Stable phenoxy radical monomolecular junctions with controlled spin distribution and methods of making the same

Abstract

This invention provides a stable phenoxy radical monomolecular junction with modulated spin distribution and its preparation method. By combining single-molecule devices with density functional theory calculations, the spin distribution of unpaired monomolecules is studied. The stable phenoxy radical monomolecular junction of this invention can characterize the spin distribution changes of organic radical molecules in the form of molecular conductivity, and it is simple to synthesize and has high stability at room temperature. The organic radical monomolecular junction of this invention exhibits significant conductivity changes in single-molecule tests, with the conductivity values ​​showing a regular variation consistent with its spin density distribution.

Description

Technical Field

[0001] This invention relates to the field of organic radical single-molecule devices, and particularly to a stable phenoxy radical single-molecule junction with controlled spin distribution and its preparation method. Background Technology

[0002] like Figure 1 As shown, free radical molecules are molecules containing one or more unpaired electrons. Because their unpaired electrons are in the outermost orbitals, they are prone to gaining or losing electrons, making them highly chemically reactive and easily undergoing reactions such as oxidation, dimerization, or long-chain polymerization. This results in free radicals generally having very short half-lives.

[0003] In free radical molecules, unpaired electrons, having lost the bond of chemical bonds, are often not confined to a single atom but exist throughout the molecule as a probability cloud; this phenomenon is called electron delocalization. Studying electron delocalization in free radical molecules helps to gain a deeper understanding of important properties such as energy levels, spectra, and stability, and also aids in the study of electron transfer, reaction mechanisms, and other related processes.

[0004] The electron delocalization problem is also known as the spin density distribution problem. Spin is the angular momentum carried by an elementary particle. Electrons can be divided into two types according to their spin direction: α electrons have a spin number of 1 / 2, and β electrons have a spin number of -1 / 2. Spin density is defined as the density difference between the two types of electrons, i.e., the density of α electrons minus the density of β electrons. For non-radical molecules, since electrons exist in pairs, the density of α and β electrons is equal everywhere, so the spin density of the molecule is zero everywhere. However, in radical molecules, the presence of unpaired electrons causes the spin density distribution of α and β electrons to no longer be equal everywhere. We usually use density functional theory to study the changes in spin distribution in radical molecules. Figure 2 This is a spin density distribution diagram of the conjugated bis(phenoxy)azobenzene diradical. Light blue represents an α-electron spin density higher than a β-electron spin density, while green represents an α-electron spin density lower than a β-electron spin density. The denser the colored areas in the diagram, the greater the probability of unpaired electrons delocalizing to that region. Regions with no spin density distribution indicate that unpaired electrons cannot delocalize to that region. Generally speaking, the more uniform the spin density distribution across the entire molecular backbone, the better the stability of the radical; conversely, the more concentrated the spin density distribution, the less stable the radical molecule. This is because the more concentrated the delocalization of unpaired electrons, the easier it is for them to be captured and undergo chemical reactions.

[0005] Single-molecule devices are important tools for studying molecular electronics. Molecular electronics studies electronics at the molecular scale. Its research goal is to build functional molecular-level electronic devices and even further form molecular-level computers by using molecules or molecular clusters as the core components of electronic devices. Figure 3 This is a schematic diagram of a single-molecule device. The pyramid formed by the yellow spheres is the gold electrode. The molecules with anchoring groups are connected between the gold electrodes. By applying a voltage to the Au electrode and recording the current flowing through the molecules, the conductivity of the molecules can be analyzed.

[0006] In this invention, we focus on the conductivity process of free radical materials. Two key issues arise in this process: first, how to construct a simple, easily prepared, and stably stored monomolecular junction at room temperature (with a half-life longer than the test period); second, what role do unpaired electrons play; and third, can the electrical transport properties of the material be modulated through unpaired electrons? Based on these three issues, existing solutions are mainly based on the following technologies.

