Free radical molecular wire with tunable quantum interference effect and preparation method thereof

Abstract

The present application provides a radical molecular wire with tunable quantum interference effect and a preparation method thereof, belonging to the technical field of electrical components using organic materials as the active part. Using 3,5-dibromobenzaldehyde and N,N'-dihydroxy-2,3-dimethyl-2,3-butanediamine as the initial raw materials, then successively adding tert-butyldimethylchlorosilane, different anchoring groups and tetrabutylammonium fluoride, and finally obtaining the final product. The radical molecular wire provided in this case can achieve the regulation of the quantum interference effect, and the preparation method is simple and the reaction process is mild.

Description

Technical Field

[0001] The present application relates to a radical molecular wire capable of effectively regulating the quantum interference effect and a preparation method thereof, so as to control the electrical transport properties of single-molecule devices, belonging to the technical field of electrical components using organic materials as the active part. Background Art

[0002] The manufacturing process of integrated circuits has advanced in a top-down manner and has developed to date according to Moore's law. After decades of development, the feature size of semiconductor devices has approached its physical limit. If single molecules are used as electronic components to construct integrated circuits from the bottom up, it is expected to further reduce the feature size, thereby further improving the integration density of integrated circuits. Molecular electronics mainly studies the electrical properties of single molecules, providing a basis for constructing single-molecule electronic components from the bottom up and then assembling integrated circuits.

[0003] As early as 1974, Arieh Aviram and Mark Ratner proposed a theory on single-molecule electrical transport, that is, unidirectional electron transport can occur between the donor and acceptor in a single molecule. Through theoretical calculations and deductions, it was obtained that a molecule with a "Donor-Bridge-Acceptor" structure can be used to construct a molecular rectifier (Chemical Physics Letters, 1974, 29). Their research shows that it is promising to construct and study single-molecule conductance by experimental means.

[0004] In single-molecule devices, due to the existence of multiple discrete orbital energy levels, electrons will interfere with each other when transporting between different energy levels. When constructive quantum interference (CQI) exists, its conductance increases. On the contrary, when destructive quantum interference (DQI) exists, low conductance is presented. This is the quantum interference effect in the electrical transport process of single-molecule devices.

[0005] The researchers used the self-developed scanning tunneling break junction technique to study three molecules, AC, AQ, and AH, and successfully observed the destructive quantum interference phenomenon at the single-molecule scale in the experiment (Beilstein Journal of Nanotechnology, 2011, 2: 699 - 713). Subsequently, a series of influencing factors of quantum interference effects were explored, such as different conductance transport paths (Chinese Chemical Letters, 2018, 29(1): 147 - 150), side-site relationships (Nature Communications, 2015, 6: 6389), heteroatom effects (Angewandte Chemie International Edition, 2017, 56(1): 173 - 176), etc. These research works provide a good theoretical basis for the subsequent design of molecular devices with ideal functions and research.

[0006] Therefore, how to regulate the quantum interference effect through molecular structure design to obtain specific electrical properties is the focus and difficulty in the field of molecular electronics. Summary of the Invention

[0007] In view of the defects existing in the prior art, the applicant provides an organic radical molecular wire, which can realize the regulation of the quantum interference effect, and the related molecules can be used to construct electronic components.

[0008] This case first provides a radical molecular wire containing a meta-radical molecule, which has the following general formula:

[0009]

[0010] In the general formula, R is an anchoring group of any of the following structures:

[0011]

[0012] The preparation method of the above radical molecular wire containing a meta-radical molecule is as follows:

[0013] (1) 3,5-Dibromobenzaldehyde reacts with N,N'-dihydroxy-2,3-dimethyl-2,3-butanediamine to obtain intermediate c:

[0014]

[0015] (2) tert-Butyldimethylchlorosilane reacts with intermediate c to obtain intermediate d:

[0016]

[0017] (3) Let the anchoring group react with intermediate d to obtain intermediate f:

[0018]

[0019] (4) Intermediate f reacts with tetrabutylammonium fluoride to obtain the following final product:

[0020]

[0021] In the above preparation process, 3,5-dibromobenzaldehyde and N,N'-dihydroxy-2,3-dimethyl-2,3-butanediamine are used as the starting materials, and then tert-butyldimethylchlorosilane, different anchoring groups, and tetrabutylammonium fluoride are added in sequence, and finally the final product is obtained. The preparation method is simple and the reaction process is mild.

