JP3374170B2 - Light control metal ion scavenger and metal ion recovery method using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel photocontrollable metal ion scavenger which traps, holds and releases metal ions by changing the photochromic state, and recovers metal ions in a solution using the same. It is about how to do it.

[0002]

2. Description of the Related Art Conventionally, an attempt to capture a substance (that is, inclusion) by using a cyclic compound such as crown ether has been studied as a part of the chemistry of host guests [Iwao Tabushi et al. Chemistry "(1979), published by Kyoritsu Shuppan]. Among them, the one that selectively forms a complex with an ion to perform extraction / transport is called an ionophore, which has been particularly noted in recent years. In such an ionophore,
If a photosensitive substituent that interacts with an ion is introduced into the ionophore in advance, a change in absorption spectrum of the photosensitive substituent or [[Journal of Chemical Society. Chemical communication ”, page 730 (1992)], and changes in emission spectrum [“ Nature ”, volume 364, page 42 (1993)] may occur, and various ions may be detected by detecting these changes. The optical analysis of is devised.

By the way, it is known that some photosensitive groups exhibit photochromism, that is, a phenomenon in which two kinds of states having different colors are reversibly exchanged by irradiation of light. This compound chemically moves back and forth between two isomers having different molecular structures, and a molecule exhibiting this property is called a photochromic molecule. Photochromic molecules having such properties have attracted attention because they can be expected to be used in the fields of light control, decoration, printing, recording, calculation, display, etc., and researches for their practical use have been actively conducted.

Particularly, in the information field which has been widely spread in recent years, it is said that the photon mode recording method is indispensable for high-speed and high-density recording required in the future. In the latest photon mode recording, the photoreaction in nanometer-sized pits is controlled by near-field light, etc., but a photochromic molecule capable of expressing bistability from a single molecule is used for this purpose. It is possible [eg, "Applied Physics", Vol. 66, p. 228 (1997)].

As described above, when a photochromic molecule is exposed to light, its molecular shape and chemical properties are remarkably changed, so that it is possible to control the characteristics of a substance or material containing the photochromic molecule by using light as a trigger. Supervised by Kunihiro Ichimura, "Chromic Materials and Applications", published by CMC (1989)]. Moreover, it is speculated that it is possible to control the ion trapping phenomenon with light by combining a photochromic molecule and an ionophore. As an example, it is possible to combine spirobenzopyran with azacrown ether to select ions for trapping. It has been reported that photo-isomerization of spirobenzopyran molecules can change the sex [Journal of Chemical Society Chemical Communication, p. 147 (1991)]. Similar to ion trapping, it can be inferred that a series of light control such as ion trapping, transporting, and releasing can be performed if it is possible to cause changes in the retention and release of ions by photostimulation. The fact is that no material has been found so far.

On the other hand, calixarenes are cyclic oligomers obtained by condensation of phenols and formaldehydes or derivatives thereof, and have a goblet-like molecular structure, and other atoms or molecules are present at this goblet site. It is known that it is possible to form an adduct that encloses

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a novel metal ion scavenger that traps, holds and releases metal ions by changing the photochromic state, and recovers metal ions in a solution using the same. The purpose is to provide a method.

[0008]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have focused on the inclusion ability of calixarenes, and have at least two photochromic pyropyrans in the calixarene. In the state where the spiropyran residue is ring-closed, various metal ions of groups 1, 2 and 3 of the Periodic Table (long period type) are included in the calixarene skeleton to form an adduct when the residue of the compound is bonded. Forming, (2) the adduct of the spiropyran residue with a metal ion formed in a ring-closed state does not easily release the ion, and (3) the spiropyran residue is a ring-opened product thereof upon irradiation with light. It was found that metal ions are released to the outside of the calixarene skeleton when the merocyanine body is used, and the present invention has been completed based on this finding.