[0007] Density functional theory (DFT) is used to simulate the distribution of unpaired electrons in molecules. In quantum mechanics, the quantum states of multiple particles in isolated systems are described by wave functions. However, finding a wave function that reflects all information in a multi-particle system is extremely difficult, not only due to the high computational requirements and costs, but also because only a portion of the system has analytical solutions. To address this problem, researchers have attempted to construct simplified models that facilitate both conceptual and computational processing of complex problems while maintaining a certain level of accuracy. DFT developed in this direction, essentially replacing the wave function with electron density as the fundamental quantity for studying all information in the ground state of molecules or atoms. This simplifies variables and transforms a 3N-dimensional multi-electron system into a 3-dimensional single-electron problem. The most fundamental function of DFT is to calculate the electron density distribution and total ground state energy of a system, with the Hohenberg-Kohn theorem (HK theorem) and the Kohn-Sham equations forming its basis. The HK theorem includes: HK theorem 1, which states that each electron density state has a unique corresponding ground-state external potential term and ground-state total energy; and HK theorem 2, which states that with a constant number of electrons, the ground-state energy of any multi-particle system is the global minimum of the system's total energy with respect to the charge density functional, which corresponds to the ground-state electron density. Kohn and Sham proposed an assumption: any interacting N-dimensional system can be accurately simulated by a non-interacting N-dimensional system. Therefore, a series of equations proposed by Kohn and Sham are used to solve for the electron energy and density distribution in non-interacting multi-particle systems. The results can be used to simulate the electron energy and density distribution in the corresponding interacting multi-particle system. With further research, more theories have been developed, such as the generalized gradient approximation, exchange-correlation functionals, and hybrid functionals, which have supplemented and optimized the accuracy and applicability of the DFT.

[0008] Regarding the construction of single-molecule junctions, several similar technical solutions exist, such as mechanically controlled break junction (MCBJ) and conductive-atomic force microscopy break junction (AFM-BJ). The MCBJ device mainly consists of three parts: a pusher for forming nano-intervals, an elastic matrix, and two side supports. Its working principle is as follows: under a certain bias voltage, an external force is applied to the pusher, causing the matrix to bend. The metal wire on the matrix also elongates until it breaks at a certain length, forming two electrodes. Conversely, when the matrix is ​​no longer subjected to external force, the contraction of the metal wire causes the two electrodes to rejoin, forming a single metal wire. The entire device is driven by piezoelectric control or a stepper motor. Similar to STM-BJ, AFM-BJ uses metal probes and a gold substrate as electrodes, but unlike STM-BJ, AFM-BJ introduces the variable of force. Its working principle is as follows: under a certain bias voltage and laser irradiation, a certain external force is applied to the cantilever to change the molecular connection. Under the reflection effect, the molecular connection is reflected by the difference in the detector signal.

[0009] The STMBJ used in this invention can rapidly create thousands of molecular junctions by repeatedly moving the needle tip to contact and separate it from the substrate electrode on which sample molecules are adsorbed. When the needle tip is close enough to the substrate, molecules have a chance to connect the needle tip electrode and the substrate electrode. Then, the needle tip is pulled upward to break the metal-molecule-metal connection. By precisely controlling the movement of the needle tip, i.e., changing the distance between the needle tip and the substrate, the number of bridging molecules can be changed.

[0010] Currently, research on free radical molecules in the field of organic electronics mainly focuses on macroscopic areas such as free radical polymers. At the molecular level, research on the mechanisms related to electron spin distribution, molecular frontier orbitals, internal energy level changes, and structural changes resulting from the unpaired electrons in free radical molecules is still in its early stages. Predictions are typically only possible using density functional theory calculations. Therefore, we combine single-molecule technology with organic free radical materials to construct a phenoxy free radical single-molecule junction that is stable at room temperature. This scheme effectively solves the problem of poor stability in single-molecule testing of organic free radicals and allows for better control of molecular conductivity. Furthermore, by combining density functional theory, the single-molecule junction in this scheme can characterize the properties of organic free radical molecules in terms of molecular conductivity, allowing for the study of changes in the spin distribution of free radical molecules. The materials involved in this invention are simple to prepare, the raw materials are inexpensive and readily available, and the characterization methods used are common and easy to operate. Summary of the Invention

[0011] To address the problems in the prior art, this application proposes a stable phenoxy radical monomolecular junction for controlling spin distribution. The monomolecular junction can characterize the changes in the spin distribution of organic radical molecules in the form of molecular conductivity.

[0012] The specific steps for preparing compound R1 are as follows: Under a protective gas environment, 4-bromo-2,6-di-tert-butylphenol and bis-pinacol boronic acid ester were placed in container A, and a magnetic stir bar was placed in the container. Subsequently, the air in container A was replaced with a protective gas. Potassium acetate and bis(triphenylphosphine)palladium chloride were added to container A, and 1,4-dioxane solvent was injected to form mixture X1. Then, the mixture X1 was heated in an oil bath to allow it to react in container A. After the reaction was completed, the mixture X1 was filtered to obtain a solution. The solvent was then removed by vacuum evaporation. Hexane and dichloromethane were used as a mixed solvent and used as the eluent for purification on a silica gel column. The purified product was a white powdery solid compound R1.

