A spatially conjugated organic molecule based on naphthalene skeleton and its preparation and application

Abstract

The present invention belongs to the technical field of organic electronics, and discloses a method for preparing a class of spatially conjugated organic molecules based on a naphthalene skeleton and their application in the field of organic optoelectronics. The spatially conjugated organic molecules based on a naphthalene skeleton of the present invention have the following structure shown in I-III: Its unique spatial conjugated 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 conductance phenomenon caused by insufficient valence bond conjugation of meta-modified molecules. The preparation method of the present invention is simple and applicable, and has good application prospects in the field of organic optoelectronics.

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 a naphthalene skeleton 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] Traditional single-molecule wires are generally constructed based on linear π-conjugated skeletons, such as oligostyrene and oligothiophene, in which highly delocalized π electrons are conducive to charge transfer in the molecular skeleton. However, compared with linear molecules modified at the para position, the conductivity of molecules modified at the meta position will be greatly reduced, and it is far from meeting the requirements of industrialization. Single-molecule wires based on spatial conjugation are also an important type of research. Spatial conjugation is essentially the orbital coupling between two adjacent group π orbitals (or σ, n orbitals, etc.) through weak interactions such as electrostatic interactions and van der Waals interactions. This unique cross-space conduction mode has attracted more and more interest and has shown important significance in various systems, including redox processes in biological complexes, electronic signal transmission in DNA molecules, and carrier transport in organic electronics and optoelectronics.

[0004] In order to improve the conductivity of organic molecules and meet the requirements of industrial applications, the present invention provides a conjugated organic molecule based on a naphthalene skeleton that has both valence bond conjugation and spatial conjugation, which can not only significantly improve the molecular conductivity, but also effectively compensate for the low conductivity phenomenon caused by the low degree of valence bond conjugation of the molecular skeleton. 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 naphthalene skeleton and a preparation method thereof. The spatially conjugated organic molecule based on a naphthalene skeleton of the present invention has the characteristics of spatial conjugation and valence bond conjugation at the same time, has multiple conductive channels, and 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 naphthalene skeleton, and the application of the spatially conjugated organic molecules based on the naphthalene skeleton 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 naphthalene skeleton, the structure of which is shown in Formula I-III:

[0009]

[0010] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a preparation method and application of a spatial conjugated organic molecule based on a naphthalene skeleton, wherein the preparation method comprises the following steps: adding 4-bromoanisole, triphenylphosphine dichloropalladium and cuprous iodide into a double-necked round-bottom flask; evacuating and exchanging air three times, injecting trimethylsilylene under a nitrogen atmosphere, injecting triethylamine under nitrogen protection, and reflux reaction; after cooling to room temperature, purifying the crude product by column chromatography, putting it into a round-bottom flask containing potassium carbonate and methanol, stirring at room temperature, pouring the product into water, and extracting it three times with dichloromethane to obtain (4-ethylphenyl)(methyl)sulfonamide; adding 1,8-dibromonaphthalene, (4-ethylphenyl)(methyl)sulfonamide, triphenylphosphine dichloropalladium and cuprous iodide into a double-necked round-bottom flask, evacuating and exchanging air three times, cooling to room temperature under nitrogen protection, and reflux overnight; the obtained crude product is purified by a silica gel column using petroleum ether and dichloromethane as eluents to separate the product o-Naph.

[0011] A spatial conjugated organic molecule based on a naphthalene skeleton synthesized by the present invention not only has a traditional valence bond conjugated structure, but also has a spatial conjugation effect. The molecular skeleton 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, effectively compensating for the low conductance phenomenon caused by insufficient valence bond conjugation of the molecule. The spatial conjugated organic molecule of the present invention is easy to prepare, has excellent conductive properties, and is a building block of a molecular wire with good prospects.

[0012] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0013] The traditional valence bond conjugated molecular wires with meta-modified molecular skeletons are affected by the reverse ring current and have poor molecular conductivity. The spatially conjugated organic molecules based on the naphthalene skeleton prepared in the present invention have the characteristics of valence bond conjugation and spatial conjugation, and provide multiple conductive channels. The preparation method of the present invention has wide universality and greatly improves the conductivity of the molecular skeleton. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1(A) Molecular configurations of o-Naph, m-Naph, and p-Naph. (B) Circuit representation of p-Naph anchored on a gold electrode.

