JPS6213051B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a gas adsorbent, and particularly to a gas adsorbent containing a five-coordinated high spin type iron porphyrin complex as an active ingredient. Conventionally, formula (where each R ¹ is a hydrogen atom, vinyl group, or ethyl group)
It is known that in the Fe() state, it has the ability to adsorb oxygen molecules to the axial coordinate site in the presence of a suitable axial ligand (pyridine or imidazole). However, when pyridine or imidazole is added as an axial ligand, the axial ligand coordinates to two axial sites, e.g. (However, -- indicates the state of the porphyrin ring plane viewed from the side. The same applies hereinafter.) It is necessary to take a six-coordinated (low spin) structure such that oxygen displaces imidazole and coordinates. Since the spin must be recombined from low spin to high spin, oxygen complexes are difficult to form under conditions that are susceptible to oxidative degradation, such as in water. For this reason, CCKhang and TG
Trailer is a formula We synthesized the proximal base type iron porphyrin complex shown in (Proc. Nat. Acad. Sci. USA Vol. 70, p. 2674).
1973). This complex has the formula It is said that it is easy to form a stable five-coordinate (high spin) structure as shown in Figure 2, and that oxygen can be adsorbed efficiently at the vacant sixth position. However, it has been found that in this compound, the imidazole group is actually not sufficiently coordinated. In other words, as a result of too strong steric hindrance between the methyl substituent and the porphyrin ring,
This complex is difficult to form a 5-coordinate structure and becomes a mixture with a 4-coordinate structure in which the imidazole group is not coordinated. This four-coordination complex is oxidized very quickly by oxygen, resulting in extremely poor oxygen adsorption properties. The object of the present invention is to provide a gas adsorbent containing a proximal base type iron porphyrin complex having only a stable five-coordinate high spin type structure as an active ingredient. According to this invention, the general formula (Here, 〓 is the expression An iron porphyrin complex having _a porphyrin _ring shown in
There is provided a gas adsorbent comprising as an active ingredient a proximal base type iron porphyrin complex in which R is a methyl group or an ethyl group and n is 4, 5 or 6). In the proximal base type iron porphyrin complex represented by formula (A), the group connecting the amide bond and the imidazole group is different from the conventional ( _-CH2 ) _-3 , and is ( _-CH2 ) _{-4 to 6} .
As a result, surprisingly, the complex has only a stable five-coordinate high-spin structure and exhibits the excellent effect of reversibly adsorbing and desorbing oxygen even in water and at room temperature. This effect is particularly excellent when R is a methyl group and n is 5. Further, the solubility of the complex represented by formula (A) can be changed depending on the type of X. For example, when X is a hydrogen atom or an alkali metal such as sodium or potassium, it is water-soluble, and when X is a _C1 - _C20 alkyl group, it is oil-soluble. As an example of the method for producing the complex represented by formula (A), first, N-(ω-aminoalkyl)-2-methylimidazole is synthesized according to the following reaction formula. In the above reaction (), potassium phthalimide is suspended in about three times the molar amount of alkylene bromide, such as pentamethylene bromide, and the suspension is heated and stirred at 190 to 200°C. After the reaction is completed, the mixture is allowed to cool and unreacted pentamethylene bromide is removed by steam distillation.
Ether and water are added to the residue, and after shaking, the ether layer is separated. Extract the remaining aqueous layer with ether,
