Four-component metal-organic cages based on perylene diimide and terphenyl, their preparation methods and photocatalytic applications

Abstract

The application discloses a four-component metal organic cage based on perylene diimide and terphenyl as well as a preparation method and photocatalytic application thereof, and belongs to the technical field of supramolecular chemistry. The metal organic cage is based on a method of transition metal coordination driven self-assembly, inter-ligand shape complement strategy and molecular docking, and discloses a series of four-component metal organic cages based on perylene diimide and p-terphenyl pyridine ligands which are asymmetric in space structure. The functional integration of the pyridine ligands in the metal cage can realize the charge transfer in the multi-component metal organic cage, so that the application of photocatalytic oxidation reaction can be realized.

Description

Technical Field

[0001] This invention belongs to the field of supramolecular chemistry technology, specifically relating to a four-component metal-organic cage based on perylene diimide and terphenyl, its preparation method, and its photocatalytic application. Background Technology

[0002] One of the challenging and important challenges in photocatalytic oxidation reactions is the efficient and selective oxidation of sulfides to sulfoxides under mild reaction conditions, thus avoiding the formation of toxic sulfones and other byproducts. This is crucial because sulfoxides play a vital role in organic synthesis, pharmaceuticals, and polymers. Some sulfoxides, such as those found in drugs like omeprazole and sulindac, exhibit remarkable pharmacological properties. Current sulfoxide synthesis methods typically involve the use of multiple oxidants, leading to excessive waste and challenges in selectivity, with the potential formation of unwanted sulfones. Furthermore, many existing schemes require high temperatures. In this regard, it is attractive to develop a self-assembling cage with a unique geometry that uses functional ligands to selectively photooxidize sulfides to sulfoxides in high yields under both aerobic and organic conditions.

[0003] Due to their moderate bond strength and specific orientation of coordination bonds, metal coordination-driven self-assembly can efficiently construct multi-component supramolecular coordination complexes. As a subset of multi-component supramolecular coordination complexes, metal cages, characterized by their well-defined three-dimensional structures and enormous functionalization potential, have attracted increasing attention in a range of applications. However, most metal cages utilize a limited range of organic ligands, typically involving a single metal and ligand, which leads to reduced structural diversity and functional integration compared to the highly complex self-assembly systems observed in biological processes. In recent years, Fujita, Stang, Clever, Nitschke, and other authors have conducted pioneering research on multi-component metal cages. Strategies such as template effects, charge separation, shape complementarity, and subcomponent self-assembly have been effectively used to construct multi-component metal cages. However, further increasing the number of components significantly exacerbates the challenges of constructing multi-component metal cages. This difficulty is mainly due to the increasingly complex interactions between different ligands, which may lead to the formation of multiple structures during self-assembly, thus reducing the likelihood of achieving a single target structure. Furthermore, in multi-component metal cage systems, thermodynamic stability and kinetic pathways may be inconsistent, resulting in competing products driven by thermodynamic and kinetic factors. Therefore, multi-component metal cages with more than three organic ligands remain rare. Furthermore, although the self-assembly process of multi-component metal cages has been clearly investigated in the aforementioned studies, the relationship between structural changes caused by the added components and their resulting functions has not been thoroughly explored. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a four-component metal-organic cage based on perylene diimide and terphenyl, its preparation method and photocatalytic application, so as to solve the problems of size matching, functional integration, charge transfer and selective photocatalytic oxidation of methyl phenyl sulfide in multi-component metal cages in the prior art.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A four-component metal-organic cage based on perylene diimide and terphenyl has the following structural formula:

[0007]

[0008] A method for preparing the above-mentioned four-component metal-organic cage based on perylene diimide and terphenyl includes the following steps: dissolving tetrapyridylperylene diimide ligand, tetrapyridylterphenyl ligand, tetradentate sodium carboxylate ligand and cisplatin metal ligand in a mixed solvent; subjecting the mixed system to ultrasonic treatment and stirring; obtaining the reaction product through a self-assembly reaction; and obtaining a cavity-based metal-organic cage based on perylene diimide and terphenyl after purifying the reaction product.

[0009] Preferably, the tetrapyridylperylene diimide ligand is 4,7,11,14-tetra(4-pyridyl)perylene diimide.

[0010] Preferably, the tetrapyridyl terphenyl ligand is any one of tetrapyridyl terphenyl-benzene, tetrapyridyl terphenyl-anthracene, or tetrapyridyl terphenyl-methoxy.

[0011] Preferably, the cisplatin metal ligand is cis-bis(triethylphosphine)bis(trifluoromethanesulfonic acid)platinum(II).

[0012] Preferably, the tetradentate sodium carboxylate ligand is 4'-(4,7-bis(3-carboxyphenyl)-1H-benzo[d]imidazol-2-yl)-[1,1'-biphenyl]-3,5-dicarboxylate sodium.

[0013] Preferably, the preparation process of the sodium 4'-(4,7-bis(3-carboxyphenyl)-1H-benzo[d]imidazol-2-yl)-[1,1'-biphenyl]-3,5-dicarboxylate includes the following steps:

[0014] (1) Compound 1 is generated by the reaction of 4,7-dibromo-2,3-benzothiadiazole, 3-ethoxycarbonylphenylboronic acid, tetratriphenylphosphine palladium and Cs2CO3;

[0015] (2) Compound 1 was dissolved in a mixed solution of THF and EtOH, and NaBH4 and CoCl2·6H2O were added and reacted. The mixture was extracted with brine and DCM. The extract was mixed with 4-bromobenzaldehyde and ZrCl4 and recrystallized to obtain compound 2.

[0016] (3) Compound 3 is generated by reacting a mixture of compound 2, 4-bromobenzaldehyde, ZrCl4, tetratriphenylphosphine palladium, and Cs2CO3.

[0017] (4) After mixing compound 3, potassium hydroxide, THF and water, the mixture was refluxed. HCl was added dropwise to the reflux solution to obtain compound 4.

[0018] (5) Dissolve compound 4 and sodium hydroxide in water and precipitate the solid through acetone to obtain sodium 4'-(4,7-bis(3-carboxyphenyl)-1H-benzo[d]imidazol-2-yl)-[1,1'-biphenyl]-3,5-dicarboxylic acid.

