JP6799339B2 - Synthesis of metal salt compound aggregate of phenylazomethine type dendrimer and production method of sub-nanoparticles - Google Patents

Description

The present invention relates to a method for synthesizing a novel phenylazomethine-type dendrimer aggregate accumulating a metal salt compound and a method for producing sub-nanoparticles.

Oxidation reaction is known to be a basic and basic reaction operation in various chemical fields such as resource chemistry, fuel chemistry, synthetic organic chemistry, and environmental chemistry. For this oxidation reaction, various catalysts have been tried to be used in both gas phase reaction and liquid phase reaction, and various metal catalysts have been put into practical use. However, in the conventional catalytic oxidation reaction, when air or oxygen is used as an oxidant, it is necessary to set a high temperature condition and to use an organic solvent having a large environmental load in the liquid phase reaction. There is a problem that the catalytic reaction efficiency is not always good.

Against this background, attention has been paid to the catalyst composition of atomized heterogeneous systems such as microparticles and nanoparticles as catalysts with excellent reaction activity, and studies from various viewpoints and approaches are underway. For fine particles of 10 nm or less, the bandgap becomes large and discrete based on the quantum effect, the active surface area increases due to fine particle formation, and the number of atoms that take a surface state different from the bulk increases, so that the fine particles are larger than the bulk. It can be expected to be highly active.

As a method for producing nanoscale fine particles that can also be used as such a catalyst, a method using a phenylazomethine dendrimer as a template, which is a unique method by the present inventors, has been energetically searched for and developed (Patent Documents). 1). The phenylazomethine dendrimer, which was developed by the present inventors and is being studied, has a large number of imine sites showing high coordination in the skeleton, and thus can be complexed with Lewis acid. The phenylazomethine dendrimer has an electron density gradient in which the electron density of imine increases from the terminal imine toward the center by continuously adding electrons from the imine from the terminal to the center. .. Due to this electron density gradient, when a metal salt is complexed with the phenylazomethine dendrimer, a stepwise complex formation occurs in which the innermost imine is preferentially complexed with the metal salt. By utilizing the stepwise complex formation ability of the phenylazomethine dendrimer, a binary system using two metal salts that accumulates different metal species in each layer, including a single one system such as platinum salt, etc. Furthermore, it is possible to accumulate precision heterometals of multiple types such as 3 types, 4 types, and 5 types, and it is possible to prepare a dendrimer complex in which the number and composition of metal salts are specified. By reducing the dendrimer complex coordinated with this metal salt, it is possible to form precisely controlled metal sub-nanoclusters having an extremely small particle size distribution (Patent Documents 2 to 5).

According to the research conducted by the present inventors, it has been clarified that the physical properties and chemical properties of the metal sub-nanocluster having about a dozen metal atoms largely depend on the number of constituent atoms and the type. (Non-Patent Documents 1 and 2). From this point of view, a synthetic method that defines the number of constituent atoms and their types is desired. However, the conventional phenylazomethine dendrimer complex has the following problems in order to obtain a stable complex in which the number is precisely defined, such as the stability of the bond of a metal atom to the dendrimer and the suppression of decomposition during complex synthesis. is there. For example, the stability of the bond is not always sufficient, and the conventional phenylazomethine dendrimer complex is decomposed under the influence of moisture when exposed to the atmosphere, so that it is not appropriate to handle it in the air. In the aqueous solution, the metal salt forming the complex is separated again due to the dissociation of the bond. To aim for "ultra-precision" synthesis of metal clusters with high atomic number accuracy, and to aim for "ultra-precision" synthesis of alloy clusters with single-atom accuracy by simultaneously accumulating different metal atoms in one dendrimer. It is essential to use a dendrimer with tightly bonded metal atoms.

Japanese Patent No. 4511125 Japanese Unexamined Patent Publication No. 2010-18610 Japanese Unexamined Patent Publication No. 2013-159588 Japanese Unexamined Patent Publication No. 2007-23166 JP-A-2018-145172

K. Yamamoto et al. Angew. Chem. Int. Ed. 2015, 54, 9810-9815. K. Yamamoto et al. Sci. Adv. 2017, 3, e1700101.

In the present disclosure, a novel method for producing a metal salt compound aggregate of a phenylazomethine type dendrimer and sub-nanoparticles is provided. In this aggregate, metal atoms form strong bonds to the dendrimer. Decomposition, dissociation, etc. of this aggregate are suppressed even in the air or aqueous solution, and the stability of the bond of metal atoms to the dendrimer is excellent. Therefore, 1: 1 complex formation reaction by imine and application to a wide range of metals In cluster synthesis using a phenylazomethine-type dendrimer, which is characterized by multi-metal accumulation due to sex and basic gradient, and clustering of accumulated metals, it enables "ultra-precision" synthesis of metal clusters with high atomic number accuracy. By simultaneously accumulating different metal atoms in one dendrimer, we provide a technique that enables "ultra-precision" synthesis of alloy clusters with single-atom accuracy.

In particular, "ultra-precision" synthesis can be achieved by combining with the synthetic concept of a novel phenylazomethine-type dendrimer. This synthetic concept is characterized by the formation of clusters according to the "shape" of the dendrimer, and the number of imine nitrogens in the dendrimer to react with the organic molecule that is the core of the dendrimer can be selected, so that the metal salt compound in the dendrimer coordinates. The number of imine nitrogen can be precisely controlled in individual steps. Therefore, it is possible to synthesize a number-controlled dendrimer in which the number of metal coordinations is controlled. That is, it is possible to create a metal cluster in which the number of atoms and composition are controlled.

In the aggregate of the present invention, a metal salt compound is accumulated in a phenylazomethine type dendrimer in a cyclic structure represented by the following formula (I):

(In the formula, MR indicates the metal salt compound, M indicates a metal atom, R indicates the chemical structure of the residue thereof. In the imine nitrogen atom and carbon atom forming an azomethin bond in the phenylazomethine structure, and the carbon atom. The cyclic structure is formed between the phenyl ring to be bonded and the metal atom M of the metal salt compound).

In a preferred embodiment of the aggregate of the present invention, the metal salt compound is integrated in a phenylazomethine type dendrimer represented by the following formula (II):

(In the equation, A represents an n-valent organic group that is the core of the dendrimer, n represents an integer of 1 or more. When n is 2 or more, each of the n dendron units is independent. X is the following. Indicates X ¹ or X ² represented by the formula.

(In the formula, Ph ^a represents ^a divalent phenyl residue that may have ^a substituent.)

(In the formula, Ph ^b indicates a monovalent phenyl residue which may have a substituent.)
In the repeating unit rep, when X is X ¹ , the repeating unit rep is repeated, the end of the repeating unit rep is X ² , and all Xs in the repeating unit rep are independent. All Ph ^a and Ph ^b substituents are independent. ).

Further, the method for producing sub-nanometal particles of the present invention is characterized in that the aggregate is reduced.

Further, according to the present invention, it is a method of controlling the number of metal atoms accumulated in a phenylazomethine type dendrimer using an aggregate in which a metal salt compound is accumulated in a cyclic structure represented by the above formula (I). By selecting the valence n of the organic group A and the repeating unit rep in the phenylazomethine type dendrimer represented by the formula (II), the number of metal atoms to be accumulated corresponds to the target number. Provided is a method including a step of synthesizing the phenylazomethine-type dendrimer having a site forming the cyclic structure and a step of accumulating the target number of the dissimilar metal salt compounds in the site forming the cyclic structure. Will be done.
Further, according to the present invention, the following aggregates in which dissimilar metal salt compounds are accumulated and the following methods that enable the production of alloy particles are provided.

The aggregate of the present invention is an accumulation of dissimilar metal salt compounds. In a preferred example, n in the phenylazomethine type dendrimer represented by the above formula (II) is an integer of 2 or more, and at least one of each of the n dendron units has a metal species different from that of the other dendron units. Different dissimilar metal salt compounds are accumulated.

The method for producing an aggregate of the present invention is a method for producing an aggregate in which a plurality of types of metal salt compounds having different metal types are integrated by controlling the number, and is any of the following [1] and [2]. Including the process.
[1] For a phenylazomethine type dendrimer, the following formula (I):

(In the formula, MR indicates the metal salt compound, M indicates a metal atom, R indicates the chemical structure of the residue thereof. In the imine nitrogen atom and carbon atom forming an azomethin bond in the phenylazomethine structure, and the carbon atom. The cyclic structure is formed between the phenyl ring to be bonded and the metal atom M of the metal salt compound.) The number of metal salt compounds having different metal species from each other is controlled. A step of binding the two types of aggregate fragments (A1) and (A2) that have been accumulated together at the cores of the respective phenylazomethine-type dendrimers to form an integrated aggregate.

