Temperature-controlled supramolecular chirality of oligoaniline helical nanoribbons in an achiral molecule-mediated synthesis system

Abstract

This case involves a method for temperature-controlled supermolecular chirality of oligoaniline helical nanoribbons in a non-chiral molecule-mediated synthesis system. A mixed solvent of acetone and water is used as the mediating system. Aniline is dissolved in the mixed solvent to obtain a mixed solution. A certain amount of ammonium persulfate aqueous solution is then added, stirred and mixed evenly, and then placed at 0-27°C for a certain period of time. The precipitate that appears in the system is the oligoaniline helical nanoribbon. The present invention successfully achieves the synthesis of helical chiral nanoribbons by mediating the assembly of aniline monomers in a non-chiral acetone / water mixed solvent. The reaction process is simple and easy to operate, the raw materials are readily available, the prepared nanoribbons have obvious helical structures, strong chiral signals, and good environmental stability, and have good application prospects in materials chemistry, especially in chiral recognition and resolution and chiral crystallization. And through the construction method of the present invention, chirality reversal can be achieved simply by regulating the temperature.

Description

Technical Field

[0001] The present invention relates to the fields of nanochemical material technology and supramolecular self-assembly technology, and in particular to a method for regulating the supramolecular chirality of oligoaniline helical nanoribbons by temperature in a non-chiral molecule-mediated synthesis system. Background Art

[0002] Chirality is a common phenomenon in nature and an important characteristic of living organisms. Research and exploration of chirality issues are of great significance to the development of related disciplines such as life science, pharmacy, and materials science. In addition to traditional molecular chirality, many small molecules can also be assembled in an orderly manner due to non-covalent bond effects (such as hydrogen bonds, π-π stacking, electrostatic effects, hydrophobic effects, etc.) to form three-dimensional asymmetric supramolecular structures; during the assembly process, the chirality of molecules is amplified in a nonlinear manner through certain aggregation forms, or molecules that originally did not have chiral characteristics show new chiral signals after assembly. This phenomenon is called supramolecular chirality. Depending on whether the assembly unit contains chiral molecules, supramolecular chiral assembly can be divided into three types: (1) supramolecular chiral assembly of chiral molecules; (2) supramolecular chiral assembly involving chiral molecules and achiral molecules; (3) supramolecular chiral assembly of achiral molecules. This assembly from achiral to chiral has more important research value and scientific significance because it involves the key scientific issue of the origin of chirality, and has aroused great interest among researchers in related disciplines.

[0003] Chiral conducting polymers are functional conjugated macromolecules with chiral molecular chain conformations or chiral groups. Due to their combined electrical and optical activity, they have attracted widespread attention in recent years due to their potential applications in chiral recognition and separation, chiral sensing, chiral synthesis, and catalysis. Currently, there are three main approaches to obtaining chiral conducting polymers: first, polymerization of chiral monomers. For example, the Nilsson group at the Norwegian University of Science and Technology synthesized chiral polypyrroles by polymerization of monomers grafted with chiral groups. Second, doping with chiral organic acids. The Li group at Los Alamos National Laboratory and the Wei Zhixiang group at the National Center for Nanoscience and Technology synthesized chiral polyaniline or its derivatives by doping with chiral camphorsulfonic acid. Third, chiral template induction. The Huang Xirong group at Shandong University and the Chen Jianbo group at Shanghai Normal University, respectively, prepared chiral polyaniline using different protein molecules as templates. Clearly, most of the currently reported methods for preparing chiral conducting polymers require the presence of chirality. However, constructing single-chirality conducting polymer functional materials in achiral molecular-mediated systems remains a major challenge. Summary of the Invention

[0004] In order to address the deficiencies in the prior art, the present invention constructs a unichiral oligomeric polyaniline in an achiral molecule-mediated system. The oligomeric polyaniline has electrochemical activity similar to that of conductive polyaniline.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for temperature-controlled chirality of oligoaniline helical nanoribbons in a non-chiral molecule-mediated synthesis system comprises the following steps:

[0007] A mixed solvent of acetone and water is used as the mediator system. Aniline is dissolved in the mixed solvent to obtain a mixed solution. A certain amount of ammonium persulfate aqueous solution is then added and stirred to mix evenly. The solution is then placed at 0-27°C for a certain period of time. The precipitate that appears in the system is oligoaniline helical nanoribbons.

[0008] Among them, when the reaction temperature is between 0 and 12 °C, left-handed oligoaniline nanoribbons are obtained;

[0009] When the reaction temperature is between 17 and 27 °C, right-handed oligoaniline nanoribbons are obtained.

[0010] Furthermore, the volume ratio of acetone to water in the mixed solvent is 3:7, and the concentration of aniline in the mixed solvent is 20-30 mmol / L.

[0011] Furthermore, the molar ratio of ammonium persulfate to aniline is 1.2:1.

[0012] Compared with existing technologies, the present invention offers the following advantages: chiral nanostructures of oligoaniline functional molecules have promising applications in fields such as chiral resolution, chiral sensing, and chiral catalysis. The present invention successfully mediates the assembly of helical chiral nanoribbons from aniline monomers in an achiral acetone / water mixed solvent. The reaction is simple and easy to operate, and the raw materials are readily available. The resulting nanoribbons exhibit distinct helical structures, strong chiral signals, and excellent environmental stability. These nanoribbons have promising applications in materials chemistry, particularly in chiral recognition and resolution, and chiral crystallization. Furthermore, the present invention's construction method allows for chirality reversal simply by controlling temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 (a, b) FESEM and (ce) TEM images of the product obtained at 0°C.

