Photoresponsive coordination compounds having photo-controllable electron transport and conductive properties, and the manufacture of organic electronic devices and organic resistive memory devices having photoconversion properties

Abstract

A novel photoresponsive coordination compound having at least one photochromic unit in its coordination ligand is disclosed. The photoresponsive coordination compound is demonstrated to be useful as an electroactive material for fabricating organic memory devices and as a photocontrolled electron transport material.

Description

Technical Field

[0001] This invention discloses photoresponsive coordination compounds with photocontrolled electron transport and conductivity properties that can be regulated by light irradiation. These photoresponsive coordination compounds can be used as photoconversion electron transport layers in organic electronic devices and photoconversion electroactive layers in organic resistive storage devices. Background Technology

[0002] Compared to traditional inorganic electronic devices, organic electronic devices have received particular attention in recent decades due to their distinct and unique characteristics, such as high flexibility, simple manufacturing processes, portable size and light weight, and adaptive functionality. Specifically, attempts have been made to incorporate photoresponsive units into organic electronic devices to modulate device performance through light. In particular, photoresponsive materials exhibit intriguing changes in their optical, magnetic, mechanical, or electrical properties depending on the light irradiation. This represents an exciting research area in materials science, where researchers are boldly venturing into a new world of materials whose properties are still unknown but promise beneficial applications in health, industry, agriculture, and other fields. Due to their versatility and relative ease of synthesis, combined with the spatial and temporal control provided by using light as a trigger source, a significant amount of research has focused on polymers with embedded photoresponsive units.

[0003] Recently, incorporating photochromic molecules into organic frameworks has proven to be an effective means of achieving light-controlled behavior. Photochromic compounds have at least two isomers with different physical properties, including electronic properties and refractive index, and can be transformed from one form to the other by irradiation with light of a specified wavelength.

[0004] Among photochromic isomers, diarylethene, spiropyran, and spiroxazine exhibit photochromism via pericyclic reactions and have attracted particular attention due to their versatility in preparing photoresponsive functional molecules. For practical applications in optical recording and other optical devices, both isomers must be thermally stable and exhibit excellent durability against reversible photochromic reactions. Notably, diarylethene outperforms other photochromic groups due to its excellent thermal stability, high fatigue resistance, rapid photoresponsiveness, and high conversion rate between open-ring and closed-ring conformational isomers. Recent studies have shown that incorporating nitrogen- and sulfur-containing heterocycles into the "ethylene" moiety of the diarylethene skeleton enriches the photochromic and photophysical properties, rather than using side groups derived from a bis(thiophene)perfluorocyclopentene core. It has also been demonstrated that by combining phosphorus- and silicon-containing heterocycles, phospholes and siloles can be attached to diarylethene, achieving excellent bistability of both open-ring and closed-ring isomers.

[0005] Meanwhile, research on metal-containing and coordination-unit-containing diarylethenes has been an emerging field over the past decade, demonstrating a promising molecular framework for modulating photochromism. The color of photochromic complexes and coordination compounds can be effectively tuned through coordination with metal centers or main group atoms. More importantly, photoisomerization can be induced using much lower-energy excitation sources through readily available photosensitization. Furthermore, this can improve the stability of photoswitching. Simultaneously, by combining the intrinsic properties of coordination compounds with the photoresponsiveness of photochromic groups, multifunctional smart materials can be readily obtained.

