WO2012108300A1

WO2012108300A1 - Silica-based chiral nanostructures and processes for producing same

Info

Publication number: WO2012108300A1
Application number: PCT/JP2012/052088
Authority: WO
Inventors: 金　仁華; 裕之松木囿
Original assignee: 一般財団法人川村理化学研究所
Priority date: 2011-02-09
Filing date: 2012-01-31
Publication date: 2012-08-16
Also published as: JP5060670B2; JPWO2012108300A1

Abstract

Silica-based chiral nanostructures each comprising or obtained from a silica/organic-substance composite having chirality are provided, the nanostructures being obtained through a step in which an aqueous solution of a polymer having a linear polyethyleneimine skeleton is mixed with an aqueous solution of an optically active tartaric acid to obtain chiral crystals of an acid-base complex and a step in which a silica source is subjected, in the presence of the chiral crystals obtained in that step, to a sol-gel reaction to coat the chiral crystals with silica to which the chiral structure of the chiral crystals has been transferred. The structures are silica-based chiral nanostructures which are stable even to high-temperature burning. The structures can be converted to organic-silane-modified silica-based chiral nanostructures by bonding an organic silane to the silica.

Description

Silica-based chiral nanostructure and method for producing the same

The present invention relates to a silica-based chiral nanostructure in which chirality is imparted to silica, which is derived from a chiral crystal composed of a polymer having a linear polyethyleneimine chain and optically active tartaric acid, and a method for producing the same.

∙ Chirality in organic materials exists widely from low molecules to macromolecules, and life forms are supposed to operate on the premise of the existence of chirality molecules. Chiral molecules are substances that must be in the fields of medicine, liquid crystals, optical materials, and electronic materials. In general, the chirality of organic substances is derived from having an asymmetric central element (for example, carbon, phosphorus, sulfur, etc.), an asymmetric axis, an asymmetric surface, etc. in the molecular structure. The structure also forms a positive or negative cotton helical structure. In the case of a chiral polymer, an asymmetric structure is usually included in the structural unit of the polymer molecule, thereby expressing various functions of the chiral polymer. Aside from this, even if the polymer molecule itself does not have an asymmetric structure, a chiral molecule that can interact with the polymer is physically bonded to the achiral polymer, thereby creating a chiral space in the polymer structure. Induced and converted into functional material with chiral information. A quasi-chiral polymer complex consisting of a molecular complex of a chiral molecule and an achiral polymer has many advantages such as simplicity of manufacturing method, high degree of freedom in material structure control, and diversity in functional expression. There is a lot of research in Japan. On the other hand, unlike the chirality of organic substances at the molecular level, research and development of chiral minerals by adding chirality cavities or spirals in inorganic materials have attracted much attention.

For example, a gel having a spiral fiber as a basic structure is formed with a chiral organic compound in an organic solvent, and then mixed with alkoxysilane, an amine as a catalyst, and a small amount of water for hydrolysis of silane, to form a spiral. It has been reported that chiral silica is formed (see, for example, Patent Document 1). This method uses the fact that water is not a medium and a chiral organic compound forms a fibrous gel in an organic solvent, and the alkoxysilane hydrolyzed by the catalytic action of the added amine compound in the organic solvent. Silica sol is deposited on the surface of the spiral fiber.

Unlike the formation of a fibrous gel of a chiral organic compound in an organic solvent, a hydrogel composed of four carboxylic acid-containing amphiphilic chiral aliphatic compounds formed in water is used as a template, and contains alkoxysilane and amino groups. It has been reported that a hybrid-type chiral silica nanowire is formed by mixing a silane coupling agent at a certain ratio and reacting at room temperature for 5 to 10 days (see, for example, Non-Patent Document 1). It is disclosed that when an organic compound inside the silica is extracted, a helical chiral silica nanotube is obtained, but the chirality exists on the hollow inner wall, and no chirality appears in the outer wall of the nanotube.

Unlike silica precipitation on the surface of the above chiral gel fiber, an anionic chiral surfactant having an amino acid residue is mixed with a cationic silane coupling agent having an amino group and a tetraalkoxysilane of silica source, It has been reported that chiral mesoporous silica with a helix form is obtained by reacting in an acidic medium (see, for example, Non-Patent Document 2). In this reaction, a chiral anionic surfactant and a cationic silane coupling agent assemble to form a chiral micelle, and the cationic silane coupling agent on the surface layer of the micelle undergoes hydrolytic condensation. . Then, along the hexagonal aggregate of the micelles, hydrolysis and condensation reaction of alkoxysilane proceeds outside each micelle surface layer, resulting in the formation of chiral silica induced by chiral micelles, A composite composed of chiral silica is obtained. The reason for the details is unknown, but the chiral silica obtained in this way is in a helix form. When this is heated and baked to remove the organic components inside, it becomes a helix-shaped mesoporous silica having a channel with an air diameter of 2 to 4 nm.

This method is similar to the above chiral micelle method, but instead of using a chiral surfactant, a chiral micelle is formed by the interaction of an achiral anionic surfactant and a chiral amino compound, which is used as a template, under acidic conditions. It has been reported that a complex of helix chiral silica and an organic substance is obtained by causing hydrolysis and condensation reaction of alkoxysilane (see, for example, Non-Patent Document 3). By removing the organic component in the composite, a silica nanotube having a helix and an inner diameter of several tens of nanometers can be obtained.

Contrary to using these chiral micelles as templates, in spite of the fact that no chiral compounds are used, a micellar reaction field consisting of ordinary achiral surfactants is formed in an acidic aqueous medium. It has been reported that a mesoporous silica having a helix structure can be obtained by mixing a alkoxysilane and inducing a seed structure and then adding a solution having the seed structure to an acidic aqueous solution (see, for example, Non-Patent Document 4). ). This suggests that the helix structure itself has nothing to do with chirality. In other words, in chiral mesoporous silica, the helix itself is not chiral, but a chiral structure is imparted to the mesopore. The chiral mesoporous silica using the above-described chiral micelle as a template requires a strong acidic medium in the sol-gel reaction of alkoxysilane at the synthesis stage, and requires aging at a temperature around 90 ° C. Furthermore, the production of chiral micelles requires the synthesis of chiral surfactants or chiral ionic molecules. Supplying these chiral sources is not possible in existing industries. Using chiral molecules that are widely used in industry, interacting with existing achiral molecules that are manufactured and sold industrially to induce chiral supramolecular complexes, as well as chiral minerals that use them as a template, silica There are still no examples of construction.

In general, when chirality is imparted to a mineral cavity, the cavity wall is composed of a hard inorganic material, and thus it is considered to be a semi-permanent chiral substance that is strong in heat resistance and durability. However, considering that the structural thermal stability of ordinary mesoporous silica is insufficient, it is highly possible that the chiral thermal stability of chiral mesoporous silica cannot be expected. At present, many research reports on chiral mesoporous silica are disclosed, but there is no report discussing the thermal stability of chirality, and little is known about the maintenance of chiral structure by high-temperature firing.

In addition, silica synthesis with chirality is not based on biomimetic silification techniques such as room temperature, neutrality, and high speed, and the reaction process is not environmentally friendly, such as in acidic or basic conditions under sol-gel reaction conditions. There were no drawbacks.

When thinking of silica as a material and device, it is necessary to understand biosilica that inhabits the natural world. Biosilica is classified into diatoms and sponges, which are unicellular organisms whose cell walls are constructed of silica with a very complex pattern and elaborate structure. In the silica, polypeptides and proteins are complexed to form a nano-level hybrid structure. In fact, in this hybrid structure formation, the polypeptide or protein functions as a template as well as a catalyst that condenses silicic acid and grows it on silica. This is because the cell wall of biosilica, that is, the silica wall, is derived from a chiral polypeptide or chiral protein, and it can be inferred that the silica internal structure is more or less accompanied by chirality. However, this has never been proved, and there is no example of artificially designing and synthesizing chiral silica using this principle. By the way, natural biosilica is produced in units of gigatons per year. In the process of production, silicic acid is converted to silica under mild conditions such as room temperature, normal pressure, and neutrality.

