The invention relates to a tri (4, 4apos; -dimethyl-2, 2apos,-dimethyl-2, 2apos; preparation method of-dipyridyl) ruthenium hexafluorophosphate (II)

Abstract

The invention relates to the technical field of ruthenium coordination compound synthesis, in particular to a preparation method of tris (4, 4 '-dimethyl-2, 2'-dipyridyl) ruthenium hexafluorophosphate (II). According to the preparation method provided by the invention, a trivalent ruthenium source, 4, 4 '-dimethyl-2, 2'-dipyridyl and water-soluble hexafluorophosphate are taken as raw materials, water is taken as a solvent, monobasic acid and / or monobasic aldehyde with the carbon atom number of 1-2 are / is taken as a reducing agent, and tris (4, 4 '-dimethyl-2, 2'-dipyridyl) ruthenium hexafluorophosphate (II) is prepared with high yield through a one-pot method. According to the method, ruthenium (III) in a trivalent ruthenium source is reduced into ruthenium (II) by a reducing agent, meanwhile, the reduced ruthenium compound (II) is coordinated with 4, 4 '-dimethyl-2, 2'-dipyridyl to form tri (4, 4 '-dimethyl-2, 2'-dipyridyl) ruthenium (II) ions, and finally, the tri (4, 4 '-dimethyl-2, 2'-dipyridyl) ruthenium (II) ions react with water-soluble hexafluorophosphate to obtain a target product.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of synthesis of ruthenium coordination compounds, and particularly relates to a preparation method of tris(4,4'-dimethyl-2,2'-bipyridine) ruthenium (II) hexafluorophosphate. BACKGROUND

[0002] Tris(4,4'-dimethyl-2,2'-bipyridine) ruthenium (II) hexafluorophosphate (Ru(dmbpy)3(PF6)2) is an important ruthenium-based bipyridine complex, which is widely used in the fields of dye-sensitized solar cells, electrochemiluminescence sensors, biological imaging probes and organic electronic devices due to its excellent photochemical stability, reversible redox characteristics and unique fluorescence performance.

[0003] At present, Ru(dmbpy)3(PF6)2 is prepared by using ruthenium chloride (such as RuCl3·3H2O) or ruthenium nitrate as a ruthenium source, 4,4'-dimethyl-2,2'-bipyridine (dmbpy) as a ligand, ethylene glycol as a solvent and a reducing agent, and through coordination reaction under high-temperature reflux conditions to synthesize tris(4,4'-dimethyl-2,2'-bipyridine) ruthenium (II) chloride (Ru(dmbpy)3Cl2) first, and then obtain the target product through ion exchange of hexafluorophosphate (PF6-). The existing preparation process has a low yield of the target product, only 50-60%. SUMMARY

[0004] Therefore, the present application aims to provide a preparation method of tris(4,4'-dimethyl-2,2'-bipyridine) ruthenium (II) hexafluorophosphate. The method provided by the present application can be used to prepare tris(4,4'-dimethyl-2,2'-bipyridine) ruthenium (II) hexafluorophosphate, and the yield of the target product is high.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions. The present application provides a preparation method of tris(4,4'-dimethyl-2,2'-bipyridine) ruthenium (II) hexafluorophosphate, which comprises the following steps: A trivalent ruthenium source, 4,4'-dimethyl-2,2'-bipyridine, water and a reducing agent are mixed to perform an oxidation-reduction coordination reaction, so as to form tris(4,4'-dimethyl-2,2'-bipyridine) ruthenium (II) ions and obtain an intermediate system; the reducing agent is one or more of formic acid, acetic acid, formaldehyde and acetaldehyde; The intermediate system is mixed with a water-soluble hexafluorophosphate to perform an ion exchange reaction, so as to obtain the tris(4,4'-dimethyl-2,2'-bipyridine) ruthenium (II) hexafluorophosphate.

[0006] Preferably, the molar ratio of the trivalent ruthenium source and 4,4'-dimethyl-2,2'-bipyridine is 1:4-6.

[0007] Preferably, the molar ratio of the trivalent ruthenium source and the reducing agent is 1:4-8.

