JP2022044012A - Metal nanocluster - Google Patents

Abstract

To provide a metal nanocluster, such as silver, having high stability, and to provide a method for preparing such a metal nanocluster.SOLUTION: A composite metal nanocluster comprises a metal nanocluster and a multimer of a heteropolyoxometalate anion containing a defective structure moiety represented by a compositional formula [YZ9O34]n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and n is 9 or 10). At least a portion of an outer surface of the metal nanocluster is enclosed within the multimer, and the metal is selected from silver or platinum.

Description

There is an application for exception of loss of novelty

The present invention relates to a composite metal nanocluster containing a metal nanocluster and a heteropolyoxometallate anion containing a defective structure site, and a method for synthesizing the composite metal nanocluster.

Metal nanoclusters, which have precise structures at the atomic level, are of wide interest in the field of advanced materials because they have unique properties based on quantum size and can be applied to various fields such as photocatalytic properties, catalytic properties, and imaging. I'm collecting. Silver (Ag) nanoclusters in particular have recently gained increasing attention due to their interesting geometric and electronic structures, in addition to their usefulness in interdisciplinary fields such as luminescence, imaging and catalysts. There is.

So far, pioneering research on the X-ray crystal structure of gold (Au) nanoclusters has been made (Non-Patent Document 1), and following this, a wide variety of synthetic methods for these materials have been developed (Non-Patent Document 1). 2, 3). In contrast to the study of gold nanoclusters, the chemistry of silver nanoclusters has not been well studied. The first X-ray crystallography of {Ag ₃₄ } nanoclusters has been reported by Sun and Zheng (Non-Patent Document 4), and since this original discovery, several silver nanoclusters with well-defined structures have been synthesized. (For example, Non-Patent Documents 5 and 6).
However, conventional silver nanocluster synthesis methods have been largely limited to simple one-step reduction methods of silver cations (Ag ⁺ ) in the presence of organic ligands due to the low stability of these materials. .. The low stability of the silver nanoclusters obtained by such a method typically impedes their synthesis and application due to the immediate aggregation of the nanoclusters into nanoparticles.

In this way, silver nanoclusters obtained by conventional technology are extremely unstable and easily decompose, so a method for synthesizing silver nanoclusters by precisely controlling the structure and electronic state and maintaining them stably. Was sought after.

Jadzinsky, P. D .; Calero, G .; Ackerson, C. J .; Bushnell, D. A .; Kornberg, R. D., Science 2007, 318, 430-433. Chakraborty, I .; Pradeep, T., Chem. Rev. 2017, 117, 8208-8271. Kurashige, W .; Niihori, Y .; Sharma, S .; Negishi, Y., Chem. Rev. 2016, 320-321, 238-250. Sun, D .; Luo, G.-G .; Zhang, N .; Huang, R.-B .; Zheng ,, Chem. Commun. 2011, 47, 1461-1463. Yang, H .; Lei, J .; Wu, B .; Wang, Y .; Zhou, M .; Xia, A .; Zheng, L .; Zheng ,, Chem. Commun. 2013, 49, 300-302. Shen, X.-T .; Ma, X.-L .; Ni, Q.-L .; Ma, M.-X.,; Gui, L.-C .; Hou, C .; Hou, R. -B., Nanoscale 2018, 10, 515-519.

An object of the present invention is to provide metal nanoclusters such as silver having high stability. It is also an object of the present invention to provide a method for preparing such metal nanoclusters.

Polyoxometallates (POMs) are bulky anionic metal-oxoclusters with unique structures and properties such as acidic / basic, electronic states, and redox properties. The inventors conceived that POM could act as a structure-oriented unit for metal clusters such as reactive polynuclear silver by protecting the metal clusters from unwanted aggregation and stabilizing the clusters. did. And we have the potential to result in novel POM-based nanomaterials with unique geometric and / or electronic structures that cannot be achieved with conventional flexible organic ligands. As a result of diligent studies, the present invention has been completed.

That is, the present invention
[1] Metal nanoclusters and
[YZ ₉ O ₃₄ ] In the composition formula of ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and n is 9 or 10). It contains a multimers of terror polyoxometallate anions and contains defective structural sites.
At least a part of the outer surface of the metal nanocluster is encapsulated inside the multimer.
The metal is a composite metal nanocluster selected from silver or platinum.
[2] The multimer is a dimer of a heteropolyoxometallate anion containing a defective structure site, a dimer of a heteropolyoxometallate anion containing one or more other defective structure sites, and / or. The composite metal nanocluster according to [1], which is formed by condensing a heteropolyoxometallate anion containing one or more defective structure sites.
[3] The composite metal nanocluster according to [1] or [2], wherein the metal is silver.
[4] The composite metal nanocluster according to any one of [1] to [3], wherein the heteropolyoxometallate anion containing the defective structure site is represented by [SiW ₉ O ₃₄ ] ^10- .
[5] The composite metal nanocluster according to [4], wherein the dimer is represented by [Si ₂ W ₁₈ O ₆₆ ] ^16- .
[6] The composite metal nanocluster according to any one of [1] to [5], wherein the multimer is composed of a dimer of a heteropolyoxometallate anion containing three defective structure sites.
[7] The multimer is composed of a dimer of a heteropolyoxometallate anion containing one defective structure site and a heteropolyoxometallate anion containing one defective structure site.
The composite metal nanocluster according to any one of [1] to [5].
[8] Formula: [Ag ₂₇ (Y ₂ Z ₁₈ O ₆₆ ) ₃ ] A compound containing an anion represented by ^s- .
(In the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and s is selected from an integer from 25 to 31).
[9] The compound according to [8] having the composition of X _s [Ag ₂₇ (Y ₂ Z ₁₈ O ₆₆ ) ₃ ] (in the formula, X represents a counter cation, and even if they are the same pair cation, they are different. It may be anti-cation).
[10] [Ag ₇ (Y ₃ Z ₂₇ O ₉₆ )] A compound containing an anion represented by ^t- .
(In the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and t is selected from an integer from 10 to 13).
[11] The compound according to [10] having the composition of _Xt [Ag ₇ (Y ₃ Z ₂₇ O ₉₆ )] (in the formula, X represents a counter cation, and even if they are the same pair cation, they are different pairs. It may be a cation).
[12] With silver nanoclusters
[YZ ₉ O ₃₄ ] In the composition formula of ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and n is 9 or 10). It contains a multimer in which three dimers of heteropolyoxometallate anion are condensed, and at least a part of the outer surface of the silver nanocluster is encapsulated inside the multimer. , A method for preparing composite silver nanoclusters,
(A) A step of providing a mixture of AgL (where L represents a counter anion) and an organic solvent,
(B) In the mixture, the composition formula of [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, n is 9). Alternatively, by adding a compound containing a telopolyoxometallate anion containing a defective structure site represented by 10), the composition formula of [Ag ₂ (Y ₂ Z ₁₈ O ₆₆ )] ^m- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo and m is 14 or 16) to contain the defect structure site containing the two Ag ⁺ cations. The preparation method comprising a step of obtaining a dimer of telopolyoxometallate anion and (c) a step of adding a reducing agent and AgL (L represents a counter anion) to a solution containing the dimer.
[13] With silver nanoclusters
[YZ ₉ O ₃₄ ] In the composition formula of ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and n is 9 or 10). It contains a multimer in which three dimers of heteropolyoxometallate anion are condensed, and at least a part of the outer surface of the silver nanocluster is encapsulated inside the multimer. , A method for preparing composite silver nanoclusters,
(D) A step of providing a mixture of AgL (where L represents a counter anion), an organic solvent and water.
(E) In the mixture, the composition formula of [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, n is 9). Or 10), a step of adding a compound containing a telopolyoxometallate anion to the defect structure site, and (f) after stirring for a predetermined time, a reducing agent and AgL (L is a counter anion). The preparation method comprising the step of adding (represented).
[14] With silver nanoclusters
[YZ ₉ O ₃₄ ] In the composition formula of ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and n is 9 or 10). A complex silver nano that contains a multimer in which three heteropolyoxometallate anions are condensed, and at least a part of the outer surface of the silver nanocluster is encapsulated inside the multimer. It ’s a method of preparing clusters.
(G) A step of providing a mixture of AgL (where L represents a counter anion) and an organic solvent,
(H) In the mixture, the composition formula of [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, n is 9). Alternatively, by adding a compound containing a telopolyoxometallate anion containing a defective structure site represented by 10), the composition formula of [Ag ₂ (Y ₂ Z ₁₈ O ₆₆ )] ^m- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo and m is 14 or 16) to contain the defect structure site containing the two Ag ⁺ cations. The above-mentioned preparation method comprising a step of obtaining a dimer of a telopolyoxometallate anion and a step of allowing a solution containing the dimer obtained in the steps (i) and (h) to stand at room temperature for a predetermined time.
[15]
An antibacterial and / or antiviral product comprising the composite metal nanocluster according to any one of [1] to [7] or the compound according to any one of [8] to [11].
[16]
The composite metal nanocluster according to any one of [1] to [7], or the compound, water, organic solvent or mixture thereof, and resin according to any one of [8] to [11]. Including paint composition.
[17]
The composite metal nanocluster according to any one of [1] to [7], or the compound, water, organic solvent or mixture thereof, and resin according to any one of [8] to [11]. Coating agent including.
Is to provide.

Metal clusters such as silver nanoclusters brought about by the composite metal nanoclusters of the present invention can exhibit extremely high stability not only in a solid state but also in a state of being dissolved in a solution.
In Ag27 (details will be described later), which is one of the composite metal nanoclusters of the present invention, the existing silver nanoclusters are immediately decomposed in the solution, but the silver nanoclusters contained in Ag27 have passed for more than one week. Even if it does not decompose, it shows very high stability. In addition, Ag27 exhibits visible light-responsive electrolytic transfer characteristics between silver nanoclusters and heteropolyoxometallates containing defective structure sites.
Further, it was found that in Ag7 (details will be described later), which is one of the composite metal nanoclusters of the present invention, silver atoms are exposed on the surface of the material. Silver atoms that are not protected by such ligands are important for catalytic reactions using exposed silver atoms as reaction active points, and for applications such as antibacterial and antiviral agents, but at the same time, they also decompose silver clusters. It may cause structural changes. However, it was confirmed from the ultraviolet-visible absorption spectrum of the silver nanoclusters contained in Ag7 that the structure of the silver nanoclusters did not change for more than one week and had very excellent stability.

