A PN ligand and a PN ligand modified Au cluster capable of cis-trans isomerization

Abstract

The application provides a cis-trans isomerizable PN ligand and a PN ligand modified Au cluster, and a PN ligand modified Au cluster with high photo-thermal conversion efficiency is prepared through the cis-trans isomerizable PN ligand.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal cluster materials, and particularly relates to a PN ligand capable of cis-trans isomerization and a PN ligand modified Au cluster. BACKGROUND

[0002] The current photo-thermal conversion materials, such as gold (Au), silver (Ag) and copper (Cu), have two most basic characteristics: one is that they need to have obvious absorption to a certain specific waveband of light, and the other is that they can effectively convert the absorbed light energy into heat energy. For example, the noble metal Au and Ag have obvious absorption in the visible light region and near-infrared light region due to their local surface plasmon resonance (SPR) effect, and the waveband of the absorbed light can be accurately controlled through morphology change.

[0003] However, the current photo-thermal conversion materials still have defects in photo-thermal conversion efficiency and the like. Gold clusters have attracted more and more attention of scientists due to their clear and unique molecular structure and application in the fields of light emission and catalysis. Therefore, it is very important to seek a preparation method of Au clusters with high photo-thermal conversion efficiency. SUMMARY

[0004] Based on the above technical problems, the application provides a PN ligand capable of cis-trans isomerization and a PN ligand modified Au cluster. Through the PN ligand capable of cis-trans isomerization under light, a PN ligand modified Au cluster with high photo-thermal conversion efficiency is prepared.

[0005] The application provides a PN ligand capable of cis-trans isomerization, and the trans structure formula of the PN ligand is as follows:

[0006]

[0007] The cis structure formula of the PN ligand is as follows:

[0008]

[0009] wherein R1 and R2 are each independently at least one of hydrogen, halogen, alkyl, halogenated alkyl, amino, cyano, nitro, hydroxyl, mercapto, alkoxy, alkenyl, alkynyl, cycloalkyl, aryl or heteroaryl.

[0010] Preferably, the structure formula of the PN ligand is as shown in the following formula I and II:

[0011]

[0012] Preferably, the synthesis route of the PN ligand is as shown in the following formula:

[0013]

[0014] The application further provides a PN ligand modified Au cluster, which has a general molecular formula of Au 21 (PN)8X2;

[0015] The structure of the PN ligand is as shown in the following formula:

[0016]

[0017] R1 and R2 are each independently at least one of hydrogen, halogen, alkyl, haloalkyl, amino, cyano, nitro, hydroxyl, thiol, alkoxy, alkenyl, alkynyl, cycloalkyl, aryl or heteroaryl;

[0018] X is an anion group.

[0019] Preferably, the structure of the PN ligand is as shown in the following formula I:

[0020]

[0021] Preferably, X is halogen, preferably Cl.

[0022] Preferably, the application further provides a preparation method of the PN ligand modified Au cluster, which comprises: adding a gold source and a PN ligand into a solvent to completely dissolve, and then adding a reducing agent to reduce, so that the Au cluster is obtained.

[0023] Preferably, the gold source is at least one of chloroauric acid, gold trichloride, gold oxide or a gold complex;

[0024] Preferably, the molar ratio of the gold source and the PN ligand is 1:1-3.

[0025] Preferably, the reducing agent is at least one of NaBH4, vitamin C or NaBH3CN;

[0026] Preferably, the molar ratio of the reducing agent and the gold source is 4-6:1.

[0027] The application further provides an application of the Au cluster or the Au cluster prepared by the preparation method in a photothermal conversion material.

[0028] Advantages:

[0029] (1) The application provides a cis-trans isomerizable PN ligand and a PN ligand modified Au cluster, and the Au cluster has a high photothermal conversion efficiency in a near-infrared region, so that the application of the photothermal conversion material is expanded.

[0030] (2) The application provides a preparation method of the PN ligand modified Au cluster, and the preparation method has mild reaction conditions and is simple and easy to implement.