[0013] The specific steps for preparing compound R2 are as follows: 1,3,5-tribromobenzene and 4-methylthiophenylboronic acid are placed in container B, and a magnetic stir bar is placed in the container. Then, the air in the double-necked flask is replaced with a protective gas. Tetra(triphenylphosphine)palladium and potassium carbonate are added to container B, and a mixed solvent of water, ethanol, and toluene is injected to form mixture Y1. Then, the mixture Y1 is heated in an oil bath to react in container B. After the reaction is complete, the mixture Y1 is filtered to obtain a solution. The solvent is then removed by vacuum evaporation. Hexane and dichloromethane are mixed to form a solvent, which is used as an eluent for purification on a silica gel column. The purified product is a white powdery solid compound R2.

[0014] The specific process for preparing compounds m1 and m1o is as follows: Under a protective gas environment, compounds R1 and R2 are placed in container C, and a magnetic stir bar is placed in the container. Subsequently, the air in container C is replaced with a protective gas. Tetra(triphenylphosphine)palladium and potassium hydroxide are added to container C, and tetrahydrofuran solvent is injected to form mixture Z1. Then, the mixture Z1 is heated in an oil bath to react in container C. After the reaction is complete, the mixture Z1 is filtered to obtain a solution. The solvent is then removed by vacuum evaporation. Hexane and dichloromethane are mixed to form a solvent, which is used as an eluent for purification on a silica gel column. The purified product is a white powdery solid organic molecule compound m1. Lead dioxide is mixed with the reacted compound m1 and stirred in dichloromethane solvent for ten minutes to obtain compound m1o.

[0015] The specific process for preparing compound R3 is as follows: Under a protective gas environment, compound R1 and 1-bromo-4-iodobenzene are placed in container D, and a magnetic stir bar is placed in the container. Subsequently, the air in container D is replaced with a protective gas. Tetra(triphenylphosphine)palladium and potassium hydroxide are added to container D, and tetrahydrofuran solvent is injected to form mixture X2. Then, the mixture X2 is heated in an oil bath to react in container D. After the reaction is complete, the mixture X2 is filtered to obtain a solution. The solvent is then removed by vacuum evaporation, and n-hexane is used as the eluent for purification on a silica gel column. The purified product is a white powdery solid compound R3.

[0016] The specific process for preparing compound R4 is as follows: Under a protective gas environment, compound R2 and bis-pinacol boronic acid ester were placed in container E, and a magnetic stir bar was placed in place. Subsequently, the air in container E was replaced with a protective gas. Potassium acetate and bis(triphenylphosphine)palladium chloride were added to container E, and 1,4-dioxane solvent was injected to form mixture Y2. Then, the mixture Y2 was heated in an oil bath to allow it to react in container E. After the reaction was completed, the mixture Y2 was filtered to obtain a solution. The solvent was then removed by vacuum evaporation. Hexane and dichloromethane were mixed to form a solvent, which was used as the eluent for purification on a silica gel column. The purified product was a white powdery solid compound R4.

[0017] The specific preparation process of compounds m2 and m2o is as follows: Under a protective gas environment, compounds R3 and R4 are placed in container F, and a magnetic stir bar is placed in the container. Then, the air in container F is replaced with a protective gas. Tetra(triphenylphosphine)palladium and potassium hydroxide are added to container F, and tetrahydrofuran solvent is injected to form mixture Z2. Then, the mixture Z2 is heated in an oil bath to allow the mixture Z2 to react in container F. After the reaction is complete, the mixture Z2 is filtered to obtain a solution. The solvent is then removed by vacuum evaporation. Hexane and dichloromethane are mixed to form a solvent, which is used as an eluent for purification on a silica gel column. The purified product is a white powdery solid organic molecule compound m2. Lead dioxide is mixed with the reacted compound m2 and stirred in dichloromethane solvent for ten minutes to obtain compound m2o.

[0018] The preparation process of compound R5 is as follows: Under a protective gas environment, compound R1 and 4-bromo-4-iodobiphenyl are placed in container G, and a magnetic wave is placed in the container. Then, the air in container G is replaced with a protective gas. Tetra(triphenylphosphine)palladium and potassium hydroxide are added to container G, and tetrahydrofuran solvent is injected to form mixture X3. Then, the mixture X3 is heated in an oil bath to react in container G. After the reaction is complete, the mixture X3 is filtered to obtain a solution. The solvent is then removed by vacuum evaporation. Hexane is used as the eluent for purification in a silica gel column. The purified product is a white powdery solid compound R5.

[0019] The synthesis process of compounds m3 and m3o is as follows: Under a protective gas environment, compounds R4 and R5 are placed in container H, and a magnetic stir bar is placed in the container. Then, the air in container H is replaced with a protective gas. Tetra(triphenylphosphine)palladium and potassium hydroxide are added to container H, and tetrahydrofuran solvent is injected to form a mixture Y3. Then, the mixture Y3 is heated in an oil bath to react in container H. After the reaction is complete, the mixture Y3 is filtered to obtain a solution. The solvent is then removed by vacuum evaporation. Hexane and dichloromethane are mixed to form a solvent, which is used as an eluent for purification on a silica gel column. The purified product is a white powdery solid organic molecule compound m3. Lead dioxide is mixed with the reacted compound m3 and stirred in dichloromethane solvent for ten minutes to obtain compound m3o.

