JP7626419B2 - Porous network complex crystal for guest molecule analysis, method for preparing sample for crystal structure analysis, and method for determining molecular structure - Google Patents

Description

The present invention relates to a porous network complex crystal for guest molecule analysis. It also relates to a method for preparing a sample for crystal structure analysis and a method for determining a molecular structure using the porous network complex crystal.

Porous coordination network complexes (PCNs) consisting of metal ions and organic ligands have an infinite structure that can maintain its structure even after the solvent is removed, and technologies utilizing the pores have been proposed. For example, PCNs that undergo reversible structural changes in response to the adsorption and desorption of guests in the pores (Non-Patent Document 1), PCNs combining 2,4,6-tris(4-pyridyl)triazine ligands with _ZnBr2 (Non-Patent Documents 2 and 3), and PCNs combining tripyridylhexaazaphenalenate (K ⁺ TPHAP ^- ) ligands with _ZnI2 have been reported (Non-Patent Document 4). In addition, the present inventors recently reported a synthesis example of PCN using 2,4,6-tris(3-pyridyl)hexaazaphenalenate ligands, cobalt(II) chloride, and terephthalic acid (Non-Patent Document 5).

Sujit K. Ghosh et al., Angew. Chem., 2013, 125, 1032 Masaki Kawano et al., Angew. Chem. Int. Ed. 2008, 47, 1269 -1271 Makoto Fujita et al. NATURE CHEMISTRY, VOL 3, 2011 Masaki Kawano, et al. CrystEngComm., 2014, 16, 6335 Masanori Kono et al., "Synthesis of network complexes by controlling the substituents of multipoint interacting ligands," Proceedings of the Annual Meeting of the Crystallographic Society of Japan, November 2018, PB-I-04.

Compared to zeolites and activated carbon, PCN has a very large surface area, and isostructures can be generated by customizing its structure, so it has attracted attention in the fields of catalyst support, adsorption, and separation and purification. Furthermore, if it were possible to provide PCN crystals that can be used to analyze guest molecules, and in particular if it were possible to provide PCN crystals that can analyze medium molecules (molecules with molecular weights of about 500 to 3000), which have been considered difficult to analyze until now, it is expected that pharmaceutical development will be dramatically accelerated. However, in order to incorporate medium molecules as guest molecules, it is necessary to increase the pore size. Furthermore, it is desirable to suppress structural fluctuations in PCN crystals in order to improve the accuracy of analysis.

Note that, although the above describes the case where medium-sized molecules are used as guest molecules, similar issues can arise regardless of the molecular weight.

The present invention has been made in view of the above background, and has as its first object to provide a porous network complex crystal for guest molecule analysis that has a large pore size and is capable of suppressing structural fluctuations, a method for preparing a sample for crystal structure analysis, and a method for determining a molecular structure. In addition, a second object is to provide a porous network complex crystal that can be used for purposes other than analysis.

前記コネクター分子は二座配位子であり、前記二座配位子のそれぞれの配位子と当該コネクター分子の重心との成す角度が７０～１８０°であり、
前記３-ピリジニル基の軸の自由回転が抑制されたゲスト分子解析用の細孔性ネットワーク錯体結晶。
［２］： 前記遷移金属には、更に溶媒分子が配位しており、前記遷移金属と前記溶媒分子の配位結合は、前記遷移金属と前記三座配位子および前記遷移金属と前記コネクター分子の配位結合よりも弱い［１］に記載のゲスト分子解析用の細孔性ネットワーク錯体結晶。
［３］： 前記遷移金属は２価の金属である［１］または［２］に記載のゲスト分子解析用の細孔性ネットワーク錯体結晶。
［４］： 前記細孔は、ハニカム状の孔部と、前記ハニカム状の孔部同士を連通させる、当該ハニカム状の孔部よりもサイズの小さい孔部を含む［１］～［３］のいずれかに記載のゲスト分子解析用の細孔性ネットワーク錯体結晶。
［５］： 前記三座配位子が一般式（II）で表される［１］～［４］いずれかに記載のゲスト分子解析用の細孔性ネットワーク錯体結晶。

但し、一般式（ＩＩ）中のＸは、一般式（ＩＩＩ）で表される化合物および化合物（ＩＶ）で表される化合物から選択され、Ｙ^１～Ｙ^３はそれぞれ独立に、Ｘと前記３－ピリジニル基が直結する単結合、炭素－炭素二重結合、炭素－炭素三重結合から選択される。

但し、一般式（ＩＩＩ）中のＺ^１～Ｚ^６はそれぞれ独立に、Ｃ－ＨまたはＮである。

［６］： 前記ゲスト分子の分子量が５００～３０００の中分子である［１］～［５］のいずれかに記載のゲスト分子解析用の細孔性ネットワーク錯体結晶。
［７］： 解析対象化合物を溶媒に溶解した試料を用意し、
前記試料に、
［１］～［６］のいずれかに記載のゲスト分子解析用の細孔性ネットワーク錯体結晶を分散させ、
前記細孔性ネットワーク錯体結晶の細孔内に、前記解析対象化合物を取り込む結晶構造解析用試料の作製方法。
［８］： ［７］に記載の結晶構造解析用試料の作製方法により得られた結晶構造解析用試料を用いて、結晶構造解析を行うことを特徴とする解析対象化合物の分子構造決定方法。 As a result of extensive investigations, the present inventors have found that the problems of the present invention can be solved in the following aspect, and have thus completed the present invention.
[1]: A porous network complex crystal for guest molecule analysis,
It has a three-dimensional network structure and has pores that contain guest molecules.
the three-dimensional network structure is formed by coordinating a tridentate ligand and a connector molecule to a transition metal;
The tridentate ligand is a compound having a three-branched structure represented by the following general formula (I) in which the nitrogen atoms of the 3-pyridinyl group each function as a ligand (wherein W is an aromatic group which may contain a heteroatom):

