Use of a spin catalyst based on a macrocyclic gadolinium complex in photoredox reactions

Abstract

The application belongs to the field of organic photochemical synthesis and catalysis technology, and discloses application of a spin catalyst based on a macrocyclic gadolinium complex in a photo-oxidation-reduction reaction. The spin catalyst utilizes the high-spin ground state of gadolinium ions, promotes intersystem crossing of a singlet radical ion pair to a triplet radical ion pair in a photo-reaction intermediate through paramagnetic effect, and effectively inhibits the reverse electron transfer process. In particular, the Gd-DOTP complex in an aqueous system induces the formation of an ordered hydrogen bond network of solvent water molecules through phosphonic acid groups on the ligand, constructs a proton-mediated spin transport channel, and can achieve efficient catalysis at a low concentration (0.5-3.0 mM) of millimolar level. The system significantly inhibits BET and improves the efficiency of organic photo-oxidation-reduction reactions, is suitable for halogenated aromatic hydrocarbon dehalogenation, benzylic oxidation hydroxylation and the like, and has the advantages of small catalyst dosage, good stability and wide application range.

Description

Technical Field

[0001] This invention belongs to the field of organic photochemical synthesis and catalysis technology, and specifically relates to the application of a spin catalyst based on macrocyclic gadolinium complex in promoting the efficiency of photoredox reactions. Background Technology

[0002] Organic photoredox catalysis utilizes visible light to excite photosensitizers and activate organic molecules via single-electron transfer (SET), making it an important tool in modern green synthesis. However, widely used organic dye photosensitizers (such as phenothiazine and eosin Y) typically exhibit weak spin-orbit coupling (SOC) effects. This results in the radical ion pairs (RIPs) generated after photoinduced electron transfer primarily being in the singlet state. Due to the Pauli exclusion principle, singlet RIPs readily undergo back electron transfer (BET) back to the ground state, leading to wasted light energy and reduced reaction quantum efficiency.

[0003] Currently, the main method to improve the quantum efficiency of organic photo-oxidation-reduction reactions is through complex modification of photosensitizer molecules, which involves a complicated and cumbersome synthesis process.

[0004] To address this issue, a spin catalysis strategy has been employed, introducing paramagnetic substances to interact with reactive oxygen species (RIPs). This accelerates the intersystem crossing (ISC) of RIPs, transforming them into a spin-forbidden BET triplet state, thereby extending the intermediate lifetime and promoting the forward reaction, ultimately increasing product yield. However, this strategy is currently limited to mechanistic research and lacks practical applications in enhancing organic photo-oxidation-reduction reactions. Furthermore, traditional spin catalysts suffer from the following drawbacks: limited efficiency: traditional spin catalysis relies primarily on physical collisions between reactants (diffusion control), requiring high catalyst concentrations to produce significant effects; poor stability: simple paramagnetic metal salts or organic radicals used as spin catalysts are prone to side reactions or degradation under complex photoreaction conditions; and a single mechanism: there is a lack of long-range spin modulation methods capable of overcoming diffusion limitations.

[0005] Therefore, developing a highly stable, low-dosage, diffusion-limiting, and efficient spin catalyst that can enhance organic photo-redox reactions is of great significance for promoting the practical application of photo-redox catalysis. Summary of the Invention

[0006] To overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide an application of spin catalysts based on macrocyclic gadolinium complexes in photo-redox reactions, particularly in the dehalogenation and hydrogenation photo-redox reactions of halogenated aromatics and in the photo-oxidative hydroxylation of aromatic compounds. Although macrocyclic gadolinium complexes are widely used in magnetic resonance imaging, their application as spin catalysts in organic photo-redox reactions has not been reported. This invention creatively discovers that such complexes exhibit unique advantages in these reactions. First, due to the good chemical stability of macrocyclic gadolinium complexes, they cause minimal interference to the reaction system, thus enabling the non-destructive acceleration of organic photo-redox reactions and possessing broad applicability. Second, compared to the traditional method of inhibiting the reverse electron transfer in organic photo-redox reactions and improving reaction efficiency through complex modification of the photocatalyst, spin catalysts only require simple addition, making the method simpler, faster, and requiring no complex operational steps.