In recent years, many studies enlightened by biosilica have been reported. Many of them are concentrated on the synthesis and study of the mechanism of silica nanoparticles or silica nanoplates using organic polyamines and basic polypeptides under conditions such as room temperature, atmospheric pressure, and neutrality. However, there are no reports on the synthesis of chiral silica that makes use of the mild conditions.

The present inventors have already paid attention to the crystallization of linear polyethyleneimine as part of the manufacturing that learns from biosilica, and constructed a complex hierarchical silica by using the fibrous crystals and their crystals in the reaction field. It has developed. However, the crystal obtained by these methods is a crystal of linear polyethyleneimine alone, and the crystal is ethyleneimine in the polymer, that is, two molecules of water are bonded to one monomer unit. It was characterized by.

JP 2001-253705 A

In view of the above situation, the problem to be solved by the present invention is to use a basic principle of biosilica formation in room temperature, normal pressure, neutral aqueous medium, that is, an organic structure having chirality as a catalyst and a template. Silica / organic composite silica-based chiral nanostructures with chirality by utilizing the sol-gel reaction spontaneously induced by silica, silica-based chiral nanostructures that are stable even at high temperature firing, and organic silanes bonded to silica The object is to provide a silane-modified silica-based chiral nanostructure and a method for producing them.

In the silica construction learned from biosilica, the presence of organic matrix is a prerequisite for silica structure control. The organic matrix is often a basic polyamine, which effectively precipitates silica under mild conditions of normal temperature, normal pressure, and neutrality in cooperation with acidic molecules such as phosphate residues.

As a result of intensive studies to solve the above-mentioned problems, the present inventor has combined a non-evaporable chiral organic acid with an achiral polymer having a linear polyethyleneimine skeleton. A linear polyethyleneimine is formed by an acid-base interaction between a base of a polymer having a linear polyethyleneimine skeleton and a chiral organic acid, not a crystal formed by an interaction between a polymer having a linear polyethyleneimine skeleton and a water molecule. A crystalline structure composed of a chiral supramolecular complex derived by incorporating the chiral molecule into a polymer having a skeleton is constructed, and the chiral crystalline structure is subjected to a hydrolytic condensation reaction of alkoxysilane (ie, By using it as a catalyst and template for a sol-gel reaction) Nanostructures silica / organic substance complexed to, it found that silica-based nanostructures are obtained having stable chirality in firing a high temperature, and completed the present invention.

That is, the present invention comprises (1) mixing an aqueous solution of a polymer (A) having a linear polyethyleneimine skeleton with an aqueous solution of optically active tartaric acid (B) to obtain an acid-base complex chiral crystal (X). (2) A sol-gel reaction of silica source (Y ′) is carried out in the presence of the chiral crystal (X) obtained in the step (1), and the chiral structure of the chiral crystal (X) is transferred. A process for coating the chiral crystal (X) with silica (Y), and a method for producing a silica-based chiral nanostructure and its structure [hereinafter referred to as silica-based chiral nanostructure (α)] ] To provide.

Furthermore, the present invention provides (3) the step of eluting the optically active tartaric acid (B) with an acidic or basic aqueous solution after the step (2), or (3 ′) the complex obtained in the step (2). A method for producing a silica-based chiral nanostructure having a chiral spatial structure in a silica structure characterized by having a step of firing and removing organic components, and the structure [hereinafter, a structure obtained by elution Is referred to as a silica-based chiral nanostructure (β), and a structure obtained by firing is referred to as a silica-based chiral nanostructure (γ)].

Furthermore, the present invention provides an organosilane-modified silica-based chiral nanostructure, wherein an O—Si—C bond is introduced into the silica of the silica-based chiral nanostructure (α to γ) obtained above. A method and structure are provided.

The chiral structure of the present invention is characterized by imparting chirality to silica nanostructures such as nanofibers and nanosheets. As indicated by SiO ₂ , silica has a —O—Si—O—Si—O— structure that repeats in chemical bonds and spreads three-dimensionally. Usually, this bond has no chirality, but the —O—Si—O—Si—O— linkage of silica formed in the presence of a chiral template has an asymmetric stereochemistry of the chiral template molecule and molecular assembly. Spatial structure is carved. As a result, the walls composed of silica bonds that support the asymmetric spatial structure are also chiral. Therefore, various asymmetric information can be exchanged at the gas / solid interface when the chiral wall is in contact with the gas and at the liquid / solid interface when in contact with the liquid. Naturally, by combining organic substances or bonding organic residues to the chiral wall, polarity control around the chiral wall, hydrophilization, hydrophobization, various functional groups, functional molecular units, metal complexes, etc. Can be arranged. Furthermore, it is also possible to combine metal nanoparticles and metal oxides around the chiral wall (cavity). Moreover, the process for producing the chiral structure of the present invention is very simple and can be synthesized on a large scale. Accordingly, the chiral structure of the present invention is a catalyst for asymmetric organic synthesis in the production of liquid crystalline, pharmacological, physiologically active, antimicrobial, and antiviral substances for industrial, pharmaceutical, and agricultural chemicals, and for organic racemic resolution. A wide range of applications such as asymmetric adsorbents, optical sensors related to polarization dimming, and security materials are possible.

2 is an XRD chart of a chiral crystal obtained in Example 1. FIG. 2 is a CD spectrum of the chiral crystal (a) obtained in Example 1 and the raw material D-tartaric acid (b). 3 is a solid-state ²⁹ Si-NMR spectrum of the silica-based chiral nanostructure (α-1) obtained in Example 1. 3 is a solid state ¹³ C-NMR spectrum of the silica-based chiral nanostructure (α-1) obtained in Example 1. 2 is a CD spectrum of the silica-based chiral nanostructure (α-1) obtained in Example 1. 2 is a SEM photograph image of the silica-based chiral nanostructure (α-1) obtained in Example 1. 2 is a TEM photograph image of the silica-based chiral nanostructure (α-1) obtained in Example 1. 2 is an XRD chart of a chiral crystal obtained in Example 2. 2 is a CD spectrum of the chiral crystal obtained in Example 2. 3 is a solid-state ²⁹ Si-NMR spectrum of the silica-based chiral nanostructure (α-2) obtained in Example 2. 3 is a solid state ¹³ C-NMR spectrum of the silica-based chiral nanostructure (α-2) obtained in Example 1. 3 is a CD spectrum of the silica-based chiral nanostructure (α-2) obtained in Example 2. 3 is a SEM photograph image of the silica-based chiral nanostructure (α-2) obtained in Example 2. 3 is a TEM photograph image of the silica-based chiral nanostructure (α-2) obtained in Example 2. 4 is a TEM photograph image of the silica-based chiral nanostructure (γ-1) obtained in Example 3. 3 is a CD spectrum of the silica-based chiral nanostructure (γ-1) obtained in Example 3. FIG. 3 is a CD spectrum of silica-based chiral nanostructure (γ-1) after adsorption of porphyrin in Example 3. FIG. 4 is a TEM photograph image of the silica-based chiral nanostructure (γ-2) obtained in Example 4. 4 is a CD spectrum of the silica-based chiral nanostructure (γ-2) obtained in Example 4. FIG. 4 is a CD spectrum of silica-based chiral nanostructure (γ-2) after adsorption of porphyrin in Example 4. FIG. 6 is a CD spectrum of the nanostructure after modification with organosilane in Example 5. It is CD spectrum of the nanostructure after the organosilane modification in Example 6. 6 is an XRD chart of a chiral crystal obtained in Example 7. 7 is a CD chart of the chiral crystal obtained in Example 7. FIG. 4 is a CD spectrum of the silica-based chiral nanostructure (α-3) obtained in Example 7. 4 is a SEM photograph image of the silica-based chiral nanostructure (α-3) obtained in Example 7. 3 is an XRD chart of a crystal obtained in Comparative Example 1. 3 is a solid-state ²⁹ Si-NMR spectrum of a silica-based nanostructure obtained in Comparative Example 1. 3 is a solid state ¹³ C-NMR spectrum of the silica-based nanostructure obtained in Comparative Example 1. 2 is a CD spectrum of the silica-based nanostructure obtained in Comparative Example 1. 2 is a CD spectrum of a nanostructure after adsorption of porphyrin in Comparative Example 1. 3 is a SEM photograph image of the silica-based nanostructure obtained in Comparative Example 1. 4 is an FT-IR spectrum of a silica-based chiral nanostructure (β-1) before and after the tartaric acid elution step in Example 8. (A): Before the elution process, (b): After the elution process CD after adsorbing copper ions to the silica-based chiral nanostructure (β-1) of Example 8, the silica-based chiral nanostructure (β-2) of Example 9 and the silica-based nanostructure of Comparative Example 2 respectively. It is a spectrum. (A) Example 8, (b) Example 9, (c) Comparative Example 2. 3 is a solid CD spectrum after adsorbing 2-methyl-1,4-naphthoquinone on the silica-based chiral nanostructure of Example 10. FIG. (A) Measurement sample cell fixing angle is 0 °, (b) Measurement sample cell fixing angle is rotated by 90 °, (c) Comparative 2-methyl-1,4-naphthoquinone powder and KCl mixed sample.