[0031] (3) The present invention provides an application of PN ligand modified Au clusters, which can be used as photothermal conversion materials in the fields of photothermal conversion. Attached Figure Description

[0032] Figure 1 This is the proton spectrum of the trans-PN ligand that is cis-trans isomerizable according to an embodiment of the present invention;

[0033] Figure 2 This is the carbon spectrum of the trans-PN ligand capable of cis-trans isomerization described in the embodiments of the present invention;

[0034] Figure 3 This is the phosphorus spectrum of the trans-PN ligand that is cis-trans isomerizable according to an embodiment of the present invention;

[0035] Figure 4 This is the proton spectrum of the cis-trans isomerizable cis-PN ligand described in the embodiments of the present invention;

[0036] Figure 5 This is the carbon spectrum of the cis-trans isomerizable cis-PN ligand described in the embodiments of the present invention;

[0037] Figure 6 This is the phosphorus spectrum of the cis-trans isomerizable cis-PN ligand described in the embodiments of the present invention;

[0038] Figure 7 Au as described in the embodiments of the present invention 21 Mass spectrum of the cluster;

[0039] Figure 8 Au as described in the embodiments of the present invention 21 Crystal diffraction pattern of the cluster;

[0040] Figure 9 Au as described in the embodiments of the present invention 21 UV-Vis absorption spectrum of the cluster;

[0041] Figure 10 Au as described in the embodiments of the present invention 21 TLC chromatogram of the cluster;

[0042] Figure 11 Au as described in the embodiments of the present invention 21 Light conversion diagram of clusters: a is Au as described in the example 21 TLC chromatograms of clusters after illumination under different conditions, b is the Au described in the example. 21 UV-Vis absorption spectra of clusters after illumination under different conditions;

[0043] Figure 12 Au as described in the embodiments of the present invention 21The infrared thermal imaging instrument real-time monitoring temperature and irradiation time results of the clusters after irradiation under different conditions: a and b correspond to the irradiation conditions of concentration 1 mg / mL, wavelength 785 nm, and power 0.6 W; c and d correspond to the irradiation conditions of concentration 0.5 mg / mL, wavelength 785 nm, and power 1 W;

[0044] Figure 13 The Au clusters described in the embodiment of the present application 21 The photothermal conversion curve of the clusters under the conditions of wavelength 785 nm, laser intensity 0.6 W / cm 2 , and concentration 1.0 mg / mL: a is the photothermal conversion and cooling curve of the Au clusters described in the embodiment of the present application, and b is the linear curve of the corresponding time and lnθ; 21

[0045] Figure 14 The Au clusters described in the embodiment of the present application 21 The photothermal conversion curve of the clusters under the conditions of wavelength 785 nm, laser intensity 1.0 W / cm 2 , and concentration 0.5 mg / mL: a is the photothermal conversion and cooling curve of the Au clusters described in the embodiment of the present application, and b is the linear curve of the corresponding time and lnθ; 21

[0046] Figure 15 The Au clusters described in the embodiment of the present application 21 The temperature change graph of the clusters after irradiation under the condition of wavelength 785 nm for five cycles;

[0047] Figure 16 The Au clusters described in the embodiment of the present application 21 The ultraviolet-visible absorption spectrum graph of the clusters after irradiation under different conditions. DETAILED DESCRIPTION

[0048] Hereinafter, the technical solutions are described in detail by the embodiments of the present application, but it should be clear that these embodiments are used for illustration, but not to be interpreted as limiting the scope of the present application.

[0049] EMBODIMENT

[0050] The present embodiment provides a trans-PN ligand capable of cis-trans isomerization, and the structural formula is shown in formula I as follows:

[0051]

[0052] The preparation method of the above-mentioned trans-PN ligand capable of cis-trans isomerization comprises:

[0053]

[0054] ​​(1) Dissolve 12 mmol of 2-methylquinoline in 50 mL of anhydrous and oxygen-free tetrahydrofuran (THF). Under nitrogen protection, place the solution at -78 °C and slowly add 6 mL of 2.0 M lithium diisopropylamino (LDA) solution. After stirring at -78 °C for 1 h, the solution gradually turns into a red viscous liquid. Dissolve 10 mmol of 2-diphenylphosphine benzaldehyde powder in anhydrous and oxygen-free tetrahydrofuran solution and add it dropwise to the above red viscous liquid. Gradually restore the solution to room temperature and stir for 12 h. After the reaction is complete, add water and extract the mixture with ethyl acetate. Dry the mixture with anhydrous sodium sulfate and concentrate it under vacuum. Purify the mixture by silica gel column chromatography to obtain the intermediate with a yield of 92%.

