JP2015003875A - Phosphorus compound and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel phosphorus compound improved in solvent solubility and a method for producing the same.SOLUTION: The phosphorus compound is represented by general formula (I) (where Y, Y, Y, and Yeach independently represent an aralkyl group or a hydrogen atom; at least one of Yto Yis an aralkyl group; A and Z are each independently an ethylene group or an isopropylene group; n and m are each independently 0, 1, or 2; and two A's or Z's may be the same or different when n or m is 2).

Description

  The present invention relates to a novel phosphorus compound having improved solvent solubility and a method for producing the same. More specifically, for example, it is useful as a stabilizer and flame retardant for epoxy resins, polyester resins, polyurethane resins, polybutyral resins, SBR, NBR, AS resins, ABS resins, etc. As an intermediate, for example, an epoxy resin, a polyester resin, a polyether resin, a polycarbonate resin, a polyurethane resin, a compound having a dihydro-oxa-phospho-phenanthrene skeleton useful as a resin material having a high refractive index, and a novel phosphorus having improved solvent solubility. The present invention relates to a compound and a method for producing the same.

  A compound represented by the following formula (c) having a dihydro-oxa-phospho-phenanthrene skeleton (hereinafter may be abbreviated as “compound (c)” or trade name “HCA-NQ”, Sanko Co., Ltd.) Is a cyclic organophosphorus compound useful as a polymer material or a flame retardant (Patent Document 1). For example, it has been reported that high flame retardancy is exhibited by addition to an epoxy resin (Patent Document 2).

  On the other hand, an acrylate having a benzene ring introduced is known as a (meth) acrylate having a high refractive index (Patent Document 3). Its refractive index is about 1.58. A compound having a dihydro-oxa-phospho-phenanthrene skeleton also has a high refractive index because it has a high density of benzene rings and a phosphorus atom with a high polarizability. Therefore, the compound (c) has a high refractive index of 1.68 and is suitable as a raw material for a high refractive index resin material.

JP-A-61-2236787 JP 2008-208315 A Japanese Patent Laid-Open No. 05-58950

  However, when the compound (c) is used as a resin material for flame retardant applications, high refractive index applications, or other applications, the compound (c) has a low solubility in a solvent, and therefore the handleability to a resin material is poor. There is a problem.

  Therefore, a compound having a dihydro-oxa-phospho-phenanthrene skeleton such as compound (c) and having good solvent solubility is desired.

  As a result of intensive studies to solve the above problems, the present inventors have improved the solubility in a solvent by introducing an aralkyl group into a compound having a dihydro-oxa-phospho-phenanthrene skeleton. The title and the present invention have been completed. That is, this invention makes it a subject to provide the novel phosphorus compound which improved the solvent solubility, and its manufacturing method.

To solve the above problem,
The present invention provides a phosphorus compound represented by the following formula (I).

(In the formula, Y ₁ , Y ₂ , Y ₃ , and Y ₄ each independently represent an aralkyl group or a hydrogen atom. At least one of Y _{1 to} Y ₄ is an aralkyl group. Z is independently an ethylene group or an isopropylene group, and n and m are each independently 0, 1 or 2, and when n or m is 2, two A or Z may be the same as each other May be different.)

  The phosphorus compound of the present invention is preferably represented by the following formula (a).

    The phosphorus compound of the present invention is preferably represented by the following formula (b).

  In addition, the present invention includes a step of obtaining a compound represented by the following general formula (I) -1 by reacting a compound represented by the following general formula (II) with 1,4-naphthoquinone. A method for producing a phosphorus compound represented by the formula (I) -1 is provided.

(In the formula, Y ₁ , Y ₂ , Y ₃ , and Y ₄ each independently represent an aralkyl group or a hydrogen atom. At least one of Y _{1 to} Y ₄ is an aralkyl group.)

  In addition, the present invention reacts a compound represented by the following general formula (I) -1 with at least one selected from the group consisting of ethylene oxide, ethylene carbonate, propylene oxide, and propylene carbonate, to give the following general formula: Provided is a method for producing a phosphorus compound represented by the following general formula (I) -2, which comprises a step of obtaining a phosphorus compound represented by the formula (I) -2.

