Space-conjugated organic molecule based on hexaphenylbenzene anchoring group as well as preparation and application of space-conjugated organic molecule

Abstract

The invention belongs to the technical field of organic electronics, and discloses a space conjugated organic molecule based on a hexaphenylbenzene anchoring group as well as preparation and application of the space conjugated organic molecule. The space-conjugated organic molecule based on the hexaphenylbenzene anchoring group has a structure shown as I-III: the unique space-conjugated structure of the space-conjugated organic molecule enables electrons not only to be transmitted along a valence bond conjugation channel, but also to be transmitted along a space conjugation channel, and the space-conjugated organic molecule has a plurality of electric conduction channels, so that the space-conjugated organic molecule has a good application prospect. The low conductivity phenomenon caused by insufficient valence bond conjugation of meta-position modified molecules is effectively compensated. The preparation method is simple and applicable, and has a good application prospect in the field of organic monomolecular wires.

Description

Technical Field

[0001] The invention belongs to the technical field of organic electronics, and particularly relates to the preparation of spatially conjugated organic molecules based on hexaphenylbenzene anchoring groups and their application in the field of organic optoelectronics. Background Art

[0002] The preparation process of integrated circuits in the semiconductor industry has been developed in a top-down manner according to Moore's Law. The preparation of smaller components through silicon-based micromachining technology has reached a bottleneck. Molecular electronics has attracted much attention because of its potential to break through the inherent limitations of silicon-based electronics. Molecular wires, as the basic components of molecular electronics, are responsible for charge transfer and electronic communication between different components at the molecular level. They are currently a research hotspot in the field of multidisciplinary intersections, and organic molecular wires are an indispensable part of them. The conjugated structure directly affects the energy level structure, chemical stability and thermal stability of organic molecules, and also affects the photophysical properties, carrier transport properties and processing properties of optoelectronic devices, and has a decisive influence on the stability of the device. Therefore, the regulation of the conjugated structure is an indispensable and important link in the design of organic optoelectronic materials.

[0003] Molecular electronics has attracted extensive attention due to its potential to break through the inherent limitations of silicon-based electronics. Single-molecule wires are the basic elements of molecular electronics, responsible for charge transport and electronic communication between different components at the molecular level. In addition to the electrode-molecule interface, the internal electronic structure and geometry of the molecule play a decisive role in the overall performance of the molecular wire in the metal-molecule-metal junction. Therefore, exploring robust single-molecule wires with ideal conformations and unique electronic effects remains a huge challenge to achieve high and stable conductance. To date, the molecular cores of artificial single-molecule wires widely studied in the literature are mainly limited to rod-shaped organic molecules and organometallic molecules through bond π conjugation, in which a high density of delocalized π electrons facilitates charge transport through the molecular backbone. This through-bond conjugation usually refers to the direct connection of aliphatic and aromatic units with carbon-carbon single, double or triple bonds composed of sp, sp2 or sp3 carbon frameworks. Another type of interesting single-molecule wires that has just emerged is based on non-covalent spatial conjugation, in which the π electrons are spatially distributed in the interplanar regions of closely stacked aromatic rings and can be used for charge transport. When two chromophores or aromatic rings are arranged close enough and their electron density distributions overlap, through-space conjugation and long-range Coulomb (dipole-dipole) interactions are formed. This unique spatial conduction mode has attracted increasing attention and has shown important significance in various systems, including redox processes in biological complexes, electronic signaling in DNA molecules, carrier transport in organic electronics and photovoltaics, etc. However, compared with through-bond single-molecule wires, the exploration of through-space wires is far less, which may be due to the lack of suitable organic platforms with strong through-space conjugation.