[0007] The objective of this invention is achieved through the following solution:

[0008] The application of macrocyclic gadolinium complexes as spin catalysts in organic photo-redox reactions, especially in the photo-redox reaction of dehalogenation and hydrogenation of halogenated aromatics and the photo-oxidative hydroxylation of aromatic compounds.

[0009] The macrocyclic gadolinium complex has the structure of either Formula I or Formula II, wherein Formula I represents Gd-DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid gadolinium), and Formula II represents Gd-DOTP (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylenephosphonate gadolinium).

[0010]

[0011] Preferably, the macrocyclic gadolinium complex has the structure Gd-DOTP (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylenephosphonate gadolinium).

[0012] While Gd-DOTA and Gd-DOTP are widely known as contrast agents in magnetic resonance imaging (MRI), their mechanism of action in MRI is based on the acceleration of spin relaxation of surrounding water proton nuclei by paramagnetic centers. However, this invention reveals for the first time a novel function of this type of macrocyclic complex in the field of photocatalysis—as a spin catalyst. Unlike the MRI mechanism, this invention utilizes its large magnetic moment (S=7 / 2) to suppress reverse electron transfer (BET) by directly interfering with the electronic spin state evolution of photoinduced free radical ion pairs (RIPs). This catalytic mechanism based on "electron-electron" spin interactions is fundamentally different from imaging mechanisms based on "electron-nucleus" spin interactions.

[0013] The application of macrocyclic gadolinium complexes as spin catalysts in organic photo-redox reactions specifically includes the following steps:

[0014] A macrocyclic gadolinium complex was added as a spin catalyst to an organic photo-redox catalytic reaction system, and then a photocatalytic redox reaction was carried out under light irradiation.

[0015] The aforementioned organic photo-oxidation-reduction catalytic reaction system includes an organic photosensitizer, a reaction substrate, and a solvent. Depending on the reaction substrate, the photo-oxidation-reduction reaction system can be a photo-oxidation-reduction reaction system for the dehalogenation and hydrogenation of haloaromatic hydrocarbons or a photo-oxidative hydroxylation reaction system for aromatic compounds.

[0016] When the photo-oxidation-reduction reaction system is a photo-oxidation-reduction reaction system for the dehalogenation and hydrogenation of haloaromatic hydrocarbons:

[0017] The solvent is a mixture of an organic solvent and water, wherein the organic solvent is selected from at least one of polar aprotic solvents, such as dimethyl sulfoxide, N,N-dimethylformamide, acetonitrile, acetone, etc., preferably dimethyl sulfoxide; the volume ratio of the organic solvent to water can be adjusted within a wide range, for example from 1:1 to 30:1, preferably 9:1;

[0018] The organic photosensitizer is an organic compound with photoredox activity, especially a phenothiazine derivative, including but not limited to at least one of 10-phenyl-10H-phenothiazine, phenothiazine, 10-methyl-10H-phenothiazine and other phenothiazine derivatives;

[0019] The dehalogenation and hydrogenation photo-oxidation-reduction reaction system of the haloaromatic hydrocarbons may also include a reduction sacrificial agent, wherein the reduction sacrificial agent is an organic amine compound, such as at least one of the tertiary amines such as triethylamine, N,N-diisopropylethylamine, and diethylamine, preferably N,N-diisopropylethylamine (DIPEA).

[0020] The halogenated aromatic hydrocarbon is an aryl halide, such as at least one of methyl 4-chlorobenzoate, 4-chlorobenzonitrile, methyl 3-chlorobenzoate, methyl 2-chlorobenzoate, methyl 4-chloro-3-methylbenzoate, methyl 4-bromobenzoate, methyl 4-iodobenzoate, ethyl 4-chlorobenzoate, pentafluoropyridine, and other aryl halides with similar structures.

[0021] In the aforementioned dehalogenation and hydrogenation photo-oxidation-reduction reaction system of haloaromatics, the concentration of the substrate haloaromatics is 0.005-1 M; 0.001-0.2 mol of photosensitizer is added for every 1 mol of substrate haloaromatics; and 0.5-4 mol of reducing sacrificial agent is added for every 1 mol of substrate haloaromatics.