[2] An aggregate fragment (A1') in which the number of metal salt compounds is controlled and accumulated in a cyclic structure represented by the formula (I), and a phenylazomethine-type dendrimer fragment (D1) in which no metal salt compound is accumulated. ) Is bonded to each other in each core, and the imine site derived from the phenylazomethine-type dendrimer fragment (D1) in which the metal salt compound is not accumulated is located at the imine site derived from the aggregate fragment (A1'). A step of controlling the number of dissimilar metal salt compounds having a different metal species from the metal salt compounds accumulated at the site by a cyclic structure represented by the formula (I) and accumulating them.

In a preferred example, the method for producing the aggregate further comprises any of the following steps [3] to [5].
[3] In the phenylazomethine type dendrimer, the number of metal salt compounds having a cyclic structure represented by the above formula (I) and having different metal types from the aggregates obtained in the above [1] or [2] is controlled. The aggregate fragment (A4) accumulated in the above and the aggregate fragment obtained in the above [1] or [2] are bound to each other in the cores of the respective phenylazomethine type dendrimers and integrated. Step of forming a body [4] An aggregate fragment which is an aggregate obtained in the above [1] or [2] and a phenylazomethine-type dendrimer fragment (D2) in which a metal salt compound is not accumulated are formed between cores. To the imine site derived from the phenylazomethine-type dendrimer fragment (D2) in which the metal salt compound is not accumulated, to the imine site derived from the aggregate obtained in the above [1] or [2]. Step of accumulating dissimilar metal salt compounds having different metal species from the accumulated metal salt compound by controlling the number in a cyclic structure represented by the formula (I) [5] Step of the above-mentioned [3] or [4]. After that, a step of optionally repeating the same operation as in [3] or [4] above.

In a preferred example, the method for producing the aggregate is to connect the cores in each of the three or more fragments in series in the steps [3] to [5].

The method for producing alloy particles of the present invention is characterized in that after an aggregate is obtained by the method for producing an aggregate, the aggregate is reduced to obtain an alloy particle having a controlled number.

(A) is a mass spectrum of the product synthesized in Example 1 measured by MALDI-TOF-MS, and (b) is a ¹ H-NMR spectrum of compound G0 which is a partial structure of the product and the dendrimer. is there. ^{1 1} H-NMR spectrum of a product synthesized in the presence of sodium acetate in Example 1 and a product synthesized without the addition of sodium acetate. It is an X-ray photoelectron spectroscopic spectrum before and after the reduction of the iridium complex synthesized in Example 1. The crystal structure of the iridium dinuclear complex synthesized in Example 3 by X-ray crystal structure analysis is shown. (A) is a mass spectrum of the iridium 12-nuclear complex synthesized in Example 4 measured by MALDI-TOF-MS, and (b) is a transmission electron microscope image. 5 is a mass spectrum of a rhodium 12 nuclear complex measured by MALDI-TOF-MS in Example 5. (A) is the mass spectrum of the platinum 12-nuclear complex measured by MALDI-TOF-MS in Example 6, and (b) is the HAADF-STEM image of the surface carrying the platinum 12-nuclear complex. 9 is an X-ray photoelectron spectroscopic spectrum after hydrogen reduction of the iridium 12-nuclear complex coated and immobilized on a Si wafer in Example 7. It is an X-ray photoelectron spectroscopic spectrum before reduction, after vacuum treatment, and after hydrogen reduction of the iridium 12-nuclear complex synthesized in Example 4. It is a HAADF-STEM image of the surface carrying the iridium 12-nuclear complex (left) and the surface after reduction (right). 9 is a mass spectrum of the iridium 10-17 nuclear complex measured by MALDI-TOF-MS in Example 9. FIG. 10 is a mass spectrum of a complex obtained by simultaneously complexing iridium and rhodium measured by MALDI-TOF-MS in Example 10. 11 is a mass spectrum of a complex in which iridium and rhodium are sequentially complexed as measured by MALDI-TOF-MS in Example 11. 12 is a photomicrograph of crystals of an iridium complex obtained from a water-methanol solution in Example 12. 13 is a mass spectrum of an iridium 7-nuclear rhodium 7-nuclear complex measured by MALDI-TOF-MS in Example 13. (A) and (b) are electron microscope observation images (HAADF-STEM) of the iridium 7-nuclear rhodium 7-nuclear complex of Example 13. It is an electron microscope observation image (HAADF-STEM) of the iridium 7 nucleus rhodium 7 nucleus complex of Example 13 which further expanded and showed the number of atoms. (A) and (b) are electron microscope observation images (HAADF-STEM) of the Ir ₇ Rh ₇ alloy cluster obtained in Example 14. (A) to (d) are images showing the results of STEM-EDX mapping of the Ir ₇ Rh ₇ alloy cluster obtained in Example 14. It is a graph which shows the STEM-EDX spectrum result of the Ir ₇ Rh ₇ alloy cluster obtained in Example 14. It is a graph which shows the measurement result of the hydrogen generation reaction (HER) activity of the Ir cluster in Example 15 (before annealing (raw)). It is a graph which shows the measurement result of the HER activity of the Ir cluster in Example 15 (after annealing (annealed)). It is a graph which shows the measurement result of the HER activity of Ir ₇ Rh ₇ and Ir ₁₄ in Example 16 (before and after annealing).

The present invention will be described in detail below.

In the aggregate of the present invention, a metal salt compound is accumulated in a phenylazomethine type dendrimer in a cyclic structure represented by the above formula (I).

In formula (I), a cyclic structure is formed between an imine nitrogen atom forming an azomethine bond in the phenylazomethine structure, a carbon atom, a phenyl ring bonded to the carbon atom, and a metal atom M of a metal salt compound. ing. In this cyclic structure, metal atoms form strong bonds to the dendrimer, and the aggregate of the present invention suppresses decomposition, dissociation, etc. even in the air or an aqueous solution, and is excellent in bond stability of metal atoms to the dendrimer. ..

Phenylazomethine-type dendrimers, which have phenylazomethine as a constituent unit of a dendritic branched structure, are characterized by being rigid because they have a rigid structure based on a π-conjugated system, and a sufficient space is secured inside the molecule to ensure a metal. Since it has a large number of coordination sites that form a complex with a salt, it is suitable for precisely accumulating a large number of metal salt compounds from the inner layer to the outer layer at each stage of complex formation site.

Phenylazomethine-type dendrimers have different environmental sites that interact with metal salt compounds. Here, the "site having a different environment" is a site in the dendrimer where the metal salt compound can be accumulated, that is, a site forming the cyclic structure of the above formula (I), and the interaction with the metal salt compound is different from each other. Means. The site includes a complex formation site with a metal salt compound, an ionic bond site, and a covalent bond site. The “complex forming site” means a site forming a complex with a metal salt compound in a dendrimer, and is a site serving as a Schiff base. In the unidirectional electron density gradient type dendrimer, the strength of interaction such as complex formation strength gradually changes from the inner layer to the outer layer so as to gradually weaken, forming parts having different environments.

In the unidirectional electron density gradient type dendrimer, since the basic gradient is generated from the core to the end, the complex formation constant of the core and the first generation complex formation site closest to the core is the highest, and the complex formation constant is stepwise toward the outside. The complex formation constant decreases. The difference in the complex formation constant serves as a driving force, and the metal salt compounds are gradually accumulated from the first generation to the second generation and the third generation near the center. In the conventional 4th generation phenylazomethine dendrimer, the number of fillings up to each layer is 4, 12, 28, 60 when the number of branches of the core is 4. On the other hand, in the phenylazomethine type dendrimer of the present invention, the number of metal salt compounds accumulated can be controlled one by one by applying the synthetic concept represented by the above formula (II).

In formula (I), M-R represents a metal salt compound, M represents a metal atom, and R represents the remaining chemical structure.

In the present invention, the "metal salt compound" is a broad definition including a salt of a metal and an anion, a complex of a ligand, and the like. In addition to the metal salt compound (a) that reacts with the phenylazomethine type dendrimer, as a result of the reaction, a complex or the like was formed and a part of the anion, the ligand, etc. was desorbed from R of the metal salt compound (a). The metal salt compound (b) in an accumulated state is also collectively referred to as a "metal salt compound".