(In the formula, Y ₁ , Y ₂ , Y ₃ , and Y ₄ each independently represent an aralkyl group or a hydrogen atom. At least one of Y _{1 to} Y ₄ is an aralkyl group. A and Z are Each independently represents an ethylene group or an isopropylene group; n ¹ and m ¹ are each independently 0, 1 or 2, provided that n ¹ and m ¹ are not both 0, and n ¹ or m ^{When 1} is 2, two A or Z may be the same or different from each other.)

  According to the present invention, a phosphorus compound having improved solvent solubility and a method for producing the same are provided.

It is the data of the infrared absorption spectrum of the compound (a) obtained in Example 1. It is the data of the infrared absorption spectrum of the compound (b) obtained in Example 2.

[Phosphorus compounds]
The phosphorus compound according to the present invention is a dihydro-oxa-phospho-phenanthrene derivative represented by the following general formula (I) (hereinafter sometimes abbreviated as “compound (I)”).
Compound (I) has a dihydro-oxa-phospho-phenanthrene skeleton useful as an intermediate for stabilizers, flame retardants and polymer compounds, or intermediates for optical resin materials that require a high refractive index. It is a novel compound with improved solubility.

(In the formula, Y ₁ , Y ₂ , Y ₃ , and Y ₄ each independently represent an aralkyl group or a hydrogen atom. At least one of Y _{1 to} Y ₄ is an aralkyl group. Z is independently an ethylene group or an isopropylene group, and n and m are each independently 0, 1 or 2, and when n or m is 2, two A or Z may be the same as each other May be different.)

Y < ₁ >, Y < ₂ >, Y < ₃ >, Y < ₄ > in a formula represents an aralkyl group or a hydrogen atom. At least one of Y _{1 to} Y ₄ is an aralkyl group.
The position of the aralkyl group in the formula is not particularly limited as long as it is any of Y _{1 to} Y ₄ .

Examples of the aralkyl group in Y _{1 to} Y ₄ in the formula include a benzyl group (phenylmethyl group), 1-methylbenzyl group, phenethyl group (phenylethyl group) and the like.

A and Z in the formula are each independently an ethylene group (—CH ₂ CH ₂ —) or an isopropylene group (—CH (CH ₃ ) CH ₂ —).

In the formula, n and m are each independently 0, 1 or 2.
When n is 2, two A's may be the same or different from each other, and when m is 2, two Z's may be the same or different from each other.

  Preferred examples of compound (I) include those represented by the following formulas (a) and (b).

Compound (I) has a dihydro-oxa-phospho-phenanthrene skeleton in its structure. Since this skeleton has a phosphorus atom, the compound (I) is useful as a flame retardant. In addition, phosphorus atoms have a high refractive index because they have a high polarizability and, in addition, a high benzene ring density. And since it has two hydroxyl groups in the structure, it is suitable as a flame retardant or as an intermediate for various resin materials such as optical resin materials that require a high refractive index.
Then, by introducing an aralkyl group into the dihydro-oxa-phospho-phenanthrene skeleton, solvent solubility is improved and handling properties are improved. Further, since the compound (I) has a phosphorus atom in its structure, a resin that requires high adhesion to a base material unique to such a compound (see “Tokuyo 2007-231107”). It is also suitable as a material.

In the present invention, the reason for improving the solvent solubility by introducing an aralkyl group into a compound having a dihydro-oxa-phospho-phenanthrene skeleton is as follows. Since the aralkyl group has a benzene ring, the lipophilicity is improved. Moreover, since it has a fatty chain, the melting point tends to decrease, and the solvent solubility is improved. Furthermore, since the density of the benzene ring hardly decreases, the refractive index hardly changes even when a compound having no aralkyl group introduced is compared with a compound having an aralkyl group introduced. Therefore, it is possible to improve solvent solubility while maintaining appropriateness as an intermediate of a flame retardant or a polymer compound, or an optical resin material for which a high refractive index is desired.
On the other hand, when a chain alkyl group is introduced into the dihydro-oxa-phospho-phenanthrene skeleton, the density of the benzene ring is lowered and the refractive index is lowered, so that it is not suitable as an intermediate for an optical resin material for which a high refractive index is desired.
Further, when a phenyl group is introduced into the dihydro-oxa-phospho-phenanthrene skeleton, the density of the benzene ring is improved, but the melting point tends to increase, so that the handling property is deteriorated.