[0020] Preferably, the molar ratio of tetra(triphenylphosphine)palladium to potassium hydroxide is 1:30.

[0021] Preferably, the volume ratio of n-hexane to dichloromethane is 3:1.

[0022] Preferably, the oil bath heating temperature is 75℃-100℃.

[0023] The above-mentioned technical features can be combined in various suitable ways or replaced by equivalent technical features, as long as the purpose of the present invention can be achieved.

[0024] The present invention provides a stable phenoxy radical unimolecular junction with regulated spin distribution and its preparation method, which, compared with the prior art, has at least the following advantages:

[0025] (1) This invention yields a class of organic free radical monolayers that are stable at room temperature (e.g., Figure 4 (as shown);

[0026] (2) In this invention, the conductivity of the free radical monomolecular junction changes significantly in the single-molecule test;

[0027] (3) In the single-molecule test, the conductivity of the free radical single-molecule junction in this invention shows a regular change that matches its spin density distribution. Attached Figure Description

[0028] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0029] Figure 1 A schematic diagram of free radicals is shown;

[0030] Figure 2 The spin density distribution of the conjugated bis(phenoxy)azobenzene diradical is shown;

[0031] Figure 3A schematic diagram of the single-molecule device structure is shown;

[0032] Figure 4 The molecular formula of the phenoxy radical unary junction involved in this invention is shown;

[0033] Figure 5 A schematic diagram of the preparation of intermediate product R1 is shown;

[0034] Figure 6 A schematic diagram of the preparation of intermediate product R2 is shown;

[0035] Figure 7 A schematic diagram of the preparation of products m1 and m1o is shown;

[0036] Figure 8 A schematic diagram of the preparation of intermediate product R4 is shown;

[0037] Figure 9 A schematic diagram of the preparation of intermediate product R3 is shown;

[0038] Figure 10 A schematic diagram of the preparation of products m2 and m2o is shown;

[0039] Figure 11 A schematic diagram of the preparation of intermediate product R5 is shown;

[0040] Figure 12 A schematic diagram of the preparation of products m3 and m3o is shown;

[0041] Figure 13 This shows a schematic diagram of the STM-BJ connection in this invention;

[0042] Figure 14 The electron spin distribution diagrams of m1o, m2o, and m3o are shown.

[0043] Figure 15 The image shows the UV absorption spectrum of the molecule before oxidation, the UV absorption spectrum of the free radical molecule after oxidation, and the molecular absorption peak.

[0044] Figure 16 The results of ESR tests on free radical molecules are shown.

[0045] Figure 17 The results of molecular conductivity tests before oxidation are shown;

[0046] Figure 18 A schematic diagram of the molecular conductive pathway before oxidation is shown (the green highlighted part is the conductive pathway);

[0047] Figure 19 The results of the free radical molecular conductivity test after oxidation are shown. Detailed Implementation

[0048] The invention will now be further described with reference to the accompanying drawings.

[0049] This invention provides a stable phenoxy radical monolayer with regulated spin distribution and its preparation method.

[0050] Example 1: m1 and m1o

[0051] like Figure 5 As shown, the specific steps for preparing R1 are as follows: Under nitrogen atmosphere, 4-bromo-2,6-di-tert-butylphenol (8.55 g, 3 mol) and bis(triphenylphosphine) borate (10.12 g, 4 mol) were placed in a 500 mL two-necked flask, and a magnetic stir bar was placed in place. The air in the two-necked flask was then replaced with nitrogen. Potassium acetate (7.84 g, 8 mol) and palladium bis(triphenylphosphine)chloride (1.1 g, 0.3 mol) were added to the two-necked flask, and 200 mL of 1,4-dioxane solvent was injected. The oil bath heater was then adjusted to 100 °C, and the mixture was allowed to react for approximately 12 hours. After the reaction was complete, the mixture was filtered to obtain a solution. The solvent was then removed by vacuum evaporation. A mixed solvent of n-hexane and dichloromethane in a 2:1 volume ratio was prepared and used as the eluent for purification on a silica gel column. The purified product was a white powdery solid, which was the desired compound R1 (7.43 g), with a yield of approximately 74.6%. It was used in the next stage of experiments.