The present inventors have already used a crystalline aggregate in which a polymer having a linear polyethyleneimine skeleton grows in an aqueous medium in a self-organizing manner as a reaction field, and hydrolyzes alkoxysilane on the surface of the aggregate in a solution. A silica-based nanostructure having a complex shape (powder) having nanofibers, nanosheets, and the like as basic units by decomposing condensation and precipitating silica, and a method for producing the same have been provided (Japanese Patent Laid-Open No. 2005-264421) JP, 2005-336440, JP 2006-063097, JP 2007-051056, Chem. Commun., 2005, 1399-1401, Langmuir 2005, 21, 3136-3145, Adv. 2006, 16, 2205-2212, CrystEngCo m, see, for example, 2009,11,2695-2700).

These techniques utilize the fact that polymer crystals are precipitated by dissolving a polymer having a linear polyethyleneimine skeleton in hot water and cooling the solution to room temperature. The crystal always has a composition in which two water molecules are bonded to one ethyleneimine unit. Thereafter, the silica with a special shape can be rapidly precipitated by simply mixing the crystal with a silica source at room temperature. This process is extremely simple and highly efficient, but naturally does not exhibit chirality.

If a non-evaporable chiral compound can be incorporated into the crystal in place of water molecules in the crystallization of linear polyethyleneimine or a polymer having the same, a chiral crystalline structure with excellent stability can be obtained. It is thought that. In the present invention, non-evaporable and optically active (chiral) L or D-tartaric acid is an acid-base complex while being bonded to a polymer having a linear polyethyleneimine skeleton in the same manner as a water molecule. Thus, the present invention has been completed.

[Polymer having linear polyethyleneimine skeleton (A)]
The polymer (A) having a linear polyethyleneimine skeleton used in the present invention may be a linear, star-like, or comb-like homopolymer, or a copolymer having other repeating units. good. In the case of a copolymer, the molar ratio of the linear polyethyleneimine skeleton in the polymer (A) is preferably 20% or more from the viewpoint that stable crystals can be formed. The repeating unit of the polyethyleneimine skeleton It is more preferable that the number is 10 or more.

As the polymer (A) having a linear polyethyleneimine skeleton, the higher the ability to form a crystalline aggregate, the more preferable. Therefore, it is preferable that the molecular weight corresponding to the linear polyethyleneimine skeleton portion is in the range of 500 to 1,000,000, whether it is a homopolymer or a copolymer. The polymer (A) having a linear polyethyleneimine skeleton can be obtained from a commercially available product or a synthesis method already disclosed by the present inventors (see the above-mentioned patent documents and non-patent documents).

[Optically active tartaric acid (B)]
As tartaric acid, commercially available D-tartaric acid and L-tartaric acid can be used alone, or a non-equal mixture of D-form and L-form (mixture of excess enantiomer) can be used. By selecting these optical isomers of tartaric acid, it is possible to control the structure of the resulting chiral crystal which is an acid-base complex of polymer / tartaric acid.

[Chiral crystal (X) which is an acid-base complex of polymer / tartaric acid]
The acid-base complex composed of the polymer and tartaric acid is a white powder. The powder is a particle having a particle size of 1 to 80 μm, and can be a particle having a particle size of 10 to 50 μm. At this time, the particles do not need to be perfect spheres, and may be elliptical or may have a shape in which a part of a plurality of spheres overlap. The particle diameter in the case of an ellipse refers to the longest part. When a plurality of spheres overlap, the longest part of each sphere is referred to as a particle diameter for convenience.

The internal structure of the polymer / tartaric acid acid-base complex particles can be changed depending on the type of tartaric acid used. That is, when D-tartaric acid or L-tartaric acid is used alone, a sheet-like nanostructure (nanosheet) of 1 to 50 nm is used as a basic skeleton, and this is a complex intertwined aggregate (see drawings). .

When tartaric acid (enantiomeric excess state) in which D-tartaric acid and L-tartaric acid are mixed at a non-equal ratio is used, granular crystals are formed, and a sheet of which one grain has a thickness of 1 to 50 nm is constant. It is characterized in that it has a multi-layered structure formed by overlapping at intervals of 5 to 30 nm.

In any case, the acid-base complex composed of polymer / tartaric acid absorbs a large amount of heat from a temperature of 100 ° C. or higher and does not exhibit a melting point in a single heating scanning range (up to 150 ° C. or lower) in DSC. And That is, although it is a crystal, dehydration occurs between carboxylic acid of tartaric acid and imine, and amidation proceeds.

In addition, regardless of the tartaric acid used, the crystal is characterized by showing a similar diffraction pattern regardless of the type of L-form or D-form of tartaric acid in XRD measurement.

[Isolation of chiral crystal (X) comprising acid-base complex]
The chiral crystal (X) comprising an acid-base complex can be obtained through the following steps.
(I) a step of preparing (Liquid I) in which a polymer (A) having a linear polyethyleneimine skeleton is dissolved in hot water;
(II) a step of preparing (II solution) in which optically active tartaric acid (B) is dissolved in hot water;
(III) (I liquid) and (II liquid) are mixed to form an acid-base complex of polymer (A) and optically active tartaric acid (B),
(IV) A step of precipitating a chiral crystal composed of an acid-base type complex by lowering the temperature of the mixed hot water solution containing the acid-base type complex obtained in (III).

As the polymer (A) having a linear polyethyleneimine skeleton, any of those described above can be used. By adding the polymer (A) powder to distilled water and heating it to 80 ° C. or higher, the polymer is obtained. A hot aqueous solution (solution I) is prepared. At this time, the concentration of the polymer (A) is preferably in the range of 0.5 to 8% by mass.

On the other hand, tartaric acid (B) powder having optical activity is added to distilled water and heated in the range of 80 to 100 ° C. to prepare a hot aqueous solution of tartaric acid (Part II). At this time, the concentration of tartaric acid (B) is preferably in the range of 1 to 15% by mass.

(I liquid) and (II liquid) obtained above are mixed and cooled from a temperature range of 80 to 100 ° C. At this time, the cooling method is not particularly limited, and may be a method of natural cooling in an air atmosphere or cooling by mixing with ice water to lower the temperature to room temperature or below. In this process, white powder is deposited. This powder is a chiral crystal (X) having chirality.