[0004] Single-molecule junctions are a popular platform for studying molecular electronics. To this end, there have been numerous demonstrations of single-molecule electron transport properties. In order to count the molecular conductance that may occur in the junction at room temperature, one of the most widely used experimental techniques for studying single-molecule junctions is the scanning tunneling microscopy-broken junction (STM-BJ) method. In this method, the properties of single-molecule junctions are measured while increasing the electrode separation to promote the formation, evolution and rupture of the junction. Therefore, each measurement samples the progression of many different conformations. This method has been previously used for the covalent binding of rigid molecules to electrodes. It provides a platform to elucidate the properties of distance-dependent electronic interactions, such as van der Waals (vdW) forces. In order to be able to improve the conductivity of organic molecules and meet the requirements of industrial applications, the present invention provides conjugated organic molecules based on hexaphenylbenzene anchor groups with simultaneous valence conjugation and steric conjugation. Summary of the invention

[0005] In order to overcome the shortcomings and deficiencies of the above-mentioned prior art, the primary purpose of the present invention is to provide a spatially conjugated organic molecule based on a hexaphenylbenzene anchoring group and a preparation method thereof. The spatially conjugated organic molecule based on a hexaphenylbenzene anchoring group of the present invention has the characteristics of spatial conjugation and valence bond conjugation at the same time, has multiple conductive channels, one end of which is anchored by a coordination bond formed with a gold electrode through a mercaptomethyl group, and the other end of the hexaphenylbenzene is anchored with a gold electrode through a van der Waals force, which can effectively compensate for the low conductivity phenomenon caused by insufficient valence bond conjugation.

[0006] Another object of the present invention is to provide the application of the spatially conjugated organic molecules based on the hexaphenylbenzene anchoring group, and the application of the spatially conjugated organic molecules based on the hexaphenylbenzene anchoring group in the field of organic molecular wires.

[0007] The purpose of the present invention is achieved based on the following technical solutions:

[0008] A spatially conjugated organic molecule based on a hexaphenylbenzene anchoring group, the structure of which is shown in Formula I-III:

[0009]

[0010] To achieve the above object, the present invention provides the following technical solution: a preparation and application of a spatially conjugated organic molecule based on a hexaphenylbenzene anchoring group, wherein the preparation method comprises the following steps:

[0011] Add the compounds phenylacetylene, 4-bromothiylanisole, tetrakistriphenylphosphine palladium dichloride and cuprous iodide to a double-necked round-bottom flask. Evacuate the reaction flask under vacuum, replace it with dry nitrogen three times, then add triethylamine under a nitrogen atmosphere, reflux the reaction mixture for 24 hours, cool it to room temperature, pour the mixture into water, and extract it three times with dichloromethane. The combined organic layers are dried over anhydrous magnesium sulfate, filtered, and the solvent is evaporated under reduced pressure. The crude product is purified by silica gel column chromatography using petroleum ether: dichloromethane (4:1, v:v) as the eluent to obtain a white solid product, methyl (4-(phenylynyl)phenyl)sulfane. Mix methyl (4-(phenylynyl)phenyl)sulfane and tetraphenylcyclopentadienone in phenyl ether and add them to a single-necked round-bottom flask. The mixture is heated at 260 o C for 8 hours. After cooling to room temperature, the mixture was poured into water and extracted with dichloromethane three times. The combined organic layer was washed with saturated sodium bicarbonate and water in sequence, and then dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the crude product was purified by silica gel column chromatography using petroleum ether: dichloromethane (5: 1, v: v) as the eluent to obtain a white solid product ZL-01.

[0012] A spatial conjugated organic molecule based on a hexaphenylbenzene anchoring group synthesized by the present invention not only has a traditional valence bond conjugated structure, but also has a spatial conjugation effect. The molecular anchoring group with an intramolecular π-π stacking structure enables electrons to be transmitted not only along the valence bond conjugation channel, but also along the spatial conjugation channel, and has multiple conductance channels, which effectively compensates for the low conductivity phenomenon caused by insufficient valence bond conjugation of the molecule, and designs a new anchoring group hexaphenylbenzene, one end of which is anchored to the gold electrode through the van der Waals force of hexaphenylbenzene and the gold electrode, providing new insights for regulating the charge transfer performance of the single molecule wire. The spatial conjugated organic molecule of the present invention is easy to prepare and has excellent electrical conductivity, and is a building unit of a molecular wire with good prospects.