[0052] like Figure 6 As shown, the specific steps for preparing R2 are as follows: 1,3,5-tribromobenzene (3.11 g, 1 mol) and 4-methylthiophenylboronic acid (3.3 g, 1.9 mol) were placed in a 500 mL two-necked flask, and a magnetic stir bar was placed in place. The air in the two-necked flask was then replaced with nitrogen. Tetra(triphenylphosphine)palladium (1.15 g, 0.1 mol) and potassium carbonate (6.9 g, 5 mol) were added to the two-necked flask, and 200 mL of a water:ethanol:toluene mixture (1:1:3) was injected. The oil bath heater was then adjusted to 90 °C, and the mixture was allowed to react for approximately 24 hours. The reacted mixture was then filtered to obtain a solution. The solvent was removed by vacuum evaporation. A mixed solvent of n-hexane and dichloromethane in a 3:1 volume ratio was prepared and used as the eluent for purification on a silica gel column. The purified product was a white powdery solid, which was the desired compound R2 (2.96 g), with a yield of 73.8%. It is prepared and used in the next experiment.

[0053] like Figure 7As shown, the specific process for preparing m1 and m1o is as follows: Under nitrogen atmosphere, R1 (400.8 mg, 0.12 mol) and R2 (401 mg, 0.1 mol) were placed in a 50 mL two-necked flask, and a magnetic stir bar was placed in place. The air in the two-necked flask was then replaced with nitrogen. Tetra(triphenylphosphine)palladium (57 mg, 0.1 mol) and potassium hydroxide (84 mg, 3 mol) were added to the two-necked flask, and 20 mL of tetrahydrofuran solvent was injected. The oil bath heater was then adjusted to 75 °C, and the mixture was allowed to react for approximately 12 hours. After the reaction was complete, the mixture was filtered to obtain a solution. The solvent was then removed by vacuum evaporation. A mixed solvent of n-hexane and dichloromethane in a 3:1 volume ratio was prepared and used as the eluent for purification on a silica gel column. The purified product was a white powdery solid, which was the desired organic molecular product m1 (285.6 mg), with a yield of 54.3%. The purified product m1 was preserved, and then lead dioxide and the reacted m1 were placed in a two-necked flask and stirred in dichloromethane solvent for ten minutes to obtain product m1o. The oxidized product was filtered and evaporated to obtain product 237.6 mg directly, with a yield of 83.2%.

[0054] Example 2: m2 and m2o

[0055] like Figure 8 As shown, the specific process for preparing R4 is as follows: Under nitrogen atmosphere, R2 (401 mg, 0.1 mol) and bis(pinacolborate) (303.6 mg, 0.12 mol) were placed in a 50 mL double-necked flask, and a magnetic stir bar was placed in place. The air in the double-necked flask was then replaced with nitrogen. Potassium acetate (7.84 g, 8 mol) and palladium bis(triphenylphosphine)chloride (1.1 g, 0.3 mol) were added to the double-necked flask, and 20 mL of 1,4-dioxane solvent was injected. The oil bath heater was then adjusted to 100 °C, and the mixture was allowed to react for 12 hours. The reacted mixture was then filtered to obtain a solution. The solvent was removed by vacuum evaporation. A mixed solvent of n-hexane and dichloromethane in a 2:1 volume ratio was prepared and used as the eluent for purification on a silica gel column. The purified product was a white powdery solid, which was the desired compound R4 (248.3 mg), with a yield of 74.8%. It is prepared and used in the next experiment.

[0056] like Figure 9As shown, the specific process for preparing compound R3 is as follows: Under nitrogen atmosphere, R1 (332 mg, 0.1 mol) and 1-bromo-4-iodobenzene (282 mg, 0.1 mol) were placed in a 50 mL two-necked flask, and a magnetic stir bar was placed in place. The air in the two-necked flask was then replaced with nitrogen. Tetra(triphenylphosphine)palladium (57 mg, 0.1 mol) and potassium hydroxide (84 mg, 3 mol) were added to the two-necked flask, and 20 mL of tetrahydrofuran solvent was injected. The oil bath heater was then adjusted to 75 °C, and the mixture was allowed to react for 12 hours. The reacted mixture was then filtered to obtain a solution. The solvent was removed by vacuum evaporation, and the solution was purified using n-hexane as the eluent in a silica gel column chromatography. The purified product was a white powdery solid, which was the desired compound R3 (267.2 mg), with a yield of 73.8%. This product was used in the next stage of experiments.