[Method for producing phosphorus compound]
Compound (I) can be produced, for example, by the method shown below depending on whether n and m are each 0 or not.
Among compounds (I), a compound represented by the following general formula (I) -1 corresponding to n = m = 0 (hereinafter sometimes abbreviated as “compound (I) -1”) A compound represented by the following general formula (II) (hereinafter sometimes abbreviated as “compound (II)”) and 1,4-naphthoquinone are reacted to give the following general formula (I) -1. It can manufacture by the method which has the process of obtaining the phosphorus compound represented by these.

(In the formula, Y ₁ , Y ₂ , Y ₃ , and Y ₄ each independently represent an aralkyl group or a hydrogen atom. At least one of Y _{1 to} Y ₄ is an aralkyl group.)

In formula (II) and _{(I) -1, Y 1,} Y 2, Y 3, Y 4 are the same as _{Y 1, Y 2, Y 3} , Y 4 in the general formula (I).

The organic solvent in the step of obtaining compound (I) -1 is preferably an inert solvent. Examples of the inert solvent include ethylene glycol lower alkyl ether, propylene glycol lower alkyl ether, benzene, and toluene.
The said organic solvent may be used individually by 1 type, and may use 2 or more types together.

  In the reaction of compound (II) with 1,4-naphthoquinone, the above-mentioned inert solvent solution of compound (II) is prepared and adjusted so that compound (II) is in excess with respect to 1,4-naphthoquinone. Then, 1,4-naphthoquinone is preferably added in the form of fine powder or an inert solvent solution similar to the above.

  In the reaction in the step of obtaining compound (I) -1, the reaction temperature at the time of adding 1,4-naphthoquinone is preferably 60 to 150 ° C., and it is highly possible that other than the target product is produced by reacting at a high temperature. Therefore, 70-120 degreeC is more preferable. Moreover, although it is preferable to prepare reaction time according to reaction temperature, it is 0.5 to 5 hours, More preferably, it is 1.5 to 3 hours.

  In the step of obtaining compound (I) -1, after the completion of the reaction, the physical properties of compound (I) -1 and the types and amounts of the used raw materials and organic solvents are taken into consideration, if necessary, by a known method. Post-treatment may be performed to extract compound (I) -1. That is, as necessary, post-treatment operations such as filtration, washing, extraction, pH adjustment, dehydration, concentration, etc. are performed alone or in combination of two or more, and concentration, crystallization, reprecipitation, column chromatography are performed. The compound (I) -1 may be taken out by, for example. In addition, the extracted compound (I) -1 may be used alone or in combination of two or more of operations such as crystallization, reprecipitation, column chromatography, extraction, and stirring and washing of the crystals with a solvent, if necessary. May be purified once or more.

In addition, as compound (II), for example, in compound (II), Y ₁ is a benzyl group and Y ₂ , Y ₃ and Y ₄ are hydrogen atoms (8-benzyl-9,10-dihydro- 9-oxa-10-phosphophenanthrene-10-oxide, “Bz-HCA” manufactured by Sanko Co., Ltd.).

  A compound represented by the following general formula (I) -2 corresponding to the compound (I) excluding the case where n and m are both 0 (hereinafter abbreviated as “compound (I) -2”). May be obtained by reacting compound (I) -1 with one or more selected from the group consisting of ethylene oxide, ethylene carbonate, propylene oxide, and propylene carbonate, and the following general formula (I) -2: And a step of obtaining a novel phosphorus compound (compound (I) -2) represented.

(In the formula, Y ₁ , Y ₂ , Y ₃ , and Y ₄ each independently represent an aralkyl group or a hydrogen atom. At least one of Y _{1 to} Y ₄ is an aralkyl group. A and Z are Each independently represents an ethylene group or an isopropylene group; n ¹ and m ¹ are each independently 0, 1 or 2, provided that n ¹ and m ¹ are not both 0, and n ¹ or m ^{When 1} is 2, two A or Z may be the same or different from each other.)

In the general formula (I) -1 and _{(I) -2, Y 1,} Y 2, Y 3, Y 4, Y 1 A and Z in the general formula _{(I), Y 2, Y} 3, Y 4, A And Z are the same.
In general formula (I) -2, n ¹ and m ¹ are each independently 0, 1 or 2, provided that n ¹ and m ¹ are not (simultaneously) 0 and n ¹ Is 2, the two A's may be the same or different, and when m ¹ is 2, the two Z's may be the same or different.

