PN ligand capable of being cis-trans isomerized and Au cluster modified by PN ligand

Abstract

The invention provides a PN ligand capable of being subjected to cis-trans isomerization and a PN ligand modified Au cluster, and the PN ligand modified Au cluster with high photothermal conversion efficiency is prepared from the PN ligand capable of being subjected to cis-trans isomerization under illumination.

Description

Technical Field

[0001] The invention belongs to the technical field of metal cluster materials, and in particular relates to a PN ligand capable of cis-trans isomerization and a PN ligand-modified Au cluster. Background Art

[0002] The photothermal conversion materials currently under study, such as gold (Au), silver (Ag), copper (Cu), etc., have two most basic characteristics: one is that they need to have obvious absorption of light in a certain wavelength band, and the other is to effectively convert the absorbed light energy into heat energy. For example, the precious metals Au and Ag have obvious absorption in the visible light region and near-infrared light region due to their own localized surface plasmon resonance (SPR) effect; and the wavelength band of their absorption light can be accurately controlled by changing their morphology.

[0003] However, current photothermal conversion materials still have defects in terms of photothermal conversion efficiency. Gold clusters have attracted more and more attention from scientists due to their clear and unique molecular structure and applications in luminescence, catalysis and other fields. Therefore, it is very important to find a method for preparing Au clusters with high photothermal conversion efficiency. Summary of the invention

[0004] Based on the above technical problems, the present invention provides a PN ligand capable of cis- and trans-isomerization and a PN ligand-modified Au cluster. A PN ligand-modified Au cluster with high photothermal conversion efficiency is prepared by using a PN ligand capable of cis- and trans-isomerization under light.

[0005] The present invention proposes a PN ligand capable of cis-trans isomerization, and the trans structural formula of the PN ligand is as follows:

[0006]

[0007] The cis structural formula of the PN ligand is shown below:

[0008]

[0009] Among them, R 1 , R 2 Each is independently at least one of hydrogen, halogen, alkyl, haloalkyl, amino, cyano, nitro, hydroxyl, mercapto, alkoxy, alkenyl, alkynyl, cycloalkyl, aryl or heteroaryl.

[0010] Preferably, the structural 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 follows:

[0013]

[0014] The present invention also provides a PN ligand-modified Au cluster, the molecular formula of which is Au 21 (PN) 8 X 2 ;

[0015] The structural formula of the PN ligand is shown below:

[0016]

[0017] R 1 , R 2 Each is 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 anionic group.

[0019] Preferably, the structural formula of the PN ligand is as shown in Formula I below:

[0020]

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

[0022] Preferably, the present invention also provides a method for preparing the above-mentioned PN ligand-modified Au clusters, comprising: adding a gold source and a PN ligand into a solvent and dissolving them completely, and then adding a reducing agent for reduction to obtain the Au clusters.

[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 to the PN ligand is 1:1-3.

[0025] Preferably, the reducing agent is NaBH 4 , Vitamin C or NaBH 3 At least one of CN;

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

[0027] The present invention also proposes an application of the Au cluster or the Au cluster prepared by the above preparation method in a photothermal conversion material.

[0028] Beneficial effects:

[0029] (1) The present invention provides a PN ligand capable of cis-trans isomerization and a PN ligand-modified Au cluster, wherein the Au cluster has a high photothermal conversion efficiency in the near-infrared region, thereby expanding the application of photothermal conversion materials;

[0030] (2) The present invention provides a method for preparing Au clusters modified with PN ligands, wherein the preparation method has mild reaction conditions and is simple and easy to perform;

[0031] (3) The present invention provides an application of a PN ligand-modified Au cluster, which can be used as a photothermal conversion material in the field of photothermal conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a hydrogen spectrum of the trans-PN ligand capable of cis-trans isomerization described in the embodiment of the present invention;

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

[0034] Figure 3 The phosphorus spectrum of the trans-PN ligand capable of cis-trans isomerization described in the embodiment of the present invention;

[0035] Figure 4 It is a hydrogen spectrum of the cis-PN ligand capable of cis- and trans-isomerization according to the embodiment of the present invention;

[0036] Figure 5 The carbon spectrum of the cis-PN ligand capable of cis- and trans-isomerization described in the embodiment of the present invention;

[0037] Figure 6 The phosphorus spectrum of the cis-PN ligand capable of cis- and trans-isomerization described in the embodiment of the present invention;

[0038] Figure 7 The Au described in the embodiment of the present invention 21 Mass spectra of clusters;

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

[0040] Fig. 9 The Au described in the embodiment of the present invention 21 UV-visible absorption spectrum of the cluster;