[0022] The amount of the macrocyclic gadolinium complex used is such that, after being added to the dehalogenation and hydrogenation photoredox reaction system of the haloaromatic hydrocarbon, the concentration of the macrocyclic gadolinium complex is 0.1-50 mM, preferably 0.5-3 mM. The amount of the macrocyclic gadolinium complex used is such that 0.005-0.1 M of macrocyclic gadolinium complex is added for every 1 mol of substrate haloaromatic hydrocarbon, preferably 0.005-0.03 M of macrocyclic gadolinium complex is added for every 1 mol of substrate haloaromatic hydrocarbon.

[0023] The photocatalytic oxidation-reduction reaction under illumination refers to the reaction at 25-50°C for 5 minutes to 10 hours under 365-550 nm light irradiation in air or an inert atmosphere, preferably under 365-550 nm LED light irradiation at 25-50°C for 5 minutes to 10 hours.

[0024] When the photo-redox reaction system is a photo-oxidative hydroxylation reaction system of aromatic compounds:

[0025] The solvent is a mixture of an organic solvent and water, wherein the organic solvent is acetonitrile; the volume ratio of the organic solvent to water can be adjusted within a wide range, for example, between 1:1 and 4:1, preferably 4:1;

[0026] The organic photosensitizer is an organic compound with photo-redox activity, especially quinoline salt photosensitizers and their derivatives, such as 3-cyano-1-methylquinoline salt, other substituted quinoline salts or structurally similar heterocyclic cationic salts, preferably 3-cyano-1-methylquinoline salt;

[0027] The substrate is an aromatic compound, including but not limited to at least one of benzene, substituted aromatic hydrocarbons, and heterocyclic aromatic hydrocarbons, preferably benzene.

[0028] In the photooxidative hydroxylation reaction system of the aromatic compound, the concentration of the substrate aromatic compound is 0.01-1 M; for every 1 mol of substrate aromatic compound, 0.01-0.2 mol of photosensitizer is added.

[0029] The amount of the macrocyclic gadolinium complex is such that after the macrocyclic gadolinium complex is added to the photooxidative hydroxylation reaction system of benzene, the concentration of the macrocyclic gadolinium complex is 0.1-50 mM.

[0030] The photocatalytic oxidation-reduction reaction under illumination refers to the reaction at 25-50°C for 5 minutes to 10 hours under an air or O2 atmosphere and irradiated with 365-450 nm light, preferably under LED light irradiation at 365-450 nm.

[0031] The mechanism of this invention is as follows:

[0032] Macrocyclic gadolinium complexes as spin catalysts: Highly chemically stable macrocyclic ligands (DOTA and DOTP) are selected to complex gadolinium ions. Gd(III) possesses seven unpaired electrons (4f...). 7 It has a large magnetic moment, and the macroring structure avoids the dissociation of metal ions and non-specific reactions.

[0033] Suppression of reverse electron transfer (BET): In the photoreaction, macrocyclic gadolinium complexes act as spin catalysts, significantly accelerating the conversion of singlet RIPs to triplet RIPs through magnetic dipole-dipole interactions or exchange interactions. Triplet RIPs cannot directly undergo BET back to the singlet ground state, thus forcing the reaction to proceed in the forward direction.

[0034] Proton-mediated ultrafast transport (for Gd-DOTP): This invention reveals that the four phosphonic acid groups surrounding Gd-DOTP not only provide a strong negative charge field but also act as hydrogen bond donors / acceptors, inducing the formation of an ordered hydrogen bond network by solvent water molecules. This network, like a "spin transport highway," allows for ultrafast, long-range transport of spin angular momentum via a proton transfer mechanism. This enables Gd-DOTP to exhibit catalytic activity an order of magnitude higher than conventional catalysts even at extremely low concentrations (1.4 mM). This characteristic is not possessed by traditional simple gadolinium salts or common carboxylic acid complexes (such as Gd-DOTA) and is the key structural basis for its highly efficient catalysis at millimolar low concentrations.

[0035] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0036] The present invention uses macrocyclic gadolinium complexes as spin catalysts to significantly improve the reaction efficiency of haloaromatic dehalogenation model reactions, increasing the reaction rate by more than 25 times and the yield by nearly 100%, thus solving the problem of low efficiency in haloaromatic dehalogenation reactions.

