Organic compounds and photocatalysts

Abstract

We provide organic compounds suitable for use in photocatalysts. [Solution] The provided organic compound is a chain-like organic compound, the molecular chain of the organic compound having a portion comprising a first section composed of a first structural unit, a second section composed of a second structural unit, and a third section composed of a third structural unit. In the portion, the first section, the second section, and the third section are bonded in this order to form a π-conjugated system, and the energy levels of the lowest unoccupied orbitals of each of the structural units decrease in the order of the first structural unit, the second structural unit, and the third structural unit, and the organic compound can be excited by visible light.

Description

[Technical Field]

[0001] This invention relates to an organic compound and a photocatalyst containing the same. [Background technology]

[0002] The construction of a photoenergy conversion system that converts carbon dioxide (CO2) into a resource is an urgent issue. One of the technologies being considered for application to the above system is CO2 reduction using photocatalysts. Conventionally, solid semiconductor materials such as inorganic semiconductors composed of metal oxynitrides and metal sulfides, and organic polymer semiconductors have been actively researched as photocatalysts. Furthermore, composites in which metal complexes are bonded to semiconductor materials are also being considered for use as photocatalysts.

[0003] For example, Japanese Patent No. 5493572 and Sato et al., "Visible-Light-Induced Selective CO2 Reduction Utilizing a Ruthenium Complex Electrocatalyst Linked to a p-Type Nitrogen-Doped Ta2O5 Semiconductor", Angew. Chem. Int. Ed., 2010, 49, 5101 disclose a photocatalyst that is a composite of an inorganic semiconductor and a metal complex. Kuriki et al., "Visible-Light-Driven CO2 Reduction with Carbon Nitride: Enhancing the Activity of Ruthenium Catalysts", Angew. Chem. Int. Ed., 2015, 54, 2406 disclose a photocatalyst that is a composite of a carbon nitride-based organic semiconductor and a metal complex. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 5493572 [Non-patent literature]

[0005] [Non-Patent Document 1] Sato et al., "Visible-Light-Induced Selective CO2Reduction Utilizing a Ruthenium Complex Electrocatalyst Linked to a p-Type Nitrogen-Doped Ta2O5 Semiconductor", Angew. Chem. Int. Ed., 2010, 49, 5101 [Non-Patent Document 2] Kuriki et al., "Visible-Light-Driven CO2 Reduction with Carbon Nitride: Enhancing the Activity of Ruthenium Catalysts", Angew. Chem. Int. Ed., 2015, 54, 2406 [Overview of the project] [Problems that the invention aims to solve]

[0006] This invention provides organic compounds suitable for use in photocatalysts. [Means for solving the problem]

[0007] [1] The organic compounds according to embodiments of the present invention are A chain-like organic compound, The molecular chain of the organic compound has a portion comprising a first section composed of a first structural unit, a second section composed of a second structural unit, and a third section composed of a third structural unit. In the aforementioned portion, The first section, the second section, and the third section are joined in this order to form a π-conjugated system. The lowest empty orbital level of each of the aforementioned structural units decreases in the order of the first structural unit, the second structural unit, and the third structural unit. The aforementioned organic compound can be excited by visible light. [2] In the organic compounds described in [1] above, the energy gap between the energy level of the highest occupied orbital and the energy level of the lowest unoccupied orbital of the organic compound may be 3.1 eV or less. [3] In the organic compounds described in [1] or [2] above, the number of the second structural units included in the second section may be two or more. [4] In the organic compounds described in any one of the above items [1] to [3], the ratio n2 / n1 of the number of second structural units in the second section to the number of first structural units in the first section n1 to the number of second structural units in the second section n2 is 1 or more and 3 or less. [5] In the organic compounds described in any one of the above paragraphs [1] to [4], the number of the third structural units included in the third section may be two or less. [6] In the organic compounds described in any one of the above items [1] to [5], the LUMO is the lowest unoccupied orbital level of the first structural unit. U1 and the lowest unaired orbital level LUMO of the third structural unit U3 The absolute value of the difference between the two values ​​may be 0.10 eV or greater. [7] In the organic compounds described in any one of the above items [1] to [6], the LUMO is the lowest unoccupied orbital level of the first structural unit. U1 and the lowest unaired orbital level LUMO of the third structural unit U3 Let X (in eV) be the absolute value of the difference between the two, and let n be the number of second structural units in the second section relative to the number of third structural units in the third section. The ratio X / n may be 0.08 eV or more and 0.43 eV or less. [8] In any one of the organic compounds described in [1] to [7] above, at least one structural unit selected from the group consisting of the first structural unit, the second structural unit, and the third structural unit may have a skeleton containing two or more aromatic rings. [9] In any one of the organic compounds described in [1] to [8] above, at least one structural unit selected from the group consisting of the first structural unit, the second structural unit, and the third structural unit may have a skeleton including a condensed aromatic ring.

[10] In any one of the organic compounds described in [1] to [9] above, at least one structural unit selected from the group consisting of the first structural unit, the second structural unit and the third structural unit may have a condensed polycyclic hydrocarbon skeleton.

[11] In the organic compounds described in any one of the above items [1] to

[10] , the first structural unit may have a carbazole skeleton, a condensed polycyclic hydrocarbon skeleton, a thiophene skeleton, or a dibenzothiophene skeleton.

[12] In the organic compounds described in any one of the above items [1] to

[11] , the second structural unit may have a condensed polycyclic hydrocarbon skeleton, a thiophene skeleton, or a dibenzothiophene skeleton.

[13] In the organic compounds described in any one of the above items [1] to

[12] , the third structural unit may have an aromatic diimine skeleton.

[14] In the organic compounds described in any one of the above items [1] to

[13] , the third structural unit may have a structure in which a metal atom or a group of atoms containing a metal atom is coordinately bonded to the organic skeleton.

[15] In the organic compounds described in

[14] above, the organic skeleton may be an aromatic diimine skeleton.

[16] In the organic compounds described in

[14] or

[15] above, the metal atom may be at least one selected from the group consisting of ruthenium, rhenium, platinum, iridium, rhodium, palladium, iron, cobalt, and nickel.

[17] The organic compounds described in any one of the above items [1] to

[16] may be used as photocatalysts.

[18] The organic compounds described in any one of the above items [1] to

[17] may be used for modifying metal particles or metal compound particles.

[19] A photocatalyst according to an embodiment of the present invention comprises an organic compound described in any one of the above [1] to

[18] .

[20] The photocatalyst described in

[19] above may further contain metal particles or metal compound particles.

[21] The photocatalyst described in

[19] or

[20] above may further contain metal ions.

[22] The photocatalyst described in any one of the above paragraphs

[19] to

[21] may be used for the reduction reaction of carbon dioxide, water, or protons, or for the oxidation reaction of water. [Effects of the Invention]

[0008] According to the present invention, an organic compound suitable for use as a photocatalyst is provided. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram illustrating the relationship between the lowest unoccupied orbital levels between the structural units constituting each section of an organic compound according to an embodiment of the present invention. [Figure 2] This graph shows the ultraviolet-visible light absorption characteristics of the organic compounds prepared in the examples. [Figure 3] This is a schematic diagram showing the relationship between the lowest unoccupied orbital energy level of an organic compound according to an embodiment of the present invention and the lowest unoccupied orbital energy level of a reference compound. [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described below. The present invention is not limited to the embodiments described below.

[0011] <<1.Organic compounds>> <1-1.Organic compounds> The organic compound according to the embodiment of the present invention (hereinafter referred to as "organic compound A") is a chain-like compound. The molecular chain of organic compound A has a portion (hereinafter referred to as "part B") which includes a first section composed of a first structural unit, a second section composed of a second structural unit, and a third section composed of a third structural unit. The first structural unit, the second structural unit, and the third structural unit are all different structural units. The molecular chain of organic compound A may contain two or more parts B, or may consist only of one or two or more parts B. Furthermore, a molecular chain containing two or more parts B may have a structure in which parts B are bonded to each other, or may consist only of a structure in which two or more parts B are bonded to each other. In a structure in which parts B are bonded to each other, the first section of one adjacent part B may be bonded to the third section of the other part B, or the first sections of adjacent parts B may be bonded to each other, or the third sections may be bonded to each other. The molecular chain of organic compound A may be linear, branched, or cyclic, as long as it contains parts B.

[0012] The first section consists of one or more first structural units. The second section consists of one or more second structural units. The third section consists of one or more third structural units. The first section usually does not contain structural units other than the first structural units. The second section usually does not contain structural units other than the second structural units. The third section usually does not contain structural units other than the third structural units.

[0013] In part B, the first section, the second section, and the third section are combined in this order to form a π-conjugated system. The first section, the second section, and the third section are preferably directly connected to each other in the above order. However, as long as a π-conjugated system is formed, sections other than the first section, the second section, and the third section may exist between each section. In part B, electron transport between each section through the formed π-conjugated system is possible. The energy levels of the lowest unoccupied molecular orbitals of each structural unit constituting each section decrease in the order of the first structural unit, the second structural unit, and the third structural unit (see Fig. 1). Hereinafter, the levels of the lowest unoccupied molecular orbitals of each of the first structural unit, the second structural unit, and the third structural unit are denoted as LUMO U1 , LUMO U2 , and LUMO U3 respectively. When expressing the values of each LUMO in terms of potential, that is, when expressing so that the higher the energy, the more negative and larger it becomes, LUMO U1 , LUMO U2 , and LUMO U3 are in a relationship that satisfies the formula: -LUMO U1 > -LUMO U2 > -LUMO U3 .