[0015] Figure 2 (A) is the optimized molecular structure of o-Naph. (B) is the frontier molecular orbital of o-Naph molecule. (C) is the absorption spectrum of o-Naph, m-Naph and p-Naph in THF solution. (D) is the distance-conductivity curve of o-Naph, m-Naph and p-Naph in STM.

[0016] Figure 3 One-dimensional conductivity diagrams of A) o-Naph, B) m-Naph, and C) p-Naph in solution; distance-conductance curves of D) o-Naph, E) m-Naph, and F) p-Naph in solution; the illustrations in Figures D-F are the step lengths of the three molecules.

[0017] Figure 4 A)o-Naph (proportional factor is G 1.6 ), B) m-Naph (proportional factor is G 1.3 ) and C) p-Naph (with a scaling factor of G 1.0 ) two-dimensional statistical graph of noise-conductance; D) transmission spectra of o-Naph, m-Naph and p-Naph.

[0018] Figure 5 Schematic diagram of the transmission path of o-Naph, m-Naph and p-Naph. DETAILED DESCRIPTION

[0019] 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.

[0020] Example 1 Preparation of a novel spatially conjugated organic single-molecule wire [o-Naph] based on naphthalene

[0021]

[0022] The synthetic route is as follows:

[0023]

[0024] (1) Compounds 4-bromothioanisole, trimethylsilylene, 1,8-dibromonaphthalene, 1,5-dibromonaphthalene, and 1,4-dibromonaphthalene were purchased from Energy Chemical (Shanghai). All reagents and drugs were sealed and not processed before use. All other chemicals and reagents were purchased from commercial channels and used without further purification.

[0025] (2) 4-bromothioanisole 1 (2.3 g, 10 mmol), triphenylphosphine dichloropalladium (0.7 g, 1 mmol) and cuprous iodide (0.19 g, 1 mmol) were added to a 250 ml double-necked round-bottom flask. The flask was evacuated three times and 4.5 mL of trimethylsilylene 2 (30 mmol) was injected under nitrogen atmosphere. 150 ml of triethylamine was injected under nitrogen protection and the reaction was refluxed for 12 h. After cooling to room temperature, the crude product was purified by column chromatography.

[0026] (3) The intermediate product 3 (1.89 g, 8.6 mmol) was placed in a 250 ml round-bottom flask containing potassium carbonate (0.55 g, 4 mmol) and 100 ml of methanol and stirred at room temperature for 6 hours. The product was poured into water and extracted three times with dichloromethane to obtain a yellow oily product 4 with a yield of 97% (1.23 g).

[0027] (4) 1,8-Dibromonaphthalene 5 (280 mg, 1 mmol), (4-ethylphenyl)(methyl)sulfonamide 4 (450 mg, 3 mmol), triphenylphosphine dichloropalladium (35 mg, 0.05 mmol) and cuprous iodide (20 mg, 0.1 mmol) were added to a 125 ml two-necked round-bottom flask. The mixture was evacuated three times and cooled to room temperature under nitrogen protection. The mixture was refluxed for 24 hours and the crude product was purified by silica gel column using petroleum ether and dichloromethane as eluents (v / v=6 / 1) to isolate o-Naph as a yellow solid (0.186 mg) with a yield of 44%. 1 H NMR (500MHz, CDCl3), δ (ppm): 7.86 (d, J = 15.2Hz, 4H), 7.25 (d, J = 8.50Hz, 4H), 7 .49(d,J=7.5Hz,2H),7.25(t,J=8.3Hz,4H),7.01(d,J=8.3Hz,4H),2.48(s,6H). 13 CNMR(125MHz, CDCl3)δ138.78,134.70,134.14,131.78,129.58,125.58,125.42,120.83,120.09,96.39,89.84,15.39.HRMS(C 28 H 20 S2):m / z 420.59[M + ,calcd 420.10].