The ether extract is dried over Na ₂ SO ₄ and the ether is removed under reduced pressure. The obtained oil was dissolved in chloroform, and the filtered solution was concentrated under reduced pressure to obtain a solid residue. This is recrystallized from ethanol to obtain the desired N-(ω-bromoalkyl)phthalimide. In reaction (), oily sodium hydride is suspended in anhydrous toluene, 2-methylimidazole (2MeIm) is added, and the mixture is brought to boiling point reflux while passing in _N2 gas. A toluene solution of N-(ω-bromoalkyl)phthalimide obtained in reaction () is added to this and the mixture is refluxed at the boiling point. The reaction mixture is filtered, the residue is washed with toluene, and the liquid and washing liquid are combined and the solvent is distilled off under reduced pressure to obtain an oily residue. This was filtered through a silica gel column using chloroform/methanol (20/
1) and purified by thin layer chromatography.
Collect spillage. Distill the solvent under reduced pressure to obtain the desired N
-(ω-phthalimidoalkyl)-2-methylimidazole is obtained. In reaction (), the product obtained in reaction () is dissolved in methanol, 100% hydrazine hydrate is added, and the mixture is brought to boiling point reflux. After adding water to this, methanol is distilled off under reduced pressure, concentrated hydrochloric acid is added, and the mixture is brought to boiling point reflux.
The reaction mixture was cooled to 0°C, the resulting precipitate was removed, and the liquid was concentrated under reduced pressure to obtain a powdery residue. This was recrystallized from ethanol and the desired N-(ω-
Aminoalkyl)-2-methylimidazole (AAMI) is obtained. Now, using the AAMI thus obtained, a complex represented by formula (A) is obtained according to the following reaction formula. (In each of the above formulas, 〇 is porphyrin, 〓 is Fe
_{The above} reaction () can take two routes. In (A), dicarboxyporphyrin monoester and triethylamine (Et ₃ N) are combined in CH ₂ Cl ₂
Ethyl chloroformate (ECC) is added at -10°C, and after a certain period of time, AAMI is added and reacted. The reaction product is separated and purified using a silica gel column using chloroform/ethanol (15/1).
In (B), porphyrin monoester is dissolved in CH ₂ Cl ₂ , N,N'-dicyclohexylcarbodiimide (DCC) is added at 0°C, AAMI is added thereto, and the mixture is reacted overnight at room temperature. The obtained reaction product (A)
Refine in the same way as. In reaction (), the product obtained in reaction () is
Dissolve in DMF, add FeCl ₂ .nH ₂ O under N ₂ flow, and reflux. The product is purified with chloroform/ethanol (80/1) using a basic alumina column to obtain the desired product. Reaction () is carried out when X in formula (A) is a hydrogen atom, and potassium hydroxide is added to the product obtained in reaction () and the reaction is carried out at room temperature. Thereafter, it is neutralized with hydrochloric acid to precipitate the hydrolysis product.
When this reaction step () is adopted, it is convenient that X' is a lower alkyl group such as a methyl group or an ethyl group. The dicarboxyporphyrin used in the above reaction may be of any type as long as it has a porphyrin ring with two carboxyl groups, but typical ones with the formula (Here, each R ¹ is a hydrogen atom, a vinyl group, or an ethyl group). The complex represented by formula (A) thus obtained reversibly adsorbs and desorbs oxygen, CO and NO, either as a solid as it is or as a solution in an appropriate solvent. In particular, the gas adsorbent of the present invention has an excellent effect of reversibly adsorbing and desorbing oxygen even in water and at room temperature. The gas adsorbent of the present invention in the form of a solution preferably contains the complex represented by formula (A) at a concentration of 10 ^-6 mol/or more. When the complex represented by formula (A) exists at high concentration in a solution state, the following formula is obtained due to the collision of two molecules. (here,

