Free radical polymer single crystals constructed based on boron-nitrogen coordination bonds, their preparation and applications

Abstract

This invention discloses a free radical polymer single crystal constructed based on boron-nitrogen coordination bonds, its preparation method, and its application in the preparation of organic electron spin devices, organic field-effect transistor devices, or near-infrared dyes. The free radical polymer single crystal is formed by the boron free radical monomer and pyridine monomer, as shown in formula (1), through boron-pyridine nitrogen coordination linkage. The preparation method involves a solvothermal reaction of the boron free radical monomer and pyridine monomer in an organic solvent. After the reaction, the temperature is programmed to cool down, and crystallization is performed to obtain the free radical polymer single crystal constructed based on boron-nitrogen coordination bonds. This invention can regulate the spin interaction between free radicals on the polymer chain through boron-nitrogen coordination bonds to change the free radical properties of the material and transform the material's magnetic properties.

Description

Technical Field

[0001] This invention relates to the field of organic free radical compound technology, specifically to a free radical polymer single crystal constructed based on boron-nitrogen coordination bonds, its preparation method, and its application. Background Technology

[0002] Organic free radicals possess unpaired single electrons, resulting in high reactivity. With the rapid development of organic free radicals and the resolution of stability issues, various stable free radical materials have been developed. Compared to traditional small molecule free radicals, free radical polymer materials exhibit multi-level structures and superior properties, finding wide application in areas such as battery energy storage, photovoltaic devices, biomedical imaging, and magnetic materials. Therefore, the efficient construction of free radical polymers has become a research hotspot in recent years.

[0003] Currently, most free radical polymers are formed by grafting stable free radical molecules onto polymer side chains. Unpaired electrons, acting as spin units, can interact with the polymer backbone through space or the side chains. A paper (Science, 2018, 359(6382):1391-1395) reports a 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) non-conjugated free radical polymer that exhibits rapid solid-state charge transfer reactions and extremely high conductivity at sub-environmental glass transition temperatures. However, non-conjugated free radical polymers constructed by grafting free radical molecules onto the polymer backbone cannot obtain precise single-crystal structure information, making it difficult to clarify the stacking patterns of free radicals between polymer chains, long-range order, secondary interactions, and kinetic and thermodynamic factors. These are crucial for a deep understanding of the structure-property relationship. A paper (Nat Commun, 2022, 13(1):6116) reports a method using a dithiophene-functionalized TTA ligand and rare earth ions Eu... 3+ The self-assembled three-dimensional metal-organic framework EuTTA can be transformed into an organic free radical framework material stable above 300℃ under thermally induced conditions, which can be used for efficient photothermal conversion and solar-driven water evaporation applications. However, the development of free radical polymers constructed through metal coordination is severely limited by the high toxicity and radioactivity of the metals and the weak stability of the coordination materials. Therefore, it is necessary to develop pure organic free radical polymer crystal materials, while the preparation of pure organic free radical polymer single crystals remains a highly challenging research area.

[0004] On the other hand, pure organic free radical polymer single crystal materials have advantages such as light weight, low toxicity, high safety, and good stability. Therefore, how to efficiently prepare pure organic free radical polymer single crystal materials with well-defined structures is of great significance. The traditional way to construct free polymers is to graft stable free radical small molecules onto the polymer backbone. If unpaired electrons or spin units are retained in the backbone through boron-nitrogen coordination, the free radical units between the backbones can be directly spin-coupled and the single-occupied molecular orbitals (SOMOs) will partially overlap. This method does not introduce metals, is easy to obtain single crystals, and the resulting free radical polymers may have better solid-state properties, huge magnetic moments, and magnetic orientation order. Summary of the Invention

[0005] This invention provides a series of free radical polymer single crystal materials with different topological structures constructed by boron-nitrogen coordination bonds, and the free radical properties and magnetic properties of the materials can be changed by controlling the spin interaction between free radicals on the polymer chain through boron-nitrogen coordination bonds.