[0019] Preferably, the molar ratio of the tetrapyridylperylene diimide ligand, the tetrapyridylterphenyl ligand, the tetradentate sodium carboxylate ligand, and the cisplatin metal ligand is 1:1:2:8.

[0020] Preferably, the stirring process is carried out at a temperature of 55°C for 12 hours.

[0021] An application of the above-mentioned four-component metal-organic cage based on perylene diimide and terphenyl is used as a photocatalyst for photocatalytic oxidation reactions;

[0022] The photocatalytic oxidation can generate singlet oxygen, which is used to oxidize methyl phenyl sulfide.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention discloses a four-component metal-organic cage based on perylene diimide and terphenylpyridine ligands. This metal-organic cage utilizes transition metal coordination-driven self-assembly, a ligand shape complementarity strategy, and molecular docking methods, disclosing a series of spatially asymmetric four-component metal-organic cages based on perylene diimide and terphenylpyridine ligands. The functional integration of pyridine ligands within this metal cage enables charge transfer within the multi-component metal-organic cage cavity, facilitating photocatalytic oxidation reactions. Therefore, the metal-organic cage formed by combining methoxy- and anthracene-modified p-terphenyl as an electron donor with perylene diimide as an electron acceptor can promote charge separation and charge transfer under illumination. Furthermore, the metal-organic cage can generate singlet oxygen under illumination, thereby oxidizing methyl phenyl sulfide to methyl phenyl sulfoxide. This invention provides a strategy for incorporating multifunctional pyridine ligands into metal-organic cages for photocatalytic oxidation, which will contribute to the development of functional integration of pyridine ligand molecules, strategies for preparing multi-component metal-organic cages, and the application of metal-organic cages in photocatalysis.

[0025] This invention also discloses a method for preparing a four-component organometallic cage based on perylene diimide and terphenyl. The organic cage is prepared from a tetrapyridylperylene diimide ligand, a tetrapyridylterphenyl ligand, a tetradentate sodium carboxylate ligand, and a cisplatin metal ligand. During this preparation process, the sodium ion in the tetradentate sodium carboxylate ligand dissociates in solution. The cisplatin metal ligand Pt(PEt3)2(OTf)2 loses two trifluoromethanesulfonate anions in solution and then self-assembles with the N atom in the pyridine group of the tetrapyridylperylene diimide and the tetrapyridylterphenyl ligand, and the O atom on the tetradentate carboxylate via metal-organic coordination, respectively, to form the target four-component organometallic cage. The detached trifluoromethanesulfonate ions serve as counterions around the Pt metal sites of the metal cage. This method can prepare four-component metal-organic cages based on perylene diimide and terphenyl with a yield of up to 90%. The preparation steps are simple, the raw materials are inexpensive and readily available, the products are easy to purify, and the yield is high.

[0026] This invention also discloses the application of a four-component metal-organic cage based on perylene diimide and terphenyl. The luminescent metal-organic cage is assembled from a tetrapyridylperylene diimide ligand, a tetrapyridylterphenyl ligand, a tetradentate sodium carboxylate ligand, and cisplatin. After absorbing photons, the tetrapyridylterphenyl ligand acts as an electron donor, transferring electrons to the tetrapyridylperylene diimide ligand, resulting in charge transfer and the formation of perylene diimide anion radicals. Furthermore, the four-component metal cage can undergo energy transfer under illumination to generate singlet oxygen, which can then undergo sulfide oxidation reactions. The prepared four-component organometallic cage has a well-defined cavity and can convert oxygen into singlet oxygen under illumination through energy transfer, selectively oxidizing methyl phenyl sulfide to methyl phenyl sulfoxide, thus artificially preparing a photocatalytic oxidation system. Attached Figure Description

[0027] Figure 1 The flowchart for preparing a four-component metal-organic cage based on perylene diimide and terphenyl is shown below.

[0028] Figure 2 This is a synthetic route diagram of the four-component metal-organic cage 5a based on perylene diimide and terphenyl prepared in Example 1;

[0029] Figure 3 The four-component metal-organic cage 5a based on perylene diimide and terphenyl prepared in Example 1 1 HNMR spectrum;

[0030] Figure 4 The four-component metal-organic cage 5a based on perylene diimide and terphenyl prepared in Example 1 31 PNMR plot;

[0031] Figure 5 Synthetic route diagram of the four-component metal-organic cage 5b based on perylene diimide and terphenyl prepared in Example 2;

[0032] Figure 6 The four-component metal-organic cage 5b based on perylene diimide and terphenyl prepared in Example 2 1 HNMR spectrum;

[0033] Figure 7 The four-component metal-organic cage 5b based on perylene diimide and terphenyl prepared in Example 2 31 PNMR plot;

[0034] Figure 8 This is a synthetic route diagram of the four-component metal-organic cage 5c based on perylene diimide and terphenyl prepared in Example 3;

[0035] Figure 9 The four-component metal-organic cage 5c based on perylene diimide and terphenyl prepared in Example 3 1 HNMR spectrum;

[0036] Figure 10 The four-component metal-organic cage 5c based on perylene diimide and terphenyl prepared in Example 3 31 PNMR plot;

[0037] Figure 11 Crystal structure diagrams of the four-component metal-organic cages based on perylene diimide and terphenyl prepared in Examples 1-3;

[0038] Figure 12 The UV absorption spectra of the four-component metal-organic cages based on perylene diimide and terphenyl prepared in Examples 1-3 are shown.

[0039] Figure 13 The fluorescence emission spectra of the four-component metal-organic cages based on perylene diimide and terphenyl prepared in Examples 1-3 are shown.

[0040] Figure 14 The fluorescence lifetime of the four-component metal-organic cages based on perylene diimide and terphenyl prepared in Examples 1-3;

[0041] Figure 15 Electron paramagnetic resonance (EPR) spectra of the four-component metal-organic cages based on perylene diimide and terphenyl prepared in Examples 1-3;

[0042] Figure 16 Electrochemical impedance spectroscopy of the four-component metal-organic cages based on perylene diimide and terphenyl prepared in Examples 1-3;

[0043] Figure 17 Photocurrent testing of the four-component metal-organic cage based on perylene diimide and terphenyl prepared in Examples 1-3;

[0044] Figure 18 The transient absorption spectra of the four-component metal-organic cage based on perylene diimide and terphenyl prepared in Examples 1-3 are shown.