[0014] Also, organic compound A can be excited by visible light. If excited electrons are generated by irradiation with visible light, it can be determined that organic compound A can be excited by visible light. In this specification, visible light means light having a wavelength in the range of 400 to 800 nm. Organic compound A may be excited by light having a wavelength of 400 nm or more, or may be excited by light having a wavelength of 420 nm or more, 440 nm or more, 450 nm or more, 470 nm or more, 490 nm or more, 500 nm or more, 520 nm or more, 540 nm or more, or 550 nm or more. The visible light may be sunlight.

[0015] Organic compound A may have an energy gap suitable for excitation by visible light. The level of the highest occupied molecular orbital of organic compound A (HOMO OC) and the lowest orbital level (LUMO) OC The energy gap Eg1 with respect to the ) is, for example, 3.1 eV or less, and may be 3.0 eV or less, 2.9 eV or less, 2.8 eV or less, 2.7 eV or less, 2.6 eV or less, or even 2.5 eV or less. The lower limit of the energy gap Eg1 is, for example, 1.5 eV or more. 3.1 eV corresponds to the energy of light with a wavelength of 400 nm. In this specification, the levels of the lowest unoccupied orbital and the highest occupied orbital can be values ​​with a standard hydrogen electrode (NHE) evaluated by the method described in the examples as the reference electrode, regardless of whether they are levels as structural units or levels as organic compounds.

[0016] In section B, a π-conjugated system is formed from the first section to the third section, and the energy level of the lowest unoccupied orbital of the first structural unit (LUMO) U1 ) is the lowest unspent orbital level (LUMO) of the third structural unit. U3 ) is higher. Also, organic compound A can be excited by visible light in at least part B. For this reason, the first section can serve as a starting point for electron transition excitation to the third section by visible light. This means that the first section can function as a donor that donates excitation electrons relatively more strongly than the third section. On the other hand, the third section can function as an acceptor that receives excitation electrons relatively strongly. In addition to this, in part B, the lowest unoccupied orbital level (LUMO) of the second structural unit constituting the second section located between the first and third sections is higher. U2 ) but LUMO U1 and LUMO U3It lies between the two. In other words, the energy of the lowest unoccupied orbital of organic compound A has a gradient that decreases from the first section to the third section. This means that the first section and the third section can be separated along the molecular chain while suppressing the inhibition of excited electron transport by the second section. According to the inventors' studies, this separation may contribute to stronger charge separation between the first section and the third section in portion B, and to the reverse movement of excited electrons from the third section to the first section and the suppression of charge recombination caused by this. It is presumed that both the strengthened charge separation and the suppressed charge recombination contribute to the efficient transport of excited electrons to the third section. Organic compound A having portion B suitable for efficient excited electron transport is suitable for use in photocatalysts, particularly in photocatalysts that utilize visible light.

[0017] The above "-LUMO U1 >-LUMO U2 >-LUMO U3 The relationship can be determined as follows: Determine the lowest unoccupied orbital level for organic compound A, and use this as the LUMO. OC Separately, determine the lowest unoccupied orbital level of the first reference compound, which has the same configuration as part B except for lacking only the third section, and use this as the LUMO. RC1 Let's assume that. -LUMO RC1 and-LUMO OC The difference with LUMO OC -LUMO RC1 If it is true, -LUMO U2 >-LUMO U3 It can be determined that this is true. Furthermore, the lowest unoccupied orbital level of the second reference compound, which has the same configuration as part B except that it lacks only the second and third sections, is determined and this is the LUMO. RC2 Let's assume that. -LUMO RC2 and-LUMO RC1 The difference with LUMO RC1 -LUMO RC2 If it is true, -LUMO U1 >-LUMO U2 It can be concluded that this is true. OC -LUMORC1 The value is -LUMO U2 and-LUMO U3 The difference with LUMO U3 -LUMO U2 ΔE U2-U3 This corresponds to LUMO. RC1 -LUMO RC2 The value is -LUMO U1 and-LUMO U2 The difference with LUMO U2 -LUMO U1 ΔE U1-U2 This corresponds to -LUMO U1 and-LUMO U3 The difference with LUMO U3 -LUMO U1 ΔE U1-U3 ΔE U1-U2 and ΔE U2-U3 This corresponds to the sum of the two. By comparing the magnitudes of the lowest unaired orbital levels of each structural unit identified by some evaluation method, the above-mentioned "-LUMO U1 >-LUMO U2 >-LUMO U3 You may also want to check the "relationship".

[0018] The number n1 of first structural units included in the first section is 1 or greater, and may be 2 or greater, 3 or greater, or even 4 or greater. The upper limit of n1 is, for example, 5 or less, and may be 4 or less, 3 or less, or even 2 or less.

[0019] The number n2 of the second structural units included in the second section is 1 or greater, and may be 2 or greater, 3 or greater, or even 4 or greater. The upper limit of n1 is, for example, 5 or less, and may be 4 or less, 3 or less, or even 2 or less.

[0020] The ratio n2 / n1 of the number of second structural units in the second section to the number of first structural units n1 in the first section may be between 1 and 3, or between 1.5 and 3.

[0021] The number n3 of third structural units included in the third section is 1 or greater, and may be 2 or greater, 3 or greater, or even 4 or greater. The upper limit of n3 is, for example, 5 or less, and may be 4 or less, 3 or less, or even 2 or less.

[0022] The ratio n2 / n3, which is the number of second structural units n2 in the second section to the number of third structural units n3 in the third section, may be between 1.6 and 3, or between 2 and 3.

[0023] n1, n2, n3, the ratio n2 / n1, and the ratio n3 / n1 can take any combination of the numerical ranges exemplified above. For example, the ratio n2 / n1 of the number of second structural units n2 in the second section to the number of first structural units n1 in the first section may be 1 or more and 3 or less, and the number of third structural units in the third section may be 1 or 2.

[0024] LUMO U1 and LUMO U3 The absolute value of the difference (ΔE above) U1-U3 The value (corresponding to ) may be 0.10 eV or greater, 0.15 eV or greater, or even 0.17 eV or greater. The upper limit of the absolute value of this difference is, for example, 0.81 eV or less. Organic compound A whose absolute value of this difference falls within the above range is particularly suitable for use as a photocatalyst.

[0025] LUMO U1 and LUMO U2 The absolute value of the difference (ΔE above) U1-U2 The value (corresponding to ) may be between 0.01 eV and 0.70 eV, or between 0.01 eV and 0.68 eV. Organic compound A whose absolute value of the difference falls within the above range is particularly suitable for use as a photocatalyst.

[0026] LUMO U2 and LUMO U3 The absolute value of the difference (ΔE above) U2-U3The value (corresponding to ) may be between 0.05 eV and 0.55 eV, or between 0.05 eV and 0.51 eV. Organic compound A whose absolute value of the difference falls within the above range is particularly suitable for use as a photocatalyst.

[0027] LUMO U1 and LUMO U2 The absolute value of the difference between is LUMO U2 and LUMO U3 It may be greater than or equal to the absolute value of the difference between the two, and LUMO U2 and LUMO U3 It may be greater than the absolute value of the difference between the two. LUMO U1 and LUMO U2 The absolute value of the difference, and LUMO U2 and LUMO U3 Organic compound A whose absolute difference from the above relationship is particularly suitable for use as a photocatalyst.

[0028] LUMO U1 and LUMO U3 Let X (in eV) be the absolute value of the difference between the two, and let n (n = n² / n³) be the number of second structural units in the second section relative to the number of third structural units in the third section. Then the ratio X / n may be between 0.08 eV and 0.43 eV. According to our research, having the ratio X / n within the above range may be particularly suitable for preventing excessive separation between the first section and the third section, thereby suppressing charge recombination while transporting excited electrons to the third section.

[0029] The first, second, and third structural units are typically units formed by the polymerization of aromatic compounds. The aromatic compounds may be aromatic hydrocarbons or heterocyclic compounds. At least one structural unit selected from the group consisting of the first, second, and third structural units may be a unit formed by the polymerization of aromatic hydrocarbons or a unit formed by the polymerization of a heterocyclic compound. The heteroatoms contained in the heterocyclic compound are, for example, nitrogen atoms, sulfur atoms, and oxygen atoms, and may be at least one selected from the group consisting of nitrogen atoms and sulfur atoms.

[0030] The first, second, and third structural units typically have a skeleton containing aromatic rings. Each structural unit is typically bonded to an adjacent structural unit via carbon atoms or complex atoms, preferably carbon atoms, that make up the skeleton. The skeleton may contain two or more aromatic rings. In other words, at least one structural unit selected from the group consisting of the first, second, and third structural units may have a skeleton containing two or more aromatic rings.