When mixing (I liquid) and (II liquid) which are hot aqueous solutions, the number of moles of ethyleneimine units (number of moles of amine functional group) in (liquid I) and the carboxylic acid functional group in (liquid II) It is most preferable that the ratio with respect to the number of moles is 1: 1, and when it is not equimolar, the excess range of any functional group is preferably within 10 mol%.

In addition, the liquid mixture may be left standing in the natural cooling process, or precipitation can be promoted by applying stirring or vibration. Furthermore, when ice water is added to the hot aqueous solution and cooled, precipitation of the chiral crystal (X) can be promoted by a method such as stirring.

The obtained white precipitate may be isolated as it is, or after washing with distilled water and drying at room temperature. Further, after washing with distilled water, it can be washed with an organic solvent such as ethanol, isopropanol, acetone, and dried.

The chiral crystal (X) obtained as described above is a solid circular dichroism spectrum (hereinafter referred to as a CD spectrum), and both can cause a negative cotton effect or a positive cotton effect of polarized light.

[Silica-based chiral nanostructure consisting of chiral crystal (X) and silica (Y)]
The structure of the chiral crystal (X) contains amino groups and carboxylic acid residues at high density. These two types of functional groups function as catalysts for the hydrolysis of alkoxysilanes and their condensation reactions. That is, the simultaneous presence of an amino group and a carboxylic acid residue is an effective catalyst for promoting the hydrolytic condensation reaction (sol-gel reaction) of silicate. Therefore, by mixing the chiral crystal (X) with the silica source (Y ′), the sol-gel reaction on the surface of the crystal (X) proceeds, and the chiral crystal (X) and the silica (Y) are separated. A composite silica-based chiral nanostructure (α) can be obtained.

In the above sol-gel reaction, since the chiral crystal (X) itself is used as a catalyst, it is considered that a chiral structure is induced in the skeleton of silica (Y) to be formed. That is, the chiral information in the chiral crystal (X) is transferred to the silica (Y) structure on which the chiral information is deposited, and chirality appears in the silica (Y) structure itself. That is, the chiral nanostructure according to the present invention is characterized in that not only the chirality is maintained in the internal organic component but also the silica (Y) catalyzed thereby is imparted with a chiral structure.

In order to obtain the silica-based chiral nanostructure (α) in the present invention, basically, a constant concentration of the chiral crystal (X) is dispersed in water, and a silica source (Y ′) solution is mixed therewith, and the mixture May be stirred for a certain time at room temperature.

The dispersion concentration in water of the chiral crystal (X) can be set to 0.5 to 15 wt%. Silica source (Y ′) is prepared as a liquid or an alcohol solution and mixed with chiral crystal (X).

As the silica source (Y ′), any alkoxysilane can be suitably used. The concentration of the alkoxysilane is adjusted in proportion to the concentration of the chiral crystal (X). When the concentration is low, the concentration of the alkoxysilane is also reduced. When the concentration is high, the concentration of the alkoxysilane is decreased. It is desirable to increase. In general, the amount of silica source (Y ′) used can be 2 to 50 times the number of moles of the amine of the polymer (A) in terms of silicon.

Examples of the alkoxysilane compounds include tetraalkoxysilanes, alkyltrialkoxysilanes, and dialkyl dialkoxysilanes.

Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and tetra-t-butoxysilane.

Examples of the silica source (Y ′) include condensates such as tetramethoxysilane tetramer silane (trade name MS-51 manufactured by Colcoat Co., Ltd.), tetraethoxysilane tetramer silane condensate. (Product name ES-51 manufactured by Colcoat Co., Ltd.) can be preferably used.

As the silica source (Y ′), tetraalkoxysilane and oligomers thereof are preferably used alone, but if necessary, other alkoxysilanes such as trialkoxysilane and dialkoxysilane are mixed and used. You can also.

Other alkoxysilanes include, for example, methyltrimethoxylane, methyltriethoxylane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxylane, n-propyltriethoxylane, iso-propyltrimethoxysilane , Iso-propyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyl Triethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptotriethoxysilane, 3,3,3-trifluoro Propyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxylane, p-chloro Examples thereof include methylphenyltrimethoxysilane, p-chloromethylphenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, and diethyldiethoxysilane.

Further, the silica-based chiral nanostructure (α) can contain 30 to 60 wt% of organic components as its composition. The organic component is combined with silica and embedded in the silica component.

[Silica-based chiral nanostructure (β) from which optically active tartaric acid (B) has been removed]
The silica-based chiral nanostructure (α) is composed mainly of three components of a polymer (A) having a linear polyethyleneimine skeleton, an optically active tartaric acid (B), and silica (Y). In the structure, since the polymer (A) and the silica (Y) are strongly physically bonded, only the optically active tartaric acid (B) component is included in the structure while the polymer (A) remains inside. The silica-based chiral nanostructure (β) containing the polymer (A) having a linear polyethyleneimine skeleton and silica (Y) as main components can be obtained by washing out (eluting) the body (α). In the present invention, the main component is a component other than impurities derived from the raw material, or a component that has not been sufficiently removed by elution or firing and has undergone modification or the like, unless the third component is intentionally used. Even if it enters, it means that it does not contain other ingredients.

For the selective removal of the optically active tartaric acid (B), a basic aqueous solution, an alcohol solvent and an acidic aqueous solution can be used. Specifically, the tartaric acid (B) component is converted into a silica-based chiral nanostructure (by immersing the silica-based chiral nanostructure (α) in the above solution or solvent and leaving it at room temperature, or heating the mixture. It can be easily obtained by extracting from α) and recovering the remaining solid component by filtration, centrifugation or the like.

As the basic aqueous solution, for example, an aqueous solution of a basic organic compound such as ammonia, triethylamine, diethylamine, ethylamine, ethylenediamine, or pyridine can be used. The concentration of these aqueous solutions may be 0.1 to 1 mol / L, and the actual amount used is suitable if it is excessive relative to the amount of tartaric acid (B) contained in the silica-based chiral nanostructure (α). However, in terms of the number of moles, it is desirable that the amount is 1.5 to 10 times equivalent. The time for immersing the silica-based chiral nanostructure (α) in the basic aqueous solution can be adjusted as appropriate within a range of 1 to 10 hours, but after immersing once, removing the supernatant and further immersing it twice or three times. By soaking, tartaric acid (B) can be completely removed.

Methanol, ethanol, ethylene glycol or the like can be used as the alcohol solvent. In that case, it is also suitable to mix an organic amine compound.

As the acidic aqueous solution, an aqueous solution of an inorganic acid such as an aqueous hydrochloric acid solution, an aqueous nitric acid solution, an aqueous sulfuric acid solution, or an aqueous phosphoric acid solution can be used. In this case, the acid concentration is preferably in the range of 0.1 to 5.0 mol / L. The polymer (A) having a linear polyethyleneimine skeleton easily dissolves in water when protonated with an inorganic acidic compound, but is insoluble when the pH value of the aqueous solution is 1 or less. Therefore, in order to prevent the polymer (A) component from flowing out, it is desirable to use a highly concentrated acidic aqueous solution.

After the tartaric acid (B) component is removed, the polymer (A) remains in the resulting silica-based chiral nanostructure (β), and the silica (Y) and the polymer (A) are combined. The complex also exhibits chirality.

In this silica-based chiral nanostructure (β), the content of the polymer (A) having a linear polyethyleneimine skeleton (that is, the organic component in the structure) is in the range of 5 to 30 wt%.