[0037] This invention utilizes macrocyclic gadolinium complexes as spin catalysts to overcome diffusion limitations in photoredox reactions. Existing technologies generally consider that the spin-flipping effect of paramagnetic materials on free radical pairs depends on frequent physical collisions, thus typically requiring extremely high loading levels (often greater than 10 mM, or even higher). This invention discovers that a specific phosphonate-based macrocyclic gadolinium complex (Gd-DOTP) exhibits superior catalytic activity at extremely low concentrations (1.4 mM), with catalytic efficiency more than 10 times higher than Gd-DOTA at the same concentration, and significantly superior to non-macrocyclic, free Gd. 3+This result demonstrates that the catalytic activity is not solely due to the intrinsic properties of Gd, but rather a non-obvious technical effect resulting from the synergistic interaction of the macrocyclic ligand structure, solvent environment, and metal center. It also proves that extremely low doses of Gd-DOTP utilize the hydrogen bond network formed between phosphonic acid groups and the solvent, no longer relying solely on molecular collisions, thus overcoming the bottleneck of high concentration loading required for traditional spin catalysts.

[0038] The application of the macrocyclic gadolinium complex as a spin catalyst of the present invention is highly versatile. The system is applicable to a variety of photosensitizers (phenothiazines, quinolines) and a wide range of substrates (including but not limited to chloro / bromine / iodophors and aromatic substrates with different substituents), and has no special requirements for the reaction apparatus (a conventional LED light source is sufficient). Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the reverse electron transfer (BET) process and spin catalysis mechanism in photo-redox reactions.

[0040] Figure 2 The graph shows the effect of different concentrations of Gd-DOTP on the yield and conversion rate of the photoreduction dehalogenation reaction in Example 4.

[0041] Figure 3 This is a graph showing the effect of Gd-DOTP on the yield of photoreduction dehalogenation reaction under different water contents in Example 6.

[0042] Figure 4 This is a schematic diagram of the "proton-mediated spin catalysis" model of Gd-DOTP (phosphonic acid groups and water molecules form a hydrogen bond network).

[0043] Figure 5 Mass spectra of Gd-DOTA and Gd-DOTP.

[0044] Figure 6 The gas chromatographic qualitative results of the dechlorination and hydrogenation photo-oxidation-reduction reaction system with methyl 4-chlorobenzoate as the substrate (monitoring the changes in the chromatographic peaks of the product and substrate before and after the addition of the spin catalyst). Detailed Implementation

[0045] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0046] Example 1

[0047] The synthetic method based on the macrocyclic gadolinium complex Gd-DOTA includes the following steps:

[0048] Dissolve 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA, 50 mg, 124 μmol) in 5 mL of deionized water, and denote this solution as solution A.

[0049] Dissolve GdCl3·6H2O (50.5 mg, 136 μmol) in 0.5 mL of deionized water, and denote this solution as solution B.

[0050] Add B slowly dropwise to A while stirring, keeping the solution clear.

[0051] The mixture was heated and stirred at 60°C for 24 hours. The reaction solution was filtered through a 0.22 μm filter membrane and freeze-dried to obtain the crude product.

[0052] The crude product was dissolved in methanol, then precipitated with excess diethyl ether. After centrifugation, the supernatant was collected and precipitated again with diethyl ether. Finally, all the precipitates were collected and dried to obtain 63 mg of white Gd-DOTA powder solid, with a yield of 90%. ESI-MS (m / z): Calculated value: [C 16 H 24 N4O8Gd] - : 558.1; Experimental value: 558.05. Mass spectrum as follows Figure 5 As shown.

[0053] Example 2

[0054] The synthetic method based on the macrocyclic gadolinium complex Gd-DOTP includes the following steps:

[0055] Dissolve 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra(methylenephosphonic acid) (DOTP, 100 mg, 0.18 mmol) in 5 mL of deionized water, and denote this solution as solution C.

[0056] Adjust the pH using 1 M NaOH solution until the solution becomes clear.

[0057] Dissolve GdCl3·6H2O (67 mg, 0.18 mmol) in 0.5 mL of deionized water and denote the solution as solution D.

[0058] Under stirring conditions, slowly add D dropwise to C, and continue to adjust the pH to 6-7.

[0059] The reaction was heated and stirred at 60°C for 48 hours; the reaction solution was then freeze-dried to obtain the crude product.

