Method for extracting singlet split triplet electrons and application

Abstract

The invention provides a method for extracting singlet split (SF) triplet electrons and application of the singlet split (SF) triplet electrons. In the invention, a strategy of capturing SF triplet state electrons by constructing a donor-acceptor system (D-A system) is provided, a tetracene derivative with efficient intramolecular SF properties is selected as an electron donor, and a non-fullerene organic small molecule is used as an electron acceptor. The energy level of donor / acceptor molecules is adjusted through structural modification, and a D-A system is constructed in a liquid phase, so that the purpose that non-fullerene small molecules efficiently capture triplet state electrons of tetracene oligomer SF is successfully achieved. The SF triplet state electron capture is simply and efficiently realized, a solid foundation is laid for the application of the SF material in the fields of photoelectric conversion, photocatalysis and the like, and the SF material has a potential application prospect in the aspect of greatly improving the efficiency of photovoltaic devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectrochemistry, and relates to a method and application for extracting singlet fission triplet electrons by using a donor-acceptor system. Background Art

[0002] The incomplete utilization of the solar spectrum is the main reason for the low utilization rate of solar energy. Photon down-conversion can convert high-energy photons in the solar spectrum into multiple low-energy photons that can be absorbed by photovoltaic materials, thereby solving the problem of thermal loss of high-energy photon energy. Singlet fission (SF) is the only way in organic materials that can achieve photon down-conversion. It can achieve the effect of exciton multiplication while reducing the energy of a single photon, so it has the potential to further improve the solar energy utilization efficiency of photovoltaic devices. However, how to quickly and efficiently capture the two triplet excitons generated by SF materials is still the bottleneck of current SF applications.

[0003] The present invention proposes a strategy of constructing a donor-acceptor (D-A) system to capture SF triplet electrons by relying on the Dexter energy transfer mechanism. Constructing a D-A system with efficient electron transfer characteristics and clarifying the triplet electron transfer mechanism between components are of great significance for the construction of an efficient SF system and the efficient capture of triplet excitons. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and application for extracting singlet fission triplet electrons. The present invention proposes that the triplet electrons of singlet fission materials can be captured by constructing a donor-acceptor system (D-A system), and the triplet electrons generated by singlet fission can be collected through an organic acceptor molecule with energy level matching (oxidation / reduction potential matching). The present invention provides a method for extracting singlet fission triplet electrons, which includes:

[0005] Screening out suitable singlet fission materials and electron acceptor molecules and selecting a suitable ratio to blend in a liquid phase to construct a donor-acceptor system, and further characterizing the electron transfer dynamics by transient absorption spectroscopy (TA spectroscopy).

[0006] Preferably, the singlet fission materials include any one or several combinations of tetracene, pentacene, perylene diimide, tetracene dimer, tetracene trimer, pentacene dimer, pentacene trimer, perylene diimide dimer, and derivatives of the above molecules.

[0007] Preferably, the acceptor materials include any one or several combinations of anthraquinone, tetrachlorobenzoquinone, 7,7,8,8-tetracyano-p-benzoquinone dimethane, perylene diimide, and its derivatives.

[0008] Preferably, the donor-receptor molar ratio is 1:(1 - 500).

[0009] Preferably, the liquid phase is one or a combination of benzonitrile, N,N-dimethylformamide, methanol, and acetonitrile.

[0010] The present invention also provides an application for extracting singlet fission triplet electrons.

[0011] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0012] The construction strategy of the donor-receptor system based on SF proposed by the present invention effectively realizes the extraction and application of triplet electrons of singlet fission materials. This method is simple and convenient to operate, laying a solid foundation for the subsequent practical applications of singlet fission materials in the fields of photoelectric conversion and photocatalysis. Description of the Drawings

[0013] In order to more specifically illustrate the technical solutions of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0014] The present invention will be further described below with reference to the drawings.