[expression] and

[Formula] shows the state in which the proximal base B is coordinated with the central iron and the state in which it is dissociated, respectively), dimerization progresses and the gas adsorption/desorption ability may decrease over time. In the above case, if a mixed solution is added with a soluble polymer thickener in the solvent used, the above 2.
The quantification reaction is significantly reduced and the oxygen adsorption/desorption ability can be improved. Of course, the addition of a polymeric thickener improves the oxygen adsorption/desorption capacity even at low concentrations of the complex. The above polymer thickener has a number average molecular weight (n) of
Any nonionic polymer having a molecular weight of 5,000 or more may be used, such as polystyrene, polymethyl methacrylate, polyacrylamide, polyN-vinylpyrrolidone polyethylene oxide, polysaccharide (especially dextran), etc. What is necessary is to select one that is soluble in the solvent. It is desirable to add this polymeric thickener in an amount of 1 to 10%, preferably 2 to 5%. In particular, when the gas adsorbent of the present invention is used in the form of an aqueous solution, when dextran is used as the polymer thickener, the central iron of the complex represented by formula (A) is reduced by Fe() because it has a reducing ability. Since it slowly reduces the central iron to Fe(), there is no need to add a reducing agent such as Na ₂ S ₂ O ₄ (usually used in an amount approximately 5 times the molar amount of the complex) to reduce the central iron to Fe(). It's convenient. Note that when the gas adsorbent of the present invention is used in the form of an aqueous solution, the aqueous solution is prepared in an inert atmosphere such as N ₂ or argon. The gas adsorbent of this invention absorbs trace amounts from gas.
Useful for removing NO, CO or _O2 , co-catalyst for catalytic reactions, etc. The gas adsorbent of the present invention will be described below with reference to Examples, but prior to that, a synthesis example of the complex represented by formula (A) will be described. Synthesis Example 1 Synthesis of N-(5-aminopentyl)-2-methylimidazole (A) Potassium phthalimide 60.0g (0.324 mol)
was suspended in 250 g (1.0 mol) of pentamethylene bromide, and heated and stirred in an oil bath at 190 to 200°C for 12 hours. After the reaction was completed, the mixture was allowed to cool and unreacted pentamethylene bromide was removed by steam distillation. Ether and water were added to the residue, and after shaking, the ether layer was separated. The remaining aqueous layer was extracted twice with ether, the ether extract was dried over Na ₂ SO ₄ , and the ether was distilled off under reduced pressure to obtain a brown oily residue. The obtained oily residue was dissolved in chloroform, and the filtered solution was concentrated under reduced pressure to obtain a brown solid residue (63.8 g). This was recrystallized from ethanol to obtain the desired N-(5-bromopentyl)phthalimide. Yield 48.0g (yield
50.1%). (B) Suspend 1.17 g of 50% oily sodium hydride in 50 ml of anhydrous toluene and add 2-methylimidazole.
2.0 g (24.4 mmol) was added and the mixture was refluxed at boiling point for 5 hours while passing N ₂ gas through it. Add to this the N-(5-bromopentyl)phthalimide obtained in (A) above.
Add a toluene solution of 7.2 g) 24.4 mmol)
Boiling reflux was carried out for 15 hours. After cooling, the reaction mixture was filtered and the brown precipitate was washed with toluene.
The liquid and washing liquid were combined and the solvent was distilled off under reduced pressure to obtain a brown oily residue. This was applied to a silica gel column (φ3×
chloroform/methanol (20/
1) and purified by thin layer chromatography (R _f =
0.42, chloroform/methanol (10/1);
R _f =0.19 chloroform/methanol (20/
A fourth effluent was collected according to 1)). The solvent was distilled off under reduced pressure to obtain the target N-(5-phthalimidopentyl)-2-methylimidazole as a pale yellow powder. Yield 2.63g (yield 36.3%). (C) 17.7 g (59.5 mmol) of the product obtained in (B) above
was dissolved in 250 ml of methanol, 2.98 g (59.5 mmol) of 100% hydrazine hydrate was added, and the mixture was refluxed at boiling point for 1.5 hours. After adding 200 ml of water to this, methanol was distilled off under reduced pressure, 200 ml of concentrated hydrochloric acid was added, and the mixture was refluxed at the boiling point for 2 hours. The reaction mixture was cooled to 0°C, the resulting white precipitate was removed, and the liquid was concentrated under reduced pressure to obtain a pale yellow powdery residue. This was recrystallized from ethanol to obtain the desired N-(5-aminopentyl)-2-methylimidazole (APeMI).
was obtained as pale yellow crystals. Yield 12.1g (yield
84.7%). The structure of APeMI was confirmed by NMR, and the results shown in the table below were obtained.