[0057] like Figure 10 As shown, the specific preparation process of compounds m2 and m2o is as follows: Under nitrogen atmosphere, R3 (36.2 mg, 0.01 mol) and R4 (33.2 mg, 0.01 mol) were placed in a 10 mL double-necked flask, and a magnetic stir bar was placed in place. The air in the double-necked flask was then replaced with nitrogen. Tetra(triphenylphosphine)palladium (5.7 mg, 0.01 mol) and potassium hydroxide (8.4 mg, 0.3 mol) were added to the double-necked flask, and 4 mL of tetrahydrofuran solvent was injected. The oil bath heater was then adjusted to 75 °C, and the mixture was allowed to react for approximately 12 hours. The reacted mixture was then filtered to obtain a solution. The solvent was removed by vacuum evaporation. A mixed solvent of n-hexane and dichloromethane in a 3:1 volume ratio was prepared and used as the eluent for purification on a silica gel column. The purified product was a white powdery solid, which was the desired organic molecular product m2 (21.29 mg), with a yield of 53.1%. The purified product m2 was preserved. Then, lead dioxide and the reacted m2 were placed in a two-necked flask and stirred in dichloromethane solvent for ten minutes to obtain product m2o. The oxidized product was filtered and evaporated to dryness, yielding 17.39 mg of product, with a yield of 81.6%.

[0058] Example 3: m3 and m3o

[0059] like Figure 11As shown, the preparation process of compound R5 is as follows: Under nitrogen atmosphere, R1 (332 mg, 0.1 mol) and 4-bromo-4-iodobiphenyl (430.8 mg, 0.12 mol) were placed in a 50 mL two-necked flask, and a magnetic stir bar was placed in place. The air in the two-necked flask was then replaced with nitrogen. Tetra(triphenylphosphine)palladium (57 mg, 0.1 nmol) and potassium hydroxide (84 mg, 3 nmol) were added to the two-necked flask, and 20 mL of tetrahydrofuran solvent was injected. The oil bath heater was then adjusted to 75 °C, and the mixture was allowed to react for approximately 12 hours. The reacted mixture was then filtered to obtain a solution. The solvent was removed by vacuum evaporation, and the solution was purified using n-hexane as the eluent in a silica gel column chromatography. The purified product was a white powdery solid, which was the desired compound R5 (259.2 mg), with a yield of 71.6%. This product was used in the next stage of experiments.

[0060] like Figure 12 As shown, the synthesis process of compounds m3 and m3o is as follows: Under nitrogen atmosphere, R4 (44.8 mg, 0.01 mol) and R5 (36.2 mg, 0.01 mol) were placed in a 10 mL two-necked flask, and a magnetic stir bar was placed in place. The air in the two-necked flask was then replaced with nitrogen. Tetra(triphenylphosphine)palladium (5.7 mg, 0.01 mol) and potassium hydroxide (8.4 mg, 0.3 mol) were added to the two-necked flask, and 4 mL of tetrahydrofuran solvent was injected. The oil bath heater was then adjusted to 75 °C, and the mixture was allowed to react for approximately 12 hours. The reacted mixture was then filtered to obtain a solution. The solvent was removed by vacuum evaporation. A mixed solvent of n-hexane and dichloromethane in a 3:1 volume ratio was prepared and used as the eluent for purification on a silica gel column. The purified product was a white powdery solid, which was the desired organic molecular product m3 (37.09 mg), with a yield of 54.7%. The purified product m3 was preserved, and then (iv) lead dioxide and the reacted m3 were placed in a two-necked flask and stirred in dichloromethane solvent for ten minutes to obtain product m3o. The oxidized product was filtered and evaporated to dryness, directly yielding 30.56 mg of product, with a yield of 82.4%.

[0061] Experimental approach

[0062] like Figure 13 As shown, with dithiomethyl terphenyl as the core structure, the degree of electron delocalization was changed by altering the number of benzene rings between the phenoxy radical and the conductive pathway. The changes in conductivity were observed, and the electron spin distribution law was summarized.

[0063] Theoretical calculations and experimental results

[0064] First, density functional calculations were performed on a series of molecules, and the results are as follows: Figure 14As shown, we can see that as the benzene ring chain grows, the probability of unpaired electrons delocalizing into the conductive path decreases significantly. In particular, a large number of unpaired electrons in m1o delocalize to the central benzene ring in the conductive path, while only a small number in m2o enter the central benzene ring. After extending two benzene rings, i.e. in m3o, the number of electrons delocalized to the central benzene ring is almost 0.

[0065] Table 1 shows the energy level calculation results of the six molecules involved in this invention. It can be seen that the molecular band gap (HOMO-LUMO gap) of the oxidized free radical molecules is smaller than that of the unoxidized molecules, and it also decreases with the growth of the benzene ring chain.

[0066] Table 1. Molecular HOMO and LUMO calculation results

[0067]

[0068] We also conducted UV-Vis absorption spectroscopy tests on it, such as... Figure 15 As shown, it can be seen that with the growth of the central benzene ring chain, the absorption spectra of both the unoxidized and oxidized free radical molecules exhibit a red shift. Secondly, from the absorption spectra of the oxidized free radical molecules, it is clearly visible that all three molecules show absorption peaks in the 500nm-750nm wavelength range. These small, bulging peaks in this range are characteristic peaks of free radicals, proving that we have obtained free radical molecules.

