JP7776101B2 - Electrofluorochromic sheet, electrofluorochromic device, and metallosupramolecular polymer - Google Patents

Description

The present invention relates to an electrofluorochromic sheet, an electrofluorochromic device, and a metallosupramolecular polymer.

Materials with electrofluorochromic properties, which allow for electrically induced reversible changes in fluorescence intensity, are known. Such materials are expected to be used as fluorescent switching materials in optical memory devices, logic gates, biological imaging, sensors, and displays, and development is underway.

Non-Patent Document 1 describes a polymer compound containing cyanoarylamine as a material with such electrofluorochromic properties.

Chemical Communications, 2013, 49, pp. 9797-9799

The inventors have continued to develop electrochromic sheets using metallo-supramolecular polymers formed by alternating organic ligands and (metal) cations, as well as electrochromic devices containing such sheets. However, they have not yet succeeded in completing an electrofluorochromic sheet using a metallo-supramolecular polymer.

Therefore, an object of the present invention is to provide a novel electrofluorochromic sheet containing a metallo-supramolecular polymer. Another object of the present invention is to provide an electrofluorochromic element containing this electrofluorochromic sheet, and a metallo-supramolecular polymer.

As a result of extensive research into achieving the above objectives, the inventors have discovered that the above objectives can be achieved by the following configuration.

[1] An electrofluorochromic sheet comprising a metallo-supramolecular polymer formed by alternating cations of at least one element A selected from the group consisting of metal elements of Groups 7 to 12 and lanthanoid elements with organic ligands via a bonding form including at least one selected from the group consisting of coordinate bonds and organometallic bonds, wherein the organic ligand has two or more coordination sites per molecule that form at least one luminescent complex selected from the group consisting of metal complexes and organometallic complexes via the bonding form with the cations, and has one or more redox-responsive sites that undergo an oxidation-reduction reaction upon application of an electric potential, and the redox-responsive site has at least one nitrogen atom, and in the organic ligand, the coordination site and the redox-responsive site are directly bonded or bonded via a spacer site.
[2] The electrofluorochromic sheet according to [1], wherein the metal element is at least one selected from the group consisting of rhenium, ruthenium, osmium, rhodium, iridium, platinum, copper, silver, gold, zinc, and cadmium.
[3] The electrofluorochromic sheet according to [1] or [2], wherein the lanthanoid element is at least one selected from the group consisting of praseodymium, neodymium, samarium, europium, gadolinium, and terbium.
[4] The coordination site includes at least one structure selected from the group consisting of a nitrogen-containing heterocycle and an aromatic ring capable of forming a metal-carbon bond, [1] to [3]. The electrofluorochromic sheet according to any one of the above.
[5] The electrofluorochromic sheet according to any one of [1] to [4], wherein the redox responsive site comprises at least one structure selected from the structures represented by formulas 2A to 2C described below.
[6] The electrofluorochromic sheet according to [5], wherein the redox responsive site comprises at least one structure selected from the group consisting of a structure represented by the formula 2A and a structure represented by the formula 2B.
[7] The electrofluorochromic sheet according to any one of [1] to [6], wherein the spacer moiety comprises an arylene group having 6 to 20 carbon atoms which may contain a heteroatom.
[8] The metallo-supramolecular polymer is a repeating unit selected from the group consisting of formula 5AP, formula 5BP, formula 6AP, formula 6BP, formula 7AP, formula 7BP, formula 8AP, and formula 8BP, which is described later. The electrofluorochromic sheet according to any one of [1] to [7], which contains one or more repeating units selected from the group consisting of formula 5AP, formula 5BP, formula 6AP, formula 6BP, formula 7AP, formula 7BP, formula 8AP, and formula 8BP.
[9] The electrofluorochromic sheet according to any one of [1] to [8], wherein the spacer moiety is at least one divalent group selected from the group consisting of an alkynylene group having 2 to 20 carbon atoms, an arylene group having 6 to 20 carbon atoms, a heteroarylene group having 6 to 20 carbon atoms, and a group formed by combining these groups.
[10] The metallo-supramolecular polymer comprises at least one trifunctional branch point selected from the group consisting of formulas 5CP, 6CP, 7CP, 8CP, and 9CP, or any one or more of the following: [1] to [9]. The electrofluorochromic sheet according to any one of the above.
[11] An electrofluorochromic device comprising a pair of electrodes and the electrofluorochromic sheet according to any one of [1] to [10] sandwiched between the electrodes.
[12] A metallo-supramolecular polymer comprising at least one repeating unit selected from the group consisting of Formula 5AP, Formula 5BP, Formula 6AP, Formula 6BP, Formula 7AP, Formula 7BP, Formula 8AP, Formula 8BP, Formula 9AP, and Formula 9BP, which will be described later.
[13] The metallo-supramolecular polymer according to [12] further comprises at least one trifunctional branch point selected from the group consisting of formula 5CP, formula 6CP, formula 7CP, formula 8CP, and formula 9CP described below, or two or more of them.

The present invention provides a novel electrofluorochromic sheet containing a metallo-supramolecular polymer. The present invention also provides an electrofluorochromic element containing this electrofluorochromic sheet, and a metallo-supramolecular polymer.

1 is a cross-sectional view illustrating a configuration of an electrofluorochromic device according to an embodiment of the present invention. This is a diagram showing the change in the ultraviolet-visible absorption _spectrum when a Zn(BF ₄ ) ₂ solution (MeOH, c=5×10 ⁻⁴ mol/L) is added to a CH ₂ Cl ₂ solution (c=1×10 ⁻⁵ mol/L) containing an organic ligand (LTPA ). FIG. 1 is a graph showing the change in absorbance at 431 nm versus the metal/organic ligand molar ratio. 1 is an absorption spectrum of a polyZn-EFC film (a specific embodiment of the electrofluorochromic sheet according to the present invention) on an ITO (indium tin oxide) glass substrate. 1 shows the emission spectrum of a polyZn-EFC film on an ITO glass substrate excited at 425 nm. 1 shows the results of X-ray photoelectron spectroscopy (XPS) measurement of the polyZn-EFC film. 1 shows a cyclic voltammogram of a polyZn-EFC film. FIG. 1 is a graph showing the change in luminescence intensity (excitation light=425 nm) when a potential of 0 to 1.6 V is applied to the working electrode of an electrofluorochromic device according to a specific embodiment of the present invention. A comparison of an image (bottom) showing the quenched state when 1.6 V is applied to the working electrode of the electrofluorochromic device and an image (top) showing the luminescent state when no potential is applied (0 V). This figure shows the measurement of the emission intensity at a wavelength of 650 nm when the fluorescence was repeatedly turned on and off by applying a potential. 1 shows the results of ¹ H NMR (Nuclear Magnetic Resonance, CD ₃ OD) measurement of polyZn-EFC.

The present invention will be described in detail below.
The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment.
In this specification, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits.
In this specification, a notation such as "C ₁₀ " in which a number is added after "C" indicates that the number of carbon atoms is the number of the subscript. "C ₁₀ " indicates that the number of carbon atoms is 10. This notation is used as in "C ₁₀ alkyl group" and is synonymous with "an alkyl group having 10 carbon atoms."

[Electrofluorochromic Device]
FIG. 1 is a cross-sectional view showing the configuration of an electrofluorochromic (hereinafter also referred to as "EFC") device according to an embodiment of the present invention.
The EFC device 10 includes a pair of electrodes 15 , an EFC sheet 13 sandwiched therebetween, and a solid electrolyte 12 .