【table】

[Table] Synthesis Example 2 Synthesis of proximal base-type iron porphyrin complex (A)-1 3.0 g of protoporphyrin monoethyl ester (PP・OEt) and 0.5 g of triethylamine were dissolved in 50 ml of CH ₂ Cl ₂ and heated at -10°C. Add 0.55g of ethyl chloroformate, and after 5 minutes
0.84 g of APeMI was added and reacted. The reaction product was separated and purified using a silica gel column (φ4×20 cm) using chloroform/ethanol (15/1). Yield 290mg. (A)-2 3.3 g of PP・OEt was dissolved in 80 ml of CH ₂ Cl ₂ , and 1.16 g of N,N'-dicyclohexylcarbodiimide was added at 0°C. After 30 minutes, the mixture was dissolved.
0.94 g of APeMI was added and reacted overnight at room temperature. The obtained reaction product was purified in the same manner as (A)-1. Yield 320mg. (B) 300 mg of the product obtained in (A)-2 above was dissolved in DMF, and 180 mg of FeCl ₂ .nH ₂ O was added under a N ₂ stream, and the mixture was refluxed for 1 hour. The product was purified twice with chloroform/ethanol (80/1) using a basic alumina column (φ3×15 cm) to obtain the desired product. Yield 172mg. The value of the visible absorption maximum (λmax) of this complex in chloroform at room temperature is
They were 387, 511, 540 and 640mm. (C) 250 ml of 1N aqueous potassium hydroxide solution was added to 100 mg of the product obtained in B above, and the mixture was reacted at room temperature. Thereafter, it was neutralized with 1N hydrochloric acid to adjust the pH to 5, and the hydrolysis product was precipitated. Collect this, wash it with water,
It was heated and dried. Yield 96.7mg. Synthesis Example 3 Synthesis of N-(4-aminobutyl)-2-methylimidazole (A) Potassium phthalimide 60.0g (0.324mol)
223g (1.03mol) of tetramethylene bromide
The mixture was suspended in water and heated and stirred in an oil bath at 190 to 200°C for 12 hours. After the reaction was completed, the mixture was allowed to cool and unreacted tetramethylene bromide was removed by steam distillation. Add ether and water to the residue and after shaking,
The ether layer was separated. The remaining aqueous layer was extracted twice with ether, the ether extract was dried over Na ₂ SO ₄ , and the ether was distilled off under reduced pressure to obtain a brown oily residue. The obtained oily residue was dissolved in chloroform, and the filtered solution was concentrated under reduced pressure to obtain a brown solid residue (64.1 g). This is recrystallized from ethanol to obtain the desired N-(4-bromobutyl).
Obtained phthalimide. Yield 48.1g (yield 52.6
%) (B) 5.85 g of 50% oily sodium hydride was suspended in 250 ml of anhydrous toluene, 10.0 g (0.122 mol) of 2-methylimidazole was added, and the mixture was refluxed at boiling point for 5 hours while passing N ₂ gas. Add to this the N-(4-bromobutyl)phthalimide obtained in (A) above.
Add 34.4g (0.122mol) of toluene solution and add 15
Boil at reflux for an hour. After cooling, the reaction mixture was filtered, the brown precipitate was washed with toluene, the liquid and the washing liquid were combined, and the solvent was distilled off under reduced pressure to obtain a brown oily residue. Add this to a silica gel column (φ3×45
chloroform/methanol (20/cm)
1) and purified by thin layer chromatography (R _f =
0.42, chloroform/methanol (10/1);
=0.19, chloroform/methanol (20/1)
A fourth effluent was collected. The solvent was distilled off under reduced pressure to obtain the desired N-(4-phthalimidobutyl)-2.
-Methylimidazole was obtained as a pale yellow powder. Yield: 19.4g (yield 56.2%). (C) 17.0 g (60.0 mmol) of the product obtained in (B) above
was dissolved in 250 ml of methanol, 3.01 g (60.0 mmol) of 100% hydrazine hydrate was added, and the mixture was refluxed at boiling point for 1.5 hours. After adding 200 ml of water to this, methanol was distilled off under reduced pressure, 200 ml of concentrated hydrochloric acid was added, and the mixture was refluxed at the boiling point for 2 hours. The reaction mixture was cooled to 0°C, the resulting white precipitate was removed, and the liquid was concentrated under reduced pressure to obtain a pale yellow powdery residue. This was recrystallized from ethanol to obtain the target N-(4-aminobutyl)-2-methylimidazole (ABuMI) as pale yellow crystals. Yield 12.0g (yield 88.4
%). The structure of ABuMI was confirmed by NMR, and the results shown in the table below were obtained.