The metal element in the metal salt compound to be accumulated in the dendrimer is not particularly limited, and for example, titanium, vanadium, iron, cobalt, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, etc. Examples thereof include indium, tin, antimony, hafnium, tantalum, tungsten, ruthenium, osmium, iridium, platinum, gold, mercury, bismuth and the like.

The counter anion or ligand in the metal salt compound is not particularly limited, but is, for example, halogen ions such as chloride ion, bromide ion, and iodide ion, trifluoromethanesulfonic acid, acetic acid, acetylacetone, salen, and cyclopentadi. Examples include enyl.

R in the metal salt compound M-R indicates the chemical structure of the residue of the metal atom M. Examples of R include the above-mentioned counter anion or ligand, and may have a singular or a plurality of bond forms depending on the valence of M. The mass of the entire R is not particularly limited, but may be, for example, 400 or less, 300 or less, or 200 or less in terms of atomic weight.

Specific examples of the metal salt compound are as follows.

When producing an aggregate in which a metal salt compound is accumulated in a dendrimer, a solution containing the dendrimer is prepared as a first step. The solvent for dissolving the dendrimer and its metal salt compound aggregate is not particularly limited as long as it can dissolve them. For example, chlorine-containing organic solvents such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1-dichloroethane and carbon tetrachloride, aromatic organic solvents such as benzene, toluene, xylene, chlorobenzene, anisole and acetophenone, cyclohexanone, Examples thereof include organic solvents such as tetrahydrofuran, limonene, propylene glycol monoethyl ether acetate and acetonitrile. These may be used in combination of 2 or more types.

In the next step, the metal salt compound is mixed with the solution to obtain a metal salt compound aggregate of the dendrimer in which the metal salt compound is accumulated. The method of mixing the metal salt compound with the dendrimer solution is not particularly limited, and examples thereof include dropping the metal salt compound solution into the dendrimer solution.

At this time, when an acetate salt such as sodium acetate is added, the formation of a cyclized complex is promoted, and the formation of benzophenone, which is a by-product, is suppressed.

It is also possible to accumulate dissimilar metal salt compounds by simultaneously or sequentially mixing the dissimilar metal salt compounds with the dendrimer solution. The coordination force of the metal salt can also be adjusted by changing the electronic effect of the counter anion, the steric effect of the ligand on the organic ligand, and other oxidation numbers of the metal salt. By these means, it is possible to increase the variation of the coordination force in the metal accumulation even if it is the same element, and it is also possible to change the accumulation order of the two kinds of metals. In the present invention, it is possible to obtain a dendrimer dissimilar metal salt accumulation in which two or more dissimilar metal salt compounds having different metal species are accumulated at different sites in the dendrimer environment. The number of metal species and metal salt compounds accumulated here is not particularly limited, but for example, an example in which up to eight different metal salt compounds are accumulated is known (Patent Document 5). When the dissimilar metal salt compound is accumulated in the dendrimer, the complex formation with the dendrimer site is reversible with respect to the order in which the metal salt compound solution is dropped and the mixing of the metal solution, and the arrangement changes to the most energetically stable arrangement. This is considered because it is considered that a metal having a strong complex bond strength spontaneously binds to a complex formation site having a high coordination force, and a metal having a weak complex bond strength binds to a complex formation site having a weak coordination force. It may be arbitrary from the viewpoint. It has been reported that when a metal having a weak complex formation strength is actually accumulated in an inner layer having a strong coordination force and then a metal having a strong complex formation strength is added, the binding sites are replaced. (Bull. Chem. Soc. Jpn. 2007, 80, 1563-1572.)

The aggregate of the present invention stably holds a metal atom to the dendrimer by forming a strong bond to the dendrimer by the cyclic structure represented by the formula (I), and synthesizes the phenylazomethine type dendrimer represented by the formula (II). This makes it possible to synthesize a number-controlled dendrimer in which the number of metal coordinations is controlled. That is, it is possible to create a metal cluster in which the number of atoms and composition are controlled.

In formula (II), A represents an n-valent organic group that is the core of the dendrimer. The organic group is not particularly limited, and an organic group used in a conventional phenylazomethine type dendrimer and an organic group having a related structure derived from common technical knowledge are referred to. Specific examples thereof include a monocyclic or polycyclic aromatic group, a heteroaromatic group, a porphyrin group, a phthalocyanine group, a cyclolam group and the like, and these may have a substituent. The number of carbon atoms of the organic group is not particularly limited, but may be, for example, 50 or less and 40 or less.

In formula (II), n represents an integer of 1 or more, preferably 2 or more. The upper limit of n is not particularly limited, but is preferably 6 or less, and more preferably 4 or less. When n is 2 or more, each of the n dendron units is independent.

In formula (II), X represents X ¹ or X ² .

At X ¹ , Ph ^a represents ^a divalent phenyl residue that may have ^a substituent. Preferably, it is a divalent phenyl residue in which the 1st and 4th positions in the para position are binding sites.

The substituent that Ph ^a may have is not particularly limited, but for example, a halogen atom such as a chlorine atom, a bromine atom or a fluorine atom, or an alkyl group such as a methyl group or an ethyl group (for example, 1 to 6 carbon atoms). , Heteroelement-containing groups (hydroxy group, amino group, nitro group, thiol group, etc.) whose bond site is heteroelement and does not contain carbon, halogen atom, oxygen-containing group (hydroxy group, oxo group, ether group, carboxyl group, etc.) Hetero-element-containing groups such as aldehyde groups), nitrogen-containing groups (cyano groups, primary to tertiary amino groups, nitro groups, etc.), sulfur-containing groups, phosphorus-containing groups, etc., are substituted with carbon atoms or have base ends or CC. Examples thereof include an alkyl group in which the bond is interrupted (for example, 1 to 6 carbon atoms). These substituents may have one or more. Among them, the number of substituents of Ph ^a is preferably 1 or less, and more preferably no substituents.

At X ² , Ph ^b represents a monovalent phenyl residue that may have a substituent. The Ph ^b substituent which may be a, is not particularly limited, for example, in the above, such as those exemplified as the substituent which may be possessed by Ph ^a like. These substituents may have one or more. Among them, the number of substituents of Ph ^b is preferably 1 or less, and more preferably no substituents.

In the repeating unit rep, all Ph ^a and Ph ^b substituents are independent.

In the repeating unit rep, when X is X ¹ , the repeating unit rep is repeated, the end of the repeating unit rep is X ² , and all Xs in the repeating unit rep are independent. Among them, in the repetition of the repeating unit rep, it is preferable that the branch having the largest number of generations in the dendritic structure is up to the fourth generation. The number of sites forming the cyclic structure represented by the formula (I) is not particularly limited, but may be 60 or less, 30 or less, and 5 or more, 7 or more.

In general, a dendrimer is a dendritic polymer having a structure that is regularly branched from the center, and is composed of a central molecule as a core and a dendron as a side chain portion. The number of branches of the dendron part is also called a generation. The portion branched from the central molecule of the dendrimer in one step is called the first generation, and the portion branched in two steps is called the second generation. In general, dendrimers are polymers that are regularly and completely dendritically branched from the core, have a spherical structure with sparse center and dense surface, and the number of generations increases with each branch from the center. .. Hyperbranched polymers, on the other hand, are polymers with incomplete dendritic branches, unlike dendrimers, which have a perfect dendritic structure. The phenylazomethine-type dendrimer of the present invention may be a hyperbranched polymer having such a partially defective branching unit.

The aggregate of the present invention is characterized in that the dendrimer has a stable bond with a metal atom due to the cyclic structure represented by the formula (I), and further, the imine nitrogen of the dendron that reacts with the organic molecule that is the core of the dendrimer. Since the number can be selected, the number of imine nitrogens coordinated by the metal salt in the dendrimer can be precisely controlled for each one. Therefore, it is possible to synthesize a number-controlled dendrimer in which the number of metal coordinations is controlled. Hereinafter, a point that enables the synthesis of a number-controlled dendrimer with a controlled metal coordination number will be described with specific examples. In this example, a method for controlling the number of metal atoms accumulated in a phenylazomethine-type dendrimer using an aggregate in which metal salt compounds are accumulated in a cyclic structure represented by the formula (I) is used. In the phenylazomethine type dendrimer represented by II), a site that forms a cyclic structure in a number corresponding to the desired number of metal atoms to be accumulated by selecting the valence n of the organic group A and the repeating unit rep. The present invention includes a step of synthesizing a phenylazomethine-type dendrimer having a phenylazomethine type, and a step of accumulating the target number of the dissimilar metal salt compounds at a site forming the cyclic structure.