[0045] Figure 19 The transient absorption spectra of the four-component metal-organic cage based on perylene diimide and terphenyl prepared in Examples 1-3 are shown.

[0046] Figure 20 The image shows the decay fitting curves of perylene diimide anion free radicals based on perylene diimide and terphenyl prepared in Examples 1-3.

[0047] Figure 21 Calculations of HOMO-LUMO levels for the four-component metal-organic cage based on perylene diimide and terphenyl prepared in Examples 1-3;

[0048] Figure 22 The synthetic routes for anisole in Examples 1-3 are shown below;

[0049] Figure 23 The conversion rate of anisole in Examples 1-3;

[0050] Figure 24 The yields of anisole in Examples 1-3;

[0051] Figure 25 The changes in absorbance at 372 nm of DPHA (c = 150 μM) in Examples 1-3 under the action of TPP (c = 10 μM) and a four-component metal cage (c = 10 μM);

[0052] Figure 26 The 1H NMR spectra of the process products during the preparation of tetradentate sodium carboxylate ligands in Examples 1-3 are shown.

[0053] Figure 27 The 1H NMR spectra of the process products during the preparation of tetradentate sodium carboxylate ligands in Examples 1-3 are shown.

[0054] Figure 28 The NMR spectra of the sodium tetradentate carboxylate ligands in Examples 1-3 are shown in the 1H NMR spectrum. Detailed Implementation

[0055] The present invention will now be described in further detail with reference to the accompanying drawings:

[0056] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0057] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0058] The present invention will be further illustrated below with reference to 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. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0059] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0060] like Figure 1-10 As shown, the first aspect of this invention discloses a four-component metal-organic cage based on perylene diimide and terphenyl, wherein the metal-organic cage is composed of a tetrapyridine perylene diimide ligand, a tetrapyridyl terphenyl ligand, a tetradentate sodium carboxylate ligand, and a cisplatin metal ligand. The structural formula of the metal-organic cage is as follows:

[0061]

[0062] The second aspect of this invention discloses a method for preparing a four-component metal-organic cage based on perylene diimide and terphenyl. The preparation method includes the following steps: dissolving a tetrapyridylperylene diimide ligand and a tetrapyridylterphenyl ligand with a tetradentate sodium carboxylate ligand and a cisplatin metal ligand in a mixed solvent of acetonitrile and water; ultrasonically treating the mixture and transferring it to a constant-temperature metal bath for stirring; and purifying the product obtained through self-assembly to obtain a four-component metal-organic cage with cavities based on perylene diimide and terphenyl.

[0063] As a preferred embodiment, the tetrapyridylperylene diimide ligand is 4,7,11,14-tetra(4-pyridyl)perylene diimide, with the following structural formula:

[0064]

[0065] As a preferred embodiment, the tetrapyridyl terphenyl ligand is any one of tetrapyridinyl-p-terphenyl-benzene, tetrapyridinyl-p-terphenyl-anthracene, and tetrapyridinyl-p-terphenyl-methoxy, with the following structural formulas:

[0066]

[0067] As a preferred embodiment, the tetradentate sodium carboxylate ligand is 4'-(4,7-bis(3-carboxyphenyl)-1H-benzo[d]imidazol-2-yl)-[1,1'-biphenyl]-3,5-dicarboxylate sodium, with the following structural formula:

[0068]

[0069] Because the molecule utilizes a shape-matching strategy, the sodium m-phenylcarboxylate moiety (top of the molecule) can coordinate with the tetrapyridylperylene diimide ligand, while the sodium terphenylcarboxylate moiety (bottom of the molecule) can coordinate with the tetrapyridylterphenyl ligand. This molecule acts as a good bridge, allowing multiple pyridine ligands to bind in a metal cage, thus achieving the binding of multiple functional pyridine ligands.

[0070] The specific preparation process of this substance is as follows:

[0071]

[0072] Specifically, the following steps are included:

[0073] (1) 4,7-Dibromo-2,3-benzothiadiazole (1.60 g, 5.45 mmol), 3-ethoxycarbonylphenylboronic acid (2.75 g, 14.18 mmol), tetrakis(triphenylphosphine)palladium (630.05 mg, 0.54 mmol), and Cs₂CO₃ (5.33 g, 16.36 mmol) were added to a 250 mL Schlenk flask. The solution was degassed and purged with N₂. DMF (60 mL) and toluene (60 mL) were added, and the solution was refluxed (110 °C) for 24 hours. After cooling to room temperature, the crude product was purified by column chromatography on silica gel to give a pale yellow compound 1 (yield: 2.24 g, 95%). The proton NMR spectrum data are as follows: 1 H NMR (600MHz, CDCl3, 295K): δ8.62(t,J=1.8Hz,2H), 8.21(dt,J=7.8,1.5Hz,2H), 8.15(dt,J=7. 8,1.4Hz,2H),7.86(s,2H),7.64(t,J=7.8Hz,2H),4.44(q,J=7.1Hz,4H),1.43(t,J=7.2Hz,6H).

[0074] (2) Compound 1 (2 g, 4.6 mmol) was dissolved in THF / EtOH (1:3, 160 mL). NaBH4 (690 mg, 18.4 mmol) was added in portions. CoCl2·6H2O (50 mg, 0.21 mmol) was added. The resulting black mixture was refluxed for 4 hours. The mixture was cooled to room temperature and then filtered. The filtrate was concentrated and extracted with brine and DCM. Excess 4-bromobenzaldehyde and ZrCl4 (30.12 mg, 129.26 μmol) were added and stirred for 24 h. The solvent was then evaporated to dryness. Recrystallization from DCM / PE yielded compound 2 as a white solid (617 mg, 84% yield). The 1H NMR spectrum data are as follows: 1 H NMR (600MHz, CDCl3, 295K): δ9.78(s,1H),8.83(d,J=1.8Hz,1H),8.42–8.39(m,1H),8.34(t,J=1.8Hz,1H),8.11(d,J=7.5Hz,1H),8.07(d,J= 7.8Hz,1H),7.98–7.95(m,2H),7.86–7.84(m,1H),7.66–7.57(m,5H),7.41(d,J=7.7Hz,1H),4.46–4.40(m,4H),1.44(dt,J=9.9,7.1Hz,6H).