the connector molecule is a bidentate ligand, and each ligand of the bidentate ligand forms an angle with the center of gravity of the connector molecule of 70 to 180°;
A porous network complex crystal for analyzing guest molecules in which the free rotation of the 3-pyridinyl group axis is restricted.
[2]: The porous network complex crystal for guest molecule analysis according to [1], wherein a solvent molecule is further coordinated to the transition metal, and the coordinate bond between the transition metal and the solvent molecule is weaker than the coordinate bonds between the transition metal and the tridentate ligand and between the transition metal and the connector molecule.
[3]: The porous network complex crystal for guest molecule analysis according to [1] or [2], wherein the transition metal is a divalent metal.
[4]: The porous network complex crystal for guest molecule analysis according to any one of [1] to [3], wherein the pores include honeycomb-shaped pores and pores that are smaller in size than the honeycomb-shaped pores and connect the honeycomb-shaped pores to each other.
[5]: The porous network complex crystal for guest molecule analysis according to any one of [1] to [4], wherein the tridentate ligand is represented by general formula (II):

In the general formula (II), X is selected from the compounds represented by the general formula (III) and the compounds represented by the general formula (IV), and Y ¹ to Y ³ are each independently selected from a single bond, a carbon-carbon double bond, and a carbon-carbon triple bond in which X is directly linked to the 3-pyridinyl group.

In the general formula (III), Z ¹ to Z ⁶ each independently represent CH or N.

[6]: The porous network complex crystal for guest molecule analysis according to any one of [1] to [5], wherein the guest molecule has a molecular weight of 500 to 3,000 and is a medium molecule.
[7]: Prepare a sample by dissolving the target compound in a solvent;
The sample is
Dispersing the porous network complex crystal for guest molecule analysis according to any one of [1] to [6];
A method for preparing a sample for crystal structure analysis, comprising incorporating the compound to be analyzed into the pores of the porous network complex crystal.
[8]: A method for determining the molecular structure of a compound to be analyzed, comprising carrying out crystal structure analysis using a sample for crystal structure analysis obtained by the method for preparing a sample for crystal structure analysis described in [7].

The present invention has the excellent effect of providing a porous network complex crystal for guest molecule analysis that has a large pore size and can suppress structural fluctuations, a method for preparing a sample for crystal structure analysis, and a method for determining a molecular structure.

1A is a schematic diagram of a conventional tridentate ligand, and FIG. 1B is a schematic diagram of a tridentate ligand according to the present embodiment. FIG. 2 is a schematic structural diagram showing an example of a structural unit of the PCN crystal of the present embodiment. FIG. 2 is a schematic structural diagram showing an example of a PCN crystal according to the present embodiment. FIG. 2 is a schematic diagram for explaining an example of the stereochemical configuration of nitrogen of a 3-pyridinyl group of a tridentate ligand in PCN according to the present embodiment. FIG. 2 is a schematic structural diagram showing an example of a bonding state between a transition metal of PCN and an interlayer connector according to this embodiment. (a) Powder X-ray profile of the PCN crystal according to Example 1. (b) Powder X-ray profile after the PCN crystal according to Example 1 is ground in a mortar. (c) X-ray profile of the PCN crystal according to Example 1 obtained by simulation. 1 is a micrograph of a PCN crystal according to Example 1. 1 is a structural diagram of the PCN crystal according to Example 1 as viewed from the c-axis direction, determined by X-ray structural analysis. FIG. 9 is a structural diagram of the PCN crystal from FIG. 8, with the tridentate ligand hidden, viewed from the c-axis direction, determined by X-ray structural analysis. 1 is a structural diagram of the PCN crystal of Example 1, obtained by X-ray structural analysis with the tridentate ligand hidden and viewed from the b-axis direction. FIG. 2 is a partially enlarged view of the structure determined by X-ray structural analysis in which part of the DMF in the PCN crystal of Example 1 is replaced with water molecules. FIG. 2 is a diagram showing a DTG-DTA profile of the PCN crystal according to Example 1. FIG. 1 is a structural diagram of a guest molecule (anthracene) trapped in the pores of the PCN crystal in Example 2, determined by X-ray structural analysis. Absorption spectra over time after adding PCN crystals to a DMF solution of iodine. FIG. 1 is a graph showing the change in absorbance over time when a PCN crystal incorporating iodine as a guest is irradiated with ultraviolet light. FIG. 1 is a structural diagram obtained by X-ray structural analysis of a guest molecule (triphenylene) trapped in the pores of the PCN crystal in Example 4. FIG. 1 is a structural diagram obtained by X-ray structural analysis of a guest molecule (safflower pigment carthamin) trapped in the pores of the PCN crystal of Example 5.