X-ray crystal structure analysis data of Ag2, Ag6 and Ag27 The crystal structures of Ag2 and Ag6 are shown. The measurement result of the ESI-mass spectrum of Ag2 is shown. The measurement result of ²⁹ SiNMR of Ag2 is shown. The measurement result of the ESI-mass spectrum of the reaction solution of Ag2 in acetone and silver acetate (4 equivalents with respect to Ag2) is shown. The top view (a) and the side view (b) of the silver cluster {Ag ₂₇ } of Ag 27 are shown. The crystal filling of Ag27 is shown. The observed powder XRD pattern (upper pattern) of Ag27 and the simulated powder XRD pattern (lower pattern) are shown. The crystal structure of Ag27 is shown, a is the structure of the whole anion, and b is the structure of { _Ag27 } ¹⁷⁺ . The measurement result of ¹ HNMR spectrum of Ag27 is shown. The analysis result of the potentiometric titration of Ag27 (18.9 μmol / L) in acetonitrile using TBAOH (0.236M, methanol solution) as a titration agent is shown. The ESI-mass spectrum of Ag27 (a (overall view) and b (enlarged view)) and the ²⁹ SiNMR spectrum of Ag27 are shown. The measurement result of the UV-vis spectrum of Ag2 and Ag27 is shown. The UV-vis spectra of Ag27 (10 μM) in acetone (a), acetone (b), and acetonitrile (c) containing ethylene carbonate (1M) are shown. The results of measuring the UV-vis spectrum of Ag27 (10 μM) in acetonitrile are shown by (a) light irradiation (λ> 400 nm, 300 W Xe lamp) for 6 hours and (b) before and after heating at 60 ° C. for 6 hours. The ESI-mass spectrum of the synthetic solution of Ag27 is shown. The inset shows the spectrum in the range m / z 3530-3560 and the simulation pattern of [TBA ₈ H ₆ Ag ₆ (SiW ₉ O ₃₃ ) ₂ (DMF)] ²⁺ (m / z 3543.775). Schematic scheme of the production process from Ag2 to Ag27. The Ag K-end XANES spectra of Ag2 and Ag27 are shown. The XPS spectrum of Ag27 is shown. The molecular orbital of Ag27 is shown. Two types of possible visible light-induced charge transfer on Ag27 based on TD-DFT calculations are shown. The crystal filling of Ag7 is shown. Shows the X-ray crystal structure of Ag7 A schematic diagram of Ag7 nanocluster formation within a triangular hollow POM skeleton [Si ₃ W ₂₇ O ₉₆ ] ^18- ({Si ₃ W ₂₇ }) is shown. (A) shows a schematic diagram of the formation of a triangular POM skeleton [Si ₃ W ₂₇ O ₉₆ ] ^18- consisting of a C-type Dawson-type POM {Si ₂ W ₁₈ } and an additional {Si W ₉ } unit. b) shows the structure of a triangular hollow POM skeleton [Si ₃ W ₂₇ O ₉₆ ] ^18- . The negative ion ESI-mass spectrum of Ag7 in acetonitrile is shown. The inset shows the signals and simulations observed in the range of m / z 2135 to 2155 for [TBA ₅ H ₂ Ag ₇ (Si ₃ W ₂₇ O ₉₅ ) (MeCN)] ^4- (theoretically m / z 2144.482). Shows the pattern. (A) shows the UV-vis spectrum of Ag7 in acetonitrile (1 mM, 1 mm cell) before and after storage in the air and in solution. Further, (b) shows the theoretical UV-vis spectrum of Ag7 by time-dependent DFT calculation. The results of measuring the UV-vis spectrum (1 mm cell) of Ag7 (1 mM) in acetonitrile before and after light irradiation (λ> 400 nm, 300 W Xe lamp) in an atmospheric solution for 2 hours are shown. The space filling model of Ag7 is shown. The molecular orbital of Ag7 is shown. a) indicates HOMO, and b) indicates LUMO. The schematic diagram of the antiviral test method performed in Example 4 is shown. An example of calculating the anti-M13 phage activity value for the sample ⁽ Y6) having a dilution ratio of 105 is shown. The comparison of the decrease amount of M13 phage with respect to the addition amount of Ag27 in the anti-M13 phage activity evaluation is shown. A comparison of the anti-M13 phage activity of a commercially available silver compound and Ag27 under equal amount of substance conditions is shown.

As used herein, the term "nanocluster" refers to the bonding of several to dozens of atoms in a metal (eg, silver, etc.). The nanoclusters may have a diameter in the range of about 0.1 nm to about 3 nm.

1. 1. Composite Metal Nanoclusters One embodiment of the present invention comprises metal nanoclusters and
[YZ ₉ O ₃₄ ] In the composition formula of ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and n is 9 or 10). It contains a multimers of terror polyoxometallate anions and contains defective structural sites.
At least a part of the outer surface of the metal nanocluster is encapsulated inside the multimer.
The metal is a composite metal nanocluster selected from silver or platinum (hereinafter, also referred to as “composite metal nanocluster of the present invention”).

The composite metal nanocluster of the present invention comprises a metal nanocluster and a composition formula of [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As, and Z is from W or Mo. Selected, n is 9 or 10) and contains a multimer of heteropolyoxometallate anion (hereinafter also referred to as “POM”) containing a defective structure site.

As the multimer of POM, various multimers can be used as long as they have a structure in which metal nanoclusters partially or wholly enclosed inside the multimer are stabilized.

In one preferred embodiment of the invention, the POM multimer is constructed by condensing a POM dimer with one or more other POM dimers and / or one or more POMs. ..

In the composite metal nanoclusters of the present invention, the entire metal cluster is typically encapsulated inside the multimer, but only a portion of the outer surface of the metal cluster or the number of outer surfaces of the metal nanocluster. The portion may be encapsulated inside the multimer.
Further, in the composite metal nanocluster of the present invention, all or a part of all or a part of the metal atoms (as a non-limiting example, one or two metal atoms) of a part of the metal atom group constituting the metal cluster is the composite metal nano. It is also possible to take a structure that is exposed to the outside of the cluster.

In the composite metal nanocluster of the present invention, the metal nanocluster is preferably a silver nanocluster.

The metal nanocluster in the composite metal nanocluster of the present invention is an aggregate of silver atoms or platinum atoms. The metal nanocluster may contain any suitable number of silver or platinum atoms in the range of 1 to 100. In one preferred embodiment, the metal nanocluster comprises 2-100 atoms, 5-80 atoms, 5-70 atoms, 5-50 atoms.
Generally, the diameter of the metal nanocluster is from about 0.1 nm to about 3 nm, preferably less than about 2 nm.

In the composition formula of [YZ ₉ O ₃₄ ] ⁿ⁻ of POM, Y is preferably Si. Further, Z is preferably W.

In the composite metal nanocluster of the present invention, POM is preferably represented by [SiW ₉ O ₃₄ ] ^10- .
Further, in this case, the dimer of POM is represented by [Si ₂ W ₁₈ O ₆₆ ] ^16- .
Such a dimer of POM, [Si ₂ W ₁₈ O ₆₆ ] ^16- , is reactive and condenses with one or more other dimers and / or POM to be a multimer. Can be configured.
Further, the above-mentioned POM dimer preferably has a C-type open Dawson-type structure.

In a preferred aspect of the composite metal nanoclusters of the invention, the multimer is composed of three POM dimers.

In another preferred aspect of the composite metal nanoclusters of the invention, the POM multimer is composed of three POM dimers, the metal nanocluster is a silver nanocluster.

The above composite metal nanoclusters are selected from compounds containing anions represented by the formula: [Ag ₂₇ (Y ₂ Z ₁₈ O ₆₆ ) ₃ ] ^s- (where Y is P, Ge, Si or As). , Z is selected from W or Mo, and s is selected from an integer from 25 to 31).

Here, when Y is Si and Z is W, s is 31.
Further, when Y is Si and Z is Mo, s is 31.
Further, when Y is P and Z is W, s is 25.
Further, when Y is P and Z is Mo, s is 25.
Further, when Y is Ge and Z is W, s is 31.
Further, when Y is Ge and Z is Mo, s is 31.
Further, when Y is As and Z is W, s is 25.
Further, when Y is As and Z is Mo, s is 25.

Further, the above-mentioned composite metal nanocluster can also be represented as a compound having a composition of X _s [Ag ₂₇ ( _Y2 Z ₁₈ O ₆₆ ) ₃ ] (in the formula, X represents a counter cation).

Here, the counter cation may be the same or different, and quaternary ammonium (dimethylammonium, tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, tributylmethylbutylammonium, trioctylmethylammonium, tri) may be used. Laurylmethylammonium, benzyltrimethylammonium, benzyltriethylammonium, benzyltributylammonium, etc.), quaternary phosphonium (tetramethylphosphonium, tetraethylphosphonium, tetrapropylphosphonium, tetrabutylphosphonium, benzyltri Phenylphosphonium, etc.), protons, metal cations (eg, Ag ⁺ , Na ⁺ , K ⁺ , etc.) and the like.

The compound or salt thereof which is the composite metal nanocluster of the present invention is a hydrate and / or a solvate (for example, N, N-dimethylformamide, pyridine, N, N-dimethylacetamide, nitromethane, dichloromethane, 1, 2). -It may exist as dichloroethane, ethylene acetate, water), but these substances are also within the scope of the present invention.

In a more preferred aspect of the composite metal nanoclusters of the invention, the polymer is composed of three POM dimers, the dimer being represented by [Si ₂ W ₁₈ O ₆₆ ] ^16- , a metal. The cluster is a silver nanocluster.

Such composite metal nanoclusters can also be represented as compounds containing anions represented by the formula: [Ag ₂₇ (Si ₂ W ₁₈ O ₆₆ ) ₃ ] ^31- . Such anions are also referred to herein as "Ag27".
Ag27 is composed of three condensations of [Si ₂ W ₁₈ O ₆₆ ] ^16- , a POM dimer having a C-type open Dawson type.