[0031] Two or more aromatic rings included in the skeleton may form a fused ring. In other words, at least one structural unit selected from the group consisting of a first structural unit, a second structural unit, and a third structural unit may have a skeleton containing a fused aromatic ring. The number of rings constituting the fused aromatic ring may be, for example, 2 to 5, 2 to 4, or even 3 to 4. The aromatic rings may include heterocycles. At least one of the two or more aromatic rings may be a heterocycle.

[0032] The condensed ring included in the skeleton may be a hydrocarbon ring. In other words, at least one structural unit selected from the group consisting of a first structural unit, a second structural unit, and a third structural unit may have a condensed polycyclic hydrocarbon skeleton.

[0033] The fused rings included in the skeleton may also be peri-fused rings.

[0034] Aromatic rings in the skeleton may have substituents attached. Examples of substituents include alkyl groups, alkoxy groups, aryl groups, amino groups, hydroxyl groups, and halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, etc.). However, substituents are not limited to the above examples. The number of carbon atoms in alkyl groups and alkoxy groups may be, for example, 1 to 20, and may be 15 or less, or even 10 or less. The alkyl portion of alkyl groups and alkoxy groups may be linear, branched, or cyclic. Examples of aryl groups include phenyl groups, alkylphenyl groups, alkoxyphenyl groups, aminophenyl groups, and halogenated phenyl groups.

[0035] The first structural unit has, for example, a carbazole skeleton, a condensed polycyclic hydrocarbon skeleton, a thiophene skeleton, or a dibenzothiophene skeleton. Examples of condensed polycyclic hydrocarbon skeletons are fluorene skeletons, pyrene skeletons, phenanthrene skeletons, anthracene skeletons, naphthalene skeletons, and benzene skeletons. The condensed polycyclic hydrocarbon skeleton may also be a pericondensed polycyclic hydrocarbon skeleton. The dibenzothiophene skeleton includes a dibenzothiophene oxide skeleton. The first structural unit may have a carbazole skeleton, a fluorene skeleton, a pyrene skeleton, or a dibenzothiophene skeleton. Examples of the first structural unit having a carbazole skeleton are carbazole units, 9-phenylcarbazole units, and 9-alkylcarbazole units. The first structural unit having a condensed polycyclic hydrocarbon skeleton may be a fluorene unit, a 9,9-dialkylfluorene unit, a pyrene unit, a phenanthrene unit, anthracene unit, a naphthalene unit, or a phenyl unit. The first structural unit having a thiophene skeleton may also be a thiophene unit. The first structural unit having a dibenzothiophene skeleton may be a dibenzothiophene unit or a dibenzothiophene oxide unit. A more specific example of a dibenzothiophene oxide unit is the dibenzothiophene-5,5-dioxide unit. The first structural unit having a carbazole skeleton may be bonded to an adjacent structural unit with the carbon atoms at positions 2 and 7 of the skeleton as bonding sites. However, the positions of the bonding sites in each skeleton, including the carbazole skeleton, are not limited. Furthermore, the first structural unit is not limited to the above examples.

[0036] The second structural unit has, for example, a condensed polycyclic hydrocarbon skeleton, a thiophene skeleton, or a dibenzothiophene skeleton. Examples of the condensed polycyclic hydrocarbon skeleton are the same as those described above in the description of the first structural unit. The condensed polycyclic hydrocarbon skeleton may also be a pericondensed polycyclic hydrocarbon skeleton. The dibenzothiophene skeleton includes the dibenzothiophene oxide skeleton. The second structural unit may have a fluorene skeleton, a pyrene skeleton, or a dibenzothiophene skeleton. Examples of the second structural unit having a fluorene skeleton are the 9,9-dimethylfluorene unit, the 9,9-dialkylfluorene unit, and the fluorenone unit. An example of the second structural unit having a thiophene skeleton is the thiophene unit. Examples of the second structural unit having a dibenzothiophene skeleton are the dibenzothiophene unit and the dibenzothiophene oxide unit. A more specific example of the dibenzothiophene oxide unit is the dibenzothiophene-5,5-dioxide unit. The second structural unit may be a 9,9-dialkylfluorene unit, a pyrene unit, a phenanthrene unit, an anthracene unit, a naphthalene unit, or a phenyl unit. A second structural unit having a fluorene skeleton may be bonded to an adjacent structural unit with the carbon atoms at positions 2 and 7 of the skeleton as bonding sites. A second structural unit having a thiophene skeleton may be bonded to an adjacent structural unit with the carbon atoms at positions 3 and 3' of the skeleton as bonding sites. A second structural unit having a dibenzothiophene skeleton may be bonded to an adjacent structural unit with the carbon atoms at positions 3 and 7 of the skeleton as bonding sites. A second structural unit having a pyrene skeleton may be bonded to an adjacent structural unit with the carbon atoms at positions 2 and 7 of the skeleton as bonding sites. However, the positions of the bonding sites in each skeleton are not limited, including in the examples described above. Furthermore, the second structural unit is not limited to the examples described above.

[0037] The third structural unit may have, for example, an aromatic diimine skeleton, an aromatic triimine skeleton, or a porphyrin skeleton. Examples of aromatic diimine skeletons are bipyridine, phenanthroline, and bipyrimidine skeletons. Examples of third structural units having an aromatic diimine skeleton are the 2,2'-bipyridine unit, the 1,10-phenanthroline unit, and the 2,2-bipyrimidine unit. An example of an aromatic triimine skeleton is the terpyridine skeleton. An example of a third structural unit having a terpyridine skeleton is the 2,2':6',2''-terpyridine unit. Examples of third structural units having a porphyrin skeleton are the porphyrin unit and the tetraphenylporphyrin unit. A third structural unit having a bipyridine skeleton may be bonded to an adjacent structural unit using the carbon atoms at positions 5 and 5' of the skeleton as bonding sites. However, the positions of the bonding sites in each skeleton are not limited, including in the examples described above. Furthermore, the third structural unit is not limited to the examples described above.

[0038] The examples of the first, second, and third structural units described above can be combined in any way, as long as the energy levels of the lowest unoccupied orbits of each structural unit decrease in the order of the first structural unit, the second structural unit, and the third structural unit.

[0039] The third structural unit may have a structure in which a metal atom, or a group of atoms containing a metal atom, is coordinately bonded to an organic skeleton. According to the inventors' studies, the fact that the third structural unit has such a structure is related to the LUMO of the third structural unit. U3 , and the LUMO of organic compound A OC This may contribute to a decrease in [the specified value]. Furthermore, the third structural unit having the above structure can also be viewed as a site of a metal complex with an organic skeleton as a ligand.

[0040] The LUMO level of organic compound A, in which a third structural unit is a structure in which a metal atom or a group of atoms containing a metal atom is coordinately bonded to an organic skeleton, may be 0.12 eV or more lower, 0.23 eV or more, or even 0.30 eV or more lower than the LUMO level of organic compound A having the same structure except that the third structural unit does not have said structure. There is no particular upper limit to the amount of reduction, for example, 0.36 eV or less.

[0041] The metal atom may be at least one selected from the group consisting of ruthenium (Ru), rhenium (Re), platinum (Pt), iridium (Ir), rhodium (Rh), palladium (Pd), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and silver (Ag). When organic compound A is used as a photocatalyst, the metal atom may be selected depending on the reaction to be applied. The metal atom is not limited to the above examples.

[0042] Examples of organic skeletons are the same as examples of skeletons that the third structural unit may contain. The organic skeleton may also be an aromatic diimine skeleton. Examples of aromatic diimine skeletons are the same as those described above in the explanation of the third structural unit.

[0043] Examples of atomic groups that can coordinate bond to an organic skeleton are M(CO)2Cl2, M(CO)(Sol)Cl2, M(CO)3Br, MCl4, M(CO)3Cl, and M(PPh3)2(CO)2, where M represents the metal atom. The atomic groups may also be Ru(CO)2Cl2, Re(CO)3Br, or PtCl4. "Sol" refers to a solvent molecule, and "PPh3" refers to triphenylphosphine. An example of a solvent molecule is acetonitrile.

[0044] <1-2. Manufacturing method> Organic compound A can be produced, for example, by carrying out a polymerization reaction on a system containing a first compound that can form a first structural unit by polymerization, a second compound that can form a second structural unit by polymerization, and a third compound that can form a third structural unit by polymerization. The polymerization reaction may also be carried out by applying a coupling reaction to the above compound. Examples of applicable coupling reactions include the Suzuki-Miyaura coupling, the Mizorogi-Heck reaction, the Yamamoto polymerization, the Negishi coupling, the Migita-Kosugi-Still coupling, the Sonogashira coupling, and the Hiyama coupling. The conditions for the coupling reaction can be those known for the applicable coupling reaction.

[0045] A catalyst may be used to facilitate the polymerization reaction. When the polymerization reaction is carried out by a coupling reaction, a catalyst corresponding to the coupling reaction can be selected.

[0046] The method for producing organic compound A is not limited to the above example.