[0060] The crude product was placed in a funnel, and the precipitate was washed dropwise with 0.5 mL of methanol and water, respectively. This operation was repeated at least three times. Finally, the remaining precipitate was dried to obtain 166 mg of white Gd-DOTP powder solid, with a yield of 91%. ESI-MS (m / z): Calculated value: [C 12 H 28 N4O 12 [P4Gd]: 701.4; Experimental value: 702.2. Mass spectrum as follows: Figure 5 As shown.

[0061] Example 3

[0062] Based on Gd-DOTA as a spin catalyst for photoreduction dehalogenation and hydrogenation reaction.

[0063] The reaction system consisted of 9 mL of dimethyl sulfoxide (DMSO) solvent and 1 mL of water [DMSO:H2O = 9:1 (volume ratio)], containing 0.1 M methyl 4-chlorobenzoate (substrate), 5 mM Ph-PTZ (photosensitizer, 10-phenyl-10H-phenthiazine), and 0.2 M DIPEA (sacrificial agent, N,N-diisopropylethylamine).

[0064] Procedure: To ensure complete dissolution of the spin catalyst in the reaction system, 0.0558 g of Gd-DOTA was first dissolved in 1 mL of water in the above reaction system, and then added to the remaining system (i.e., the reaction system lacking 1 mL of water) to achieve a concentration of 10 mM in the total solution. The reaction was conducted under air atmosphere and room temperature conditions using a 365 nm LED (4 W / cm²). 2 Irradiation. Qualitative results of gas chromatography (monitoring the changes in chromatographic peaks of the product and substrate before and after the addition of the spin catalyst), such as... Figure 6 As shown. Simultaneously, a Gd-free group is set up that does not add 0.0558 g of Gd-DOTA.

[0065] Results: After 5 minutes of reaction, the yield of the group with added Gd-DOTA was significantly higher than that of the group without Gd. After 2 hours of reaction, the yield of the group without Gd was 33% and the conversion rate was 61%; the yield of the group with Gd-DOTA increased to 51% and the conversion rate increased to about 80%.

[0066] Conclusion: Gd-DOTA effectively improves reaction efficiency through a solution diffusion control mechanism.

[0067] Example 4

[0068] Gd-DOTP concentration optimization experiment.

[0069] Same as Example 3, but with the catalyst changed to Gd-DOTP, and its effect on the reaction yield after 2 hours was investigated.

[0070] 0 mM: Yield 33%; Conversion rate: 61%.

[0071] 0.5 mM: Yield 45%; Conversion rate: 65%.

[0072] 1.4 mM: Yield 63%; Conversion rate: 87%.

[0073] 3.0 mM: Yield 67%; Conversion rate: 90%.

[0074] Conclusion: Spin catalysts exhibit significant effects across the 0.5–3.0 mM range (all concentrations refer to the catalyst concentration in the entire reaction system), with an optimal window. Higher concentrations may lead to aggregation or light-shielding effects, slightly reducing efficiency, thus confirming the superiority of Gd-DOTP at low concentrations.

[0075] Example 5

[0076] High-efficiency catalysis and mechanism confirmation of Gd-DOTP at low concentrations.

[0077] Reaction system: Same as in Example 3, but the spin catalyst was changed to Gd-DOTP, and its concentration in the entire reaction system was set to only 1.4 mM.

[0078] Results: At a low concentration of 1.4 mM, the Gd-DOTP group achieved a yield of 63% and a conversion of 87% after 2 hours, demonstrating a significant spin catalytic effect (compared to 33% in the Gd-free group). In contrast, the addition of 1.4 mM Gd-DOTA did not show significant spin catalytic effect (yield 34%).

[0079] The molar spin catalytic effect (Molar SCE) is defined as the rate of increase in yield after concentration normalization (SCE = [yield with Gd - yield without Gd] / yield without Gd × 100%, Molar SCE = SCE / spin catalyst concentration, with the concentration unit being mol / L, equivalent to M). The Molar SCE value for Gd-DOTP is 650 M. -1 It is Gd-DOTA (55M) -1 More than 10 times that of ).

[0080] Conclusion: Such a significant catalytic enhancement effect in a homogeneous solution system at millimolecular low concentrations is unprecedented, strongly suggesting that the system possesses an unconventional mechanism that breaks through the physical limitations of diffusion-controlled spin interactions.

[0081] Example 6

[0082] Water content dependence and mechanism verification of Gd-DOTP spin catalysis effect.