[0022] Furthermore, as a preference:

[0023] In step (1), the reaction solvent is methanol, and the molar ratio of 3,5-dibromobenzaldehyde to N,N'-dihydroxy-2,3-dimethyl-2,3-butanediamine is 1-1.1:1.3-1.8. Under nitrogen protection, the reaction is carried out at room temperature for 20 h.

[0024] In step (2), imidazole is added. Because in the solution, the N-H group of imidazole shows a negative charge, making it alkaline, which helps the occurrence of the whole reaction.

[0025] In step (2), the molar ratio of intermediate c to tert-butyldimethylchlorosilane is 1-1.1:5-5.5, the reaction solvent is DMF, and the reaction is stirred at 65 °C for 90 h under nitrogen protection.

[0026] In step (3), bis(triphenylphosphine)palladium dichloride or tetrakis(triphenylphosphine)palladium is added as a catalyst. These two catalysts have good solubility in the reaction solvent, and the electron-donating ability of the ligand interacting with palladium helps the occurrence of the whole catalytic reaction.

[0027] In step (3), the molar ratio of intermediate d to different anchoring groups is 1-1.2:2.3-2.8, the reaction solvent is THF:TEA = 1:1, and the reaction is carried out at 65 °C for 24 h under nitrogen protection.

[0028] In step (4), the reaction solvent is THF, and the molar ratio of intermediate f to tetrabutylammonium fluoride is 1-1.2:2-2.4, and the reaction is carried out at room temperature for 12 h.

[0029] Meanwhile, this case also provides a radical molecular wire containing a meta-radical molecule, which has the following general formula:

[0030]

[0031] In the general formula, R is an anchoring group with any of the following structures:

[0032]

[0033] The preparation method of the radical molecular wire containing the ortho-radical molecule is as follows:

[0034] (1) 2,4-Dibromobenzaldehyde reacts with the anchoring group to obtain intermediate j:

[0035]

[0036] (2) N,N'-Dihydroxy-2,3-dimethyl-2,3-butanediamine reacts with intermediate j to obtain intermediate l:

[0037]

[0038] (3) Sodium periodate reacts with intermediate l to obtain the following final product:

[0039]

[0040] In the above preparation process, 2,4-dibromobenzaldehyde and different anchoring groups are used as the initial raw materials, and then N,N'-dihydroxy-2,3-dimethyl-2,3-butanediamine and sodium periodate are added in sequence to finally obtain the final product. The preparation method is simple and the reaction process is mild.

[0041] In step (1), bis(triphenylphosphine)palladium dichloride or tetrakis(triphenylphosphine)palladium is added as a catalyst. These two catalysts have good solubility in the reaction solvent, and the electron-donating ability of the ligand interacting with palladium contributes to the occurrence of the whole catalytic reaction.

[0042] In step (1), the molar ratio of 2,4-dibromobenzaldehyde to different anchoring groups is 1-1.2:2.3-2.8, the reaction solvent is THF:TEA = 1:1, and the reaction is carried out at 65 °C for 24 h under nitrogen protection.

[0043] In step (2), p-toluenesulfonic acid (p-TsOH·H2O) is added as an organic acid catalyst. The addition of the acid protonates the carbonyl oxygen, greatly improving the electrophilicity of the carbonyl carbon atom, which helps the nucleophilic addition of the hydroxylamine compound to the carbonyl group.

[0044] In step (2), the molar ratio of intermediate (j) to N,N'-dihydroxy-2,3-dimethyl-2,3-butanediamine is 1-1.2:1.7-3.1. The reaction solvent is THF:MeOH = 2:1, and the reaction is stirred at room temperature for 24 h under nitrogen protection.

[0045] In step (3), the reaction temperature is 0-10 °C, the molar ratio of intermediate (l) to sodium periodate is 1-1.2:3-5, and the reaction is carried out at room temperature in the dark for 2 h.