[Table] Synthesis Example 4 Synthesis of proximal base type iron porphyrin complex (A) Protoporphyrin monoethyl ester 59
Dissolve 1 g of Et 3 N in 1 dichloromethane and 10.1 g of Et ₃ N.
After adding, the mixture was cooled to −10° C. or below, and 10.8 g of ethyl chloroformate was added. After 10 minutes, 15.3 g of ABuMI obtained in Synthesis Example 3 [ABuMI・2HCl
20.2 g of Et ₃ N was added to 22.6 g of dichloromethane suspension to remove hydrochloric acid] and the mixture was reacted at room temperature for 3 hours. The obtained reaction product was filtered with chloroform/silica gel column (φ6 x 20 cm).
It was separated and purified with ethanol (15/1). yield
23.2g (B) 20.0g of the product obtained in (A) above was dissolved in DMF, and 13.0g of FeCl ₂ .nH ₂ O was added under a N ₂ stream.
The mixture was heated and stirred at ℃ for 2 hours. The product was transferred to a basic alumina column (φ6×15
cm) using chloroform/ethanol (80/cm).
The desired purified product was obtained by purification twice in step 1). yield
12.4g. The visible absorption maximum (λmax) values of this complex were 387, 511, 541 and 640 nm in chloroform at room temperature. (C) Add 10g of the product obtained in (B) above to 100ml of methanol.
25 ml of a 2N aqueous potassium hydroxide solution was added to the mixture, and the mixture was reacted at room temperature. After that, it was neutralized with 2N hydrochloric acid, adjusted to pH5, and the hydrolysis product (ABuMI
−〓−COOH) was precipitated. This was washed with water and dried by heating. Yield 9.5g Synthesis Example 5 Synthesis of N-(6-aminohexyl)-2-methylimidazole (A) Potassium phthalimide 60.0g (0.324 mol)
268g (1.10mol) of hexamethylene bromide
The mixture was suspended in water and heated and stirred in an oil bath at 190 to 200°C for 12 hours. After the reaction was completed, the mixture was allowed to cool and unreacted hexamethylene bromide was removed by steam distillation. Add ether and water to the residue and after shaking,
The ether layer was separated. The remaining aqueous layer was extracted twice with ether, the ether extract was dried over Na ₂ SO ₄ , and the ether was distilled off under reduced pressure to obtain a brown oily residue. The obtained oily residue was dissolved in chloroform, and the filtered solution was concentrated under reduced pressure to obtain a brown solid residue (67.3 g). This was recrystallized from ethanol to obtain the desired N-(6-bromohexyl)phthalimide. Yield 51.2g (yield
50.9%). (B) 5.85 g of 50% oily sodium hydride was suspended in 250 ml of anhydrous toluene, 10.0 g (0.122 mol) of 2-methylimidazole was added, and the mixture was refluxed at boiling point for 5 hours while passing N ₂ gas. Add to this the N-(6-bromohexyl)phthalimide obtained in (A) above.
Add 37.8g (0.122mol) of toluene solution and add 15
Boil at reflux for an hour. After cooling, the reaction mixture was filtered, the brown precipitate was washed with toluene, the liquid and the washing liquid were combined, and the solvent was distilled off under reduced pressure to obtain a brown oily residue. Add this to a silica gel column (φ3×45
chloroform/methanol (20/cm)
1) and purified by thin layer chromatography (R _f =
0.42, chloroform/methanol (10/1);
R _f =0.19, chloroform/methanol (20/
A fourth effluent was collected according to 1). The solvent was distilled off under reduced pressure to obtain the target N-(6-phthalimidohexyl)-2-methylimidazole as a pale yellow powder. Yield: 20.8g (yield 54.8%). (C) 18.7 g (60.0 mmol) of the product obtained in (B) above
was dissolved in 250 ml of methanol, 3.01 g (60.0 mmol) of 100% hydrazine hydrate was added, and the mixture was refluxed at boiling point for 1.5 hours. After adding 200 ml of water to this, methanol was distilled off under reduced pressure, 200 ml of concentrated hydrochloric acid was added, and the mixture was refluxed at the boiling point for 2 hours. The reaction mixture was cooled to 0°C, the resulting white precipitate was removed, and the liquid was concentrated under reduced pressure to obtain a pale yellow powder residue. This was recrystallized from ethanol to obtain the target N-(6-aminohexyl)-2-methylimidazole (AHeMI) as pale yellow crystals. Yield 13.3g (yield 87.0
%). The structure of AHeMI was confirmed by NMR, and the results shown in the table below were obtained.