Below, an example of an embodiment to which the present invention is applied is described. Note that other embodiments are also included within the scope of the present invention as long as they are consistent with the spirit of the present invention. Also, the size and proportions of each part in the following figures are for the convenience of explanation and are not intended to be limiting.

The porous network complex (hereinafter referred to as PCN) crystal for guest molecule analysis according to this embodiment has a three-dimensional network structure. This three-dimensional network structure is formed by coordinating a tridentate ligand and a connector molecule to a transition metal. In addition, the PCN crystal has pores that contain guest molecules.

但し、式（１）中のＷはヘテロ原子を含んでいてもよい芳香族基である。
三座配位子の３－ピリジニル基の窒素原子がそれぞれ遷移金属に配位され、当該配位によって、３－ピリジニル基の軸の自由回転が抑制されている。 The tridentate ligand is a compound having a three-branched structure represented by the following general formula (I) in which the nitrogen atoms of the 3-pyridinyl group each function as a ligand.

However, W in formula (1) is an aromatic group which may contain a heteroatom.
The nitrogen atoms of the 3-pyridinyl groups of the tridentate ligand are each coordinated to a transition metal, and the free rotation of the axis of the 3-pyridinyl group is restricted by the coordination.

The connector molecule is a bidentate ligand, and the angle between the center of gravity of the connector molecule and each ligand of the bidentate ligand is 70 to 180°. The center of gravity here refers to the center of mass of the connector molecule.

Incidentally, the tridentate ligand used in the PCN disclosed in the above Non-Patent Documents 2 and 3 is 2,5,8-tri(4'-pyridyl)-1,3,4,6,7,9-hexaazaphenalene (4-TPHAP ^- ), which is a compound with a three-branched structure having three 4-pyridinyl groups. The axis of this 4-pyridinyl group rotates freely as shown in FIG. 1(a), and as shown in the same figure, the symmetry is excellent. Furthermore, even in PCN in which the nitrogen of this 4-pyridinyl group is coordinated with a transition metal, the free rotation of the axis of the 4-pyridinyl group itself is not inhibited.

In contrast, the tridentate ligand of the PCN crystal used in this embodiment is a compound with a three-branched structure with three 3-pyridinyl groups as ligands, as shown in general formula (I). As shown in FIG. 1(b), this tridentate ligand increases the degree of freedom of the topological structure due to the free rotation of the axis of the 3-pyridinyl group. In other words, by using a tridentate ligand with a three-branched structure having a 3-pyridinyl group, a structure with reduced symmetry can be obtained.

In addition, in the PCN crystal used in this embodiment, the free rotation of the axis of the pyridinyl group is inhibited by the bond between the nitrogen of the 3-pyridinyl group and the transition metal. By inhibiting the free rotation of the 3-pyridinyl group, it is possible to reduce dynamic movement more than when a tridentate ligand with a three-branched structure having a 4-pyridinyl group is used. As a result, it is expected that the analytical accuracy of guest molecules will be improved, and that it will be possible to analyze guest molecules that have been difficult to analyze until now. In addition, by using a PCN crystal having a tridentate ligand with a three-branched structure having a 3-pyridinyl group, the opening diameter of the pores can be widened.

The pores of the three-dimensional network are regularly formed by combining multiple tridentate ligands and connector molecules with the transition metal via coordinate bonds. The shape of the pores can vary depending on the raw material molecules used. A suitable example is an embodiment that includes honeycomb-shaped pores and pores that are smaller than the honeycomb-shaped pores and connect the honeycomb-shaped pores to each other. The opening size of the pores can be easily adjusted depending on the type of tridentate ligand, connector molecule, and transition metal.

The tridentate ligand is a compound that satisfies the above formula (I) and has three nitrogen atoms of the 3-pyridinyl groups as ligands, and is not limited as long as it can form a PCN crystal together with the connector molecule and the transition metal, but it is preferable to use a tridentate ligand that is substantially planar in shape to form a two-dimensional network. It is also preferable that the tridentate ligand is triangular with the 3-pyridinyl groups of the tridentate ligand as vertices. W in formula (1) is preferably a delocalized aromatic plane capable of π-π interactions. The tridentate ligand may be used alone or in combination of two or more types.

但し、一般式（ＩＩ）中のＸは、一般式（ＩＩＩ）で表される化合物および化合物(ＩＶ)で表される化合物から選択され、Ｙ^１～Ｙ^３はそれぞれ独立に、Ｘと前記３－ピリジニル基が直結する単結合、炭素－炭素二重結合、炭素－炭素三重結合から選択される。

但し、一般式（ＩＩＩ）中のＺ^１～Ｚ^６はそれぞれ独立に、Ｃ－ＨまたはＮである。

A suitable example of the tridentate ligand is a compound represented by the general formula (II).

In the general formula (II), X is selected from the compounds represented by the general formula (III) and the compounds represented by the general formula (IV), and Y ¹ to Y ³ are each independently selected from a single bond, a carbon-carbon double bond, and a carbon-carbon triple bond that directly connects X to the 3-pyridinyl group.

In the general formula (III), Z ¹ to Z ⁶ each independently represent CH or N.