In the example below, a second-generation dendrimer with four cores and 12 imines and a third-generation dendrimer with three cores and 13 imines are used from a 12-nuclear complex. A 12-atom cluster is synthesized from a 12-atom cluster and a 12-nuclear complex.

In the example below, two types of metal salts A and B are further accumulated in the dendrimer, and the composition of the alloy cluster is adjusted at the atomic number level (6 + 6) by selecting the compounding ratio of the accumulated metal salts A and B. Pieces) Controlled.

In the example below, a 3rd generation dendrimer with 1 core and 6 imines, a 3rd generation dendrimer with 1 core and 7 imines is used, and the former is an imine. Six metal salts A are complexed at six positions, and seven metal salts B are complexed at seven imines in the latter, and then the amino group in the former core and the ester group COOR in the latter core are peptide-bonded to form a dendrimer. A complex is formed in which two kinds of metal salts A and B are accumulated by controlling the number of them. This dendrimer complex is used to synthesize 6 + 7 atomic clusters. According to this method, the composition of the alloy cluster can be controlled at the atomic number level (6 + 7). In this method, two dendrimers may be complexed with a metal and then the dendrimers may be peptide bonded to each other, or one dendrimer may be complexed with a metal and then two dendrimers may be peptide bonded, followed by two dissimilar metals. It may be complexed with the dendrimer of the eye.

Next, a case where 10N-dendrimers to 17N-dendrimers, that is, the following dendrimers containing 10 to 17 sites forming the cyclic structure containing imine nitrogen are used for controlling the number of accumulated metals will be described.

The dendrimer used for number control can realize various dendrimers with an imine number A by combining a core and a dendron. In the case of the following structural formula, a combination represented by A = 1 × a + 3 × b + 7 × c + 15 × d (a to d are integers of 0 or more) is possible.

In addition to the above structural formula, if there is one second-generation phenylazomethine structure that binds to the first-generation, it becomes a dendron (2N-dendron) with two imines. In the following, 2 dendrons of imine (2N-dendron), 3 dendrons of imine (3N-dendron), 7 dendrons of imine (7N-dendron), and 15 dendrons of imine (15N-dendron) are shown. ..

By combining each dendrimer as described above, the imine number of each dendrimer can be controlled. The table below shows the relationship between 2N, 3N, 7N, 15N-dendrimers and the number of imines (10N-dendrimers to 17N-dendrimers) that can be synthesized by combining them.

The schematic structure of each dendrimer is as follows.

Although the 10N-dendrimers to 17N-dendrimers having 10 to 17 imines have been described above, the number of sites forming the cyclic structure represented by the formula (I) is not particularly limited, and the above combinations can be used. Based on this, for example, the number may be 60 or less, 30 or less, and 5 or more, 7 or more.

In the example below, a plurality of dendrimers are used as a method for producing a multi-alloy cluster, and a fragment is formed in the A fragment, b is formed in the B fragment, c is formed in the C fragment, and different metals are complex-formed at the imine site. Next, these are bonded to each other by a linker. As a result, a complex in which dissimilar metal salts A, B, C ... are accumulated in a dendrimer in a controlled number is formed. This dendrimer complex is used to synthesize A _a B _b C _c clusters. According to this method, the composition of the alloy cluster can be controlled at the atomic number level (a + b + c). In this method, two dendrimers may be complexed with a metal and then the dendrimers may be peptide bonded to each other, or one dendrimer may be complexed with a metal and then two dendrimers may be peptide bonded, followed by two dissimilar metals. It may be complexed with the dendrimer of the eye.

According to the present invention, as in the above-mentioned synthesis example of A ₆ B ₇ cluster and the above synthesis example of A _a B _b C _c cluster, the following methods capable of producing alloy particles in a controlled number are provided. Will be done.

The method for producing an aggregate of the present invention is a method for producing an aggregate in which a plurality of types of metal salt compounds having different metal types are integrated by controlling the number, and is any of the following [1] and [2]. Including the process.

[1] Two types of aggregate fragments (A1), (A1), in which metal salt compounds having a cyclic structure represented by the above formula (I) and having different metal species are accumulated in a phenylazomethine type dendrimer in a controlled number. A step of binding A2) between the cores of each phenylazomethine type dendrimer to form an integrated aggregate.

[2] An aggregate fragment (A1') in which the number of metal salt compounds is controlled and accumulated in a cyclic structure represented by the above formula (I), and a phenylazomethine-type dendrimer fragment in which no metal salt compound is accumulated (2). D1) is bound to each other in each core, and the imine site derived from the phenylazomethine-type dendrimer fragment (D1) in which the metal salt compound is not accumulated in the bound aggregate is derived from the aggregate fragment (A1'). A step of controlling the number of dissimilar metal salt compounds having a different metal species from the metal salt compounds accumulated at the imine site with a cyclic structure represented by the formula (I) and accumulating them.

In the above, the binding between the cores can be achieved by the above-mentioned linker. Therefore, it is preferable that the core has a reactive functional group capable of binding with a linker. For example, when the linker is a peptide bond, one core has an amino group and the other core has an ester group. When three or more cores are bonded, it is preferable that one core has two or more functional groups having this reactivity.

In a preferred example, the method for producing the aggregate further comprises any of the following steps [3] to [5].

[3] In the phenylazomethine type dendrimer, the number of metal salt compounds having a cyclic structure represented by the above formula (I) and having different metal types from the aggregates obtained in the above [1] or [2] is controlled. The aggregate fragment (A4) accumulated in the above and the aggregate fragment obtained in the above [1] or [2] are bound to each other in the cores of the respective phenylazomethine type dendrimers and integrated. Step of forming a body [4] An aggregate fragment which is an aggregate obtained in the above [1] or [2] and a phenylazomethine-type dendrimer fragment (D2) in which a metal salt compound is not accumulated are formed between cores. To the imine site derived from the phenylazomethine-type dendrimer fragment (D2) in which the metal salt compound is not accumulated, to the imine site derived from the aggregate obtained in the above [1] or [2]. Step of accumulating dissimilar metal salt compounds having different metal species from the accumulated metal salt compound by controlling the number in a cyclic structure represented by the formula (I) [5] Step of the above-mentioned [3] or [4]. After that, a step of optionally repeating the same operation as in [3] or [4] above.

Also in the above, the bonding between the cores can be achieved by the above-mentioned linker. Therefore, it is preferable that the core has a reactive functional group capable of binding with a linker. When three or more cores are bonded, it is preferable that one core has two or more functional groups having this reactivity.

In a preferred example, the method for producing the aggregate is to connect the cores in each of the three or more fragments in series in the steps [3] to [5]. As shown in the example of synthesizing A _a B _b C _c clusters described above, by connecting the cores in series, it is possible to bond a large number of fragments with the cores in series, and alloy particles composed of many kinds of dissimilar metals. Can be easily produced.

After obtaining an aggregate by the method for producing an aggregate as described above, the alloy particles having a controlled number can be obtained by reducing the aggregate. The reduction of the aggregate can be carried out in a gas phase or a solution using a reducing agent which has a reducing action on the metal salt compound and can reduce the metal salt compound to a zero-valent state, as described later. ..

The type and composition of the alloy particles are not particularly limited. The metal elements constituting the alloy particles are not particularly limited, and are, for example, titanium, vanadium, iron, cobalt, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, indium, and tin. , Antimon, hafnium, tantalum, tungsten, ruthenium, osmium, iridium, platinum, gold, mercury, bismuth and the like. Alloy particles having two or more kinds of metal elements such as these, and alloy particles composed of three or more kinds of metal elements can be produced by controlling the composition of dissimilar metals by selecting a dendrimer or the like. The alloy particles are not limited to sub-nano particles, and for example, according to the method of bonding the cores in series, alloy particles having a size larger than the sub-nano particles composed of many kinds of metal elements can be produced.