【table】

[Table] Synthesis Example 6 Synthesis of proximal base type iron porphyrin complex (A) Protoporphyrin monoethyl ester 59
Dissolve 1 g of Et 3 N in 1 dichloromethane and 10.1 g of Et ₃ N.
After adding, the mixture was cooled to −10° C. or below, and 10.8 g of ethyl chloroformate was added. After 10 minutes, 18.1 g of AHeMI obtained in Synthesis Example 5 [AHeMI・2HCl
20.2 g of Et ₃ N was added to 25.4 g of dichloromethane suspension to remove hydrochloric acid] and the mixture was reacted at room temperature for 3 hours. The obtained reaction product was separated and purified using a silica gel column (φ6×20 cm) using chloroform/ethanol (15/1). Yield 24.0
g. (B) Dissolve 20.0 g of the product obtained in (A) above in DMF, add 13.0 g of FeCl・nH ₂ O under a N ₂ stream, and
The mixture was heated and stirred at ℃ for 2 hours. The product was transferred to a basic alumina column (φ6×15
cm) using chloroform/ethanol (80/cm).
The desired purified product was obtained by purification twice in step 1). Yield: 11.7g. The visible absorption maximum (λ
max) value is 387 in chloroform at room temperature,
They were 511, 541 and 640nm. (C) Add 10.0 g of the product obtained in (B) above to 100 g of methanol.
ml, 25 ml of 2N aqueous potassium hydroxide solution was added, and the mixture was reacted at room temperature. Thereafter, the mixture was neutralized with 2N hydrochloric acid and the pH was adjusted to 5 to precipitate a hydrolysis product (AHeMI-1H-COOH). This was collected, washed with water, and dried by heating. Yield: 9.4g Example 1 The complex obtained in Synthesis Example 2 was dissolved in water at a concentration of 1 x 10 ^-4 mol/, and Na ₂ S ₂ O ₄ (reducing agent) was added at 5 x 10 ^-4 mol/. added at the rate of If you blow enough _N2 gas and leave it for 1 hour, the central iron will be
Fe() changed to Fe(), and the aqueous solution turned red accordingly. This was bubbled with O ₂ (oxygen) or CO at room temperature and the visible absorption spectra were recorded. We also recorded visible absorption spectra after vacuum degassing (or after blowing N ₂ or argon gas). The results are shown in Table A below in comparison with those for myoglobin.