[0075] (3) Compound 2 (174 mg, 305.56 μmol), 3,5-dimethoxycarboxyphenylboronic acid (121.94 mg, 458.33 μmol), tetrakis(triphenylphosphine)palladium (35.31 mg, 30.56 μmol), and Cs₂CO₃ (298.67 mg, 916.67 μmol) were added to a 250 mL Schlenk flask. The solution was degassed and purged with N₂. DMF (60 mL), toluene (60 mL), and water (15 mL) were added, and the solution was refluxed (110 °C) for 24 hours. After cooling to room temperature, the crude product was purified by column chromatography on silica gel to give a white compound 3 (177 mg, yield 81%). The proton NMR spectrum data are as follows: 1 H NMR (600MHz, CDCl3, 295K): δ10.01(s,1H),8.87(s,1H),8.67(t,J=1.5Hz,1H),8.49(d,J=1.6Hz,3H),8.39(s,1H),8.23(d,J=8.0Hz,2H) ,8.11(s,2H),8.00(s,1H),7.90(s,1H),7.78(d,J=8.0Hz,2H),7.63(s,2H),7.44(s,1H),4.45(p,J=7.0Hz,8H),1.45(t,J=7.0Hz,12H), such as Figure 26 As shown.

[0076] (4) Compound 3 (177 mg, 249.02 μmol) and potassium hydroxide (223.54 mg, 3.98 mmol) were added to a 100 mL Schlenk flask. THF (20 mL) and water (10 mL) were added, and the solution was refluxed (70 °C) for 12 hours. After cooling the solution to room temperature, HCl was added dropwise to give a dark brown product, compound 4 (101 mg, yield 68%). The proton NMR spectrum data are as follows: 1 H NMR (600MHz, DMSO, 295K): δ13.33(s,4H),8.50(dd,J=9.0,1.6Hz,4H),8.46(d,J=8.2Hz,2H),8 .24(s,2H),8.05(d,J=7.8Hz,2H),7.99(d,J=8.1Hz,2H),7.73(t,J=7.7Hz,2H),7.54(s,2H), such as Figure 27 As shown.

[0077] (5) Compound 4 (101 mg, 168.74 μmol) and sodium hydroxide (28.35 mg, 708.69 μmol) were added to an aqueous solution. After complete dissolution at room temperature, acetone was added to precipitate a solid, yielding a white product 5 (90 mg, yield 78%). The proton NMR spectrum data are as follows: 1 H NMR (600MHz, D2O, 295K): δ8.14(t,J=1.7Hz,0H),8.07(s,1H),7.98(s,1H),7.79(dd,J=17.3 ,7.8Hz,2H),7.66–7.62(m,1H),7.51(d,J=8.0Hz,1H),7.47(t,J=7.7Hz,1H),7.14(s,1H), such as Figure 28 As shown.

[0078] As a preferred embodiment, the cisplatin metal ligand is cis-bis(triethylphosphine)bis(trifluoromethanesulfonic acid)platinum(II), with the following structural formula:

[0079]

[0080] OTf:

[0081] PEt3:

[0082] As a preferred embodiment, tetrapyridylperylene diimide ligand, tetrapyridylterphenyl ligand, tetradentate sodium carboxylate ligand and cisplatin metal ligand are weighed and mixed in a molar ratio of 1:1:2:8, and a mixed solvent of acetonitrile and water is added to obtain a mixed solution, wherein the volume ratio of acetonitrile to water is 4:1.

[0083] As a preferred method, the mixed solution is sonicated and then placed in a metal bath for constant temperature stirring to obtain a product solution through multi-component self-assembly. The constant temperature stirring temperature of the reaction solution is 55℃, and the reaction time is 12h.

[0084] As a preferred embodiment, the reaction product is purified to obtain a four-component metal-organic cage based on perylene diimide and terphenyl. The purification process involves removing the solvent, re-dissolving the product, filtering, recrystallizing, centrifuging, and drying to obtain the four-component metal-organic cage based on perylene diimide and terphenyl.

[0085] The solvent removal method is: N2 drying and vacuum rotary evaporation, preferably, N2 drying.

[0086] As one of the preferred solutions, the solvent for redissolution is acetonitrile or acetone, and more preferably, acetonitrile is used as the solvent for redissolution.

[0087] As one preferred method, the solution is to recrystallize the filtered material using diethyl ether or isopropyl ether solvent. Preferably, the solution is to recrystallize the material using diethyl ether.

[0088] As one of the preferred methods, the obtained precipitate is centrifuged and then vacuum dried at 80°C for 12 hours.

[0089] The third aspect of the present invention discloses an application of the above-mentioned four-component metal-organic cage based on perylene diimide and terphenyl, wherein the metal-organic cage is capable of energy transfer to generate active oxygen species, namely singlet oxygen, and the oxidation reaction of methyl phenyl sulfide is achieved through singlet oxygen.

[0090] One embodiment of the present invention discloses a method for preparing a four-component metal-organic cage based on perylene diimide and terphenyl. Tetrapyridylperylene diimide ligand and tetrapyridylterphenyl ligand are dissolved with tetradentate sodium carboxylate ligand and cisplatin metal ligand in a mixed solvent of acetonitrile and water. The mixture is ultrasonically treated for 30 seconds and then transferred to a constant-temperature metal bath for stirring. The product obtained through self-assembly is purified to obtain a four-component metal-organic cage with a cavity structure based on perylene diimide and terphenyl.

[0091] like Figure 22 As shown, the four-component metal-organic cage based on perylene diimide and terphenyl synthesized in this invention is used as a photocatalyst for oxidation reactions. The specific process is as follows:

[0092] Take a 10 mL glass bottle and add the anisole substrate, standard, four-component metal cage (1% mol), deuterated acetonitrile, and magnetic ball into the bottle. Fill the bottle with oxygen and calculate the conversion rate and yield of anisole at different time periods under 520 nm light irradiation.