[0015] Figure 1 It is the nanosecond transient absorption spectrum of the single donor in Example 1;

[0016] Figure 2 It is the femtosecond transient absorption spectrum of the single donor in Example 1;

[0017] Figure 3 It is the nanosecond transient absorption spectrum of the D-A system in Example 1;

[0018] Figure 4 It is the kinetic curve of the triplet exciton of the donor corresponding to whether there is a receptor in Example 1;

[0019] Figure 5 It is the kinetic curve of the triplet exciton of the donor and the receptor in the system of Example 1 (A is the kinetic curve of the triplet of the donor; B is the kinetic curve of the triplet of the receptor). Detailed Embodiments

[0020] The technical solution proposed by the present invention is to construct a donor-acceptor system by using a singlet fission material and an organic acceptor molecule with energy level matching (oxidation / reduction potential matching), and to collect the triplet electrons of the singlet fission material through the construction of the D-A system. The following will further explain the technical solution, its implementation process, principle, etc.

[0021] One aspect of the embodiment of the present invention provides a method for extracting singlet fission triplet electrons, including:

[0022] Screen suitable singlet fission materials and electron acceptor molecules, blend them in a liquid phase system in a suitable ratio to construct a donor-acceptor system, and further characterize the electron transfer kinetics by transient absorption spectroscopy.

[0023] Further, the singlet fission material includes any one or several combinations of tetracene, pentacene, perylene diimide, tetracene dimer, tetracene trimer, pentacene dimer, pentacene trimer, perylene diimide dimer, and derivatives of the above molecules.

[0024] Further, the electron acceptor includes any one or several combinations of anthraquinone, tetrachlorobenzoquinone, 7,7,8,8-tetracyano-p-benzoquinone dimethane, perylene diimide and its derivatives.

[0025] Further, the molar ratio of the donor-acceptor blend is 1:(1 - 500).

[0026] Further, the liquid phase is one or several combinations of benzonitrile, N,N-dimethylformamide, methanol, and acetonitrile.

[0027] To better explain the purpose and characteristics of the present invention, the technical solution of the present application will be described in more detail below with reference to the accompanying drawings and several embodiments. However, it should be noted that the content of the following embodiments is illustrative and not a limiting implementation manner, and does not limit the scope of the present application. Unless otherwise specified, various raw materials, reaction methods, etc. used in the following embodiments are known in the art.

[0028] The present invention will be described in detail below with several specific cases.

[0029] Example 1:

[0030] Typically, an intermolecular electron donor-acceptor system composed of a tetracene derivative and a perylene diimide derivative is constructed to capture the triplet electrons generated by singlet fission. In this example, by chemically modifying tetracene and perylene diimide, while ensuring the intramolecular singlet fission efficiency of the donor, the energy levels of the two are regulated to achieve energy level matching, thereby realizing the effective capture of triplet electrons, and demonstrating the potential prospects of singlet fission in the application field.

[0031] The technical solution for synthesizing the receptor in this embodiment is as follows:

[0032]

[0033] a. Weigh 0.2 g (0.364 mmol) of compound (1), 0.23 g (1.156 mmol) of 2,2,3,3,4,4,4-heptafluorobutylamine, and 1.360 g (2.267 mmol) of acetic acid into a Schlenk tube. Add 7.6 mL of 1-methyl-2-pyrrolidone, and react at 90 °C for 7 h under a nitrogen atmosphere. After the reaction is completed, add a large amount of methanol, let it stand and freeze overnight, then perform suction filtration and washing to obtain a red crude product. Purify it by column chromatography using dichloromethane / n-hexane = 4 / 1 (v / v) as the eluent. Recrystallize the product with dichloromethane and methanol, and dry it to obtain 0.1321 g of a red solid, with a yield of 39.3%.

[0034] b. Weigh 0.1 g (0.125 mmol) of compound (2), 128.68 mg (1.096 mmol) of zinc cyanide, 9.11 mg (0.164 mmol) of 1,1'-bis(diphenylphosphino)ferrocene, and 15.05 mg (0.0210 mmol) of tris(dibenzylideneacetone)dipalladium into a Schlenk tube and perform three evacuations and three connections. Then add 20 mL of deoxygenated and dehydrated 1,4-dioxane. React at 100 °C for 8 h under a nitrogen atmosphere, then extract the reaction solution with distilled water and dichloromethane, retain the organic phase, dry it, and purify it by column chromatography (using n-hexane / ethyl acetate = 3 / 2, v / v, as the eluent). Then recrystallize it with dichloromethane and methanol, and dry it to obtain 60.24 mg of a red solid compound (3), with a yield of 60.1%. Abbreviated as PDICN2 in the attached drawings.

