An ultra-stable strong luminescent n-heterocyclic carbene-protected chiral heterometallic cluster and a preparation method thereof

Abstract

The application belongs to the cross field of coordination chemistry and nanomaterials, and discloses a super-stable strong luminescent N-heterocyclic carbene-protected chiral heterometallic cluster and a preparation method thereof. 58.5 H 59 AuBr4ClCu4F6N8OP (abbreviated as: R / S -NHC py -AuCu4 ‑ Br) belongs to an orthorhombic system, and the space group is a chiral space group P 212121. Another chemical formula of the nanocluster is C 58 H 58 AuCu4F6I4N8P (abbreviated as: R / S -NHC py -AuCu4 ‑ I) belongs to an orthorhombic system, and the space group is a chiral space group I 41. The cluster has a structure that can be stable to 150 DEG C in air. R / S -NHC py -AuCu4 ‑ Br has strong orange luminescence at room temperature in air, and the luminescence quantum yield is 58%. The chiral structure and strong luminescence make it have strong chiral luminescence characteristics, and it can have good application prospects in the fields of holographic projection, information storage and cell imaging.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of coordination chemistry and nanomaterials, and mainly relates to an ultra-stable, strongly luminescent N-heterocyclic carbene-protected chiral heterometallic cluster and its preparation method. Background Technology

[0002] Atomic-precise coin metal (gold, silver, copper) clusters are a class of clusters with precise atomic structures, formed by three or more coin metal atoms through metalophilic interactions, with an outer layer protected by organic ligands. Nanoclusters represent a state of matter between atoms, molecules, and bulk materials, serving as a bridge between atoms, molecules, and macroscopic matter. Their size is typically on the nanometer scale, and they often exhibit quantum confinement effects, leading to many novel phenomena and properties. Their excellent photophysical properties and potential applications in catalysis, bioimaging, and other fields have made them a research hotspot in materials science and inorganic chemistry in recent years.

[0003] Current research on coin metal nanoclusters mainly focuses on the synthesis and structure of novel nanoclusters. The excellent optical properties, superior lightfastness, and good biocompatibility of nanoclusters make them promising for a wide range of applications. However, the reported stability of coin metal nanoclusters at room temperature is relatively poor, and their luminescence quantum efficiency is also low. These shortcomings significantly hinder the application and development of nanoclusters. Therefore, designing and synthesizing atomically precise nanoclusters with high luminescence efficiency is one of the key research areas in the field of nanoclusters.

[0004] Chirality is a ubiquitous phenomenon in nature, and the chirality of nanoclusters can be endowed by chiral ligands. By selecting appropriate chiral ligands, chiral nanocluster structures can be synthesized. Chiral luminescence of chiral nanoclusters has significant potential applications in organic optoelectronics, information storage, biological cell imaging, and diagnostics. Summary of the Invention

[0005] The present invention aims to provide an ultra-stable, strongly luminescent N-heterocyclic carbene-protected chiral heterometallic cluster. Another objective is to provide a method for its preparation.

[0006] To achieve the objectives of this invention, an ultra-stable, strongly luminescent N-heterocyclic carbene-protected chiral heterometallic cluster was developed, with the chemical formula: C 58.5 H 59 AuBr4ClCu4F6N8OP (abbreviated as: R / S-NHC) py -AuCu4-Br), belongs to the orthorhombic crystal system, space group is chiral space group P212121, R-NHC py -AuCu4-Br: α=90°, β=90°, γ=90°, S-NHC py -AuCu4-Br): c=27.9235(18), α=90°, β=90°, γ=90°,

[0007] Another chiral heterometallic cluster has the following chemical formula: C 58 H 58 AuCu4F6I4N8P (abbreviated as: R / S-NHC) py -AuCu4-I), belongs to the orthorhombic crystal system, space group I41, R-NHC py -AuCu4-I: α=90°, β=90°, γ=90°; S-NHC py -AuCu4-I: α=90°, β=90°, γ=90°.