The pair of electrodes 15 includes a first electrode 11 and a second electrode 14. The first electrode 11 is in contact with the solid electrolyte 12, and the second electrode 14 is in contact with the EFC sheet 13. The solid electrolyte 12 and the EFC sheet 13 are also in contact with each other.

The EFC device 10 has a pair of electrodes 15. When a potential is applied between these electrodes 15, the redox-responsive site (details of which will be described later) of the metallo-supramolecular polymer contained in the EFC sheet 13 undergoes an oxidation-reduction reaction, thereby exhibiting electrofluorochromic properties.

The material of the pair of electrodes 15 is not particularly limited, but from the viewpoint of facilitating application of the EFC device to displays and the like, it is preferable that the material be light-transmitting.
Examples of such materials include a SnO ₂ film, an In ₂ O ₃ film, and an ITO (Indium Tin Oxide) film.

An active material layer may also be disposed on the surface of the first electrode 11 facing the solid electrolyte 12. An EFC device 10 having an active material layer can switch the fluorescent light on and off with less power.

Examples of active materials include sodium iron phosphate, sodium cobalt oxide, sodium manganese bronze, copper hexacyanoferrate, and nickel hexacyanoferrate.

The material of the solid electrolyte 12 is not particularly limited, but typically, a composite containing a polymer compound, a supporting salt, and a plasticizer is preferred.

Polymer compounds include, but are not limited to, polymethyl methacrylate (PMMA), polyethylene oxide (PEO), poly(vinylidene fluoride-co-hexafluoroisopropyl) (PVdF-co-PHFP), polypropylene carbonate (PPC), polycarbonate, and polyacrylonitrile.

The content of the polymer compound in the composite is not particularly limited, but is preferably 18 to 80% by mass when the total mass of the composite is taken as 100% by mass.

_The supporting salt is not particularly limited, but _examples thereof include _LiClO4 , _LiBF4 , LiAsF6, _LiPF6 , _LiCF3SO3 , _LiCF3COO , lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), _LiCH3COO , tetrabutylammonium perchlorate, tetraethylammonium perchlorate, KCl, NaClO3, NaCl, NaBF4, NaSCN, _KBF4 , Mg( _ClO4 ) _{2 ,} and Mg( _BF4 ) _{2 .}

The content of supporting salt in the composite is not particularly limited, but is preferably 1 to 15% by mass when the total mass of the composite is taken as 100% by mass.

Furthermore, examples of plasticizers include propylene carbonate (PC), ethylene carbonate, dimethyl carbonate, diethylene carbonate, gamma-butyrolactone, succinonitrile, and ionic liquids.

The amount of plasticizer in the composite is not particularly limited, but is preferably 18 to 80% by mass when the total mass of the composite is taken as 100% by mass.

The method for preparing the solid electrolyte 12 is not particularly limited, but may be such that the components are mixed and then heated as necessary. The temperature at which the mixture is heated is not particularly limited, but may be from room temperature to 100°C.
Although the EFC device 10 has the solid electrolyte 12 , the EFC device of the present invention does not necessarily have to have the solid electrolyte 12 .

There are no particular limitations on the manufacturing method for the EFC device of the present invention, but it is sufficient to stack each layer in order on the first electrode 11 (or second electrode 14).

The EFC sheet is a thin plate-like member that contains a metallo-supramolecular polymer, which will be described later, and whose fluorescence intensity changes reversibly when a potential is applied by a pair of electrodes 15 .
The EFC sheet is sufficient as long as it contains the metallo-supramolecular polymer described below, and may also contain other components. The content of the metallo-supramolecular polymer in the EFC sheet is not particularly limited, but is preferably 60% by mass or more, and more preferably 80% by mass or more, when the total mass of the EFC sheet is taken as 100% by mass. In one embodiment, the EFC sheet is preferably made of a metallo-supramolecular polymer.

The thickness of the EFC sheet can be adjusted as appropriate depending on the application of the EFC device, but for use as a display or light control panel, for example, a thickness of 10 nm to 10,000 μm is generally preferred.

When this EFC device is excited by irradiating it with light of a predetermined excitation wavelength in a state where no potential is applied to the second electrode 14, it emits light at a wavelength (color) that corresponds to the structure of the metallo-supramolecular polymer (the structure of the luminescent complex, described below, plays a major role). On the other hand, when a positive potential is applied to the second electrode 14, the emission intensity decreases according to the magnitude of the potential, and when a potential above a predetermined potential is applied, the emission is quenched. Furthermore, when the potential of the second electrode is brought closer to 0, the emission intensity increases again, and this cycle can be repeated.

In this case, there are no particular restrictions on the potential applied between the pair of electrodes 15, but generally, a potential of 0 to 4.0 V is preferred.

(Metallo-supramolecular polymer)
Next, the metallo-supramolecular polymer contained in the EFC sheet will be described in detail.

The metallo-supramolecular polymer is formed by alternating cations of at least one element (hereinafter also referred to as "element A") selected from the group consisting of metal elements of Groups 7 to 12 and lanthanoid elements with organic ligands via a bonding form that includes at least one selected from the group consisting of coordinate bonds and organometallic bonds. The organic ligand has two or more coordination sites per molecule that form at least one luminescent complex selected from the group consisting of metal complexes and organometallic complexes through the above bonding form with the cations. The organic ligand also has one or more redox-responsive sites that undergo an oxidation-reduction reaction upon application of an electric potential. The redox-responsive site has at least one nitrogen atom. In the organic ligand, the coordination site and the redox-responsive site are bonded directly or via a spacer site.

The reason why the above-mentioned metallo-supramolecular polymer exhibits electrofluorochromic properties is not entirely clear, but the inventors speculate as follows. Note that the following mechanism is merely speculation and is not a definitive explanation of the mechanism of action of the present invention.

The inventors speculate that the following three factors are related to the electrofluorochromic properties of the above metallo-supramolecular polymer:

(1) When a potential is applied, a redox reaction occurs, and radical cations are generated at the redox-responsive site, which quench the luminescence.
(2) The absorption due to the n-π* transition of the organic ligand is reduced or eliminated by the generation of radical cations, which prevents the metallo-supramolecular polymer from entering an excited state and makes it difficult for light to be emitted.
(3) Radical cations are generated at the redox-responsive site, which causes new absorption and quenches the luminescence due to energy transfer.

The metallo-supramolecular polymer is formed by combining an organic ligand with a cation of element A. The organic ligand has two or more coordination sites and one or more redox-responsive sites, and thus the polymer is formed by repeated bonding between the coordination sites and the cation.
The luminescent complex formed by the combination of the coordination site and the cation is bound to the redox-responsive site with or without a spacer site, and therefore can satisfy all of the above conditions (1) to (3), and it is presumed that the desired electrofluorochromic properties are obtained.

Below, we will first explain the cations and organic ligands that make up the repeating units of metallo-supramolecular polymers, and then provide a detailed description of the structure of the metallo-supramolecular polymers formed thereby.

(cation)
The cation constituting the metallo-supramolecular polymer is a cation of at least one element A selected from the group consisting of metal elements of Groups 7 to 12 and lanthanoid elements.