[0069] Electron spin resonance (ESR) tests were performed on free radical molecules, and the results are as follows: Figure 16 As shown in the figure, the absorption peaks of the free radical molecules are quite obvious and conform to the characteristic that a single free radical has only one absorption peak. Based on the ESR test results, we can confirm that m1o, m2o, and m3o are the three free radical molecules designed in this invention.

[0070] The conductivity of six molecules was measured using the STMBJ device, and the results are as follows: Figure 17 As shown. The molecule before oxidation does not contain unpaired electrons, therefore it does not experience electron delocalization and does not affect the conductive pathway, as... Figure 18 As shown, the conductive pathways of m1, m2, and m3 are all formed by the thiomethyl group connected at positions 3 and 5 and the central benzene ring. Therefore, the conductivity of the three molecules before oxidation is all in G0. -5.5 To G0 -5.6 The left and right positions are within the acceptable error range.

[0071] STMBJ tests were performed on the oxidized molecules m1o, m2o, and m3o, and the results are as follows: Figure 19 As shown.

[0072] First, the conductivity of m1o is G0. -3.41 Compared to G0 before oxidation -5.51 The conductivity value increased by 2.1 orders of magnitude, with G0- observed in the m1o test. 5.52 The conductivity peak was confirmed to be the conductivity peak that appears after m1o is reduced to m1. The conductivity value of m2 was measured as G0. -4.26 Compared to the unoxidized m2 molecule G0 -5.66 Compared to the original m3 molecule, the conductivity of m1o increased by 1.4 orders of magnitude, while the conductivity of m3o remained almost unchanged compared to the unoxidized m3 molecule. This verifies our DFT calculation results, which show that a large number of electron spins of m1o are delocalized to the central benzene ring, thus affecting the conductivity pathway. The number of electrons delocalized to the conductivity pathway of m2o is significantly reduced, resulting in a smaller increase in conductivity than that of m1o. As for m3o, the probability of its spin distribution on the central benzene ring is almost 0, thus having almost no effect on the conductivity pathway. Therefore, the conductivity value is not significantly different from that of the unoxidized m3 molecule.

[0073] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A stable phenoxy radical monomolecular knot that regulates spin distribution, characterized in that, The monomolecular junction can characterize the spin distribution changes of organic free radical molecules in the form of molecular conductivity. The molecular formula of the monomolecular junction is: or or .