[0093] The following description, in conjunction with specific embodiments, provides further details.

[0094] Example 1

[0095] See Figure 2 This embodiment discloses a method for preparing a four-component metal-organic cage based on perylene diimide and terphenyl, including the following steps:

[0096] (1) Weigh and mix 4,7,11,14-tetra(4-pyridyl)perylene diimide (3.26 mg, 3.64 μmol), tetrapyridine-p-terphenyl-benzene (1.96 mg, 3.64 μmol), 4'-(4,7-bis(3-carboxyphenyl)-1H-benzo[d]imidazol-2-yl)-[1,1'-biphenyl]-3,5-dicarboxylate sodium (5 mg, 7.28 μmol) and cis-di(triethylphosphine)bis(trifluoromethanesulfonic acid)platinum(II) (21.25 mg, 29.13 μmol) in a molar ratio of 1:1:2:8, and dissolve them in a mixed solvent of acetonitrile / water (7.5 ml, 4:1, v / v) to obtain a mixed solution.

[0097] (2) After sonicating the mixed solution for 30 seconds, place it in a metal bath at a constant temperature of 55°C and stir for 12 hours. Then cool it to room temperature to obtain the product solution.

[0098] (3) The solvent was removed by drying with nitrogen gas flow. The residue was dissolved and filtered with acetonitrile (2.0 mL). Diethyl ether (8.0 mL) was added to precipitate the residue. After centrifugation, the residue was vacuum dried at 60 °C for 12 h to collect the four-component metal-organic cage based on perylene diimide and terphenyl. The four-component metal-organic cage 5a can be prepared through this example.

[0099] The product prepared in this embodiment 1 H NMR spectrum and 31 The p NMR spectra are as follows: Figure 3 and Figure 4 As shown.

[0100] (4) Take a 10 mL glass bottle, add the anisole substrate, standard, four-component metal cage (1% mol), deuterated acetonitrile and magnetic ball into the bottle, fill with oxygen, and calculate the conversion rate and yield of anisole under 520 nm light irradiation at different time periods.

[0101] Example 2

[0102] Referring to 5, this embodiment discloses a method for preparing a four-component metal-organic cage based on perylene diimide and terphenyl, including the following steps:

[0103] (1) Weigh and mix 4,7,11,14-tetra(4-pyridyl)perylene diimide (3.26 mg, 3.64 μmol), tetrapyridine-p-terphenyl-anthracene (2.33 mg, 3.64 μmol), 4'-(4,7-bis(3-carboxyphenyl)-1H-benzo[d]imidazol-2-yl)-[1,1'-biphenyl]-3,5-dicarboxylate sodium (5 mg, 7.28 μmol) and cis-bis(triethylphosphine)bis(trifluoromethanesulfonic acid)platinum(II) (21.25 mg, 29.13 μmol) in a molar ratio of 1:1:2:8, and dissolve them in a mixed solvent of acetonitrile / water (7.5 ml, 4:1, v / v) to obtain a mixed solution.

[0104] (2) After sonicating the mixed solution for 30 seconds, place it in a metal bath at a constant temperature of 55°C and stir for 12 hours. Then cool it to room temperature to obtain the product solution.

[0105] (3) The solvent was removed by drying with nitrogen gas flow. The residue was dissolved and filtered with acetonitrile (2.0 mL). Diethyl ether (8.0 mL) was added to precipitate the residue. After centrifugation, the residue was vacuum dried at 60 °C for 12 h to collect the four-component metal-organic cage based on perylene diimide and terphenyl. Metal-organic cage 5b can be prepared through this example.

[0106] The product prepared in this embodiment 1 H NMR spectrum and 31 The p NMR spectra are as follows: Figure 6 and Figure 7 As shown.

[0107] (4) Take a 10 mL glass bottle, add the anisole substrate, standard, four-component metal cage (1% mol), deuterated acetonitrile and magnetic ball into the bottle, fill with oxygen, and calculate the conversion rate and yield of anisole under 520 nm light irradiation at different time periods.

[0108] Example 3

[0109] See Figure 8 This embodiment discloses a method for preparing a four-component metal-organic cage based on perylene diimide and terphenyl, including the following steps:

[0110] (1) Weigh and mix 4,7,11,14-tetra(4-pyridyl)perylene diimide (3.26 mg, 3.64 μmol), tetrapyridine-p-terphenyl-methoxy (2.18 mg, 3.64 μmol), 4'-(4,7-bis(3-carboxyphenyl)-1H-benzo[d]imidazol-2-yl)-[1,1'-biphenyl]-3,5-dicarboxylic acid sodium salt (5 mg, 7.28 μmol) and cis-di(triethylphosphine)bis(trifluoromethanesulfonic acid)platinum(II) (21.25 mg, 29.13 μmol) in a molar ratio of 1:1:2:8, and dissolve them in a mixed solvent of acetonitrile / water (7.5 ml, 4:1, v / v) to obtain a mixed solution.

[0111] (2) After sonicating the mixed solution for 30 seconds, place it in a metal bath at a constant temperature of 55°C and stir for 12 hours. Then cool it to room temperature to obtain the product solution.

[0112] (3) The solvent was removed by drying with nitrogen gas flow. The residue was dissolved and filtered with acetonitrile (2.0 mL). Diethyl ether (8.0 mL) was added to precipitate the residue. After centrifugation, the residue was vacuum dried at 60 °C for 12 h to collect the four-component metal-organic cage based on perylene diimide and terphenyl. The metal-organic cage can be prepared through this example.

[0113] The product prepared in this embodiment 1 H NMR spectrum and 31 The p NMR spectra are as follows: Figure 9 and Figure 10 As shown.

[0114] (4) Take a 10 mL glass bottle, add the anisole substrate, standard, four-component metal cage (1% mol), deuterated acetonitrile and magnetic ball into the bottle, fill with oxygen, and calculate the conversion rate and yield of anisole under 520 nm light irradiation at different time periods.

