JP2000290099A - Asymmetric surface structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To build a two-dimensional asymmetric structure created by the arrangement of molecules on a solid surface by fixing the molecules having the asymmetric structure by a self-organization method to the solid surface, thereby causing the molecules to be bonded to the solid in a monomolecular layer by a chemical reaction. SOLUTION: The surface structure having an asymmetric surface structure having the mirror image relation with this asymmetric surface structure and a domain having the one asymmetric surface structure and a domain having another asymmetric surface structure having the mirror image relation therewith may be obtained. The solid surface is a metallic surface, more preferably a gold (III) surface. The molecules can be asymmetric molecules or an optically active asymmetric compound. The optically active asymmetric compound is preferably binaphthothiol (BNSH) (1,1'-Binaphthalene 2,2'-ditchiol). The fixation is preferably effected by the self-organization method and an immersion aqueous solution containing the molecules to be used is preferably made basic by potassium hydroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an asymmetric surface structure having a two-dimensional asymmetric structure formed by an arrangement of molecules on a solid surface. And the asymmetric surface structure. The present invention also relates to a method for producing such an asymmetric surface structure. The asymmetric surface according to the present invention can be provided as a novel material in research on asymmetric electrode reaction systems and catalytic reaction systems, and contributes to the progress and development of such research.

[0002]

2. Description of the Related Art There have been many studies aimed at selective synthesis of asymmetric organic compounds in electrodes and catalytic reactions, that is, asymmetric propagation, but one-to-one interaction between asymmetric molecules modified on a solid surface and a reaction substrate. Most are based on action (Fig. 1
reference). For example, an example in which the catalyst surface is modified with an asymmetric compound (Blaser, H.-U. & Muller, M. in Heterogeneous Cata
lysis and Fine Chemicals II (eds. Guisnet, M.) 73
(Elsevier Science Publishers BV, Amsterdam, 1991
And Blaser, H.-U.Enantioselective Synthesis Using
Chiral Heterogeneous Catalysts. Tetrahedron: Asym
Measurement, 843-866 (1991)), or an example in which the electrode is modified with an asymmetric compound (Watkins, BF, Behling, J. et al.
R., Kariv, E. & Miller, LLA Chiral Electrode. J.
Am. Chem. Soc. 97, 3549-3550 (1975) and Komori, T. &
Nonaka, T. Stereochemical Studies of the Electrolyt
ic Reactions of Organic Compounds. 25. Electroorga
nicReactions on Organic Electrodes. 6. Electrochem
ical Asymmetric Oxidationof Unsymmetric Sulfides t
o the Corresponding Chiral Sulfoxides on Poly (amin
o acid) -coated Electrodes. J. Am. Chem. Soc. 106, 265
6-2659 (1984)), but does not have a two-dimensional asymmetric structure formed by the arrangement of molecules as in the present invention, that is, an asymmetric surface.

It has been reported that an asymmetric surface has been formed (Bi
nnes, R., Gedanken, A. & Margel, S. Self-assembled
monolayer coatings as a new tool for the resolutio
n of recemates, Tetrahedron Lett. 38, 1285-1288 (1
994), Muskal, N., Turyan, I., Shurky, A. & Mandler,
D.Chiral Self-Assembled Monolayers. J.Am.Chem.So
c. 117, 1147-1148 (1995) and Inose, Y., Moniwa,
S., Aramata, A., Yamagishi, A. & Kyaw-Naing Chiral
monolayer of self-assembled Δ- [Os (bpy) ₂ L (Cl)]
⁺ [bpy = 2,2'-bipyridyl, L = 1,2-bis- (4-pyridyl) ethan
e] on a platinum electrode. Chem. Commun. 111-112
(See (1997)), but the asymmetric surface has been imagined but not confirmed.