[0047] <1-3.Applications> Organic compound A may be used as a photocatalyst. In other words, organic compound A may be used as a photocatalyst.

[0048] Organic compound A may be used in combination with metal particles or metal compound particles. Depending on the type of metal particles and metal compound particles, a mixture of these particles and organic compound A, or a modified form of these particles modified with organic compound A, may be used as a photocatalyst. Organic compound A may also be used to modify metal particles or metal compound particles.

[0049] Examples of metal particles that may be used as photocatalysts in combination with organic compound A include ruthenium (Ru) particles, platinum (Pt) particles, iridium (Ir) particles, rhodium (Rh) particles, palladium (Pd) particles, iron (Fe) particles, cobalt (Co) particles, nickel (Ni) particles, copper (Cu) particles, and silver (Ag) particles.

[0050] Examples of the metal compound that constitutes the metal compound particles include metal oxides, metal nitrides, metal oxynitrides, metal sulfides, and metal phosphates. Examples of the metal contained in the metal compound are the same as those of the metal atoms described above in the description of the third structural unit. Examples of metal compound particles that may be used as a photocatalyst in combination with the organic compound A include iridium oxide (IrO x , for example, IrO2) particles, cobalt oxide (CoO x ) particles, cobalt phosphate (CoPi) particles, ruthenium oxide (RuO x , for example, RuO2) particles, iron oxide (FeO x ) particles, iron nickel oxide particles (FeNiO x ), and iron cobalt oxide (FeCoO x ) particles.

[0051] The metal particles and the metal compound particles may be nanoparticles having an average particle diameter of less than 1 μm. The average particle diameter can be specified by the median diameter (d50). The particles may be colloidal particles. Examples of more specific combinations are the combination of the organic compound A and Pt nanoparticles, and the combination of the organic compound A and IrO x colloidal particles. For specifying the median diameter, for example, a particle size distribution measuring device such as a laser diffraction type can be used.

[0052] The organic compound A may be used in combination with metal ions. According to the studies of the present inventors, in the function as a photocatalyst in the combination, the modification of the metal ions to the second section and / or the third section of the organic compound A, particularly the third section, may further contribute. For example, a mechanism in which the metal ions that have received the excited electrons generated in the organic compound A act as the active sites (active centers) of the reaction can be considered.

[0053] The metal ions may be ions of the first transition metals. Examples of the first transition metals are copper (Cu), iron (Fe), manganese (Mn), cobalt (Co), and nickel (Ni). The valence of the ions is not limited, but typically it is divalent. The metal ions are Cu 2+ , Fe 2+ , Mn2+ 、Co 2+ and Ni 2+ may be at least one selected from the group consisting of.

[0054] When combined with metal ions, an auxiliary ligand may be further added. In other words, the organic compound A may be used in combination with metal ions and an auxiliary ligand. An example of the auxiliary ligand is 2,2’:6’,2’’-terpyridine. An example of the combination of metal ions and an auxiliary ligand is Fe 2+ and 2,2’:6’,2’’-terpyridine.

[0055] The photocatalyst using the organic compound A may be applied to a reduction reaction or an oxidation reaction. The enhanced charge separation between the first section and the third section can contribute to the promotion of both the reduction reaction and the oxidation reaction.

[0056] Examples of the reduction reaction are the reduction reaction of CO2, the reduction reaction of water, and the reduction reaction of protons. An example of the oxidation reaction is the oxidation reaction of water. However, the reduction reaction and the oxidation reaction are not limited to the above examples.

[0057] An example of the organic compound A particularly suitable for the photocatalyst for the reduction reaction of CO2 is that the first structural unit has a carbazole skeleton, the second structural unit has a fluorene skeleton, a pyrene skeleton or a dibenzothiophene skeleton, preferably a dibenzothiophene skeleton, the third structural unit has a bipyridine skeleton, and an atomic group containing Ru or Re is coordinated to the bipyridine skeleton. The second structural unit having a dibenzothiophene skeleton may be a dibenzothiophene oxide unit. According to the study of the present inventors, Ru is more suitable for the production of formic acid by the reduction of CO2, and Re is more suitable for the production of carbon monoxide (CO) by the reduction of CO2.

[0058] An example of the combination of the organic compound A particularly suitable for the photocatalyst for the reduction reaction of CO2 and metal ions is the combination of the organic compound A and divalent copper ions (Cu 2+ ) and the combination of the organic compound A and divalent iron ions (Fe2+ ) in combination with organic compound A and divalent manganese ions (Mn 2+ ) and combinations with organic compound A and divalent cobalt ions (Co 2+ This is a combination of organic compound A and Cu. 2+ The combination of, and organic compound A and Fe 2+ A combination of organic compound A and Fe is preferred. 2+ The combination with is particularly preferred. In this case, organic compound A may be a compound in which the first structural unit has a carbazole skeleton, a fluorene skeleton, a pyrene skeleton, or a dibenzothiophene skeleton, the second structural unit has a dibenzothiophene oxide skeleton, and the third structural unit has a bipyridine skeleton. According to the inventors' studies, organic compound A and Cu 2+ The combination of, and organic compound A and Fe 2+ The combination is more suitable for the production of formic acid by the reduction of CO2, and organic compound A and Fe 2+ This combination is also more suitable for generating CO through the reduction of CO2.

[0059] An example of an organic compound A particularly suitable as a photocatalyst for the reduction reaction of water is an organic compound A having a carbazole skeleton as its first structural unit, a fluorene skeleton, a pyrene skeleton, or a dibenzothiophene skeleton, preferably a dibenzothiophene skeleton, as its second structural unit, and a bipyridine skeleton as its third structural unit. The second structural unit having a dibenzothiophene skeleton may also be a dibenzothiophene oxide unit. An embodiment combining the organic compound A with Pt nanoparticles is preferably used. Typically, hydrogen is produced by the reduction of water.

[0060] An example of a combination of organic compound A and metal ions particularly suitable as a photocatalyst for proton reduction reactions is organic compound A and Cu 2+ In combination with, organic compound A and Fe 2+ In combination with organic compound A and Mn 2+ The combination of, and organic compound A and Co 2+ This is a combination of organic compound A and Cu 2+The combination of, and organic compound A and Mn 2+ A combination of organic compound A and Cu is preferred. 2+ The combination with is particularly preferred. In this case, organic compound A may be a compound in which the first structural unit has a carbazole skeleton, a fluorene skeleton, a pyrene skeleton, or a dibenzothiophene skeleton, the second structural unit has a dibenzothiophene oxide skeleton, and the third structural unit has a bipyridine skeleton. Hydrogen is usually produced by the reduction of protons.

[0061] An example of an organic compound A particularly suitable as a photocatalyst for the oxidation reaction of water is an organic compound A having a carbazole skeleton as its first structural unit, a fluorene skeleton, a pyrene skeleton, or a dibenzothiophene skeleton, preferably a dibenzothiophene skeleton, as its second structural unit, and a bipyridine skeleton as its third structural unit. The second structural unit having a dibenzothiophene skeleton may also be a dibenzothiophene oxide unit. A combination of the organic compound A and IrO2 colloid is preferably used. Typically, oxygen is produced by the oxidation of water.

[0062] Organic compound A is not limited to the above examples and can be used for various applications. Organic compound A may be used as an organic material containing organic compound A. In other words, the organic material according to the embodiments of the present invention may contain organic compound A.

[0063] <<2. Photocatalyst>> The photocatalyst according to an embodiment of the present invention (hereinafter referred to as "photocatalyst C") contains organic compound A. As described above, organic compound A is suitable for use in photocatalysts.

[0064] The photocatalyst C may be in the form of parts or thin films, for example. However, the shape of the photocatalyst C is not limited to the above examples. The photocatalyst C can have any shape.

[0065] The average particle size of the particulate photocatalyst C is, for example, 1 nm to 100 μm, but may also be 2 nm to 50 μm, 5 nm to 25 μm, 10 nm to 20 μm, 25 nm to 15 μm, 50 nm to 10 μm, or even 100 nm to 5 μm. The average particle size can be determined by the median diameter (d50). For determining the median diameter, a particle size distribution analyzer, such as a laser diffraction analyzer, can be used.

[0066] Photocatalyst C may contain materials other than organic compound A. Examples of materials include metal particles and metal compound particles. In other words, photocatalyst C may further contain metal particles or metal compound particles. Another example of materials is metal ions and auxiliary ligands. In other words, photocatalyst C may further contain metal ions, or further contain metal ions and auxiliary ligands. Photocatalyst C may contain at least one selected from the group consisting of metal particles, metal compound particles, metal ions, and auxiliary ligands.

[0067] The metal particles and metal compound particles may be particles that have catalytic activity for the chemical reaction to which photocatalyst C is applied. Examples of such metal particles and metal compound particles are the same as those described above in the explanation of the uses of organic compound A.

[0068] The content of metal particles or metal compound particles in photocatalyst C is, for example, 0.05 to 10% by weight. The lower limit of the content may be 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, or even 0.7% by weight or more. The upper limit of the content may be 8% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, or even 2% by weight or less.