The composite metal nanocluster can also be represented as a compound having the composition of X ₃₁ [Ag ₂₇ (Si ₂ W ₁₈ O ₆₆ ) ₃ ] (in the formula, X represents a counter cation).
The counter cation of X is as described above.

One preferred aspect of the compounds of the above composite metal nanoclusters is TBA ₁₆ (Me ₂ NH ₂ ) ₈ H ₅ Ag ₂ [Ag ₂₇ (Si ₂ W ₁₈ O ₆₆ ) ₃ ] · 12C ₃ H ₄ O _3.34H . ₂ O (C ₃ H ₄ O ₃ = ethylene carbonate).

As will be described in detail in Examples described later, the silver nanoclusters ({Ag ₂₇ } clusters) of Ag27 prepared in Examples are composed of five octahedral {Ag ₆ } clusters and three crosslinked Ag atoms. There is. At the center of the cluster, two octahedral {Ag ₆ } clusters form a face-shared di-octahedron {Ag ₉ } cluster, and nine Ag atoms are arranged in a hexagonal close-packed (hcp) fashion. Three octahedral {Ag ₆ } clusters exist around the central {Ag ₉ } cluster, and each octahedral cluster shares one corner Ag atom with the central {Ag ₉ } cluster. Three additional Ag atoms bridge these three octahedral {Ag ₆ } clusters to form a {Ag ₂₇ } cluster.
The {Ag ₂₇ } cluster is surrounded by a bulky anionic POM directly through the Ag-OW bond.

In another preferred aspect of the composite metal nanoclusters of the invention, the multimer of POM is composed of a dimer of one POM fused with one POM.

In another preferred aspect of the composite metal nanoclusters of the invention, the multimer is composed of a dimer of one POM fused with one POM, the metal cluster being a silver cluster.

The above composite metal nanoclusters are selected from compounds containing anions represented by the formula: [Ag ₇ (Y ₃ Z ₂₇ O ₉₆ )] ^t- (where Y is P, Ge, Si or As). Z is selected from W or Mo, and t is selected from an integer from 10 to 13).

Here, when Y is Si and Z is W, t is 13.
Further, when Y is Si and Z is Mo, t is 13.
Further, when Y is P and Z is W, t is 10.
Further, when Y is P and Z is Mo, t is 10.
Further, when Y is Ge and Z is W, t is 13.
Further, when Y is Ge and Z is Mo, t is 13.
Further, when Y is As and Z is W, t is 10.
Further, when Y is As and Z is Mo, t is 10.

The above-mentioned composite metal nanocluster can also be represented as a compound having a composition of the formula: _Xt [Ag ₇ (Y ₃ Z ₂₇ O ₉₆ )] (in the formula, X represents a counter cation).
The counter cation of X is as described above.

In another more preferred aspect of the composite metal nanoclusters of the invention, the multimer is a dimer of one POM; [Si ₂ W ₁₈ O ₆₆ ] ^16- and another POM; [SiW ₉ O]. ₃₄ ] It is composed of condensation with ^10- , and the metal nanocluster is a silver nanocluster.

Such composite metal nanoclusters can also be represented as compounds containing anions represented by the formula: [Ag ₇ (Si ₃ W ₂₇ O ₉₆ )] ^13- . Such anions are also referred to herein as "Ag7".

The composite metal nanocluster can also be represented as a compound having the composition of X ₁₃ [Ag ₇ (Si ₃ W ₂₇ O ₉₆ )] (in the formula, X represents a counter cation).
The counter cation of X is as described above.

Another preferred aspect of the compound of the composite metal nanoclusters described above is TBA ₉ H ₄ [Ag ₇ (Si ₃ W ₂₇ O ₉₆ )] · 12C ₃ H ₆ O (C ₃ H ₆ O = acetone).

As will be described in detail in Examples described later, the silver nanoclusters of Ag7 prepared in Examples are composed of two corner-shared tetrahedrons, _Ag4 nuclei (that is, one tetrahedron containing Ag1, Ag2, Ag3, and Ag4). Other tetrahedra containing Ag1 *, Ag2 *, Ag3 *, and Ag4 *), and the corner Ag2 atom is shared by two tetrahedra (see FIG. 23b). The _seven Ag atoms in the Ag7 nanocluster are arranged in an fcc structure.

2. 2. Method for Preparing Composite Metal Nanoclusters Another embodiment of the present invention is a composition formula of silver nanoclusters and [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As). , Z is selected from W or Mo and n is 9 or 10) and contains a multimer of three condensed heteropolyoxometallate anion dimer containing the defective structure site. A method for preparing a composite silver nanocluster, wherein at least a part of the outer surface of the silver nanocluster is encapsulated inside the multimer.
(A) A step of providing a mixture of AgL (where L represents a counter anion) and an organic solvent,
(B) In the mixture, the composition formula of [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, n is 9). Alternatively, by adding a compound containing a telopolyoxometallate anion containing a defective structure site represented by 10), the composition formula of [Ag ₂ (Y ₂ Z ₁₈ O ₆₆ )] ^m- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo and m is 14 or 16) to contain the defect structure site containing the two Ag ⁺ cations. In the above preparation method, which comprises a step of obtaining a dimer of telopolyoxometallate anion and (c) a step of adding a reducing agent and AgL (L represents a counter anion) to the solution containing the dimer. (Hereinafter, also referred to as "preparation method 1 of the present invention").

In the preparation method 1 of the present invention, first, a dimer of a heteropolyoxometallate anion containing a defect structure site containing two Ag ⁺ cations is obtained, and then a reducing agent is added to a solution containing the dimer. And AgL (L stands for counter anion) is important. By having such a step, it becomes possible to form a {Ag ₆ } cluster in a C-type Dawson-type POM such as a {Si ₂ W ₁₈ } unit, thereby obtaining a target composite silver nanocluster. Can be done.

As AgL (L represents a counter anion), it is necessary to be a silver salt that dissolves in an organic solvent, and silver acetate, silver benzoate and the like are preferable.

As the organic solvent, any solvent can be used as long as it dissolves the raw materials used such as POM and AgL, and for example, acetone, acetonitrile, N, N-dimethylformamide (DMF) and the like can be usually used.

The reducing agent is preferably N, N-dimethylformamide (DMF). A reducing agent such as DMF is preferable because it is effective in synthesizing Ag nanoclusters and serves as a mild reducing agent and an organic reaction medium.

Another embodiment of the present invention is a compositional formula of silver nanoclusters and [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is W or Mo. (N is 9 or 10), which contains a multimer in which three dimers of telopolyoxometallate anions are condensed and contains a defect structure site represented by 9 or 10. The outer surface of the silver nanocluster. At least a part of the above is a method for preparing composite silver nanoclusters encapsulated inside the multimer.
(D) A step of providing a mixture of AgL (where L represents a counter anion), an organic solvent and water.
(E) In the mixture, the composition formula of [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, n is 9). Or 10), a step of adding a compound containing a telopolyoxometallate anion to the defect structure site, and (f) after stirring for a predetermined time, a reducing agent and AgL (L is a counter anion). This is the above-mentioned preparation method including the step of adding (represented) (hereinafter, also referred to as “preparation method 2 of the present invention”).

In the preparation method 2 of the present invention, it is important to react AgL with POM and add a reducing agent and additional AgL after a lapse of a predetermined time. As a result, it is possible to control the formation of silver nanoclusters to be produced by reducing a part of the silver ions after the POM and the silver ions have sufficiently reacted.

The stirring time of the step (f) is several hours (for example, about 1 to 12 hours).

In the preparation methods 1 and 2 of the present invention, for example, when the POM is [SiW ₉ O ₃₄ ] ^10- , a hexamer is formed by condensing three C-type Dawson-type POMs {Si ₂ W ₁₈ }. POM skeleton can be formed.

Another embodiment of the present invention is a compositional formula of silver nanoclusters and [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is W or Mo. (N is 9 or 10), which contains a multimer of three condensed heteropolyoxometallate anions containing a defective structure site, and at least a part of the outer surface of the silver nanocluster. , A method for preparing composite silver nanoclusters encapsulated inside the multimer.
(G) A step of providing a mixture of AgL (where L represents a counter anion) and an organic solvent,
(H) In the mixture, the composition formula of [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, n is 9). Alternatively, by adding a compound containing a telopolyoxometallate anion containing a defective structure site represented by 10), the composition formula of [Ag ₂ (Y ₂ Z ₁₈ O ₆₆ )] ^m- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo and m is 14 or 16) to contain the defect structure site containing the two Ag ⁺ cations. The above-mentioned preparation method (hereinafter referred to as a preparation method) comprising a step of obtaining a dimer of a telopolyoxometallate anion and a step of allowing the solution containing the dimer obtained in the steps (i) and (h) to stand at room temperature for a predetermined time. Also referred to as "preparation method 3 of the present invention").

In the preparation method 3 of the present invention, it is important to allow the solution containing the dimer to stand at room temperature for a predetermined time after the step of obtaining a dimer of POM containing two Ag ⁺ cations. Thus, for example, when the POM is [SiW ₉ O ₃₄ ] ^10- , a triangular hollow POM skeleton [Si] consisting of a C-type Dawson-type POM {Si ₂ W ₁₈ } and an additional {SiW ₉ } unit. ₃ W ₂₇ O ₉₆ ] ^18- can be formed.
Here, the time for standing at room temperature is usually several days to several weeks.

3. 3. Applications of the composite metal nanoclusters of the present invention Since the composite metal nanoclusters of the present invention can provide highly stable silver nanoclusters, catalysts (fuel cell catalysts, automobile catalysts, chemical product manufacturing catalysts, etc.), It can be suitably used for photocatalyst and antibacterial / antiviral products.

Examples of antibacterial / antiviral products include paints and coating agents containing the composite metal nanoclusters of the present invention, and coating film products obtained from these.

That is, another aspect of the present invention is a coating composition containing the composite metal nanocluster of the present invention, water, an organic solvent or a mixture thereof, and a resin (hereinafter, also referred to as "the coating composition of the present invention"). ..