Particularly preferred tridentate ligands include compounds selected from the group of compounds represented by the following formulae:

The type of transition metal is not particularly limited. Specific examples include copper, chromium, cadmium, zinc, and cobalt. The valence of the transition metal is not particularly limited, but from the viewpoint of ease of synthesis of PCN crystals, it is preferable that the transition metal is divalent. It is possible to use multiple types of transition metals, but from the viewpoint of ease of structural analysis, it is preferable to use a single transition metal.

Examples of the ligand of the connector molecule include heteroatoms such as nitrogen atoms, oxygen atoms, and phosphorus atoms. The nitrogen atom can be, for example, the nitrogen of an amino group or a pyridinyl group. The oxygen atom can be, for example, the oxygen of a carboxy group, a carbonyl group, a hydroxyl group, or a nitro group. The phosphorus atom can be, for example, the phosphorus of a phenylphosphine group. The angle between each ligand of the bidentate ligand of the connector molecule and the center of gravity of the connector molecule is preferably 90° or more, more preferably 110° or more, even more preferably 140° or more, and particularly preferably 160° or more.

Suitable examples of the connector molecule include the following compounds:

The PCN crystal of this embodiment can take various forms. FIG. 2 shows an example of a structural unit of a PCN crystal, and FIG. 3 shows a structural diagram of a part of this PCN crystal. In the example of FIG. 2, the structural unit of the PCN crystal 1 is formed by coordinating four transition metals 3 (Co ²⁺ ) with two tridentate ligands 2 and three connector molecules 4 (carboxy groups of terephthalic acid). In addition, two solvent molecules 5 (DMF) are coordinated to the transition metal. In the example of FIG. 3, the pores are arranged in a honeycomb shape and have a three-dimensional network structure having hexagonal pores 6. From the viewpoint of the stability of the PCN crystal, it is preferable that the hexagonal openings of the two-dimensional network are hexagonal from a macroscopic viewpoint.

Furthermore, in the PCN crystal of Figure 2, two DMF molecules, which are the solvent molecules used during synthesis, are coordinated to the cobalt ion per unit structure. The solvent molecules incorporated into such unit crystals preferably have a weaker bond with the transition metal than the coordinate bond between the transition metal and the tridentate ligand and the coordinate bond between the transition metal and the connector molecule. By incorporating such solvent molecules into the crystal structure unit, it is expected that the structural fluctuations when analyzing guest molecules will be reduced and the analytical accuracy will be improved. It will also be possible to replace the solvent depending on the guest molecule to be incorporated, which is expected to increase the number of objects to be analyzed. Furthermore, it will be possible to confirm these solvent molecules inside the pores through analysis.

As shown in the partially enlarged view of FIG. 5, the Co ²⁺ of the PCN crystal 1 in FIG. 2 is coordinated to the nitrogen atom of the 3-pyridinyl group of the tridentate ligand and the carboxyl group of the terephthalic acid. In this example, two of the 3-pyridinyl groups of the tridentate ligand are arranged close to each other as shown in FIG. 4, and are fixed by one terephthalic acid via Co ²⁺ . In this way, the tridentate ligand 2 of the PCN crystal 1 is fixed in a structure with low symmetry. By using the 3-pyridinyl group, it is possible to suppress structural fluctuation, rigidify the framework structure, increase the periodicity of the structure, and improve the crystallinity. For this reason, a crystal suitable for structural analysis can be provided.

The shape of the pores can be adjusted by changing the structure of the connector molecules and the structure of the tridentate ligand. The size of the pores, expressed as the body diagonal distance when the pores not filled with spheres of the van der Waals radius of the atoms forming the network structure are considered as cubes, is, for example, 0.8 to 1.2 nm. The maximum diameter of the pores of the PCN crystal, which is defined as the short axis distance when a cut is made at the opening of the pore and the cut is considered as a rectangle, is not limited, but from the viewpoint of using it as a sample for crystal structure analysis, it is preferably 1.5 to 5.0 nm. It is more preferably 2.0 to 5.0 nm, and even more preferably 2.5 to 5.0 nm. The opening diameter of the pores is mainly determined by the type of tridentate ligand. By making the opening diameter size of the pores of the two-dimensional network 1.5 nm or more, it is possible to selectively incorporate compounds with molecular weights of, for example, about 100 to 7000 into the hollow, making it possible to apply it to various uses including crystal structure analysis.

The PCN crystal according to this embodiment is suitable as a crystal for analyzing the crystal structure of guest molecules with high molecular weights, such as pharmaceuticals and peptides. In addition, as shown in FIG. 2, by forming a crystal having an organic solvent as a ligand, the position of the guest molecule relative to the solvent molecule can also be analyzed. Furthermore, by making the bond between this organic solvent and the transition metal weaker than the coordinate bond between the tridentate ligand and the transition metal, and between the connector molecule and the transition metal, the degree of freedom to replace it with other solvent molecules can be increased. Therefore, it is possible to adjust the environmental field of the pores of the PCN crystal according to the guest molecule. These effects are expected to improve the accuracy of crystal structure analysis.