[0069] The example of metal ions is the same as the example described above in the explanation of the uses of organic compound A.

[0070] The content of metal ions in photocatalyst C containing metal ions is, for example, 1 mol% or more, based on the molar amount of the third section of all organic compound A contained in photocatalyst C, and may be 5 mol% or more, 10 mol% or more, 25 mol% or more, 50 mol% or more, 75 mol% or more, 80 mol% or more, 90 mol% or more, 100 mol% or more, 125 mol% or more, and even 150 mol% or more. The upper limit of the content is not limited as long as the function of photocatalyst C is obtained, and may be, for example, 500 mol% or less, 300 mol% or less, 250 mol% or less, and even 200 mol% or less.

[0071] The example of the auxiliary ligand is the same as the example described above in the explanation of the uses of organic compound A.

[0072] Photocatalyst C may be used for the reduction reaction of CO2, water, or protons, or for the oxidation reaction of water. Photocatalyst C applied to the reduction reaction of CO2 may contain organic compound A, which is particularly suitable for the photocatalyst for the reduction reaction of CO2, as described above, or it may be a combination of organic compound A, which is particularly suitable for the photocatalyst for the reduction reaction of CO2, and a metal ion. Photocatalyst C applied to the reduction reaction of water may contain organic compound A, which is particularly suitable for the photocatalyst for the reduction reaction of water, as described above. Photocatalyst C applied to the reduction reaction of protons may contain organic compound A, which is particularly suitable for the photocatalyst for the reduction reaction of protons, as described above, or it may be a combination of organic compound A, which is particularly suitable for the photocatalyst for the reduction reaction of protons, and a metal ion. Photocatalyst C applied to the oxidation reaction of water may contain organic compound A, which is particularly suitable for the photocatalyst for the oxidation reaction of water, as described above.

[0073] The chemical reactions to which photocatalyst C is applied are not limited to the examples above.

[0074] The CO2 reduction reaction using photocatalyst C can be carried out, for example, by supplying CO2 to a dispersion containing particles of organic compound A and irradiating it with light. Alternatively, the CO2 reduction reaction using photocatalyst C may be carried out, for example, by supplying CO2 to a solution containing dispersed particles of organic compound A and dissolved metal ions, and irradiating it with light.

[0075] The water reduction reaction using photocatalyst C can be carried out, for example, by irradiating a dispersion (containing water) in which particles of organic compound A are dispersed with light. The dispersion may also contain metal particles or metal compound particles.

[0076] The proton reduction reaction using photocatalyst C can be carried out, for example, by irradiating a dispersion containing particles of organic compound A (provided to contain a proton source) with light. The dispersion may also contain metal particles or metal compound particles. Alternatively, the proton reduction reaction using photocatalyst C can be carried out, for example, by irradiating a solution containing particles of organic compound A and dissolved metal ions (provided to contain a proton source) with light.

[0077] The oxidation reaction of water using photocatalyst C can be carried out, for example, by irradiating a dispersion (containing water) in which particles of organic compound A are dispersed with light. The dispersion may also contain metal particles or metal compound particles. Alternatively, the oxidation reaction of water using photocatalyst C can be carried out, for example, by irradiating a solution (containing water) in which particles of organic compound A are dispersed and metal ions are dissolved with light. Whether to proceed with reduction or oxidation of water may be determined by selecting the type of metal particles or metal compound particles, or by selecting the type and amount of metal ions.

[0078] The light irradiated onto the chemical reaction system to which photocatalyst C is applied is, for example, light including visible light. The irradiated light may include light with a wavelength of 400 nm or more. The irradiated light may include at least one light selected from the group consisting of light with wavelengths of 420 nm or more, 440 nm or more, 450 nm or more, 470 nm or more, 490 nm or more, 500 nm or more, 520 nm or more, 540 nm or more, and 550 nm or more. The irradiated light may be sunlight, or light from which ultraviolet and / or infrared rays have been removed. In this specification, visible light means light with a wavelength in the range of 400 to 800 nm. Ultraviolet light means light with a wavelength in the range of less than 400 nm. Infrared light means light with a wavelength in the range of more than 800 nm. The light source can be arbitrarily selected.

[0079] Other materials may be used in combination with photocatalyst C. An example of such other material is a sacrificial agent. A sacrificial agent is a material that acts as an electron donor (or electron acceptor) to the reduction (or oxidation) reaction by photocatalyst C, thereby contributing to the acceleration of the reduction (or oxidation) reaction. Examples of sacrificial agents that can act as electron donors include triethanolamine, disodium ethylenediaminetetraacetate, ascorbic acid, 1-benzyl-1,4-dihydronicotinamide, and benzimidazole derivatives. Examples of sacrificial agents that can act as electron acceptors include sodium peroxodisulfate, silver nitrate, iron(III) chloride, iron(III) nitrate, iron(III) sulfate, sodium iodate, potassium iodate, and potassium hexacyanoferrate(III). However, the sacrificial agent is not limited to the above examples.

[0080] When a sacrificial agent is used in combination, the amount used is expressed by its concentration in the dispersion, for example, 0.1 mmol / L to 1 mol / L, or 1 mmol / L to 100 mmol / L. [Examples]

[0081] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the specific embodiments shown below.

[0082] <<Evaluation Method>> First, we will explain the evaluation method for the organic compounds prepared in the examples.

[0083] <Mass spectrometry> The mass distribution of organic compounds was evaluated using a matrix-assisted laser desorption / ionization mass spectrometer (Shimadzu, MALDI-8020).

[0084] <Infrared Spectroscopy> The infrared light absorption characteristics of organic compounds were evaluated using an infrared spectrophotometer (JASCO, FT / IR-4200).

[0085] <Energy Levels> The energy levels of organic compounds are determined by their ionization energy (E ion ) and visible light absorption edge (λ edge The values ​​were evaluated by estimation from the following: The visible light absorption edge of the organic compounds was evaluated using a UV-Vis spectrophotometer (Shimadzu, UV-2600i). The ionization energy of the organic compounds was evaluated using a photoelectron yield spectrometer (Bunko-keiki, BIP-KV201). The HOMO-LUMO energy gap (eV) of the organic compounds is given by the formula: energy gap (eV) = 1240 / λ edge The HOMO energy of an organic compound relative to the vacuum level is calculated using the ionization energy (E ion ) was assumed to be equal to . The HOMO potential of an organic compound relative to the standard hydrogen electrode (NHE) is given by the formula: HOMO potential (V) = E ion Calculated using -4.44 (see J.Phys.Chem.B 2003, 107, 1798). The LUMO potential of organic compounds relative to the standard hydrogen electrode (NHE) is given by the formula: LUMO potential (V) = E ion -4.44-1240 / λ edge It was calculated using the method described below.

[0086] <Photocatalytic activity> The photocatalytic activity of organic compounds was evaluated based on their CO2 reduction ability, hydrogen production ability from water, and oxygen production ability from water.

[0087] [CO2 reduction ability] The CO2 reducing ability of organic compounds was evaluated by a photocatalytic reaction using triethanolamine as an electron donor. The evaluation was carried out as follows: First, 2 mg of particles of the organic compound to be evaluated and 2 mL of acetonitrile-triethanolamine mixed solvent (volume ratio 4:1) were placed in a Pyrex® test tube, and the organic compound particles were dispersed in the mixed solvent by ultrasonic irradiation using an ultrasonic cleaner. Next, CO2 gas at 1 atmosphere was passed through the resulting dispersion for 20 minutes, and then the test tube was sealed with a rubber septum. Next, visible light was irradiated onto the dispersion in the test tube. For visible light irradiation, an LED merry-go-round light irradiation device (Cell System, Iris-S) was used. This device makes it possible to irradiate the entire workpiece with a uniform amount of visible light. For visible light irradiation, five types of LEDs with central wavelengths of 430 nm, 470 nm, 530 nm, 590 nm, and 650 nm, provided by the device, were used. Visible light irradiation was performed at room temperature (25°C) for 3 hours. The amount of formic acid produced by light irradiation was analyzed by liquid chromatography (Shimadzu, CDD-10A conductivity detector). The amount of gas produced by light irradiation was analyzed by gas chromatography (GL-Science, GC2010). A thermal conductivity type (TCD) detector was used for the gas chromatography, a molecular sieve 5A was used for the column, and argon was used as the carrier gas.

[0088] [Hydrogen generation capacity] The hydrogen-generating ability of organic compounds modified with Pt nanoparticles was evaluated by a photocatalytic reaction using disodium ethylenediaminetetraacetate as an electron donor, which was carried out simultaneously with the generation of Pt nanoparticles. The evaluation was performed as follows: First, 2 mg of particles of the organic compound to be evaluated (before modification), a 0.021 mg / mL H2PtCl6 solution (equivalent to 1% by weight of Pt relative to the organic compound), and 2 mL of a 0.1 mol / L aqueous solution of disodium ethylenediaminetetraacetate were placed in a Pyrex® test tube, and the organic compound particles were dispersed by ultrasonic irradiation using an ultrasonic cleaner. Next, argon gas at 1 atmosphere was passed through the resulting dispersion at a flow rate of 50 mL / min for 20 minutes, and then the test tube was sealed with a rubber septum. Next, while stirring the contents of the test tube with a magnetic stirrer, visible light was irradiated onto the dispersion in the test tube. An LED merry-go-round light irradiation device (Cell System, Iris-S) was used for visible light irradiation. For visible light irradiation, six types of LEDs with central wavelengths of 405 nm, 430 nm, 470 nm, 530 nm, 590 nm, and 650 nm, provided by the device, were used. Visible light irradiation was carried out at room temperature for 12 hours. The hydrogen generated by the light irradiation and its amount were identified and analyzed using the same gas chromatograph used to evaluate the CO2 reduction capacity.