[0008] Preferably, the molar ratio of the trivalent ruthenium source and the water-soluble hexafluorophosphate salt is 1:4-7.

[0009] Preferably, the mass of the trivalent ruthenium source and the volume of water are in a ratio of 1g:5-12mL.

[0010] Preferably, the trivalent ruthenium source comprises ruthenium trichloride or ruthenium nitrate.

[0011] Preferably, the water-soluble hexafluorophosphate salt comprises potassium hexafluorophosphate or ammonium hexafluorophosphate.

[0012] Preferably, the temperature of the redox-ligand reaction is 94-100℃, and the time is 1-3h; the redox-ligand reaction is carried out under a protective atmosphere.

[0013] Preferably, the time of the ion exchange reaction is 0.5-1h; the ion exchange reaction is carried out under a protective atmosphere.

[0014] Preferably, after the ion exchange reaction is completed, the obtained reaction solution is subjected to solid-liquid separation, and the obtained solid is washed with water and dried.

[0015] The preparation method provided by the present application uses a trivalent ruthenium source, 4,4'-dimethyl-2,2'-bipyridine and a water-soluble hexafluorophosphate salt as raw materials, water as a solvent, a monobasic acid and / or a monobasic aldehyde with a carbon atom number of 1-2 as a reducing agent, and a one-pot method to prepare tris(4,4'-dimethyl-2,2'-bipyridine) ruthenium(II) hexafluorophosphate in a high yield. Specifically, under the action of the reducing agent, the ruthenium(III) in the trivalent ruthenium source is reduced to ruthenium(II), and at the same time, the reduced ruthenium compound(II) is coordinated with 4,4'-dimethyl-2,2'-bipyridine to form tris(4,4'-dimethyl-2,2'-bipyridine) ruthenium(II) ions, which then react with the water-soluble hexafluorophosphate salt to form tris(4,4'-dimethyl-2,2'-bipyridine) ruthenium(II) hexafluorophosphate. The ligand utilization rate is high in the entire reaction process, the side reactions are few, and the yield of the target product is high.

[0016] In addition, since the target product is insoluble in water, the purification step is simplified, which is conducive to improving the yield of tris(4,4'-dimethyl-2,2'-bipyridine) ruthenium(II) hexafluorophosphate. In the background art, the purification method often uses column silica gel separation technology, which is complex, increases the consumption of organic solvents (such as acetonitrile and methanol), and causes the loss rate of the target product to exceed 15%.

[0017] The solvent of this invention is water, which is safe and environmentally friendly, can reduce environmental pollution, and can also reduce preparation costs.

[0018] The preparation method of the present invention adopts a one-pot redox-coordination reaction, which has fewer steps, is easy to operate, and has a high yield of tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate; it does not require high-end equipment, and the amount of raw materials can reach the hundred-gram level, which can realize mass industrial production. Attached Figure Description

[0019] Figure 1 The 1H NMR spectrum of tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate prepared in Example 1; Figure 2 The carbon spectrum of tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate prepared in Example 1; Figure 3 The mass spectrum of tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate prepared in Example 1; Figure 4 The infrared spectrum of tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate prepared in Example 1. Detailed Implementation

[0020] This invention provides a method for preparing tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate, comprising the following steps: A trivalent ruthenium source, 4,4'-dimethyl-2,2'-bipyridine, water, and a reducing agent are mixed and subjected to a redox-coordination reaction to form tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) ions, yielding an intermediate system; the reducing agent is one or more of formic acid, acetic acid, formaldehyde, and acetaldehyde; The intermediate system was mixed with water-soluble hexafluorophosphate and subjected to an ion exchange reaction to obtain tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium hexafluorophosphate(II).

[0021] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0022] This invention involves mixing a trivalent ruthenium source, 4,4'-dimethyl-2,2'-bipyridine, water, and a reducing agent to carry out a redox-coordination reaction, forming tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) ions, thus obtaining an intermediate system.