There are no particular restrictions on the metal elements from Groups 7 to 12, and any known metal element can be used, as long as it forms a luminescent complex in combination with the coordination site of the organic ligand described below. Examples of metal elements include Re, Ru, Os, Rh, Ir, Pt, Cu, Ag, Au, Zn, and Cd. At least one element selected from the group consisting of Ru, Ir, Pt, Zn, and Cd is preferred, and at least one element selected from the group consisting of Ir, Pt, Zn, and Cd is more preferred.

In this specification, the term "luminescent complex" does not refer to a single independent compound such as the entire metallo-supramolecular polymer, but rather refers to a "metal complex" or "organometallic complex" formed by coordination bonding or organometallic bonding between multiple coordination sites and a single cation of element A, and incorporated as part of the metallo-supramolecular polymer. In this specification, the "luminescent complex" is preferably a divalent group formed by removing two hydrogen atoms from a general luminescent complex.

The selection of a "luminescent complex" within the metallo-supramolecular polymer can be determined based on whether the complex has luminescent functionality in the general sense. In other words, the "luminescent complex" incorporated as part of this metallo-supramolecular polymer is preferably a compound that itself has luminescence, and such compounds are known to those skilled in the art.

Like the metal elements described above, there are no particular limitations on the lanthanoid elements, so long as they can form a luminescent complex with the coordination site of the organic ligand described below. Examples of such lanthanoid elements include praseodymium, neodymium, samarium, europium, gadolinium, and terbium, with europium and/or terbium being more preferred.

(organic ligand)
The organic ligand has two or more coordination sites in one molecule that coordinate to a cation to form a luminescent complex, and one or more redox-responsive sites that cause an oxidation-reduction reaction when an electric potential is applied. The coordination site and the redox-responsive site are bonded directly or via a spacer site.

Examples of bonding forms between an organic ligand and a cation include coordination bonding, in which a cation is bonded to nitrogen (N), oxygen (O), sulfur (S), or the like, and organometallic bonding, in which a cation is bonded to carbon.
In this specification, a complex formed by coordinate bonds is called a metal complex, and a complex formed by organometallic bonds is called an organometallic complex.

Examples of luminescent complexes formed by such bonding forms include those represented by the following formulas Z1 to Z4. In the formulas below, * represents the bonding position with the spacer moiety or the redox-responsive moiety.

The luminescent complex may be one in which the bond between the cation and the coordination site is formed by either a coordinate bond or an organometallic bond, as represented by formula Z1 and formula Z2. Alternatively, the luminescent complex may be one in which the bond is formed by both a coordinate bond and an organometallic bond, as represented by formula Z3. Alternatively, the luminescent complex may be one in which the bond is formed by a coordinate bond and/or an organometallic bond (hereinafter also referred to as a "coordinate bond, etc.") in addition to other bonds, as represented by formula Z4.
In particular, the luminescent complex represented by formula Z4 is more stable and preferable when the central cation is a lanthanoid element including terbium. The four carboxy groups in the luminescent complex represented by formula Z4 form salts with the central Eu (europium) cation, and examples of such groups include hydroxy groups in addition to the above.

Metallo-supramolecular polymers are polymers formed by alternating cations and the above-mentioned organic ligands linked together through coordination bonds, etc. Because the organic ligands have two or more coordination sites within the molecule, the unit structure is repeated through the bonding between these coordination sites and cations, forming a polymer compound.

The branching structure of the molecular chains of metallo-supramolecular polymers is influenced not only by the number of coordination sites of the organic ligands (described below), but also by the bonding structure between the cation and the coordination site. When three or more coordination sites are coordinated to a cation, trifunctional or higher branching points are formed.

In this regard, from the viewpoint of easily controlling the solvent solubility of the metallo-supramolecular polymer, a form in which the cations and coordination sites are coordinated at a molar ratio of 1:2 is preferred. For example, such a form may be one in which the coordination number of the cations is twice the number of coordination sites of the coordination sites. Below, we will explain a form in which the cations and coordination sites are coordinated at a molar ratio of 1:2.

The above formula 1 is an example of a preferred bonding form between a cation and a coordination moiety in a metallo-supramolecular polymer. In formula 1, M is a cation, Lig is a coordination moiety, ^L2 represents a single bond or -Sp-, Sp is a spacer moiety described later, and * represents a bonding position with a redox-responsive moiety described later. In the above formula 1, Lig is bonded to M via a coordination bond or the like, and Lig is covalently bonded to the redox-responsive moiety or Sp. Note that the two Ligs may be the same or different, but are preferably the same, and the same applies when there are two Sps.

The coordination site is not particularly limited as long as it can form a luminescent complex in relation to the cation. However, for example, groups having a nitrogen-containing heterocycle and an aromatic ring (e.g., a benzene ring) capable of forming a metal-carbon bond are preferred.

The group having a nitrogen-containing heterocycle is not particularly limited, but examples include monocyclic rings having 3 to 7 members and a nitrogen atom, and monovalent groups in which one hydrogen atom has been removed from these fused rings (collectively referred to as "nitrogen-containing coordination moieties"). The ring may have one or more carbon atoms.

Nitrogen-containing coordination sites include pyrrole, imidazole, pyrazole, oxazole, isoxazole, thiazole, isothiazole, 1,2,3-triazole, 1,2,4-triazole, 1,3,4-thiadiazole, tetrazole, pyridine, pyrazine, pyrimidine, pyridazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4,5-tetrazine, azepine, azonine, quinoline, isoquinoline, acridine, phenanthridine, indole, isoindole, and carbazole. , benzimidazole, 1,8-naphthyridine, purine, pteridine, benzotriazole, quinoxaline, quinazoline, perimidine, cinnoline, phthalazine, 1,10-phenanthroline, phenoxazine, phenothiazine, phenazine, 8-hydroxyquinoline, 8-mercaptoquinoline, 2,2'-bipyridine, 2,2'-dipyridylamine, di(2-picolylamine), 2,2',2"-terpyridine, porphyrin, phthalocyanine, and monovalent groups formed by removing one hydrogen atom from these derivatives.

In addition, since the resulting metallo-supramolecular polymer exhibits superior effects of the present invention, the nitrogen-containing coordination site is preferably a monovalent group formed by removing one hydrogen atom from pyrrole, imidazole, pyrazole, oxazole, thiazole, pyridine, or a derivative thereof.

Specific structures of nitrogen-containing coordination sites are shown below. The nitrogen-containing coordination site is a monovalent group obtained by removing one of the hydrogen atoms contained in these compounds. An optional substituent may also be bonded to the site. In the following formulas, p represents an integer of 2 or greater and is not particularly limited, but is preferably 20 or less, more preferably 10 or less, and even more preferably 6 or less.

Precursor compounds for forming nitrogen-containing coordination sites may be commercially available or may be synthesized using known methods (e.g., C. H. Weidl, A. A. Precup, C. Eschbaumer, U.S. Schubert, Polymeric Materials: Science and Engineering, 84, 649 (2001)).

In addition to the above, the coordination site may also be a group having a hydroxy group, an alkoxy group, an acyl group, an alkoxy-carbonyl group, an acetylacetonato group, a benzylidene acetylacetonato group, a cycloalkadienyl group (such as a cyclopentadienyl group and a cyclooctadienyl group), a benzylidene group, a cyano group, a nitro group, an amino group, a phosphino group, or a combination thereof.