Silica-based chiral nanostructure (β) composed mainly of polymer (A) from which tartaric acid (B) component is removed and silica (Y) has a polarization rotation of positive cotton or negative cotton in the solid CD spectrum. Indicates. The direction of this deflection rotation is the same as that of the silica-based chiral nanostructure (α) before the tartaric acid (B) component is eluted, and the chirality is maintained by the elution, that is, the chirality in the structure (β) is maintained. It has a special spatial structure.

[Silica-based chiral nanostructure (γ) obtained by removing tartaric acid (B) and polymer (A)]
Tartaric acid (B) and polymer (A), which are organic components in the silica-based chiral nanostructure (α), are decomposed and removed by heating and firing the structure (α) in air. Thereby, the silica-type chiral nanostructure ((gamma)) which has a silica (Y) component as a main component can be obtained.

¡No special conditions are required for heating and removing the organic component, and it is sufficient to fire for a certain time in the temperature range where the organic component is decomposed in the electric furnace.

For example, the electric furnace firing temperature range can be set to 250 ° C. or higher and 1000 ° C. or lower. In view of efficiently removing the organic components, the heating temperature is desirably 400 ° C. or higher.

The heating and baking temperature decomposes and removes organic components, and at the same time, may cause a chemical bond change in the resulting silica-based chiral nanostructure (γ), so the surface area decreases with an increase in the baking temperature. Therefore, in order to obtain a high specific surface area, it is desirable to set appropriately according to the specific surface area requirement range by generally raising the firing temperature.

The heating and baking time may be approximately 1 to 4 hours, and it is desirable to shorten the time for high-temperature baking.

There is no change in the shape of the silica-based chiral nanostructure (γ) obtained after heating and baking, and the shape of the silica-based chiral nanostructure (α) such as nanofibers, nanoribbons, and nanosheets is maintained. The specific surface area of the silica-based chiral nanostructure (γ) after firing is in the range of 400 to 700 m ² / g, and exhibits a negative cotton or positive cotton effect of polarization in the solid CD spectrum. That is, the silica-based chiral nanostructure (γ) has a chiral spatial structure.

In addition, the removal of the organic component from the silica-based chiral nanostructure (α) can be performed by an acidic solution cleaning method other than heating and baking. That is, in order to selectively remove tartaric acid (B), a basic aqueous solution or a high concentration acidic aqueous solution is required as described above. To remove tartaric acid (B) and polymer (A) simultaneously, The organic component can be completely removed by repeatedly using a method of heating and washing in an acidic aqueous solution having a pH value of 3 to 5 at a temperature of 90 ° C. or lower.

The silica-based chiral nanostructure (α to γ) of the present invention is an aggregate of nanostructures such as nanofibers, nanoribbons, and nanosheets, and has a thickness or thickness in the range of 10 to 100 nm, and is long. The thickness is in the range of 200 nm to 10 μm, the appearance of the aggregate is close to a spherical body, and the size thereof is in the range of 1 to 20 μm.

Further, the silica-based chiral nanostructure (α to γ) of the present invention exhibits a positive cotton effect or a negative cotton effect because of a difference in light absorption with respect to left and right circularly polarized light in the CD spectrum. In other words, the silica-based chiral nanostructure (α to γ) can rotate left polarized light or right polarized light in a certain direction. The positive cotton effect or the negative cotton effect in the solid CD spectrum is determined by the optical activity of the tartaric acid (B) used as a raw material for synthesizing the silica-based chiral nanostructure (α to γ). When the body is mixed at a constant ratio other than equal amounts (ie, enantiomeric excess), the change in the degree of absorption of left circularly polarized light or right circularly polarized light occurs, so the positive and negative directions of the Cotton effect can be reversed. It is.

[Organosilane-modified silica-based chiral nanostructure]
The chemical structure of silica (Y) of the silica-based chiral nanostructure (α to γ) obtained above is basically represented by SiO ₂ . When these structures are brought into contact with a silane coupling agent, an O—Si—C bonding component is introduced into the silica (Y), and an organosilane-modified silica-based chiral nanostructure can be obtained.

Examples of the silane coupling agent that can be used here include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, and iso-propyl. Trimethoxysilane, iso-propyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycol Sidoxypropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltomethoxysilane, 3-mercaptotriethoxysilane, 3, , 3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane , P-chloromethylphenyltrimethoxysilane, p-chloromethylphenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxy Examples thereof include silane and tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane.

For contact with the silane coupling agent, the silane coupling agent is dissolved in a solvent such as chloroform, methylene chloride, cyclohexanone, xylene, toluene, ethanol, methanol, and the silica-based chiral nanostructure (α˜ A method of dispersing the powder of γ) and stirring the mixture for a certain time is preferable.

The concentration of the silane coupling agent is preferably 1 to 5% by mass, and more preferably 1 to 5% by mass with an aqueous ethanol solution of ammonia. The volume ratio upon mixing is preferably 5 to 10 times the amount of the aqueous ammonia solution relative to the silane coupling agent solution.

When the mixture is stirred for 2 hours or more, the residue of the silane coupling agent can be easily introduced into silica (Y). After stirring and mixing for a certain period of time, the obtained powder is filtered or centrifuged, and the solid content is washed with a solvent such as ethanol, methanol, acetone, toluene, chloroform, hexane, cyclohexane, etc., and dried at room temperature. By doing so, an organosilane-modified silica-based chiral nanostructure can be obtained.

The solid CD spectra of the structures modified with these organosilanes show a positive or negative cotton effect of polarization, and are in the same direction as the silica-based chiral nanostructure before contact.

In addition to the introduction of organosilane, the silica-based chiral nanostructure (α to γ) of the present invention and the structure modified with organosilane can be combined with various organic compounds to form silica. The surface of (Y) can also be modified. As the organic compound that can be used, various constituents ranging from high polymers to low molecules, for example, polar, nonpolar, cationic, and anionic organic compounds can be suitably used. These organic compounds may be pigments or luminescent materials.

In addition, an organometallic complex compound or an organometallic compound can be physically adsorbed on the silica-based chiral nanostructure (α to γ) of the present invention and a structure obtained by modifying this with a organosilane. The organic compound containing these metals is suitable even if it has a catalytic function. After they are adsorbed, the cotton effect in the solid CD spectrum can still be maintained, and in the absorption wavelength range of the adsorbed compound, the direction of the positive and negative cotton effect is basically unchanged.

Hereinafter, the present invention will be described more specifically with reference to examples and application examples, but the present invention is not limited to these examples. Unless otherwise specified, “%” represents “mass%”.

[Analysis by X-ray diffraction method]
Place the isolated and dried sample on the measurement sample holder, set it on a wide-angle X-ray diffractometer “Rint-Ultma” manufactured by Rigaku Corporation, Cu / Kα ray, 40 kV / 30 mA, scan speed 1.0 ° / min, Measurements were made under conditions of a scanning range of 10 to 70 °.

[Differential scanning calorimetry]
The isolated and dried sample is weighed with a measurement patch, set in a SII nano-technological differential scanning calorimetry measurement device (TG-TDA6300), and the temperature rise rate is 10 ° C / min. Measurements were made at

[Shape analysis by scanning electron microscope]
The isolated and dried sample was placed on a glass slide and observed with a surface observation device VE-7800 manufactured by Keyence Corporation.

[Shape analysis by transmission electron microscope]
The isolated and dried sample was placed on a carbon-deposited copper grid and observed with a Topcon Co., Ltd., EM-002B, Nolan Instruments Co., Ltd., VOYAGER M3055 high-resolution electron microscope.

[Specific surface area analysis by isotherm measurement of gas adsorption / desorption]
The sample was dried under reduced pressure at 300 ° C. for 3 hours or more, and then the specific surface area was measured using TriStar 3000 (manufactured by Micromeritics). The micropore area and the external surface area were calculated by the t-plot method.