[0023] In this invention, the trivalent ruthenium source preferably includes ruthenium trichloride or ruthenium nitrate, more preferably ruthenium trichloride. In this invention, the ruthenium trichloride is preferably hydrated ruthenium trichloride, specifically ruthenium trichloride monohydrate or ruthenium trichloride trihydrate. In this invention, hydrated ruthenium trichloride has good solubility, which is beneficial for the redox-coordination reaction.

[0024] In this invention, the molar ratio of the trivalent ruthenium source to 4,4'-dimethyl-2,2'-bipyridine is preferably 1:4 to 6, and in specific embodiments it can be 1:4, 1:5, or 1:6; the mass ratio of the trivalent ruthenium source to the volume ratio of water is preferably 1g:6 to 12mL, and in specific embodiments it can be 1g:6mL, 1g:8mL, 1g:10mL, or 1g:12mL; the molar ratio of the trivalent ruthenium source to the reducing agent is preferably 1:4 to 8, and in specific embodiments it can be 1:4, 1:5, 1:6, 1:7, or 1:8. In this invention, the reducing agent is preferably one or more of formic acid, acetic acid, formaldehyde, and acetaldehyde. Since pure formaldehyde and acetaldehyde are not commercially available, in this invention, formaldehyde and acetaldehyde are preferably used in the form of aqueous aldehyde solutions. This invention does not impose a special limitation on the concentration of the aqueous aldehyde solution; commercially available products are acceptable. In an embodiment of the present invention, specifically, a 40% formaldehyde aqueous solution and a 40% acetaldehyde aqueous solution are purchased.

[0025] In this invention, the mixing of trivalent ruthenium source, 4,4'-dimethyl-2,2'-bipyridine, water and reducing agent preferably includes: first mixing trivalent ruthenium source, 4,4'-dimethyl-2,2'-bipyridine and water, stirring and heating to reflux, and then adding reducing agent to the resulting mixture.

[0026] In this invention, the reducing agent is preferably added dropwise. The invention does not impose special requirements on the dropping rate; it can be added dropwise, for example, at a rate of 5-10 mL / min. Specifically, the dropping rate can be 5 mL / min, 7 mL / min, 8 mL / min, or 10 mL / min. By using a dropwise addition method, the reducing agent can fully contact the other raw materials, rapidly reducing ruthenium(III) in the trivalent ruthenium source to ruthenium(II), which not only makes the reaction more complete but also shortens the time of the redox-coordination reaction.

[0027] In this invention, the reflux temperature is the same as the temperature of the redox-coordination reaction. The preferred temperature of the redox-coordination reaction is 94~100℃, and in specific embodiments it can be 94℃, 95℃, 96℃, 97℃, 98℃, 99℃, or 100℃; the preferred time of the redox-coordination reaction is 1~3 hours, and in specific embodiments it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. In this invention, the time of the redox-coordination reaction refers to the time starting from when the reducing agent is completely added.

[0028] The synthesis methods mentioned in the background art require high-temperature reflux, exceeding 190°C. High temperatures may generate amorphous ruthenium-based impurities, which are difficult to remove during subsequent purification, affecting product purity (often below 98%) and failing to meet the requirements of high-end electronic devices or biological detection. The present invention uses a low reaction temperature, avoiding the formation of high-temperature impurities, and ultimately yields tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate with high purity, exceeding 99%.

[0029] In this invention, the redox-coordination reaction is preferably carried out under reflux conditions and a protective atmosphere; the protective atmosphere is preferably a nitrogen atmosphere or an argon atmosphere. By carrying out the redox-coordination reaction under a protective atmosphere, this invention can prevent the target product from being oxidized by oxygen in the air and reduce side reactions.

[0030] In the redox-coordination reaction process of this invention, the reducing agent reduces ruthenium(III) in the trivalent ruthenium source to ruthenium(II). Simultaneously, the reduced ruthenium compound(II) coordinates with 4,4'-dimethyl-2,2'-bipyridine to form tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) ions. When the ruthenium source is ruthenium trichloride, the product formed after the redox-coordination reaction is tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) chloride.

[0031] After completing the redox-coordination reaction, the present invention preferably cools to room temperature to obtain an intermediate system.