The organic ligand has two or more coordination sites in one molecule, and although there is no particular upper limit, it is preferably four or less, and more preferably three or less.
The two or more coordination sites may be the same or different, but are preferably the same.

(Spacer part)
The spacer moiety is a moiety that connects the coordination moiety and the redox-responsive moiety (described later) to form the main chain of the metallo-supramolecular polymer.
The bonding form between the coordination site and the redox-responsive site is not particularly limited, but it is preferable that they are linked by a covalent bond.

The structure of the spacer moiety is not particularly limited, but it is preferable that the part adjacent to the redox responsive site, i.e., the part directly bonded to the redox responsive site, has a C ₆ -C ₂₀ arylene group or a C ₆ -C ₂₀ heteroarylene group.

As described below, the redox responsive moiety contains a nitrogen atom and generates a radical cation upon application of a (positive) potential. In this case, if a spacer moiety having a divalent aromatic hydrocarbon group such as a _C6 - _C20 arylene group or a _C6 - _C20 heteroarylene group is located adjacent to the redox responsive moiety, the radical cation generated upon application of a potential is likely to be stabilized.

In electrofluorochromic sheets, it is preferable that the fluorescent OFF state induced by the application of an electric potential be as stable as possible. Additionally, the ability to repeatedly turn ON/OFF is also an important characteristic.

In this regard, when the spacer moiety has an arylene group and/or a heteroarylene group and is directly bonded to the redox-responsive moiety, the resulting metallo-supramolecular polymer is more likely to stabilize the radical cation generated by the application of an electric potential and to have better properties required for the application of electrofluorochromic materials.

The spacer moiety preferably has the function of linking the coordination moiety and the redox-responsive moiety, as well as the function of electron transfer within the organic ligand. For example, it is preferable that such a spacer moiety is conjugated in whole or in part.

Preferred examples of such a spacer moiety include linear, branched, or cyclic C ₁ to C ₂₀ alkylene groups, C ₂ to C ₂₀ alkenylene groups, and C ₂ to C ₂₀ alkynylene groups; C ₆ to C ₂₀ arylene groups; C ₆ to C ₂₀ heteroarylene groups; and groups combining these.
Among these, the spacer moiety is preferably at least one divalent group selected from the group consisting of a _C2 - _C20 alkynylene group, a _C6 - _C20 arylene group, a _C6 - _C20 heteroarylene group, and a combination thereof, in that an electrofluorochromic material having a more excellent effect of the present invention can be obtained.

An example of a spacer moiety is a group represented by the following formula 3AA. In formula 3AA, * represents the bonding position with the redox-responsive moiety and the coordination moiety, respectively.

(Redox response site)
The redox-responsive site refers to an atomic group that undergoes an oxidation-reduction reaction upon application of an electric potential. The organic ligand has at least one redox-responsive site per molecule, and although there is no particular upper limit, three or less is generally preferred. The oxidation-reduction reaction may result in the generation/elimination of a radical cation.

The redox-responsive site contains at least one nitrogen atom, which has an unshared electron pair and generates a radical cation upon application of a (positive) potential.
As already explained, it is presumed that the reversible generation and disappearance of stable radical cations inside the organic ligand molecules contributes to the achievement of fluorescence ON/OFF switching.

From the viewpoint of obtaining a metallo-supramolecular polymer with superior effects of the present invention, it is preferable that the redox-responsive moiety be at least one structure selected from the structures represented by formulas 2A to 2C below.

In Formula 2A, R ²¹ _and R ²² each independently represent a hydrogen atom or a C ₁ to C ₂₀ hydrocarbon group, L ¹ represents a divalent C ₁ to C ₂₀ hydrocarbon group, and * represents the bonding position with the spacer moiety.

The group represented by Formula 2A is a side branch bonded to a spacer moiety constituting the main chain of the metallo-supramolecular polymer, and is a pendant group.

The C ₁ to C ₂₀ hydrocarbon groups of R ²¹ and R ²² include C ₁ to C ₂₀ alkyl groups, C ₂ to C ₂₀ alkenyl groups, and C ₂ to C ₂₀ alkynyl groups, which may have heteroatoms, and any of these may be linear, branched, or cyclic.

Other examples of the C ₁ to C ₂₀ hydrocarbon group for R ²¹ and R ²² include a C ₆ to C ₂₀ aryl group and a C ₆ to _{C 20} heteroaryl group, and these may be combined with a linear, branched, or cyclic alkyl group, alkenyl group, or alkynyl group.

In particular, it is preferable that R ²¹ and R ²² contain a C ₆ to C ₂₀ aryl group and a C ₆ to C ₂₀ heteroaryl group, in that the radical cation generated by the oxidation-reduction reaction can be further stabilized.
R ²¹ and R ²² may be the same or different.

Examples of the divalent C ₁ -C ₂₀ hydrocarbon group of L ¹ include the divalent groups explained as specific examples of the spacer moiety, and the preferred embodiments are also the same.

In Formula 2B, R ²³ represents a hydrogen atom or a C ₁ -C ₂₀ hydrocarbon group, and * in Formula 2B and Formula 2C represents a coordination site or a bonding site with a spacer site.

The divalent group represented by formula 2B is bonded to two coordination sites, two spacer sites, or a coordination site and a spacer site, and is incorporated into the main chain of the metallo-supramolecular polymer. In formula 2B, ^R23 has the same meaning as ^R21 , and the preferred embodiments are also the same.

The trivalent group represented by formula 2C is bonded to three moieties selected from the group consisting of coordination moieties and spacer moieties to form a trifunctional branch point.

When the redox-responsive moiety consists solely of the structure represented by Formula 2A or Formula 2B, branch points do not usually occur at the redox-responsive moiety. Furthermore, in the form in which the cation:coordination moiety coordinates at a molar ratio of 1:2 as described above, branch points are generally unlikely to occur in the luminescent complex moiety, and the resulting metallo-supramolecular polymer tends to be linear.

The reason we say that it "easily becomes" linear is that during the polymerization process of the metallo-supramolecular polymer, steric hindrance can occur, preventing the formation of coordinate bonds, etc., resulting in disruption of 1:2 coordinate bonds (deteriorating the "structural regularity" described in JP 2018-145244 A), and in cases where three coordination sites, which should normally bind to one cation, become bonded, instead of two, and unintended branching points can occur.

However, when the redox responsive moiety contains a structure represented by Formula 2A or Formula 2B, and the cation:coordination moiety is coordinated in a molar ratio of 1:2 as a rule, a metallo-supramolecular polymer having a repeating unit represented by Formula 3A or Formula 3B is typically obtained.
Metallo-supramolecular polymers containing such repeating units have the excellent characteristics of being easily soluble in solvents and easily formed into films.

In Formula 3A, Lig represents a coordination site, Sp represents a spacer site, M represents a cation of element A, CA represents a counter anion that compensates for the charge, and the other symbols (L ¹ , R ²¹ , and R ²² ) have the same meanings as the respective symbols in Formula 2A.
In addition, in Formula 3B, Lig represents a coordination site, ^L2 represents a single bond or -Sp-, Sp represents a spacer site, M represents a cation of element A, CA represents a counter anion that compensates for the charge, and ^R23 has the same meaning as the same symbol in Formula 2B.

On the other hand, when the redox responsive moiety contains a structure represented by formula 2C above, a trifunctional branch point is formed in the redox responsive moiety. Metallo-supramolecular polymers having such a structure have excellent mechanical strength.