[0013] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0014] In addition to the electrode-molecule interface, the internal electronic structure and geometric structure of the molecule play a decisive role in the overall performance of the molecular wire in the metal-molecule-metal junction. Therefore, exploring a strong single-molecule wire with an ideal conformation and unique electronic effect is still a huge challenge to achieve high and stable conductivity. The traditional valence bond conjugated molecular wire of the through-bond transmission is affected by the reverse ring current and has poor molecular conductivity. The spatial conjugated organic molecule based on the hexaphenylbenzene anchoring group prepared in the present invention has the characteristics of valence bond conjugation and spatial conjugation, providing multiple conductive channels. The preparation method of the present invention has wide universality and greatly improves the conductivity of the single-molecule wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 (A) Normalized absorption spectra of ZL-01, ZL-02, and ZL-03 in THF solution (10 μM). (B) One-dimensional conductance plots of ZL-01, ZL-02, and ZL-03. Two-dimensional conductance-shift histograms of ZL-01 (C), ZL-02 (D), and ZL-03 (E). (F) Typical individual conductance-shift traces of ZL-01, ZL-02, and ZL-03.

[0016] Figure 2 Two-dimensional histograms of normalized flicker noise power and average conductance for ZL-01 (A), ZL-04 (B), and ZL-03 (C).

[0017] Figure 3 One-dimensional conductance histograms of ZL-01 (A), ZL-02 (B) and ZL-03 (C) under different deviations. Statistical conductance data of ZL-01, ZL-02 and ZL-03 under different applied deviations (D).

[0018] Figure 4 This is the single crystal structure and torsion angle information of ZL-01.

[0019] Figure 5 Illustration of the frontier molecular orbitals of HOMO-2, HOMO-1, HOMO, LUMO, LUMO+1 and LUMO+2 of ZL-01 determined at the M06-2X / 6-311G (d, p) theoretical level.

[0020] Figure 6 Diagram of the frontier molecular orbitals of HOMO-2, HOMO-1, HOMO, LUMO, LUMO+1 and LUMO+2 of ZL-02 determined at the M06-2X / 6-311G (d, p) theoretical level

[0021] Figure 7 Diagram of the frontier molecular orbitals of HOMO-2, HOMO-1, HOMO, LUMO, LUMO+1 and LUMO+2 of ZL-03 determined at the M06-2X / 6-311G (d, p) theoretical level

[0022] Figure 8 This is the high-resolution MALDI-TOF spectrum of ZL-01 [MALDI-TOF, m / z: 603.21 (Na) (Calcd580.22)].

[0023] Fig. 9This is the high-resolution MALDI-TOF spectrum of ZL-02 [MALDI-TOF, m / z: 695.21 (K) (Calcd656.25)].

[0024] Fig.10 This is the high-resolution MALDI-TOF spectrum of ZL-03 [MALDI-TOF, m / z: 719.21 (Na)(Calcd 680.91)]. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with examples and drawings, but the embodiments of the present invention are not limited thereto.

[0026] Example 1 Preparation of a novel spatial conjugated organic single-molecule wire [ZL-01] based on hexaphenylbenzene

[0027]

[0028] The synthetic route is as follows:

[0029]

[0030] (1) All chemicals and reagents were purchased from commercial sources and used without further purification. All reagents and drugs were sealed and not handled before use.