[0115] like Figure 11 As shown, from left to right, these are 5a, 5b, and 5c. In the metal-organic cage crystal structure, each Pt atom is coordinated with one O atom and one N atom. The N atom is the N atom in the pyridine group of tetrapyridylperylene diimide or tetrapyridylterphenyl, and the O atom is an O atom on sodium tetradentate carboxylate. Tetrapyridylperylene diimide and tetrapyridylterphenyl are regarded as the top and bottom surfaces of the cage compound, respectively. The tetradentate carboxylate ligand is regarded as the side surface of the cage compound, and the Pt metal is regarded as the eight vertices of the cage compound.

[0116] Figure 12As shown, UV-Vis absorption spectra of the examples were measured to obtain the photophysical properties of the four-component metal cages 5a-5c in acetonitrile. All four-component metal cages 5a-5c exhibited three typical absorption bands with center wavelengths of 459 nm, 490 nm, and 526 nm, respectively, which are typical absorption bands of PDI pyridine ligands and showed no significant variation. Furthermore, compared to four-component metal cage 5a, the anthracene in four-component metal cage 5b, present on the p-terphenylpyridine ligand, exhibited two additional absorption bands at 373 nm and 395 nm, which stems from its characteristic π-π*-dominated electronic transitions.

[0117] like Figure 13 As shown, fluorescence emission spectra of the four-component metal cages 5a-5c were tested, revealing good fluorescence emission capabilities. All four-component metal-organic cages exhibited two fluorescence emission peaks with maximum emission wavelengths of 550 nm and 581 nm, respectively. This is because they share similar luminescent groups and conjugated structures, resulting in similar electronic transition energy levels and concentrated maximum emission wavelengths in similar regions. Furthermore, the fluorescence intensity of the four-component metal cages 5a-5c differed significantly, primarily due to differences in quantum yield. In acetonitrile, when excited at a wavelength of 520 nm, the fluorescence quantum yields of the four-component metal cages 5a-5c were measured to be 34.95%, 25.05%, and 30.16%, respectively. This indicates that the four-component metal cages 5b and 5c, after photoexcitation, absorb photons and undergo intramolecular transitions to generate charge-separated states, exhibiting better charge separation performance.

[0118] Figure 14 As shown, after testing the fluorescence emission spectra and quantum yields of the four-component metal cages 5a-5c, fluorescence lifetime experiments were conducted. The unmodified four-component metal cage 5a exhibited a relatively long fluorescence lifetime of 4.16 ns in acetonitrile, indicating that no additional groups were introduced to interfere with the excited state. Therefore, the fluorescence decay of the excited state mainly occurred through radiative transitions, with less competition from non-radiative transitions. The modified four-component metal cages 5b and 5c had fluorescence lifetimes of 3.76 ns and 3.75 ns, respectively. This indicates that the anthracene in the four-component metal cage 5b, as a highly conjugated system, participates in intramolecular charge transfer, forming a charge-separated state that causes the excited state energy to dissipate through non-radiative pathways, thus shortening the lifetime. In contrast, the methoxy group in the four-component metal cage 5c enhances the electron density of the parent nucleus, leading to intramolecular charge transfer after photoexcitation and also forming a separated state. Furthermore, the introduction of the methoxy group increases molecular flexibility and promotes vibrational energy dissipation, resulting in a shorter lifetime than that of the four-component metal cage 5b.

[0119] like Figure 15As shown, electron paramagnetic resonance (EPR) measurements were performed on the four-component metal cages 5a-5c to investigate the charge separation properties after photoexcitation. TEMPO (2,2,6,6-tetramethylpiperidine nitride) is a stable free radical that can be oxidized to TEMPO+ by photogenerated holes (h+), leading to a decrease in its EPR signal intensity. The greater the signal decrease, the higher the concentration of photogenerated holes in the system. The four-component metal cages 5b, 5c, and 5a caused the TEMPO signal peak decrease in the order of decreasing magnitude, indicating that the four-component metal cage 5b has a stronger hole generation ability or more efficient charge separation. Anthracene is an electron-donating group that forms a donor-acceptor structure with the parent nucleus, promoting the transfer from the donor to the acceptor after photoexcitation, forming a charge-separated state, reducing the probability of electron-hole recombination, stabilizing the holes, and allowing them to participate in the oxidation reaction to capture TEMPO, resulting in a significant decrease in signal intensity. The methoxy group is also an electron-donating group. After photoexcitation, due to the limited charge separation efficiency, the 5c signal of the four-component metal cage decreases less than that of 5b. The unmodified core undergoes rapid electron-hole recombination after photoexcitation, resulting in low hole utilization and the least decrease in EPR signal.

[0120] like Figure 16 As shown, electrochemical impedance spectroscopy was performed on the four-component metal cages 5a-5c to obtain the charge separation property after photoexcitation. The impedance radius corresponds to the charge transfer resistance R. ct The ease or difficulty of charge transfer on the surface of the reaction electrode, R ct The smaller the surface material, the higher the efficiency of charge separation and transport at the interface, R ct A larger value indicates impeded charge transfer, stemming from a high carrier recombination rate. The impedance radii of the four-component metal cages 5b, 5c, and 5a increase sequentially, indicating that the four-component metal cage 5b has a stronger charge separation efficiency. Anthracene, as an electron-donating group, forms a donor-acceptor structure with the parent nucleus, promoting the separation of photogenerated electron-hole pairs. Charge separation reduces carrier recombination, leading to more free holes and electrons participating in charge transfer, significantly reducing R0. ct The methoxy group, also an electron-donating group, results in a higher impedance radius (5c) of the four-component metal cage than that of 5b due to limited charge separation efficiency after photoexcitation. Meanwhile, the unmodified core exhibits rapid electron-hole recombination after photoexcitation, leading to low hole utilization and consequently, R... ct Relatively large.

[0121] like Figure 17As shown, photocurrent tests were performed on the four-component metal cages 5a-5c to obtain the charge separation properties after photoexcitation. The photocurrent intensity directly reflects the electron-hole pair separation efficiency and transport capability. A higher photocurrent indicates higher charge separation efficiency, lower carrier recombination rate, and faster charge migration to the electrode. Conversely, a lower photocurrent indicates limited charge separation or severe carrier recombination, leading to a reduction in the number of electron-hole pairs effectively participating in conduction. The photocurrents of the four-component metal cages 5b, 5c, and 5a decrease sequentially, indicating that the four-component metal cage 5b has a stronger charge separation efficiency. Anthracene, as an electron-donating group, forms a donor-acceptor structure with the parent nucleus, promoting the separation of photogenerated electron-hole pairs. Charge separation reduces carrier recombination, leading to more free holes and electrons participating in charge transfer, significantly increasing the photocurrent. Methoxy groups, also electron-donating groups, have limited charge separation efficiency after photoexcitation, resulting in a lower photocurrent for the four-component metal cage 5c compared to 5b. The unmodified parent nucleus exhibits rapid electron-hole recombination after photoexcitation, resulting in low hole utilization and a lower photocurrent.

