CN120172904A - A complex monomer, a ternary memristive metal polymer and a preparation method thereof - Google Patents

Abstract

Translated fromChinese

一种配合物单体、三元忆阻金属配位聚合物及其制备方法，涉及功能材料技术领域，解决了现有二元忆阻金属配位聚合物信息存储密度低以及富含金属单元的金属聚合物溶解度低的问题。本发明将三联吡啶配体与二价钴盐在溶剂中发生配位反应，得到钴^II配合物；随后将可溶性银盐与得到的钴^II配合物在溶剂中发生氧化反应，制备得到钴^III配合物单体；将配合物单体溶解于含有支持电解质的溶液中，随后放入工作电极、对电极和参比电极，进行电化学氧化聚合，实现原位沉积，制备得到钴^III配位聚合物薄膜。利用钴^III配位聚合物的金属中心和配体在不同偏压下的氧化还原特性，实现了三个电阻状态的可逆切换。

A complex monomer, a ternary memristive metal coordination polymer and a preparation method thereof, relate to the technical field of functional materials, and solve the problems of low information storage density of existing binary memristive metal coordination polymers and low solubility of metal polymers rich in metal units. The present invention causes a terpyridine ligand to undergo a coordination reaction with a divalent cobalt salt in a solvent to obtain a cobalt^II complex; then an oxidation reaction is carried out between a soluble silver salt and the obtained cobalt^II complex in a solvent to prepare a cobalt^III complex monomer; the complex monomer is dissolved in a solution containing a supporting electrolyte, and then a working electrode, a counter electrode and a reference electrode are placed therein to perform electrochemical oxidation polymerization, achieve in-situ deposition, and prepare a cobalt^III coordination polymer film. The redox characteristics of the metal center and ligand of the cobalt^III coordination polymer under different bias voltages are utilized to achieve reversible switching of three resistance states.

Description

Complex monomer, ternary memristive metal polymer and preparation method of ternary memristive metal polymer

Technical Field

The invention relates to the technical field of functional materials, in particular to a complex monomer, a ternary memristive metal polymer and a preparation method thereof.

Background

In the present information age, with the miniaturization, high performance, and rapid increase in demand for data storage and processing capabilities of electronic devices, the development of new electronic materials is a key to the advancement of electronic technology. Memristors, as a novel electronic element with unique resistance memory effect, have great application potential in the fields of information storage, neuromorphic calculation and the like. The memristor material can realize resistance change based on redox reaction, charge transfer, conformational change and other mechanisms when certain external bias voltage is applied, and can still retain stored data after power failure by virtue of the unique resistance memory characteristic, so that reliable storage of the data is realized.

The metal polymer is a functional polymer material containing metal complex on main chain or side group. Such materials can coordinate with organic ligands (e.g., carboxylic acids, alcohols, amines, pyridines, etc.) by selecting different metal ions (e.g., transition metals or rare earth metals), thereby forming polymer systems with complex and diverse structures and rich redox states, which makes metal polymers exhibit great potential in memristive applications. However, the metal polymers used for memristive applications are usually binary memristors (only comprise two resistance states), high-density storage is difficult to realize in data storage applications, and moreover, the intermolecular forces of the metal polymers rich in metal units are strong, so that the solubility of the metal polymers in common organic solvents such as ethanol and acetone is extremely low, uniform and stable solutions are difficult to form, and film formation is difficult to be carried out by a solution method after polymerization.

In order to meet urgent requirements of the electronic information field on high-performance memristor materials, the development of novel metal polymers with multi-element memristor characteristics and an efficient and large-scale preparation method have important practical significance.