[0006] Given the current use of metal chelates and coordination derivatives in organic electronic devices, it is anticipated that integrating photochromic units onto a framework containing coordination motifs could provide a simple and effective method to modulate the performance of optical switches by simply applying light, without reconstructing the entire molecular framework. This approach should be a significant advantage for the rapid development of organic electronics, particularly in organic resistive memory devices and optical switches, as it can effectively reduce the preparation time and manufacturing costs of new materials. Unlike inorganic storage, whose performance depends on the amount of charge stored in the device, the storage effect in organic resistive memory devices strongly depends on the electrically bistable nature of conductance (resistance), where a low-conductance (off) state switches to a high-conductance (on) state during operation. With the combination of photochromic motifs and coordination frameworks, the variability and functionality of organic resistive memory devices are expected to be greatly enhanced. Summary of the Invention

[0007] To provide a basic understanding of some aspects of the invention, a brief overview of the invention is presented below. This overview is not a comprehensive overview of the invention. It is neither intended to indicate the essential or key elements of the invention nor to define the scope of the invention. Rather, the sole purpose of this overview is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that follows.

[0008] As described herein, a novel class of photoresponsive coordination compounds with photochromic groups integrated into the coordination ligands has been developed. These photoresponsive coordination compounds can be used as electroactive layers for the fabrication of organic resistive memory devices. In particular, these photoresponsive coordination compounds exhibit high electron transport properties and high conductivity upon light irradiation via photoisomerization of the photochromic groups. More importantly, organic resistive memory devices based on these photoconversion coordination compounds exhibit properties exceeding 10... 4 High on / off ratio and long hold time binary storage behavior.

[0009] Furthermore, these novel photoresponsive coordination compounds exhibit photoconversion electron transport properties and conductivity under light irradiation. This photoresponsiveness makes them promising electroactive materials for various organic electronic devices. The design, synthesis, and study of a photoresponsive coordination compound with a photochromic group are described below in one embodiment. This compound exhibits high electron transport properties and high conductivity under light irradiation.

[0010] Another embodiment describes a photoresistive memory device based on a photoresponsive coordination compound, which, upon illumination with light, reversibly undergoes photoisomerization of the photochromic unit. This organic resistive memory device exhibits properties exceeding 10... 4 The high on / off ratio and long retention time exhibit binary storage behavior. The photochromic unit can be, for example, diarylethylene, spiropyran, spiroxazine, or rhodamine. Notably, the electron transport behavior and storage effect of organic memory devices based on such compounds indicate that electron transport and conductivity can be tuned under light irradiation. The photoresponsive coordination compounds described herein provide a simple method for obtaining photoresponsive electron transport materials that can be used as active ingredients in the manufacture of organic electronic devices and organic resistive memory devices. Light conversion storage performance can be readily achieved through light irradiation.

[0011] This article also describes the preparation of photoresponsive coordination compounds having a chemical structure represented by the following general formula (I), which can be used as electroactive materials in organic electronic devices:

[0012]

[0013] in,

[0014] a) X can be oxygen, sulfur, selenium, NR or PR, where R is alkyl, alkylaryl, cycloalkyl, alkoxy, benzyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl or heterocyclic.

[0015] b) A is a cyclic derivative of a substituted or unsubstituted aromatic or heteroaromatic hydrocarbon;

[0016] c) B is a cyclic derivative of a heterocyclic group containing one or more nitrogen atoms, which may be fused with or linked to A by a single bond;

[0017] d) C is a photochromic unit, preferably but not limited to diarylethylene, spiropyran, spiroxazine or rhodamine;

[0018] e)[ML n [] represents a coordination unit containing a metal or main group element M, where L is a ligand;

[0019] f)k is the number of rings in the cyclic derivative, and k is an integer from 0 to 2;

[0020] g)n is the number of ligands, and n is an integer from 0 to 4; and

[0021] h)m is the number of photochromic ligands, and m is an integer from 1 to 4.

[0022] Research has shown that incorporating photochromic units into coordination compounds can effectively modulate the electrical conductivity of the compounds through light irradiation and induce photoresponsive electron transport properties in these compounds. These compounds exhibit thermal stability, high solubility in most organic solvents, and can be easily formed into thin films via thermal deposition or spin coating processes.