Although the above examples show its use for analysis, it is also suitable for applications such as refining substances and as a reaction field in closed spaces. In addition, since its surface area is significantly larger than that of zeolites, it can be used as an adsorbent or for purification purposes. It can also be used for sensing organic substances, i.e. as a chemical sensor material. It can also be used in drug delivery systems that release adsorbed guest molecules in response to external stimuli such as UV light.

(Production method)
Next, an example of a method for producing PCN crystals will be described, although the method for producing PCN crystals of the present invention is not limited to the following method.

First, a tridentate ligand, a transition metal or transition metal compound, and a connector molecule are placed in a container and heated, and synthesis can be performed using the solvothermal method. This allows PCN crystals with pores to be produced by a one-pot reaction in a self-organizing manner. After synthesis of PCN, crystals can be obtained by thorough washing. Instead of the solvothermal method, PCN can also be synthesized using the solution diffusion method, electrochemical synthesis method, microwave irradiation method, mechanochemical synthesis method, or ultrasonic synthesis method. Various PCNs can be synthesized by changing the solvent and its concentration, the molar ratio of metal to ligand, temperature, and metal ions.

The molar ratio of the tridentate ligand to the transition metal used is 1:1 to 1:10, preferably 1:1 to 1:5, and more preferably 1:1 to 1:3. The molar ratio of the connector molecule to the transition metal is 1:1 to 1:7, preferably 1:1 to 1:5, and more preferably 1:1 to 1:3.

The organic solvent used is not particularly limited as long as it can uniformly dissolve the tridentate ligand and the transition metal. Examples of the solvent include aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene, 1,2-dichlorobenzene, mesitylene, and nitrobenzene; sulfoxides such as dimethyl sulfoxide (DMSO); amides such as N,N-dimethylformamide; ethers such as tetrahydrofuran, 1,2-dimethoxyethane, and 1,4-dioxane; alcohols such as methanol, ethanol, and isopropyl alcohol; and ketones such as acetone and methyl ethyl ketone. The solvent may be used alone or in combination of two or more.
Among these, aromatic hydrocarbons are preferred as the solvent for the transition metal compound, and nitrobenzene is more preferred, because the porous network complex of the present invention can be synthesized in a higher yield. Furthermore, aromatic hydrocarbons and sulfoxides are preferred as the solvent for the tridentate organic ligand, and sulfoxides are particularly preferred.

The precipitated PCN crystals can be collected by filtration. The structure of the PCN crystals can be confirmed by elemental analysis, IR, UV absorption spectroscopy, visible light absorption spectroscopy, X-ray single crystal structure analysis, etc.

(Method of preparing a sample for crystal structure analysis)
Next, a method for preparing a sample for crystal structure analysis according to the present embodiment will be described. The preparation of the sample for crystal structure analysis according to the present embodiment involves incorporating a compound to be analyzed into the pores of the PCN crystal of the present embodiment, and using the compound as a sample for structure analysis.

First, a sample is prepared by dissolving the compound to be analyzed in a solvent, and the PCN crystal according to this embodiment is dispersed in this sample. The compound to be analyzed is then incorporated into the pores of the PCN crystal, and the solvent is distilled off, etc., to produce the crystal.

The mixture containing the compound to be analyzed can be brought into contact with the PCN crystal and the molecules of the compound to be analyzed can be incorporated into the pores of the PCN crystal by a known method.

The compounds to be analyzed are not particularly limited as long as they are of a size that can enter the pores of the PCN crystal. It can be applied to a wide variety of compounds, including low molecular weight compounds, medium molecular weight compounds such as pharmaceuticals, and chiral compounds. For example, molecules with a molecular weight of about 50 to 7000 can be analyzed. Compounds with a molecular weight of 5000 or less are preferable, with 480 to 4000 being more preferable, and 500 to 3000 being particularly preferable.

The method of contacting the PCN crystal with the target compound is not particularly limited. For example, a solution of the target compound may be prepared and the PCN crystal may be brought into contact with this solution, or, if the target compound is a liquid or gas, the molecules of the target compound may be incorporated into the pores of the PCN crystal by directly contacting the PCN crystal with the target compound. Among these, the method of preparing a solution of the target compound and contacting the PCN crystal with this solution is preferred because it is easier to obtain a higher quality sample for crystal structure analysis.

In addition, when a solution containing the target compound is used or when the target compound is liquid, the contact operation can be performed by immersing the single crystal in a solution containing the target compound, or by filling the single crystal into a capillary and then passing a solution containing the target compound through the capillary.

The solvent of the solution containing the target compound may be any solvent that does not dissolve the single crystal used and dissolves the target compound. Examples of organic solvents include aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene, 1,2-dichlorobenzene, nitrobenzene, and mesitylene; aliphatic hydrocarbons such as n-butane, n-pentane, n-hexane, and n-heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and cycloheptane; nitriles such as acetonitrile and benzonitrile; sulfoxides such as dimethyl sulfoxide (DMSO); amides such as N,N-dimethylformamide and n-methylpyrrolidone; ethers such as diethyl ether, tetrahydrofuran, 1,2-dimethoxyethane, and 1,4-dioxane; alcohols such as methanol, ethanol, and isopropyl alcohol; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; halogenated hydrocarbons such as dichloromethane, chloroform, carbon tetrachloride, and 1,2-dichloroethane; esters such as methyl acetate, ethyl acetate, ethyl lactate, and ethyl propionate; and water. The solvents can be used alone or in combination of two or more.