[Chirality analysis by solid CD spectrum]
Circular dichroism was measured using a J-720 (manufactured by JASCO Corporation) equipped with a CD integrating sphere device (DRCD-466 powder CD measurement unit). A sample for CD measurement was prepared by mixing with potassium chloride.

Synthesis Example 1 [Synthesis of linear polyethyleneimine (LPEI)]
30 g of commercially available polyethyloxazoline (average molecular weight 50,000, average polymerization degree about 500, manufactured by Aldrich) was dissolved in 150 mL of 5M aqueous hydrochloric acid. The solution was heated to 90 ° C. in an oil bath and stirred at that temperature for 10 hours. Acetone 500 mL was added to the reaction solution to completely precipitate the polymer, which was filtered and washed with methanol three times to obtain white polyethyleneimine powder. When the obtained powder was identified by ¹ H-NMR (heavy water), peaks 1.2 ppm (CH ₃ ) and 2.3 ppm (CH ₂ ) derived from the side chain ethyl group of polyethyloxazoline completely disappeared. It was confirmed that That is, it was shown that polyethyloxazoline was completely hydrolyzed and converted to polyethyleneimine.

The powder was dissolved in 50 mL of distilled water, and 500 mL of 15% ammonia water was added dropwise to the solution while stirring. The mixture was allowed to stand overnight, the precipitated polymer crystals were filtered, and the crystals were washed 3 times with cold water. The washed crystal powder was dried in a desiccator at room temperature to obtain linear polyethyleneimine (LPEI). The yield was 22 g (containing crystal water). In polyethyleneimine obtained by hydrolysis of polyoxazoline, only the side chain reacts and the main chain does not change. Therefore, the degree of polymerization of LPEI is similar to about 500 before hydrolysis.

Example 1
[Silica-based chiral nanostructure (α-1) <SiO ₂ / LPEI / D-Tart>) in which a chiral crystal composed of D-tartaric acid and LPEI is combined with silica
316 mg of LPEI powder obtained in Synthesis Example 1 (4 mmol of ethyleneimine [EI] unit) was added to 4 g of distilled water and heated to about 95 ° C. to completely dissolve LPEI ([EI] = 1000 mM). Was prepared. On the other hand, 300 mg (2.0 mmol) of D-tartaric acid (D-Tart, manufactured by Tokyo Chemical Industry Co., Ltd.) powder was dissolved in 4.0 g of distilled water, and the solution was added to a hot aqueous solution of LPEI. The mixture solution (95 ° C.) was naturally cooled to room temperature (25 ° C.) to obtain a precipitate. The obtained precipitate was separated by centrifugation, washed and recovered with distilled water, and dried in the air for 3 days to obtain a powder. Yield was 477 mg.

From the XRD measurement of the obtained powder, it was found that this powder was a crystal (FIG. 1). From the solid CD spectrum measurement, it was found that this powder showed a negative cotton effect in the wavelength range of 210 to 240 nm (FIG. 2a). In the same wavelength range, the D-tartaric acid powder used alone as a raw material showed the opposite positive cotton effect (FIG. 2b). From these results, the obtained powder is a chiral crystal of an acid-base complex composed of the polymer LPEI and D-tartaric acid, and has a new structure composed of chiral tartaric acid and achiral LPEI. I understand that.

200 mg of the powder as the chiral crystal obtained above was dispersed in a mixed solution of water and tetramethoxysilane (TMOS) (water / TMOS = 20 mL / 3 mL) and stirred at room temperature (25 ° C.) for 1 hour. . The resulting precipitate was separated by centrifugation and washed with distilled water to recover a white solid. Yield was 405 mg.

From the solid ²⁹ Si-NMR measurement result of the obtained solid, it was confirmed that the solid contained basic bonded Si—O constituting silica (FIG. 3). Particularly, it was suggested that the Q ⁴ signal indicating Si (OSi) ₄ and the Q ³ bond indicating HOSi (OSi) ₃ are main bonds in the range of −100 ppm to −120 ppm.

Further, from the solid ¹³ C-NMR measurement of the obtained solid, in the solid, the peak of methylene carbon CH ₂ N derived from LPEI (44 ppm), the peak of hydroxycarbon HC—OH derived from tartaric acid (73 ppm), tartaric acid The carbonyl group carbon C = O peak (180 ppm) was confirmed (FIG. 4). This strongly suggests that, in addition to the silica structure, the chemical structure of LPEI and the chemical structure of tartaric acid coexist in the solid.

The solid CD spectrum of this solid is shown in FIG. A negative cotton effect having a peak top of about 220 nm ultraviolet absorption was exhibited. This is the same as the negative direction of the ellipticity of the LPEI / D-Tart chiral crystal before precipitating the silica. Since the complex of chiral LPEI / D-Tart crystal and silica derived thereby both strongly absorbs left-handed circularly polarized light, they are considered to retain left-handed chirality inside. From the above, it was confirmed that the composite with silica thus obtained was the silica-based chiral nanostructure (α-1) <SiO ₂ / LPEI / D-Tart> of the present invention.

In the SEM photograph of the obtained solid, it was confirmed that the solid was an assembly of nanofibers (FIG. 6). Moreover, from the TEM photograph (FIG. 7), the thickness of the nanofiber which is the basic unit of this aggregate was about 25 nm.

Example 2
[Silica-based chiral nanostructure (α-2) <SiO ₂ / LPEI / L-Tart>] in which a chiral crystal composed of L-tartaric acid and LPEI is combined with silica
In Example 1, chiral crystal LPEI / L-Tart and silica were prepared in the same manner as in Example 1 except that L-tartaric acid (L-Tart, manufactured by Tokyo Chemical Industry Co., Ltd.) powder was used instead of D-tartaric acid. A chiral nanostructure (α-2) <SiO ₂ / LPEI / L-Tart> was prepared.

FIG. 8 shows an XRD chart of the chiral crystal LPEI / L-Tart. Since the diffraction pattern is the same as that of the chiral crystal LPEI / D-Tart in Example 1, it can be confirmed that the crystal has the same crystal structure.

FIG. 9 is a solid CD spectrum of the chiral crystal LPEI / L-Tart. Due to the presence of L-tartaric acid, a positive cotton effect opposite to that in Example 1 was confirmed.

FIG. 10 is a solid-state ²⁹ Si-NMR spectrum of a silica-based chiral nanostructure (α-2) <SiO ₂ / LPEI / L-Tart> formed by complexing with silica. The peaks of Q ⁴ and Q ³ derived from the silica bond structure remarkably appear, and it can be confirmed that the structure has a silica structure.

FIG. 11 is a solid state ¹³ C-NMR spectrum of silica-based chiral nanostructure (α-2) <SiO ₂ / LPEI / L-Tart>. The methylene carbon derived from the LPEI skeleton, the hydroxymethine carbon derived from the tartaric acid structure, and the carbonyl carbon were confirmed.

FIG. 12 is a solid CD spectrum of silica-based chiral nanostructure (α-2) <SiO ₂ / LPEI / L-Tart>. The waveform of this spectrum showed a positive cotton effect that was just a mirror image of the silica-based chiral nanostructure (α-1) obtained in Example 1. In other words, the silica-based chiral nanostructure (α-2) <SiO ₂ / LPEI / L-Tart> produced using L-tartaric acid as a chiral source retains right-handed chirality. It is clear that L-tartaric acid and D-tartaric acid have transferred their respective chirality characteristics to silica.

13 and 14 show SEM and TEM photographs of the silica-based chiral nanostructure (α-2) <SiO ₂ / LPEI / L-Tart>. The structure was an aggregate of flower-like fibres, and the thickness of the nanofiber as the basic unit was around 25 nm.