2. The method for preparing stable phenoxy radical unimolecular junctions with controlled spin distribution according to claim 1, characterized in that, The specific steps for preparing compound R1 are as follows: Under a protective gas environment, 4-bromo-2,6-di-tert-butylphenol and dipinacol boronic acid ester were placed in container A, and a magnetic stir bar was placed in the container. Subsequently, the air in container A was replaced with a protective gas. Potassium acetate and bis(triphenylphosphine)palladium chloride were added to container A, and 1,4-dioxane solvent was injected to form mixture X1. Then, the mixture X1 was heated in an oil bath to allow it to react in container A. After the reaction was completed, the mixture X1 was filtered to obtain a solution. The solvent was then removed by vacuum evaporation. Hexane and dichloromethane were used as a mixed solvent and used as the eluent for purification on a silica gel column. The purified product was a white powdery solid compound R1. The specific steps for preparing compound R2 are as follows: 1,3,5-tribromobenzene and 4-methylthiophenylboronic acid are placed in container B, and a magnetic stir bar is placed in the container. Then, the air in the double-necked flask is replaced with a protective gas. Tetra(triphenylphosphine)palladium and potassium carbonate are added to container B, and a mixed solvent of water, ethanol, and toluene is injected to form mixture Y1. Then, the mixture Y1 is heated in an oil bath to react in container B. After the reaction is complete, the mixture Y1 is filtered to obtain a solution. The solvent is then removed by vacuum evaporation. Hexane and dichloromethane are mixed to form a solvent, which is used as an eluent for purification on a silica gel column. The purified product is a white powdery solid compound R2. The specific process for preparing compounds m1 and m1o is as follows: Under a protective gas environment, compounds R1 and R2 are placed in container C, and a magnetic stir bar is placed in the container. The air in container C is then replaced with a protective gas. Tetra(triphenylphosphine)palladium and potassium hydroxide are added to container C, and tetrahydrofuran solvent is injected to form mixture Z1. The mixture Z1 is then heated in an oil bath to react in container C. The reacted mixture Z1 is then filtered to obtain a solution. The solvent is removed by vacuum evaporation. Hexane and dichloromethane are mixed and used as eluent for purification on a silica gel column. The purified product is a white powdery solid organic molecule compound m1. Lead dioxide is mixed with the reacted compound m1 and stirred in dichloromethane solvent for ten minutes to obtain compound m1o. The molecular formula of compound m1o is: 。 3. The method for preparing stable phenoxy radical unimolecular junctions with controlled spin distribution according to claim 1, characterized in that, The specific process for preparing compound R3 is as follows: Under a protective gas environment, compound R1 and 1-bromo-4-iodobenzene are placed in container D, and a magnetic stir bar is placed in the container. Subsequently, the air in container D is replaced with a protective gas. Tetra(triphenylphosphine)palladium and potassium hydroxide are added to container D, and tetrahydrofuran solvent is injected to form mixture X2. Then, the mixture X2 is heated in an oil bath to react in container D. After the reaction is complete, the mixture X2 is filtered to obtain a solution. The solvent is then removed by vacuum evaporation, and n-hexane is used as the eluent for purification on a silica gel column. The purified product is a white powdery solid compound R3. The specific process for preparing compound R4 is as follows: Under a protective gas environment, compound R2 and bis-pinacol boronic acid ester were placed in container E, and a magnetic stir bar was placed in the container. Subsequently, the air in container E was replaced with a protective gas. Potassium acetate and bis(triphenylphosphine)palladium chloride were added to container E, and 1,4-dioxane solvent was injected to form mixture Y2. Then, the mixture Y2 was heated in an oil bath to allow it to react in container E. After the reaction was completed, the mixture Y2 was filtered to obtain a solution. The solvent was then removed by vacuum evaporation. Hexane and dichloromethane were mixed to form a solvent, which was used as the eluent for purification on a silica gel column. The purified product was a white powdery solid compound R4. The specific preparation process of compounds m2 and m2o is as follows: Under a protective gas environment, compounds R3 and R4 are placed in container F, and a magnetic stir bar is placed in the container. The air in container F is then replaced with a protective gas. Tetra(triphenylphosphine)palladium and potassium hydroxide are added to container F, and tetrahydrofuran solvent is injected to form mixture Z2. The mixture Z2 is then heated in an oil bath to allow it to react in container F. The reacted mixture Z2 is then filtered to obtain a solution. The solvent is removed by vacuum evaporation. A mixed solvent of n-hexane and dichloromethane is used as the eluent for purification on a silica gel column. The purified product is a white powdery solid organic molecule, compound m2. Lead dioxide is mixed with the reacted compound m2 and stirred in dichloromethane solvent for ten minutes to obtain compound m2o. The molecular formula of compound m2o is: 。 4. The method for preparing stable phenoxy radical unimolecular junctions with controlled spin distribution according to claim 1, characterized in that, The preparation process of compound R5 is as follows: Under a protective gas environment, compound R1 and 4-bromo-4-iodobiphenyl are placed in container G, and a magnetic wave is placed in the container. Then, the air in container G is replaced with a protective gas. Tetra(triphenylphosphine)palladium and potassium hydroxide are added to container G, and tetrahydrofuran solvent is injected to form mixture X3. Then, the mixture X3 is heated in an oil bath to react in container G. After the reaction is complete, the mixture X3 is filtered to obtain a solution. The solvent is then removed by vacuum evaporation. Hexane is used as the eluent for purification in a silica gel column. The purified product is a white powdery solid compound R5. The synthesis processes of compounds m3 and m3o are as follows: Under a protective gas environment, compounds R4 and R5 are placed in container H, and a magnetic stir bar is placed in the container. The air in container H is then replaced with a protective gas. Tetra(triphenylphosphine)palladium and potassium hydroxide are added to container H, and tetrahydrofuran solvent is injected to form mixture Y3. The mixture Y3 is then heated in an oil bath to react in container H. The reacted mixture Y3 is then filtered to obtain a solution. The solvent is removed by vacuum evaporation. A mixed solvent of n-hexane and dichloromethane is used as the eluent for purification on a silica gel column. The purified product is a white powdery solid organic molecule, compound m3. Lead dioxide is mixed with the reacted compound m3 and stirred in dichloromethane solvent for ten minutes to obtain compound m3o. The molecular formula of compound m3o is: 。 5. The method for preparing stable phenoxy radical unimolecular junctions with controlled spin distribution according to any one of claims 2 to 4, characterized in that, The molar ratio of tetra(triphenylphosphine)palladium to potassium hydroxide is 1:

30.

6. The method for preparing stable phenoxy radical unimolecular junctions with controlled spin distribution according to any one of claims 2 to 4, characterized in that, The volume ratio of n-hexane to dichloromethane is 3:

1.

7. The method for preparing stable phenoxy radical unimolecular junctions with controlled spin distribution according to any one of claims 2 to 4, characterized in that, The oil bath heating temperature is 75℃-100℃.

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