[0032] After obtaining the intermediate system, the present invention mixes the intermediate system with water-soluble hexafluorophosphate and carries out an ion exchange reaction.

[0033] In this invention, water-soluble hexafluorophosphate is preferably added to the intermediate system for mixing.

[0034] In this invention, the water-soluble hexafluorophosphate preferably comprises potassium hexafluorophosphate or ammonium hexafluorophosphate; the molar ratio of the trivalent ruthenium source to the water-soluble hexafluorophosphate is preferably 1:4 to 7, and in specific embodiments it can be 1:4, 1:5, 1:6 or 1:7. In this invention, the ion exchange reaction is preferably carried out at room temperature, i.e., no additional heating or cooling is required; the ion exchange reaction time is preferably 0.5 to 1 hour, and in specific embodiments it can be 0.5 hours or 1 hour; the ion exchange reaction is preferably carried out under a protective atmosphere; the protective atmosphere is preferably a nitrogen atmosphere or an argon atmosphere. This invention preferably carries out the ion exchange reaction under stirring conditions. During the ion exchange reaction, the hexafluorophosphate ion replaces the anion in the redox-coordination reaction product to form the target product tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate.

[0035] After the ion exchange reaction is completed, the present invention preferably further includes solid-liquid separation of the obtained reaction solution, washing and drying the obtained solid with water to obtain tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate.

[0036] This invention does not have special requirements for the solid-liquid separation method; any solid-liquid separation method well-known in the art, such as filtration, can be used. In this invention, the number of water washes is preferably 1 to 2 times, specifically 1 or 2 times. In this invention, the target product tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate is insoluble in water, but it can wash away unreacted water-soluble hexafluorophosphate, thereby improving the purity of the target product.

[0037] In this invention, the drying temperature is preferably 50~70℃, specifically 50℃, 60℃ or 70℃; the drying time is preferably 3~5h, specifically 3h, 4h or 5h.

[0038] The following detailed description of the preparation method of tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate provided by the present invention, with reference to the embodiments, is not intended to limit the scope of protection of the present invention.

[0039] Example 1 0.37 mol of ruthenium trichloride trihydrate (ruthenium content 37.24%) and 1.48 mol of 4,4'-dimethyl-2,2'-bipyridine were added to the reaction mixture, followed by 600 mL of water. Under argon protection, the mixture was stirred and heated to 94 °C. Then, 1.48 mol of formic acid was added dropwise to the reaction flask at a rate of 5 mL / min. After the addition was complete, the mixture was refluxed for 1 h. After cooling to room temperature, 1.48 mol of potassium hexafluorophosphate was added under argon protection, and the mixture was stirred and reacted at room temperature for 0.5 h. The mixture was filtered, and the filter cake was washed twice with distilled water and dried at 50 °C for 3 h to obtain 341.52 g of red solid tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium hexafluorophosphate(II), with a yield of 98.22% and a purity of 99.01% based on ruthenium.

[0040] Example 2 0.37 mol of ruthenium trichloride trihydrate (ruthenium content 37.24%) and 1.85 mol of 4,4'-dimethyl-2,2'-bipyridine were added to the reaction mixture, followed by 800 mL of water. Under argon protection, the mixture was stirred and heated to 96 °C. Then, 1.85 mol of acetic acid was added dropwise to the reaction flask at a rate of 7 mL / min. After the addition was complete, the mixture was refluxed for 2 h. After cooling to room temperature, 1.85 mol of potassium hexafluorophosphate was added under argon protection, and the mixture was stirred for another 1 h at room temperature. The mixture was filtered, and the filter cake was washed twice with distilled water and dried at 60 °C for 4 h to obtain 341.42 g of red solid tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium hexafluorophosphate(II), with a yield of 98.19% and a purity of 99.01% based on ruthenium.