[0089] [Oxygen production ability] The oxygen-producing capacity of organic compounds was evaluated by a photocatalytic reaction using sodium peroxodisulfate as an electron acceptor. The evaluation was carried out as follows: First, 5 mg of particles of the organic compound to be evaluated and 5 mL of a 10 mmol / L aqueous solution of sodium peroxodisulfate were placed in a Pyrex® test tube, and the organic compound particles were dispersed by ultrasonic irradiation using an ultrasonic cleaner. Next, argon gas at 1 atmosphere was passed through the resulting dispersion for 20 minutes, and the test tube was sealed with a silicon / polytetrafluoroethylene septum. Next, visible light was irradiated onto the dispersion in the test tube. An LED light source (Asahi Spectra, center wavelength 430 nm) was used for visible light irradiation. Visible light irradiation was carried out at room temperature for 1 hour, with an irradiation intensity of 0.2 W. The amount of oxygen produced by the light irradiation was analyzed using an oxygen sensor (FireSting O2-C, Pyroscience).

[0090] <<Preparation of Organic Compounds>> <Manufacturing Example 1> The organic compound in Production Example 1 was prepared as follows. From this point forward, part B of the prepared organic compound will be referred to as D. x -S y -A z or D x -S y -AM z The notation is as follows: D, S, and A correspond to the first section, the second section, and the third section, respectively. D, S, and A are abbreviations for the first structural unit, the second structural unit, and the third structural unit, respectively. However, for the third structural unit having a structure in which a group of atoms containing metal atoms are coordinately bonded to an organic skeleton, it is written as AM, with A being the abbreviation for the organic skeleton and M being the element symbol for the metal atom. x, y, and z are all natural numbers and represent the number of first structural units contained in the first section of part B, the number of second structural units contained in the second section, and the number of third structural units contained in the third section, respectively.

[0091] The abbreviations are as follows: Cz: Carbazole skeleton Ful: Fluorene skeleton Dbt: ​​Dibenzothiophene skeleton DbtO: Dibenzothiophene oxide skeleton Py: Pyrene skeleton BPy: Bipyridine skeleton

[0092] [Preparation of organic compounds containing D1-S2-Bpy1] 0.25 mmol of 2,7-dibromo-9-phenylcarbazole, 0.5 mmol of 3,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)dibenzo[b,d]thiophene-5,5-dioxide, and 0.25 mmol of 5,5'-dibromo-2,2'-bipyridine were added to a mixed solvent containing 0.01 mmol of tetrakis(triphenylphosphine)palladium (Pd(PPh3)4), 3.75 mmol of K2CO3, 2 mL of water, and 10 mL of N,N'-dimethylformamide. The resulting mixture was then refluxed at 150°C for 2 days under a nitrogen atmosphere. After adding 20 mL of water to the suspension produced by reflux, the mixture was filtered, and the resulting filtrate was washed with 20 mL of methanol. The powder obtained by washing was vacuum-dried at room temperature to obtain a powdered organic compound containing Cz1-DbtO2-Bpy1.

[0093] In the same manner as described above, five more organic compounds containing the respective parts of Cz1-Ful2-Bpy1, Cz1-Py2-Bpy1, Ful1-DbtO2-Bpy1, Dbt1-DbtO2-Bpy1, or Py1-DbtO2-Bpy1 were prepared. 2,7-dibromo-9,9-dimethylfluorene was used as the starting material for Ful introduced into part D (first section). 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-dimethylfluorene was used as the starting material for Ful introduced into part S (second section). 3,7-dibromodibenzo[b,d]thiophene was used as the starting material for Dbt. 2,7-dibromopyrene was used as the starting material for Py.

[0094] [Cz x -DbtOy -Bpy z [Vehicles containing organic compounds] x / (x+y+z)mmol 9-phenyl-2,7(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole, 0.5×(-x+y+z) / (x+y+z)mmol 3,7-dibromodibenzothiophene-5,5-dioxide, 0.5×(x+yz) / (x+y+z)mmol 3,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)dibenzo[ Except for using [b,d]thiophene-5,5-dioxide and z / (x+y+z)mmol 5,5'-dibromo-2,2'-bipyridine as starting materials, five organic compounds containing the respective parts of Cz1-DbtO3-Bpy1, Cz2-DbtO2-Bpy1, Cz2-DbtO3-Bpy1, Cz2-DbtO5-Bpy3, or Cz3-DbtO5-Bpy2 were prepared in the same manner as for the preparation of the organic compounds containing D1-S2-Bpy1.

[0095] [Preparation of an Organic Compound as a Comparative Example 1] 0.25 mmol of 2,7-dibromo-9-phenylcarbazole and 0.25 mmol of 9-phenyl-2,7(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole were added to a mixed solvent containing 0.01 mmol of tetrakis(triphenylphosphine)palladium (Pd(PPh3)4), 3.75 mmol of K2CO3, 2 mL of water, and 10 mL of N,N'-dimethylformamide. The resulting mixture was refluxed at 150°C for 2 days under a nitrogen atmosphere. After adding 20 mL of water to the suspension produced by reflux, the mixture was filtered, and the resulting filtrate was washed with 20 mL of methanol. The powder obtained by washing was vacuum-dried at room temperature to obtain a powdered organic compound containing only the moiety denoted by Cz. The organic compound containing only the moiety denoted by Cz consists only of structural units having a carbazole skeleton.

[0096] In the same manner as described above, three more organic compounds were prepared, each containing only the portion represented by Ful, DbtO, or Py. For Ful, 2,7-dibromo-9,9-dimethylfluorene and 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-dimethylfluorene were used as starting materials. For DbtO, 3,7-dibromodibenzothiophene-5,5-dioxide and 3,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)dibenzo[b,d]thiophene-5,5-dioxide were used as starting materials. For Py, 2,7-dibromopyrene and 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyrene were used as starting materials. Organic compounds containing only the parts denoted as Ful, DbtO, or Py consist of only one corresponding structural unit.

[0097] [Comparative Example: Preparation of Organic Compounds 2] Except for using two types of raw materials and adjusting the amounts of the raw materials used, four types of organic compounds containing the Cz1-DbtO2, Ful1-DbtO2, Py1-DbtO2, and DbtO1-Bpy1 parts were prepared in the same manner as the preparation of organic compounds containing D1-S2-Bpy1. Each part consists of only two corresponding sections.

[0098] The only difference is that no raw materials forming the DbtO section are used, and the amount of raw materials used is adjusted. x -DbtO y -Bpy z Organic compounds containing the Cz1-Bpy1 moiety were prepared in the same manner as the preparation of organic compounds containing the moiety. This moiety consists of only two sections: a Cz section and a Bpy section.

[0099] [D x -S y -BpyM z Preparation of organic compounds containing (M=Ru) The powder of the organic compound containing Cz1-DbtO2-Bpy1, prepared by the method described above, is mixed with 1 equivalent of [Ru(CO)2Cl2]n The compound was added to 5 mL of methanol solution containing the compound to form a suspension. Next, the resulting suspension was refluxed at 70°C for 17 hours under a nitrogen atmosphere. The suspension produced by reflux was filtered, and the resulting filtrate was washed with 10 mL of methanol. The powder obtained by washing was vacuum-dried at room temperature to obtain a powdered organic compound containing Cz1-DbtO2-BpyRu1.

[0100] In addition to changing the organic compound used, [Ru(CO)2Cl2] n Eight different organic compounds were prepared in the same manner as the preparation of organic compounds containing Cz1-DbtO2-BpyRu1, except for adjusting the equivalent amounts of each component. These compounds contain either Cz1-Ful2-BpyRu1, Ful1-DbtO2-BpyRu1, Dbt1-DbtO2-BpyRu1, Cz1-DbtO3-BpyRu1, Cz2-DbtO2-BpyRu1, Cz2-DbtO3-BpyRu1, Cz2-DbtO5-BpyRu3, or Cz3-DbtO5-BpyRu2.

[0101] [Comparative Example: Preparation of Organic Compounds 3] The organic compound prepared in "Comparative Example: Preparation of Organic Compound 2" was used, along with [Ru(CO)2Cl2] n Except for adjusting the equivalent amounts of each component, two types of organic compounds containing either Cz1-BpyRu1 or DbtO1-BpyRu1 were prepared in the same manner as in the preparation of organic compounds containing Cz1-DbtO2-BpyRu1.