[0023] To achieve the foregoing and related objectives, the present invention includes features fully described below and particularly pointed out in the claims. Certain illustrative aspects and embodiments of the invention are set forth in detail in the following description and drawings. However, these are merely examples of a few of the various ways in which the principles of the invention can be employed. Other objects, advantages, and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. Attached Figure Description

[0024] Figure 1 A typical structure of a purely electronic device for measuring the conductivity of photoresponsive coordination compounds is shown.

[0025] Figure 2 A schematic diagram of an organic resistive storage device is shown.

[0026] Figure 3 The changes in the UV-Vis absorption spectrum of compound 2 in degassed benzene under 300 nm excitation are shown.

[0027] Figure 4 The emission spectrum changes of compound 2 in degassed benzene under 337 nm excitation are shown.

[0028] Figure 5 The figure shows the ln(A / A) at which the absorbance of compound 2 at 543 nm decreases in an argon-purged toluene solution at different temperatures. o The graph shows the relationship between absorbance and time; A represents the absorbance at time t. o The solid line represents the initial absorbance; the solid line represents the theoretical linear fit.

[0029] Figure 6 The Arrhenius diagram of the thermal reverse reaction of the closed-ring form of compound 2 in an argon-flushed toluene solution is shown.

[0030] Figure 7The UV-Vis absorbance change of compound 2 in a degassed benzene solution at 543 nm is shown after six cycles of alternating excitation at 300 and 525 nm at 298 K.

[0031] Figure 8 The current density-voltage (JV) curves and photoresponse behavior of the device with an active layer doped with compound 2 are shown.

[0032] Figure 9 The JV curves of a device with an Alq3-doped active layer are shown, with and without light exposure.

[0033] Figure 10 The current-voltage (IV) characteristics of the indium tin oxide (ITO) / active layer / Al device of compound 2 after light irradiation are shown.

[0034] Figure 11 The stability of the light-irradiated ITO / active layer / Al device of compound 2 in the "off" and "on" states under constant stress (1.0V) is shown.

[0035] Figure 12 A scanning electron microscope (SEM) image of a cross-section of a device containing compound 2 under light irradiation is shown. Detailed Implementation

[0036] This paper describes photoresponsive coordination compounds that can switch from a high-resistance state (off state) to a low-resistance state (on state) upon exposure to light. The electron transport properties of these photoresponsive coordination compounds can be light-tuned, and their conductivity increases by at least two times upon light irradiation. Furthermore, these photoresponsive coordination compounds also exhibit thermal stability and fatigue resistance.

[0037] The implementation scheme relates to a new class of photoresponsive coordination compounds with photocontrolled electron transport and conductivity properties. The photochromic unit can be, for example, diarylethene, spiropyran, spiroxazine, or rhodamine. The photoresponsive coordination compounds have the chemical structure shown in general formula (I):

[0038]

[0039] in,

[0040] a) X can be oxygen, sulfur, selenium, NR or PR, where R is alkyl, alkylaryl, cycloalkyl, alkoxy, benzyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl or heterocyclic.

[0041] b) A is a cyclic derivative of a substituted or unsubstituted aromatic or heteroaromatic hydrocarbon;

[0042] c) B is a cyclic derivative of a heterocyclic group containing one or more nitrogen atoms, which may be fused with or linked to A by a single bond;

[0043] d) C is a photochromic unit, preferably but not limited to diarylethylene, spiropyran, spiroxazine or rhodamine;

[0044] e)[ML n [] represents a coordination unit containing a metal or main group element M, where L is a ligand;

[0045] f)k is the number of rings in the cyclic derivative, and k is an integer from 0 to 2;

[0046] g)n is the number of ligands, and n is an integer from 0 to 4; and

[0047] h)m is the number of photochromic ligands, and m is an integer from 1 to 4.