[0008] Among them, R / S-NHC py -PF6 is a chiral N-heterocyclic carbene ligand with the following structural formula:

[0009]

[0010] The method for preparing the chiral carbene ligand of the present invention is achieved through the following steps:

[0011] A methanol solution of (1R,2R)-(+)-1,2-diphenyl-1,2-ethylenediamine or (1S,2S)-(-)-1,2-diphenyl-1,2-ethylenediamine and glyoxylic acid monohydrate was stirred at room temperature. N-bromosuccinimide (NBS) was added to the mixture and stirred at room temperature. The reaction was then quenched with saturated sodium metabisulfite, and the solvent was removed under vacuum to obtain a solid. NaOH solution was then added, and the solid was extracted with ethyl acetate. The organic layer was dried with anhydrous magnesium sulfate, and the solvent was removed under vacuum to obtain a chiral imidazole. The synthesized chiral imidazole was dissolved in ethanol, and 2-(chloromethyl)pyridine hydrochloride and sodium bicarbonate were added and refluxed for two days. After filtration, the solvent was removed under vacuum, and the resulting solid was dissolved in dichloromethane. The solid was dried with anhydrous magnesium sulfate, and the solution was filtered. The solvent was removed under vacuum to obtain an oily substance, which was mixed with tetrahydrofuran to obtain a powder. Further washing with tetrahydrofuran and drying under vacuum yielded a white powder. In a flask, the above powder was dissolved in methanol, and an excess of ammonium hexafluorophosphate aqueous solution was added dropwise, immediately forming a precipitate. The precipitate was filtered, thoroughly washed with water / methanol, and dried under vacuum to obtain the above R / S-NHC. py -PF6 chiral carbene ligand ( Figure 1 (As shown).

[0012] The method for preparing gold-copper nanoclusters of the present invention is achieved through the following steps:

[0013] The chiral ligand, silver oxide, and tetrabutylammonium hexafluorophosphate were dispersed in a dichloromethane solution and reacted under light-protected conditions with stirring at room temperature. NaOH solution was then added, and the reaction was continued with stirring. After the reaction was complete, the mixture was filtered, and the clear filtrate was concentrated to a minimum volume under vacuum. Ether was added to obtain a large amount of white powder. The white powder was dissolved in dichloromethane, and a dichloromethane solution of thiophene gold was added. The mixture was placed in a light-protected environment and stirred, during which a precipitate formed. The solution was filtered to remove the precipitate, and the clear filtrate was concentrated to a minimum volume. A large amount of ether was added to obtain a white powder. The powder was dissolved in dichloromethane, and CuBr or CuI was added, with stirring continued to form a yellow solution. The mixture was filtered, and the clear filtrate was concentrated to a minimum volume. A yellow powder was precipitated with ether. The yellow powder was dissolved in dichloromethane and diffused in the gas phase with ether to obtain yellow crystals. The crystals were filtered, washed with ether, and dried at room temperature.

[0014] The chiral heterometallic nanoclusters described above are in the form of R-NHC py Taking -AuCu4-Br as an example, it consists of a metallic core composed of four copper atoms and one gold atom, surrounded by two organic ligands and four iodide ions. Figure 2 (As shown in Figure 3). Five metal atoms form two triangular frameworks sharing a single gold atom through metalophilic interactions; these triangles are almost orthogonal. Each central gold atom forms a strong coordination bond with a carbene carbon atom. Each copper atom is coordinated by two iodine atoms and one pyridine nitrogen atom.

[0015] The properties of the chiral heterometallic clusters with strong luminescence and high quantum yield of this invention are described in detail below:

[0016] The material possesses an ultra-stable crystal structure, maintaining its crystalline structure even at a high temperature of 150°C. Figure 4 (As shown). It exhibits strong orange emission at room temperature in air, with its optimal emission wavelength at 616 nm (excitation wavelength 450 nm). Figure 5 (As shown); the fluorescence quantum yield at room temperature is 58%, which is rare among N-heterocyclic carbene ligand-protected clusters. High quantum yield is a prerequisite for excellent luminescent materials, and high quantum yield cluster materials are a goal pursued by cluster researchers. Chiral ligands endow the entire cluster molecule with chiral properties (as shown). Figure 6 As shown), its chiral structure and strong luminescence give it strong chiral luminescence properties. Figure 7 As shown in the figure, it has great application prospects in fields such as holographic projection, information storage and cell imaging.

[0017] The beneficial effects of this invention are: the heterometallic cluster material of this invention has high stability, can maintain its crystalline structure at a high temperature of 150℃, and has ultra-high luminescence quantum yield and chiral luminescence characteristics, which has great potential for widespread application. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the molecular structure of the chiral carbene ligand of the present invention.

[0019] Figure 2 The present invention is R / S-NHC py A schematic diagram of a pair of enantiomeric structures of the -AuCu4-Br cluster material.

[0020] Figure 3 The present invention is R / S-NHC ql -A schematic diagram of a pair of enantiomeric structures of the AuCu4-I cluster material.

[0021] Figure 4 The present invention is R / S-NHC py Powder XRD curve of the -AuCu4-Br cluster material.