That is, the present invention provides a photocontrollable metal ion scavenger consisting of a calixarene in which at least two residues of a photochromic spiropyran compound are bound, and a photocontrollable metal ion-containing solution in a metal ion-containing solution in a light-shielded state. Provided is a method for recovering a metal ion, which comprises adding an ion-trapping agent to form the metal ion adduct, separating the metal ion adduct, and then irradiating the metal ion to release the metal ion and recovering the metal ion. It is a thing.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The photocontrollable metal ion scavenger of the present invention comprises a calixarene in which two or more residues of a photochromic spiropyran compound are bonded in the molecule. For example, the general formula

[Chemical 1] (In the formula, R ¹ is a residue of a photochromix pyropyran compound or an alkyl group having 1 to 5 carbon atoms, R ² is a residue of a photochromix pyropyran compound, a hydroxyl group or an alkoxyl group having 1 to 5 carbon atoms, and R ³ is a lower alkylene. At least one of R ¹ and R ² is a residue of a photochromic spiropyran compound, and n is an integer of 4 to 8).

In the above general formula (I), the residue of the photochromic spiropyran compound of R ¹ and R ² is, for example,

[Chemical 2] (Z in the formula is a divalent organic group capable of directly or indirectly binding to calixarene).

The residue of the photochromic spiropyran compound is preferably one having a nitro group introduced into the benzopyran ring in order to improve the photochromic property. Further, although it binds to calixarene via Z, its position is not particularly limited as long as it is in the vicinity of the calixarene.

In the general formula (I), examples of the alkyl group having 1 to 5 carbon atoms in R ¹ include a methyl group, an ethyl group, a tert-butyl group, and the like.
Examples of the alkoxyl group having 1 to 5 carbon atoms in ² include a methoxy group, an ethoxy group, and a tert-butoxy group. As the lower alkylene group represented by R ³ , a methylene group is particularly preferable.

The calixarene to which the residue of the photochromic spiropyran compound represented by the general formula (I) is bonded is not particularly limited in its production method.
It can be manufactured by a conventionally known method.

The photocontrollable metal ion scavenger of the present invention having such a structure changes the isomerization state of the residue of the photochromic spiropyran compound by irradiating light, thereby trapping, retaining and releasing ions. Can be controlled.

For example, when the photocontrollable metal ion scavenger of the present invention comprises a calixarene having a residue of the photochromic spiropyran compound represented by the general formula (I) bound thereto, the spiropyran compound residue is ring-closed. In this state, an adduct in which various metal ions are included in the calixarene skeleton can be easily formed. The metal ions effective for forming this adduct include:
Examples thereof include metals such as lithium, sodium, potassium, and cesium belonging to Group 1 of the periodic table (long period type), metals such as magnesium and calcium belonging to Group 2, metal ions such as lanthanum belonging to Group 3, and the like. These adducts can be prepared in a suitable solvent such as acetonitrile,
The solution of calixarene having a residue of the photochromic spiropyran compound is subjected to heat treatment or light irradiation to bring the spiropyran compound residue into a ring-closed state, and then a salt containing a desired metal ion is appropriately added to the solution. It can be formed by adding.

The calixarene having a residue of the photochromic pyropyran compound is a polar solvent such as water, alcohol, dimethylformamide, dimethylsulfoxide or acetonitrile, acetone, tetrahydrofuran, dioxane, chloroform, methylene chloride, ethyl acetate or diethyl ether. It is soluble in solvents with moderate polarity, and adduct formation by salt addition in these solvents is easy.

Further, in the photocontrollable metal ion scavenger of the present invention, the photochromic reaction associated with light irradiation in the above-mentioned soluble solvent, polymer film, gel, resin, etc. and metal ions in the metal ion scavenger The movement can be shown, for example, in the schematic diagram of FIG. As shown in FIG. 1, when the absorption band of the ring-closed compound (Ia) is photoexcited, a heterolytic C—O cleavage reaction occurs at the spiro carbon position, resulting in a merocyanine-type ring-opened compound (I) having strong absorption in the visible region. -B) is generated. This ring-opened body has an ionic structure, and in particular, its phenolate anion strongly interacts with the metal ion included in the calixarene skeleton immediately below, so that the metal ion leaves the inclusion field and a new ion is generated. The bond forms with the phenolate anion. At this time, since the metal ions are exposed to the outside, the metal ions can be released and used.