Disclosure of Invention

The invention provides a complex monomer, a ternary memristor metal polymer and a preparation method thereof, and aims to solve the problems of low information storage density and low solubility of the metal polymer rich in metal units of the conventional binary memristor metal polymer. The technical scheme of the invention is as follows:

a complex monomer has a structural formula shown in a formula (I):

the preparation method of the complex monomer comprises the following steps:

Carrying out coordination reaction on terpyridine ligand and bivalent cobalt salt in a solvent to obtain a cobalt^II complex, carrying out oxidation reaction on soluble silver salt and the obtained cobalt^II complex in the solvent, removing precipitate after the reaction is finished, washing the precipitate until filtrate is colorless, concentrating the filtrate, continuously adding saturated potassium hexafluorophosphate aqueous solution to precipitate a product, filtering, washing the precipitate to obtain a crude product, and purifying the crude product to obtain a cobalt^III complex monomer with a structure shown in a formula (I);

further, the structural formula of the terpyridine ligand is shown as a formula (II):

Further, the molar ratio of the terpyridine ligand to the divalent cobalt salt is 2-2.5:1, and the molar ratio of the soluble silver salt to the cobalt^II complex is 3-8:1;

further, the divalent cobalt salt is any one of cobalt dichloride, cobalt nitrate, cobalt perchlorate or cobalt tetrafluoroborate;

further, the soluble silver salt is any one of silver nitrate, silver hexafluorophosphate, silver tetrafluoroborate or silver trifluoromethane sulfonate;

further, the solvent is any one of methanol, ethanol, glycol or acetonitrile;

Further, the coordination reaction time is 5-30 min, and the oxidation reaction time is 3-10 min.

A ternary memristive metal polymer has a structural formula shown in a formula (III):

the preparation method of the ternary memristive metal polymer comprises the following steps:

dissolving cobalt^III complex monomer in a solution containing supporting electrolyte, then placing the solution into a working electrode, a counter electrode and a reference electrode, and performing electrochemical oxidative polymerization to realize in-situ deposition to prepare a cobalt^III -containing polymer film;

further, the supporting electrolyte is composed of anions and cations, wherein the anions are any one of tetrafluoroborate ion, tetraphenylborate ion, hexafluorophosphate ion, hexafluoroarsenate ion or perchlorate ion, the cations are tetraalkylammonium ion, and the alkyl is any one of methyl, ethyl, propyl or butyl;

further, the solvent in the solution is any one or at least two of acetonitrile, ethanol, methanol, methylene dichloride, chloroform or tetrahydrofuran;

further, the working electrode and the counter electrode are any one of an inert metal electrode, a semiconductor electrode or a carbon material;

further, the inert metal electrode is platinum, gold, silver or titanium;

further, the semiconductor electrode is indium tin oxide, fluorine-doped tin oxide or titanium dioxide;

further, the carbon material electrode comprises graphene, and the reference electrode is a silver-silver ion electrode;

Further, the electrochemical oxidative polymerization method is cyclic voltammetry or potentiostatic method;

Further, the potential scanning range of the cyclic voltammetry is 0.2-1.0V, and the scanning speed is 50mV/s.

Compared with the prior art, the invention solves the problems of low information storage density and low solubility of the metal polymer rich in metal units of the prior binary memristor metal polymer, and has the specific beneficial effects that:

1. The ternary nonvolatile memristive property is that cobalt^III complex monomers are polymerized in situ on the surface of an electrode through electrochemical oxidation polymerization reaction and are uniformly deposited to prepare a cobalt-containing^III polymer film, the deposited cobalt-containing^III polymer film is initially in a high-resistance state (S₀), when a certain negative bias voltage is applied, metal centers and ligands are subjected to reduction reaction, extra electrons are injected into the polymer film from the electrode to improve conductivity and cause a low-resistance state (S₁), when a certain positive bias voltage is applied, the reduced ligands are oxidized to cause an extra middle low-resistance state (S₂), the bias voltage is continuously increased, the reduced metal centers are subjected to oxidation reaction to enable the cobalt-containing^III polymer film to return to the high-resistance state (S₀), and the reversible switching of three resistance states is realized by utilizing the reduction and oxidation properties of the metal centers and the ligands of the cobalt-containing^III polymer under different bias voltages, so that a stable and controllable electrical property foundation is provided for the application of nonvolatile storage.

2. The cobalt^III -containing polymer film exhibits a loose porous structure, and as each cobalt^III complex monomer carries three counter ions, the counter ions dynamically migrate during the polymerization process to form a porous structure. Under the external electric field, ions migrate and redistribute along the channel, which can cause enhancement of the interfacial local electric field, which can promote the injection of additional holes and electrons from the electrode to the polymer, thereby causing molecular redox, and the structure is beneficial to the memristive property of the cobalt^III -containing polymer film.