[0041] Example 3 0.37 mol of ruthenium trichloride trihydrate (ruthenium content 37.24%) and 2.22 mol of 4,4'-dimethyl-2,2'-bipyridine were added to the reaction mixture, followed by 1000 mL of water. Under argon protection, the mixture was stirred and heated to 98 °C. Then, 166.68 g of 2.22 mol of 40% formaldehyde aqueous solution was added dropwise to the reaction flask at a rate of 8 mL / min. After the addition was complete, the mixture was refluxed for 3 h. After cooling to room temperature, 408.61 g of 2.22 mol of potassium hexafluorophosphate was added under argon protection, and the mixture was stirred and reacted for another 1 h at room temperature. The mixture was filtered, and the filter cake was washed twice with distilled water and dried at 70 °C for 5 h to obtain 341.62 g of red solid tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate, with a yield of 98.25% and a purity of 99.01% based on ruthenium.

[0042] Example 4 0.37 mol of ruthenium trichloride trihydrate (ruthenium content 37.24%) and 1.85 mol of 4,4'-dimethyl-2,2'-bipyridine were added to the reaction mixture, followed by 1200 mL of water. Under argon protection, the mixture was stirred and heated to 100 °C. Then, 2.96 mol of 40% acetaldehyde was added dropwise to the reaction flask at a rate of 10 mL / min. After the addition was complete, the mixture was refluxed for 3 h. After cooling to room temperature, 2.96 mol of potassium hexafluorophosphate was added under argon protection, and the mixture was stirred for another 1 h at room temperature. The mixture was filtered, and the filter cake was washed twice with distilled water and dried at 60 °C for 6 h to obtain 341.72 g of red solid tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate, with a yield of 98.27% and a purity of 99.01% based on ruthenium.

[0043] Comparative Example 1 0.37 mol of ruthenium trichloride trihydrate (ruthenium content 37.24%) and 1.85 mol of 4,4'-dimethyl-2,2'-bipyridine were added to the reaction mixture, followed by 1200 mL of ethylene glycol. Under argon protection, the mixture was stirred and heated to reflux at 196 °C, and the reaction was continued under reflux for 5 h. After cooling to room temperature, 2.96 mol of potassium hexafluorophosphate was added under argon protection, and the reaction was continued under stirring at room temperature for 1 h. After filtration, the ethylene glycol was found to be very viscous. The filter cake was washed twice with distilled water and dried at 60 °C for 24 h. 1H NMR spectroscopy revealed residual ethylene glycol solvent. The sample was then re-dissolved in acetonitrile and passed through a silica gel column to obtain 241.02 g of red solid tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium hexafluorophosphate(II), with a yield of 69.31% and a purity of 98.02% based on ruthenium.

[0044] Comparative Example 2 The only difference from Example 1 is that the reducing agent formic acid is replaced with propionic acid. The specific steps are as follows: 0.37 mol of ruthenium trichloride trihydrate (ruthenium content 37.24%) and 1.48 mol of 4,4'-dimethyl-2,2'-bipyridine were added to the reaction mixture, followed by 600 mL of water. Under argon protection, the mixture was stirred and heated to 94 °C. Then, 1.48 mol of propionic acid was added dropwise to the reaction flask at a rate of 5 mL / min. After the addition was complete, the mixture was refluxed for 1 h. The mixture was cooled to room temperature, and then 1.48 mol of potassium hexafluorophosphate was added under argon protection. The mixture was stirred and reacted at room temperature for 0.5 h. The mixture was filtered, and the filter cake was washed twice with distilled water and dried at 50 °C for 3 h to obtain 150.02 g of a mixed solid of red and black. Due to the weak reducing power of propionic acid, it is possible that only part of the ruthenium(III) was reduced, resulting in a mixed solid.