[Table] As can be seen from the results, the gas adsorbent of the present invention behaves similarly to myoglobin with respect to adsorption and desorption of oxygen or carbon monoxide, indicating that an O ₂ complex or a CO complex is generated. Furthermore, similar results were obtained even after repeating the adsorption and desorption of these gases more than 10 times. The attached figure shows the visible absorption spectrum of the gas adsorbent of the present invention when adsorbing and desorbing oxygen in the above example. In the figure, curve a is after oxygen adsorption, and curve b is after oxygen degassing. Comparative Example An experiment similar to the above was conducted on a conventional compound represented by formula (). When a reducing agent is added and _N2 gas is blown in sufficiently and left, the central iron changes from Fe() to Fe(), but when the visible spectrum is measured, 432
Although it showed absorption at 557 nm, it was broad and was mixed with a four-coordinate structure in which the imidazole group was not sufficiently coordinated. When oxygen was blown into this at room temperature, it rapidly deteriorated due to oxidation. Example 2 The complex obtained in Synthesis Example 2 was dissolved in water at a concentration of 1 x 10 ^-4 mole, and dextran with a molecular weight of 6000 was added thereto at a ratio of 5% by weight/volume, and N ₂ gas was sufficiently supplied. After blowing into the solution, it was left at room temperature for one day. When oxygen was blown into this aqueous solution, the resulting oxygen complex remained stable for 2 to 3 days. Furthermore, more oxygen adsorption and desorption was achieved than in Example 1. Note that when agar was added in place of dextran at a ratio of 2% by weight/volume, the obtained oxygen complex remained stable for one week. Examples 3 and 4 The same operations as in Example 1 were carried out using the complexes obtained in Synthesis Examples 4 and 6 instead of the complex obtained in Synthesis Example 2. The results are shown in Table B.

[Table] In Examples 3 and 4, similar results were obtained even when the gas adsorption and desorption was repeated 10 times and 5 times, respectively. Example 5 The complex obtained in Synthesis Example 4 was dissolved in water at a concentration of 1 x 10 ^-4 mole, and dextran with a molecular weight of 6,000 was added thereto at a ratio of 5% by weight/volume, and N ₂ gas was sufficiently supplied. After blowing into the solution, it was left at room temperature for one day. When oxygen was blown into this aqueous solution, the resulting oxygen complex remained stable for two days. Furthermore, more oxygen adsorption and desorption was achieved than in Example 3. Example 6 The complex obtained in Synthesis Example 6 was dissolved in water at a concentration of 1×10 ^-4 mol/polyethylene glycol with a molecular weight of 40,000 was added thereto at a ratio of 5% by weight/volume, and N ₂ gas was added. After sufficiently blowing, the mixture was left at room temperature for one day. When oxygen was blown into this aqueous solution, the resulting oxygen complex remained stable for two days. Furthermore, more oxygen adsorption and desorption was achieved than in Example 4.

[Brief explanation of the drawing]

The attached figure is a visible absorption spectrum diagram when the gas adsorbent of the present invention adsorbs and desorbs oxygen.

Claims (1)

[Claims] 1. General formula (Here, 〓 is the expression An iron porphyrin complex having _a porphyrin _ring shown in
A gas adsorbent comprising, as an active ingredient, a proximal base type iron porphyrin complex, in which R is a methyl group or an ethyl group and n is 4, 5 or 6). 2. The gas adsorbent according to claim 1, wherein R is a methyl group and n is 5. (1) General formula (Here, 〓 is the expression _An iron porphyrin complex having _a porphyrin ring shown in A gas adsorbent comprising a proximal base type iron porphyrin complex represented by 5 or 6) and a nonionic polymer. 4. The gas adsorbent according to claim 1, wherein the nonionic polymer is a polysaccharide. 5. The gas adsorbent according to claim 3 or 4, wherein R is a methyl group and n is 5.