3. The cobalt^III complex monomer provided by the invention has a pair of electrochemical oxidation active group triphenylamine, has high reactivity under a certain positive potential, can polymerize and deposit a metal polymer film on the surface of an electrode in situ, can monitor the growth process of the film by adopting an absorption spectrometry and an electrochemical method, can control the thickness of the cobalt^III -containing polymer film by changing the polymerization circles, realizes the regulation and control of the deposition of the metal polymer film, and can prepare uniform and stable films with different thicknesses according to the requirements.

4. The preparation process is simple and efficient, the metal polymer film is polymerized and uniformly deposited on the surface of the electrode by the electrochemical polymerization method, no extra film forming step is needed, the preparation process is simple, the problem of low solubility of the metal polymer rich in metal units is effectively solved, the polymerization reaction is quick and efficient, the requirements on equipment and operation are low, a common electrochemical workstation is used, the time and cost consumption is reduced, the film performance can be controlled by adjusting polymerization parameters, the flexibility and the customization are excellent, and the method can be applied to large-scale industrialization.

Drawings

FIG. 1 is a flow chart of a preparation process of a cobalt^III complex monomer;

FIG. 2 is a schematic diagram of a three-layer structure of a gallium indium liquid alloy/film/indium tin oxide during a resistance change test;

FIG. 3 is a cyclic voltammogram of monitoring the polymerization process of a cobalt-containing^III polymer;

FIG. 4 is a graph of the absorption spectra of a polymer polymerization process monitor containing cobalt^III;

FIG. 5 is a plot of current density versus bias voltage for the cobalt^III -containing polymer prepared in example 2;

FIG. 6 is a plot of current density versus time and bias versus time for writing, reading, and erasing a cobalt^III -containing polymer prepared in example 2;

FIG. 7 is a plot of current density versus bias voltage for the cobalt^III -containing polymer prepared in example 3;

FIG. 8 is a plot of current density versus bias voltage for the cobalt^III -containing polymer prepared in example 4;

FIG. 9 is a plot of current density versus bias voltage for the cobalt^III -containing polymer prepared in example 5;

FIG. 10 is a plot of current density versus bias voltage for the cobalt^III -containing polymer prepared in example 10.

Detailed Description

In order to make the technical solution of the present invention clearer, the technical solution of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the present invention, and it should be noted that the following embodiments are only used for better understanding of the technical solution of the present invention, and should not be construed as limiting the present invention.

Example 1.

S1 to a round bottom flask with magnetic stirring bar was added 4 '-bromo-2, 2':6',2 "-terpyridine (312 mg,1 mmol), triphenylamine 4-borate (318 mg,1.1mmol,1.1 eq), palladium tetraphenylphosphine (7 mg,0.03mmol,0.03 eq), cesium carbonate (978 mg,3mmol,3 eq), tetrahydrofuran (30 mL) and deionized water (5 mL) under stirring reflux for 48h, after completion of the reaction, cooled to room temperature, diluted with 30mL dichloromethane, followed by three washes with deionized water (50 mL), followed by drying the organic layer with anhydrous sodium sulfate, filtration and concentration, and the resulting crude product was purified by silica gel column chromatography (eluting with methanol, dichloromethane, ammonia water at a volume ratio of 1:8:1) to give ligand 4' - (4- (diphenylamino) phenyl) 2,2':6',2" -terpyridine (calculated as [ M⁺ 476.20, calculated as calculated 85% yield ).¹H NMR(500MHz,CD₂Cl₂)δ8.64(s,2H),8.62(d,J＝4.9Hz,2H),8.59(d,J＝8.0Hz,2H),7.81(t,J＝7.7Hz,2H),7.71(d,J＝8.9Hz,2H),7.28(dd,J＝7.5,4.7Hz,2H),7.23(t,J＝8.5,7.5Hz,4H),7.11-7.05(m,6H),7.00(t,J＝7.3Hz,2H).¹³C NMR(500MHz,CD₂Cl₂)δ156.34,156.05,149.61,149.27,149.06,147.52,136.93,131.75,129.52,128.08,125.06,123.95,123.62,123.04,121.19,118.08,29.83.MALDI-TOF：m/z, actual measured 476.2).