[0048] Ring A is a cyclic derivative, wherein the cyclic structure is independently selected from 5- or 6-membered aromatic hydrocarbons or heteroaromatic hydrocarbons. Aromatic hydrocarbons can be benzene, naphthalene, anthracene, pyrene, fluorene, and their derivatives; heteroaromatic hydrocarbons can be pyridine, pyrazole, imidazole, oxazole, isoxazole, thiazole, isothiazole, isoquinoline, pyrrole, pyrazine, pyridazine, pyrimidine, benzimidazole, benzothiazole, indole, triazole, tetraazole, pyran, oxadiazole, triazine, tetraazine, and their derivatives.

[0049] Ring B is a cyclic derivative, wherein the cyclic structure is independently selected from 5- or 6-membered nitrogen-containing heteroaromatic hydrocarbons or heterocycles known in the art. The heteroaromatic hydrocarbons or heterocycles can be pyridine, pyrazole, imidazole, oxazole, isoxazole, thiazole, isothiazole, isoquinoline, pyrrole, pyrazine, pyridazine, pyrimidine, benzimidazole, benzothiazole, indole, triazole, tetraazole, pyran, oxadiazole, triazine, tetraazine, and their derivatives.

[0050] Ring A and ring B can be unsubstituted or substituted with one or more of the following groups: alkyl, alkenyl, alkynyl, aryl, cycloalkyl, OR, NR2, SR, C(O)R, C(O)OR, C(O)NR2, CN, CF3, NO2, SO2, SOR, SO3R, halogen, aryl, substituted aryl, heteroaryl, substituted heteroaryl, or heterocyclic group, wherein R is independently alkyl, alkenyl, alkynyl, aryl, or cycloalkyl, and additionally or optionally, any two adjacent substitution positions of ring A and B independently form a fused 5- or 6-membered cyclic group. The cyclic group is cycloalkyl, cyclohexaalkyl, aryl, or heteroaryl, and the fused 5- to 6-membered cyclic group may be substituted by one or more of the following groups: alkyl, alkenyl, alkynyl, alkylaryl, cycloalkyl, haloformyl, hydroxyl, aldehyde, formamide, amine, amino, alkoxy, azo, benzyl, carbonate, carboxylic acid ester, carboxyl, ketamine, isocyanate, isonitrile, isothiocyanate, nitrile, nitroso, phosphine, phosphate, phosphonyl, pyridyl, sulfonyl, sulfinyl, mercapto, halogen, aryl, substituted aryl, heteroaryl, substituted heteroaryl, or heterocyclic group.

[0051] C represents the photoresponsive unit. The non-limiting list includes diarylethenes, spiropyrans, spiroxazines, or rhodamine. Examples of diarylethenes include dithienylethylene and stilbenes. Examples of rhodamine include rhodamine 6G, rhodamine B, rhodamine 123, carboxytetramethylrhodamine (TAMRA), tetramethylrhodamine (TMR), isothiocyanate derivatives of tetramethylrhodamine (TRITC), sulforhodamine 101, and rhodamine red. Examples of spiropyrans include substances having the following structures:

[0052]

[0053] Ar1 and Ar2 can represent benzene, naphthalene, anthracene, indolinol, thiophene ring, or other aromatic rings (including heterocycles), and spiropyrans include indolinospiropyrans (where Ar1 represents an indolinol ring). Examples of spiroxazines include the following structures 1-13:

[0054]

[0055] M represents a metal center and a main group element, and its non-restrictive list includes, but is not limited to, aluminum, zinc, gallium, indium, rhodium, manganese, nickel, iron, cobalt, copper, ruthenium, platinum, palladium, tin, vanadium, chromium, iridium, gadolinium, boron, beryllium, lanthanum, etc.