Example 3
[Silica-based chiral nanostructure (γ-1) obtained by heating and removing organic components in silica-based chiral nanostructure (α-1)]
250 mg of the silica-based chiral nanostructure (α-1) <SiO ₂ / LPEI / D-Tart> prepared in Example 1 was placed in a ceramic crucible and heated to 600 ° C. in an electric furnace, and the temperature And left for 3 hours. From the TEM observation of the silica-based chiral nanostructure (γ-1) thus obtained, the nanofibre structure was confirmed (FIG. 15). The specific surface area (BET) of the silica-based chiral nanostructure (γ-1) was 665 m ² / g, of which the surface area derived from μ pore was 553 m ² / g, and the area derived from a simple outer surface was 112 m ² / g.

From the solid CD spectrum of the silica-based chiral nanostructure (γ-1) (FIG. 16), a negative cotton effect in the absorption wavelength range derived from the silica structure O—Si—O was confirmed. This suggests that the chiral spatial structure that selectively absorbs left-handed circularly polarized light is firmly engraved in the silica-based chiral nanostructure (γ-1).

Furthermore, after the porphyrin dye was adsorbed to this silica-based chiral nanostructure (γ-1), the solid CD spectrum of the powder was measured, and the negative cotton effect in the range of the Soret band absorption wavelength (around 400 nm) of porphyrin was measured. Was confirmed (FIG. 17). That is, the achiral porphyrin dye does not show any waveform in the CD spectrum, but it is adsorbed in the spatial structure of the chiral silica-based chiral nanostructure (γ-1), so that the porphyrin has an asymmetric structure. A behaving induced CD appeared. It was strongly suggested that a chiral silica structure and an achiral organic compound form a new asymmetric structure.

Example 4
[Silica-based chiral nanostructure (γ-2) obtained by heating and removing organic components in silica-based chiral nanostructure (α-2)]
250 mg of the silica-based chiral nanostructure (α-2) <SiO ₂ / LPEI / L-Tart> prepared in Example 2 was placed in a ceramic crucible and heated at 600 ° C. in an electric furnace at that temperature. Left for 3 hours. From the TEM observation of the silica-based chiral nanostructure (γ-2) thus obtained, a nanofibrar structure was confirmed (FIG. 18). The specific surface area (BET) of the silica-based chiral nanostructure (γ-2) was 653 m ² / g, of which the surface area derived from μ pore was 549 m ² / g, and the area derived from a simple outer surface was 104 m. ² / g.

In the solid CD spectrum of the silica-based chiral nanostructure (γ-2) obtained by calcination, a positive cotton effect appeared, which was exactly a mirror image relationship with the result of Example 3 (FIG. 19).

Furthermore, after the porphyrin dye was adsorbed to this silica-based chiral nanostructure (γ-2), the solid CD spectrum of the powder was measured, and the positive cotton effect in the range of the Soret band absorption wavelength (around 400 nm) of porphyrin was measured. Was confirmed (FIG. 20). This was a mirror image relationship as a result of Example 3. That is, an achiral porphyrin dye is adsorbed in the spatial structure of a chiral silica structure, and an induced CD appears in which the porphyrin behaves like an asymmetric structure. It was strongly suggested that chiral silica and achiral organic compounds form a new asymmetric structure.

Example 5
[Organic Silane Modified Silica-Based Chiral Nanostructure-1]
200 mg of the silica-based chiral nanostructure (γ-1) obtained in Example 3 above was mixed with a toluene solution (200 mg) of phenyltrimethoxysilane (1.0 mmol) and refluxed for 6 hours in a nitrogen atmosphere to obtain organosilane-modified silica. The system chiral nanostructure-1 was obtained. From the results of TG-TDA analysis, it was found that the amount of phenyl group introduced was 0.67 mmol / g. As a result of measuring the solid CD spectrum of this powder, a negative cotton effect was confirmed in the ultraviolet absorption wavelength range (190-230 nm) of the C═C bond of the aromatic ring (FIG. 21). This suggests that the phenyl group is bound to the silica wall that constitutes the chiral spatial structure.

Example 6
[Organic Silane Modified Silica-Based Chiral Nanostructure-2]
200 mg of the silica-based chiral nanostructure (γ-2) obtained in Example 4 above was mixed with a toluene solution (200 mg) of phenyltrimethoxysilane (1.0 mmol) and refluxed in a nitrogen atmosphere for 6 hours to obtain organosilane-modified silica. The system chiral nanostructure-2 was obtained. From the results of TG-TDA analysis, it was found that the amount of phenyl group introduced was 0.64 mmol / g. As a result of measuring the solid CD spectrum of this powder, a positive cotton effect was confirmed in the ultraviolet absorption wavelength range (190-230 nm) of the C═C bond of the aromatic ring (FIG. 22). This suggests that the phenyl group was bonded to the silica wall constituting the chiral spatial structure.

Example 7
[Silica-based chiral nanostructure in excess of enantiomer (α-3) <SiO ₂ / LPEI / ee-Tart>]
158 mg of the LPEI powder obtained in Synthesis Example 1 was added to 3 g of distilled water and heated to about 95 ° C. to prepare an aqueous solution in which LPEI was completely dissolved. On the other hand, a mixed powder of D-tartaric acid (120 mg) and L-tartaric acid (30 mg) was dissolved in 3.0 g of distilled water, and the solution was added to a hot aqueous solution of LPEI. The mixture solution (95 ° C.) was naturally cooled to room temperature (25 ° C.) and crystallized. The precipitate was washed and collected by centrifugation, and dried in the air for 3 days to obtain a powder composed of LPEI and D, L-tartaric acid (ee).

From the XRD measurement of this powder, it was confirmed that this complex was a crystal (FIG. 23). From the solid CD spectrum measurement (FIG. 24), it was found that this crystalline powder exhibited a negative cotton effect in the wavelength range of 210 to 240 nm, confirming that it was a chiral crystal.

200 mg of this chiral crystal was dispersed in a mixed solution of water and tetramethoxysilane (TMOS) (water / TMOS = 20 mL / 3 mL) and stirred at room temperature for 1 hour. The solid was separated with a centrifuge and washed with distilled water to recover a white solid. The yield was 396 mg.

The solid CD spectrum result of this solid is shown in FIG. A negative cotton effect having a peak top of about 220 nm ultraviolet absorption was exhibited. This was the same as the negative orientation of the ellipticity of the chiral crystal LPEI / D excess L-Tart before complexing with silica. Even when the D form is in excess of the L form, the chiral structure can be engraved into the spatial structure of silica, confirming that it is a silica-based chiral nanostructure (α-3).

In the SEM photograph of the obtained silica-based chiral nanostructure (α-3), it was confirmed that the structure was an assembly of nanofibers (FIG. 26).

Comparative Example 1
[Silica-based nanostructure <SiO ₂ / LPEI / (±) -Tart> formed by combining an acid-base complex crystal composed of racemic tartaric acid and LPEI and silica]
316 mg of LPEI powder obtained in Synthesis Example 1 (4 mmol of ethyleneimine [EI] unit) was added to 4 g of distilled water and heated to about 95 ° C. to completely dissolve LPEI ([EI] = 1000 mM). Was prepared. On the other hand, a mixed powder of D-tartaric acid (150 mg) and L-tartaric acid (150 mg) (total number of moles: 2.0 mmol) was dissolved in 4.0 g of distilled water, and the racemic solution was added to a hot aqueous solution of LPEI. The mixture solution (95 ° C.) was naturally cooled to room temperature (25 ° C.) and crystallized. The precipitate was washed and collected by centrifugation, and dried in the air for 3 days to obtain a powder. The yield was 472 mg.

From the XRD measurement of this powder, it was confirmed that it was a crystal (FIG. 27). However, solid CD spectrum measurement of this crystal revealed that there was no change in ellipticity and no chiral waveform appeared.

200 mg of this crystal was dispersed in a mixed solution of water and tetramethoxysilane (TMOS) (water / TMOS = 20 mL / 3 mL) and stirred at room temperature for 1 hour. The solid was separated and washed with a centrifuge, and a white solid was recovered. The yield was 402 mg.