S2, adding ligand 4'- (4- (diphenylamino) phenyl) 2,2':6', 2' -terpyridine (98 mg,0.205mmol,2.05 eq.) prepared in S1 and 10mL of dichloromethane into a round bottom flask with a magnetic stirring rod, stirring until the ligand is completely dissolved, dropwise adding 5mL of methanol solution with anhydrous cobalt dichloride (13 mg,0.1mmol,1 eq.) to the solution, stirring for 15min, removing the solvent by rotary evaporation after the reaction, adding 3mL of methanol to dissolve the obtained crude product, continuing to add saturated aqueous potassium hexafluorophosphate solution to precipitate intermediate, washing the precipitate with water, toluene and diethyl ether in sequence, dissolving the precipitate in 3mL of acetonitrile, adding silver nitrate (85 mg,0.5mmol,5 eq.) to the solution, filtering to remove the precipitate, washing the precipitate with acetonitrile until the solution is colorless, concentrating the filtrate, adding saturated aqueous potassium hexafluorophosphate solution to the solution, filtering the precipitate, washing the precipitate with water and diethyl ether, dissolving the crude product in dichloromethane, purifying the crude product by volume ratio of dichloromethane (volume ratio of 37:35 is 3275), preparing the monomer according to FIG. 3275 by a solution, and preparing the monomer according to the actual process of FIG. 3235, wherein the actual process is shown in FIG. 3235, and the actual yield is 3275.

Example 2.

S1, dissolving cobalt^III complex monomer in dichloromethane containing 0.1M supporting electrolyte, wherein the concentration of cobalt^III complex monomer is 0.2mM, and the supporting electrolyte is tetrabutylammonium perchlorate;

S2, sequentially ultrasonically washing a working electrode Indium Tin Oxide (ITO) electrode with toluene, acetone and ethanol for 20min, and then drying for standby, burning a counter electrode platinum sheet electrode at high temperature, removing organic matters attached to the surface of the electrode, and washing the electrode after the electrode is cooled to normal temperature with dichloromethane, and drying for standby;

S3, adding the cobalt^III complex monomer solution prepared by the S1 into a 5mL beaker, and adopting a standard one-chamber three-electrode system. Placing a working electrode, a counter electrode and a reference electrode into a beaker, carrying out electrochemical polymerization by using a CHI660E electrochemical workstation and adopting a cyclic voltammetry, wherein the potential scanning range is 0.2-1.0V, the scanning speed is 50mV/s, taking the working electrode out of the solution after each scanning turn, cleaning with dichloromethane, drying, and scanning for 1 turn to obtain a cobalt-containing^III polymer film, and monitoring the polymerization process of each turn of film by using an ultraviolet-visible absorption spectrum and scanning a cyclic voltammogram in a blank electrolyte solution.

Example 3.

The difference between this example and example 2 is that the number of scanning turns was changed to 5, and the other experimental procedures and conditions were the same as those of example 2, to prepare a cobalt^III -containing polymer film.

Example 4.

The difference between the present example and example 3 is that the counter electrode is a gold electrode, the working electrode is FTO, the supporting electrolyte is tetraethylammonium hexafluorophosphate, the solvent is a mixed solvent of dichloromethane and acetonitrile in a volume ratio of 1:1, and other experimental steps and conditions are the same as those of example 3, so as to prepare the cobalt-containing^III polymer film.

Example 5.

The difference between this example and example 3 is that the working electrode was changed to a gold-plated silicon wafer, the supporting electrolyte was tetrapropylammonium hexafluoroarsenate, the solvent was methanol, and other experimental procedures and conditions were the same as in example 3, to prepare a cobalt-^III -containing polymer film.

Example 6.

The difference between this example and example 3 is that the working electrode was changed to silver, the supporting electrolyte was tetramethyl ammonium tetrafluoroborate, the solvent was ethanol, and other experimental procedures and conditions were the same as in example 3 to prepare a cobalt^III -containing polymer film.

Example 7.

The difference between this example and example 3 is that the working electrode was changed to titanium, the solvent was chloroform, and other experimental procedures and conditions were the same as in example 3 to prepare a cobalt^III -containing polymer film.