[0035] The technical solution for synthesizing the donor in this embodiment is as follows:

[0036]

[0037]

[0038] a. Add 1,4-naphthoquinone (1.6 g, 10.0 mmol), 4-pentabromoisophthalic acid dimethyl ester (5.0 g, 10.0 mmol), and potassium iodide (6.5 g, 40 mmol) into a three-necked flask. After performing three evacuations and three connections, add 120 mL of dehydrated and deoxygenated DMF. Heat the mixture at 110 °C for 18 hours. After the reaction is completed, cool the mixture to room temperature, pour it into a large amount of methanol, and then filter. Then wash the solid and dry it to obtain 3.032 g of a shiny golden-yellow solid, with a yield of 88.5%.

[0039] b. After performing three evacuations and three-way cocks in a three-necked flask, successively add 40 mL of dehydrated and deoxygenated THF, isopropylmagnesium chloride (4.5 mL, 9 mmol), and triisopropylsilylacetylene (2.12 g, 10.8 mmol). First, heat at 60 °C for 1 hour and then cool to room temperature. Then add the product obtained in step a (500 mg, 1.49 mmol), continue to react at 60 °C for 6 hours, cool to room temperature, and add an aqueous hydrochloric acid solution (10%, 12.5 mL) dissolved with stannous chloride (2.68 g, 14.14 mmol). Then extract with distilled water and dichloromethane and retain the organic phase. After drying, purify by column chromatography (using n-hexane as the eluent), recrystallize with dichloromethane and methanol, and dry to obtain 350.25 mg of a red solid with a yield of 52.4%.

[0040] c. Add the compound synthesized in step b (200 mg, 0.3 mmol), bis(pinacolato)diboron (228 mg, 0.9 mmol), KOAC (147 mg, 1.5 mmol), and the catalyst Pd(dppf)Cl2 (22 mg, 0.03 mmol) to a three-necked flask, perform three evacuations and three-way cocks, then add 20 mL of dehydrated and deoxygenated 1,4-dioxane. The mixture reacts at 90 °C for 24 hours. After the reaction, extract with distilled water and dichloromethane and retain the organic phase. After drying, purify by column chromatography (the eluent is n-hexane / dichloromethane = 3 / 1, v / v), recrystallize with dichloromethane and methanol, and dry to obtain 150.08 mg of a red solid with a yield of 66.7%.

[0041] d. Add the red compound obtained in step c (100 mg, 0.14 mmol), 1,3,5-tribromobenzene (11 mg, 0.035 mmol), K2CO3 (32.4 mg, 0.14 mmol), and Pd(dppf)Cl2 (3.7 mg, 0.005 mmol) to a three-necked flask, perform three evacuations and three-way cocks, then add 10 mL of deoxygenated solvent (THF / H2O = 9 / 1, v / v). The mixture reacts at 70 °C for 24 hours. After the reaction, extract with distilled water and dichloromethane and retain the organic phase. After drying, purify by column chromatography (the eluent is n-hexane / dichloromethane = 3 / 1, v / v), recrystallize with dichloromethane and methanol, and dry to obtain 82.16 mg of the compound of formula (4) with a yield of 31.8%. Abbreviated as TC3 in the attached figure.

[0042] Dissolve the obtained donor (TC3) and acceptor (PDICN2) in benzonitrile at a ratio of 1 / 10 to construct a D-A system.

[0043] Furthermore, through the study of the attached drawings, it can be found that: in the TA spectrum of a single donor, short-lived pentacene singlet signals and long-lived pentacene triplet signals appear in sequence, proving that singlet fission has occurred in the donor. Moreover, it can be further found that in the D-A system, singlet fission still occurs in the donor to generate triplets, and the lifetime of the triplets generated by the donor in the D-A system is significantly shorter than that of the triplets in the single donor. At the same time, along with the attenuation of the donor triplet signal, the anion signal of the acceptor appears to increase. From this, it can be concluded that: the acceptor we synthesized successfully captures the triplet excitons generated by the singlet fission of the donor in the form of electron transfer.