The contact time between the compound to be analyzed and the PCN crystal of this embodiment is not particularly limited, but is usually several minutes to several days. Depending on the compound, the contact time can be shortened or lengthened as appropriate. The contact temperature can be in the range of, for example, -30 to 200°C, and is not particularly limited. It is preferable to contact the compound to be analyzed at a temperature at which it is easy to handle.

A sample for crystal structure analysis is one in which molecules of the compound to be analyzed are incorporated into the pores of a PCN crystal. Due to the size of the opening diameter of the pores, the compound to be analyzed is arranged regularly within the pores. Regularly arranged here means that the molecules of the compound to be analyzed are incorporated into the pores to an extent that their structure can be determined by crystal structure analysis.

The sample for crystal structure analysis may be one that can determine the molecular structure of the compound to be analyzed, and it is not necessary that the molecules of the compound to be analyzed are incorporated into all of the pores of the PCN crystal. The molecular structure of the compound to be analyzed is determined by performing crystal structure analysis of the compound to be analyzed using the above-mentioned sample for crystal structure analysis. X-ray diffraction, neutron diffraction, etc. can be used for the structure analysis. The molecular structure of the compound to be analyzed can be determined by performing crystal structure analysis using the sample for crystal structure analysis obtained by the method for preparing a sample for crystal structure analysis.

[Example]
The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

(Experimental Example 1)
[Synthesis of 2,5,8-tri(3'-pyridyl)-1,3,4,6,7,9-hexaazaphenalene potassium (3-TPHAPK)]
4.1 g (26.0 mmol) of 3-amidinopyridine hydrochloride and 0.86 g (6.7 mmol) of potassium tricyanomethide were thoroughly mixed in a mortar, then transferred to a pressure vessel and heated at 180° C. for 20 hours. The obtained black solid was transferred to a mortar and ground to reduce the particle size, then 300 cm ³ of distilled water was added, stirred at room temperature for 3 hours, and filtered. Then, impurities were extracted using ethyl acetate until the organic layer became colorless. Then, the aqueous layer was dried using a rotary evaporator. The obtained brown solid was dissolved in 5 M hydrochloric acid to a saturated solution. Then, 5 M aqueous potassium hydroxide solution was added dropwise until the precipitation of solids stopped. The precipitated solid was filtered. The obtained solid was dissolved in methanol, acetone was added in an amount three times the amount, filtered, and the filtrate was dried under reduced pressure to obtain 286 mg (0.65 mol, yield: 9%) of ocher powder.

¹ H NMR : δ = 7.55 (ddd, 3H, J = 0.8, 4.8, 8.0Hz ), 8.69 (dd, 3H, J = 2.0, 8.6 Hz), 8.78 (dt, J = 2.0, 8.4 Hz), 9.61 (d, 3H, J = 2.8 Hz). ¹³ CNMR : δ 103.0 , 123.7 , 134.6 , 135.9 , 149.7 , 151.7 , 166.4 , 166.7.
calcd. (%) for C 22.7 H 23.08 KN 9 O 4.84 (=C 22 H 12 N 9 K (CH 4 O) 0.70 (H 2 O) 4.14 ): C, 50.63; H,4.32; N,23.41;. Found: C, 50.63; H,4.09; N, 23.41. The results of NMR and elemental analysis are as follows, and it was confirmed that the compound represented by formula (VI) was obtained.

¹ H NMR: δ = 7.55 (ddd, 3H, J = 0.8, 4.8, 8.0Hz ), 8.69 (dd, 3H, J = 2.0, 8.6 Hz), 8.78 (dt, J = 2.0, 8.4 Hz), 9.61 (d, 3H, J = 2.8 Hz). ¹³ CNMR: δ 103.0, 123.7, 134.6, 135.9, 149.7, 151.7, 166.4, 166.7.
calcd. (%) for C 22.7 H 23.08 KN 9 O 4.84 (=C 22 H 12 N 9 K (CH 4 O) 0.70 (H 2 O) 4.14 ): C, 50.63; H,4.32; N,23.41;. Found: C, 50.63; H,4.09; N, 23.41.

[Synthesis of PCN]
Next, 15.8 mg (35.82 μmol) of the above 3-KTPHAP, 17.9 mg (107.7 μmol) of terephthalic acid (BDC), and 25.1 mg (193.3 μmol) of cobalt (II) chloride were placed in a pressure-resistant vessel, and 10 ^cm3 of dehydrated DMF was added and reacted at 80° C. for 7 days to obtain 45.1 mg (17.5 μmol) of reddish purple crystals. The yield was 97.7%.
The results of the elemental analysis are shown below.
calcd (%) for Co4C98.45H140.15N32.55(= Co4C92H92N26O16(C3H7NO)2.15(H2O)16.55): C, 45.96; H,5.49; N,15.33;. Found: C, 45.96; H, 5.49; N, 15.55.