[0031] (2) Compounds phenylacetylene (0.74 g, 5.00 mmol), 4-bromothiylanisole (1.65 g, 5.00 mmol), tetrakistriphenylphosphine palladium dichloride (0.35 g, 0.50 mmol) and cuprous iodide (0.01 g, 0.50 mmol) were added to a 125 mL double-necked round-bottom flask. The reaction flask was evacuated under vacuum, flushed with dry nitrogen three times, and then 80 mL of triethylamine was added. The reaction mixture was refluxed for 24 hours. After cooling to room temperature, the mixture was poured into water and extracted with dichloromethane three times. The combined organic layers were dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the crude product was purified by silica gel column chromatography using petroleum ether: dichloromethane (4:1, v:v) as the eluent to obtain 1.02 g of white solid product 3 with a yield of 91%. 1 H NMR (500 MHz, CDCl3) δ 7.53 (d, J = 9.70 Hz, 2H), 7.45 (d, J = 8.50 Hz, 2H), 7.35 (t, J =7.95 Hz, 3H), 7.22-7.20 (d, J = 8.50 Hz, 2H), 2.50 (s, 3H). 13C NMR (125 MHz, CDCl3) δ 139.45, 132.01, 131.68, 128.49, 128.33, 126.02, 123.44, 119.70, 89.60, 89.33, 15.53.

[0032] (3) Intermediate product 3 (0.89 g, 4.00 mmol) and tetraphenylcyclopentadienone (1.15 g, 3.00 mmol) were mixed in 10 mL of phenyl ether and added to a 25 mL single-necked round-bottom flask. The mixture was heated at 260 o C for 8 hours. After cooling to room temperature, the mixture was poured into water and extracted with dichloromethane three times. The combined organic layer was washed with saturated sodium bicarbonate and water in sequence, and then dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the crude product was purified by silica gel column chromatography using petroleum ether: dichloromethane (5:1, v:v) as the eluent to obtain 1.07 g of a white solid with a yield of 62%. 1 H NMR (500 MHz,Methylene Chloride-d2) δ 6.89–6.85 (m, 25H), 6.81–6.78 (d, J = 10.50 Hz, 2H), 6.74-6.72 (d, J = 10.45 Hz, 2H), 2.29 (s, 3H). 13 C NMR (125 MHz, CDCl3) δ140.70, 140.49, 131.94, 131.53, 126.84, 126.71, 125.39, 125.32, 15.85. MALDI-TOF, m / z: 603.21 (Na) (Calcd 580.22).

[0033] Example 2 Preparation of a novel spatial conjugated organic single-molecule wire [ZL-02] based on hexaphenylbenzene

[0034]

[0035] The synthetic route is as follows:

[0036]

[0037] (1) Mix 4-bromotolane (1.00 g, 2.60 mmol) and tetraphenylcyclopentadienone (0.73 g, 2.86 mmol), add to 10 mL of phenyl ether, and place in a 25 mL single-necked round-bottom flask. oC for 8 hours. After cooling to room temperature, the mixture was poured into water and extracted with dichloromethane three times. The combined organic layer was washed with saturated sodium bicarbonate and water in sequence, and then dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the crude product was purified by silica gel column chromatography using petroleum ether: dichloromethane (5:1, v:v) as the eluent to obtain 1.46 g of white solid 6 in a yield of 92%. 1 H NMR (500 MHz, CDCl3) δ 6.98 (d, J = 8.25 Hz, 2H), 6.88–6.80 (m, 25H), 6.70 (d, J= 8.40 Hz, 2H). 13 C NMR (125 MHz, CDCl3) δ 140.80, 140.61, 140.56, 140.52,140.39, 140.32, 139.81, 139.07, 133.14, 131.46, 129.92, 126.95, 126.75,125.57, 125.40, 119.56.