[0102] [D x -S y -BpyM z Preparation of organic compounds containing (M=Re) The powder of the organic compound containing Cz1-DbtO2-Bpy1, prepared by the method described above, was added to 5 mL of toluene solution containing 1 equivalent of Re(CO)5Br to form a suspension. Next, the resulting suspension was refluxed at 115°C for 17 hours under a nitrogen atmosphere. The suspension produced by reflux was filtered, and the resulting filtrate was washed with 10 mL of toluene. The powder obtained by washing was vacuum-dried at room temperature to prepare the organic compound containing Cz1-DbtO2-BpyRe1.

[0103] [D x -S y -BpyM z Preparation of organic compounds containing (M=Pt) The powder of the organic compound containing Cz1-DbtO2-Bpy1, prepared by the method described above, was added to 8.5 mL of hydrochloric acid aqueous solution containing 1 equivalent of H2PtCl4 to form a suspension. Next, the resulting suspension was reacted at 90°C for 24 hours under a nitrogen gas atmosphere. The suspension produced by the reaction was filtered, and the resulting filtrate was washed with 10 mL of water. The powder obtained by washing was vacuum-dried at room temperature to prepare the organic compound containing Cz1-DbtO2-BpyPt1.

[0104] <Manufacturing Example 2: Preparation of Organic Compounds Modified with Metal or Metal Oxide Nanoparticles> [Cz x -DbtO y -Bpy z [Preparation of organic compounds modified with Pt nanoparticles, including] Cz produced by the method described above x -DbtO y -Bpy zTwo mg of an organic compound containing H2PtCl6 was dispersed in two mL of a 0.1 mol / L aqueous solution of disodium ethylenediaminetetraacetate containing 0.021 mg / mL of H2PtCl6. The resulting dispersion was transferred to a Pyrex® test tube, aerated with Ar gas at a flow rate of 50 mL / min for 20 minutes, and then sealed with a rubber septum. Next, the test tube was irradiated with visible light at room temperature for 12 hours while stirring with a magnetic stirrer. An LED merry-go-round light irradiation device (Cell System, Iris-S) was used for visible light irradiation. Six types of LEDs with central wavelengths of 405 nm, 430 nm, 470 nm, 530 nm, 590 nm, and 650 nm, as provided by the device, were used for visible light irradiation. The hydrogen generated in response to light irradiation was quantified by gas chromatography, and the hydrogen generation activity of the organic compound modified with Pt nanoparticles was simultaneously evaluated. After visible light irradiation, the dispersion was filtered, washed with water, and then dried under reduced pressure at room temperature. This allowed us to create four types of organic compounds by modifying Pt nanoparticles, each containing one of the following moieties: Cz1-DbtO2-Bpy1, Cz2-DbtO3-Bpy1, Cz2-DbtO5-Bpy3, or Cz3-DbtO5-Bpy2.

[0105] [Preparation of an Organic Compound as a Comparative Example 4] Cz x -DbtO y -Bpy z Except for using an organic compound consisting solely of DbtO units prepared by the method described above, or an organic compound containing Cz1-Bpy1, instead of an organic compound containing Cz1, x -DbtO y -Bpy z Two types of organic compounds modified with Pt nanoparticles were prepared in the same manner as the preparation of organic compounds modified with Pt nanoparticles, each containing either DbtO or Cz1-Bpy1.

[0106] [Preparation of organic compounds containing Cz1-DbtO2-Bpy1, modified with IrO2 nanoparticles] An IrO2 colloidal solution was prepared according to a previously reported method (Maeda, K. et. al., Angew. Chem. Int. Ed. 2012, 51, 9865). Next, 9 mg of the organic compound containing Cz1-DbtO2-Bpy1, prepared by the method described above, was dispersed in 9 mL of an IrO2 colloidal solution with a concentration of 0.38 mg / mL. After stirring the dispersion for 1 hour, it was filtered, washed with water, and then dried under reduced pressure at room temperature to produce an organic compound containing Cz1-DbtO2-Bpy1 and modified with IrO2 nanoparticles.

[0107] [Comparative Example: Preparation of Organic Compounds 5] Except for using an organic compound composed solely of DbtO units prepared by the method described above, or an organic compound containing Cz1-Bpy1, instead of an organic compound containing Cz1-DbtO2-Bpy1, two types of organic compounds were prepared in the same manner as the preparation of organic compounds containing Cz1-DbtO2-Bpy1 and modified with IrO2 nanoparticles, each containing either DbtO or Cz1-Bpy1.

[0108] <Test Example 1> Mass spectroscopy analysis was performed on each of the organic compounds prepared as described above. From the spacing of the peaks in the obtained spectra, a periodic structure derived from the number and arrangement of each structural unit could be confirmed.

[0109] D x -S y -BpyM z Infrared absorption spectral analysis was performed on each organic compound containing BpyM. z Characteristic absorptions were observed in the carbonyl stretching vibrations of the complex moiety within the section. The observed absorptions were consistent with those previously reported for the isomorphic complex (BpyM complex).

[0110] Figure 2(A) shows the evaluation results of the visible absorption characteristics of several organic compounds containing Cz1-DbtO2-Bpy1, as well as several comparative organic compounds. As shown in Figure 2(A), all organic compounds containing Cz1-DbtO2-Bpy1 showed absorption in the visible light region above 400 nm. In some organic compounds, the absorption extended to wavelengths above 500 nm, and even above 550 nm. Furthermore, the absorption wavelength changed depending on the combination and ratio of the organic skeletons constituting each organic compound. Figures 2(A) and (B) show the diffuse reflectance spectra after KM (Kuberka-Munk) transformation, with wavelength on the horizontal axis.

[0111] Cz x -DbtO y -BpyM z Figure 2(B) shows the evaluation results of the visible absorption properties for several organic compounds containing Cz, as well as several comparative organic compounds. As shown in Figure 2(B), Cz x -DbtO y -BpyM z All organic compounds containing Cz1-DbtO2-Bpy1 showed absorption in the visible light region at wavelengths of 400 nm or higher. In some organic compounds, absorption extended to wavelengths of 500 nm or higher, and even beyond 550 nm. Furthermore, the absorption wavelengths were longer than those of organic compounds containing Cz1-DbtO2-Bpy1, and varied depending on the type of M molecule coordinated.

[0112] The highest occupied orbital level (HOMO) of each organic compound, estimated from the evaluation of visible absorption characteristics and ionization energy. OC ), the lowest orbital level (LUMO) OC ), and HOMO OC and LUMO OC The energy difference is shown in Tables 1A and 1B. By having a second section, compared to organic compounds consisting of the first and third sections, LUMO OC It was confirmed that it shifts to the positive side, in other words, decreases. Furthermore, in an organic compound having a first section, a second section, and a third section, by coordinating a metal atom to the third section, LUMO OCIt was confirmed that the level decreased even further compared to before coordination.

[0113] [Table 1A]

[0114] [Table 1B]

[0115] LUMO of several organic compounds OC Regarding the LUMO of a reference compound having the same structure except for the lack of only the third section, RC1 The amount of decrease (ΔE) U2-U3 ), and the LUMO of a reference compound having the same configuration except for lacking the second and third sections. RC2 The amount of decrease (ΔE) U1-U2 The following values ​​were calculated. Also, ΔE U1-U2 and ΔE U2-U3 For organic compounds where both values ​​are positive, ΔE U1-U2 and ΔE U2-U3 And, LUMO of organic compounds OC , LUMO of the reference compound RC1 and LUMO RC2 The correlation with this is shown in Figure 3.

[0116] [Table 2]

[0117] <Test Example 2: Photocatalytic Properties> [CO2 reduction ability] When the CO2 reduction ability of the organic compounds shown in Table 3 below was evaluated using the method described above, the organic compounds of Examples 1 to 10 produced formic acid as the main product upon irradiation with visible light, and the production rates were as shown in Table 3.

[0118] On the other hand, in the organic compound of Example 11, in which an atomic group containing Re was coordinated to the bipyridine skeleton, CO was selectively produced. Furthermore, in the organic compound of Example 12, in which an atomic group containing Pt was coordinated to the bipyridine skeleton, no reduction product of CO2 was obtained, and hydrogen was selectively produced. Since these reaction selectivityes are consistent with those previously reported for each metal complex, it was presumed that they reflect the catalytic properties of the metal complex.

[0119] [Table 3]

[0120] Cz x -DbtO y -BpyRu z In the organic compounds of Examples 1 and 6-10, significantly higher formic acid production activity was observed compared to Comparative Example 1, which had a similar structure except for the absence of the second section, and Comparative Example 2, which had a similar structure except for the absence of the first section. From this, it was inferred that the organic compound containing part B, which includes all of the first to third sections, is particularly suitable as a photocatalyst.

[0121] A comparison of the organic compounds in Examples 1 to 5, which differ in their combinations of the first and second structural units, revealed that Cz was particularly effective as the first structural unit for high activation, and DbtO was particularly effective as the second structural unit for high activation.