The ²⁹ Si-NMR and ¹³ C-NMR spectra of this solid are shown in FIGS. 28 and 29, respectively. From these results, it was confirmed that this composite was composed of three components of silica, LPEI, and tartaric acid. However, in the solid CD spectrum of the solid (FIG. 30), there was no waveform change and no chirality. Furthermore, after the porphyrin dye was adsorbed to the solid, the solid CD spectrum was measured, but no change in the ellipticity waveform appeared even in the porphyrin absorption wavelength range (FIG. 31). That is, in the silica-based nanostructure <SiO ₂ / LPEI / (±) -Tart> prepared using racemic tartaric acid, there may be a possibility that individual asymmetric spatial structures may be formed. It was revealed that the structure does not become a structure showing optical activity. FIG. 32 shows an SEM photograph of the structure.

Example 8
[Silica-based chiral nanostructure (α-1) obtained by removing tartaric acid from <SiO ₂ / LPEI / D-Tart>]
500 mg of the silica-based chiral nanostructure (α-1) obtained in Example 1 was added to 20 mL of 1% NH ₃ aqueous solution, allowed to stand at room temperature for 30 min, and collected by centrifugation. This operation was performed 4 times, and finally washed twice with distilled water and once with 2-propanol. Drying under reduced pressure at 40 ° C. gave 266 mg of white powder. As a result of FT-IR spectrum measurement of the obtained powder (FIG. 33), the vibration of tartaric acid derived from COOH (FIG. 33a) disappeared (FIG. 33b), and the silica-based chiral nanostructure (β-1) of the present invention It was confirmed that. This structure (β-1) and an aqueous copper nitrate solution were mixed to coordinate a copper ion to LPEI, and then measured by a solid CD spectrum. From the result of FIG. 34a, a strong negative cotton effect appeared in the copper complex absorption wavelength range (strong absorption around 250 nm).

Example 9
[Silica-based chiral nanostructure (α-2) obtained by removing tartaric acid from <SiO ₂ / LPEI / L-Tart>]
A silica-based chiral nanostructure (β-2) was obtained in the same manner as in Example 8 except that the silica-based chiral nanostructure (α-2) obtained using L-tartaric acid as tartaric acid was used. After copper ions were coordinated to LPEI in the same manner as in Example 8, it was measured with a solid CD spectrum. From the result of FIG. 34b, a strong positive cotton effect appeared in the copper complex absorption wavelength range (strong absorption around 250 nm).

Comparative Example 2
[Silica-based nanostructure obtained by removing tartaric acid from <SiO ₂ / LPEI / (±) -Tart>]
Tartaric acid was removed in the same manner as in Example 8 using the silica-based nanostructure <SiO ₂ / LPEI / (±) -Tart> obtained in Comparative Example 1. Furthermore, after coordinating copper ions to this in the same manner as in Example 8, it was measured by a solid CD spectrum. From the result of FIG. 34c, there was no change in the ellipticity waveform in the copper complex absorption wavelength range (strong absorption around 250 nm). This is a completely different result from Examples 8 and 9.

Example 10
[Silica-Based Chiral Nanostructure (α-1) <Silica-Based Chiral Nanostructure (γ-3) Obtained from High-Temperature Firing of <SiO ₂ / LPEI / D-Tart>]]
A silica-based chiral nanostructure (α-1) was prepared by the method of Example 1, 250 mg of the powder was placed in a ceramic crucible, heated to 900 ° C. in an electric furnace, and 2 ° C. at that temperature. Left for hours. The silica-based chiral nanostructure (γ-3) thus obtained had a specific surface area (BET) of 402 m ² / g, of which the μ-pore-derived surface area was 317 m ² / g, derived from a simple outer surface. The area of was 86 m ² / g. Compared with the baking at 600 ° C. in Example 3, the surface area tended to decrease. That is, it is considered that the internal space of silica was reduced at a high temperature of 900 ° C.

The structure powder is mixed with a chloroform solution of 2-methyl-1,4-naphthoquinone to adsorb 2-methyl-1,4-naphthoquinone to a silica-based chiral nanostructure (γ-3), and then the solid powder CD spectra were measured (FIGS. 35a and 35b). For comparison, the solid CD spectrum of 2-methyl-1,4-naphthoquinone powder was also measured (FIG. 35c). Even after baking at 900 ° C., after the adsorption of the 2-methyl-1,4-naphthoquinone molecule, the same induced CD spectrum appears remarkably even when the measurement sample cell fixing angle is 0 or 90 °, and the ultraviolet of quinone appears. It became clear that it was a negative cotton effect in the absorption wavelength range. Without chiral silica, there was no CD waveform change with 2-methyl-1,4-naphthoquinone alone. These results strongly suggest that the silica-based chiral nanostructure (γ-3) has extremely high heat resistance.

Claims

(1) A step of mixing an aqueous solution of a polymer (A) having a linear polyethyleneimine skeleton with an aqueous solution of optically active tartaric acid (B) to obtain an acid-base complex chiral crystal (X),
(2) In the presence of the chiral crystal (X) obtained in the step (1), a silica source (Y ′) is subjected to a sol-gel reaction to transfer the chiral structure of the chiral crystal (X) (silica) Coating the chiral crystal (X) with Y),
A method for producing a silica-based chiral nanostructure, comprising:
(1) A step of mixing an aqueous solution of a polymer (A) having a linear polyethyleneimine skeleton with an aqueous solution of optically active tartaric acid (B) to obtain an acid-base complex chiral crystal (X),
(2) In the presence of the chiral crystal (X) obtained in the step (1), a silica source (Y ′) is subjected to a sol-gel reaction to transfer the chiral structure of the chiral crystal (X) (silica) Coating the chiral crystal (X) with Y),
(3) a step of eluting the optically active tartaric acid (B) with an acidic or basic aqueous solution;
A method for producing a silica-based chiral nanostructure comprising a polymer (A) having a linear polyethyleneimine skeleton and silica (Y) having a chiral spatial structure.
(1) A step of mixing an aqueous solution of a polymer (A) having a linear polyethyleneimine skeleton with an aqueous solution of optically active tartaric acid (B) to obtain an acid-base complex chiral crystal (X),
(2) In the presence of the chiral crystal (X) obtained in the step (1), a silica source (Y ′) is subjected to a sol-gel reaction to transfer the chiral structure of the chiral crystal (X) (silica) Coating the chiral crystal (X) with Y),
(3 ′) a step of firing the composite obtained in the step (2) to remove organic components;
A method for producing a silica-based chiral nanostructure, characterized by having a chiral spatial structure in a silica skeleton.
The silica-based chiral nanostructure obtained by the production method according to any one of claims 1 to 3,
(4) a step of contacting with a silane coupling agent;
A process for producing an organosilane-modified silica-based chiral nanostructure, wherein an O—Si—C bond is introduced into silica (Y) having
In the step (1), the molar ratio of the amine functional group in the polymer (A) having a linear polyethyleneimine skeleton to the carboxylic acid functional group in the optically active tartaric acid (B) is 1: 1. The method for producing a silica-based chiral nanostructure according to any one of claims 1 to 4, which is used.
The method for producing a silica-based chiral nanostructure according to any one of claims 1 to 5, wherein the photochemically active tartaric acid (B) is D-tartaric acid, L-tartaric acid, or enantiomerically excess tartaric acid.
The method for producing a silica-based chiral nanostructure according to any one of claims 1 to 6, wherein the shape of the silica-based chiral nanostructure is an aggregate of nanofibers or nanosheets.
A silica-based chiral nanostructure obtained by the production method according to any one of claims 1 to 7.
The silica-based chiral nanostructure according to claim 8, which has a positive or negative cotton effect in a solid circular dichroism spectrum.