In addition, another aspect of the present invention is a coating agent containing the composite metal nanocluster of the present invention, water, an organic solvent or a mixture thereof, and a resin (hereinafter, also referred to as "coating agent of the present invention").

In the coating composition and coating agent of the present invention, the resin that can be used as a resin component and the resin formed from the resin component by coating or curing at the time of coating are not particularly limited, and are usually used in the coating industry. The resin used can be exemplified.
Specifically, acrylic resin, silicone resin, acrylic silicone resin, styrene acrylic copolymer resin, polyester resin, fluorine resin, rosin resin, petroleum resin, kumaron resin, phenol resin, urethane resin, melamine resin, urea resin, epoxy resin. , Cellulose resin, xylene resin, alkyd resin, aliphatic hydrocarbon resin, butyral resin, maleic acid resin, fumaric acid resin, vinyl resin (polyvinylidene chloride, etc.), amine resin, ketimine resin and the like. These resins may be used alone or in combination of two or more.

The organic solvent that can be used in the coating composition and the coating agent of the present invention is not particularly limited, and examples thereof include organic solvents that are usually used in coating materials. For example, alcohol (isopropyl alcohol, ethanol, butanol, etc.), ketone solvent (methyl ethyl ketone, acetone, etc.), ester (ethyl acetate, butyl acetate), toluene, xylene, amide solvent (dimethylacetamide, etc.), etc. should be used. Can be done.
Two or more kinds of organic solvents can be mixed and used, and a mixture of water and an organic solvent can also be used.

In the coating composition and coating agent of the present invention, two or more kinds of composite metal nanoclusters of the present invention may be used in combination.

The coating composition of the present invention can contain a pigment. Such pigments are not particularly limited, and pigments commonly used in the paint industry can be used. Specific examples include coloring pigments such as titanium dioxide, iron oxide and carbon black, extender pigments such as silica, talc, mica, calcium carbonate and barium sulfate, zinc, zinc phosphate, aluminum phosphate, zinc molybdate and metaboric acid. Examples thereof include rust preventive pigments such as barium and hydrocarbimite, and bright pigments such as aluminum, nickel, chromium, tin, copper, silver, platinum, gold, stainless steel and glass flakes.

The coating agent of the present invention may contain a pigment, or may be a coating agent that gives a transparent coating film containing no pigment.

The content of the composite metal nanoclusters in the coating composition of the present invention is, for example, 0.2 wt% to 3 wt%.
The content of the composite metal nanocluster in the coating agent of the present invention is, for example, 0.2 wt% to 3 wt%.

In the coating composition and coating agent of the present invention, the composite metal nanoclusters of the present invention can be used as they are, but the composite metal nanoclusters can also be used by being supported on metal or metal oxide particles. By supporting the composite metal nanoclusters on the particles of metal or metal oxide, the activity is further increased and high antiviral activity can be obtained.

Examples of the metal include Al, Ti, Si and the like, and examples of the metal oxide include silica (SiO ₂ ), titanium oxide, alumina and the like.
To support the metal or metal oxide particles, preferably the metal or metal oxide particles are impregnated into the solution or dispersion of the composite metal nanoclusters of the invention and then at a predetermined temperature (eg, eg). It can be obtained by drying at about 30 to 80 ° C.).
The amount of the composite metal nanocluster supported can be appropriately determined, and is, for example, 2 wt% to 20 wt%.

In the coating composition and coating agent of the present invention, pigment dispersants, thickeners, surface conditioners, film-forming aids, ultraviolet absorbers, antioxidants, flame retardants, antistatic agents, rust preventives, etc. It can contain various ingredients well known by those skilled in the art.

The coating means of the coating composition and the coating agent of the present invention is not particularly limited, and known coating means such as spray coating, roller coating, brush coating, iron coating, spatula coating and the like can be used.

The coating composition and coating agent of the present invention of the present invention can be used, for example, for painting or coating the walls of walls, toilets, and washbasins.
Further, the coating agent of the present invention can also be used as a protective agent for automobiles and the like.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Materials Acetone, N, N-dimethylformamide, dichloroethane, diethyl ether, ethyl acetate, tetrachloroethane, and ethylene carbonate were obtained from Kanto Chemical Co., Inc.
All solvents were stored in a suitable molecular sieve.
Silver acetate and silver benzoate were purchased from Sigma-Aldrich.
TBA ₄ [SiW ₉ O ₂₈ (OCH ₃ ) ₆ ] was synthesized according to the procedure reported in the following paper.
Minato, T .; Suzuki, K .; Kamata, K .; Mizuno, N. Synthesis of α-Dawson-type silicotungstate [α-Si2W18O62] 8-and protonation and deprotonation inside the aperture through intramolecular hydrogen bonds. Chem. Eur. J. 2014, 20, 5946-5952.
Minato, T .; Suzuki, K .; Yamaguchi, K .; Mizuno, N. Alkoxides of trivacant lacunary polyoxometalates. Chem. Eur. J. 2017, 23, 14213-14220.

The solution state UV-vis spectrum was measured with a JASCO V-570 spectrometer using a 1 cm quartz cell. Diffuse UV-vis spectra were measured with Shimadzu UV-3600plus.
The IR spectrum was measured with a JASCO FT / IR-4100 spectrometer using a KBr disk.
ESI-mass spectra were measured on a Waters Xevo G2-XS QTof device.
¹ H and ²⁹ Si NMR spectra were measured using a 5 mm tube with a JEOL JNM ECA-500 spectrometer. The chemical shift (δ) was measured using Si (CH ₃ ) ₄ as an internal standard.
ICP-AES analysis of Si, Ag and W was performed using Shimadzu ICPS-8100.
Elemental analysis of C, H, and N was performed on the Elemental vario MICRO cube of the Elemental Analysis Center, Faculty of Science, University of Tokyo.
Thermogravimetric analysis and differential thermal analysis (TG-DTA) were performed on the Rigaku Thermo Plus TG 8120.
The powder XRD pattern was measured with a Rigaku SmartLab diffractometer (CuKα, λ = 1.5405Å, 45kV, 200mA).
The XPS spectrum was measured by ULVAC-Phi PHI 5000 VersaProbe of the University of Tokyo microstructure nanotechnology platform.
The XANES spectrum was measured by the transmission method at the beamline BL 11S2 of the Aichi Synchrotron Optical Center.
Each sample was mixed with boron nitride to pelletize. The pellet was doubly wrapped in an Al-laminated pack and heat-sealed in an Ar-filled glove box. Ag foil was used for energy calibration.

X-ray crystal structure analysis Single crystal X-ray diffraction measurements were performed on a Rigaku MicroMax-007 Season 724 CCD detector with Mo Kα rays (λ = 0.71069 Å, 50 kV, 24 mA) monochromatic at 123K. Data were collected using Crystal Clear and processed using CrysAlisPro (Rigaku OD. CrysAlis PRO. Rigaku Oxford Diffraction Ltd, Yarnton, England (2018).).
In the data processing, Lorentz correction and polarization correction were performed. Structural analysis was performed using WinGX (Farrugia, LJ WinGX suite for small-molecule single-crystal crystallography. J. Appl. Crystallogr. 1999, 32, 837-838.).
All structures were analyzed by SHELXS-97 (direct method) and SHELXL-2018 / 3 ((a) Sheldrick, GM A short history of SHELX. Acta Cryst. 2008, A64, 112-122. (B) Sheldrick, GM. Crystal structure refinement with SHELXL. Acta Cryst. 2015, C71, 3-8.).
The metal atoms (Si, Ag, W) and oxygen atoms in the POM skeleton were anisotropically refined. The highly disordered TBA cations and solvent molecules are van der Sluis, P .; Spek, AL BYPASS: An effective method for the refinement of crystal structures containing disordered solvent regions. Acta Crystallogr. 1990, A46, 194. Was removed using. CCDC-1949945, CCDC-19449946 and CCDC-19499947 contain complementary crystallographic data of Ag2, Ag6 and Ag27, respectively.
These data are available free of charge from the CambridGe Crystalgraphic Data Center site (www.ccdc.cam.ac.uk/data_request/cif).

Valency Total (BVS) Calculation The BVS value was calculated by the following equation for the change in length _rij of a bond with a valency V between two atoms i and j in the observed crystal. In the equation, B is a constant equal to 0.37 Å and r ₀ ′ is the bond valence parameter for a given atomic pair (Brese, NE; O'Keeffe, M. Bond-valence parameters for solids. Acta Crystallogr. Sect. . 1991, B47, 1
92-197.)

Detailed calculation The geometry used for the calculation was obtained from the crystal structure determined in this study. Calculations were performed in acetone and solvent effects were included using a polarization continuum model (PCM). Since the size of the target molecule is large, a medium-sized basis set system (6-31G * for O and Si, LANL2DZ ECP for W and Ag) was used. All calculations were done with Gauss 16.

[Synthesis Example 1]
TBA ₇ H ₂ [Ag ₂ (SiW ₉ O ₃₁ ) ₂ (CH ₃ COO) ₃ ] ・ H ₂ O ・ CCl ₄ (
Ag2) synthesis and characterization
TBA ₄ [SiW ₉ O ₂₈ (OCH ₃ ) ₆ ] (101 mg, 30.8 μmol) was added to a mixture of acetone (2 mL) and silver acetate (5.3 mg, 30.8 μmol). The resulting solution was stirred at room temperature for 5 hours. From the mixture of synthetic solution and carbon tetrachloride, colorless single crystals of Ag2 suitable for X-ray crystallography were obtained (52.6 mg, yield 48%).