[0028] Example 2 Preparation of a novel spatially conjugated organic single-molecule wire [m-Naph] based on naphthalene

[0029]

[0030] The synthetic route is as follows:

[0031]

[0032] (1) The synthesis of intermediate (4-ethylphenyl)(methyl)sulfonamide 4 was the same as in Example 1.

[0033] (2) 1,5-Dibromonaphthalene 6 (280 mg, 1 mmol), (4-ethylphenyl)(methyl)sulfonamide 4 (450 mg, 3 mmol), triphenylphosphine dichloropalladium (35 mg, 0.05 mmol) and cuprous iodide (20 mg, 0.1 mmol) were added to a 125 ml two-necked round-bottom flask. The mixture was evacuated three times and cooled to room temperature under nitrogen protection. The mixture was refluxed for 24 hours and the crude product was purified by silica gel column using petroleum ether and dichloromethane as eluents (v / v=6 / 1). 0.189 g of white solid m-Naph was isolated, and the isolation rate was 44%. 1 H NMR (500MHz, CDCl3), δ (ppm): 8.45 (d, J = 8.4Hz, 2H), 8.27 (d, J = 7.35Hz, 2H), 7.84-7.79 (m, 4H), 7.58-7.54 (m, 6H), 7.43 (t, J = 8.7Hz, 2H), 2.55 (s, 6H). 13 C NMR (125MHz, CDCl3) δ139.86,134.47,131.92,131.86,131.05,130.59,131.38,127.78 ,126.95,126.68,126.30,125.91,123.24,121.59,119.31,94.72,87.13,15.38.HRMS(C 28 H 20 S2):m / z 420.59[M + ,calcd 420.10]. Example 3 Preparation of a novel spatially conjugated organic single-molecule wire based on naphthalene [p-Naph]

[0034]

[0035] The synthetic route is as follows:

[0036]

[0037] (1) The synthesis of intermediate (4-ethylphenyl)(methyl)sulfonamide 4 was the same as in Example 1.

[0038] (2) 1,4-dibromonaphthalene 7 (280 mg, 1 mmol), (4-ethylphenyl)(methyl)sulfane 4 (450 mg, 3 mmol), triphenylphosphine dichloropalladium (35 mg, 0.05 mmol) and cuprous iodide (20 mg, 0.1 mmol) were added to a 125 ml two-necked round-bottom flask. The mixture was evacuated three times, cooled to room temperature under nitrogen protection, refluxed for 24 hours, and the crude product was purified by silica gel column using petroleum ether and dichloromethane as eluents (v / v=6 / 1) to obtain 0.187 g of p-Naph as a white solid with a separation rate of 44%. 1 H NMR (500MHz, CDCl3), δ (ppm): 8.47 (d, J = 9.1Hz, 2H), 7.71 (d, J = 8.56Hz, 2H), 7. 67(t,J=3.1Hz,2H),7.58(d,J=8.3Hz,4H),7.28(d,J=4.45Hz,4H),2.55(s,6H). 13 C NMR (125MHz, CDCl3) δ139.82,133.01,131.94,129.61,127.22,126.63,125.91,121.45,119.42,95.86,87.69,15.37.HRMS(C 42 H 32 S3):m / z 420.59[M + ,calcd 420.10].

[0039] Example 4 Determination of molecular conductance based on STM-BJ technology

[0040] Figure 1 A is three molecules prepared according to the synthetic routes shown in Examples 1 to 3, Figure 1 B is the optimized p-Naph molecular device structure.

[0041] Example 5 o-Naph molecular structure and frontier orbital analysis

[0042] Figure 2 A is the optimized o-Naph molecular structure, in which the distance between the two nearest carbon atoms is than the typical π-π interaction distance short. Figure 2 B is the frontier orbital of the o-Naph molecule, because the molecule anchored by mercaptomethyl is dominated by HOMO, HOMO-1 is close to the Fermi level of gold -5.20 eV, and the electron cloud is localized on the side chain, indicating the existence of poor valence bond conjugation. Figure 2C is the optical properties of the molecules measured in dilute tetrahydrofuran (THF) solution. Compared with the control molecule p-Naph, o-Naph and m-Naph underwent a blue shift, verifying their poor valence bond conjugation. Figure 2 D is a single conductivity-distance curve measured by randomly selecting o-Naph, m-Naph, and p-Naph, all of which have obvious conductivity steps.