[0038] (2) Compound 6 (1.00 g, 1.60 mmol), 4-(methylthio)phenylboronic acid (0.13 g, 0.80 mmol), tetrakis(triphenylphosphine)palladium (0.28 g, 0.25 mmol) and potassium carbonate (4.00 g, 3.20 mmol) were added to a 100 mL double-necked round-bottom flask. The reaction flask was evacuated under vacuum, flushed with dry nitrogen three times, and then 40 mL of a mixture of toluene, ethanol and water (6 / 1 / 1, v / v / v) was added. The reaction mixture was refluxed for 24 hours. After cooling to room temperature, the mixture was poured into water and extracted three times with dichloromethane. The combined organic layers were dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the crude product was purified by silica gel column chromatography using petroleum ether: dichloromethane (5:1, v:v) as the eluent to obtain 0.33 g of a white solid with a yield of 32%. 1 HNMR (500 MHz, CDCl3) δ 7.36 (d, J = 8.35 Hz, 2H), 7.22 (d, J = 8.45 Hz, 2H), 7.09 (d, J = 8.35 Hz, 2H), 6.87–6.84 (m, 27H), 2.47 (s, 3H). 13C NMR (125 MHz, CDCl3) δ 140.72, 140.52, 140.47, 140.00, 132.02, 131.56, 127.16, 127.04,126.81, 126.72, 125.37, 125.33, 124.91, 16.19. MALDI-TOF, m / z: 695.21 (K)(Calcd 656.25).

[0039] Example 3 Preparation of a novel spatially conjugated organic single-molecule wire [ZL-03] based on hexaphenylbenzene

[0040]

[0041] The synthetic route is as follows:

[0042]

[0043] (1) The synthesis of intermediate 4 is the same as that of Example 2.

[0044] (2) Compound 6 (1.00 g, 1.60 mmol), (4-ethynylbenzene)(methyl)pyridinium chloride (0.72 g, 3.80 mmol), bistriphenylphosphine palladium dichloride (0.11 g, 0.16 mmol) and cuprous iodide (0.02 g, 0.24 mmol) were added to a 250 mL two-necked round-bottom flask. The flask was evacuated under vacuum, flushed with dry nitrogen three times, and then 80 mL of triethylamine was added. The reaction mixture was refluxed for 24 hours. After cooling to room temperature, the mixture was poured into water and extracted three times with dichloromethane. The combined organic layers were dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the crude product was purified by silica gel column chromatography using petroleum ether: dichloromethane (4:1, v:v) as the eluent to obtain 0.25 g of a yellow solid with a yield of 23%. 1 H NMR (500 MHz, CDCl3) δ 7.33 (d, J = 8.15 Hz, 2H), 7.15 (d, J = 8.10 Hz, 2H), 7.02 (d, J =7.95 Hz, 2H), 6.86–6.83 (m, 27H), 2.47 (s, 3H). 13C NMR (125 MHz, CDCl3) δ140.66, 140.47, 140.33, 138.07, 131.87, 131.52, 130.12, 126.93, 126.76,125.94, 125.56, 125.40, 15.76. MALDI-TOF, m / z: 719.21 (Na) (Calcd 680.91).

[0045] Example 4 Determination of molecular conductance based on scanning tunneling microscopy-broken junction (STM-BJ) technology

[0046] Figure 1 A shows the optical properties of the molecules measured in dilute tetrahydrofuran (THF) solution. Compared with ZL-01, ZL-02 and ZL-03 showed red shift, which verified their longer valence bond conjugation. Figure 1 B is the one-dimensional conductivity diagram of ZL-01, ZL-02 and ZL-03 molecules, Figure 1 C~E are the two-dimensional conductivity diagrams of ZL-01, ZL-02 and ZL-03 molecules. From the one-dimensional conductivity diagram, we can see that the conductivity peak of ZL-01 is located at 10 -4.12 G0, ZL-02 conductivity peak is located at 10 -4.58 G0, ZL-03 conductivity peak is located at 10 -3.66 G0. It can be seen from the figure that there are obvious intensity clouds in the two-dimensional images of the three molecules, indicating that in most of the splitting processes, molecular junctions are formed as the gold electrode breaks and stretches. Figure 1 F is a single conductivity-distance curve measured by randomly selecting ZL-01, ZL-02 and ZL-03, all of which have obvious conductivity steps.