Example 8.

The difference between the embodiment and the embodiment 3 is that the working electrode is changed to be high-efficiency pyrolytic graphene, the solvent is tetrahydrofuran, and other experimental steps and conditions are the same as those of the embodiment 3, so that the cobalt-containing^III polymer film is prepared.

Example 9.

The difference between this example and example 3 is that the working electrode was changed to titanium dioxide, and the other experimental procedures and conditions were the same as in example 3 to prepare a cobalt^III -containing polymer film.

Example 10.

The difference between this example and example 3 is that the working electrode was changed to platinum and the supporting electrolyte was tetrabutylammonium tetraphenyl borate, and the other experimental procedures and conditions were the same as in example 3 to prepare a cobalt-containing^III polymer film.

Memristance test of metal polymers:

Memristance testing was performed using an X-Tech series SAMJ module (pareil technologies, inc.) to prepare a grounded gallium indium liquid alloy (EGaIn) tip as the top electrode in contact with a cobalt^III -containing polymer film, applying a bias voltage to the indium tin oxide bottom electrode, and reading the current signal through the top electrode by a logarithmic amplifier calibrated by a 100 Ω -100mΩ resistance, as shown in fig. 2, which is a schematic diagram of the gallium indium liquid alloy/film/indium tin oxide three-layer structure during the resistance change test. As shown in fig. 3 and fig. 4, which are cyclic voltammograms and absorption spectra of the polymer containing cobalt^III prepared in example 3, it can be seen from fig. 3 and fig. 4 that during the polymerization, the absorption characteristic peak and the oxidation-reduction characteristic peak of the film both increase uniformly with the increase of the number of scanning turns, because the periodic variation of the electric potential is used for oxidizing and polymerizing the triphenylamine groups, the more the number of scanning turns is, the more the monomer is involved in polymerization, the thicker the polymer film containing cobalt^III, and therefore, the absorption characteristic peak and the oxidation-reduction characteristic peak change synergistically with the change of the number of scanning turns, which indicates that the deposition process of the polymer film containing cobalt^III on the electrode is a continuous and uniform process, and the phenomenon of excessively rapid or excessively slow local deposition does not exist.

As shown in fig. 5, which is a graph of the current density-bias voltage relationship of the cobalt-containing^III polymer prepared by scanning one cycle of cyclic voltammetry of example 2, the scanning speed is 500mV/S, and it can be seen from the graph that the cobalt-containing^III polymer film has a ternary nonvolatile memristive property, and in the initial state, the film is in a high resistance state (S₀), the metal center and the ligand reduction process respectively correspond to two different low resistance states (S₂ and S₁) along with the change of the bias voltage, and the three resistance states can be switched under a specific bias voltage. The film is switched from the high resistance state S₀ to the low resistance state S₁ during scan 1, sometimes to the intermediate low resistance state S₂ during scan 3, and back to the high resistance state S₀ during scan 2 and 4, with the resistance state of the film remaining unchanged. Since the J-V curve is random, it is difficult to determine the switching voltage therefrom. FIG. 6 is a graph of current density versus time and bias versus time for constant bias writing, reading, erasing using manual constant bias switching and recording of corresponding current signals and time, using high bias (-1.3, -0.8), 1.0 or 2.0V) to switch the resistance state (write or erase) of the film, after each resistance state transition, the current resistance state is read by applying a low bias of-0.1V, further verifying that the cobalt^III -containing polymer film has three different resistance states, and determining the switching relationship between the resistance states, namely, the film is switched from S₀ to S₁ when-1.3V is applied, the film is switched from S₁ to S₂ when-1.0V is applied, the film is restored from S₂ to S₁ when-0.8V is applied, and the film returns to S₀ when 2.0V is applied, thereby completing the erase operation. These phenomena prove that the film can stably switch three resistance states S₀、S₁、S₂ under specific bias, and further verify the memristive property.