[0122] like Figure 18 As shown, transient absorption spectroscopy was performed on the four metal cages 5a-5c to obtain the charge-separation property after photoexcitation. All four cages exhibited a ground-state bleaching peak at 530 nm, indicating that photoexcitation leads to a reduction in the ground-state molecules of the parent nucleus, corresponding to the formation of the excited S1 state. The presence of a ground-state bleaching peak in all metal cages at 0.2 ps indicates an extremely rapid excited-state formation rate; the stability within 0.2 ps to 0.92 ps indicates a long excited-state lifetime, without rapid decay through radiative or non-radiative transitions. All four cages exhibited a stimulated emission peak at 580 nm, originating from the radiative transition from the excited S1 state to the ground S0 state; the stability within 0.2 ps to 0.92 ps indicates that the excited-state molecules did not significantly deactivate through non-radiative pathways. All four cages showed an absorption peak of the PDI anion radical around 733 nm, originating from the electron donor donating electrons to the acceptor PDI after excitation, which is direct evidence of the generation of the charge-separated state. The increasing intensity of the PDI anion radical absorption peak from 0.2 ps to 0.92 ps indicates that the charge separation process continues and has not yet reached equilibrium. The peak intensities of the PDI anion radicals in the four-component metal cages 5b and 5c are significantly higher than those in the four-component metal cage 5a, indicating a higher rate or total amount of electron transfer to PDI, reflecting better charge separation efficiency.

[0123] like Figure 19As shown, the peak intensity increases from 0.2 ps to 0.92 ps, but then gradually decreases with time. Therefore, ten time periods were selected from 0.54 ps to 5335.22 ps for comparison. The continuous decrease in the ground-state bleaching peak at 530 nm indicates that the concentration of excited states of the parent nucleus decreases over time, originating from radiative and non-radiative transitions, including charge recombination. The continuous decrease in the stimulated emission peak at 580 nm indicates a decrease in the number of S1 state molecules. The decrease in the absorption peak intensity of the PDI anion radical around 730 nm directly reflects the charge separation process, where electrons return from the PDI anion radical to the parent nucleus and recombine with holes (h+), leading to a decrease in its concentration.

[0124] Figure 20 As shown, the decay trajectories of the PDI anion radical peak in the transient absorption spectrum were fitted with a fitting exponent n=2, yielding two time points, τ1 and τ2. In previous reports on the transient absorption spectra of PDI derivatives, τ1 and τ2 were attributed to molecular structure rearrangement and the S1 excited-state lifetime of the PDI anion radical, respectively, and are related to charge recombination. The τ2 values ​​of the four-component metal cages 5a-5c after photoexcitation, related to the charge separation efficiency or charge recombination of the PDI anion radical, were 1238 ps, 1852 ps, and 1804 ps, respectively, indicating that the lower the charge recombination rate of the four-component metal cage 5b, the higher the charge separation efficiency; while the unmodified four-component metal cage 5a had the highest charge recombination rate and the lowest charge separation efficiency. These results demonstrate that constructing an electron donor-donor structure to achieve efficient charge separation and a low recombination rate, significantly extending the S1 state lifetime of the PDI anion radical, is a key mechanism for optimizing photoelectric performance.

[0125] like Figure 21 As shown, DFT calculations were performed on the four-component metal cages 5a-5c to obtain the HOMO-LUMO energy levels, in order to study the charge separation properties after photoexcitation. The HOMO-LUMO band gap represents the minimum energy required for an electron in the molecule to transition from the HOMO to the LUMO. A smaller band gap indicates easier electron transitions, absorption of lower-energy photons, and generally stronger photoelectric response; a larger band gap requires higher-energy photons for electron transitions. The band gaps of the four-component metal cages 5b, 5c, and 5a increase sequentially, indicating that the narrower band gap of the four-component metal cage 5b is beneficial for light absorption and charge separation. This is consistent with previous results from electrochemical impedance spectroscopy, photocurrent measurements, EPR photogenerated hole experiments, and the lifetime of the S1 state of the PDI anion radical in transient absorption spectroscopy. The four-component metal cage 5a has the largest band gap, indicating that electron transitions require higher energy, limiting its photoelectric performance.

[0126] Figure 23As shown in the figure, in an embodiment of the present invention, with 1 mol% metal cages, the reaction was carried out at room temperature under 520 nm green light irradiation. The conversion rate of methyl phenyl sulfide was as high as 99% under the action of a four-component metal-organic cage based on perylene diimide and terphenyl, with yields of 99%, 89%, and 99.2%, respectively. With prolonged time, the conversion rate of anisole sulfide under the action of the three four-component metal cages continuously increased, eventually leading to almost complete conversion of the substrate. Furthermore, under the action of the unmodified four-component metal cage 5a, the conversion rate of anisole sulfide gradually exceeded that of the other four-component metal cages. Figure 24 As shown, starting from 80 min, the yield of anisole was highest under the action of the unmodified four-component metal cage 5a, while the yields of anisole decreased sequentially under the actions of 5c and 5b. To explain this phenomenon, the quantum yield of singlet oxygen was calculated. Figure 25 As shown, singlet oxygen can disrupt the conjugated structure of 9,10-diphenylanthracene (DPHA) and reduce the UV absorption peak, thus it can be used to calculate the singlet oxygen quantum yield. Using tetraphenylporphyrin (TPP) as a reference, the singlet oxygen quantum yields of the four metal cages 5a, 5b, and 5c were calculated to be 0.52, 0.42, and 0.48, respectively. This result corresponds to the yield, indicating that singlet oxygen is the predominant reactive oxygen species in this reaction. The four metal cage 5a exhibits the highest singlet oxygen quantum yield, and its fastest reaction rate corresponds to the leading yield of anisole at 80 min. The four metal cages 5b and 5c may inhibit singlet oxygen generation; charge separation preferentially uses excited-state energy for electron transfer to generate superoxide anion radicals or hydroxyl radicals, rather than for energy transfer to generate singlet oxygen, hence their lower reaction rates and yields.

