A monothiol molecule for quantum dot interface regulation and a synthesis method thereof

Abstract

The application discloses a novel monothiol molecule for quantum dot surface modification and interface regulation, which is obtained by hydrolysis of a corresponding thioester precursor. The thioester precursor is obtained through a coupling reaction of a bromine atom and a terminal alkyne bond, and finally the acetyl group is hydrolyzed into a thiol group under methanol and alkaline conditions to obtain the final product monothiol molecule. The application aims to design and synthesize a quantum dot surface ligand with a thiol group, the main structure of the surface ligand is a naphthalene ring, the thiol group is introduced under the condition that the molecular conjugate structure is unchanged, the degree of orbital overlap between the surface new ligand and the quantum dot is higher, efficient energy transfer from the quantum dot to the surface new ligand and higher surface ligand exchange kinetics are realized, an organic-inorganic composite system is successfully constructed, the construction of the composite system provides a new idea for the research of a novel quantum dot sensitizer, and the composite system has a wide application prospect in triplet-triplet annihilation upconversion.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology and relates to a naphthalene ring-based monothiol molecule and its preparation method. Background Technology

[0002] In the field of quantum dot surface energy transfer, the widely used surface-modified organic molecules are all monocarboxylic acid ligands, such as 9-anthracarboxylic acid, carboxylated tetraphenyl and its derivatives, and BODIPY derivatives. Compared with conventional carboxylic acid ligands, the conjugated system of thiol ligands can adhere more parallel to the quantum dot surface, enhancing the orbital coupling with the quantum dot and achieving more efficient Dexter energy transfer. Furthermore, the binding ability between metals and sulfur atoms on the quantum dot surface is stronger, and the exchange kinetics between thiol ligands and quantum dot surface ligands are faster. According to reported literature, Yinon Deree et al. compared anthracene ligands modified with different anchoring groups and found that modifying the quantum dot surface with ligands containing thiol groups significantly increased the fluorescence quenching rate of the quantum dots. Based on this, this invention designed and synthesized for the first time a novel naphthalene ring ligand containing thiol groups, achieving efficient energy transfer from the quantum dot to the novel thiol ligand while ensuring energy level matching with the quantum dot. Summary of the Invention

[0003] The present invention aims to provide a monothiol naphthalene ring aromatic compound and its preparation method, the chemical structural formula of which is shown in formulas (i) and (ii):

[0004]

[0005] This invention designs and synthesizes a novel small organic molecule ligand with a thiol group for quantum dot surface modification, and successfully anchors it onto the quantum dot surface, constructing a novel organic-inorganic composite system. The presence of the thiol group results in a higher degree of orbital overlap between the novel surface ligand and the quantum dot, achieving efficient energy transfer from the quantum dot to the novel surface ligand and more efficient surface ligand exchange kinetics. The construction of this composite system provides a new approach for the research of novel quantum dot sensitizers and has broad application prospects in triplet-triplet annihilation upconversion. Detailed Implementation

[0006] The technical solution adopted in this invention is carried out according to the following steps:

[0007]

[0008] The compound shown in formula (1), S-4-ethynylbenzyl thioacetate, PdCl2 (dppf), and CuI were placed in a cleaned Shrek tube. Water and oxygen in the apparatus were removed by three vacuum cycles and nitrogen purging. Then, dehydrated and deoxygenated triethylamine and tetrahydrofuran (2 mL / 10 mL) were added. The mixture was stirred at 70 °C for 10 hours. After the reaction was completed, the mixture was cooled to room temperature, and the solvent in the reaction mixture was removed under reduced pressure. The product was extracted with distilled water and dichloromethane. The organic phase was dried with sodium sulfate, and the organic solvent was removed by vacuum distillation. The crude product was purified by silica gel column chromatography (n-hexane / dichloromethane = 2 / 1, v / v) to obtain the compound shown in formula (2), which is the thioester precursor based on the naphthalene ring.

[0009] The compound shown in formula (2) and K2CO3 were placed in a cleaned Shrek tube. Water and oxygen in the apparatus were removed by three vacuum cycles and nitrogen purging. Then, deoxygenated methanol solvent was added and the mixture was stirred at room temperature for 1 hour. Dilute hydrochloric acid solution was slowly added dropwise to the reaction mixture until the pH of the solution was acidic. At this point, a white precipitate was formed in the solution. The crude product after filtration was purified by silica gel column chromatography (n-hexane / dichloromethane = 6 / 1, v / v) to obtain the compound shown in formula (3).