[0055]

[0056] (2) Dissolve the intermediate in 100 mL of toluene (Tol), add p-toluenesulfonic acid (0.1 eq.) to the resulting toluene solution, heat to 110 °C in an oil bath under nitrogen protection, reflux for 12 h, cool to room temperature after completion, concentrate under vacuum, and purify the mixture by silica gel column chromatography to obtain the final product, which is the trans PN ligand, with a yield of 71%.

[0057] This embodiment also proposes a cis-trans isomerizable cis-PN ligand, the structural formula of which is shown in Formula II below:

[0058]

[0059] The preparation methods of the above-mentioned cis-trans isomerizable cis-PN ligands include:

[0060]

[0061] The trans-PN ligand was dissolved in dichloromethane (DCM), irradiated for 3 hours under nitrogen protection at a wavelength of 400 nm and a power of 3 W, concentrated under vacuum, and purified by silica gel column chromatography to obtain the final product, which is the cis-PN ligand, with a yield of 75%.

[0062] The trans-PN ligands and cis-PN ligands prepared in the examples were analyzed by proton, carbon, and phosphorus spectra, and the results are as follows: Figures 1-6 As shown, refer to Figures 1-6 It can be seen that the chemical shifts of the olefin hydrogens of the trans PN ligand are 7.76 and 8.10, while the chemical shifts of the olefin hydrogens of the cis PN ligand are 7.70 and 7.94.

[0063] The specific NMR data for the trans-PN ligand are as follows:

[0064] Hydrogen spectrum: 1H NMR (400 MHz, CD2CI2) δ 6.96 (dd, 1 H), 7.24 (t, 2 H), 7.34 (d, 11 H), 7.42 (t, 1 H), 7.48 (t, 1 H), 7.54 (d, 1 H), 7.68 (t, 1 H), 7.77 (d, 1 H), 7.86 (dd, 1 H), 8.00 (d, 1 H), 8.09 (d, 1 H), 8.38 (dd, 1 H).

[0065] Carbon spectrum: 13 C NMR (101 MHz, CD2CI2) δ 119.41, 126.42, 126.46, 126.61, 127.76, 127.89, 128.94, 128.99, 129.06, 129.28, 129.51, 129.66, 130.03, 134.00, 134.31, 134.51, 136.66, 136.76, 136.86, 137.10, 137.25, 141.42, 141.64, 156.35.

[0066] Phosphorus spectrum: 31 P NMR (162 MHz, CD2CI2) δ -13.79.

[0067] Specific NMR data for the cis PN ligand are as follows:

[0068] Hydrogen spectrum: 1 H NMR (400 MHz, CD2CI2) δ 6.80 (t, 2 H), 7.01 (dd, 1 H), 7.1 1 - 7.25 (m, 3 H), 7.33 (q, 1 1 H), 7.48 (t, 1 H), 7.66 (t, 1 H), 7.73 (dd, 2 H), 7.95 (d, 1 H).

[0069] Carbon spectrum: 13 C NMR (101 MHz, CD2CI2) δ 121.78, 126.44, 127.00, 127.51, 128.1 1, 128.65, 128.72, 128.98, 129.13, 129.46, 130.17, 130.22, 132.02, 133.08, 134.15, 134.34, 134.99, 136.23, 136.33, 137.06, 137.19, 142.02, 142.28, 156.49.

[0070] Phosphorus spectrum: 31 P NMR (162 MHz, CD2CI2) δ -13.19.