[0041] Fig.10 The Au described in the embodiment of the present invention 21 TLC chromatogram of clusters;

[0042] Fig.11 The Au described in the embodiment of the present invention 21 Cluster light transition diagram: a is Au described in the example 21 TLC chromatograms of clusters after illumination under different conditions, b is the Au 21 UV-visible absorption spectra of clusters after illumination under different conditions;

[0043] Fig.12 The Au described in the embodiment of the present invention 21 The results of the infrared thermal imager monitoring the temperature and illumination time of the clusters in real time after illumination under different conditions: a and b correspond to the illumination conditions of concentration 1 mg / mL, wavelength 785 nm, and power 0.6 W, and c and d correspond to the illumination conditions of concentration 0.5 mg / mL, wavelength 785 nm, and power 1 W;

[0044] Fig.13 The Au described in the embodiment of the present invention 21 Cluster at wavelength 785nm, laser intensity 0.6W / cm 2 , photothermal conversion curve under the condition of concentration 1.0 mg / mL: a is the Au 21 The photothermal conversion and cooling curves of the cluster, b is the linear curve of the corresponding time and lnθ;

[0045] Fig.14 The Au described in the embodiment of the present invention 21 Cluster at wavelength 785nm, laser intensity 1.0W / cm 2 , photothermal conversion curve under the condition of concentration 0.5 mg / mL: a is the Au 21 The photothermal conversion and cooling curves of the cluster, b is the linear curve of the corresponding time and lnθ;

[0046] Fig.15 The Au described in the embodiment of the present invention 21 Temperature variation of the cluster after five cycles of illumination at 785 nm wavelength;

[0047] Fig.16 The Au described in the embodiment of the present invention 21 UV-visible absorption spectra of the clusters after illumination under different conditions. DETAILED DESCRIPTION

[0048] Hereinafter, the present invention will describe the technical solution in detail through specific embodiments, but it should be clearly stated that these embodiments are for illustration only and are not to be construed as limiting the scope of the present invention.

[0049] Example

[0050] This embodiment provides a trans-PN ligand capable of cis-trans isomerization, and its structural formula is shown in the following formula I:

[0051]

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

[0053]

[0054] (1) 2-Methylquinoline (12 mmol) was dissolved in 50 mL of anhydrous and oxygen-free tetrahydrofuran (THF), and the mixture was placed at -78°C under nitrogen protection. 6 mL of 2.0 M lithium diisopropylamide (LDA) solution was slowly added dropwise thereto. After stirring for 1 h at -78°C, the solution gradually turned into a red viscous liquid. 2-Diphenylphosphobenzaldehyde (10 mmol) powder was dissolved in anhydrous and oxygen-free tetrahydrofuran solution, and then added dropwise to the red viscous liquid, and the mixture was gradually restored to room temperature and stirred for 12 h. After the reaction was completed, water was added and the mixture was extracted with ethyl acetate, dried with anhydrous sodium sulfate, and concentrated under vacuum. The mixture was purified by silica gel column chromatography to obtain an intermediate with a yield of 92%.

[0055]

[0056] (2) The intermediate was dissolved in 100 mL of toluene (Tol), and p-toluenesulfonic acid (0.1 eq.) was added to the obtained toluene solution. Under nitrogen protection, the oil bath was heated to 110° C., and the reaction was refluxed under condensation for 12 h. After the reaction was completed, the mixture was cooled to room temperature and concentrated under vacuum. The mixture was purified by silica gel column chromatography to obtain the final product, which was the trans-PN ligand, with a yield of 71%;

[0057] This embodiment also proposes a cis-PN ligand capable of cis-trans isomerization, and its structural formula is shown in the following formula II:

[0058]

[0059] The preparation method of the above-mentioned cis-PN ligand capable of cis-trans isomerization comprises:

[0060]

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

[0062] The trans-PN ligand and cis-PN ligand prepared in the embodiment were tested by hydrogen spectrum, carbon spectrum and phosphorus spectrum. The results are as follows: Figure 1-6 As shown, refer to Figure 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] Among them, the specific NMR data of the trans-PN ligand are as follows:

[0064] Hydrogen spectrum: 1H NMR (400MHz, CD 2 Cl 2 )δ6.96(dd,1H),7.24(t,2H),7.34(d,11H),7.42(t,1H),7.48(t,1H),7.54(d,1H) ,7.68(t,1H),7.77(d,1H),7.86(dd,1H),8.00(d,1H),8.09(d,1H),8.38(dd,1H).