[0046] The above method of effectively regulating the quantum interference effect by preparing ortho- and meta-organic radical molecules, and then controlling the electrical transport properties of single molecules, provides a good theoretical basis for the design and research of molecular devices with ideal functions. Description of the Drawings

[0047] Figure 1 1H-NMR spectrum of molecule c; 1 1H-NMR spectrum of molecule c;

[0048] Figure 2 13C-NMR spectrum of molecule c; 13 13C-NMR spectrum of molecule c;

[0049] Figure 3 1H-NMR spectrum of molecule d; 1 1H-NMR spectrum of molecule d;

[0050] Figure 4 13C-NMR spectrum of molecule d; 13 13C-NMR spectrum of molecule d;

[0051] Figure 5 1H-NMR spectrum of molecule f; 1 1H-NMR spectrum of molecule f;

[0052] Figure 6 13C-NMR spectrum of molecule f; 13 13C-NMR spectrum of molecule f;

[0053] Figure 7 1H-NMR spectrum of molecule h; 1 1H-NMR spectrum of molecule h;

[0054] Figure 8 Mass spectrum of molecule i;

[0055] Figure 9 UV-Vis absorption spectrum of the meta-radical molecule (molecule g) of the present application in THF (c~7×10 -6 M) solution;

[0056] Figure 10 1H-NMR spectrum of molecule j; 1 1H-NMR spectrum of molecule j;

[0057] Figure 11 13C-NMR spectrum of molecule j; 13 13C-NMR spectrum of molecule j;

[0058] Figure 12 1H-NMR spectrum of molecule l; 1 1H-NMR spectrum of molecule l;

[0059] Figure 13 13C-NMR spectrum of molecule l; 13 13C-NMR spectrum of molecule l;

[0060] Figure 14 1H-NMR spectrum of molecule m; 11H-NMR spectrum;

[0061] Figure 15 is the mass spectrum of molecule m;

[0062] Figure 16 is the ultraviolet-visible absorption spectrum of the ortho-radical molecule (molecule m) of the present application in a THF (c ~ 10 -6 M) solution;

[0063] Figure 17 is the electrical characterization result diagram of the pure solvent;

[0064] Figure 18 is the single-molecule conductance test diagram. Detailed implementation mode

[0065] The organic radical molecular structure has diversity, and the anchoring group can be structures such as (4-ethylphenyl)(methyl)sulfonamide, 4-ethynylpyridine, and S-(4-ethynylphenyl)ethanethiolate. Only when the anchoring group is (4-ethylphenyl)(methyl)sulfonamide, the following examples have detailed synthesis and characterization.

[0066] Example 1

[0067] In this example, the synthesis of the meta-radical molecule g is carried out, and the specific reaction formula is expressed as follows:

[0068]

[0069] The following is a specific elaboration in combination with the corresponding steps.

[0070] (1) Synthesis of the intermediate with chemical structure c:

[0071] Add compound a (3.00 g, 11.37 mmol) and compound b (3.03 g, 20.46 mmol) to a round-bottom flask and dissolve them in 30 mL of methanol. Stir at room temperature for 20 h under nitrogen protection, filter the white precipitate and wash it with methanol to obtain 2.76 g of white solid, with a yield of 61.5%.

[0072] Test the intermediate with structure c, and the results Figure 1 、 Figure 2 are shown.

[0073] The performance parameter characterization is as follows:

[0074] 1 1H-NMR (400 MHz, DMSO, δ / ppm): 7.97 (s, 2H), 7.72 (s, 1H), 7.67 (d, J = 1.7 Hz, 2H), 4.52 (s, 1H), 1.07 (s, 6H), 1.01 (s, 6H).

[0075] 13 C-NMR (100 MHz, DMSO, δ / ppm): 146.94, 132.12, 130.08, 121.86, 88.85, 66.46, 24.28, 17.30.

[0076] (2) Synthesis of the intermediate with chemical structure d:

[0077] Add the intermediate with structure c (2 g, 5.07 mmol), tert-butyldimethylchlorosilane (3.83 g, 25.37 mmol), and imidazole (3.45 g, 50.7 mmol) into a round-bottom flask, dissolve them in 30 mL of DMF, stir at 65 °C for 90 h under nitrogen protection. After cooling to room temperature, extract with DCM, dry with anhydrous magnesium sulfate, filter and concentrate by rotary evaporation, and then pass through a silica gel column using PE as the eluent. Obtain 1.74 g of white solid with a yield of 55%.

