Method for preparing one-dimensional polymer by utilizing strategy of activating saturated carbon-hydrogen bonds in adjacent methylene by cyano groups

Abstract

The invention discloses a method for preparing a one-dimensional polymer by using a strategy of activating saturated carbon-hydrogen bonds in adjacent methylene by using cyano groups. In the preparation method, a gold single crystal substrate is selected as a substrate, precursor molecules with acetonitrile groups are deposited on the surface of the gold single crystal substrate through a molecular beam epitaxy growth technology to obtain a self-assembled sample, and then the self-assembled sample is gradually annealed to induce dehydrogenation polymerization reaction between the molecules, so that the electrochemical sensor is obtained. Therefore, an atomic-scale precise one-dimensional polymer is obtained. The method provides a brand-new high-selectivity surface dehydrogenation coupling reaction, and has high scientific research value and wide application potential.

Description

Technical Field

[0001] The invention belongs to the field of surface synthesis, and in particular relates to a method for preparing a one-dimensional polymer by utilizing a cyano group to activate a saturated carbon-hydrogen bond in an adjacent methylene group. Background Art

[0002] In recent years, the construction of covalently bonded nanostructures through surface synthesis has become a hot topic in surface science. Most surface in-situ chemistry is done on the surface of metal single crystals, through traditional chemical reactions, to prepare stable zero-dimensional, one-dimensional linear and two-dimensional network structure macromolecules and polymers.

[0003] The C–H bond is one of the most basic chemical bonds and exists in almost all organic compounds. The most ideal strategy for synthesizing organic molecular structures is in principle through C–H bond activation. The main reason for this is that the byproducts generated contain only non-polluting hydrogen. The selective activation of C–H bonds has great application potential in the refining and processing of petroleum products, the synthesis of special nanostructures, and the post-modification of biopharmaceuticals. However, due to the high dissociation enthalpy of the C–H bond and the presence of multiple equivalent C–H reaction sites in organic molecules, achieving selective activation of C–H bonds is one of the most challenging topics both in solution chemistry and in-situ surface chemistry. Summary of the invention

[0004] In view of the difficulties and challenges of activating the C–H bond, the present invention proposes a method for preparing a one-dimensional polymer by using a cyano group to activate a saturated carbon-hydrogen bond in a neighboring methylene group. Specifically, the present invention uses a strategy that a precursor molecule DCEP with two acetonitrile functional groups will undergo dehydrogenation coupling under the catalysis of a gold substrate, deposits the precursor molecule DCEP on the surface of a gold substrate, and anneals at 250°C for 20 minutes. The sample is then cooled to room temperature, and finally a high-quality one-dimensional polymer is obtained.

[0005] A method for preparing a one-dimensional polymer by using a cyano group to activate a saturated carbon-hydrogen bond in an adjacent methylene group, the specific steps of which include:

[0006] Step 1, preparing a gold single crystal substrate;

[0007] Step 2, depositing the precursor molecule DCEP synthesized in step 1 onto a gold single crystal substrate maintained at room temperature by molecular beam epitaxy technology;

[0008] Step 3, heating the sample to 250°C and keeping it warm for 10-20 minutes;

[0009] The preparation process of the gold single crystal substrate is specifically as follows:

[0010] Step 1.1, in an ultra-high vacuum chamber, subjecting a gold substrate to argon ion sputtering to obtain a gold base;

[0011] Step 1.2: Heat the gold substrate obtained in step 1.1 to 450°C and keep it warm for 10-30 minutes to obtain a gold single crystal substrate.

[0012] In step 2, the evaporation temperature of the precursor molecule DCEP is 160° C., and the deposition time is 2 minutes.

[0013] In step 3, the growth temperature is 250° C. and the temperature is kept at this temperature for 20 minutes.

[0014] The deposition time of the above-mentioned precursor molecule DCEP determines the coverage of the final one-dimensional polymer. The deposition time should not exceed 10 minutes when the evaporation temperature is 160°C.

[0015] The beneficial effects of the present invention are:

[0016] (1) The present invention can prepare a regular and orderly one-dimensional polymer bridged by succinonitrile;

[0017] (3) The present invention proposes a highly selective surface dehydrogenation polymerization reaction; BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a reaction pathway diagram proposed in an embodiment of the present invention;

[0019] Figure 2 This is a scanning tunneling microscope image of the self-assembly of the precursor molecule DCEP of the embodiment of the present invention (and a one-dimensional polymer image of the prepared succinonitrile bridge;

[0020] Figure 3 It is a scanning tunneling microscope image of lateral needle tip manipulation of one-dimensional polymer according to an embodiment of the present invention.

[0021] Figure 4 This is the electrical property characterization of the one-dimensional polymer by the embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods.

[0023] Test instruments and equipment:

[0024] Low-temperature scanning tunneling microscope: purchased from Omicron, Germany.