[0065] Carbon spectrum: 13 C NMR (101 MHz, CD 2 Cl 2 )δ119.41,126.42,126.46,126.61,127.76,127.89,128.94,128.99,129.06,129.28,129.51,129.66 ,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 PNMR (162MHz, CD 2 Cl 2 )δ-13.79.

[0067] The specific NMR data of cis-PN ligand are as follows:

[0068] Hydrogen spectrum: 1 H NMR (400MHz, CD 2 Cl 2 )δ6.80(t,2H),7.01(dd,1H),7.11–7.25(m,3H),7.33(q,11H),7.48(t,1H),7.66(t,1H),7.73(dd,2H),7.95(d,1H).

[0069] Carbon spectrum: 13 C NMR (101 MHz, CD 2 Cl 2)δ121.78,126.44,127.00,127.51,128.11,128.65,128.72,128.98,129.13,129.46,130.17,130.22 ,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 PNMR (162MHz, CD 2 Cl 2 )δ-13.19.

[0071] This embodiment also proposes a PN ligand-modified Au cluster, whose molecular formula is [Au 21 (PN) 8 Cl 2 ] + , with Au 21 Cluster as a short name;

[0072] Wherein, the structural formula of PN ligand is shown in the following formula I:

[0073]

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

[0075] (1) Prepare PN ligand according to the above method;

[0076] (2) HAuCl 4 ·4H 2 O (0.25 mmol) and PN ligand (200 mg, 0.5 mmol) were added to 20 mL of ethanol at the same time. After stirring for 10 min, the solution changed from light yellow turbidity to clear, and then gradually turned into a yellow suspension. NaBH 4 (1.25mmol) was dissolved in 4mL of ultrapure water and then quickly added to the above yellow suspension. The solution quickly turned black. After stirring for 4h, the reaction solution was concentrated by rotary evaporation to about 5mL. After adding petroleum ether and ethyl acetate (10:1) to wash twice, 15mL of dichloromethane was used for extraction. After rotary evaporation and concentration, the Au cluster modified with the PN ligand was obtained by thin layer chromatography, referred to as Au 21 Clusters.

[0077] The Au prepared in the above embodiment 21 Mass spectrometry and crystal diffraction were performed, and the results were as follows Figure 7 , 8 As shown, refer to Figure 7 , 8 It can be seen that the structural formula and spatial structure of the Au cluster modified by the PN ligand, Au 21 The crystallographic data of the cluster are shown in Table 1 below:

[0078] Table 1

[0079]

[0080]

[0081] The Au prepared in the above embodiment 21 The clusters were dissolved in dichloromethane and their UV-visible spectra were measured. Fig. 9 As shown, refer to Fig. 9 It can be seen that Au 21 The clusters have main absorption peaks at 413nm, 457nm, and 593nm.

[0082] Au 21 The crude product of the cluster was dissolved in dichloromethane and evenly coated on a thin layer chromatography plate. A TLC chromatogram was obtained at a developing solvent ratio of dichloromethane (DCM): methanol (MeOH) = 20:1. The results are as follows: Fig.10 As shown, refer to Fig.10 It can be seen that Au 21 After the clusters are separated from the mixture, the largest reddish-brown part of the separation band indicates that Au 21 Clusters have a high content ratio.

[0083] Au 21 The crude product of the cluster was dissolved in ethanol (EtOH) and illuminated for one day under the conditions of 400nm-24W (Purple), 450nm-24W (Blue 24w), and 450nm-40W (Blue 40w). The three product bands corresponding to 1, 2, and 3 were separated by TLC method. The results are shown in FIG. Fig.11 As shown, refer to Fig.11 It can be seen that under different lighting conditions, Au 21 The clusters can undergo transformation, where the UV peaks of the two product bands corresponding to 1 and 2 are different from the original Au 21 The clusters are different, indicating that new clusters have been generated, and the UV peak of the product band corresponding to 3 is the same as the original Au 21 Like the cluster, this is the part that has not undergone the transformation.

[0084] Au 21The clusters were dissolved in 1 mL of toluene to a concentration of 0.5 mg / mL and 1 mg / mL. Laser irradiation was performed at a wavelength of 785 nm and a power of 0.6 W or 1.0 W. The temperature was measured by an infrared camera and photographed every 30 seconds to record the temperature change process. After 10 minutes of irradiation, the irradiation was stopped and photographing was continued until the 18th minute. The results are shown in the figure. Fig.12 As shown, refer to Fig.12 It can be seen that there is a picture taken every 30 seconds, the first 21 pictures are pictures of heating under illumination, and the last 15 pictures are pictures of cooling after stopping illumination. The photothermal efficiency is obtained through temperature changes, calculation according to the formula and data fitting.