As can be seen from the graphs of the current density-bias voltage relationship of the cobalt-containing^III polymer of the scan 5-cycle voltammetry prepared in examples 3-5 and 10, respectively, the cobalt-containing^III polymer films prepared in the above examples all have memristive properties and exhibit certain randomness. This is because the thickness of the cobalt^III -containing polymer film increases with the number of scan turns, which complicates the carrier transport path and increases the randomness, affecting its stability, and in addition, the larger anion volume may cause the increase of the internal pores of the film, increase the mobility randomness, and thus affect the uniformity of the current density-bias curve.

According to the invention, cobalt^III complex monomers are polymerized in situ and deposited uniformly on the surface of an electrode through electrochemical oxidation polymerization reaction to prepare a cobalt^III -containing polymer film, the growth process of the film is monitored by adopting an absorption spectrum method and an electrochemical method, and the reversible switching of three resistance states is realized by utilizing the redox characteristics of the metal center and the ligand of the cobalt^III -containing polymer under different bias voltages, so that a stable and adjustable electrical property foundation is provided for nonvolatile storage application. The preparation process is simple and efficient, effectively solves the problem of low solubility of the metal polymer, and can be applied to large-scale industrialization.

The above description of the embodiments is only for aiding in the understanding of the method of the present invention and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A complex monomer is characterized in that the structural formula is shown as a formula (I):

2. A process for the preparation of the complex monomer according to claim 1, comprising the steps of:

And then carrying out oxidation reaction on soluble silver salt and the obtained cobalt^II complex in the solvent, removing precipitate after the reaction is finished, washing the precipitate until filtrate is colorless, concentrating the filtrate, continuously adding saturated potassium hexafluorophosphate aqueous solution to precipitate a product, filtering, washing the precipitate to obtain a crude product, and purifying the crude product to obtain the cobalt^III complex monomer with the structure shown in the formula (I).

3. The method for preparing the complex monomer according to claim 2, wherein the terpyridine ligand has a structural formula shown in formula (II):

the molar ratio of the terpyridine ligand to the divalent cobalt salt is 2-2.5:1, and the molar ratio of the soluble silver salt to the cobalt^II complex is 3-8:1.

4. The preparation method of the complex monomer according to claim 2, wherein the divalent cobalt salt is any one of cobalt dichloride, cobalt nitrate, cobalt perchlorate or cobalt tetrafluoroborate, the soluble silver salt is any one of silver nitrate, silver hexafluorophosphate, silver tetrafluoroborate or silver trifluoromethane sulfonate, the solvent is any one of methanol, ethanol, ethylene glycol or acetonitrile, the coordination reaction time is 5-30 min, and the oxidation reaction time is 3-10 min.

5. The ternary memristive metal polymer is characterized by having a structural formula shown in a formula (III):

6. a method of preparing the ternary memristive metal polymer of claim 5, comprising the steps of:

And dissolving cobalt^III complex monomer into a solution containing supporting electrolyte, then placing the solution into a working electrode, a counter electrode and a reference electrode, and performing electrochemical oxidative polymerization to realize in-situ deposition to prepare the cobalt^III -containing polymer film.

7. The method of preparing a ternary memristive metal polymer according to claim 6, wherein the supporting electrolyte is composed of an anion and a cation, the anion is any one of tetrafluoroborate ion, tetraphenylborate ion, hexafluorophosphate ion, hexafluoroarsenate ion or perchlorate ion, the cation is tetraalkylammonium ion, and the alkyl is any one of methyl, ethyl, propyl or butyl.

8. The method of claim 6, wherein the solvent in the solution is any one or a combination of at least two of acetonitrile, ethanol, methanol, dichloromethane, chloroform, or tetrahydrofuran.

9. The method for preparing the ternary memristive metal polymer according to claim 6, wherein the working electrode and the counter electrode are any one of an inert metal electrode, a semiconductor electrode or a carbon material, the inert metal electrode is platinum, gold, silver or titanium, the semiconductor electrode is indium tin oxide, fluorine-doped tin oxide or titanium dioxide, the carbon material electrode comprises graphene, and the reference electrode is a silver-silver ion electrode.

10. The preparation method of the ternary memristive metal polymer according to claim 6, wherein the electrochemical oxidation polymerization method is cyclic voltammetry or potentiostatic method, and the potential scanning range of the cyclic voltammetry is 0.2-1.0V, and the scanning speed is 50mV/s.