[0006] A free radical polymer single crystal based on boron-nitrogen coordination bond is formed by boron free radical monomer and pyridine monomer as shown in formula (1) through boron-pyridine nitrogen coordination link;

[0007]

[0008] The pyridine monomer is one of the compounds shown in formulas (2) to (14):

[0009]

[0010] The free radical polymer single crystal of the present invention is formed by boron-nitrogen coordination polymerization of different pyridine monomers and boron-containing free radical monomers, and has different crystal packing modes and topological structures, different multi-radical properties and different magnetic properties.

[0011] The present invention also provides a method for preparing the free radical polymer single crystal based on boron-nitrogen coordination bonds, wherein the boron free radical monomer and the pyridine monomer are subjected to a solvothermal reaction in an organic solvent, and after the reaction is completed, the temperature is cooled down to obtain the free radical polymer single crystal based on boron-nitrogen coordination bonds.

[0012] The boron radical monomer can be obtained by existing technology, for example, by referring to the patent specification with publication number CN 113773338A.

[0013] In the method for preparing free radical polymer single crystals based on boron-nitrogen coordination bonds, the molar ratio of the boron free radical monomer to the pyridine monomer can be 1 to 2:1.

[0014] The method for preparing free radical polymer single crystals based on boron-nitrogen coordination bonds, wherein the organic solvent may be at least one selected from benzene, toluene, xylene, mesitylene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,2,4-trichlorobenzene.

[0015] When the amount of organic solvent is too small, the raw materials cannot be completely dissolved, which is not conducive to crystallization; conversely, when the amount of organic solvent is too large, the polymer does not form a saturated solution, and crystals are not easily precipitated. In a preferred embodiment, in the method for preparing free radical polymer single crystals based on boron-nitrogen coordination bonds, the ratio of the amount of boron free radical monomer to the amount of organic solvent is 0.03 mol: 5-50 mL.

[0016] If the solvothermal reaction temperature is too low, the polymerization process will be slow, and the precipitated crystals will mostly be raw materials; if the temperature is too high, the polymerization process will be too fast, and the product will mostly be disordered flocculent polymers rather than crystals. If the solvothermal reaction time is too short, the crystals cannot precipitate completely. In a preferred embodiment, in the method for preparing free radical polymer single crystals based on boron-nitrogen coordination bonds, the solvothermal reaction temperature can be 80–130°C, and the time can be 1–5 days.

[0017] In one embodiment, the method for preparing free radical polymer single crystals based on boron-nitrogen coordination bonds involves adding the boron free radical monomer and the pyridine monomer to the organic solvent, sonicating for 10-30 minutes, and then carrying out the solvothermal reaction.

[0018] The excessively rapid cooling rate can lead to poor crystal quality and difficulty in resolving the single-crystal structure. In one embodiment, the method for preparing free radical polymer single crystals based on boron-nitrogen coordination bonds involves a cooling rate of 1–2°C per hour, with the cooling endpoint being room temperature.

[0019] In one embodiment, the method for preparing the free radical polymer single crystal based on boron-nitrogen coordination bonds involves solid-liquid separation after the temperature program is completed, followed by drying of the solid to obtain the free radical polymer single crystal based on boron-nitrogen coordination bonds.

[0020] This invention also provides the application of the free radical polymer single crystal based on boron-nitrogen coordination bonds in the preparation of organic electronic spin devices, organic field-effect transistor devices, or near-infrared dyes.

[0021] The free radical polymer single crystals constructed based on boron-nitrogen coordination bonds of this invention are pure organic free radical polymers, formed by the polymerization of boron-containing free radical monomers and different pyridine monomers through boron-nitrogen coordination bonds. Compared with conjugated or non-conjugated free radical polymers prepared by organic reactions, they have the advantages of simple preparation and separation, well-defined structure, and easy precise control. Compared with free radical polymers prepared by metal coordination, they have the advantages of good stability, light weight, low toxicity, and high safety performance, while also possessing excellent electrical and magnetic properties. The preparation method of the free radical polymer single crystals described in this invention is simple to operate, highly universal, requires low equipment, has mild reaction conditions, and can produce products in large quantities.