[0078] Test the intermediate with structure d, and the results Figure 3 、 4 are shown as follows.

[0079] The performance parameter characterization is as follows:

[0080] 1 H-NMR (400 MHz, CDCl3, δ / ppm): 7.58 (t, J = 1.7 Hz, 1H), 7.46 (d, J = 1.7, 2H), 4.54 (s, 1H), 1.14 (s, 12H), 0.81 (s, 18H), -0.01 (d, J = 5.2, 6H), -0.75 (s, 6H).

[0081] 13 C-NMR (100 MHz, CDCl3, δ / ppm): 133.63, 132.70, 122.26, 93.30, 68.52, 26.41, 24.91, 18.16, 17.45, -3.47, -4.59.

[0082] (3) Synthesis of the intermediate with chemical structure f:

[0083] Add molecule d (1.5 g, 2.41 mmol), molecule e (0.89 g, 6.03 mmol), CuI (0.018 g, 0.096 mmol) and Pd(PPh3)4 (0.056 g, 0.048 mmol) into a round-bottom flask, dissolve them in 20 mL of THF and 20 mL of TEA, react under nitrogen protection for 48 h, cool it to room temperature, extract with DCM, and dry with anhydrous magnesium sulfate. Filter and rotary evaporate, and then column chromatograph with (PE:DCM = 5:1) as the eluent. Obtain 0.87 g of pale yellow solid with a yield of 48%.

[0084] Test the intermediate with the structural formula f, and the results Figure 5 、 6 are shown as follows.

[0085] The performance parameters are characterized as follows:

[0086] 1 1H-NMR (CDCl3, 400 MHz, δ / ppm): 6.60 (s, 1H), 7.49 (s, 2H), 7.46 (d, J = 8.5 Hz, 4H), 7.22 (d, J = 8.3 Hz, 4H), 4.62 (s, 1H), 2.51 (s, 6H), 1.17 (s, 12H), 0.83 (s, 18H), -0.01 (s, 6H), -0.74 (s, 6H).

[0087] 13 13C-NMR (100 MHz, CDCl3, δ / ppm): 139.59, 134.27, 132.16, 126.07, 123.19, 119.71, 89.38, 89.27, 68.39, 29.92, 26.46, 18.18, 15.62, -3.46, -4.52.

[0088] (4) Synthesis of the radical molecule with the chemical structural formula g:

[0089] Add compound h (0.1 g, 0.13 mmol), TBAF (0.27 mL, concentration 1 mol / L) and 10 mL of tetrahydrofuran (THF) into a round-bottom flask, stir at room temperature for 12 h, rotary evaporate and then column chromatograph with (PE:DCM = 1:2) as the eluent to obtain 57 mg of blue solid with a yield of 82%.

[0090] Test the intermediate with the structural formula g, and the results Figure 7 、 8 are shown as in Figure 9.

[0091] The core performance parameters are characterized as follows:

[0092] 1H-NMR(CDCl3, 400 MHz, δ / ppm): 7.49 (s, 4H), 6.95 (s, 4H), 2.61 (s, 6H), 1.30 (s, 12H).

[0093] Example 2

[0094] In this example, the synthesis of the ortho-radical molecule m was carried out, and the reaction equation is expressed as follows:

[0095]

[0096] The specific process is as follows:

[0097] (1) Synthesis of the intermediate with chemical structure j:

[0098] Add molecule h (1 g, 3.79 mmol), molecule i (1.4 g, 9.47 mmol), CuI (0.022 g, 0.11 mmol) and Pd(PPh3)4 (0.18 g, 0.15 mmol) into a round-bottom flask, dissolve them in 20 mL of THF and 20 mL of TEA, react under nitrogen protection for 48 h, cool it to room temperature, extract with DCM, and dry with anhydrous magnesium sulfate. Filter and spin-dry, and column-chromatograph with (PE:DCM = 5:1) as the eluent. Obtain 0.7 g of yellow solid with a yield of 47%.

[0099] Test the intermediate with chemical structure j, and the results Figure 10 、 11 are shown as follows.