Such a trifunctional branch point includes a structure represented by the following formula 3C when the cation:coordination site is coordinately bonded at a molar ratio of 1:2 in principle.
In Formula 3C, Lig represents a coordination site, ^L2 represents a single bond or -Sp-, Sp represents a spacer site, and M represents a cation of element A. In addition, * in the formula represents the position of a coordination bond with Lig of another organic ligand.

(Preferred Form of Organic Ligand)
Next, preferred forms of the organic ligand will be explained.
Preferred forms of the organic ligand include compounds represented by formula 4A, formula 4B, and formula 4C.

In the above formulas 4A to 4C, Lig represents a coordination site, ^L2 represents a single bond or -Sp-, Sp represents a spacer site, and ^R21 , ^R22 , and ^R23 have the same meanings as the respective symbols in formulas 2A to 2C, and the preferred embodiments are also the same.

In particular, from the viewpoint of obtaining an electrofluorochromic sheet that exhibits the effects of the present invention more effectively, it is preferable that the organic ligand contains a compound represented by 4B.

When the organic ligand contains a compound represented by the following formulas 5A to 5C, 6A to 6C, 7A to 7C, 8A to 8C, and 9A to 9C, the resulting electrofluorochromic sheet has a better effect of the present invention.
In particular, when the organic ligand contains one or more of the compounds represented by formulas 5A to 5C, 6A to 6C, 7A to 7C, and 8A to 8C, the electrofluorochromic sheet has even more excellent effects of the present invention.
When the organic ligand contains compounds represented by 5B, 6B, 7B, 8B, and 9B, the electrofluorochromic sheet has better effects of the present invention, and when it contains compounds represented by 5B, 6B, 7B, and 8B, the electrofluorochromic sheet has even better effects of the present invention.

In formulas 5A to 5C, R ⁵¹ , R ⁵² , and R ⁵³ each independently represent at least one atom or group selected from the group consisting of a hydrogen atom, an alkyl group, and an aryl group, and multiple R ⁵¹ , R ⁵² , and R ⁵³ may be the same or different. L ² represents a single bond or -Sp-, where Sp represents a spacer moiety. R ²¹ , R ²² , and R ²³ have the same meanings as the respective symbols in formulas 2A to 2C, and the preferred embodiments are also the same.

The alkyl group of R ⁵¹ , R ⁵² and R ⁵³ is not particularly limited, but examples thereof include linear or branched C ₁ to C ₂₀ alkyl groups. The aryl group includes C ₆ to C ₂₀ aryl groups.
More specifically, examples of R ⁵¹ include a methyl group, an ethyl group, an n-butyl group, a t-butyl group, a phenyl group, and a toluyl group.

These aryl groups and alkyl groups may further have a substituent, such as alkyl groups such as methyl, ethyl, and hexyl, alkoxy groups such as methoxy and butoxy, and halogen groups such as chlorine and bromine.

In formulae 6A to 6C, R ⁶¹ , R ⁶² , and R ⁶³ represent at least one selected from the group consisting of a hydrogen atom, an alkyl group, and an aryl group, and a plurality of R ⁶¹ , R ⁶² , and R ⁶³ may be the same or different, and the preferred embodiments are the same as those of R ⁵¹ .
Furthermore, ^L2 represents a single bond or -Sp-, where Sp represents a spacer moiety.
Furthermore, R ²¹ , R ²² and R ²³ have the same meanings as the respective symbols in formulae 2A to 2C, and the preferred embodiments are also the same.

In formulas 7A to 7C, Sp represents a spacer moiety, R ⁷¹ , R ⁷² , and R ⁷³ represent at least one selected from the group consisting of a hydrogen atom, an alkyl group, and an aryl group, and a plurality of R ⁷¹ , R ⁷² , and R ⁷³ may be the same or different, and the preferred embodiment is the same as that of R ⁵¹ .
Furthermore, ^L2 represents a single bond or -Sp-, where Sp represents a spacer moiety.
Furthermore, R ²¹ , R ²² and R ²³ have the same meanings as the respective symbols in formulae 2A to 2C, and the preferred embodiments are also the same.

In formulas 8A to 8C, Sp represents a spacer moiety, R ⁸¹ , R ⁸² , and R ⁸³ represent at least one selected from the group consisting of a hydrogen atom, an alkyl group, and an aryl group, and a plurality of R ⁸¹ , R ⁸² , and R ⁸³ may be the same or different, and the preferred embodiment is the same as that of R ⁵¹ .
Furthermore, ^L2 represents a single bond or -Sp-, where Sp represents a spacer moiety.
Furthermore, R ²¹ , R ²² and R ²³ have the same meanings as the respective symbols in formulae 2A to 2C, and the preferred embodiments are also the same.

In formulas 9A to 9C, Sp represents a spacer moiety, R ⁹¹ , R ⁹² , and R ⁹³ represent at least one selected from the group consisting of a hydrogen atom, an alkyl group, and an aryl group, and multiple R ⁹¹ , R ⁹² , and R ⁹³ may be the same or different, and the preferred embodiments are the same as those of R ⁵¹ .
Furthermore, ^L2 represents a single bond or -Sp-, where Sp represents a spacer moiety.
Furthermore, R ²¹ , R ²² and R ²³ have the same meanings as the respective symbols in formulae 2A to 2C, and the preferred embodiments are also the same.

The organic ligand can be synthesized by a known method. For example, ACS Appl. Mater. Interfaces 2020, 12, 58277-58286 and ACS Appl. Mater. Interfaces 2014, 6, 9118-9125 describe a method of cross-coupling (Suzuki coupling) a precursor compound of a coordination site and a precursor compound of a redox-responsive site to obtain an organic ligand.
Alternatively, the method described in paragraphs 0014 to 0085 of JP-A-2012-017265 can also be used.

In the above formula, Pd(PPh ₃ ) ₄ is tetrakis(triphenylphosphine)palladium.

In the above formula, Pd(PPh ₃ Cl) ₂ represents dichlorobis(triphenylphosphine)palladium. Note that the above is an example of a method for synthesizing an organic ligand, and the method is not limited to the above, and any method known to those skilled in the art can be used as appropriate.

(Preferred Form of Metallo-Supramolecular Polymer)
The metallo-supramolecular polymer according to the embodiment of the present invention is a polymer formed by alternately linking predetermined cations and organic ligands via coordinate bonds or the like, and preferably contains, for example, the following repeating units.

The following repeating units are formed by coordination bonding of organic ligands and cations in a molar ratio of 1:1 (coordination site:cation = 2:1), and metallo-supramolecular polymers consisting only of these repeating units are linear, and metallo-supramolecular polymers containing these repeating units have a linear structure.

The symbols in formulae 5AP and 5BP have the same meanings as the symbols in formulae 5A and 5B, and the preferred embodiments are also the same.
Furthermore, M represents a cation of the element A as already explained, and the same applies to the following formulae.

The metallo-supramolecular polymer may contain a counteranion, and it is preferable that the charge of the metallo-supramolecular polymer as a whole is compensated.

Examples of counter anions include acetate ions, phosphate ions, chloride ions, phosphorus hexafluoride ions, boron tetrafluoride ions, perchlorate ions, triflate ions, polyoxometalates, and mixtures of these ions.

The symbols in Formula 6AP and Formula 6BP have the same meanings as the symbols in Formula 6A and Formula 6B, and the preferred forms are also the same.