[0083] Similar to Example 5, the water content in the mixed solvent of the reaction system was changed, while the total volume of the mixed solvent was kept at 10 mL. The reaction yield and spin catalytic effect were evaluated after 1 hour (SCE = [Gd-added yield - Gd-free yield] / Gd-free yield × 100%).

[0084] Results: When DMSO:H2O = 19:1 (volume ratio), the SCE of Gd-DOTP was only 6.3%; when the water content was increased to DMSO:H2O = 9:1 to 4:1, the SCE jumped sharply to 60%-85%.

[0085] The specific experimental comparison results are shown in Table 1 below:

[0086] Table 1. Effect of water content in mixed solvent on autocatalytic performance

[0087]

[0088] Conclusion: The Gd-DOTP-mediated spin catalysis effect exhibits a highly nonlinear response to water content, supporting the rapid onset of high spin catalytic activity originating from the formation of hydrogen bond networks, in contrast to the linear results of the traditional diffusion mechanism.

[0089] Example 7

[0090] Gd-DOTP spin-catalyzed isotope effect (KIE).

[0091] Similar to Example 5, the H2O in the solvent was replaced with an equal volume of D2O, and the KIE (K2O) was evaluated. ).

[0092] Results: The catalytic efficiency of the Gd-DOTP system decreased significantly, with a measured KIE ≈ 1.7; while under the same conditions, the KIE of the Gd-DOTA system was ≈ 1.0. This confirms that the high activity of Gd-DOTP originates from a proton (H⁺)-mediated non-diffusion mechanism, which is supported by the weak hydrogen bond network and slow proton transport in D₂O.

[0093] Example 8

[0094] Spin catalysis performance evaluation and comparative analysis.

[0095] Similar to Example 3, the reaction temperature and the type of spin catalyst were changed, and the yield and conversion rate were evaluated after 2 hours of reaction.

[0096] Results: The specific experimental comparison results are shown in Table 2 below:

[0097] Table 2. Effects of reaction temperature and spin catalyst type on autocatalytic performance

[0098]

[0099] The synthesis of Y-DOTA in Table 2 includes the following steps:

[0100] Dissolve 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA, 50 mg, 124 μmol) in 5 mL of deionized water, and denote this solution as solution A.

[0101] Dissolve YCl3·6H2O (38.0 mg, 125 μmol) in 0.5 mL of deionized water, and denote this solution as solution B.

[0102] Add B slowly dropwise to A while stirring, keeping the solution clear.

[0103] The mixture was heated and stirred at 60°C for 24 hours. The reaction solution was filtered through a 0.22 μm filter membrane and freeze-dried to obtain the crude product.

[0104] The crude product was dissolved in methanol, then precipitated with excess diethyl ether. After centrifugation, the supernatant was collected and precipitated again with diethyl ether. Finally, all precipitates were collected and dried to obtain 43 mg of γ-DOTA white powder solid, yield 71%. ESI-MS (m / z): [C 16 H 25 N4O8Y] + Calculated value: 491.1; Experimental value: 491.1.

[0105] The synthesis of Y-DOTP in Table 2 includes the following steps:

[0106] Dissolve 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra(methylenephosphonic acid (DOTP, 50 mg, 0.09 mmol)) in 5 mL of deionized water, and denote this solution as solution C.

[0107] Adjust the pH using 1 M NaOH solution until the solution becomes clear.

[0108] Dissolve YCl3·6H2O (27 mg, 0.09 mmol) in 0.5 mL of deionized water and denote it as solution D.

[0109] Under stirring conditions, slowly add D dropwise to C, and continue to adjust the pH to 6-7.

[0110] The reaction was heated and stirred at 60°C for 48 hours; the reaction solution was filtered through a microporous membrane, and the filtrate was freeze-dried to obtain the crude product.

[0111] The crude product was dissolved in methanol, then precipitated with excess diethyl ether. After centrifugation, the supernatant was collected and precipitated again with diethyl ether. Finally, all precipitates were collected and dried to obtain 42 mg of γ-DOTP white powder solid, yield 74%. ESI-MS (m / z): Theoretical value: [C 12 H24 N4O 12 P4Y]: 628.9; Experimental value: 629.1.

[0112] Conclusion: Diamagnetic control: Y 3+ To prevent diamagnetism, its structure is highly similar to that of the corresponding paramagnetic complex. The lack of yield improvement demonstrates that the electron spin effect is crucial.