[0047] Example 5 Flicker Noise Analysis

[0048] Figure 2 A, B and C are the two-dimensional noise-conductance intensity statistics of ZL-01, ZL-02 and ZL-03 molecules respectively. According to previous reports, the proportionality factor of noise power G 1.0 indicates full through-bond transmission, while G 2.0 It indicates through-space transmission. From the figure, we can see that the noise power proportional factors of ZL-01, ZL-02 and ZL-03 molecules are G 1.6 , G 1.3 and G 1.0 , the noise power of ZL-01, ZL-02 and ZL-03 reveals the existence of high spatial conjugation, and spatial conjugation plays a vital role in charge transport.

[0049] Example 6 Bias voltage regulation of conductivity

[0050] We performed STM-BJ experiments at room temperature with a bias voltage between the substrate and the gold tip and collected thousands of conductance traces of ZL-01, ZL-02, and ZL-03 to construct 1D and 2D histograms from 0.1 V to 0.4 V. Figure 3 As shown in Figures AD, the molecular conductance of ZL-01, ZL-02, and ZL-03 decreases with increasing bias voltage, while the conductance of OPE2 remains unchanged. The conductance peak of ZL-03 is about 10 -3.66 G0, at 0.4 V this value drops to 10 -3.95 G0. The switching factor can be defined as the ratio of the highest conductance state to the lowest conductance state. Therefore, the switching ratios of ZL-01, ZL-02 and ZL-03 between the two bias voltages reach 12.90, 1.80 and 3.80.

[0051] Example 7 ZL-01 molecular crystal structure analysis

[0052] Single crystals of ZL-01 were grown in a dichloromethane-petroleum ether mixture by slow solvent evaporation and analyzed by X-ray crystallography. Figure 4 As shown, the six ring-shaped phenyl groups around the central benzene exhibit a face-to-face configuration with a dihedral angle of 62.23 o - 70.47 o range, indicating that ZL-01 has an obviously distorted annular space conjugation within the molecular framework.

[0053] Example 8 Molecular Energy Level Orbital Analysis of ZL-01, ZL-02 and ZL-03

[0054] To reveal the nature of the valence bond conformation and charge transport of the electrode molecules based on sterically conjugated hexaphenylbenzene, theoretical simulations including density functional theory using Gaussian 16 and Transiesta function of Siesta software were employed. Figure 5 - Figure 7 As shown, the electron distribution between the peripheral benzene rings dominates the frontier orbitals, and the molecular orbitals are distributed over the entire molecular skeleton, indicating a more efficient charge transfer via spatial conjugation.

[0055] The above data show that the present invention synthesized a series of novel spatially conjugated organic molecules based on hexaphenylbenzene anchoring groups and applied them to organic single-molecule wires. This type of organic molecule not only has a valence bond conjugated structure, but also has a spatial conjugated structure. The transmission channels of these two types of carriers work synergistically, thereby obtaining an organic single-molecule wire with good electrical conductivity and simple molecular structure.

[0056] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that modifications may be made to the exemplary embodiments, and other arrangements may be designed without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A class of spatially conjugated organic molecules based on hexaphenylbenzene anchoring groups, whose characteristic structure As shown below I-III: .

2. The spatially conjugated organic molecule based on the hexaphenylbenzene anchoring group according to claim 1, characterized in that: The spatially conjugated organic molecule based on the hexaphenylbenzene anchoring group of the present invention constructs a stable multi-transmission channel single-molecule device containing the hexaphenylbenzene anchoring group, has the characteristics of spatial conjugation and valence bond conjugation, and has multiple transmission channels.

3. According to the application of the spatially conjugated organic molecules based on the hexaphenylbenzene anchoring group in organic single-molecule wires according to claims 1-2, an Au-S-π bridge-hexaphenylbenzene-Au single-molecule wire constructed using STM-BJ technology.

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