A structure in which an asymmetric molecule is physically adsorbed in a monolayer on a solid surface is subjected to STM (scanning tunneling microscope).
Although there are examples observed by scanning tunneling microscopy), their structures cannot be used in asymmetric electrode or catalytic reaction systems because their molecules are not covalently fixed to solids (Walba , DM, Stevens, F., Cla
rk, NA & Parks, DCDetecting Molecular Chiralit
y by Scanning Tunneling Microscopy. Acc.Chem.Res.
591-597 (1996), Eckhardt, CJ, Peachey, NM, Swan
son, DR, Takacs, JM, Khan, MA, Gong, X., Ki
m, J.-H., Wang, J. & Uphaus, RASeparation of chi
ral phases in monolayer crystals ofracemic amphiph
iles.Nature 362, 614-616 (1993), Yamagishi, A., G
oto, Y. & Taniguchi, M. Stereochemical Effects on
Monolayer Formation of [Ru (dpp) ₃ ] ²⁺ (dpp = 4,7-Diphe
nyl-1,10-phenanthroline) at an Air-Water Interfac
e. J. Phys. Chem. 100, 1827-1832 (1996), Fang, H., G
iancarlo, LC & Flynn, GWDirect Determination of
the Chirality of Organic Molecules by Scanning Tu
nneling Microscopy.J.Phys.Chem.B 102, 7311-7315
(1998), Lopinski, GP, Moffatt, DJ, Wayner, D.
DM & Wolkow, RADetermination of the Absolute Ch
irality of Individual Adasorbed Molecules Using th
e ScanningTunneling Microscope.Nature 392, 909-91
1 (1998), Charra, F. & Cousty, J. Surface-Induced Ch
irality in a Self-Assembled Monolayer of Dicotic L
iquid Crystal.Phys.Rev.Lett. 80, 1682-1685 (1998)
, And Kunitake, M., Miyano, S. & Itaya, K. Highly
Ordered Adlayes of Optically Active Molecules, 1,
1'-Binaphthy-2,2'-dicarboxylic Acid: In Situ STM
study. International Conference on Electrochemist
ry of Ordered Interfaces, PB14 (Sapporo, 1998)).

When a metal such as gold is immersed in a solution of a molecule having a sulfur atom such as a thiol group or a disulfide group, a self-assembling method in which the molecule is fixed to the metal by a covalent bond is known. It is known (see FIG. 2), and the stability and potential of the functionalized surface of its self-assembled monolayer has already been reported (Ulman, A. Formation and Structure
of self-assembled monolayers.Chem.Rev. 96, 1533-15
54 (1996)).

As an asymmetric compound having an optically active axis having a thiol group, binaphthothiol (BNSH;
(R) or (C) -1,1'-Binaphthalene-2,2'-dithio
l) is known and its synthesis has been reported (Fab
bri, D., Delogu, G. & De Lucchi, O. Preparation of
Enantiomerically Pure 1,1′-Binaphthalene-2,2′-di
oland 1,1'-Binaphthalene-2,2'-dithiol. J.Org.Che
m. 58, 1748-1750 (1993) and FIG. 3).

[0007]

SUMMARY OF THE INVENTION As mentioned above,
As shown in FIG. 1, the selective synthesis of asymmetric organic compounds in the prior art, that is, asymmetric growth, is based on a one-to-one interaction between an asymmetric molecule modified on a solid surface and a reaction substrate. . Therefore, a two-dimensional asymmetric structure, which is useful in asymmetric electrode reaction systems or asymmetric catalytic reaction systems, where the arrangement of molecules rather than the chirality of the molecules themselves forms on the solid surface, that is, the construction of an asymmetric surface and There is still a need / issue to develop a new asymmetric reaction used.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, succeeded in constructing an asymmetric surface for the first time, and completed the present invention. Reached. The present inventors have proposed S
According to the TM image and asymmetric in-surface array modeling, binaphthothiol such as optical activity forms a regular two-dimensional structure on the gold (111) surface, and the structures formed by the R-form and the S-form are mirror images, respectively. That is, they discovered that an asymmetric surface was constructed, and confirmed this for the first time. As far as the inventors of the present application can know, there has been no report of an example in which an asymmetric molecule is immobilized on a surface by a covalent bond and the asymmetric two-dimensional structure created by the immobilization is directly observed. The asymmetric surface according to the invention of the present application is a novel structure obtained by the inventors of the present invention after intensive studies.