[0071] This embodiment also proposes a PN ligand-modified Au cluster with the general molecular formula [Au]. 21 (PN)8Cl2] + Au 21 Cluster is used as an abbreviation;

[0072] The structural formula of the PN ligand is shown in Equation I below:

[0073]

[0074] The preparation method of the above-mentioned PN ligand-modified Au clusters includes:

[0075] (1) PN ligands were prepared according to the aforementioned method;

[0076] (2) HAuCl4·4H2O (0.25 mmol) and PN ligand (200 mg, 0.5 mmol) were simultaneously added to 20 mL of ethanol. After stirring for 10 min, the solution changed from a pale yellow turbidity to a clear solution, and then gradually became a yellow suspension. NaBH4 (1.25 mmol) was dissolved in 4 mL of ultrapure water and then quickly added to the above yellow suspension. The solution quickly turned black. After stirring for 4 h, the reaction solution was concentrated to about 5 mL by rotary evaporation. After washing twice with petroleum ether and ethyl acetate (10:1), it was extracted with 15 mL of dichloromethane. After rotary evaporation and concentration, it was separated by thin-layer chromatography to obtain the PN ligand-modified Au cluster, abbreviated as Au. 21 Cluster.

[0077] The Au obtained in the above embodiments 21 Mass spectrometry characterization and crystal diffraction were performed, and the results are as follows: Figure 7 , 8 As shown, refer to Figure 7 , 8 The structural formula and spatial structure of the Au cluster modified by the PN ligand are known. 21 The crystallographic data of the clusters are shown in Table 1 below:

[0078] Table 1

[0079]

[0080]

[0081] The Au obtained in the above embodiments 21 The clusters were dissolved in dichloromethane, and their ultraviolet-visible spectra were measured. The results are as follows: Figure 9 As shown, refer to Figure 9 It can be seen that Au 21 The cluster has major absorption peaks at 413 nm, 457 nm, and 593 nm.

[0082] Au 21 The crude product of the clusters was dissolved in dichloromethane and uniformly coated onto a thin-layer chromatography plate. TLC chromatograms were obtained using dichloromethane (DCM):methanol (MeOH) at a solvent ratio of 20:1. The results are as follows: Figure 10 As shown, refer to Figure 10 It can be seen that Au 21 After the clusters separated from the mixture, the largest reddish-brown portion of the separation zone indicated that Au... 21 Clusters account for a high percentage of the content.

[0083] Au 21 The crude product of the cluster was dissolved in ethanol (EtOH) and irradiated for one day under illumination conditions of 400 nm-24 W (Purple), 450 nm-24 W (Blue 24 W), and 450 nm-40 W (Blue 40 W), respectively. Three product bands, corresponding to 1, 2, and 3, were obtained by TLC separation, as shown in the figure. Figure 11 As shown, refer to Figure 11 It can be seen that under different lighting conditions, Au 21 Clusters can transform, where the UV peaks of the two product bands corresponding to 1 and 2 differ from the original Au. 21 The different clusters indicate the formation of new clusters, while the UV peak of the product band corresponding to 3 differs from the original Au. 21 Like clusters, this is the part that has not changed.

[0084] Au 21 The clusters were dissolved in 1 mL of toluene to prepare concentrations of 0.5 mg / mL and 1 mg / mL. The solutions were then irradiated with laser light at a wavelength of 785 nm and a power of 0.6 W or 1.0 W. Temperature changes were recorded by taking photos at 30-second intervals using a thermometric infrared camera. After 10 minutes of irradiation, the irradiation was stopped, but photography continued until the 18th minute. The results are as follows: Figure 12 As shown, refer to Figure 12 As can be seen, an image is taken every 30 seconds. The first 21 images are the heating curves under illumination, and the last 15 images are the cooling curves when illumination stops. The photothermal efficiency is obtained by calculating the temperature using the formula and fitting the data.

[0085] The photothermal conversion efficiency is calculated using the following formula:

[0086] Calculate the overall energy balance of the system:

[0087]

[0088] Where m i and c pi Q is the system's mass and heat capacity, Qs is the photothermal energy input when the laser irradiates the sample, and Q is the system's mass and heat capacity. lossis the heat loss to the surroundings;

[0089] When the temperature reaches a maximum, the system is in equilibrium, so:

[0090] Q S = Q loss = hsΔT max

[0091] where h is the heat transfer coefficient, s is the surface area of the container, ΔT max is the change in temperature from the maximum;

[0092] The photo-thermal conversion efficiency η is calculated as follows:

[0093]

[0094] where I is the laser power, A 785 is the absorbance of the sample at 785 nm wavelength;

[0095] To obtain hS, a dimensionless driving force temperature, θ, is introduced as follows:

[0096]

[0097] When T is the sample temperature, T max is the maximum temperature of the system, and T surr is the initial temperature;

[0098] The sample system time constant τ s

[0099]

[0100]

[0101] When the laser is off,

[0102] Q S = 0

[0103]

[0104] t = -τ s ln θ

[0105] The thermal stability of the sample (hS) can be calculated from the slope of the cooling time versus ln θ.