[0113] Free ion comparison: The non-macrocyclic GdCl3 complex performed significantly worse than the macrocyclic complex. This indicates that macrocyclic ligands not only play a stabilizing role, but their specific geometry is also crucial for catalysis.

[0114] Temperature effect: At 50℃, the proton transfer process mediated by the Gd-DOTP hydrogen bond network is accelerated, thereby significantly improving the reaction efficiency and promoting the reaction to approach 100% conversion.

[0115] Example 9

[0116] Substrate extensibility studies.

[0117] Based on Example 5, the photoreduction dehalogenation effect of different substrates in long-term reactions (reaction time 5-10 hours) was tested by changing only the type of substrate:

[0118] 4-Chlorobenzonitrile (reaction time 10 hours): conversion 55%, yield 42% (Gd-free group: conversion 46%, yield 30%).

[0119] Methyl 3-chlorobenzoate (reaction time 5 hours): conversion 72%, yield 55% (Gd-free group: conversion 42%, yield 30%).

[0120] Methyl 2-chlorobenzoate (reaction time 5 hours): conversion rate 74%, yield 67% (Gd-free group: conversion rate 54%, yield 48%).

[0121] Methyl 4-chloro-3-methylbenzoate (reaction time 10 hours): conversion 82%, yield 76% (Gd-free group: conversion 58%, yield 42%).

[0122] Methyl 4-bromobenzoate (reaction time 5 hours): conversion 73%, yield 62% (Gd-free group: conversion 65%, yield 42%).

[0123] Methyl 4-iodobenzoate (reaction time 5 hours): conversion rate 80%, yield 66% (Gd-free group: conversion rate 74%, yield 62%).

[0124] Ethyl 4-chlorobenzoate (reaction time 10 hours): conversion 99%, yield 54% (Gd-free group: conversion 94%, yield 42%).

[0125] Pentafluoropyridine (reaction time 10 hours): conversion 63%, yield 44% (Gd-free group: conversion 45%, yield 30%).

[0126] Conclusion: The spin catalyst of the present invention has a universal catalytic enhancement effect on substrates with different electronic effects, different substitution positions, and different types of halogens.

[0127] Example 10

[0128] Applications of Gd-DOTA and Gd-DOTP as spin catalysts in other photo-redox reactions.

[0129] The photo-oxidative hydroxylation of benzene follows the following reaction process:

[0130]

[0131] Reaction conditions: The solvent was a mixed solvent of 10 mL MeCN:H2O (volume ratio 4:1), benzene (0.2 M), and 3-cyano-1-methylquinoline salt (QuCN). + , 5 mM), 365 nm LED (4 W / cm 2 Irradiate for 2 hours in an O2 atmosphere.

[0132] Results: Spinless catalyst group: yield 31%; after adding 10 mM Gd-DOTA, yield 40%; after adding 1.4 mM Gd-DOTP, yield 43%.

[0133] Conclusion: The efficiency of benzene to phenol is significantly improved, proving that this type of catalyst is also applicable to RIPs systems generated by the oxidative quenching pathway.

[0134] In the photo-redox reaction of this invention, the concentration of the substrate (halogenated aromatic hydrocarbons and benzene) is typically between 0.05 M and 0.5 M, and the concentration of the photocatalyst (10-methyl-10H-phenthiazine and 3-cyano-1-methylquinoline salt) is typically between 0.1% and 20% of the substrate molar concentration. Notably, this invention has found that Gd-DOTP exhibits remarkably low-concentration spin catalytic activity. For example, under typical conditions of a substrate concentration of 0.1 M, only 1.4 mM of Gd-DOTP (i.e., only 1.4% of the substrate molar amount) is required to achieve optimal catalytic performance. Therefore, those skilled in the art will understand that the preferred concentration range of 0.5-3.0 mM is based on typical photoreaction conditions (substrate approximately 0.1 M); in practical applications, the amount of spin catalyst can be adjusted accordingly from 0.1 mM to 50 mM based on changes in substrate concentration, all of which fall within the scope of this invention.