As described above, the aggregate of the present invention can be assumed to be an accumulation of dissimilar metal salt compounds, and among them, the number of each dissimilar metal can be controlled by the above-mentioned method. In a preferable example to which the above method can be applied, n in the phenylazomethine type dendrimer represented by the above formula (II) is an integer of 2 or more, and at least one of each of the n dendron units is Heterogeneous metal salt compounds with different metal types from other dendron units are accumulated.

The dendrimer can be manufactured by a convergent method or the like. The convergent method is a method in which branches are extended from the outside to the inside and finally bonded to the core to form a spherical polymer, and dendrimer synthesis is promoted inward from the outer shell of the dendrimer. Finally, some dendrons are bound to the core. In that case, for example, the reaction of an amino group and a carbonyl group is used, and in particular, 4,4'-diaminodiphenylmethane is reacted with a carbonyl group-containing compound to oxidize the methane moiety of 4,4'-diaminodiphenylmethane. By repeating the process of using a carbonyl group, the phenylazomethine-type dendrimer used in the present invention can be synthesized.

By reducing the aggregate of the present invention, sub-nanoparticles of the metal element can be produced.

The reduction of the metal salt compound aggregate of the dendrimer is carried out in a gas phase or a solution using, for example, a reducing agent having a reducing action on the metal salt compound and capable of reducing the metal salt compound to a zero-valent state. Can be done.

When reducing in the gas phase, it is supported on a carrier and the carrier is calcined in a hydrogen gas atmosphere. By supporting the metal salt compound aggregate of the dendrimer on the carrier, clusters can be formed without agglomeration. The shape of the carrier is not particularly limited, and may be various, such as granular, fibrous, granular, film-like, and plate-like. Considering that the surface area per unit mass is large and suitable for various uses such as catalysts, granular (powdered) is preferable. Examples of the carrier include carbon materials and inorganic materials. These carbon materials may be porous materials and can support clusters on the pore surface. The support on the carrier is carried out, for example, by using a solution in which a metal salt compound aggregate of dendrimer is dissolved in an appropriate solvent such as an organic solvent, contacting the carrier by impregnation, coating, dropping or the like, and then drying. be able to. This carrier is fired in a hydrogen gas or a mixed gas atmosphere with nitrogen containing hydrogen or argon.

When reducing in a solution, examples of the reducing agent include sodium borohydride, sodium borohydride, hydrogen, hydrazines, lithium aluminum borohydride, diisobutyl aluminum hydride, lithium borohydride, and tetra n borohydride. -Butylammonium, boron boromethylammonium hydride, lithium triethylborohydride, borane complexes, sodium triacetoxyboronate, zinc borohydride, lithium tributylborohydride borohydride, potassium tributylboron hydride, Schwartz reagent, Stryker reagent, hydrogenation Examples thereof include tributyltin, sodium borohydride, lithium borohydride, calcium hydride, benzophenone ketyl radicals, metal naphthalenides, hydrogen peroxide and the like.

By reducing the metal salt compound aggregate of the dendrimer in this way, sub-nanometal particles having a size corresponding to the number of accumulated metal salt compounds can be prepared. The term "sub-nano" here means that the particle size of the particles is, for example, in the range of 0.5 to 2.5 nm, especially in the range of 0.8 to 1.8 nm. A polyhedral atomic group formed by aggregating several atoms and directly bonding a part or all of them is generally called a cluster, and in that sense, sub-nanometal particles are clusters.

Such sub-nanometal particles may be supported on a carrier. By supporting the sub-nanometal particles on the carrier, it is possible to suppress the aggregation of the sub-nanometal particles and the like, and effectively suppress the decrease in catalytic activity when used as a catalyst, for example.

The shape of the carrier on which the cluster is supported is not particularly limited, and may be various, such as granular, fibrous, granular, film-like, and plate-like. Considering that the surface area per unit weight is large and suitable for a catalyst, granular (powdered) is preferable.

As the carrier, carbon materials such as carbon black (Ketjen black, oil furnace black, gas black, acetylene black, lamp black, thermal black, channel black, etc.), activated carbon, carbon fiber and other amorphous (microcrystals) Examples thereof include nanocarbons such as carbon, fullerene, nanotubes, graphene and graphene oxide, three-dimensional crystals such as graphite, and graphitized mesoporous carbon. These carbon materials may be porous materials and can support single element clusters on the pore surface.

In addition, an inorganic material can be used as the carrier. Examples of the inorganic material include silica gel, alumina, titania, magnesia, zirconia, iron oxide, copper oxide, glass, silica sand, talc, mica, clay, and wallusnite.

Preferred carriers in terms of carrier internal area, affinity, versatility, stability and durability include Ketjenblack (KB), graphitized mesoporous carbon (GMC), graphene oxide (GO) and aluminum oxide (Al ₂ O). ₃ ) etc. can be mentioned.

In the case of reduction in the gas phase, the support on the carrier can be carried out by supporting the aggregate of the present invention on the carrier and calcining the carrier in a hydrogen gas atmosphere. When reducing in a solution, a carrier in which a dendrimer containing reduced sub-nanometal particles is dissolved in an appropriate solvent such as an organic solvent is used, and the carrier is mixed, impregnated, coated, dropped, etc. with a carrier dispersion. It can be done by contacting with and then drying. If necessary, a pulverization treatment may be performed.

The sub-nanometal particles obtained from the metal salt compound aggregate of the phenylazomethine type dendrimer of the present invention can be used as a material for various fields including catalysts, for example, pharmaceuticals, electronic functional materials, environment-friendly materials, luminescent materials and the like. Expected to be applied.

Hereinafter, 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>
Using the compound (G0) that is a partial structure of the dendrimer and the pentacyclopentadienyl iridium (III) dichloride dimer ([Cp ^* IrCl ₂ ] ₂ ) in the presence of sodium acetate, an iridium complex is used in the following scheme. Was synthesized.

FIG. 1 (a) is a mass spectrum of the product measured by MALDI-TOF-MS, and FIG. 1 (b) is a ¹ H-NMR spectrum of the product and compound G0. FIG. 2 is a ¹ H-NMR spectrum of a product synthesized in the presence of sodium acetate and a product synthesized without the addition of sodium acetate.

In the above scheme, the isolated yield was 52%, and the reaction proceeded almost 100%.

When the products with and without sodium acetate, which promote the formation of cyclized complexes, were confirmed by NMR during the synthesis, benzophenone, which is a decomposition product of the dendrimer, was a by-product when it was not used. It was found that many of them occurred (Fig. 2). Since benzophenone was not produced in the solution containing only the dendrimer, it is considered that this was caused by the decomposition of the iridium complex generated during the reaction. On the other hand, no benzophenone was produced in the reaction using sodium acetate, and it can be said that the stability of the cyclized complex to water is significantly higher than that of the non-cyclized complex.

Regarding the stability of the cyclized complex, the reaction mechanism in the presence of sodium acetate is presumed as follows. The acetic acid ligand on iridium rapidly forms a cyclized complex by CH activation. There are many reports of acetate ions promoting the cyclization reaction (eg, Lutz Ackermann Chem. Rev. 2011, 111, 1315-1345.).

On the other hand, the reaction mechanism in the absence of sodium acetate is presumed as follows. Since the cyclization reaction is slow, it is considered that the hydrolysis reaction due to residual water competes and benzophenone is produced.

In addition to the above, in the following scheme, the compound (G0) that is a partial structure of the dendrimer, pentacyclopentadienyl rhodium (III) dichloride dimer ([Cp ^* RhCl ₂ ] ₂ ), and dichlorobis (dimethyl sulfoxide) platinum (II) (PtCl ₂ (dmso) ₂ ) was used for synthesis in the presence of sodium acetate. In addition to the above iridium complex (upper), rhodium complex (middle) and platinum complex (lower) were confirmed to be synthesized.

<Example 2>
The G0-Ir complex synthesized in Example 1 was heated and calcined under a hydrogen stream under the conditions of 3% H ₂ / Ar, 300 ° C., and 3 hours to reduce the gas phase. FIG. 3 is an X-ray photoelectron spectroscopic spectrum before and after the reduction of the G0-Ir complex. From the valence evaluation of Ir by X-ray photoelectron spectroscopy, it was confirmed that the iridium complex can be converted into metallic iridium.

<Example 3>
Using a dendrimer having two imine nitrogens and a pentacyclopentadienyl iridium (III) dichloride dimer ([Cp ^* IrCl ₂ ] ₂ ), an iridium dimer complex was synthesized in the presence of sodium acetate by the following scheme. ..