IR (KBr pellets): 3447, 2961, 2935, 2874, 1637, 1484, 1381, 1153, 1108, 1054, 999, 953, 906, 768, 667, 557, 457 cm ^-1 .
²⁹ SiNMR (99.37MHz, acetone-d6 solution, containing 1M ethylene carbonate, 298K) δ = -83.6ppm
UV-vis (acetone solution containing 1 M ethylene carbonate): λ (ε) 350 nm (3.92 × 10 ³ M ^-1 cm ^-1 )
ESI-mass spectrum (positive mode, acetone): m / z 3437.074 [TBA ₉ HAg ₂ (SiW ₉ O ₃₁ ) ₂ (CH ₃ COO) ₂ ] ²⁺ (calculated value 3437.085), 3467.094 [TBA ₉ H ₂ Ag ₂ (calculated value 3437.085) SiW ₉ O ₃₁ ) ₂ (CH ₃ COO) ₃ ] ²⁺ (calculated value 3467.096).
Elemental analysis: TBA ₇ H ₂ [Ag ₂ (SiW ₉ O ₃₁ ) ₂ (CH ₃ COO) ₃ ] H ₂ O · CCl ₄ ; Calculated value (%): C 21.59, H 4.03, N 1. 48, Si 0.85, Ag 3.26, W 49.98
Measured values: C 21.30, H 4.07, N 1.50, Si 0.80, Ag 3.19, W 49.98

[Example 1]
Structural analysis of Ag2
The X-ray crystal structure analysis of Ag2 obtained in Synthesis Example 1 was performed. The results are shown in FIG. 1 (see X-ray crystal structure analysis data of Ag2) and Table 1 below (BVS values of silicon and tungsten atoms of Ag2). Further, from the results of X-ray crystal structure analysis, as shown in FIG. 2a, a C-type Dawson-type dimer ({Si ₂ W ₁₈ }) containing two Ag ⁺ cations is formed in Ag2. It became clear. In FIG. 2, the large sphere represents Ag, the sphere connected to silver represents O, the gray sphere represents C, and the smallest sphere represents H.
These Ag ⁺ cations were bridged by acetate ligands, and the two acetate ligands were coordinated to the empty lattice points of the {Si ₂ W ₁₈ } unit. The ESI-mass spectrum and ²⁹ SiNMR measurements showed that Ag2 was stable in solution (FIGS. 3 and 4). It should be noted here that Ag2 still has large pore sites, which can be used to accommodate and cluster additional Ag atoms.

[Reference Example 1]
Next, an attempt was made to synthesize a larger Ag nanocluster using a silver-containing C-type {Si ₂ W ₁₈ } construction unit. However, ESI-mass spectrometry revealed that additional Ag atoms could not be introduced into the empty lattice point simply by reacting Ag2 with Ag ⁺ cations in acetone (Fig. 5). On the other hand, when a reducing agent such as boron hydride or silane was added to the reaction solution, the colorless solution immediately turned dark brown, indicating the reduction of Ag ⁺ to Ag ⁰ and the formation of Ag nanoclusters. It is highly probable that our attempts to obtain discrete Ag nanoclusters were unsuccessful because the reduction of Ag ⁺ proceeded too fast to control the growth of the nanoclusters.

Therefore, we considered that N, N-dimethylformamide (DMF) is effective for the synthesis of Ag nanoclusters and may play a role as a mild reducing agent and an organic reaction medium, and investigated the use of DMF as a reducing agent. rice field.

[Synthesis Example 2]
TBA ₁₆ (Me ₂ NH ₂ ) ₈ H ₅ Ag ₂ [Ag ₂₇ (Si ₂ W ₁₈ O ₆₆ ) ₃ ] ・ 12
Synthesis and characterization of C ₃ H ₄ O 3.34 H ₂ O ₍ Ag27 )
To Ag2 (15.4 μmol / L) in a mixture of acetone (2 mL) and water (10 μL), N, N-dimethylformamide (1 mL) and silver benzoate (134 mg, 624 μmol) were added. The resulting solution was stirred for 48 hours. During the reaction, the colorless solution gradually turned dark brown. Diethyl ether (30 mL) was added to give a dark brown precipitate of Ag27. Ag27 could also be synthesized by the following procedure.
To silver benzoate (35.5 mg, 154 μmol) in a mixture of acetone (10 mL) and water (50 μL), TBA ₄ [SiW ₉ O ₂₈ (OCH ₃ ) ₆ ] (506 mg, 154 μmol) was added. After stirring the obtained solution for 3 hours, N, N-dimethylformamide (5 mL) and silver benzoate (134 mg, 624 μmol) were added. Then, the next solution was stirred at room temperature for another 48 hours. Diethyl ether (300 mL) was added to give a dark brown precipitate of Ag27. The precipitate was collected by filtration and then recrystallized from an acetone solution containing ethylene carbonate (2.9 M) and ethyl acetate to obtain crystals of Ag27 (236 mg, yield 40%). A single crystal suitable for X-ray crystallography was obtained by further recrystallization from an acetone solution containing ethylene carbonate (1M) and diethyl ether.
IR (KBr pellets): 3448, 2960, 2937, 2874, 1800, 1773, 1629, 1486, 1466, 1384, 1153, 1072, 993, 931 (sh), 871,737,664,553,520 (sh) cm ^-1
29 SiNMR (99.37MHz, 1M ethylene carbonate-containing acetone-d6 solution, 298K, Si (CH ₃ ) ₄ ) δ = -79.2 ppm
UV-vis (acetone solution containing 1 M ethylene carbonate): λ (ε) 600 nm (9.05 × 10 ³ M ^-1 cm ^-1 ), 530 nm (7.09 × 10 ³ M ^-1 cm ^-1 ), 435 nm (6.65) × 10 ⁴ M ^-1 cm ^-1 ), 530 nm (7.09 × 10 ³ M ^-1 cm ^-1 ), 350 nm (7.60 × 10 ⁴ M ^-1 cm ^-1 )
ESI-mass (positive mode, acetone): [TBA ₁₆ (Me ₂ NH ₂ ) ₆ H ₁₁ Ag ₂₉ (Si ₂ W ₁₈ O ₆₆ ) ₃ (C ₃ H ₄ O ₃ ) ₃ ] m / that can be assigned to ⁴⁺ z 5205.968 (theory m / z: 5205.888)
Elemental analysis: TBA ₁₆ (Me ₂ NH ₂ ) ₈ H ₅ Ag ₂ [Ag ₂₇ (Si ₂ W ₁₈ O ₆₆ ) ₃ ] · 12C ₃ H ₄ O _{3.34H 2} O; Calculated value (%): C 16. 58, H 3.44, N 1.51, Si 0.76, Ag 14.02, W 44.49
Measured values: C 16.35, H 3.19, N 1.51, Si 0.74, Ag 13.90, W 44.66

[Example 2]
Structural analysis of Ag27
(1) X-ray crystal structure analysis When the X-ray crystal structure analysis of Ag27 obtained in Synthesis Example 2 was performed, the Ag27 was housed in three {Si ₂ W ₁₈ } units by X-ray crystal analysis. The formation of trefoil-propeller {Ag ₂₇ } nanoclusters was revealed. (Figs. 1 and 6-9).
Here, FIG. 1 shows the X-ray crystal structure analysis data of Ag27. Further, FIG. 6 shows a top view (a) and a side view (b) of the silver cluster {Ag ₂₇ } of Ag 27, and FIG. 7 shows the crystal filling of Ag 27. FIG. 8 shows the observed powder XRD pattern of Ag27 and the simulated powder XRD pattern. FIG. 9 shows the crystal structure of Ag27, where a is the structure of the entire anion and b is the structure of {Ag ₂₇ } ¹⁷⁺ .

From FIG. 9, it was clarified that the {Ag ₂₇ } cluster was composed of 5 octahedral {Ag ₆ } clusters and 3 crosslinked Ag atoms. At the center of the cluster, two octahedrons {Ag ₆ } clusters form a face-shared octahedron {Ag ₉ } cluster (octahedron in the center of FIG. 9b), and nine Ag atoms are hexagonally close-packed (hcp). ) It was arranged in a style. Similar hcp {Au ₉ } clusters in {Au ₁₈ } clusters have been reported, but hcp {Ag ₉ } clusters were unprecedented. Three octahedral {Ag ₆ } clusters existed around the central {Ag ₉ } cluster, and each octahedral cluster shared an Ag atom at one corner with the central {Ag ₉ } cluster. Three additional Ag atoms (black spheres) bridged these three octahedral {Ag ₆ } clusters to form {Ag ₂₇ } clusters.
The {Ag ₂₇ } cluster was surrounded by a bulky anionic POM directly through the Ag-OW bond. In the {Ag ₂₇ } cluster, the Ag-Ag separation was in the range 2.71-3.02 Å, indicating a silver-affinity interaction (Table 2). Here, Table 2 shows the distance (Å) between the silver atoms of Ag27.

In addition to the {Ag ₂₇ } cluster, two Ag ⁺ cations (Ag31 and Ag32; valency sum (BVS) values were 1.02 and 0.97, respectively) were observed above and below the cluster. The BVS values of the Si (3.89-3.95) and W (5.92-6.41) atoms were +4 and +6 (Table 3), respectively. Here, Table 3 shows the BVS values of the silicon atom and the tungsten atom of Ag27.

In particular, X-ray crystallography revealed the presence of eight dimethylammonium cations ([Me ₂ NH ₂ ] ⁺ ). In addition, the ¹ HNMR spectrum of Ag27 in Acetone-d ₆ signaled at δ = 3.2 ppm, corresponding to 8 [Me ₂ NH ₂ ] ⁺ cations for the cluster (FIG. 10). These results show that [Me ₂ NH ₂ ] ⁺ cations are most likely derived from the oxidation of DMF to N, N-dimethylcarbamic acid and subsequent degradation, so DMF is Ag ⁺ in synthetic solution. It strongly suggests that it acts as a reducing agent.
In the crystal structure, 6 TBA cations for the cluster were found. Acid-base titration of Ag27 using TBAOH as the titrator showed the presence of 5 protons per Ag27 (FIG. 11).
FIG. 11 shows the analysis result of potentiometric titration of Ag27 (18.9 μmol / L) in acetonitrile using TBAOH (0.236M, methanol solution) as a titrator. The potential is for a standard Ag / AgCl electrode.