[0056] L can be, independently, but not limited to, alkyl, alkenyl, alkynyl, cycloalkyl, haloformyl, hydroxyl, aldehyde, formamide, amine, amino, alkoxy, benzyl, carbonate, carboxylic acid ester, carboxyl, ketamine, isocyanate, isonitrile, isothiocyanate, nitrile, nitrosyl, phosphine, phosphate ester, phosphonyl, pyridyl, sulfonyl, sulfonyl, sulfinyl, mercapto, halogen, aryl, substituted aryl, heteroaryl, substituted heteroaryl or heterocyclic group, as well as cyclic metallized bidentate ligands and noncyclic metallized bidentate ligands, and quinoline ligands and their derivatives. Among them, cyclic metallized bidentate ligands can be, but not limited to, 2-phenylpyridine, phenylisoquinoline, phenylpyrazole, 7,8-benzoquinoline and their derivatives, and noncyclic metallized bidentate ligands can be, but not limited to, diimine, diamine, diphosphine, dicarboxylate, diketoate, ketoimine ligands and their derivatives. Cyclometallized, non-cyclometallized, and quinoline ligands can be unsubstituted or can be substituted by one or more of the following groups: alkyl, alkenyl, alkynyl, alkylaryl, cycloalkyl, alkoxy, carboxyl ester, carboxyl, nitro, sulfonyl, SOR, SO3R, NR2, SR, CN, CF3, halogen, aryl, substituted aryl, heteroaryl, substituted heteroaryl, or heterocyclic group, wherein R is independently alkyl, alkynyl, alkylaryl, aryl, or cycloalkyl. Cyclometallized and non-cyclometallized ligands can also be extended to tridentate and tetradentate derivatives.

[0057] In this invention, the following terms are used.

[0058] The term "halogen" or "halogen" includes fluorine, chlorine, bromine, and iodine. As used herein, the term "alkyl" includes straight-chain or branched alkyl groups. Alkyl groups contain at least one to eighteen or more carbon atoms and include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, 3-ethylhexyl, etc. Furthermore, the alkyl group may be unsubstituted or substituted with one or more substituents, including alkenyl, alkynyl, alkylaryl, cycloalkyl, haloformyl, hydroxyl, aldehyde, formamide, amine, amino, alkoxy, azo, benzyl, carbonate, carboxyl ester, ketamine, isocyanate, isonitrile, isothiocyanate, nitrile, nitro, nitroso, phosphine, phosphate ester, phosphonyl, pyridyl, sulfonyl, sulfinyl, mercapto, halogen, aryl, substituted aryl, heteroaryl, substituted heteroaryl, or heterocyclic groups.

[0059] As used herein, the term "alkenyl" includes straight-chain and branched alkenyl groups having two to eighteen or more carbon atoms. Alkenyl groups may be unsubstituted or substituted with one or more substituents, including but not limited to alkynyl, alkylaryl, cycloalkyl, haloformyl, hydroxyl, aldehyde, formamide, amine, amino, alkoxy, azo, benzyl, carbonate, carboxyl ester, carboxyl, ketamine, isocyanate, isonitrile, isothiocyanate, nitrile, nitroso, phosphine, phosphate ester, phosphonyl, pyridyl, sulfonyl, sulfinyl, mercapto, halogen, aryl, substituted aryl, heteroaryl, substituted heteroaryl, or heterocyclic groups.

[0060] As used herein, the term "alkynyl" includes straight-chain and branched alkynyl groups having two to eighteen or more carbon atoms. The alkynyl group may be unsubstituted or substituted with one or more substituents, including but not limited to alkyl, alkenyl, alkylaryl, cycloalkyl, haloformyl, hydroxyl, aldehyde, formamide, amine, amino, alkoxy, azo, benzyl, carbonate, carboxyl ester, carboxyl, ketamine, isocyanate, isonitrile, isothiocyanate, nitrile, nitroso, phosphine, phosphate ester, phosphonyl, pyridyl, sulfonyl, sulfinyl, mercapto, halogen, aryl, substituted aryl, heteroaryl, substituted heteroaryl, or heterocyclic groups.