[PCN crystal structure]
FIG. 6 shows the powder X-ray profile of the PCN crystal according to Example 1. FIG. 6(a) shows the X-ray profile of the PCN crystal according to Example 1, FIG. 6(b) shows the X-ray profile after the PCN crystal of Example 1 was crushed in a mortar, and FIG. 6(c) shows the X-ray profile by simulation. In FIG. 6(a), the measurement was performed as a single crystal, so it is considered that there is a part where the relative intensity is different from the simulation of the single crystal due to the selective orientation. On the other hand, in FIG. 6(b), it was confirmed that the peak at 20° is small and the graph is close to the simulation. It can also be inferred that the PCN crystal is obtained with a higher purity than the result of FIG. 6(b).

Figure 2 shows a unit structure diagram of the PCN crystal obtained from the X-ray structure analysis in Example 1, and Figure 7 shows an electron microscope photograph of the PCN crystal of Example 1. As shown in Figure 4, 3-TPHAP (2,5,8-tri(3'-pyridyl)-1,3,4,6,7,9-hexaazaphenalene) in the PCN crystal of Example 1 has a 3-pyridinyl group fixed in a low symmetry arrangement, and the topology of the PCN crystal structure is 3,6-c. This 3,6-c topology has not been reported in any PCN crystals before.

8 to 10 show structural diagrams for explaining the molecular arrangement of the PCN crystal of Example 1. FIG. 8 is a structural diagram of the PCN crystal viewed from the c-axis direction (long axis direction of terephthalic acid), and FIG. 9 is a structural diagram in which 3-TPHAP is hidden in FIG. 8, that is, a structural diagram viewed from the c-axis direction. FIG. 10 is a structural diagram (top view) in the b-axis direction (stacking direction of 3-TPHAP) with 3-TPHAP hidden from the PCN crystal. From these figures, it can be seen that in the PCN crystal, the connector molecule terephthalic acid (BDC) and cobalt ions form a two-dimensional sheet with a honeycomb structure, and 3-TPHAP is crosslinked between them to construct a three-dimensional structure. It was confirmed that the distance between the two Co ²⁺ ions bound to terephthalic acid is 10.4 Å, which is roughly the same as the distance between the nitrogen atoms of the 3-pyridinyl group of the tridentate ligand.

The pore size of the PCN crystal in Example 1 was 8.3 x 12.5 Å in maximum opening size, and the porosity was 48.8%. Furthermore, it was confirmed that DMF was coordinated to the cobalt ions, and that this DMF was regularly aligned in the PCN crystal. The coordination of DMF has the advantage that it makes it easy to analyze guest molecules. Four molecules of DMF are contained in the unit crystal structure, and this is a site with relatively weak bonds to the transition metal. For this reason, it is possible to replace DMF with other solvents from the unit crystal structure, or to remove DMF by heat.

As shown in Figure 5, it was confirmed that the PCN crystal of Example 1 has Co2 ⁺ coordinated asymmetrically, and that the DMFs, which are exchange-labile ligands, are adjacent to each other. The distance between Co2 ⁺ and DMF1 was 2.0962 Å, and the distance between Co2 ⁺ and DMF2 was 2.1230 Å. This result shows that there is a difference in the strength of the coordinate bond between the two DMFs. Of these, DMF2 has a longer bond length, so it is considered to be a weaker bond.

11 is a structural diagram of a PCN crystal in which one of the DMFs coordinated to Co ²⁺ in one of the PCN crystals of Example 1 is replaced with water. The distance between Co ²⁺ and DMF is 2.102 Å, and the distance between Co ²⁺ and water is 2.57 Å. The structure of the PCN crystal of Example 1 determined by X-ray structural analysis is shown in Table 1. The values in parentheses indicate statistical errors for the values in the table.

12 shows the TG-DTA profile of the PCN crystal according to Example 1. From the figure, it was confirmed that the crystal was stable up to about 400 ° C. It is believed that DMF, which is the solvent on the surface and in the pores, is desorbed up to 100 ° C, and then the coordinated DMF is desorbed around 200 ° C. It is also believed that the coordinated connector molecule is desorbed around 400 ° C.

[Guest molecule analysis]
Example 2
Next, a sample for crystal structure analysis was prepared using the PCN crystal according to Example 1. First, the PCN crystal of Example 1 was washed three times with DMF. Then, the PCN crystal was added to a saturated solution of anthracene using DMF as a solvent, and anthracene was included in the PCN crystal. After four days, the structure was analyzed by single crystal X-ray structure analysis (Synchrotron PAL-2D).

Figure 13 shows a structural diagram obtained by X-ray structural analysis when anthracene was incorporated as a guest molecule into the PCN crystal of Example 1. The structure obtained by X-ray structural analysis of the PCN crystal of Example 2 is shown in Table 2. The values in parentheses indicate the statistical error for the values in the table.

As is clear from Figure 13, no interactions such as hydrogen bonds or CH...π were observed between the PCN crystals and anthracene. This means that the anthracene molecules are incorporated in a solvated state in the solvent DMF. In this way, it has the excellent effect of mitigating the influence of interactions resulting from the structure of the PCN crystals and enabling the analysis of guest molecules.

Example 3
An example of an embodiment in which iodine was incorporated into the PCN crystal according to Example 1 will be described. ³ cm3 of DMF solution in which 0.25 mM iodine was dissolved was weighed out, and 1.7 mg of PCN crystal was added thereto. The result of iodine adsorption, that is, the profile of the change over time in the absorption spectrum, is shown in FIG. 14(a). As time passes, the absorption of the DMF-iodine association decreases, which indicates that iodine has been incorporated into the PCN crystal.