Based on these data, elemental analysis, ¹ HNMR spectrum and TG-DTA, Ag27 is formulated: TBA ₁₆ (Me ₂ NH ₂ ) ₈ H ₅ Ag ₂ [Ag ₂₇ (Si ₂ W ₁₈ O ₆₆ ) ₃ ]. It can be represented by 12C _{3H 4 O 3.34H 2 O (C 3 H 4 O 3 = ethylene carbonate )} . From the sum of the positive charges of the counter cations (ie, TBA ⁺ , [Me ₂ NH ₂ ] ⁺ , H ⁺ , and Ag ⁺ ), the negative charge of the [Ag ₂₇ (Si ₂ W ₁₈ O ₆₆ ) ₃ ] anion is -31. Calculated. Considering the charge of C-type Dawson POM [Si ₂ W ₁₈ O ₆₆ ] ^16- , the charge of {Ag ₂₇ } was +17, and the {Ag ₂₇ } ^{17 +} cluster contained 10 valence electrons.

(2) ESI-mass
The ESI-mass of Ag27 in acetone can be assigned to [TBA ₁₆ (Me ₂ NH ₂ ) ₆ H ₁₁ Ag ₂₉ (Si ₂ W ₁₈ O ₆₆ ) ₃ (C ₃ H ₄ O ₃ ) ₃ ] ⁴⁺ . A set of signals of m / z 5205.968 is shown (a and b in FIGS. 12).
All other ESI-mass signals are [TBA _m (Me ₂ NH ₂ ) _22-m H ₁₁ Ag ₂₉ (Si ₂ W ₁₈ O ₆₆ ) ₃ (C ₃ H ₄ O ₃ ) _n ] ⁴⁺ (m = 14-20) , N = 1-4). The ²⁹ SiNMR spectrum of Ag27 revealed a single peak at -79.2 ppm (c in FIG. 12). ²⁹ SiNMR spectra were measured for Ag27 in acetone-d6 containing ethylene carbonate (1M).
The results of these ESI-mass and ²⁹ SiNMR spectra showed that Ag27 was stable in solution.

(3) UV-vis spectrum The UV-vis spectrum of Ag27 showed a remarkable absorption band at 435,500 (shoulder) and 600 nm, while the spectrum of Ag2 showed an absorption band in the visible light region (λ> 400 nm, FIG. 13). Did not show. In particular, Ag27 had unprecedented hyperstability, and the UV-vis spectrum of Ag27 changed little after one week under air atmosphere in solution (FIG. 14). Furthermore, Ag27 also showed stability when irradiated with light (λ> 400 nm) or heated at 60 ° C. (FIG. 15).
Here, FIG. 13 shows UV-vis absorption spectra of Ag2 (30 / sec) and Ag27 (10 / sec) in acetone containing ethylene carbonate (1M).
FIG. 14 shows UV-vis spectra of Ag27 (10 μM) in acetone (a), acetone (b), and acetonitrile (c) containing ethylene carbonate (1M).
FIG. 15 shows UV-vis spectra of Ag27 (10 μM) in acetonitrile measured before and after (a) light irradiation (λ> 400 nm, 300 W Xe lamp) for 6 hours and (b) heating at 60 ° C. for 6 hours. The results are shown.
The stability of this Ag is noteworthy, as even the stable Ag nanoclusters reported so far partially decompose in solution after a few days.

Next, the formation structure of Ag27 was investigated. The ESI-mass of the synthetic solution of Ag27 indicates the main set of signals of m / z 3543.701 that can be assigned to [TBA ₈ H ₆ Ag ₆ (SiW ₉ O ₃₃ ) ₂ (DMF)] ²⁺ , {Ag ₆ } It was shown that the cluster was formed in the {Si ₂ W ₁₈ } unit (Fig. 16). X-ray crystallography revealed that octahedral {Ag ₆ } clusters were formed in the C-type Dawson-type POM (Ag 6; FIGS. 1, 4 and 5).
Here, Table 4 shows the BVS values of the silicon atom and the tungsten atom of Ag6. Table 5 shows the distance (Å) between silver atoms of Ag6.

One Ag atom (Ag4) in the { _Ag6 } cluster had relatively small steric hindrance, while the other atom (Ag1-Ag3) was protected by bulky POM. Similar octahedral {Ag ₆ } clusters (FIG. 2) within the {Si ₂ W ₁₈ } unit were found as a partial structure of Ag 27. These results indicate that {Ag ₆ } clusters are first formed within a C-shaped Dawson type {Si ₂ W ₁₈ } unit, followed by a large Ag 27 formed by the assembly of Ag 6 and additional Ag atoms. There is.
Therefore, it was revealed that the formation process from Ag2 to Ag27 proceeded according to the schematic scheme shown in FIG. In FIG. 17, the structure of I shows Ag2, the structure of II shows Ag6, and the structure of III shows Ag27.

(4) Study of electronic state of {Ag ₂₇ } cluster Further study on electronic state of {Ag ₂₇ } cluster, X-ray absorption near edge structure (XANES) spectrum, X-ray photoelectron spectrum (XPS), and density functional theory (DFT) Performed by calculation. The AgK-end XANES spectrum of Ag27 peaks at 25526 eV, which is observed between Ag ⁺ of Ag foil (25528 eV) and Ag2 (25524 eV) (FIG. 18), where Ag27 consists of both Ag ⁺ and Ag ⁰ . I showed that. The XPS spectra of Ag27 in the Ag3d region show two peaks of 374.28 and 368.28 eV, which can be assigned to Ag3d _3/2 and Ag3d _5/2 , respectively (FIG. 19). Here, FIG. 18 shows the Ag K-end XANES spectra of Ag2 and Ag27, and FIG. 19 shows the XPS spectra of Ag27.
These peaks are 374.56 eV (3d _3/2 , Ag ⁰ ), 374.15 eV (3d _3/2 , Ag ⁺ ), 368.56 eV (3d _5/2 , Ag ⁰ ), 368.18 eV (3d ₅ ). _{/ 2} , Ag ⁺ ) was able to be deconvoluted. The area ratios of Ag ⁺ / Ag ⁰ for Ag3d _3/2 and Ag3d _5/2 were 2.15 and 1.91, respectively, supporting Ag27 containing about 10 valence electrons. From the DC magnetic susceptibility measurement, it was found that Ag27 is diamagnetic and its ground state is a singlet (closed shell structure).

The DFT calculation of the anion moiety of Ag27 was performed using the CAM-B3 LYP functional.
When the Ag nanocluster consists of 10 valence electrons (ie {Ag ₂₇ } ¹⁷⁺ ), the orbital energy of the lowest empty molecular orbital (LUMO) was a positive value (0.54 eV), but 8 valences. The electron (that is, {Ag ₂₇ } ¹⁹⁺ ) became negative (-1.95 eV). Since the long-range corrected functional-based calculations approximately satisfy Koopmans' theorem, these results show that the electronic states of the Ag nanoclusters are most consistent with {Ag ₂₇ } ¹⁷⁺ , which is consistent with the experimental results. ing.
The highest occupied molecular orbitals (HOMO) and HOMO-1 were delocalized on {Ag ₂₇ } ¹⁷⁺ clusters (Fig. 20), and the valence electrons behaved like free electrons. The bulky POM covers the valence electrons, which is considered to be the reason why Ag27 exhibits unprecedented stability. HOMO showed superatom p-orbital-like symmetry, and HOMO-1 showed dz2 orbital-like symmetry. On the other hand, LUMO is mainly derived from the Wd orbit of the {Si ₂ W ₁₈ } unit. Time-dependent DFT calculations revealed that the absorption band in the longest wavelength region (λ = -600 nm) is due to charge transfer within {Ag ₂₇ } ¹⁷⁺ (FIG. 21). The next absorption band (λ = -530 nm) is mainly {Ag ₂₇ } ¹⁷⁺ and WD-based LUMO from orbitals based on O atoms (ie, HOMO-3, HOMO-2, HOMO-1, HOMO). Was due to charge transfer to LUMO + 1.
Here, FIG. 21 shows two types of possible visible light-induced charge transfer on Ag27 based on TD-DFT calculations. (A) shows {Ag ₂₇ } ^{17 +} nanocluster core of POM ligand charge transfer, and (b) shows internal {Ag ₂₇ } ^{17 +} core charge transfer.

[Synthesis Example 3]
Synthesis of TBA ₉ H ₄ [Ag ₇ (Si ₃ W ₂₇ O ₉₆ )] and 12C ₃ H ₆ O (Ag 7)
Characterization
TBA 4H ₆ [ _{SiW 9 O 34} ] and 2H ₂ O (100 mg, 30.8 μmol) were added to silver acetate (10.0 mg, 59.9 μmol) in acetone (2 mL). The resulting solution was stirred at room temperature for 5 hours. Colorless needle-like crystals of Ag2 were obtained from a mixture of synthetic solution and ethyl acetate. After storing this solution at room temperature for another 2 weeks, red block crystals of Ag7 suitable for X-ray crystallography were obtained (5 mg).

IR (KBr pellets): 3447, 2961, 2935, 2874, 1636, 1485, 1382, 1152, 1107, 1061, 1004, 958, 882, 784, 688, 553cm ^-1
Elemental analysis: TBA ₉ H ₄ [Ag ₇ (Si ₃ W ₂₇ O ₉₆ )] ・ 12C ₃ H ₆ O
Calculated value (%): Si 0.82, Ag 7.39, W 48.55
Measured values: Si 0.82, Ag 7.38, W 48.59
UV-vis (acetonitrile): λ (ε) 400 nm (2.1 × 10 ³ M ^-1 cm ^-1 ), 350 nm (sh, 5.4 × 10 ³ M ^-1 cm ^-1 ), 315 nm (9.7 × 10 ³ ) M ^-1 cm ^-1 )
Negative ion ESI-mass (acetonitrile): m / z = 2144.478 [TBA ₅ H ₂ Ag ₇ (Si ₃ W ₂₇ O ₉₅ ) (CH ₃ CN)] ^4- (Theory m / z = 2144.482) and m / z = 2940.071 [TBA ₆ H ₂ Ag ₇ (Si ₃ W ₂₇ O ₉₅ ) (CH ₃ CN)] ^3- (Theory m / z = 2940.072)
Cation ESI-mass (acetonitrile): m / z = 3424.974 [TBA ₁₂ H ₂ Ag ₇ (Si ₃ W ₂₇ O ₉₅ ) (CH ₃ CN)] ³⁺ (theoretical m / z = 3424.976)

[Example 3]
Structural analysis of Ag7
Various structural analyzes of Ag7 obtained in Synthesis Example 3 were performed.
(1) X-ray crystal structure analysis By X-ray crystal structure analysis of Ag7 of red crystals, Ag7 is found in an unprecedented triangular hollow POM skeleton [Si ₃ W ₂₇ O ₉₆ ] ^18- ({Si ₃ W ₂₇ }). It was found to contain ₇ nanoclusters (Table 6, FIGS. 22 and 23).
Table 6 shows the data of X-ray crystal structure analysis of Ag7. Further, FIG. 22 (a) shows crystal filling from the a-axis of Ag7, and FIG. 22 (b) shows crystal filling from the b-axis of Ag7.
FIG. 23 shows the X-ray crystal structure of Ag7. 23 (a) shows the structure of the total anion moiety, (b) shows the structure of the _Ag7 core of Ag7, and (c) shows the arrangement of Ag atoms in the bulky fccAg crystal. The black and gray spheres in the figure indicate Ag, and the small spheres indicate O.