FIG. 4 shows the crystal structure of the product by X-ray crystal structure analysis. The structure is as described in the above scheme, and C and Ir are combined. The synthesis of the iridium dinuclear complex was confirmed.

<Example 4>
In the presence of sodium acetate using a second generation phenylazomethine dendrimer (tetraphenylmethanecore G2) with 12 imines and a pentacyclopentadienyl iridium (III) dichloride dimer ([Cp ^* IrCl ₂ ] ₂ ). The iridium 12-nuclear complex was synthesized by the following scheme. A product was obtained by liquid separation operation, column chromatography, and reprecipitation.

FIG. 5 (a) is a mass spectrum of the product measured by MALDI-TOF-MS, and FIG. 5 (b) is a transmission electron microscope image of the product. In (b), 12 bright spots indicate 12 Ir atoms. The synthesis of the iridium 12-nuclear complex was confirmed.

<Example 5>
In the presence of sodium acetate using a second generation phenylazomethine dendrimer (tetraphenylmethane core G2) with 12 imines and a pentacyclopentadienyl rhodium (III) dichloride dimer ([Cp ^* RhCl ₂ ] ₂ ). The reaction was carried out. A product was obtained by liquid separation operation, column chromatography, and reprecipitation.

FIG. 6 is a mass spectrum of the product measured by MALDI-TOF-MS. As with iridium, the accumulation of rhodium in dendrimers was also confirmed.

<Example 6>
The reaction was carried out in the presence of sodium acetate using a second-generation phenylazomethine dendrimer (tetraphenylmethane core G2) having 12 imines and dichlorobis (dimethyl sulfoxide) platinum (II) (PtCl ₂ (dmso) ₂ ). It was. A product was obtained by liquid separation operation, column chromatography, and reprecipitation.

FIG. 7 (a) is a mass spectrum of the product measured by MALDI-TOF-MS, and FIG. 7 (b) is a HAADF-STEM image of the surface on which the product is supported on a carrier. As with iridium and rhodium, the accumulation of platinum in the dendrimer was also confirmed.

<Example 7>
The reduction conditions of the iridium 12-nuclear complex were examined. The iridium 12-nuclear complex synthesized in Example 4 was applied onto a Si wafer and immobilized. Next, the immobilized iridium 12-nuclear complex was subjected to heat calcination under a hydrogen stream at a temperature and time of 3% H ₂ / Ar to reduce the gas phase.

FIG. 8 is an X-ray photoelectron spectroscopic spectrum after hydrogen reduction. It can be reduced in 5 hours at 270 ° C. and in 10 min. At a temperature of 350 ° C. or higher.

<Example 8>
The iridium 12-nuclear complex synthesized in Example 4 was immobilized on a carrier by the following scheme. As the carrier, graphene nanopowder, Ketjen black and the like were used.

Next, the iridium 12-nuclear complex immobilized on the carrier was heated and calcined under a hydrogen stream under the conditions of 3% H ₂ / Ar, 350 ° C., and 10 minutes to reduce the gas phase.

FIG. 9 is an X-ray photoelectron spectroscopy spectrum of the G2-Ir12 nuclear complex before reduction, after vacuum treatment, and after hydrogen reduction. The results are shown before the reduction of the G2-Ir12 nuclear complex, after the heat-calcination treatment in vacuum, and after the heat-calcination treatment under a 3% H ₂ / Ar air flow. It was confirmed that the iridium 12-nuclear complex can be converted into metallic iridium by heating under a hydrogen stream.

FIG. 10 is a HAADF-STEM image of the surface carrying the iridium 12-nuclear complex (left) and the surface after reduction (right). In the image on the left, there is a complex at the location indicated by ○. Sub-nanoparticle formation of the iridium 12-nuclear complex was confirmed.

<Example 9>
The following 10N-dendrimers to 17N-dendrimers were used to synthesize iridium 10-17 nuclear complexes.

Scheme S1: Synthesis of phenylazomethindendrone

Pre-LG2on (general procedure for dehydration reaction with TiCl ₄ )
Benzophenone (19.9 g, 109.1 mmol), 4-benzylaniline (20 g, 109.1 mmol), 4-diazabicyclo [2.2.2] octane (DABCO) (73.4 g, 654.6 mmol) was dissolved in chlorobenzene (500 ml) at 90 ° C. Heated to. TiCl ₄ (17.4 ml, 163.6 mmol) dissolved in 40 ml of chlorobenzene was added dropwise, and the dropping funnel was rinsed with 5 ml of chlorobenzene. The mixture was heated to 125 ° C. and stirred under an argon atmosphere for 4.5 hours. The reaction mixture was cooled to room temperature, stirred in air overnight and then filtered through Celite. The filtrate was concentrated and the product was filtered through silica gel. The product pre-LG 2 on was obtained by recrystallization from tetrahydrofuran / methanol.
^{1 1} HNMR (400 MHz, CDCL ₃ , 21.0 ° C, TMS): δ = 7.73 (2H, d, J = 7.12 Hz), 7.44 (1H, t, J = 7.24 Hz), 7.38 (2H, t, J = 7.36) Hz), 7.28 --7.23 (5H, m), 7.16, (1H, t, J = 7.30 Hz) 7.09, (4H, t, J = 7.46 Hz), 6.94, (2H, d, J = 8.24), 6.65 (2H, d, J = 8.28 Hz).

LG2on (general procedure for oxidation reaction with KMnO ₄ )
Pre-LG2on (23.0 g, 66.2 mmol) and TBABr (29.0 g, 90.0 mmol) were dissolved in 1,2-dichloroethane (300 ml). KMnO ₄ (14.2 g, 90.0 mmol) was then added to the solution on the ice bath. The reaction was gradually returned to room temperature and stirred for 1 week. Then, the reaction was stopped with an aqueous sodium hydrogen sulfite solution. The mixture was separated and extracted with chloroform. The organic layer was washed with brine, then dried over sodium sulfite and concentrated. The product was filtered through silica gel and recrystallized from tetrahydrofuran / methanol.
^{1 1} HNMR (400 MHz, CDCl ₃ , 21.0 ° C, TMS): δ = 7.76 (2H, d, J = 7.04 Hz), 7.70 (2H, d, J = 8.48 Hz), 7.65 (2H, d, J = 8.48) Hz), 7.54 --7.41 (6H, m), 7.25, (3H, bs) 7.12, (2H, bs), 6.79 (2H, d, J = 8.48 Hz). 6.94, (2H, d, J = 8.24) , 6.65 (2H, d, J = 8.28 Hz).

G2on was prepared according to the literature.

Scheme S2: Synthesis of Half-Phenylazomethine dendrimer

Synthesis of Half-DPAG3 G3on (3.7 g, 2.9 mmol), p-phenylenediamine (1.08 g, 10 mmol) and DABCO (1.35 g, 12 mmol) were dissolved in chlorobenzene (30 mL) according to the general procedure of dehydration reaction. TiCl ₄ (0.32 ml, 3 mmol) was added and the mixture was stirred at 125 ° C. for 3 hours. The product (Half-DPAG3) was isolated by preparative GPC. Yield: 43% (1.71 g, 1.27 mmol). The product (Half-DPAG3) was isolated by preparative GPC. Yield: 43% (1.71 g, 1.27 mmol).

Synthesis of G2-DPAG3
Half-DPAG3on (0.67 g, 0.5 mmol), G2on (0.27 g, 0.5 mmol) and DABCO (0.42 g, 3.7 mmol) were dissolved in chlorobenzene (20 mL). TiCl ₄ (0.1 ml, 0.94 mmol) was added dropwise and the mixture was stirred at 125 ° C. for 2.5 hours. The mixture was cooled to room temperature and vigorously stirred in air to stop the reaction. The precipitate was removed by filtration through Celite and silica and the filtrate was concentrated. The product (G2-DPAG3) was isolated by preparative GPC. Yield: 44% (0.41 g, 0.22 mmol).
^{1 1} H NMR (400 MHz, CD ₂ Cl ₂ , 21.5 oC, TMS): δ = 7.81-6.46 (96H, m).