[0022] Figure 5 The present invention is R / S-NHC py Excitation and emission curves of the -AuCu4-Br cluster material.

[0023] Figure 6 The present invention is R / S-NHC py Circular dichroism chromatogram of the -AuCu4-Br cluster material.

[0024] Figure 7 The present invention is R / S-NHC py Circular polarization emission curve of the AuCu4-Br cluster material. Detailed Implementation

[0025] The invention will be further illustrated by the following examples:

[0026] Example 1: Synthesis of the chiral carbene ligand of the present invention

[0027] A methanol (100 mL) solution of (1R,2R)-(+)-1,2-diphenyl-1,2-ethylenediamine or (1S,2S)-(-)-1,2-diphenyl-1,2-ethylenediamine (3.00 g, 14.11 mmol) and glyoxylic acid monohydrate (1.50 g, 16.50 mmol) was stirred at room temperature for 4 hours. N-bromosuccinimide (NBS) (3.30 g, 18.00 mmol) was added to the mixture and stirred at room temperature. The reaction was quenched with saturated sodium metabisulfite, and the solvent was removed under vacuum to obtain a solid. The solid was then extracted with ethyl acetate after adding 5% NaOH solution. The organic layer was dried over anhydrous magnesium sulfate, and the solvent was removed under vacuum to obtain a chiral imidazole. The synthesized chiral imidazole (2.22 g, 10 mmol) was dissolved in ethanol (100 mL), and 2-(chloromethyl)pyridine hydrochloride (3.35 g, 20.40 mmol) and sodium bicarbonate (2.52 g, 31.12 mmol) were added and refluxed for two days. After filtration, the solvent was removed under vacuum, and the resulting solid was dissolved in dichloromethane, dried with anhydrous magnesium sulfate, and then the solution was filtered. The solvent was removed under vacuum to obtain an oily substance, which was mixed with 15 mL of tetrahydrofuran to obtain a powder. Further washing with tetrahydrofuran and drying under vacuum yielded a white powder. In a flask, the powder was dissolved in methanol, and the addition of excess aqueous solution of ammonium hexafluorophosphate immediately formed a precipitate. The precipitate was filtered, thoroughly washed with water / methanol, and dried under vacuum to obtain the above R / S-NHC. py -PF6 chiral carbene ligand.

[0028] Example 2: Synthesis of heterometallic clusters of the present invention

[0029] The chiral ligand (0.54 g, 1 mmol), silver oxide (66 mg, 0.28 mmol), and tetrabutylammonium hexafluorophosphate (40 mg) were dispersed in 40 mL of dichloromethane solution and stirred in the dark at room temperature for 10 minutes. Then, 1 M NaOH solution was added, and stirring continued for 4 hours. The mixture was filtered, and the clear filtrate was concentrated to 2 mL under vacuum. Ether was added to obtain a large amount of white powder. Next, the white powder (0.38 mg, 0.3 mmol) was dissolved in 30 mL of dichloromethane, and 10 mL of a dichloromethane solution of thiophene gold (0.096 g, 0.3 mmol) was added. The mixture was stirred in the dark for 30 minutes to form a precipitate. The solution was filtered to remove the precipitate, and the clear filtrate was concentrated to 2 mL. Ether was added to obtain a large amount of white powder. The above powder (0.05 mmol, 58 mg) was dissolved in 6 mL of dichloromethane. CuBr (0.2 mmol, 32 mg) or CuI (0.2 mmol, 38 mg) was added, and the mixture was stirred for 3 hours to form a yellow solution. The mixture was filtered, and the clear filtrate was concentrated to 2 mL. The yellow powder was precipitated with diethyl ether. The yellow powder was dissolved in 1 mL of dichloromethane, and the solution was diffused with diethyl ether in the gas phase to obtain yellow crystals. The crystals were filtered, washed with diethyl ether, and dried at room temperature for use in property testing.

[0030] The heterometallic cluster material of the present invention prepared in Example 2 was further characterized as follows:

[0031] (1) Crystal structure determination

[0032] X-ray single-crystal diffraction data of the complexes were determined using appropriately sized single-crystal samples on a Rigaku XtaLAB Pro single-crystal diffractometer. All data were obtained using graphite-monochromated CuKα rays. The diffraction source was collected at 200 K using ω-scan mode, and corrected for Lp factor and semi-empirical absorption. Structural analysis was performed by first obtaining the initial structure using the direct method with the SHELXL-97 program, and then refining it using the full-matrix least squares method with the SHELXL-97 program. All non-hydrogen atoms were refined using anisotropic thermal parameter methods. All hydrogen atoms were refined using isotropic thermal parameter methods. Detailed crystallographic data are shown in Table 1; important bond length data are shown in Table 2.