Further, FIG. 24 shows a schematic diagram of Ag7 nanocluster formation in a triangular hollow POM skeleton [Si ₃ W ₂₇ O ₉₆ ] ^18- ({Si ₃ W ₂₇ }).
The ^Ag7 triangle [Si ₃ W ₂₇ O ₉₆ ] 18- shown in FIG. 24 is a C-type Dewson type {Si ₂ W ₁₈ } unit (Si 1, W1-W 9) and an additional {Si W ₉ } unit (Si 2, W 9). W10-W18) is included, and [Si ₃ W ₂₇ O ₉₆ ] ^18- is most likely formed by dehydration condensation of C-type POM (ie, Ag2) and tri-defective POM [SiW ₉ O ₃₄ ] ^10- . It was shown that (see FIG. 25).
Here, (a) of FIG. 25 shows the formation of a triangular POM skeleton [Si ₃ W ₂₇ O ₉₆ ] ^18- consisting of a C-type Dawson-type POM {Si ₂ W ₁₈ } and an additional {Si W ₉ } unit. A schematic diagram is shown, in which (b) shows the structure of a triangular hollow POM skeleton [Si ₃ W ₂₇ O ₉₆ ] ^18- .
So far, several cyclic and oligomeric structures of defective POMs have been reported, but the [Si ₃ W ₂₇ O ₉₆ ] ¹⁸ -triangular hollow POM skeleton is novel. The dehydration condensation of the trivalent-deficient POM appeared to be accelerated in an organic solvent to give rise to a new triangular hollow POM skeleton.
We have previously reported that trivalent-deficient POMs are readily dimerized into Dawson-type POMs [Si ₂ W ₁₈ O ₆₂ ] ^8- without pitted sites in the absence of Ag ⁺ cations. Therefore, Ag ⁺ cations and / or Ag _n nanoclusters encapsulated in C-type POMs served as templates for the formation of triangular hollow POM skeletons. The triangular hollow POM skeleton [Si ₃ W ₂₇ O ₉₆ ] ¹⁸ -contains several reactive oxygen atoms (shown as small spheres in Figure 23a), which are stable in unique _Ag7 nanoclusters. Worked as a cluster. The sum of the valencies of the Si and W atoms suggests that their valences are +4 and +6, respectively.

_Ag7 nanoclusters are two corner-shared tetrahedrons, one tetrahedron containing _Ag4 nuclei (ie, Ag1, Ag2, Ag3, and Ag4) and another tetrahedron containing Ag1 *, Ag2 *, Ag3 *, and Ag4 *. The corner Ag2 atom is shared by two tetrahedrons (FIG. 23b). The _seven Ag atoms in the Ag7 nanocluster are arranged in an fcc structure. To the best of our knowledge, the X-ray crystal structure of _Ag7 nanoclusters has not yet been studied, although the _Ag7 sequence can be observed in bulk fcc Ag crystals (FIG. 23c). The formation of this unique _Ag7 sequence was hypothesized to be due to a structurally defined hollow POM skeleton. The Ag ... Ag separation distance is 2.69 to 2.94 Å as shown in Table 7 below (separation distance between silver atoms of Ag7 (Å)), indicating the presence of silver-affinity interaction. There is. These separation distances are similar to those of the above-mentioned Ag27 ({ _Ag27 } ¹⁷⁺ , 2.71-3.02Å) and known Ag nanoclusters.

(2) ESI-mass
The negative ion ESI-mass of Ag7 in acetonitrile showed a series of signals at m / z 2144.478 and 2940.071. These series of signals are [TBA ₅ H ₂ Ag ₇ (Si ₃ W ₂₇ O ₉₅ ) (MeCN)] ^4- (theoretically m / z 2144.482) and [TBA ₆ H ₂ Ag ₇ (TBA 6 H 2 Ag 7), respectively. It can be attributed to Si ₃ W ₂₇ O ₉₅ ) (MeCN)] ^3- ] (theoretically, m / z 2940.072) (FIG. 26). Therefore, the structure of _Ag7 nanoclusters was retained in acetonitrile. In addition, the results of the positive ion ESI-mass spectrum of Ag7 are presented with a set of signals that can be attributed to [TBA ₁₂ H ₂ Ag ₇ (Si ₃ W ₂₇ O ₉₅ ) (MeCN)] ³⁺ at m / z 3424.974. Supported the structure.

Based on the observed valence of the ESI-mass signal and the total charge of the counter cation, it was suggested that the total negative charge of the [Ag ₇ (Si ₃ W ₂₇ O ₉₆ )] moiety was -13. Considering the negative charge of the POM skeleton [Si ₃ W ₂₇ O ₉₆ ] ^18- , the charge of the Ag ₇ nanocluster seems to be +5, indicating that the {Ag ₇ } 5 ^{+ nanocluster} contains two valence electrons. There is.
It is considered that a small amount of water in the reaction solution acts as a reducing agent for Ag ⁺ .

(3) UV-vis spectrum FIG. 27 (a) shows the UV-vis spectrum of Ag7 in acetonitrile (1 mM, 1 mm cell) before and after storage in air and in solution. Further, FIG. 27 (b) shows the theoretical UV-vis spectrum of Ag7 by time-dependent DFT calculation (curve graph). A Gaussian function with a full width at half maximum (FWHM) of 0.40 eV was used for the simulation. Black bars indicate the calculated transitions.
The UV-vis spectrum of Ag7 in acetonitrile showed a remarkable absorption band in the visible light region (λ _max = about 420 nm), but was not observed in Ag2 or silver acetate (FIG. 27a). Surprisingly, the UV-vis spectrum of Ag7 showed no significant change even after storage in acetonitrile in air atmosphere for one week (FIG. 27a). Furthermore, the UV-vis spectrum of Ag7 was almost unchanged by irradiation with visible light (λ> 400 nm) for 2 hours (FIG. 28).
Here, FIG. 28 shows the results of measuring the UV-vis spectrum (1 mm cell) of Ag7 (1 mM) in acetonitrile before and after light irradiation (λ> 400 nm, 300 W Xe lamp) in an atmospheric solution for 2 hours. be.

Thus, the structure and electronic states of Ag7 are in acetonitrile, even though the small _Ag7 nanoclusters are ultrastable and expose the Ag sites accessible to small molecules such as _O2 , water, and solvents. It was maintained (see FIG. 29 showing a space-filling model of Ag7). This is very important because small Ag nanoclusters are generally very unstable and even stable large Ag nanoclusters are observed to partially decompose in solution after a few days.

(4) Study of electronic state of Ag7 The electronic state of Ag7 was further investigated by DFT calculation using the CAM-B3LYP functional. The anion structure of Ag7 is optimized by a large molecular size (BS1) using a medium-sized basis set system (6-13G * for O and Si, LANL2DZ ECP for W and Ag; ECP = effective core potential). did. Subsequently, a single point calculation based on an optimized structure using a basis set of 6 to 31 + G * for O, 6 to 31 G * for Si, and LanL08 (f) ECP for W and Ag. Total energy was calculated by (BS2). The solvent effect was evaluated using the C-PCM solvent model. Based on the reaction energy (ΔE) of the redox reaction of {Ag ₇ } ^{m +} nanocluster [formula (1)] and various reducing agents, the E'value (similar to the redox potential) is calculated using the formula (2). Obtained (Table 8). Here, F is a Faraday constant.

E'value of reduction from {Ag ₇ } ⁷⁺ to {Ag ₇ } ⁵⁺ (that is, [{Ag ₇ } ⁷⁺ (Si ₃ W ₂₇ O ₉₆ )] ¹¹⁻ + 2e ^― → [{Ag ₇ } ⁵⁺ (Si ₃ ) W ₂₇ O ₉₆ )] ^13- ) is 4.89 eV, and the E'value of the halogen reaction (for example, I _3- + ^2e- → ^{3I- vs.} E'= 4.84 eV; I ₂ + ^2e- → It was similar to E'= ^5.08eV for 2I-; Br ₂ + ^2e- → E'= ^5.30eV for 2Br-). In contrast, the E'value of the reduction from {Ag ₇ } ⁵⁺ to {Ag ₇ } ³⁺ (ie, [{Ag ₇ } ⁵⁺ (Si ₃ W ₂₇ O ₉₆ )] ^13- + ^2e- → [{Ag ₇ }] ³⁺ (Si ₃ W ₂₇ O ₉₆ )] In the case of ^15- , E'= 1.42eV) is the E'value of the alkaline cation (for example, in the case of Na ⁺ + e- → E'= ^1.33eV in the case of Na; K ⁺ + e ^- → In the case of K, it is similar to E'= 1.22V), and {Ag ₇ } ⁵⁺ in the triangular POM is reduced to {Ag ₇ } ³⁺ unless a strong reducing agent such as Na or K is used. It shows that it cannot be done.
Therefore, the electronic state of Ag7 is likely to be { _Ag7 } ⁵⁺ with two valence electrons, which is in good agreement with the experimental data. Based on these data, elemental analysis, ESI-mass and X-ray crystallography, the formula for Ag7 was TBA ₉ H ₄ [Ag ₇ (Si ₃ W ₂₇ O ₉₆ )] · 12C ₃ H ₆ O (C ₃ H ₆ ). O = acetone).