Next, a sample in which sufficient PCN crystals had been added to a DMF solution of iodine was irradiated with UV light. As a result, as shown in Figure 15, it was confirmed that the peak of the iodine-DMF association increased with increasing UV irradiation time. This did not occur in the iodine-containing DMF solution that did not contain PCN crystals, suggesting that the iodine incorporated in the PCN crystals was released from the pores by the UV light.

After iodine was released from the PCN crystals by UV light irradiation, iodine was again observed to be taken up by the PCN crystals by turning off the UV light irradiation. It was also confirmed that the rate at which iodine was adsorbed into the PCN crystals had hardly changed compared to the initial time. These results show that UV light irradiation maintained the porosity of the PCN crystals unchanged, and that the release and inclusion of iodine can be controlled by UV light while maintaining porosity.

Example 4
An example of an embodiment in which triphenylene was incorporated into the PCN crystal according to Example 1 will be described. First, the PCN crystal of Example 1 was immersed in ethyl acetate to exchange the solvent. Then, the PCN crystal was added to a triphenylene saturated solution in which ethyl acetate was used as a solvent, and anthracene was included in the PCN crystal. After 7 days, the structure was analyzed by single crystal X-ray structure analysis.

As is clear from Figure 16, no interactions such as hydrogen bonds or CH...π were observed between the PCN crystals and triphenylene. This means that the triphenylene molecules are incorporated in a solvated state in the solvent ethyl acetate. In this way, it has the excellent effect of mitigating the influence of interactions resulting from the structure of the PCN crystals and enabling the analysis of guest molecules.

Example 5
An example of an embodiment in which carthamin, a medium molecule, was incorporated into the PCN crystal according to Example 1 will be described. First, about 0.8 mg of carthamin was dissolved in a solution containing 0.9 μL of DMF and 0.1 μL of water. Then, the PCN crystal according to Example 1 was added together with DMF, a storage solvent, to thereby effect inclusion of carthamin in the PCN crystal. After 7 days, the structure was analyzed by single crystal X-ray structure analysis.

As is clear from FIG. 17, the PCN crystal can capture the solvated state, making it possible to analyze the structure of medium-sized molecules.

1 PCN crystal 2 Tridentate ligand 3 Transition metal 4 Connector molecule 5 Solvent molecule 6 Pore

Claims (8)

A porous network complex crystal for guest molecule analysis, comprising:
The porous network complex crystal comprises a tridentate ligand, a connector molecule, and a transition metal;
The tridentate ligand is a compound having a three-branched structure represented by the following general formula (II) in which the nitrogen atoms of the 3-pyridinyl group each function as a ligand:
the connector molecule is a bidentate ligand, and each ligand of the bidentate ligand forms an angle with the center of gravity of the connector molecule of 110 to 180°;
The present invention has a structural unit formed by four of the transition metals being coordinated to two of the tridentate ligands and three of the connector molecules,
a three-dimensional network structure is formed regularly between the tridentate ligand and the connector molecule and the transition metal via coordinate bonds, and hollow pores are formed in the three-dimensional network structure, and the guest molecules are contained therein;
the transition metal is selected from copper, chromium, cadmium, zinc and cobalt;
A porous network complex crystal for guest molecule analysis in which the free rotation of the axis of the 3-pyridinyl group is restricted by the bond between the nitrogen of the 3-pyridinyl group and the transition metal .
In the general formula (II), X is selected from a group represented by general formula (III) and a group represented by chemical formula (IV), and Y ¹ to Y ³ are each independently selected from a single bond, a carbon-carbon double bond, or a carbon-carbon triple bond directly connecting X to the 3-pyridinyl group.
In the general formula (III), Z ¹ to Z ⁶ each independently represent CH or N.
The porous network complex crystal for guest molecule analysis according to claim 1, wherein the transition metal is further coordinated with a solvent molecule, and the coordinate bond between the transition metal and the solvent molecule is weaker than the coordinate bonds between the transition metal and the tridentate ligand and between the transition metal and the connector molecule. The porous network complex crystal for guest molecule analysis according to claim 1 or 2, wherein the transition metal is a divalent metal. The porous network complex crystal for guest molecule analysis according to any one of claims 1 to 3, wherein the pores include honeycomb-shaped pores and pores that are smaller in size than the honeycomb-shaped pores and connect the honeycomb-shaped pores to each other. The porous network complex crystal for guest molecule analysis according to any one of claims 1 to 4, wherein the connector molecule is a bidentate ligand selected from the group consisting of the following compounds (VI):
... (VI)
The porous network complex crystal for guest molecule analysis according to any one of claims 1 to 5, wherein the molecular weight of the guest molecule is a medium molecule of 500 to 3000. Prepare a sample by dissolving the target compound in a solvent.
The sample is
Dispersing the porous network complex crystal for guest molecule analysis according to any one of claims 1 to 6;
A method for preparing a sample for crystal structure analysis, comprising incorporating the compound to be analyzed into the pores of the porous network complex crystal. A method for determining the molecular structure of a compound to be analyzed, comprising performing crystal structure analysis using a sample for crystal structure analysis obtained by the method for preparing a sample for crystal structure analysis described in claim 7.