[0106] The photo-thermal conversion efficiency of the Au 21 clusters prepared in the above examples is shown in Table 2 below:

[0107] Table 2

[0108]

[0109]

[0110] *: h is the heat transfer coefficient; s is the surface area of ​​the container.

[0111] As shown in Table 2, with the increase of laser wavelength, the maximum photothermal conversion efficiency can be obtained at a wavelength of 785nm, which can basically reach about 75%.

[0112] in, Figure 13 (a) is the Au described in the example. 21 The clusters were observed at a wavelength of 785 nm with a laser intensity of 0.6 W / cm². 2 Photothermal conversion and cooling curves at a concentration of 1.0 mg / mL. Figure 13 (b) is a linear curve of the corresponding time versus lnθ; Figure 14 (a) is the Au described in the example. 21 The clusters were observed at a wavelength of 785 nm with a laser intensity of 1.0 W / cm². 2 Photothermal conversion and cooling curves at a concentration of 0.5 mg / mL. Figure 14 (b) is the linear curve of the corresponding time versus lnθ.

[0113] The Au obtained in the above embodiments 21 Clusters were irradiated with laser at a wavelength of 785 nm, a power of 1.0 W, and a concentration of 1.0 mg / mL. One heating and cooling cycle was performed, consisting of 10 min of laser irradiation followed by 10 min of cooling. After five heating and cooling cycles, the temperature changes were recorded. The results are shown below. Figure 15 As shown, refer to Figure 15 It can be seen that even after 5 heating and cooling cycles, Au 21 The clusters still maintain excellent and stable photothermal properties; meanwhile, due to the highest temperature rise at 1.0 W-1.0 mg / mL under 785 nm conditions, Au 21 The fact that the cluster can still cycle stably under this condition indicates that it can also cycle stably under other conditions.

[0114] The Au obtained in the above embodiments 21 Clusters were irradiated with lasers under different power and concentration conditions, and their ultraviolet-visible spectra were measured. The results are as follows: Figure 16 As shown, refer to Figure 16 It can be seen that after the photothermal efficiency test, Au 21 The ultraviolet-visible absorption spectra of the clusters are basically consistent, further illustrating that Au 21 The clusters exhibit good photothermal stability.

[0115] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A cis-trans isomerizable PN ligand, characterized in that, The trans structure of the PN ligand is shown in the following formula I: The cis structure of the PN ligand is shown in the following formula II:

2. The switchable PN ligand according to claim 1, wherein The synthesis route of the PN ligand is shown as follows:

3. A PN ligand modified Au cluster, characterized in that, The molecular formula of the Au cluster is Au 21 (PN)8X2; The structure of the PN ligand is shown in the following formula I: X is an anion group.

4. The PN ligand modified Au cluster of claim 3, wherein, X is halogen.

5. The PN ligand modified Au cluster of claim 4, wherein, X is Cl.

6. A method for preparing the PN ligand modified Au cluster of any one of claims 3-5, characterized in that, Comprising: The gold source and the PN ligand are dissolved in a solvent, and then a reducing agent is added for reduction, to obtain the Au cluster.

7. The method for preparing PN ligand-modified Au clusters according to claim 6, characterized in that, The gold source is at least one of chloroauric acid, gold trichloride, gold oxide or a gold complex.

8. The method for preparing PN ligand-modified Au clusters according to claim 7, characterized in that, The molar ratio of the gold source to the PN ligand is 1:1-3.

9. The method for preparing PN ligand-modified Au clusters according to claim 6 or 7, characterized in that, The reducing agent is at least one of NaBH4, vitamin C or NaBH3CN.

10. The method for preparing PN ligand-modified Au clusters according to claim 9, characterized in that, The molar ratio of the reducing agent to the gold source is 4-6:

1.

11. Application of the Au cluster of any one of claims 3-5 or prepared by the preparation method of any one of claims 6-10 in a photothermal conversion material.

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