According to one aspect of the present invention, there is provided an asymmetric surface structure having a two-dimensional asymmetric structure formed by arrangement of molecules on a solid surface, wherein the molecules are formed into a monolayer by a chemical reaction. The asymmetric surface structure is provided which is bound to a solid. Also, an asymmetric surface structure having a mirror image relationship with the asymmetric surface structure, and a surface structure comprising a domain having one asymmetric surface structure and a domain having another asymmetric surface structure having a mirror image relationship with the domain. Is also provided. The solid surface can be a metal surface, preferably a gold (111) surface. The molecule can be an asymmetric molecule or an optically active chiral compound, and the optically active chiral compound is preferably binaphthothiol (BNSH) (1,1 ′).
-Binaphthalene-2,2'-dithiol).

In another embodiment of the present invention, there is provided a method for producing the above-mentioned asymmetric surface structure, comprising the following steps: wherein the arrangement of the above-mentioned molecules has an area sufficient to form the above-mentioned two-dimensional asymmetric structure. The method is provided, wherein the solid surface is provided with and the molecule is immobilized on the solid surface by a chemical reaction. The fixation can preferably be performed by a self-assembly method, and the immersion solution containing the molecule used in the self-assembly method can be preferably basic. As the solvent of the immersion solution,
Preferably ethanol is used and the soaking solution can be made basic with potassium hydroxide.

As a method for immobilizing a molecule on a solid surface,
A self-assembly method was used. The self-assembly method is a method in which when a metal such as gold is penetrated into a solution of a molecule having a sulfur atom such as a thiol or disulfide group as described above, the molecule is fixed on a solid surface by a chemical reaction. It is. For a solid surface, it can be any suitable metal. FIG. 2 shows the principle of the self-assembly method. In the figure, a reaction formula between gold and a thiol compound as a solid surface is also shown. The molecule immobilized on the solid surface can be a suitable molecule for a self-assembly method having an asymmetric structure. However, as a chiral molecule having a thiol group, binaphthothiol (BNSH) is preferable. It is. The structure of BNSH is shown in FIG. BNSH is an axially chiral compound having no chiral center but axial chirality. BNSH
Can be introduced from commercially available binaphthol, and a thiol group can be introduced into it using the above-mentioned synthesis method.
When the R-form and the S-form are separately synthesized and used as a racemic form, a mixture obtained by mixing equal amounts of both can be used. Further, a DNS molecule obtained by oxidizing a thiol group of the obtained BNSH to obtain a disulfide can also be synthesized by a conventional technique.

As the solid surface, a Clavier method (Clavil method) is used.
ier, J. Preparation of Monocrystalline Pt Microelec
trodes and Electrochemical Study of the Plane Surf
acesCut in the Direction of ｛111｝ and ｛100｝ Pla
nes. J. Electroanal. Chem. 107, 205-209 (1980)) (111) facet (facet)
Can be used, but the present invention is not limited to this.

[0013]

EXAMPLE 1 Fixation of BNSH to gold (111) facet A gold (111) cut surface prepared by the Clavier method was used for BNS.
FIG. 4 shows the results of electrochemical measurement and cyclic voltammetry (CV) performed in a potassium hydroxide solution after immersion in a solution of H and DNS for 1 hour, followed by washing and drying. In the electrode (a) treated with the DNS solution, when the potential was scanned toward the cathode, reductive desorption peaks were observed at around -800 mV and around -900 mV. An electrode obtained by treating the same gold electrode with an aqueous solution of sodium sulfide (c)
As compared with the CV of the electrode (a), the behavior of reductive desorption was almost the same, and it was found that only sulfur, not DNS molecules, was adsorbed on the gold (111) cut surface in the electrode (a). On the other hand, in the CV of the electrode (b) treated with the BNSH solution, a peak appeared at about -600 mV probably due to the desorption of BNSH, and a peak was also seen at about -900 mV, so that sulfur was also found. It was found that it was adsorbed.