Hereinafter, first, a case where both n ¹ and m ¹ are not 0 will be described.
In this case, in the step of obtaining compound (I) -2, the reaction between compound (I) -1 and one or more selected from the group consisting of ethylene oxide, ethylene carbonate, propylene oxide and propylene carbonate is preferably performed. At least one of these is dissolved in an organic solvent. In addition, such a reaction may be performed with or without a catalyst.
Ethylene oxide, ethylene carbonate, propylene oxide and propylene carbonate give A and Z in compound (I) -2.

  The total amount of one or more selected from the group consisting of ethylene oxide, ethylene carbonate, propylene oxide and propylene carbonate is preferably 2 to 6 times the molar amount relative to compound (I) -1, It is more preferable that the amount is a double molar amount.

The organic solvent in the step of obtaining compound (I) -1 is not particularly limited, but preferred examples include esters such as methyl acetate, ethyl acetate, phenyl acetate and benzyl acetate; halogenated hydrocarbons such as dichloromethane and trichloromethane; Ketones such as methyl isobutyl ketone; ethers such as tetrahydrofuran; aromatic hydrocarbons such as benzene, toluene and xylene; aromatic alcohols such as phenol; N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc) And amides such as
The said organic solvent may be used individually by 1 type, and may use 2 or more types together.

  The catalyst in the step of obtaining compound (I) -2 is not particularly limited as long as it does not interfere with the target reaction by reacting with other raw materials to be used. Moreover, the said catalyst may be used individually by 1 type, and may use 2 or more types together.

Preferred examples of the catalyst include an acid catalyst and a base catalyst.
The acid catalyst is not particularly limited, and preferred examples include inorganic acids such as hydrochloric acid and sulfuric acid; organic acids such as acetic acid, paratoluenesulfonic acid and methanesulfonic acid.
Although the base catalyst is not particularly limited, preferred examples thereof include carbonates or bicarbonates such as sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate as long as they are inorganic bases.

  In the reaction in the step of obtaining compound (I) -2, the reaction temperature is preferably 100 to 180 ° C, and more preferably 140 to 160 ° C. Moreover, although it is preferable to adjust reaction time according to reaction temperature, it is 1 to 15 hours, More preferably, it is 3 to 10 hours.

  In the step of obtaining compound (I) -2, after the completion of the reaction, as in the step of obtaining compound (I) -1, post-treatment is performed as necessary by a known method to obtain compound (I)- 2 can be taken out.

Hereinafter, a case where only ^one of n ¹ and m ¹ is 0 will be described.
In this case, the reaction in the step of obtaining compound (I) -2 may be abbreviated as one or more selected from the group consisting of ethylene oxide, ethylene carbonate, propylene oxide and propylene carbonate (hereinafter referred to as “ethylene oxide etc.”). ) Is preferably less than 2-fold molar amount, more preferably 0.8-1.8-fold molar amount, and even more preferably 1-1.5-fold amount relative to Compound (I) -1. For example, the amount of the target compound (I) -2 produced can be improved by reducing the total amount of ethylene oxide and the like as compared with the case where n ¹ and m ¹ are not 0. As a method of improving the production amount of compound (I) -2, for example, in addition to the method of reducing the total use amount of ethylene oxide and the like, for example, than the case where both n ¹ and m ¹ are not 0 And a method for reducing the reaction temperature (for example, the reaction temperature is preferably 80 ° C. or more and less than 100 ° C.), a method for shortening the reaction time (for example, the reaction time is preferably 30 minutes or more and less than 1 hour), etc. it can. Two or more of these methods may be used in combination. The step of obtaining compound (I) -2 when these methods are applied is carried out in the same manner as in the case where n ¹ and m ¹ are not 0 except that the conditions are changed as described above. Good. When a by-product is generated, the target compound (I) -2 can be easily obtained by applying one suitable as the above-described extraction method or generation method.

  Any of the production methods of the above-mentioned compound (I) is an excellent method in that the target products (compounds (I) -1 and (I) -2) can be efficiently produced.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the following examples.