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

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

[0087]

[0088] Where m i and c pi is the mass and heat capacity of the system, Qs is the photothermal energy input when the laser irradiates the sample, and Q loss It is the loss of heat energy to the surrounding environment;

[0089] When the temperature reaches its maximum value, 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 maximum temperature change;

[0092] The photothermal conversion efficiency η is calculated as follows:

[0093]

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

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

[0096]

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

[0098] Sample system time constant τ s

[0099]

[0100]

[0101] When the laser is turned off,

[0102] Q S =0

[0103]

[0104] t=-τ s lnθ

[0105] The thermal stability (hS) of the sample can be calculated based on the slope of the cooling time and lnθ.

[0106] The Au prepared in the above embodiment 21 The photoelectric conversion efficiency of the clusters 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] Referring to Table 2, it can be seen that as the laser wavelength increases, the maximum light-to-heat conversion efficiency can be obtained at a wavelength of 785 nm, which can basically reach about 75%.

[0112] in, Fig.13 (a) is Au described in the embodiment 21 Cluster at wavelength 785nm, laser intensity 0.6W / cm 2 , Photothermal conversion and cooling curves under the condition of concentration 1.0mg / mL, Fig.13 (b) is the linear curve of the corresponding time and lnθ; Fig.14 (a) is Au described in the embodiment 21 Cluster at wavelength 785nm, laser intensity 1.0W / cm 2 , Photothermal conversion and cooling curves under the condition of concentration 0.5mg / mL, Fig.14 (b) is the linear curve of the corresponding time and lnθ.

[0113] The Au prepared in the above embodiment 21The cluster was irradiated with laser at a wavelength of 785 nm, a power of 1.0 W, and a concentration of 1.0 mg / mL. A heating and cooling cycle was performed by first irradiating with laser for 10 min and then cooling for 10 min. After 5 heating and cooling cycles, the temperature change diagram was recorded. The results are shown in the figure. Fig.15 As shown, refer to Fig.15 It can be seen that even after 5 heating and cooling cycles, Au 21 The clusters can still achieve excellent and stable photothermal performance; at the same time, because the temperature rise of 1.0w-1.0mg / mL is the highest under the condition of 785nm, Au 21 The cluster can still circulate stably under this condition, indicating that it can also circulate stably under other conditions.

[0114] The Au prepared in the above embodiment 21 After the clusters were irradiated with lasers at different powers and concentrations, their UV-visible spectra were measured. Fig.16 As shown, refer to Fig.16 It can be seen that after the photothermal efficiency test, Au 21 The UV-visible absorption spectra of the clusters are basically consistent, further indicating that Au 21 The clusters have good photothermal stability.

[0115] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A PN ligand capable of cis-trans isomerization, characterized in that: The trans structural formula of the PN ligand is shown below: The cis structural formula of the PN ligand is shown below: Wherein, 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.

2. The PN ligand capable of cis- and trans-isomerization according to claim 1, characterized in that: The structural formula of the PN ligand is shown in the following formula I and II:

3. The PN ligand capable of cis- and trans-isomerization according to claim 1 or 2, characterized in that: The synthetic route of the PN ligand is as follows:

4. A PN ligand-modified Au cluster, characterized in that: The molecular formula of the Au cluster is Au 21 (PN)8X2; The structural formula of the PN ligand is shown below: 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; X is an anionic group.

5. The PN ligand-modified Au cluster according to claim 4, characterized in that: The structural formula of PN ligand is shown in Formula I below:

6. The PN ligand-modified Au cluster according to claim 4 or 5, characterized in that: X is halogen, preferably Cl.

7. A method for preparing the PN ligand-modified Au clusters according to any one of claims 4 to 6, characterized in that: include: The gold source and the PN ligand are added into a solvent and completely dissolved, and then a reducing agent is added for reduction to obtain the Au cluster.

8. The method for preparing the PN ligand-modified Au clusters according to claim 7, characterized in that: The gold source is at least one of chloroauric acid, gold trichloride, gold oxide or a gold complex; Preferably, the molar ratio of the gold source to the PN ligand is 1:1-3.

9. The method for preparing the PN ligand-modified Au clusters according to claim 7 or 8, characterized in that: The reducing agent is at least one of NaBH4, vitamin C or NaBH3CN; Preferably, the molar ratio of the reducing agent to the gold source is 4-6:

1.

10. Use of the Au cluster according to any one of claims 4 to 6 or the Au cluster prepared by the preparation method according to any one of claims 7 to 9 in a photothermal conversion material.

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