[0033] Table 1. Main crystallographic data of the heterometallic cluster material of the present invention.

[0034] Table 1. Main crystallographic data

[0035]

[0036] R1=∑||F o |-|F c || / ∑|F o|.wR2=[∑w(F o 2 -F c 2 ) 2 / ∑w(F o 2 ) 2 ] 1 / 2

[0037] Table 2 Main crystallographic data

[0038]

[0039] R1=∑||F o |-|F c || / ∑|F o |.wR2=[∑w(F o 2 -F c 2 ) 2 / ∑w(F o 2 ) 2 ] 1 / 2

[0040] Table 3 R-NHC py -AuCu4-Br important bond length

[0041]

[0042] Table 4 R-NHC py -AuCu4-I important bond length

[0043]

[0044] The above embodiments are only used to illustrate the content of this invention. Other embodiments of this invention are also possible. However, all technical solutions formed by equivalent substitution or equivalent modification fall within the protection scope of this invention.

Claims

1. A chiral heterometallic cluster protected by N-heterocyclic carbene, characterized in that: Its chemical formula is: C 58.5 H 59 AuBr4ClCu4F6N8OP, abbreviated as: R / S -NHC py -AuCu4 - Br belongs to the orthorhombic crystal system and has a chiral space group. P 212121, R -NHC py -AuCu4 - Br: a = 15.2743(7) Å, b = 15.7324(8) Å, c = 27.9349(14)Å, α=90 °, β=90 ° γ=90 °, V = 6712.8(6) Å 3 ; S -NHC py -AuCu4 - Br: a = 15.2964(9)Å, b =15.7426(10) Å, c =27.9235(18) Å, α = 90°, β = 90° γ = 90°, V = 6724.1(7)Å 3 ; The chemical formula of another chiral heterometallic cluster is: C 58 H 58 AuCu4F6I4N8P, abbreviated as: R / S -NHC py -AuCu4 - I belongs to the orthorhombic crystal system and its space group is chiral space group. I 41, R -NHC py -AuCu4 - I: a = 17.6372(5) Å, b =17.6372(5) Å, c = 22.5259(7) Å, V = 7007.2(5) Å 3 , α = 90°, β = 90° γ = 90°; S -NHC py -AuCu4-I: a = 17.6980(10)Å, b = 17.6980(10)Å, c = 22.5113(15) Å, V =7051.0(9) Å 3 , α = 90°, β = 90° γ = 90°; in R / S -NHC py - For chiral N-heterocyclic carbene ligands R / S -NHC py -PF6 loses the group formed by PF6. R / S -NHC py The simplified molecular structure of PF6 is as follows: 。 2. The chiral heterometallic cluster protected by N-heterocyclic carbene as described in claim 1, characterized in that: It consists of a metal core composed of four copper atoms and one gold atom, surrounded by two organic ligands and four halide ions; the five metal atoms form two triangular frames sharing a single gold atom through metalophilic interactions, and these two triangles are orthogonal; each central gold atom forms a strong coordination bond with a carbon atom of a carbene ligand; each copper atom is coordinated by two halogen atoms and one pyridine nitrogen atom; the halogen is bromine or iodine.

3. The method for preparing N-heterocyclic carbene-protected chiral heterometallic clusters as described in claim 1 or 2, characterized in that: This can be achieved through the following steps: (1) Chiral N-heterocyclic carbene ligand, silver oxide and tetrabutylammonium hexafluorophosphate were dispersed in dichloromethane solution in the dark and stirred at room temperature; then NaOH solution was added and the reaction was continued by stirring. After the reaction was completed, the mixture was filtered, the filtrate was concentrated under vacuum, and ether was added to obtain powder. (2) Dissolve the powder in dichloromethane, add a dichloromethane solution of tetrahydrothiophene gold chloride, place the mixture in a dark environment and stir to react, form a precipitate, remove the precipitate by filtration, concentrate the filtrate, add diethyl ether to obtain the powder; (3) Dissolve the above powder in dichloromethane, add CuBr or CuI and continue stirring to react, filter the mixture, concentrate the filtrate, and precipitate the powder with diethyl ether; dissolve the powder in dichloromethane and diffuse it in the gas phase with diethyl ether to obtain the target crystal; The molecular structure of the chiral N-heterocyclic carbene ligand is as follows: 。

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