[0025] K-cell molecular evaporation source: purchased from Omicron, Germany.

[0026] Argon ion gun: purchased from Omicron, Germany.

[0027] raw material:

[0028] Precursor molecule DCEP: chemical solution synthesis, purity 95%.

[0029] Gold single crystal: purchased from MaTecK, purity 99.999%.

[0030] Example

[0031] The method for constructing a one-dimensional polymer by using a cyano group to activate a carbon-hydrogen bond in an adjacent methylene group comprises the following specific steps:

[0032] Step 1: preparing a gold single crystal substrate; the preparation process of the gold single crystal substrate is specifically as follows:

[0033] Step 1.1, in an ultra-high vacuum chamber, subjecting a gold substrate to argon ion sputtering to obtain a gold base;

[0034] Step 1.2, heating the gold substrate obtained in step 1.1 to 450° C. and keeping the temperature for 10 minutes to obtain a gold single crystal substrate;

[0035] Step 2, 2 mg of precursor molecule DCEP is evaporated at 160° C. using a thermal resistance K-cell molecular evaporation source and deposited on the 50 g gold single crystal substrate in step 1 to obtain a substrate and a DCEP self-assembled structure deposited on the substrate. The temperature of the gold single crystal substrate is controlled to be 25° C. during the deposition process, and the deposition time is 2 minutes;

[0036] Step 3, annealing the DCEP molecules on the substrate in step 2 to the reaction temperature and performing heat preservation treatment; the growth temperature is 250°C and the temperature is kept for 20 minutes;

[0037] The dehydrogenation polymerization reaction pathway proposed in this embodiment is as follows Figure 1 As shown, it can be seen that the intermolecular methylene dehydrogenation coupling forms a one-dimensional polymer.

[0038] Self-assembled structure of DCEP precursor molecules prepared in this example Figure 2 (a) shows that DCEP molecules tend to adsorb on the face-centered cubic region of the gold single crystal substrate. High-resolution scanning tunneling microscopy image Figure 2 (b) Non-contact atomic force microscopy Figure 2 (c) shows the highlighting feature of methylene in the precursor molecule DCEP. Figure 2 (d) shows that after annealing at 250°C, the self-assembled structure transforms into a one-dimensional polymer chain. The chemical structure of the one-dimensional polymer and the high-definition scanning tunneling microscope Figure 2 (e) and bond-resolved scanning tunneling microscopy Figure 2 (f) is in good agreement. Non-contact atomic force microscopy of one-dimensional polymers Figure 2In (g), the sites can be connected to form new carbon-carbon bonds, and they show a highlight feature, which is mainly caused by the stereo configuration caused by the carbon-carbon single bond. The corresponding Laplace filter Figure 2 (h) Further reveals the structural characteristics of the one-dimensional polymer.

[0039] In this example, a one-dimensional polymer system was prepared by using a cyano group to activate the carbon-hydrogen bond in the adjacent methylene group. Figure 3 As shown, from Figure 3 It can be directly and effectively proved that one-dimensional polymers are connected by covalent bonds.

[0040] Figure 4 The electrical property characterization of the one-dimensional polymer prepared according to the preparation method of the embodiment of the present invention is shown. The first-order differential spectrum shows that the electronic structure of adjacent connection points of the one-dimensional polymer is the same, and the electronic state density distribution also proves that the wave function distribution of its connection site is the same.

Claims

1. A method for preparing a one-dimensional polymer by using a cyano group to activate a saturated carbon-hydrogen bond in an adjacent methylene group, characterized in that The specific steps include: Step 1, preparing a gold single crystal substrate; Step 2, depositing the precursor molecule DCEP synthesized in step 1 onto a gold single crystal substrate maintained at room temperature by molecular beam epitaxy technology; Step 3: Heat the sample to 250°C and keep it warm for 10-20 minutes.

2. The method for preparing a one-dimensional polymer by utilizing a cyano group to activate a saturated carbon-hydrogen bond in an adjacent methylene group according to claim 1, characterized in that: The preparation process of the gold single crystal substrate is specifically as follows: Step 1.1, in an ultra-high vacuum chamber, subjecting a gold substrate to argon ion sputtering to obtain a gold base; Step 1.2: Heat the gold substrate obtained in step 1.1 to 450°C and keep it warm for 10-30 minutes to obtain a gold single crystal substrate.

3. The method for preparing a one-dimensional polymer by utilizing a cyano group to activate a saturated carbon-hydrogen bond in an adjacent methylene group according to claim 1, characterized in that: In step 2, the evaporation temperature of the precursor molecule DCEP is 160° C., and the deposition time is 2 minutes.

4. The method for preparing a one-dimensional polymer by utilizing a cyano group to activate a saturated carbon-hydrogen bond in an adjacent methylene group according to claim 1, characterized in that: In step 3, the growth temperature is 230-250° C. and the temperature is kept at this temperature for 20 minutes.

Images