The symbols in Formula 7AP and Formula 7BP have the same meanings as the symbols in Formula 7A and Formula 7B, and the preferred forms are also the same.

The symbols in Formula 8AP and Formula 8BP have the same meanings as the symbols in Formula 8A and Formula 8B, and the preferred forms are also the same.

The symbols in Formula 9AP and Formula 9BP have the same meanings as the symbols below in Formula 9A and Formula 9B, and the preferred embodiments are also the same.

The metallo-supramolecular polymer may also have a branching point derived from the structure of the organic ligand, and the branching point is preferably a trifunctional branching point. Examples of such trifunctional branching points include structures represented by the following formulas 5CP to 9CP.

In formulas 5CP to 9CP, M represents a cation of a specified element, and the wavy line indicates that the subsequent structure is omitted and typically represents the bonding position with the spacer moiety. The other symbols have the same meanings as the symbols in formulas 5C to 9C, and the same applies to preferred embodiments.

Method for synthesizing metallo-supramolecular polymers There are no particular limitations on the method for synthesizing metallo-supramolecular polymers, but examples include a method of preparing and heating a mixture containing an organic ligand and a salt of element A. The mixture may further contain a solvent.

Examples of salts of element A include acetates, sulfates, carbonates, perchlorates, tetrafluoroborates, hexafluorophosphates, and chlorides.
The content ratio of the organic ligand to the salt in the mixture is not particularly limited, but from the viewpoint of allowing the reaction to proceed more easily, the molar content ratio of the content of element A to the content of the organic ligand in the mixture (element A/organic ligand) is preferably 0.5 to 1.5, and more preferably 0.75 to 1.25.

It is preferable that the mixture contains at least one organic ligand selected from the group consisting of an organic ligand represented by formula 4A ("4A ligand"), an organic ligand represented by formula 4B ("4B ligand"), and an organic ligand represented by formula 4C ("4C ligand").

The content ratio of the 4A ligand, 4B ligand, and 4C ligand in the mixture is not particularly limited, but from the viewpoint of the resulting metallo-supramolecular polymer having better solubility in solvents and better mechanical strength, it is preferable that the molar content ratio of the 4C ligand to the sum of the molar content of the 4A ligand, the molar content of the 4B ligand, and the molar content of the 4C ligand in the mixture (4C/4A + 4B + 4C) be 0.01 to 0.2.

The ratio of the organic ligands can be adjusted as appropriate depending on the properties desired for the metallo-supramolecular polymer. For example, from the standpoint of high solvent solubility and ease of forming an electrofluorochromic sheet, it is preferable that the metallo-supramolecular polymer has excellent solubility in the solvent. In this case, it is preferable that the organic ligands contained in the mixture are only 4A ligands and/or 4B ligands.

On the other hand, from the perspective of obtaining an electrofluorochromic sheet with excellent mechanical strength, it is preferable to include a 4C ligand. In this case, the sheet can be formed, for example, by synthesis at a liquid phase interface. That is, an electrofluorochromic sheet can be obtained at the liquid phase interface by inducing a polymerization reaction at the boundary between a solvent (immiscible with water) containing an organic ligand and an aqueous solution containing a cation.

As mentioned above, the branched structure of the organic ligand can be changed as appropriate depending on the properties required of the metallo-supramolecular polymer.

The solvent contained in the mixture is not particularly limited, but examples thereof include water, organic solvents, and mixtures thereof.
The organic solvent is not particularly limited, but examples thereof include ethylene glycol, ethanol, methanol, chloroform, NMP (N-methyl-2-pyrrolidone), dimethylformamide, dichloromethane, and dimethyl sulfoxide.

The content of the solvent in the mixture is not particularly limited, but in general, the solid content in the mixture is preferably 0.0001 to 30% by mass.
The reaction temperature is not particularly limited, but is preferably 60 to 140°C.
The reaction time is not particularly limited, but is preferably 12 to 36 hours.

The method for heating the mixture is not particularly limited, but microwave heating as described in JP 2018-145244 A may be used. Microwave heating provides the metallo-supramolecular polymer with superior structural regularity.

-Method for producing an electrofluorochromic sheet An electrofluorochromic sheet can be produced by preparing a metallo-supramolecular polymer solution, applying the resulting solution onto a substrate (e.g., an electrode) to form a solution layer, and removing the solvent.
Examples of such methods that can be applied include various coating methods such as spin coating, casting, microgravure coating, gravure coating, bar coating, roll coating, wire bar coating, dip coating, slit coating, capillary coating, spray coating, nozzle coating, gravure printing, screen printing, flexographic printing, offset printing, reverse printing, and inkjet printing.
Alternatively, the electrofluorochromic sheet can be formed on a temporary support and then transferred onto the electrode.

The solvent contained in the above solution is not particularly limited, but the same solvents as those already described as organic solvents that can be used in the synthesis of metallo-supramolecular polymers can be used.

There are no particular restrictions on the thickness of the electrofluorochromic sheet and it can be adjusted appropriately depending on the application, but a thickness of 10 nm to 1000 μm is generally preferred.

The present invention will be explained in more detail below based on the following examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below.

[Synthesis of organic ligand ( _LTPA )]
First, the organic ligand [4,4-bis(2,2:6,2-terpyridinyl)benzene]triphenylamine ( _LTPA ) was synthesized according to the following procedure.

4,4'-DBTPA (465 mg, 1.15 mmol), terpyridine boronic acid ester (870 mg, 2 mmol), Pd(PPh ₃ ) ₄ (115 mg, ∼10 mol%), and K ₂ CO ₃ (1.38 g, 10 mmol) were added to DMSO (20 ml), and the mixture was heated to reflux at 110°C for 48 hours.

The resulting reaction mixture was cooled to room temperature, and the product was extracted with a mixture of CH ₂ Cl ₂ /H ₂ O. The pale yellow crude product was purified by column chromatography (basic alumina, CH ₂ Cl ₂ /MeOH 95:5) to obtain 1.15 g (yield 70%) of L _TPA with Rf=0.85.

The structure of L _TPA was determined by nuclear magnetic resonance ( ¹ H-NMR, ¹³ C-NMR) and electrospray ionization mass spectrometry (ESI-MS) spectra.

¹ H-NMR: (400MHz, CD2Cl2) δ (ppm): 8.81 (s, 4H), 8.72-8.67 (m, 8H), 7.98 (d, J = 8.7Hz, 4H), 7.90 (td, J = 7.5, 1.7Hz, 4 H), 7.77 (d, J=17.6Hz, 4H), 7.62 (d, J=8.2Hz, 4H), 7.38-7.30 (m, 6H), 7.20 (t, J=7.5Hz, 6H), 7.09 (t, J=7.3Hz, 1H).

¹³ C-NMR: (CD2Cl2) δ: 156.0, 155.9, 149.6, 149.1, 147.4, 141.3, 137.0, 136.8, 134. 4, 129.5, 128.9, 127.8, 127.7, 127.1, 125.0, 124.2, 124.0, 123.6, 121.2, 118.5.

ESI-TOF-MS (CHCl3/MeOH, 1:1v/v) m/z:found 860.3 (100%), 861.3 (65%), 862.3 (20%) for [M+H] ⁺ (calculated M:859.3 for C60H41N7).