[0022] Compared with the prior art, the beneficial effects of this invention are as follows:

[0023] 1. This invention utilizes boron- and indofluorene-containing organic free radical monomers and different polypyridine ligands to construct free radical polymers through boron-nitrogen coordination, which can obtain more obvious singlet biradical properties compared to the monomers.

[0024] 2. The free radical polymer single crystal based on boron-nitrogen coordination bonds of the present invention has air stability. It has been tested that the solid ultraviolet and near-infrared absorption spectrum remains unchanged in air for 12 hours, which provides a possibility for practical applications.

[0025] 3. The free radical polymer single crystal based on boron-nitrogen coordination bonds of the present invention is crystallized by programmed cooling, which makes it easy to obtain the single crystal structure. By analyzing the interaction between monomer and solvent molecules, the stacking mode of polymer chains, and the spin interaction between free radicals in the crystal structure, it can be seen that different topological structures bring about different free radical properties and changes in magnetic behavior.

[0026] 4. The free radical polymer single crystal based on boron-nitrogen coordination bonds of the present invention has the property of near-infrared light absorption, and the near-infrared absorption band can be broadened to about 1000nm, which has the potential to prepare near-infrared dyes.

[0027] 5. Compared to monomers, the free radical polymer single crystals constructed based on boron-nitrogen coordination bonds of the present invention have a narrower band gap, which has the potential to fabricate organic field-effect transistor devices.

[0028] 6. The free radical polymer single crystal based on boron-nitrogen coordination bonds of the present invention exhibits weak antiferromagnetic interaction at low temperatures and obvious paramagnetic properties at high temperatures, and has the potential to prepare organic electronic spin devices. Attached Figure Description

[0029] Figure 1 The single-crystal packing pattern of the free radical polymer single crystal BNRP-1 in Example 1 is shown.

[0030] Figure 2 This is the single-crystal packing pattern of the free radical polymer single crystal BNRP-2 in Example 2;

[0031] Figure 3 The single-crystal packing pattern of the free radical polymer single crystal BNRP-3 in Example 3 is shown.

[0032] Figure 4 The images show the paramagnetic resonance diagrams of the free radical polymer single crystals BNRP-1, BNRP-2, and BNRP-3 and boron free radical monomer 1 in Examples 1-3.

[0033] Figure 5 The temperature-dependent paramagnetic resonance image of the free radical polymer single crystal BNRP-1 in Example 1 is shown.

[0034] Figure 6 The temperature-dependent paramagnetic resonance image of the free radical polymer single crystal BNRP-2 in Example 2 is shown.

[0035] Figure 7 The image shows the temperature-varying paramagnetic resonance (PMNR) pattern of the free radical polymer single crystal BNRP-3 in Example 3.

[0036] Figure 8 This is the UV absorption spectrum of the free radical polymer single crystal BNRP-2 solid in Example 2;

[0037] Figure 9 The graphs show the molar magnetic susceptibility of the free radical polymer single crystals BNRP-1, BNRP-2, and BNRP-3 in Examples 1-3 as a function of temperature. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0039] Example 1

[0040]

[0041] Boron free radical monomer 1 and 4,4'-bipyridine 2 were added to a reaction vessel containing chlorobenzene, sonicated for 10 minutes, placed in an oven, heated to 110°C, and reacted for 1 day. After the reaction was completed, the temperature was programmed to decrease by 1°C per hour to room temperature. The product crystals were obtained by filtration, and the crystals were placed in an oven and vacuum dried at 50°C to obtain a blue solid powder, which is the free radical polymer single crystal BNRP-1.