<Production of Compound (I)>
Example 1
Production of Bz-HCA-NQ (Production of Compound (a))

  Compound (II) -1 (Bz-HCA) (193.0 g, 0.63 mol) and toluene (193.0 g, 2.10 mol) are added to a 1000 mL 4-neck flask, heated and dissolved, and stirred at 100 ° C. Hold while doing. Thereto, 99.7 g (0.63 mol) of 1,4-naphthoquinone and 299.1 g (3.25 mol) of toluene were added and dissolved dropwise over 2 hours. After completion of dropping, the mixture was kept at 100 ° C. for 2 hours, then cooled to 20 ° C., and the precipitate was filtered. The filtered crystals and benzyl acetate (481.0 g, 3.2 mol) were added, heated and dissolved, and heated to 150 ° C. After heating, it was filtered hot, crystallized by adding a seed crystal while cooling, filtered and separated to obtain a slightly red crystal (260.4 g, yield 89.0%). Here, the yield is a value based on Compound (II) -1 (Bz-HCA).

The melting point of the obtained slightly red crystals was 208 ° C.
In addition, the slightly red crystals were dissolved in a solvent, and the refractive index (x) at 25 ° C. was calculated according to the following formula (1).

(Wherein x is the refractive index of the crystal; y is the refractive index of the solvent; z is the refractive index of the solution in which the crystal is dissolved in the solvent; w ₁ is the mass of the dissolved crystal; w ₂ is the mass of solvent required to dissolve the crystals.)

  The elemental analysis values of the obtained slightly red crystals are shown in Table 1 together with the theoretical values. The theoretical value is calculated as “C29H21O4P1”.

  FIG. 1 shows infrared absorption spectrum data (IR data) of the obtained slightly red crystals by the KBr tablet method.

As is clear from FIG. 1, the faint red crystal has a peak indicating that a phosphoroso double bond “—P═O” exists at a wavelength of 1200 cm ⁻¹ , and a hydroxyl group “at wavelengths of 3188 cm ⁻¹ and 3240 cm ^−1. Absorption peak indicating —OH ”, and absorption peaks indicating naphthalene rings at wavelengths of 1464 cm ⁻¹ and 1601 cm ⁻¹ .
The elemental analysis values (actual measurement values) were in good agreement with the theoretical values.
From the above, it was confirmed that the obtained slightly red crystals were the compound (a).

<< Example 2 >>
Production of Bz-HCA-NQ-EO (Production of Compound (b))

  In a 1000 mL 4-neck flask, compound (a) (Bz-HCA-NQ) (418.1 g, 0.90 mol), DMAc (418.1 g, 4.80 mol), ethylene carbonate (174.4 g, 1.98 mol) Then, sodium carbonate (2.1 g, 0.020 mol) was added and heated and dissolved, and the reaction was carried out for 6 hours while stirring at 160 ° C. After completion of the reaction, the pressure was reduced to 0.49 kPa to remove DMAc (367.1 g, 4.21 mol), benzyl acetate (627.2 g, 4.18 mol) was added, hot filtration was performed, and the seeds were cooled. Crystals were added for crystallization, followed by filtration and separation to obtain white crystals (453.6 g, yield 91.2%). Here, the yield is a value based on the compound (I) -1.

The melting point of the obtained white crystals was 166 ° C.
The refractive index (x) of the white crystal at 25 ° C. calculated by the same method as in Example 1 was 1.657.

  The elemental analysis values of the obtained white crystals are shown in Table 2 together with theoretical values. The theoretical value is calculated as “C29H21O4P1”.

  FIG. 2 shows infrared absorption spectrum data (IR data) of the obtained white crystals by the KBr tablet method.

The Figure 2, the product by IR analysis, Hosuhoroso double bond at a wavelength of 1196cm ^-1 "-P = O" peaks indicative of the presence of, a wavelength 3026cm ^-1 and 3061cm ^-1 "= C-H" absorption peak showing a wavelength ^2864Cm -1, the 2938Cm ^-1 "-CH ₂ -" There are absorption peaks indicating an absorption peak showing a hydroxyl group "-OH" on the wavelength 3404cm ^-1 and a wavelength 3445Cm ^-1, further wavelength having an absorption peak showing a naphthalene ring 1450 cm ^-1 and 1585 cm ^-1.
The elemental analysis values (actual measurement values) were in good agreement with the theoretical values.
From the above, it was confirmed that the obtained white crystals were the compound (b).