Scheme S4: Synthesis of triphenylbenzene core (TPB) phenylazomethine dendrimer

Synthesis of TPB core
G3on (1.65 g, 1.31 mmol), tris (4-aminophenyl) benzene (0.92 g, 2.62 mmol) and DABCO (1.03 g, 9.2 mmol) were dissolved in chlorobenzene (30 mL). TiCl ₄ (0.25 ml, 2.36 mmol) was added dropwise and the mixture was stirred at 125 ° C. for 3.5 hours. The mixture was cooled to room temperature and vigorously stirred in air to stop the reaction. The precipitate was removed by filtration through Celite and silica and the filtrate was concentrated. Products (NH _2- TPB2G3, 2NH _2- TPBG3) were isolated by preparative GPC.
^{1 1} H NMR (400 MHz, CD ₂ Cl ₂ , 21.5 oC, TMS): δ = 7.70-6.41 (143H, m), 3.70 (2H, s).
2NH ₂ -TPBG3;
^{1 1} H NMR (400 MHz, CD ₂ Cl ₂ , 21.5 oC, TMS): δ = 7.31-6.42 (96H, m) 3.72 (4H, s).

General procedure for synthesizing R-DPB2G3 (R = LG2on, G2on)
NH _2- TPB2 G3on (0.28 g, 0.1 mmol), G2on (0.16 g, 0.2 mmol) and DABCO (0.6 g, 5.4 mmol) were dissolved in chlorobenzene (20 mL). After heating the reaction solution in an oil bath at 125 ° C., chlorobenzene (3 ml) and TiCl ₄ (95 μl, 0.9 mmol) were added dropwise. After an additional 2 hours, the mixture was cooled to room temperature and vigorously stirred in air to stop the reaction. The precipitate was removed by filtration through Celite and silica and the filtrate was concentrated. The product (G2-TPB2G3) was isolated by preparative GPC.
G2-TPB2G3; ^{1 1} H NMR (400 MHz, CD ₂ Cl ₂ , 21.5 oC, TMS): δ = 7.80-6.55 (171H, m).
LG2-TPB2G3; ^{1 1} H NMR (400 MHz, CD ₂ Cl ₂ , 21.5 oC, TMS): δ 7.82-6.55 (162H, m).

General procedure for synthesizing 2R-DPBG3 (R = LG2on, G2on)
2NH _2- TPBG3on (0.24 g, 0.15 mmol), G2on (0.21 g, 0.4 mmol) and DABCO (0.6 g, 5.4 mmol) were dissolved in chlorobenzene (20 mL). The reaction mixture was heated in an oil bath at 125 ° C., then chlorobenzene (3 ml) and TiCl ₄ (95 μl, 0.9 mmol) were added dropwise. After an additional 3.5 hours, the mixture was cooled to room temperature and vigorously stirred in air to stop the reaction. Precipitates were removed by filtration through Celite and silica and concentrated. The product (2G2-TPBG3) was isolated by preparative GPC.
2G2-TPBG3; ^{1 1} H NMR (400 MHz, CD ₂ Cl ₂ , 21.5 oC, TMS): δ = 7.81-6.55 (193H, m).
2LG2-TPBG3; ^{1 1} H NMR (400 MHz, CD ₂ Cl ₂ , 21.5 oC, TMS): δ = 7.67-6.40 (117H, m).

The reaction was carried out in the presence of sodium acetate using each phenylazomethine dendrimer and a pentacyclopentadienyl iridium (III) dichloride dimer ([Cp ^* IrCl ₂ ] ₂ ). A product was obtained by liquid separation operation, column chromatography, and reprecipitation.

FIG. 11 is a mass spectrum of the product measured by MALDI-TOF-MS. It was confirmed that Ir was formed almost quantitatively with respect to the dendrimer having an imine number of 10 to 17.

<Example 10>
Pentacyclopentadienyl iridium (III) dichloride dimer ([Cp ^* IrCl ₂ ] ₂ ) and pentacyclopentadienyl rhodium ([Cp ^* IrCl ₂ ] ₂ ) using a first-generation phenylazomethine dendrimer (tetraphenylmethane core G1) with four imines. III) The reaction was carried out with a dichloride dimer ([Cp ^* RhCl ₂ ] ₂ ) in the presence of sodium acetate in one step. A product was obtained by liquid separation operation, column chromatography, and reprecipitation.

FIG. 12 is a mass spectrum of the product measured by MALDI-TOF-MS. It was confirmed that different metal atoms can be accumulated in one molecule of dendrimer by forming iridium and rhodium at the same time. In (2,2), two iridiums and two rhodiums are coordinated, in (3,1), three and one iridium and one rhodium are coordinated, and in (4,0), four iridiums are coordinated. It shows that it is. By changing the type of salt of the two types of metal, it is possible to control the combination of the two types of metal.

<Example 11>
Pentacyclopentadienyl iridium (III) dichloride dimer ([Cp ^* IrCl ₂ ] ₂ ) and pentacyclopentadienyl rhodium (III) using a 4th generation phenylazomethine dendrimer (benzene core G4) with 4 imines. The reaction was carried out with a dichloride dimer ([Cp ^* RhCl ₂ ] ₂ ) sequentially in two steps in the presence of sodium acetate. A product was obtained by liquid separation operation, column chromatography, and reprecipitation.

FIG. 13 is a mass spectrum of the product measured by MALDI-TOF-MS. It was confirmed that different metal atoms can be accumulated in one molecule of dendrimer by sequentially complexing iridium and rhodium. By changing the type of salt of the two types of metal, it is possible to control the combination of the two types of metal.

<Example 12>
In order to investigate the stability of the iridium complex, a single crystal of the iridium complex synthesized in Example 1 was prepared. FIG. 14 is a photomicrograph of crystals obtained from a water-methanol solution. Stable single crystals were obtained with less oxidation and decomposition in water and air.

<Example 13>
The following 7N-dendrimer was used to synthesize an iridium 7-nuclear rhodium 7-nuclear complex.
G3-NH ₂ and (IrCl ₂ Cp ^* ) ₂ were reacted in the presence of NaOAc in the solvent DMF / MeOH at room temperature for 1 week to obtain 7IrClCp ^* @ G3-NH ₂ . Next, 7IrClCp ^* @ G3-NH ₂ and terephthalic acid dichloride were reacted in dichloromethane as a solvent in the presence of DMAP (N, N-dimethyl-4-aminopyridine) for 20 hours at room temperature, and 7IrClCp ^* @ G3- COCl was obtained. 7IrClCp ^* @ G3-COCl and G3-NH ₂ were reacted in the solvent dichloromethane in the presence of DMAP for 20 hours at room temperature to obtain 7IrClCp ^* @ G3-CONH-G3.

7IrClCp ^* @ G3-CONH-G3 and (RhCl ₂ Cp ^* ) ₂ were reacted in the presence of NaOAc in the solvent DMF / MeOH at room temperature for 1 week, and the alloy complex 7IrClCp ^* @ G3-CONH-7RhClCp ^* @ I got G3. A crude product yield of 16.9 mg (89%) was recovered.

FIG. 15 is a mass spectrum of the iridium 7-nuclear rhodium 7-nuclear complex measured by MALDI-TOF-MS, and FIGS. FIG. 17 is an electron microscope observation image (HAADF-STEM) of the iridium 7-nuclear rhodium 7-nuclear complex showing the number of atoms in an enlarged scale. For these, samples were prepared and observed according to the following procedure. The carrier was dispersed in acetone by ultrasonic irradiation. As the carrier, graphene nanopowder, Ketjen black and the like were used. An acetone solution of an iridium 7-nuclear rhodium 7-nuclear complex was added to this dispersion (0.5 mg / mL), and ultrasonic dispersion treatment was further carried out for 1 hour. The dispersion was filtered and vacuum dried to obtain a sample.

<Example 14>
Clustering of the iridium 7-nuclear rhodium 7-nuclear complex was carried out by the following procedure. The iridium 7-nuclear rhodium 7-nuclear complex immobilized on the carrier was heat-treated under the conditions of 450 ° C. and 10 min in an H ₂ atmosphere to reduce the gas phase.

18 (a) and 18 (b) show electron microscopic observation images (HAADF-STEM) of Ir ₇ Rh ₇ alloy clusters, FIGS. 19 (a) to 19 (d), and FIGS. 20 show the results of STEM-EDX analysis of alloy clusters. Shown. STEM photographs were observed by adding the clustered solution directly to the STEM grid.

<Example 15>
The HER activity of the Ir cluster was measured. The hydrogen generation reaction activity was compared using sub-nanoparticles prepared according to the above-mentioned Examples such as Example 9 in which the number of iridium metals was precisely controlled from 11 to 17. The measurement used an electrochemical measurement method.