[0014] Prof. Taniguchi et al. Of Kumamoto University have reported that the immersion solution in the self-assembly method may be made basic in order to perform selective modification with a target molecule (Taniguchi, I. et al. , Yoshimoto, S., Yoshida, M., Kobay
ashi, S., Miyawaki, T., Aono, Y., Sunatsuki, Y. &
Taira, H. Electrochim. Acta in press). Therefore, in accordance with this suggestion, potassium hydroxide was added to an immersion solution of BNSH in ethanol to a concentration of 10 mM in order to avoid the adsorption of sulfur as described above. The result of the CV of the obtained gold electrode is shown in FIG. In the figure, in order from the top, (a) R-form of BNSH,
(B) CV of the electrode treated with the S form of BNSH and (c) the racemic form of BNSH. In the case where the potassium hydroxide concentration was low (FIG. 4), around -800 mV and -9
The sulfur peak around 00 mV disappeared, and a reduction wave having two peaks around -660 mV and around -690 mV was observed. The shapes of these reduction waves were almost the same in the R-form and the S-form, but in the racemic form, a larger peak on the negative side (around -690 mV) appeared.

The amount of electricity flowing during the reductive elimination of BNSH was about 30 μC / cm ² in any of the R-form, S-form and racemic form. Sulfur atom in one molecule 2
Assuming that the individual forms a bond with the gold atom on the surface, the surface density of the modifying molecule is determined to be approximately 1.0 × 10 ¹⁴ / cm ² . This value corresponds to a calculated occupied area per molecule of about 1 nm ² , and substantially coincides with the adsorption cross section of the BNSH molecule estimated from the model shown in the lower part of FIG. Therefore, it is considered that the BNSH molecule forms a densely packed monolayer on the gold surface. Also, DN
Also in the case of S treatment, when potassium hydroxide was added to the immersion solution, the same CV results as in the case of BNSH (FIG. 5) were obtained (not shown).

Example 2: STM observation result of BNSH-modified solid surface STM of BNSH-modified gold surface obtained in Example 1
Observations were made. FIG. 6 shows the results. The device is Nanos
Cope E and pico SPM were used. A platinum iridium wire cut as a probe, 200 to 500 mV as a bias voltage, and 500 as a tunnel current
８００800 pA was used. A step line intersecting at about 60 degrees characteristic of the gold (111) facet was seen, and also the presence of a terrace with an area on the order of 500 nm square was confirmed (results not shown).

An STM observation of the BNSH-modified gold surface obtained under the same conditions as in Example 1 was performed. That is, using an ethanol solution containing 10 mM potassium hydroxide as an immersion solution and about 1 μM BNSH, immersing for about 10 minutes, rinsing well with ethanol, and drying, and performing STM observation in the atmosphere. Was. Fig. 7 shows the results.
Shown in The results for the R-form are shown, but almost the same STM image was obtained for the S-form. From FIG. 7, it can be seen that an aggregated portion of molecules having no regularity and a domain having regularity are mixed. The domain in which the regularity was recognized had a width of about 20 nm square. An enlarged version of such a domain is shown at the bottom of FIG.

FIG. 8 is an STM image in which the R-domain and the S-domain are enlarged. It can be seen that the arrangement of bright round grains and the black portions that seem to be voids are regularly arranged. The round particles correspond to the size of one naphthalene ring of BNSH. The unit cell of this two-dimensional structure has a side of 1.6 nm.
It was a rhombus of degree. From a different point of view, it can be regarded as a combination of a triangle including six round grains and the above-described holes. As shown in the left part of FIG. 8, in the case of the R body, the positional relationship of the three triangles surrounding the holes was all counterclockwise in the domain of the R body. On the other hand, as shown in the right part of FIG.
That is, it was clockwise.