[0042] This free radical polymer single crystal is a monoclinic crystal with space group P21 / c, and its unit cell parameters are: alpha = 90, beta=96.479(5), c=22.534(3), gamma=90,

[0043] Example 2

[0044]

[0045] Boron free radical monomer 1 and 1,2-bis(4-pyridyl)ethylene 3 were added to a reaction vessel containing 1,3-dichlorobenzene, sonicated for 10 minutes, placed in an oven, heated to 100°C, and reacted for 2 days. After the reaction was completed, the temperature was programmed to decrease by 1°C per hour to room temperature. The product crystals were obtained by filtration, and the crystals were placed in an oven and vacuum dried at 50°C to obtain a blue solid powder, which is the free radical polymer single crystal BNRP-2.

[0046] This free radical polymer single crystal is a monoclinic crystal with space group C12 / c1, and its unit cell parameters are: alpha = 90, beta=111.005(3), c=17.5919(9), gamma=90,

[0047] Example 3

[0048]

[0049] Boron free radical monomer 1 and 1,2-bis(pyridin-4-yl)acetylene 4 were added to a reaction vessel containing 1,2-dichlorobenzene, sonicated for 10 minutes, placed in an oven, heated to 120°C, and reacted for 3 days. After the reaction was completed, the temperature was programmed to decrease by 1°C per hour to room temperature. The product crystals were obtained by filtration, and the crystals were placed in an oven and vacuum dried at 50°C to obtain a blue solid powder, which is the free radical polymer single crystal BNRP-3.

[0050] This free radical polymer single crystal is a monoclinic crystal with space group P-1, and its unit cell parameters are: alpha = 75.425(13), beta=73.201(14), c=19.837(4), gamma=81.443(13),

[0051] Example 4

[0052]

[0053] Boron free radical monomer 1 and 2,4,6-tris(4-pyridine)1,3,5-triazine 9 were added to a reaction vessel containing 1,2,4-trichlorobenzene. The mixture was sonicated for 10 minutes, placed in an oven, heated to 90°C, and reacted for 2 days. After the reaction was completed, the temperature was programmed to decrease by 1°C per hour until it reached room temperature. The product crystals were obtained by filtration. The crystals were placed in an oven and vacuum dried at 50°C to obtain a blue solid powder, which is the free radical polymer single crystal BNRP-4.

[0054] Example 5

[0055]

[0056] Boron free radical monomer 1 and tetrakis(4-pyridinebiphenyl)ethylene 13 were added to a reaction vessel containing toluene, sonicated for 10 minutes, placed in an oven, heated to 120°C, and reacted for 3 days. After the reaction was completed, the temperature was programmed to decrease by 1°C per hour to room temperature. The product crystals were obtained by filtration, and the crystals were placed in an oven and dried under vacuum at 50°C to obtain a blue solid powder, which is the free radical polymer single crystal BNRP-5.

[0057] Single-crystal structure analysis was performed on the free radical polymer single crystals BNRP-1, BNRP-2, and BNRP-3 synthesized in Examples 1, 2, and 3. The free radical polymer single crystals BNRP-1, BNRP-2, and BNRP-3 all formed zigzag-shaped one-dimensional polymer chains on a one-dimensional scale, such as... Figure 1 , Figure 2 , Figure 3 The figures show crystal packing diagrams along axes a, b, and c, respectively. From the c-axis direction, it can be seen that BNRP-1 and BNRP-2 mainly form two parallel, interlaced polymer chains in different directions. The dihedral angle between the two chains of BNRP-1 is 51.1°, and the dihedral angle between the two chains of BNRP-2 is 84.6°. BNRP-3 mainly forms a sandwich structure, where two free radical monomers are inserted between two polymer chains through π-π interactions. Clearly, the spin interactions between the free radicals in the three types of free radical polymer chains are different, resulting in different electron paramagnetic resonance signal intensities in the free radical polymers, such as... Figure 4 As shown.