-Sample Ir n / KB ₍ 0.2 wt% Ir, n = 11 to 17 KB is Ketjen black)
・ Measurement sample preparation
(1) The instruments used (volumetric flask, beaker, vial, special tweezers, electrochemical cells) were boiled and washed with a 25% dilute aqueous nitric acid solution. The above instruments were boiled and washed with ultrapure water three times.
(2) 19 mL of ultrapure water, 2-propanol (spectroscopic grade), and 0.1 mL of 5% Nafion dispersion were added to the vial, and the mixture was stirred with ultrasonic waves for 5 minutes.
(3) 3.5 mg of Ir cluster sample (Irn / K.b.) was weighed into a vial. 4.750 mL of the above mixed solvent was added thereto, and the mixture was stirred with ultrasonic waves for 5 minutes. If large lumps remained, ultrasonic agitation was added. This was done until the whole was uniform and there were no lumps.
(4) While rotating the glassy carbon (GC) electrode polished with alumina paste at a rotation speed of 500 rpm, 4.8 μL of catalyst ink was dropped on the center of the electrode using a micropipette. It was left to rotate for 15 minutes (until the ink dries). The same operation was performed twice later (three times in total), and a total of 14.4 μL was added dropwise.
・ Measuring equipment Potentiostat: ALS 440 Electrochemical Analyzer & ALS 750A Electrochemical Analyzer (manufactured by BAS Co., Ltd.)
Working electrode: Ir _{n /} KB modified GC electrode (φ6 mm)
Counter electrode: Pt wire Reference electrode: Standard hydrogen electrode Electrolyte: 0.1M HClO ₄ aqueous solution (SUPrapur grade perchloric acid (60%) 1.088 mL manufactured by MERCK) is added to a 100 mL volumetric flask, and ultrapure water is used. The electrolyte solution was prepared by measuring up.)
·Measurement procedure
(1) An electrolyte solution was added to the cell, degassed with argon for 15 minutes, and then the hydrogen generation reaction was measured under the following conditions. (Raw)
Initial potential: 0.2V
Final potential: 0.3V
Sweep speed: 2 mV / s
Rotational speed of electrodes: 3000 rpm
(2) Electrochemical annealing of the catalyst was performed by cyclic voltammetry measurement under the following conditions.
Initial potential: 0.1V
High potential: 1.0V
Low potential: 0.06V
Sweep speed: 100 mV / s
Sweep segment: 21
The hydrogen generation reaction measurement was performed again under the following conditions. (Annealed)
Initial potential: 0.2V
Final potential: 0.3V
Sweep speed: 2 mV / s
Rotational speed of electrodes: 3000 rpm

21 and 22 show the measurement results of the HER activity of the Ir cluster. FIG. 21 is before annealing (raw), and FIG. 22 is after annealing (annealed). As a result, the sub-nanoparticles of Ir ₁₃ had the highest activity. By accurately controlling the number of metals, the difference in catalytic activity depending on the number of metals could be confirmed accurately.

<Example 16>
The HER activity of Ir single metal sub-nanoparticles and two types of metal alloy sub-nanoparticles Ir and Rh were compared. The number of metal atoms was unified to 14. Ir ₇ Rh ₇ sub-nanoparticles were prepared according to Example 14.

FIG. 23 shows the measurement results of the HER activities of Ir ₇ Rh ₇ and Ir ₁₄ in comparison. The alloyed Ir ₇ Rh ₇ had improved hydrogen generation reaction activity as compared with Ir ₁₄ .

Claims (10)

An aggregate in which a metal salt compound is accumulated in a phenylazomethine type dendrimer with a cyclic structure represented by the following formula (I):
(In the formula, MR indicates the metal salt compound, M indicates a metal atom, R indicates the chemical structure of the residue thereof. In the imine nitrogen atom and carbon atom forming an azomethin bond in the phenylazomethine structure, and the carbon atom. The cyclic structure is formed between the phenyl ring to be bonded and the metal atom M of the metal salt compound). The aggregate according to claim 1, wherein the metal salt compound is accumulated in a phenylazomethine type dendrimer represented by the following formula (II):
(In the equation, A represents an n-valent organic group that is the core of the dendrimer, n represents an integer of 1 or more. When n is 2 or more, each of the n dendron units is independent. X is the following. Indicates X ¹ or X ² represented by the formula.
(In the formula, Ph ^a represents ^a divalent phenyl residue that may have ^a substituent.)
(In the formula, Ph ^b indicates a monovalent phenyl residue which may have a substituent.)
In the repeating unit rep, when X is X ¹ , the repeating unit rep is repeated, the end of the repeating unit rep is X ² , and all Xs in the repeating unit rep are independent. All Ph ^a and Ph ^b substituents are independent. ). The aggregate according to claim 1 or 2, wherein the dissimilar metal salt compound is accumulated. In the phenylazomethine type dendrimer represented by the above formula (II), n is an integer of 2 or more, and at least one of each of the n dendron units is a dissimilar metal salt having a metal type different from that of other dendron units. The aggregate according to claim 2, wherein the compound is accumulated. A method for producing sub-nanometal particles, which reduces the aggregate according to any one of claims 1 to 4. A method for controlling the number of metal atoms accumulated in a phenylazomethine-type dendrimer using the aggregate according to claim 3 or 4 .
By selecting the valence n of the organic group A and the repeating unit rep in the phenylazomethine type dendrimer represented by the formula (II), the number of the metal atoms to be accumulated corresponds to the target number. The step of synthesizing the phenylazomethine type dendrimer having a site forming a cyclic structure, and
A method including a step of accumulating the target number of the dissimilar metal salt compounds at a site forming the cyclic structure. A method for producing an aggregate in which a plurality of types of metal salt compounds having different metal types are accumulated by controlling the number, including any of the following steps [1] and [2].
[1] For a phenylazomethine type dendrimer, the following formula (I):
(In the formula, M-R indicates the metal salt compound, M indicates a metal atom, R indicates the chemical structure of the residue thereof. In the imine nitrogen atom and carbon atom forming an azomethine bond in the phenylazomethine structure, and the carbon atom. The cyclic structure is formed between the phenyl ring to be bonded and the metal atom M of the metal salt compound.) The number of metal salt compounds having different metal species from each other is controlled. The two types of aggregate fragments (A1) and (A2) that have been accumulated are bonded to each other by the cores of the respective phenylazomethine-type dendrimers to form an integrated aggregate, which is represented by the step [2] formula (I). The aggregate fragment (A1') in which the number of metal salt compounds is controlled and accumulated in the cyclic structure and the phenylazomethine-type dendrimer fragment (D1) in which the metal salt compound is not accumulated are bonded to each other in each core. , What is the metal salt compound accumulated in the imine moiety derived from the phenylazomethine type dendrimer fragment (D1) in which the metal salt compound is not accumulated in the bound aggregate, and in the imine moiety derived from the aggregate fragment (A1')? A step of controlling the number of dissimilar metal salt compounds having different metal types and accumulating them in a cyclic structure represented by the formula (I). The method for producing an aggregate according to claim 7, further comprising any of the following steps [3] to [5].
[3] In the phenylazomethine type dendrimer, the number of metal salt compounds having a cyclic structure represented by the above formula (I) and having different metal types from the aggregates obtained in the above [1] or [2] is controlled. The aggregate fragment (A4) accumulated in the above and the aggregate fragment obtained in the above [1] or [2] are bound to each other in the cores of the respective phenylazomethine type dendrimers and integrated. Step of forming a body [4] An aggregate fragment which is an aggregate obtained in the above [1] or [2] and a phenylazomethine-type dendrimer fragment (D2) in which a metal salt compound is not accumulated are formed between cores. To the imine site derived from the phenylazomethine-type dendrimer fragment (D2) in which the metal salt compound is not accumulated, to the imine site derived from the aggregate obtained in the above [1] or [2]. Step of accumulating dissimilar metal salt compounds having different metal species from the accumulated metal salt compound by controlling the number in a cyclic structure represented by the formula (I) [5] Step of the above-mentioned [3] or [4]. After that, a step of optionally repeating the same operation as in [3] or [4] above. The method for producing an aggregate according to claim 8, wherein in the steps [3] to [5], the cores of each of the three or more fragments are connected in series. A method for producing alloy particles, wherein an aggregate is obtained by the method according to any one of claims 7 to 9, and then the aggregate is reduced to obtain an alloy particle having a controlled number.