[0135] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. The application of macrocyclic gadolinium complexes as spin catalysts in the photo-oxidation-reduction reaction of dehalogenation and hydrogenation of haloaromatics, characterized in that... The structure of the macrocyclic gadolinium complex is shown in Formula II: ； Specifically, the steps include: adding a macrocyclic gadolinium complex as a spin catalyst to the dehalogenation hydrogenation photo-oxidation-reduction reaction system of haloaromatic hydrocarbons, and then conducting a photocatalytic oxidation-reduction reaction under light irradiation; The dehalogenation hydrogenation photo-oxidation-reduction reaction system of the haloaromatic hydrocarbons includes an organic photosensitizer, a substrate, and a solvent; the solvent is a mixture of an organic solvent and water, wherein the organic solvent is selected from dimethyl sulfoxide; the volume ratio of the organic solvent to water is 4:1 to 9:1; the organic photosensitizer is 10-phenyl-10H-phenthiazine; the haloaromatic hydrocarbon is at least one selected from methyl 4-chlorobenzoate, 4-chlorobenzonitrile, methyl 3-chlorobenzoate, methyl 2-chlorobenzoate, methyl 4-chloro-3-methylbenzoate, methyl 4-bromobenzoate, ethyl 4-chlorobenzoate, and pentafluoropyridine; a reduction sacrificial agent is also added to the dehalogenation hydrogenation photo-oxidation-reduction reaction system of the haloaromatic hydrocarbons, wherein the reduction sacrificial agent is N,N-diisopropylethylamine.

2. The application of macrocyclic gadolinium complexes as spin catalysts in the photooxidative hydroxylation of aromatic compounds, characterized in that... The structure of the macrocyclic gadolinium complex is shown in Formula II: ； Specifically, the steps include: adding a macrocyclic gadolinium complex as a spin catalyst to the photooxidative hydroxylation reaction system of aromatic compounds, and then conducting a photocatalytic redox reaction under light irradiation; The photooxidative hydroxylation reaction system of the aromatic compounds includes an organic photosensitizer, a substrate, and a solvent; The solvent is a mixture of an organic solvent and water, wherein the organic solvent is acetonitrile; the volume ratio of the organic solvent to water is 4:1; the organic photosensitizer is 3-cyano-1-methylquinoline salt; and the substrate is benzene.

3. The application of the macrocyclic gadolinium complex according to claim 1 as a spin catalyst in the dehalogenation hydrogenation photoredox reaction of haloaromatics, characterized in that: The concentration of the substrate haloaromatic hydrocarbon is 0.005-1 M; 0.001-0.2 mol of organic photosensitizer is added for every 1 mol of substrate haloaromatic hydrocarbon; 0.5-4 mol of reducing sacrificial agent is added for every 1 mol of substrate haloaromatic hydrocarbon. The amount of the macrocyclic gadolinium complex is such that after the macrocyclic gadolinium complex is added to the dehalogenation hydrogenation photoredox reaction system of haloaromatics, the concentration of the macrocyclic gadolinium complex is 0.1-50 mM.

4. The application of the macrocyclic gadolinium complex according to claim 1 as a spin catalyst in the dehalogenation hydrogenation photoredox reaction of haloaromatics, characterized in that: The photocatalytic oxidation-reduction reaction under illumination refers to the reaction at 25-50°C for 5 minutes to 10 hours in air or an inert atmosphere, where illumination refers to light irradiation at 365-550 nm.

5. The application of the macrocyclic gadolinium complex according to claim 1 as a spin catalyst in the dehalogenation hydrogenation photoredox reaction of haloaromatics, characterized in that: The volume ratio of the organic solvent to water is 9:1; when the concentration of the haloaromatic hydrocarbon is 0.1M, the corresponding concentration of the spin catalyst is 1.4 mM.

6. The application of the macrocyclic gadolinium complex according to claim 2 as a spin catalyst in the photooxidative hydroxylation reaction of aromatic compounds, characterized in that: The concentration of the substrate aromatic compound is 0.01–1 M; for every 1 mol of substrate aromatic compound, 0.01–0.2 mol of photosensitizer is added. The amount of the macrocyclic gadolinium complex is such that after the macrocyclic gadolinium complex is added to the photooxidative hydroxylation reaction system of the aromatic compound, the concentration of the macrocyclic gadolinium complex is 0.1-50 mM; The photocatalytic oxidation-reduction reaction under light conditions refers to the reaction at 25-50°C for 5 minutes to 10 hours in an air or O2 atmosphere, where the light conditions refer to light irradiation at 365-450 nm.

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