  In order to compare how the solvent solubility changes by introducing an aralkyl group, compounds (c) and (d) in which a benzyl group corresponding to the compounds prepared in Example 1 and Example 2 is not introduced Was synthesized.

≪Comparative example 1≫
Production of HCA-NQ (Production of Compound (c))

  Instead of compound (II) -1 (Bz-HCA), compound (II) -2 (9,10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide, Sanko Co., Ltd., "HCA") was used. The reaction was performed in the same manner as in Example 1 except that.

The melting point of the obtained slightly red crystals was 296 ° C.
Further, the refractive index (x) of the white crystal at 25 ° C. calculated by the same method as in Example 1 was 1.682.
The resulting pale red crystals were compound (c) (HCA-NQ).

≪Comparative example 2≫
Synthesis of HCA-NQ-EO (compound (d))

  The reaction was performed in the same manner as in Example 2 except that the compound (c) (HCA-NQ) was used instead of the compound (a) (Bz-HCA-NQ).

The melting point of the obtained white crystals was 205 ° C.
The refractive index (x) of the white crystal at 25 ° C. calculated by the same method as in Example 1 was 1.661.
The obtained white crystals were compound (d) (HCA-NQ-EO).

[solubility]
Compound (a) (Bz-HCA-NQ) and Compound (c) (HCA-NQ) and Compound (b) (Bz-HCA-NQ) and Compound (d) (HCA-NQ-EO) at 20 ° C. The solubility (g / 100 g) in each solvent was measured, and the solubility in each solvent depending on whether or not an aralkyl group was introduced into the dihydro-oxa-phospho-phenanthrene skeleton was compared.

Comparing the solubility of the compound (a) and the compound (c), and the compound (b) and the compound (d) in each solvent, the compounds in which the aralkyl group is introduced into the dihydro-oxa-phospho-phenanthrene skeleton are all used. The solvent solubility was improved by introducing an aralkyl group.
Further, when the refractive indexes of the compound (a) and the compound (c) and the compound (b) and the compound (d) are almost the same, the aralkyl group is introduced into the dihydro-oxa-phospho-phenanthrene skeleton. It was possible to improve solvent solubility without lowering the refractive index.

  The present invention can be used as a resin material for flame retardant applications, high refractive index applications, or other applications.

Claims (5)

The phosphorus compound represented by the following general formula (I).

(In the formula, Y ₁ , Y ₂ , Y ₃ , and Y ₄ each independently represent an aralkyl group or a hydrogen atom. At least one of Y _{1 to} Y ₄ is an aralkyl group. Z is independently an ethylene group or an isopropylene group, and n and m are each independently 0, 1 or 2, and when n or m is 2, two A or Z may be the same as each other May be different.) The phosphorus compound of Claim 1 represented by following formula (a).

The phosphorus compound of Claim 1 represented by following formula (b).

The following general formula (I) -1 having a step of obtaining a compound represented by the following general formula (I) -1 by reacting a compound represented by the following general formula (II) with 1,4-naphthoquinone The manufacturing method of the phosphorus compound represented by these.

(In the formula, Y ₁ , Y ₂ , Y ₃ , and Y ₄ each independently represent an aralkyl group or a hydrogen atom. At least one of Y _{1 to} Y ₄ is an aralkyl group.) A compound represented by the following general formula (I) -1 is reacted with one or more selected from the group consisting of ethylene oxide, ethylene carbonate, propylene oxide and propylene carbonate, and the following general formula (I) -2 The manufacturing method of the phosphorus compound represented by the following general formula (I) -2 which has the process of obtaining the phosphorus compound represented.

(In the formula, Y ₁ , Y ₂ , Y ₃ , and Y ₄ each independently represent an aralkyl group or a hydrogen atom. At least one of Y _{1 to} Y ₄ is an aralkyl group. A and Z are Each independently represents an ethylene group or an isopropylene group; n ¹ and m ¹ are each independently 0, 1 or 2, provided that n ¹ and m ¹ are not both 0 and n ¹ or When m ¹ is 2, two A or Z may be the same or different from each other.)

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