[0010] Accurately weigh the compound shown in formula (3), dissolve it in spectrally pure toluene reagent, and prepare a solution with a concentration of 1.0 × 10⁻⁻⁻⁶. 5 The photophysical properties of the compound were tested at room temperature using a mol / L solution. A UV-Vis spectrophotometer was used to scan the wavelength range of 350–800 nm, recording the maximum absorption wavelength. Then, using this maximum absorption wavelength as the excitation wavelength, a fluorescence spectrophotometer was used to scan the emission wavelength range of 380–700 nm, recording the fluorescence emission peak position and fluorescence intensity. The fluorescence quantum yield was determined by repeating the measurement three times for each sample and taking the average value. Transient absorption spectra were acquired using a femtosecond time-resolved transient absorption spectroscopy system with a pulsed laser as the excitation source (excitation wavelength corresponding to the aforementioned maximum absorption wavelength, pulse width not exceeding 150 fs, and adjustable single-pulse energy). Transient absorption spectra were recorded within the visible to near-infrared detection light range of 400–800 nm at different delay times from femtoseconds to microseconds, thus confirming the characteristic absorption peak of the triplet excited state of the compound.

[0011] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention. Attached Figure Description

[0012] The invention will be further described below with reference to the accompanying drawings.

[0013] Figure 1 This is the 1H NMR spectrum of a thioester precursor;

[0014] Figure 2 This is the mass spectrum of the thioester precursor;

[0015] Figure 3 It is the 1H NMR spectrum of a single thiol molecule;

[0016] Figure 4 This is the mass spectrum of a single thiol molecule;

[0017] Figure 5 These are the UV absorption and steady-state fluorescence spectra of a single thiol molecule;

[0018] Figure 6 It is the fluorescence decay kinetics and fluorescence quantum yield of monothiol molecules;

[0019] Figure 7 This is the femtosecond transient absorption spectrum of a single thiol molecule;

[0020] Figure 8 This is the nanosecond transient absorption spectrum of a single thiol molecule;

[0021] Figure 9 It is the ultraviolet absorption spectrum of the quantum dot and single-thiol molecule complex system.

Claims

1. A monothiol molecule based on a naphthalene ring, with chemical structural formulas shown in formulas (i) and (ii):

2. The structural formula of the monothiol molecule as described in claim 1, and its preparation method comprising the following synthetic steps: a. The compound shown in formula (1), S-4-ethynylbenzyl thioacetate, PdCl2 (dppf), and CuI were placed in a cleaned Shrek tube. Water and oxygen in the apparatus were removed by three vacuum cycles and nitrogen purging. Then, dehydrated and deoxygenated triethylamine and tetrahydrofuran (2 mL / 10 mL) were added. The mixture was stirred at 70 °C for 10 hours. After the reaction was completed, the mixture was cooled to room temperature, and the solvent in the reaction mixture was removed under reduced pressure. The product was extracted with distilled water and dichloromethane. The organic phase was dried with sodium sulfate, and the organic solvent was removed by vacuum distillation. The crude product was purified by silica gel column chromatography (n-hexane / dichloromethane = 2 / 1, v / v) to obtain the compound shown in formula (2), which is the thioester precursor based on the naphthalene ring. b. Take the compound shown in formula (2) and K2CO3 into a cleaned Shrek tube, remove water and oxygen from the apparatus by three vacuum cycles and nitrogen purging, then add deoxygenated methanol solvent, and stir at room temperature for 1 hour. Slowly add dilute hydrochloric acid solution to the reaction mixture and stir until the pH of the solution is acidic. At this point, a white precipitate will form in the solution. The crude product after filtration is purified by silica gel column chromatography (n-hexane / dichloromethane = 6 / 1, v / v) to obtain the compound shown in formula (3).

3. The naphthalene ring-based monothiol molecule and its preparation method according to claim 2, characterized in that... The organic solvent mentioned in step a is anhydrous and oxygen-free triethylamine and tetrahydrofuran, in a ratio of 1:

5.

4. The naphthalene ring-based monothiol molecule and its preparation method according to claim 2, characterized in that... The solvent mentioned in step b is deoxygenated methanol, and potassium carbonate is used as an alkaline reagent.

5. The naphthalene ring-based monothiol molecule and its preparation method according to claim 2, characterized in that... The reaction conditions described in step b are at room temperature; too high a temperature will produce side reactions.

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