As described above, the photo-controllable metal ion scavenger of the present invention is capable of photo-controlling the trapping, retention, transport and release of ions. FIG. 2 is a schematic diagram showing an example of a state in which light trapping, ion transport (holding), and ion release are controlled by light in the light control metal ion trapping agent of the present invention.

In order to recover metal ions using this photocontrollable metal ion scavenger, metals such as lithium, sodium, potassium and cesium belonging to Group 1 of the periodic table (long period type) and magnesium belonging to Group 2 are included. , A metal such as calcium, and a solution containing the ions of a metal such as lanthanum belonging to Group 3 in a light-blocking state, the light control metal ion scavenger is added to form the metal ion adduct, and the metal is then adducted. After separating the ion adduct by taking an appropriate means, the metal ion can be recovered by irradiating it with light to release the metal ion.

[0021]

The photo-controlled metal ion scavenger of the present invention comprises a calixarene in which two or more photochromic spiropyran compound residues are bound in the molecule, and the photochromic state is changed by the control of light. By doing so, the metal ions can be captured, retained and released, and the metal ions in the solution can be easily recovered.

[0022]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Structural formula

[Chemical 3] Lithium nitrate, sodium nitrate, potassium nitrate and cesium nitrate were added to an acetonitrile solution containing the calixarene represented by the formula (1) at a concentration of 0.1 mmol / liter, and the concentration was adjusted to 1 mmol / liter. A clathrate was formed by standing for a time. This was subjected to electrospray ionization mass spectrometry. The spectrum is shown in FIG. By this operation, it was confirmed that approximately 85% or more of calixarene formed an inclusion body. Mass peaks and relative intensities measured by mass spectrometry are as follows. Mass peak and relative intensity: 1461.3510, 0.2
9 (M ・ H +); 1467.3555, 1.00 (M ・
Li +); 1483.3308, 0.49 (M · Na
+); 1499.3223, 0.32 (M · K +); 1
593.3075, 0.21 (M · Cs +).

Example 2 An acetonitrile solution containing 0.1 mmol / liter of calixarene and 0.4 mmol / liter of lithium nitrate having the same structure as that used in Example 1 was prepared.
Electrospray ionization mass spectrometry of this solution was measured before irradiation with ultraviolet light, immediately after irradiation with ultraviolet light, and after about 10 minutes in the dark after irradiation with ultraviolet light. The spectra are shown in FIGS. 4 (a), (b) and (c), respectively. In the initial state (before UV light irradiation), the lithium ion clathrate (mass peak 1466.3721) is present at a high concentration (a), but with the formation of the ring-opened body by UV light irradiation, the lithium ion clathrate is included. The body's concentration decreased and lithium ion-free calixarene (mass peak 146
An increase in concentration of 0.3696) was seen (b). By the subsequent blocking of light irradiation, a thermal ring closure reaction proceeded, ion uptake was performed again, and after about 10 minutes, the concentration of the lithium ion inclusion complex was recovered (c).

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of the movement of metal ions in the photo-controlled metal ion scavenger of the present invention.

FIG. 2 shows a photo-controlled metal ion scavenger of the present invention
The schematic diagram which shows an example of the state where ion capture, ion transport (holding), and ion emission are controlled by light.

FIG. 3 shows that in Example 1, calixarene in which a residue of a photochromic spiropyran compound is bound,
FIG. 3 is a spectrum diagram of electrospray ionization mass spectrometry when various metal ions are included.

FIG. 4 is a spectrum diagram of electrospray ionization mass spectrometry in Example 2 in each state of a solution containing a calixarene having a residue of a photochromic spiropyran compound bound thereto and a metal ion.

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Claims (2)

(57) [Claims] 1. A photocontrollable metal ion scavenger comprising a calixarene having at least two residues of a photochromic spiropyran compound bonded thereto. 2. In the light-shielded state, the light control metal ion scavenger according to claim 1 is added to a solution containing metal ions to form the metal ion adduct, and then the metal ion adduct is separated, A method for recovering metal ions, which comprises irradiating light to release the metal ions and recovering them.