[Synthesis of Metallo-Supramolecular Polymers]
The metallo-supramolecular polymer was synthesized by complexing a ligand ( _LTPA ) with Zn ²⁺ ions in a 1:1 ratio. Hereinafter, the synthesized metallo-supramolecular polymer is referred to as "polyZn-EFC."

First, L- _TPA (200 mg, 0.23 mmol) and zinc acetate (42.7 mg, 0.23 mmol) were placed in a two-neck round-bottom flask and refluxed with ethylene glycol for 24 hours. The bright orange-yellow reaction mixture was cooled to room temperature, and the ethylene glycol was completely removed under reduced pressure. The mixture was then washed 3-4 times with dichloromethane to remove unreacted ligands and red solids. Finally, the mixture was dried overnight in a vacuum to obtain the target product as a pale yellow solid (yield: 95%). Figure 11 shows the ^1H NMR (Nuclear Magnetic Resonance, _CD3OD ) measurement results of polyZn-EFC.

[Preparation of Metallo-Supramolecular Polymer Sheets]
The metallo-supramolecular polymer film was prepared by the following procedure.
First, the solid polymer powder was dissolved in methanol to prepare a polyZn-EFC solution (concentration: 10 mg/ml). The solution was then filtered through a microsyringe filter (0.45 μm, polyvinylidene fluoride) to remove insoluble particles. Finally, the yellow solution was applied to an ITO glass substrate and a film was formed by spin coating. The resulting film was dried in a vacuum oven (50°C).

[Fabrication of Electrofluorochromic Devices]
An electrofluorochromic device was fabricated using a sandwich structure consisting of polyZn-EFC-coated ITO glass as the working electrode, solid polymer gel as the electrolyte layer, and NiHCF (nickel hexacyanoferrate)-coated ITO glass as the counter electrode.

The electrolyte layer was synthesized by the following procedure.
First, a transparent thin electrolyte gel film was prepared by mixing TBAP (tetrabutylammonium perchlorate), PC (propylene carbonate), and PMMA (polymethyl methacrylate, weight average molecular weight: 350,000 (GPC)) in a ratio of 8/46/46 (w/w), and then heated between two glass substrates at 95°C and 40% relative humidity.

Next, the polyZn-EFC coated on the ITO-glass substrate was washed with 0.1 M TBAP/CH ₂ Cl ₂ solution to remove the low molecular weight portion of the polymer, and the working electrode was prepared. The counter electrode was an ITO-glass substrate coated with NiHCF and prepared by spin coating.

The working electrode and counter electrode obtained as described above were sandwiched between a transparent electrolyte gel membrane to form a sandwich structure.

[result]
In polyZn-EFC, Zn ²⁺ ions bind to two terpyridine active sites (coordination sites) of L _TPA in a quasi-octahedral geometry, and two corresponding counter acetate ions ( ⁻ OAc) balance the charge of the polymer backbone.

2 shows the change in the UV-visible _{absorption spectrum} when a Zn(BF ₄ ) ₂ solution (MeOH, c = 5 × 10 ^-4 mol/L) is added to a CH ₂ Cl ₂ solution (c = 1 × 10 ^-5 mol/L) containing L TPA. The solid line is the L _TPA spectrum, and the open double line represents the absorption spectrum when the L _TPA /Zn ²⁺ ion molar ratio is 1:1. The multiple spectra between the two represent the spectrum that changes with the addition of the Zn(BF ₄ ) ₂ methanol solution.

The spectrum of the CH ₂ Cl ₂ solution of L _TPA (solid line) showed two absorption peaks at 279 nm and 368 nm, corresponding to the π-π ^* and n-π ^* transitions, respectively. The solution was colorless.

When a methanol solution of Zn(BF ₄ ) ₂ was added, the intensities of both peaks gradually decreased, and two new peaks at λ _max = 326 nm and 431 nm appeared. These peaks were shifted to higher wavelengths compared with the peaks of the π-π ^* and n-π ^* transitions of L- _TPA , indicating that the coordination site (terpyridine) was coordinately bonded to the metal cation. The intensity of these new peaks saturated when an equimolar amount of Zn ²⁺ ions was added to L- _TPA (Figure 3).
This result suggests that L- _TPA and Zn ²⁺ ions are complexed at a molar ratio of 1:1, that is, a metallo-supramolecular polymer is formed at a molar ratio of 1:1.

FIG. 4 shows the absorption spectrum of the polyZn-EFC film on the ITO glass substrate, and FIG. 5 shows the emission spectrum of the polyZn-EFC film on the ITO glass substrate excited at 425 nm.
As shown in Figure 4, two absorption peaks at wavelengths of 326 nm and 430 nm corresponding to the π-π ^* transition and n-π ^* transition, respectively, were observed in the absorption spectrum of the polyZn-EFC film. At this time, the polyZn-EFC film was yellow in color.

Next, as shown in Figure 5, when excited at 425 nm, a strong emission peak was observed at a wavelength of 587 nm, and bright orange fluorescence was obtained.

Figure 6 shows the results of X-ray photoelectron spectroscopy (XPS) of the polyZn-EFC film. By wide-scanning, peaks corresponding to C1s, N1s, O1s, and Zn2p were observed at binding energies of 285, 400, 534, and 981 eV, respectively, suggesting that these are contained in the polymer skeleton.
The atomic ratio of N (derived from L- _TPA ) to Zn (metal center), qualitatively confirmed by considering the area under the curve (AUC) of N1s and Zn2p, was 7.8:1, which was very close to the ideal value (N/Zn = 7:1). The area under the curve of N1s and Zn2p was also confirmed to be 7.8:1, which was very close to the ideal value (N/Zn = 7:1).

In addition, although the results are not shown, the thermal stability of the polymer, as evaluated by TGA (thermogravimetry), was good up to a temperature range of 550°C.

The electrochemical properties of polyZn-EFC were tested by three-electrode cyclic voltammetry (CV) at a scan speed of 20 mV/s in a nonaqueous (0.1 M TBAP/MeCN) electrolyte system. Figure 7 shows the cyclic voltammogram.

The CV test clearly showed the excellent redox behavior of the polyZn-EFC, with E° _1/2 =0.605 V (vs. Ag/Ag ⁺ ).
The redox characteristics show a forward oxidation peak at 0.69 V (vs. Ag/Ag ⁺ ) and a backward reduction peak at 0.52 V (vs. Ag/Ag ⁺ ), suggesting a reversible conversion between triphenylamine (TPA) and its radical cation (TPA ^·+ ).

An EFC device was fabricated by sandwiching a polyZn-EFC sheet and a transparent ion gel electrolyte layer between a pair of ITO-glass substrates. Under normal conditions, the fabricated device emitted vivid reddish-orange fluorescence (λ _max = 680 nm) when excited by ultraviolet light.

Figure 8 shows the effect of applied voltage on luminescence intensity (excited at 425 nm). In Figure 8, the open double line shows the luminescence intensity when the applied voltage is 0 V, and the solid line shows the luminescence intensity when the applied potential is 1.6 V. The line between these two lines shows the luminescence intensity when the applied potential is changed.

As shown in Figure 8, when a positive potential (1.6 V) is applied to the electrode in contact with the polyZn-EFC sheet, the fluorescence gradually decays and enters the OFF state. Figure 9 is an image showing the corresponding ON/OFF state. Figure 10 is a graph showing the emission intensity at 650 nm when the switch is repeatedly turned ON/OFF (application of 0.0 V and 1.6 V). Figure 10 shows that the ON/OFF operation continues for several cycles, demonstrating good stability.