[0100] The core performance parameters are characterized as follows:

[0101] 1 H-NMR(CDCl3, 400 MHz, δ / ppm): 10.6 (s, 1H), 7.91 (d, J = 8.1 Hz, 1H), 7.77 (d, J = 1.3 Hz, 1H), 7.54 (d, J = 8.1 Hz, 1H), 7.50 - 7.42 (m, 4H), 7.23 (dd, J = 8.4, 4.7 Hz, 4H), 2.51 (s, 6H).

[0102] 13 C-NMR(100 MHz, CDCl3, δ / ppm): 191.13, 141.06, 136.03, 134.65, 132.26, 132.16, 131.36, 127.53, 125.94, 125.90, 88.28, 84.63, 77.23, 15.40.

[0103] (2) Synthesis of the intermediate with chemical structure l:

[0104] Add compound j (0.5 g, 1.25 mmol) and compound k (0.56 g, 3.76 mmol) into a round-bottom flask,

[0105] Dissolve TsOH·H2O (1.43 g, 7.53 mmol) in 30 mL of THF and 15 mL of MeOH. Stir at room temperature for 24 h under nitrogen protection. Add water and PE, and a solid will precipitate directly. Filter and wash with PE to obtain 0.42 g of green solid with a yield of 63%.

[0106] Test the intermediate with the structural formula l, and the results Figure 12 、 13 are shown as follows.

[0107] The core performance parameters are characterized as follows:

[0108] 1 1H-NMR (DMSO-d6, 400 MHz, δ / ppm): 7.73 (d, J = 8.1 Hz, 1H), 7.70 (s, 2H), 7.62 (s, 1H), 7.56 (d, J = 8.1 Hz, 1H), 7.47 (dd, J = 17.2, 8.4 Hz, 4H), 7.31 (t, J = 7.5 Hz, 4H), 5.29 (s, 1H), 2.49 (d, J = 1.7 Hz, 6H), 1.10 (d, J = 5.8 Hz, 12H).

[0109] 13 13C-NMR (100 MHz, CDCl3, δ / ppm): 143.95, 139.91, 139.72, 133.43, 131.79, 131.53, 130.71, 129.42, 125.64, 125.57, 124.31, 121.56, 118.57, 117.99, 66.46, 24.29, 17.56, 14.26, 14.19.

[0110] (2) Synthesis of the meta radical with the chemical structural formula m:

[0111] Wrap the round-bottom flask with tin foil paper and add compound l (0.2 g, 0.38 mmol) dissolved in 20 mL of THF. Slowly add an aqueous solution of NaIO4 (0.4 g, 1.9 mmol). After stirring for 2 h, quench the reaction with NH4Cl. Extract with DCM and column chromatograph with (PE:EA = 3:1) to obtain 85.5 mg of purple solid with a yield of 43%.

[0112] Test the intermediate with the structural formula m, and the results Figure 14 、 15 are shown in Figure 16.

[0113] The core performance parameters are characterized as follows:

[0114] 1 H-NMR(CDCl3, 400 MHz, δ / ppm): 8.41(s, 2H), 7.05(s, 4H), 6.87(s, 4H), 2.48(s, 3H), 2.43(s, 3H).

[0115] Electrical characterization:

[0116] The single-molecule conductance of radical molecules was measured using the scanning tunneling break junction technique (STM-BJ).

[0117] We selected TMB:THF (v 4:1) as the solvent system for the test molecules. Before each conductance measurement of the target molecule, the pure solvent was first tested to ensure the cleanliness of the experimental environment system and to correct the stretching rate of the counter electrode. The electrical characterization results of the pure solvent are as Figure 17 shown.

[0118] To study the effect of radical addition on the electrical transport properties of molecular wires, a 0.1 mM solution of ortho-radical molecules (using a mixed solvent system of (v TMB:THF 4:1)) was prepared, and the single-molecule conductance of the target molecule was measured under the same test conditions as the pure solvent. The one-dimensional conductance statistical chart and two-dimensional conductance-distance statistical chart of the target molecule are as Figure 18 shown. After Gaussian fitting, its conductance value was 10 -2.9±0.05 G0, while in the previously reported literature, there was destructive quantum interference in the undoped radical molecules, and its conductance value was 10 -5.5±0.05 G0. The results show that the conductance value of the radical-substituted molecular wire increased by more than two orders of magnitude. Further explanation indicates that doped radical molecules can effectively regulate the destructive quantum interference effect, thereby regulating the electrical transport properties of single molecules, providing a theoretical basis and experimental evidence for the design of molecular devices with ideal functions.

