate specific guest molecules.

[0056] Example 6

[0057] eutectic and Optical characterization of two eutectics and The crystalline fluorescence spectra of EtP5 showed a broad emission peak at 630 nm, which was significantly red-shifted compared to the emission of the precursor EtP5 molecule at 332 nm. Figure 4 ). In other words, under a specific supramolecular crystal engineering method, the emission of the material was modulated from the ultraviolet region to the visible light region. In addition, based on the corresponding emission decay curve shown in the time-resolved fluorescence spectrum, the crystalline and The fluorescence lifetimes (τ) of 1.76 ns and 1.47 ns, respectively, further prove their fluorescence emission characteristics ( Figure 5 These results suggest that supramolecular cocrystal engineering of pillararenes offers great opportunities for achieving solid-state fluorescence modulation and subsequently constructing solid-state luminescent materials.

[0058] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A eutectic luminescent material based on pillararenes, characterized in that: In each unit cell of the pillararene-based eutectic luminescent material, there are two different host-guest composite crystal structures bound together by weak interactions; Among them, a host-guest composite crystal structure is a bis-diethoxy pillar[5] aromatic hydrocarbon host molecule containing a 1,2,4,5-tetracyanobenzene guest molecule, that is, Another host-guest complex crystal structure is a bis-diethoxy pillar[5]arene host molecule containing two tetrahydrofuran guest molecules or one n-hexane guest molecule; The chemical structural formula of the bisdiethoxy pillar[5]arene is as follows: The chemical structural formula of the 1,2,4,5-tetracyanobenzene is as follows:

2. The method for preparing a eutectic luminescent material based on pillararenes according to claim 1, characterized in that: The pillararene-based eutectic luminescent material is obtained by dissolving bisdiethoxy pillar[5]arene and 1,2,4,5-tetracyanobenzene in tetrahydrofuran and volatilizing and crystallizing at room temperature.

3. The method for preparing a eutectic luminescent material based on pillararenes according to claim 2, characterized in that: The molar ratio of the bisdiethoxy pillar[5]arene to 1,2,4,5-tetracyanobenzene is 2:0.5-1.

4. The method for preparing a eutectic luminescent material based on pillararenes according to claim 1, wherein: The pillararene-based eutectic luminescent material is obtained by dissolving bisdiethoxy pillar[5]arene and 1,2,4,5-tetracyanobenzene in a good solvent B, diffusing and penetrating the mixed solution in a n-hexane atmosphere, and crystallizing the mixed solution at room temperature.

5. The method for preparing a eutectic luminescent material based on pillararenes according to claim 4, characterized in that: The molar ratio of the bisdiethoxy pillar[5]arene to 1,2,4,5-tetracyanobenzene is 2:0.5-1.

6. Use of the pillararene-based eutectic luminescent material according to claim 1 or the pillararene-based eutectic luminescent material prepared by the preparation method according to any one of claims 2 to 5 in a light-emitting device.

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