PolyZn-EFC was successfully synthesized by complexing the redox-active ditopic ligand L- _TPA with Zn(II) ions at a 1:1 molar ratio. The structure of this metallo-supramolecular polymer was confirmed by various spectroscopic and microscopic observations. Titration experiments using UV-visible absorption spectroscopy estimated the molar ratio of Zn(II) ions to L- _TPA in the complexation to be 1:1. This result indicates that L _-TPA , which has two tridentate terpyridine moieties, coordinates with Zn(II) ions in a hexacoordinated structure, resulting in alternating connections between Zn(II) ions and L- _TPA , resulting in polymerization. PolyZn-EFC has excellent processability, and smooth, uniform polymer thin films were obtained by spin-coating a methanol solution of the polymer onto a conductive glass substrate (ITO glass). This polymer film appeared yellow to the naked eye (absorption ~325 nm) and showed bright orange emission under ultraviolet light (emission ~580 nm). Furthermore, the redox behavior of the polyZn-EFC film was investigated by cyclic voltammetry measurement, and it was confirmed that the redox reaction between triphenylamine and the radical cation triphenylamine (TPA⇔TPA ^·+ ) occurred at E° _1/2 = 0.6 V (Ag/Ag ⁺ ).

A solid-state electrofluorochromic device (EFC device) was fabricated using a polyZn-EFC-coated ITO glass working electrode and a NiHCF-coated ITO glass counter electrode sandwiched between the two electrodes and a solid polymer ion gel film. The fabricated EFC device exhibited strong orange-red luminescence (emission ~650 nm) under normal conditions. Upon application of a positive potential (~1.6 V), the fluorescence rapidly disappeared, and at 0.0 V, it re-emitted. This ON/OFF luminescence is related to the redox reaction between TPA and TPA ^·+ , which occurs upon application of an appropriate bias. This metallo-supramolecular polymer, which exhibits reversible changes in metal complex luminescence upon amine redox, may lead to the development of EFC materials for displays.

10: EFC device 11: First electrode 12: Solid electrolyte 13: EFC sheet 14: Second electrode 15: Electrode

Claims (12)

a cation of at least one element selected from the group consisting of iridium, platinum, zinc, and cadmium, which are metal elements of Groups 7 to 12, and an organic ligand;
An electrofluorochromic sheet comprising a metallo-supramolecular polymer formed by alternating bonding forms including at least one selected from the group consisting of coordinate bonds and organometallic bonds,
the organic ligand has two or more coordination sites in one molecule that form, with the cation, at least one luminescent complex selected from the group consisting of a metal complex and an organometallic complex, depending on the bonding form;
having one or more redox responsive sites that cause an oxidation-reduction reaction when an electric potential is applied;
the redox responsive site has at least one nitrogen atom;
In the organic ligand, the coordination site and the redox-responsive site are bonded directly or via a spacer site. 2. The electrofluorochromic sheet according to claim 1, wherein the metal element is zinc . The electrofluorochromic sheet according to claim 1 or 2 , wherein the coordination site comprises at least one structure selected from the group consisting of a nitrogen-containing heterocycle and an aromatic ring capable of forming a metal-carbon bond. 4. The electrofluorochromic sheet according to claim 1 , wherein the redox responsive moiety comprises at least one structure selected from the structures represented by the following formulas 2A to 2C:

(In Formula 1, R ²¹ _and R ²² each independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, L ¹ represents a divalent hydrocarbon group having 1 to 20 carbon atoms, and * represents the bonding position with the spacer moiety.)

(In Formula 2B, R ²³ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, and * in Formula 2B and Formula 2C represents the bonding position with the coordination moiety or the spacer moiety, respectively.) The electrofluorochromic sheet according to claim 4 , wherein the redox responsive site comprises at least one structure selected from the group consisting of a structure represented by formula 2A and a structure represented by formula 2B. 6. The electrofluorochromic sheet according to claim 1 , wherein the spacer moiety comprises an arylene group having 6 to 20 carbon atoms and optionally containing a heteroatom. The electrofluorochromic sheet according to any one of claims 1 to 6 , wherein the metallo-supramolecular polymer contains one or more repeating units represented by the following formulas:









(In each formula, R ⁵¹ , R ⁵² , R ⁶¹ , R ⁶² , R ⁷¹ , R ⁷² , R ⁸¹ , and R ⁸² each independently represent at least one atom or group selected from the group consisting of a hydrogen atom, an alkyl group, and an aryl group, and may be the same or different; L ¹ represents a divalent hydrocarbon group having 1 to 20 carbon atoms; R ²¹ _, R ²² , and R ²³ represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, and may be the same or different; L ² represents a single bond or -Sp-; Sp represents the spacer moiety; and M represents the cation.) The electrofluorochromic sheet according to any one of claims 1 to 7, wherein the spacer moiety is at least one divalent group selected from the group consisting of an alkynylene group having 2 to 20 carbon atoms, an arylene group having 6 to 20 carbon atoms, a heteroarylene group having 6 to 20 carbon atoms, and a group formed by combining these groups. The electrofluorochromic sheet according to any one of claims 1 to 8 , wherein the metallo-supramolecular polymer contains one or more of the trifunctional branch points represented by the following formula:

(In each formula, R ⁵³ , R ⁶³ , R ⁷³ , and R ⁸³ each independently represent at least one atom or group selected from the group consisting of a hydrogen atom, an alkyl group, and an aryl group, and may be the same or different; L ² represents a single bond or -Sp-; Sp represents the spacer moiety; * represents the bonding position with the spacer moiety or the coordination moiety; and M represents the cation.) An electrofluorochromic device comprising a pair of electrodes and the electrofluorochromic sheet according to any one of claims 1 to 9 sandwiched between the electrodes. A metallo-supramolecular polymer comprising one or more repeating units represented by the following formula:










(In each formula, R ⁵¹ , R ⁵² , R ⁶¹ , R ⁶² , R ⁷¹ , R ⁷² , R ⁸¹ , R ⁸² , R ⁹¹ , and R ⁹² each independently represent at least one atom or group selected from the group consisting of a hydrogen atom, an alkyl group, and an aryl group, and may be the same or different; L ¹ represents a divalent hydrocarbon group having 1 to 20 carbon atoms; R ²¹ _, R ²² , and R ²³ represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, and may be the same or different; L ² represents a single bond or -Sp-, Sp represents a spacer moiety, the spacer moiety is a divalent hydrocarbon group having 1 to 20 carbon atoms, and M represents a cation of at least one element selected from the group consisting of iridium, platinum, zinc, and cadmium, which are metal elements of Groups 7 to 12. The metallo-supramolecular polymer according to claim 11 , further comprising one or more of the trifunctional branch points represented by the following formula:

(In each formula, R ⁵³ , R ⁶³ , R ⁷³ , R ⁸³ , and R ⁹³ each independently represent at least one atom or group selected from the group consisting of a hydrogen atom, an alkyl group, and an aryl group, and may be the same or different; M represents a cation of at least one element selected from the group consisting of iridium, platinum, zinc, and cadmium, which are metal elements of Groups 7 to 12; L ² represents a single bond or -Sp-; Sp represents a spacer moiety; the spacer moiety represents a divalent hydrocarbon group having 1 to 20 carbon atoms; and * represents a bonding site.)