[0044] The beneficial effect of this embodiment is that by modifying perylene diimide and pentacene, while achieving the energy level matching of perylene diimide derivatives and pentacene derivatives, the singlet fission efficiency of pentacene derivatives is ensured, so that triplet electrons can be effectively captured to achieve the goal of improving the solar energy utilization efficiency.

[0045] Example 2:

[0046] Select a pentacene dimer as the donor and the perylene diimide derivative in Example 1 as the acceptor, and dissolve them in N,N-dimethylformamide at a donor / acceptor ratio of 1 / 12 to form a donor-acceptor system. The compounds in the examples are obtained by commercial purchase or laboratory synthesis. The results of transient absorption spectroscopy are similar to those in Example 1. High-efficiency SF occurs in the pentacene dimer, and its SF triplet electrons can be efficiently captured in the presence of the acceptor.

[0047]

[0048] Example 3:

[0049] Select the pentacene trimer in Example 1 as the donor and 7,7,8,8-tetracyano-p-benzoquinodimethane as the acceptor, and dissolve them in benzonitrile at a donor / acceptor ratio of 1 / 10 to form a donor-acceptor system. The compounds in the examples are obtained by commercial purchase or laboratory synthesis. The results of transient absorption spectroscopy are similar to those in Example 1. High-efficiency SF occurs in the pentacene dimer, and its SF triplet electrons can be efficiently captured in the presence of the acceptor.

[0050]

[0051] Example 4:

[0052] Select the same donor and acceptor as in Example 1, with a donor / acceptor ratio of 1 / 15, and change the solvent to methanol to form a donor-acceptor system. The results of transient absorption spectroscopy are similar to those in Example 1. High-efficiency SF successfully occurs in the donor, and its SF triplet electrons can be efficiently captured in the presence of the acceptor.

[0053] Through the photophysical characterization of Example 2, Example 3, and Example 4, results that are basically similar to those of Example 1 were obtained, proving the universality of the strategy for capturing the triplet electrons of SF by the donor-acceptor system provided by the present invention.

[0054] In summary, the strategy we selected for constructing the donor-acceptor system has successfully achieved the efficient capture of the triplet electrons of SF, and the experimental results of the above examples show a high degree of similarity, all proving that the acceptor molecules we selected effectively captured the triplet electrons of the donor. Thus, we conclude that the strategy of using the donor-acceptor system with intermolecular electron transfer has universality. By selecting appropriate triplet electron donors and acceptors, the goal of efficiently capturing the triplet electrons of SF can be effectively achieved, demonstrating the potential prospects of SF materials in the applications such as photoelectric conversion and photocatalysis.

[0055] The above description is only a preferred embodiment of the present invention and cannot be used to limit the protection scope of the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention all fall within the scope of the technical solution of the present invention.

Claims

1. A method for extracting singlet fission triplet electrons: A singlet fission material with energy level matching (oxidation / reduction potential matching) and an electron acceptor molecule are blended in a liquid phase in an appropriate ratio to construct a donor-acceptor system, and the electron transfer kinetics is further characterized by transient absorption spectroscopy.

2. The method according to claim 1, characterized in that: The singlet fission material includes any one or several combinations of tetracene, pentacene, perylene diimide, tetracene dimer, tetracene trimer, pentacene dimer, pentacene trimer, perylene diimide dimer, and derivatives of the above molecules.

3. The method according to claim 1, characterized in that: The acceptor material includes any one or several combinations of anthraquinone, tetrachlorobenzoquinone, 7,7,8,8-tetracyano-p-benzoquinone dimethane, perylene diimide, and its derivatives.

4. The method according to claim 1, wherein: The molar ratio of the donor-acceptor blend is 1:(1 - 500).

5. The method according to claim 1, characterized in that: The liquid phase is one or several combinations of benzonitrile, N,N-dimethylformamide, methanol, and acetonitrile.

6. Use of the method for extracting singlet fission triplet electrons according to any one of claims 1 - 5 in the fields of photovoltaic devices, photocatalysis, and photodynamic therapy.

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