[0043] Example 6 Single molecule conductance test

[0044] Figure 3 A~C are the one-dimensional conductivity diagrams of o-Naph, m-Naph and p-Naph molecules, and 1D~F are the two-dimensional conductivity diagrams and step length distribution diagrams of o-Naph, m-Naph and p-Naph molecules. It can be seen from the figure that there are obvious intensity clouds in the two-dimensional diagrams of the three molecules, indicating that molecular junctions are formed during most of the splitting process as the gold electrode breaks and stretches. From the step length distribution diagram, it can be found that the lengths of the three molecular junctions are 0.34nm, 1.45nm and 1.42nm, respectively. Considering that the gold electrode has a 0.5nm rebound during the stretching process, the lengths of the molecular junctions after addition are 0.84nm, 1.95nm and 1.92nm, respectively, which are consistent with the distance between the two sulfur atoms, proving that the molecular junction is formed by the connection between the sulfur atom on the mercaptomethyl group and the gold electrode, and the measured conductivity data is reliable. It can be seen from the one-dimensional conductivity diagram that the conductivity peak of o-Naph is located at 10 -4.7 G0, m-Naph conductivity peak is located at 10 -4.9 G0, p-Naph conductivity peak is located at 10 -3.7 G0.

[0045] Example 7 Flicker Noise Analysis and Theoretical Calculation

[0046] Figure 4 A, B and C are the two-dimensional noise-conductance intensity statistics of o-Naph, m-Naph and p-Naph 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 o-Naph, m-Naph and p-Naph molecules are G 1.6 , G 1.3 and G 1.0 , the noise power of o-Naph reveals that it has high spatial conjugation, and spatial conjugation plays a crucial role in charge transport. Figure 4 D is the transmission spectrum of the three molecules. It can be seen from the figure that the conductivity is arranged from large to small as p-Naph>o-Naph>m-Naph, which is consistent with the conductivity actually measured in Example 6.

[0047] Example 8 Transmission Path Calculation

[0048] Figure 5 A, B, and C are the transmission paths of o-Naph, m-Naph, and p-Naph calculated based on the transmission spectra, respectively. The blue arrow indicates that the electron moves from the left electrode to the right electrode, and the red arrow indicates that the electron moves from the right electrode to the left electrode. In p-Naph, after the electron is injected into the molecule from the left electrode, the transmission path on the benzene ring connected to the electrode through -SMe is mainly a valence bond conjugation channel. In m-Naph, its main transmission pathway is a through-bond conduction channel along the phenyl chain with an anchoring group, but a few electrons in the central region move in the opposite direction, resulting in lower conductivity. There is a strong Au-π interaction between the o-Naph molecule and the electrode, so in the process of electron injection from the electrode to the molecule, the electron can be directly injected into the molecule through space without passing through chemical bonds. More importantly, there are obvious cross-space transmission channels on the two side chains, which is consistent with its spatial conjugation characteristics. The existence of spatial conjugation characteristics compensates for the low conductivity caused by insufficient valence bond conjugation, so the conductivity of o-Naph is higher than that of m-Naph.

[0049] The above data show that the present invention synthesized a series of novel spatially conjugated organic molecules based on naphthalene skeletons 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.

[0050] 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 the exemplary embodiments may be modified 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 the naphthalene skeleton, whose characteristic structure As shown below I-III: 。 2. Application of the spatially conjugated organic molecules based on the naphthalene skeleton according to claim 1 in organic single-molecule wires.

3. According to claim 2, the application of the spatially conjugated organic molecules based on the naphthalene skeleton in the organic single-molecule wire, the Au-S-π bridge-S-Au single-molecule wire constructed by STM-BJ technology.

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