[0122] On the other hand, the organic compound of Comparative Example 3 exhibited activity almost equivalent to that of the organic compound of Comparative Example 1, which lacked a second section. As shown in Table 2, the LUMO level gradient ΔE from the first section to the second section of the organic compound of Comparative Example 3 was U1-U2 The value was slightly negative, suggesting that effective separation of excited electrons was not achieved.

[0123] The organic compound in Comparative Example 4, which included DbtO1-Cz2-BpyRu1 with the order of the first and second sections reversed, showed lower activity compared to all of the organic compounds in Examples 1 and 6-10. As shown in Table 2, DbtO1-Cz2-BpyRu1 has a LUMO level gradient ΔE from the first section to the second section. U1-U2 The value was negative. In DbtO1-Cz2-BpyRu1, it was presumed that the activity was lowered because the excitation electron transfer from the first section to the second section was inhibited compared to before the exchange.

[0124] When 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole was added at a concentration of 50 mM as a sacrificial reducing agent and irradiated with monochromatic light at 430 nm (4.0 mW), the reaction quantum yield for formic acid production of Cz2-DbtO3-BpyRu1 in Example 8, which showed the highest formic acid production rate in Table 3, was 34.5%.

[0125] [Hydrogen generation capacity] When the hydrogen generation ability of organic compounds was evaluated using the method described above, hydrogen was generated when organic compounds modified with Pt nanoparticles were used as photocatalysts upon irradiation with visible light. The hydrogen generation rates are shown in Table 4 below. [Table 4]

[0126] Cz x -DbtO y -Bpy z In the organic compounds of Examples 13 to 16, high hydrogen generation activity was observed in all of them compared to Comparative Example 5, which had only the second section, and Comparative Example 6, which had a similar configuration except for the absence of the second section. From this, it was inferred that the organic compound containing part B, which includes all of the first to third sections, is particularly suitable as a photocatalyst.

[0127] [Oxygen production ability] When the oxygen-producing ability of organic compounds was evaluated using the method described above, oxygen was produced when organic compounds modified with IrO2 colloid were used as photocatalysts and exposed to visible light. The oxygen production rates are shown in Table 5 below. [Table 5]

[0128] The organic compound in Example 17 containing Cz1-DbtO2-Bpy1 showed higher oxygen generation activity compared to Comparative Example 7, which had only the second section, and Comparative Example 8, which had a similar structure except for the absence of the second section. From this, it was inferred that the organic compound containing part B, which includes all of the first to third sections, is particularly suitable as a photocatalyst.

[0129] <Manufacturing Example 3: Fabrication of a photocatalyst combining Cz2-DbtO3-Bpy1 and metal ions> As described above, 2 mg of Cz2-DbtO3-Bpy1 particles and 2 mL of acetonitrile-triethanolamine mixed solvent (volume ratio 4:1) were placed in a Pyrex® test tube, and the particles were dispersed in the mixed solvent by ultrasonic irradiation using an ultrasonic cleaner. Next, iron(II) chloride tetrahydrate, copper(II) chloride, manganese(II) chloride tetrahydrate, or cobalt(II) chloride hexahydrate were dissolved in the resulting dispersion to a concentration of 1 mmol / L to obtain a dispersion combining organic compound A and metal ions. Next, 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole was further dissolved as a sacrificial reducing agent to a concentration of 50 mmol / L to obtain the dispersions of Examples 18 to 21. The metal ion content in each dispersion was 83 mol%, based on the molar amount of the third section of the total Cz2-DbtO3-Bpy1 contained in the dispersion.

[0130] <Manufacturing Example 4: Preparation of a photocatalyst that does not contain metal ions> Two mg of Cz2-DbtO3-Bpy1 particles prepared as described above were placed in a Pyrex® test tube with two mL of acetonitrile-triethanolamine mixed solvent (volume ratio 4:1), and the particles were dispersed in the mixed solvent by ultrasonic irradiation using an ultrasonic cleaner. Next, 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole was further dissolved at a concentration of 50 mmol / L as a sacrificial reducing agent to obtain the dispersion of Example 22. The dispersion of Example 22 did not contain metal ions.

[0131] <Test Example 3: Photocatalytic properties of each prepared dispersion> [CO2 reduction ability] Each dispersion in Examples 18-22 was aerated with 1 atmosphere of CO2 gas for 20 minutes, and then the test tubes were sealed with rubber septums. Next, the dispersions in the test tubes were irradiated with visible light at room temperature for 15 hours. For visible light irradiation, the LED merry-go-round light irradiation device (Iris-S, Cell Systems, Inc.) described above was used, and the five types of LEDs described above were used. The amount of purified formic acid and gas (CO) produced by light irradiation was analyzed by the method described above.

[0132] [Hydrogen generation capacity] The hydrogen generation capacity of each dispersion in Examples 18-22 was evaluated in the same manner as the evaluation of CO2 reduction capacity, except that CO2 gas was not passed through them. The amount of hydrogen produced by light irradiation was analyzed using the method described above.

[0133] The evaluation results for CO2 reduction capacity and hydrogen generation capacity are shown in Table 6 below.

[0134] [Table 6]

[0135] As shown in Table 6, the CO2 reduction ability of the photocatalysts in Examples 18-21, which incorporated metal ions, was improved compared to the photocatalyst in Example 22, which did not contain metal ions. Furthermore, the hydrogen generation ability of the photocatalysts in Examples 19-20 was improved compared to the photocatalyst in Example 22. [Industrial applicability]

[0136] The organic compounds of the present invention can be used, for example, as photocatalysts in CO2 reduction reactions, proton reduction reactions, and water splitting reactions.

Claims

1. A chain-like organic compound, The molecular chain of the organic compound has a portion comprising a first section composed of a first structural unit, a second section composed of a second structural unit, and a third section composed of a third structural unit. In the aforementioned portion, The first section, the second section, and the third section are joined in this order to form a π-conjugated system. The lowest empty orbital level of each of the aforementioned structural units decreases in the order of the first structural unit, the second structural unit, and the third structural unit. The aforementioned organic compound can be excited by visible light. organic compound.

2. The organic compound according to claim 1, wherein the energy gap between the energy level of the highest occupied orbital and the energy level of the lowest unoccupied orbital of the organic compound is 3.1 eV or less.

3. The organic compound according to claim 1, wherein the number of the second structural units included in the second section is two or more.

4. The organic compound according to claim 1, wherein the ratio n2 / n1 of the number of second structural units in the second section to the number of first structural units n1 in the first section is 1 or more and 3 or less.

5. The organic compound according to claim 1, wherein the number of the third structural units included in the third section is two or less.

6. The lowest unoccupied orbital level LUMO of the first structural unit U1 and the lowest unoccupied orbital level LUMO of the third structural unit U3 The organic compound according to claim 1, wherein the absolute value of the difference is 0.10 eV or more.

7. The lowest unoccupied orbital level LUMO of the first structural unit U1 and the lowest unoccupied orbital level LUMO of the third structural unit U3 Let X be the absolute value of the difference between the two values ​​(unit: eV). When the number of second structural units included in the second section is n relative to the number of third structural units included in the third section, The organic compound according to claim 1, wherein the ratio X / n is 0.08 eV or more and 0.43 eV or less.

8. The organic compound according to claim 1, wherein at least one structural unit selected from the group consisting of the first structural unit, the second structural unit, and the third structural unit has a skeleton containing two or more aromatic rings.

9. The organic compound according to claim 1, wherein at least one structural unit selected from the group consisting of the first structural unit, the second structural unit, and the third structural unit has a skeleton including a condensed aromatic ring.

10. The organic compound according to claim 1, wherein at least one structural unit selected from the group consisting of the first structural unit, the second structural unit, and the third structural unit has a condensed polycyclic hydrocarbon skeleton.

11. The organic compound according to claim 1, wherein the first structural unit has a carbazole skeleton, a condensed polycyclic hydrocarbon skeleton, a thiophene skeleton, or a dibenzothiophene skeleton.

12. The organic compound according to claim 1, wherein the second structural unit has a condensed polycyclic hydrocarbon skeleton, a thiophene skeleton, or a dibenzothiophene skeleton.

13. The organic compound according to claim 1, wherein the third structural unit has an aromatic diimine skeleton.

14. The organic compound according to claim 1, wherein the third structural unit has a structure in which a metal atom or a group of atoms containing a metal atom is coordinately bonded to an organic skeleton.

15. The organic compound according to claim 14, wherein the organic skeleton is an aromatic diimine skeleton.

16. The organic compound according to claim 14, wherein the metal atom is at least one selected from the group consisting of ruthenium, rhenium, platinum, iridium, rhodium, palladium, iron, cobalt, and nickel.

17. The organic compound according to claim 1, for use as a photocatalyst.

18. The organic compound according to claim 1, for modifying metal particles or metal compound particles.

19. A photocatalyst comprising the organic compound described in any one of claims 1 to 18.

20. The photocatalyst according to claim 19, further comprising metal particles or metal compound particles.

21. The photocatalyst according to claim 19, further comprising metal ions.

22. The photocatalyst according to claim 19, for use in the reduction reaction of carbon dioxide, water, or protons, or for use in the oxidation reaction of water.

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