The gold surface was modified with a racemic BNSH under the same conditions as those for the R-form and S-form of BNSH. FIG. 9 shows the results. The same domain structure as that obtained by treatment with R-form or S-form alone was confirmed. However, the size of those domains is approximately 1 on average
R is about several nm square, at most about 25 nm square.
Smaller than when treated with the body or S body alone, and
It turns out that the number of domains is also small.

As described above with reference to the CV results shown in FIG. 5, the peaks in the R-form and the S-form are different from the peaks in the racemic form. Assuming that the separation potential is different, the peak on the positive side (around -660 mV) is due to a regular structure, and the peak on the negative side (around -690 mV).
Can be considered to be due to a structure having no regularity. Therefore, the CV results shown in FIG. 5 and the STM results shown in FIGS. 7 and 9 do not contradict each other and support the existence of the asymmetric surface.

FIG. 10 shows a portion where the R-domain and the S-domain are adjacent to each other. The angle between the straight lines connecting the holes in both domains was about 20 degrees. On the other hand, in the portion where the R-form domains or the S-form domains are adjacent to each other, the straight lines were parallel (results not shown).

FIG. 11 is an STM image showing the relationship between a straight line (white line) connecting holes in the R-body domain and the S-body domain and a gold step line (black line). In the case of R body,
The angle was about 10 degrees, whereas the S-body had an angle of about 10 degrees in the opposite direction. The result is BNSH
This indicates that the arrangement of molecules is regulated by the arrangement of gold atoms on the surface.

[0023]

EFFECT OF THE INVENTION A model of asymmetric surface arrangement (theoretical interpretation)
And sulfur atom effect BNSH of the present invention is thought to be fixed to the 3-fold hollow site surface gold atoms (Ulman, A.Formati
on and Structure of self-assembled monolayers.Che
m. Rev. 96, 1533-1554 (1996)). BNS
The distance between adjacent sulfur atoms in H is 94 degrees when the angle between two naphthyl groups in BNSH is slightly greater than the angle between two naphthyl groups in unsubstituted binaphthyl (68 degrees). Distance between two thiol groups (0.40-0.
45 nm) (Ann, K. & Robinson, JM
Crystal and Molecular Structure of 1,1'-Binaphty
l. J. Chem. Soc. (B) 1146-1149 (1968)). As shown in FIG. 11 earlier, a straight line connecting holes in the R-body domain and the S-body domain and gold (111)
Crosses at an angle of about 10 degrees. The triangle shown in FIG. 12 has a side of about 1.62 nm and gives about 1.3 × 10 ¹⁴ pieces / cm ² . This result almost coincides with the result of the STM image. This triangle includes three BNSH molecules arranged in a screw shape as shown in FIG. 13 which is an enlarged view of the triangle.

At the bottom of FIG. 12, only the arrangement of sulfur atoms is
If illustrated as being arranged in a 3-fold hollow site of gold, the line connecting the holes is approximately 10
(See the angle between the lines at the top of FIG. 12). And it turns out that S body and R body have a mirror image relationship. FIG. 14 shows a model of an adjacent part of the R-domain and the S-domain obtained by the racemic treatment. It can be seen that the straight line connecting the holes of each domain has an inclination of about 20 degrees as in the STM image.