[0127] This invention discloses a method for preparing a four-component metal-organic cage based on perylene diimide and terphenyl. The organic cage is prepared from a tetrapyridylperylene diimide ligand, a tetrapyridyl-p-terphenyl ligand, a tetradentate sodium carboxylate ligand, and a cisplatin metal ligand. During the preparation process, the sodium ion in the tetradentate sodium carboxylate ligand dissociates in solution. The cisplatin metal ligand Pt(PEt3)2(OTf)2 loses two trifluoromethanesulfonate anions in solution and then self-assembles with the N atom in the pyridine group of the tetrapyridylperylene diimide and the tetrapyridyl-p-terphenyl ligand, and the O atom on the tetradentate carboxylate via metal-organic coordination, respectively, to form the target four-component organometallic cage. The detached trifluoromethanesulfonate ions serve as counterions around the Pt metal sites of the metal cage. This method can achieve a yield of up to 90% for preparing the four-component metal-organic cage based on perylene diimide and terphenyl. A four-component metal-organic cage based on perylene diimide and terphenyl, comprising tetrapyridylperylene diimide ligands, tetrapyridylterphenyl ligands, and tetradentate sodium carboxylate and cisplatin, yields a luminescent metal-organic cage. Upon photoexcitation, the electron donor of the four-component organometallic cage undergoes effective charge separation, resulting in charge transfer and the formation of perylene diimide anion radicals. Furthermore, the absolute fluorescence quantum yields of the luminescent metal-organic cages 5a-5c, assembled from tetrapyridylperylene diimide ligands, tetrapyridylterphenyl ligands, and tetradentate sodium carboxylate and cisplatin in acetonitrile are 34.95%, 25.05%, and 30.16%, respectively. The prepared four-component organometallic cages possess well-defined cavities and, under illumination, can convert oxygen to singlet oxygen via energy transfer, selectively oxidizing methyl phenyl sulfide to methyl phenyl sulfoxide, thus artificially preparing a photocatalytic oxidation system.

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the preparation of a four-component metallo-organic cage based on perylene diimide and terphenyl, characterized in that, The method comprises the following steps: dissolving a tetrapyridyl perylene diimide ligand, a tetrapyridyl terphenyl ligand, a tetradentate sodium carboxylate ligand and a cisplatin metal ligand in a mixed solvent, ultrasonic treating and stirring the mixed system, and obtaining a reaction product through a self-assembly reaction, and obtaining a perylene diimide and terphenyl-based metal-organic cage with a cavity through purification treatment. The tetrapyridyl perylene diimide ligand is 4,7,11,14-tetra(4-pyridyl)perylene diimide, and a structural formula is as follows: II The tetrapyridyl terphenyl ligand is any one of tetrapyridyl p-terphenyl-benzene, tetrapyridyl p-terphenyl-anthracene and tetrapyridyl p-terphenyl-methoxy, and structural formulas are as follows: III IV V The tetradentate sodium carboxylate ligand is 4'- (4,7-bis (3-carboxyphenyl) -1H-benzo [d] imidazole-2-yl) -[1,1'-biphenyl]-3,5-dicarboxylic acid sodium, and a structural formula is as follows: VI.

2. The method for the preparation of a four-component metallo-organic cage based on perylenediimides and terphenyls according to claim 1, characterized in that, The cisplatin metal ligand is cis-bis (triethylphosphine) bis (trifluoromethyl sulfonic acid) platinum (II).

3. The method for the preparation of perylene diimide and terphenyl based four- component metallo-organic cages according to claim 1, characterized in that, The preparation process of the 4'- (4,7-bis (3-carboxyphenyl) -1H-benzo [d] imidazole-2-yl) -[1,1'-biphenyl]-3,5-dicarboxylic acid sodium comprises the following steps: (1) generating compound 1 by reacting 4,7-dibromo-2,3-benzothiadiazole, 3-ethoxycarbonylphenyl boronic acid, tetrakis (triphenylphosphine) palladium and Cs2CO3; (2) dissolving compound 1 in a mixed solution of THF and EtOH, adding NaBH4 and CoCl2·6H2O after reaction, extracting with brine and DCM, mixing the extract with 4-bromobenzaldehyde and ZrCl4, and recrystallizing to obtain compound 2; (3) generating compound 3 by mixing compound 2, 3,5-dimethoxycarbonylphenyl boronic acid, tetrakis (triphenylphosphine) palladium and Cs2CO3 and then reacting; (4) mixing compound 3, potassium hydroxide, THF and water, refluxing, and adding HCl dropwise in the refluxing solution to obtain compound 4; (5) dissolving compound 4 and sodium hydroxide in water, precipitating solid through acetone to obtain 4'- (4,7-bis (3-carboxyphenyl) -1H-benzo [d] imidazole-2-yl) -[1,1'-biphenyl]-3,5-dicarboxylic acid sodium.

4. The method for the preparation of a four-component metallo-organic cage based on perylenediimides and terphenyls according to claim 3, characterized in that, The mixing molar ratio of the tetrapyridyl perylene diimide ligand, the tetrapyridyl terphenyl ligand, the tetradentate sodium carboxylate ligand and the cisplatin metal ligand is 1:1:2:

8.

5. The method for the preparation of perylene diimide and terphenyl based four- component metallo-organic cages according to claim 3, characterized in that, The stirring process is that the stirring temperature is 55 DEG C and the stirring time is 12 h.

6. A perylene diimide and terphenyl-based four-component metal-organic cage prepared by the preparation method in any one of claims 1-5.

7. Use of the perylenediimide and terphenyl based four-component metallo-organic cage according to claim 6, characterized in that, The metal-organic cage is used for photocatalytic oxidation reaction as a photocatalyst. The photocatalytic oxidation can generate singlet oxygen, and the singlet oxygen is used for oxidizing methyl phenyl sulfide.

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