DFT calculations show that the highest occupied molecular orbital (HOMO) is delocalized on {Ag ₇ } ⁵⁺ nanoclusters and the divalent electrons behave like free electrons (Fig. 30a). HOMO had s-orbital-like symmetry and exhibited properties related to superatomic Ag nanoclusters. In contrast, when calculated in the electronic state of {Ag ₇ } ³⁺ , HOMO moved to the Wd orbit of the POM skeleton and Ag ₇ nanoclusters. Considering that the valence electron charge transfer band attributed to W ⁵⁺ / W ⁶⁺ is not experimentally observed in the UV-vis spectrum of Ag7 (FIG. 28) in the range of 600 to 800 nm, { _Ag7 } ³⁺ electrons. The condition is unlikely to be obtained. The lowest empty molecular orbitals (LUMO, LUMO + 1, and LUMO + 2) of {Ag ₇ } ⁵⁺ are mainly derived from the Wd orbitals of the POM skeleton, whereas LUMO + 3 has p-orbital-like symmetry and is not on {Ag ₇ } ⁵⁺ nanoclusters. Localized (Fig. 30b).

Finally, in order to investigate the optical properties of Ag7, a time-dependent DFT calculation was performed using the same functional and BS2. Solvent effects were also evaluated using the C-PCM solvent model. The theoretical UV-vis spectra obtained showed prominent absorption bands in the visible light region of about 420 nm and absorption bands in the UV light region (300-400 nm), which were very close to the experimental data (these were very close to the experimental data). FIG. 27b). Absorption bands near 420 nm are characterized by HOMO → LUMO, HOMO → LUMO + 3, and HOMO → LUMO + 9 transitions (S ₁ , 419 nm, f = 0.116), which are {Ag ₇ } ⁵⁺ → POM (Wd) and { Ag ₇ } ⁵⁺ → {Ag ₇ } ⁵⁺ It was attributed to charge transfer (Fig. 30). Absorption bands in the range of 300 to 400 nm are mainly characterized by HOMO → LUMO + 7, HOMO → LUMO + 12, HOMO → LUMO + 13 transitions ( _S8 , 305 nm, f = 0.188), which are {Ag ₇ } ⁵⁺ → POM ( Wd) Assigned to charge transfer. Other minor transitions (S2 _- S7, _313-365nm , f = 0.01-0.03) were also attributed to { _Ag7 } ⁵⁺ → POM (Wd) charge transfer. Thus, these calculations reveal that the unique {Ag ₇ } ⁵⁺ -POM charge transfer dominates the optical properties of this compound.

[Example 4]
Antiviral test using Ag27 (1) Experimental method Add 90 μL of phosphate buffered saline (PBS buffer) containing M13 phage and 10 μL of a solution containing 4 × 10 ² nmol of silver compound to a 1 mL microtube. It was stirred for 24 hours. After stirring, centrifugation was performed, 10 μL of the supernatant was separated, and 990 μL of PBS buffer was added to prepare a sample solution diluted 10 ² -fold. This diluted solution was diluted 10-fold with PBS buffer, and repeated in the same manner to prepare a sample solution diluted ^{10 3-108} times.
10 μL was separated from the prepared diluted solution, added to 90 μL of a solution containing E. coli, and bathed at 37 ° C. for 30 minutes to infect E. coli with M13 phage. 5 μL of this solution was added dropwise to an agar medium supplemented with ampicillin, and the mixture was allowed to stand at 37 ° C. for 24 hours to select and culture only Escherichia coli infected with M13 phage. After 24 hours, the number of M13 phage in the sample solution was determined from the number of colonies and dilution of E. coli, and the proportion of inactivated M13 phage was determined by comparison with the control condition to which no silver compound was added. Three levels of E. coli colonies were prepared for each dilution, and the average value and standard deviation were determined.

A schematic diagram of the outline of the above experimental method is shown in FIG. 31. Further, FIG. 32 shows an example in which the activity value was calculated for the sample ⁽ Y6) having a dilution ratio of 105.

(2) Evaluation of Concentration Effect of Ag27 Compared with the case where Ag27 was not added, the number of M13 phage capable of infecting E. coli decreased when Ag27 was added, and Ag27 inactivated M13 phage. It was shown to have anti-M13 phage action. Furthermore, it was shown that the proportion of inactivated M13 phage increased with respect to the increase in the amount of Ag27 added. In particular, increasing the addition amount from 0.1 mg / mL to 1 mg / mL greatly improved the anti-M13 phage activity (FIG. 33).

(3) Examination using equimolar silver compounds The amounts of substances of various silver compounds were unified, and the anti-M13 phage activity per mol of the compound was compared. In particular, when Ag27 was used, it was shown that about 90% of M13 phage was inactivated, and in the commercially available silver compound, 25 to 55% of M13 phage were inactivated, which was higher than that of anti-M13 phage. It was shown to have activity (Fig. 34).

Claims (17)

With metal nanoclusters
[YZ ₉ O ₃₄ ] In the composition formula of ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and n is 9 or 10). It contains a multimers of terror polyoxometallate anions and contains defective structural sites.
At least a part of the outer surface of the metal nanocluster is encapsulated inside the multimer.
The metal is a composite metal nanocluster selected from silver or platinum. The multimer is a dimer of a heteropolyoxometallate anion containing a defective structure site, a dimer of a heteropolyoxometallate anion containing one or more other defective structure sites, and / or one or more. The composite metal nanocluster according to claim 1, which is formed by condensing a heteropolyoxometallate anion containing a defective structure site. The composite metal nanocluster according to claim 1 or 2, wherein the metal is silver. The composite metal nanocluster according to any one of claims 1 to 3, wherein the heteropolyoxometallate anion containing the defect structure site is represented by [SiW ₉ O ₃₄ ] ^10- . The composite metal nanocluster according to claim 4, wherein the dimer is represented by [Si ₂ W ₁₈ O ₆₆ ] ^16- . The composite metal nanocluster according to any one of claims 1 to 5, wherein the multimer is composed of a dimer of a heteropolyoxometallate anion containing three defective structure sites. One of claims 1 to 5, wherein the multimer is composed of a dimer of a heteropolyoxometallate anion containing one defective structure site and a heteropolyoxometallate anion containing one defective structure site. The composite metal nanocluster according to item 1. Formula: [Ag ₂₇ (Y ₂ Z ₁₈ O ₆₆ ) ₃ ] A compound containing an anion represented by ^s- .
(In the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and s is selected from an integer from 25 to 31.) A compound having the composition of _Xs [Ag ₂₇ (Y ₂ Z ₁₈ O ₆₆ ) ₃ ] (in the formula, X represents a counter cation, which may be the same pair cation or a different pair cation). [Ag ₇ (Y ₃ Z ₂₇ O ₉₆ )] A compound containing an anion represented by ^t- .
(In the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and t is selected from an integer from 10 to 13.) A compound having the composition of _Xt [Ag ₇ (Y ₃ Z ₂₇ O ₉₆ )] (in the formula, X represents a counter cation, which may be the same pair cation or a different pair cation). With silver nanoclusters
[YZ ₉ O ₃₄ ] In the composition formula of ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and n is 9 or 10). It contains a multimer in which three dimers of heteropolyoxometallate anion are condensed, and at least a part of the outer surface of the silver nanocluster is encapsulated inside the multimer. , A method for preparing composite silver nanoclusters,
(A) A step of providing a mixture of AgL (where L represents a counter anion) and an organic solvent,
(B) In the mixture, the composition formula of [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, n is 9). Alternatively, by adding a compound containing a telopolyoxometallate anion containing a defective structure site represented by 10), the composition formula of [Ag ₂ (Y ₂ Z ₁₈ O ₆₆ )] ^m- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo and m is 14 or 16) to contain the defect structure site containing the two Ag ⁺ cations. The preparation method comprising a step of obtaining a dimer of telopolyoxometallate anion and (c) a step of adding a reducing agent and AgL (L represents a counter anion) to a solution containing the dimer. With silver nanoclusters
[YZ ₉ O ₃₄ ] In the composition formula of ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and n is 9 or 10). It contains a multimer in which three dimers of heteropolyoxometallate anion are condensed, and at least a part of the outer surface of the silver nanocluster is encapsulated inside the multimer. , A method for preparing composite silver nanoclusters,
(D) A step of providing a mixture of AgL (where L represents a counter anion), an organic solvent and water.
(E) In the mixture, the composition formula of [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, n is 9). Or 10), a step of adding a compound containing a telopolyoxometallate anion to the defect structure site, and (f) after stirring for a predetermined time, a reducing agent and AgL (L is a counter anion). The preparation method comprising the step of adding (represented). With silver nanoclusters
[YZ ₉ O ₃₄ ] In the composition formula of ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, and n is 9 or 10). A complex silver nano that contains a multimer in which three heteropolyoxometallate anions are condensed, and at least a part of the outer surface of the silver nanocluster is encapsulated inside the multimer. It ’s a method of preparing clusters.
(G) A step of providing a mixture of AgL (where L represents a counter anion) and an organic solvent,
(H) In the mixture, the composition formula of [YZ ₉ O ₃₄ ] ^n- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo, n is 9). Alternatively, by adding a compound containing a telopolyoxometallate anion containing a defective structure site represented by 10), the composition formula of [Ag ₂ (Y ₂ Z ₁₈ O ₆₆ )] ^m- (in the formula, Y is selected from P, Ge, Si or As, Z is selected from W or Mo and m is 14 or 16) to contain the defect structure site containing the two Ag ⁺ cations. The above-mentioned preparation method comprising a step of obtaining a dimer of a telopolyoxometallate anion and a step of allowing a solution containing the dimer obtained in the steps (i) and (h) to stand at room temperature for a predetermined time. An antibacterial and / or antiviral product comprising the composite metal nanocluster according to any one of claims 1 to 7 or the compound according to any one of claims 8 to 11. A coating composition containing the composite metal nanocluster according to any one of claims 1 to 7, or the compound, water, an organic solvent or a mixture thereof, and a resin according to any one of claims 8 to 11. .. A coating agent containing the composite metal nanocluster according to any one of claims 1 to 7, or the compound, water, an organic solvent or a mixture thereof, and a resin according to any one of claims 8 to 11.

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