[0045] Comparative Example 3 The only difference from Example 1 is that the reducing agent formic acid is replaced with hydrazine hydrate. The specific steps are as follows: 0.37 mol of ruthenium trichloride trihydrate (ruthenium content 37.24%) and 1.48 mol of 4,4'-dimethyl-2,2'-bipyridine were added to the reaction mixture, followed by 600 mL of water. Under argon protection, the mixture was stirred and heated to 94 °C. Then, 1.48 mol of hydrazine hydrate was added dropwise to the reaction flask at a rate of 5 mL / min. After the addition was complete, the mixture was refluxed for 1 h. The reaction produced a large number of bubbles and was quite vigorous, making large-scale production difficult. The mixture was cooled to room temperature, and then 1.48 mol of potassium hexafluorophosphate was added under argon protection. The mixture was stirred and reacted for another 0.5 h at room temperature. The mixture was filtered, and the filter cake was washed twice with distilled water and dried at 50 °C for 3 h to obtain 306.00 g of red solid tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate, with a yield of 88.00% and a purity of 99.01% based on ruthenium.

[0046] Test case The tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate obtained in Example 1 was characterized, and the resulting proton NMR spectrum is shown below. Figure 1 As shown, the carbon spectrum is as follows Figure 2 As shown, the mass spectrum is as follows Figure 3 As shown, the red light spectrum is as follows: Figure 4 As shown.

[0047] Depend on Figure 1 As can be seen, the hydrogen spectrum ( 1 ¹H NMR (500 MHz, DMSO), chemical shifts (ppm): 8.67 (s, 7H), 7.53 (d, J = 5.8 Hz, 7H), 7.36–7.30 (m, 7H), 2.06 (s, 9H).

[0048] Depend on Figure 2 As can be seen, carbon spectrum ( 13 C NMR (500 MHz, DMSO), chemical shifts (ppm): 156.21, 150.27, 149.34, 128.47, 124.97, 20.72.

[0049] Depend on Figure 3 As can be seen, mass spectrometry (ESI(+)): m / z = 799 (calcd. 944 for [C 36 H 36 [N6P2F6Ru], [M-2PF6] + [C 36 H 24 ClN6Ru] + .

[0050] Depend on Figure 4 It can be seen that IR (KBr cm) -1 ): 3118, 3082, 2962, 2926, 1620, 1448, 1382, 1303, 1241, 1224, 844, 557.

[0051] Figures 1 to 4 The detection results showed that the product obtained in Example 1 was consistent with the target compound tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate.

[0052] As can be seen from the above embodiments, the preparation method provided by the present invention is a simple, high-yield, low-cost, and efficient method for synthesizing tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate, which is suitable for mass industrial production.

[0053] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) hexafluorophosphate, characterized in that, Includes the following steps: A trivalent ruthenium source, 4,4'-dimethyl-2,2'-bipyridine, water, and a reducing agent are mixed and subjected to a redox-coordination reaction to form tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium(II) ions, yielding an intermediate system; the reducing agent is one or more of formic acid, acetic acid, formaldehyde, and acetaldehyde; The intermediate system was mixed with water-soluble hexafluorophosphate and subjected to an ion exchange reaction to obtain tris(4,4'-dimethyl-2,2'-bipyridine)ruthenium hexafluorophosphate(II).

2. The preparation method according to claim 1, characterized in that, The molar ratio of the trivalent ruthenium source to 4,4'-dimethyl-2,2'-bipyridine is 1:4~6.

3. The preparation method according to claim 1, characterized in that, The molar ratio of the trivalent ruthenium source to the reducing agent is 1:4~8.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the trivalent ruthenium source to the water-soluble hexafluorophosphate is 1:4~7.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the trivalent ruthenium source to the volume of water is 1 g: 5~12 mL.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The trivalent ruthenium source includes ruthenium trichloride or ruthenium nitrate.

7. The preparation method according to claim 1 or 4, characterized in that, The water-soluble hexafluorophosphate includes potassium hexafluorophosphate or ammonium hexafluorophosphate.

8. The preparation method according to any one of claims 1 to 5, characterized in that, The redox-coordination reaction is carried out at a temperature of 94~100℃ for 1~3h; the redox-coordination reaction is carried out under a protective atmosphere.

9. The preparation method according to claim 1, characterized in that, The ion exchange reaction takes 0.5 to 1 hour and is carried out under a protective atmosphere.

10. The preparation method according to claim 1 or 9, characterized in that, After the ion exchange reaction is completed, the process also includes solid-liquid separation of the resulting reaction solution, and washing and drying of the resulting solid.

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