[0015] Figure 2The matrix-assisted laser desorption ionization time-of-flight mass spectrum (MALDI-TOF MS) of the product obtained at 0°C is shown.

[0016] Figure 3 (a) High performance liquid chromatography (HPLC) graph of the product obtained at 0°C and (b) mass spectrometry (LC-MS) graph of the component with a retention time of 6.3-6.9 minutes.

[0017] Figure 4 (a) FTIR spectrum and (b) NMR spectrum of the product obtained at 0°C 1 H NMR spectrum.

[0018] Figure 5 UV-vis spectrum of the product obtained at 0°C under doping-undoping conditions.

[0019] Figure 6 Circular dichroism spectra of the products dispersed in water at different temperatures. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] Example: A method for temperature-controlled unichiral oligoaniline helical nanoribbons in an achiral molecule-mediated system

[0023] Step (1), add 0.8 mmol of aniline to a conical flask, then add 6 ml of acetone and 12 ml of water, shake to obtain a uniform solution, and place it in a T℃ environment for 20 min;

[0024] Step (2), dissolve 0.96 mmol of ammonium persulfate in 2 mL of water and place at T℃ for 10 minutes;

[0025] Step (3), adding the ammonium persulfate aqueous solution in step (2) into the solution in step (1) at one time, and shaking the resulting solution for 20 seconds to ensure complete mixing;

[0026] Step (4), placing the reaction solution of step (3) in a T℃ environment for 12 hours;

[0027] In step (5) and step (4), the lower precipitate is removed from the reaction solution and the precipitate is washed with deionized water several times until the filtrate becomes colorless.

[0028] The temperature environment T℃ was set to 0℃, 5℃, 12℃, 17℃, 22℃, and 27℃, and the above experiments were carried out respectively.

[0029] Taking the product obtained at 0℃ as an example, the product was characterized by FESEM, TEM, MALDI-TOF MS, HPLC, LC-MS, FTIR, 1 H NMR, UV-vis and other instruments were used to characterize the molecular structure of the product.

[0030] like Figure 1 These are the FESEM and TEM images of oligoaniline prepared at 0°C. The FESEM image shows that the sediment contains a large number of spiral nanoribbons, mainly left-handed nanoribbons. The TEM results show that the spiral nanoribbons are composed of parallel fibers.

[0031] Figure 2 The oligoaniline helical nanoribbons prepared by the present invention are mainly composed of molecules with m / z=289, which are characterized by HPLC and LC-MS ( Figure 3 a, b), and determined the molecular structure of m / z=289. The results showed that the product prepared by the method of the present invention mainly contained triphenylamine derivative molecules.

[0032] pass Figure 4 The existence of aniline trimers containing benzoquinoneimine was further confirmed.

[0033] Figure 5 The UV-visible spectrum of the oligoaniline derivative under doping and dedoping is shown; the results show that the prepared oligoaniline can be doped and dedoped, maintaining the unique properties of conductive polymers.

[0034] The above results indicate that the prepared helical nanoribbons mainly contain an aniline trimer, and the oligoaniline retains the doping / undoping properties of polyaniline.

[0035] The circular dichroism spectra of oligoaniline helical nanoribbons obtained at different reaction temperatures are shown in Figure 2. Figure 6As shown in the figure, the product obtained by the reaction at 0°C exhibits only a weak positive CD signal in the 250-360 nm range, while the product obtained by the reaction at 5°C exhibits a distinct positive CD signal at 325 nm. As the reaction temperature increases to 12°C, the positive CD signal at this wavelength further increases. However, at 17°C, the CD signal of the product reverses, with strong negative CD signals appearing at 236 and 279 nm. At 22°C, the product exhibits a strong negative CD signal at 289 nm. However, when the temperature is further increased to 27°C, the product exhibits only a weak negative CD signal in the 270-340 nm range. These experimental results indicate that reaction temperature can regulate the supramolecular chirality of the product. At reaction temperatures of 5°C or 12°C, the product exhibits positive circular dichroism signals, while at reaction temperatures of 17°C or 22°C, products with negative circular dichroism signals are obtained. That is, the method provided by the present invention realizes the synthesis of supramolecular chiral oligoaniline by mediating aniline monomer in an achiral molecular system, and the chirality of the oligoaniline can be flipped by simple temperature regulation.

[0036] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for temperature-controlled chirality of oligoaniline helical nanoribbons in a non-chiral molecule-mediated synthesis system, characterized in that: The steps include: Step (1) Add 0.8 mmol of aniline to a conical flask, then add 6 ml of acetone and 12 ml of water, shake to obtain a uniform solution, and place it in an environment of T℃ for 20 min; Step (2), dissolve 0.96 mmol of ammonium persulfate in 2 mL of water and place at T ℃ for 10 minutes; Step (3), adding the ammonium persulfate aqueous solution in step (2) into the solution in step (1) at one time, and shaking the resulting solution for 20 seconds to ensure complete mixing; Step (4), placing the reaction solution of step (3) in a T℃ environment for 12 hours; In step (5) and step (4), the lower precipitate is removed from the reaction solution and the precipitate is washed with deionized water several times until the filtrate becomes colorless; Among them, the temperature environment T℃ is set to 0℃, 5℃, 12℃, 17℃, 22℃ or 27℃.

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