[0058] Temperature-dependent electron paramagnetic resonance (ESR) analysis was performed on the free radical polymer single crystals BNRP-1, BNRP-2, and BNRP-3 synthesized in Examples 1, 2, and 3, as shown in the figure. Figure 5 , Figure 6 , Figure 7 As shown, the free radical polymer single crystals BNRP-1, BNRP-2, and BNRP-3 exhibit significant ESR signal responses at different temperatures. eA value of 2.0020 indicates the presence of single electrons in the radical. An enhanced ESR signal was observed with increasing temperature, indicating that the number of thermally excited triplet biradicals increases with temperature, proving that the radical polymer single crystal is in the singlet biradical ground state. The significant paramagnetic properties suggest that the radical polymer single crystal has the potential to be used as a material for organic spintronic devices.

[0059] Solid-state UV-Vis absorption spectroscopy analysis was performed on the single-crystal BNRP-2 free radical polymer synthesized in Example 2, such as... Figure 8 As shown, the main absorption peaks of BNRP-2 are located at 627 nm and 890 nm, exhibiting near-infrared absorption properties. After being placed in air for 12 hours, the absorption spectrum remained unchanged, demonstrating good stability. This indicates that the free radical polymer single-crystal BNRP-2 of the present invention possesses significant near-infrared absorption properties and good stability, showing potential for application in the preparation of near-infrared dyes.

[0060] Superconducting quantum interference magnetic measurement system (SQUID) analysis was performed on the free radical polymer single crystals BNRP-1, BNRP-2, and BNRP-3 synthesized in Examples 1, 2, and 3, such as... Figure 9 As shown, the molar magnetic susceptibility of free radical polymers BNRP-1, BNRP-2, and BNRP-3 gradually increases with increasing temperature below 25 K, and remains unchanged above 100 K, indicating that they exhibit weak antiferromagnetic interactions at low temperatures and paramagnetism at high temperatures. In contrast, boron free radical monomer 1 remains paramagnetic, indicating that the magnetic properties of the material at low temperatures are altered by boron-nitrogen coordination and spin interactions between free radical polymer chains.

[0061] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A radical polymer single crystal based on boron-nitrogen coordination bond construction, characterized in that, The boron radical monomer shown in formula (1) is formed by boron-pyridine nitrogen coordination linking with the pyridine monomer; The pyridine monomer is one of the compounds shown in formulas (2) to (14):

2. The method for preparing a radical polymer single crystal based on a boron-nitrogen coordinate bond according to claim 1, characterized by, The boron radical monomer and the pyridine monomer were subjected to a solvothermal reaction in an organic solvent. After the reaction was completed, the temperature was gradually reduced, and crystallization was performed to obtain the radical polymer single crystal based on boron-nitrogen coordination bonds.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the boron radical monomer to the pyridine monomer is 1 to 2:

1.

4. The preparation method according to claim 2, characterized in that, The organic solvent is at least one selected from benzene, toluene, xylene, mesitylene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,2,4-trichlorobenzene.

5. The preparation method according to any one of claims 2 to 4, characterized in that, The ratio of the boron free radical monomer to the organic solvent is 0.03 mol: 5-50 mL.

6. The preparation method according to claim 2, characterized in that, The solvothermal reaction is carried out at a temperature of 80–130°C for 1–5 days.

7. The preparation method according to claim 2, characterized in that, The boron free radical monomer and the pyridine monomer are added to the organic solvent and sonicated for 10-30 minutes, followed by the solvothermal reaction.

8. The preparation method according to claim 2, characterized in that, The cooling process is described as a rate of 1-2°C per hour, with the final temperature being room temperature.

9. The preparation method according to claim 2, characterized in that, After the cooling process is completed, the solid and liquid are separated, the solid is dried, and the free radical polymer single crystal based on boron-nitrogen coordination bonds is obtained.

10. The application of the free radical polymer single crystal based on boron-nitrogen coordination bonds as described in claim 1 in the preparation of organic electronic spin devices, organic field-effect transistor devices, or near-infrared dyes.

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