[0061] As used herein, the term "alkylaryl" includes alkyl groups having aromatic groups as substituents. Alkynyl groups may be unsubstituted or substituted with one or more substituents, including but not limited to alkyl, alkenyl, cycloalkyl, haloformyl, hydroxyl, aldehyde, formamide, amine, amino, alkoxy, azo, benzyl, carbonate, carboxyl ester, carboxyl, ketamine, isocyanate, isonitrile, isothiocyanate, nitrile, nitrosyl, phosphine, phosphate ester, phosphonyl, pyridyl, sulfonyl, sulfinyl, mercapto, halogen, aryl, substituted aryl, heteroaryl, substituted heteroaryl, or heterocyclic groups.

[0062] As used herein, the term "cycloalkyl" includes cyclic alkyl groups. Cycloalkyl groups may contain 3 to 7 or more carbon atoms and include cyclopropyl, cyclopentyl, cyclohexyl, etc. Cycloalkyl groups may be unsubstituted or substituted with one or more substituents, including but not limited to alkyl, alkenyl, alkylaryl, cycloalkyl, haloformyl, hydroxyl, aldehyde, formamide, amine, amino, alkoxy, azo, benzyl, carbonate, carboxyl ester, carboxyl, ketamine, isocyanate, isonitrile, isothiocyanate, nitrile, nitroso, phosphine, phosphate ester, phosphonyl, pyridyl, sulfonyl, sulfinyl, mercapto, halogen, aryl, substituted aryl, heteroaryl, substituted heteroaryl, or heterocyclic groups.

[0063] As used herein, the term "alkoxy" includes a straight-chain or branched alkoxy group having one to eighteen or more carbon atoms, and may be unsubstituted or substituted with one or more substituents, including but not limited to alkyl, alkenyl, alkylaryl, cycloalkyl, haloformyl, hydroxyl, aldehyde, formamide, amine, amino, alkoxy, azo, benzyl, carbonate, carboxylic acid ester, carboxyl, ketamine, isocyanate, isonitrile, isothiocyanate, nitrile, nitroso, phosphine, phosphate ester, phosphonyl, pyridyl, sulfonyl, sulfinyl, mercapto, halogen, aryl, substituted aryl, heteroaryl, substituted heteroaryl or heterocyclic group.

[0064] Aromatic groups, whether singly or in combination, comprise carbocyclic aromatic systems containing one, two, or three rings, wherein each ring may be linked together as side groups or may be fused, and may be 5- or 6-membered rings. The aromatic ring may be unsubstituted or substituted with one or more substituents, including but not limited to alkyl, alkenyl, alkylaryl, cycloalkyl, haloformyl, hydroxyl, aldehyde, formamide, amine, amino, alkoxy, azo, benzyl, carbonate, carboxyl ester, ketamine, isocyanate, isonitrile, isothiocyanate, nitrile, nitroso, phosphine, phosphate ester, phosphonyl, pyridyl, sulfonyl, sulfinyl, mercapto, halogen, aryl, substituted aryl, heteroaryl, substituted heteroaryl, or heterocyclic groups.

[0065] Single or combined heteroaryl groups include heterocyclic aromatic systems containing one, two, three or more rings, wherein each ring may be combined in a side-chain or fused manner, and wherein each ring of the system is a 5- or 6-membered ring.

[0066] Heterocyclic compounds refer to 3- to 7-membered rings containing at least one heteroatom. Heterocyclic compounds can be aromatic, including but not limited to pyridine, thiophene, furan, pyrazole, imidazole, oxazole, isoxazole, thiazole, isothiazole, isoquinoline, pyrrole, pyrazine, pyridazine, pyrimidine, benzimidazole, benzofuran, benzothiazole, indole, naphthalene, triazole, tetraazole, pyran, thiazole, oxadiazole, triazine, carbazole, dibenzothiophene, dibenzofuran, indole, and fluorene. Heterocyclic rings can be non-aromatic, including but not limited to aziridine, ethylene oxide, cyclothioethane, oxonicyclopropane, dioxonicyclopropane, azironicyclobutane, oxonicyclobutane, thiobutane, diazabutane, dioxonicyclobutane, dithiobutane, tetrahydrofuran, thiocyclopentane, borononicyclopentane, phosphononicyclopentane, arsolane, stibolane, bismolane, silane, stannolane, piperazine, piperidine, and pyrrolidine. Heterocyclic rings can be unsubstituted or substituted, and substituents can include but are not limited to alkyl, alkoxy, and aryl groups.