Claims

1. A radical molecular wire with regulated quantum interference effect, characterized in that, The radical molecular wire has a meta-radical molecular structure, and its general formula is expressed as: Alternatively, the radical molecular wire has an ortho-radical molecular structure, and its general formula is expressed as: R is an anchoring group of any one of the following structures:

2. A preparation method of a free radical molecular wire with regulated quantum interference effect, characterized in that, The radical molecular wire has a meta-radical molecular structure, and its general formula is expressed as: R is an anchoring group having any of the following structures: The preparation steps of the radical molecular wire are as follows: (1) In a methanol solution, 3,5-dibromobenzaldehyde reacts with N,N'-dihydroxy-2,3-dimethyl-2,3-butanediamine to obtain intermediate one. The structural formula of Intermediate I is as follows: (2) Add tert-butyldimethylchlorosilane and an imidazole solution, and tert-butyldimethylchlorosilane reacts with intermediate one to obtain intermediate two. The structural formula of the intermediate II is as follows: (3) Add the anchoring group R, and use bis(triphenylphosphine)palladium dichloride or tetrakis(triphenylphosphine)palladium as a catalyst. The anchoring group reacts with intermediate two to obtain intermediate three. The structural formula of Intermediate III is as follows: (4) Add tetrabutylammonium fluoride, and tetrabutylammonium fluoride reacts with intermediate three to obtain a radical molecular wire with a meta-radical molecular structure.

3. The preparation method of a radical molecular wire with regulated quantum interference effect according to claim 2, characterized in that: In step (1), the molar ratio of 3,5-dibromobenzaldehyde to N,N'-dihydroxy-2,3-dimethyl-2,3-butanediamine is 1 to 1.1:1.3 to 1.

8.

4. The preparation method of a radical molecular wire with a regulated quantum interference effect according to claim 2, characterized in that: In step (2), the molar ratio of intermediate one to tert-butyldimethylchlorosilane is 1 to 1.1:5 to 5.

5.

5. The preparation method of a free radical molecular wire with regulated quantum interference effect according to claim 2, characterized in that: In step (3), the molar ratio of intermediate two to the anchoring group is 1 to 1.2:2.3 to 2.

8.

6. The preparation method of a radical molecular wire with a regulated quantum interference effect according to claim 2, characterized in that: In step (4), the molar ratio of intermediate three to tetrabutylammonium fluoride is 1 to 1.2:2 to 2.

4.

7. A preparation method of a radical molecular wire with regulated quantum interference effect, characterized in that, The radical molecular wire has an ortho-radical molecular structure, and its general formula is expressed as: R is an anchoring group having any of the following structures: The preparation steps of the radical molecular wire are as follows: (1) Using bis(triphenylphosphine)palladium dichloride or tetrakis(triphenylphosphine)palladium as a catalyst, 2,4-dibromobenzaldehyde reacts with the anchoring group R to obtain intermediate one. The structural formula of Intermediate I is as follows: The anchoring group R is (2) Add N,N'-dihydroxy-2,3-dimethyl-2,3-butanediamine, and add p-toluenesulfonic acid as an organic acid catalyst. N,N'-dihydroxy-2,3-dimethyl-2,3-butanediamine reacts with intermediate one to obtain intermediate two. The structural formula of Intermediate II is as follows: (3) Add sodium periodate, and sodium periodate reacts with intermediate two to obtain a radical molecular wire with an ortho-radical molecular structure.

8. The preparation method of a radical molecular wire with regulated quantum interference effect according to claim 7, characterized in that: In step (1), the molar ratio of 2,4-dibromobenzaldehyde to the anchoring group is 1 to 1.2:2.3 to 2.

8.

9. The preparation method of a radical molecular wire with regulated quantum interference effect according to claim 7, characterized in that: In step (2), the molar ratio of intermediate one to N,N'-dihydroxy-2,3-dimethyl-2,3-butanediamine is 1 to 1.2:1.7 to 3.

1.

10. The preparation method of a radical molecular wire with regulated quantum interference effect according to claim 7, characterized in that: In step (3), the molar ratio of intermediate two to sodium periodate is 1 to 1.2:3 to 5.

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