Based on the above STM image and asymmetric in-surface sequence modeling, the present inventors have found that optically active binaphthothiol forms a regular two-dimensional structure on the gold (111) surface, and its R-form and S-form. Discovered that the structures made by each are mirror images, that is, an asymmetric surface is constructed,
This was confirmed for the first time. As far as the present inventors know,
There has been no report of immobilizing an asymmetric molecule on a surface by a covalent bond and directly observing the asymmetric two-dimensional structure created thereby. The asymmetric surface according to the invention of the present application is a novel structure obtained by the inventors of the present invention after intensive studies. The asymmetric surface according to the present invention can be provided as a new material in research on asymmetric electrode reaction systems and catalytic reaction systems, and has a very significant effect of contributing to the progress and development of such research. It is.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the difference between the prior art and the asymmetric surface according to the present invention.

FIG. 2 is a schematic diagram showing the principle of the self-organizing method.

FIG. 3 is a schematic diagram showing the structure of BNSH.

FIG. 4 is a graph showing CV of a modified electrode.

FIG. 5 is a graph showing CV of a modified electrode when KOH is added.

FIG. 6 is a photograph replacing a drawing showing an STM image of a gold (111) facet.

FIG. 7 is a photograph replacing a drawing showing an STM image of a BNSH-modified gold surface.

FIG. 8: STM explaining the structure of R- and S-domains
It is a photograph replacing a drawing representing an image.

FIG. 9 is a photograph replacing a drawing showing an STM image of racemic BNSH.

FIG. 10: STM showing adjacent portions of R- and S-domains
It is a photograph replacing a drawing representing an image.

FIG. 11 is a diagram showing a relationship between a rule array and a step line;
It is a photograph replacing a drawing showing a TM image.

FIG. 12 is a schematic diagram of a sequence model of R- and S-domains.

FIG. 13 is a schematic diagram of a sequence model representing three BNSH molecules in a triangle.

FIG. 14 is a schematic diagram of a racemic sequence model.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tetsuko Shintani 11-19-19 Kita 6-Jo Nishi, Chuo-ku, Sapporo-shi, Hokkaido Katrea Park eleven 407 F-term (reference) 4G069 AA02 AA03 AA08 AA09 AA11 BA21A BA21B BA21C BC33B BC33C BD08A BD08B BD08C DA05 EE01 FA01 FB14 FB16 FB17 FC02 4G077 AA03 AA07 AB02 AB04 BF00 CB01 CB08 CG05 CG06 ED05 ED06 GA03 GA05 GA06 HA05 HA20 QA11 QA77 4H006 AA02 AA03 AB40 AB81 AB91 AC90 BB14 BE10 TA04

Claims (11)

[Claims] 1. An asymmetric surface structure having a two-dimensional asymmetric structure formed by an arrangement of molecules on a solid surface, wherein the molecules are bonded to the solid in a monolayer by a chemical reaction. An asymmetric surface structure characterized by the following. 2. An asymmetric surface structure having a mirror image relationship with the asymmetric surface structure according to claim 1. 3. A surface structure comprising a domain having an asymmetric surface structure according to claim 1 and a domain having an asymmetric surface structure according to claim 2. 4. The asymmetric surface structure according to claim 1, wherein the solid surface is a metal surface. 5. The asymmetric surface structure according to claim 4, wherein the metal surface is a gold (111) surface. 6. The asymmetric surface structure according to claim 1, wherein the molecule is an asymmetric molecule or an optically active axis asymmetric compound. 7. The optically active asymmetric compound according to claim 1, wherein the compound is binaphthothiol (BNSH) (1,1′-Binaphthalene-2,2′-d).
7. The asymmetric surface structure according to claim 6, which is an ithiol). 8. The method for producing an asymmetric surface structure according to claim 1, wherein the sequence of the molecule is used to form the two-dimensional asymmetric structure. Providing the solid surface with an area sufficient for the method, and immobilizing the molecule to the solid surface by a chemical reaction. 9. The method according to claim 8, wherein the fixing is performed by a self-organizing method. 10. The method according to claim 9, wherein the immersion solution containing the molecule used in the self-assembly method is basic. 11. The method according to claim 10, wherein ethanol is used as a solvent for the immersion solution, and the immersion solution is made basic with potassium hydroxide.