[0067] Cyclometallated bidentate ligands are a well-known term in the art, including but not limited to 2-phenylpyridine (ppy), 2-(p-tolyl)pyridine (ptpy), 4-(2-pyridyl)benzaldehyde (pba), 2-(2,4-difluorophenyl)pyridine (fppy), 4-pyridin-2-ylbenzoic acid, 3-pyridin-2-ylbenzoic acid, 2-methyl-6-phenylpyridine, 3-methyl-2-phenylpyridine, 4-methyl-2-phenylpyridine, 5-methyl-2-phenylpyridine, 2-phenylpyridine-3- Carboxylic acids, 2-phenylpyridine-4-carboxylic acid, 6-phenylpyridine-3-carboxylic acid, 2,3-diphenylpyridine, 2,4-diphenylpyridine, 2,5-diphenylpyridine, phenylpyrazole (ppz), 3-methyl-1-phenyl-1H-pyrazole (mppz), 7,8-benzoquinoline (bzq), 2-phenylquinoline (pq), 1-phenylisoquinoline (piq), 2-phenylquinoline, 3-phenylisoquinoline, 3,4-diphenylisoquinoline, and 2-(benzimidazol-2-yl)quinolone (biq).

[0068] Acyclic metallized bidentate ligands are a well-known term in the art, including but not limited to 2,2'-bipyridine (bpy), 4-chloro-2,2'-bipyridine (4-Cl-bpy), 4-carboxy-2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine (4,4'-Me2-bpy), 4,4'-diphenyl-2,2'-bipyridine (4,4'-Ph2-bpy), 4,4'-dicarboxy-2,2'-bipyridine, 5,5'-bis(ethoxycarbonyl)-2,2'-bipyridine, 5-chloro-2,2'-bipyridine, 6-bromo-2,2'-bipyridine, 1,10-phenanthroline (phen), 4-chloro- 1,10-Phenanthroline (4-Cl-phen), 4-methyl-1,10-phenanthroline (4-Me-phen), 5-bromo-1,10-phenanthroline (5-Br-phen), 5-phenyl-1,10-phenanthroline (5-Ph-phen), 5-nitro-1,10-phenanthroline (5-NO2-phen), 4,7-dimethyl-1,10-phenanthroline (4,7-Me2-phen), 4,7-diphenyl-1,10-phenanthroline (4,7-Ph2-phen), 5,6-dimethyl-1,10-phenanthroline (5,6-Me2-phen), 3,4,7,8-tetramethyl-1, 10-Phenanthroline (3,4,7,8-Me4-phen), 3,8-dibromo-1,10-phenanthroline (3,8-Br2-phen), 5,6-dibromo-1,10-phenanthroline (5,6-Br2-phen), 2,9-dichloro-1,10-phenanthroline (2,9-Cl2-phen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (2,9-Me2-4,7-Ph2-phen), dipyrido[3,2-a:2',3'-c]phenazine (dppz), benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (dppn), 2,2' -Bis(diphenylphosphine)-1,1'-binaphthyl (BINAP), 2,2'-bis(di-p-tolylphosphine)-1,1'-binaphthyl, 2,2'-bis[bis(3,5-dimethylphosphine)phospho]-1,1'-binaphthyl, 2,2'-bis(diphenylphosphine)-5,5',6,6',7,7',8,8'-octahydro-1,1'-binaphthyl, 1,2-bis(diphenylphosphine)ethane, 1,3-bis(diphenylphosphine)propane, bis[(2-diphenylphosphine)phenyl]ether, 4,5-bis(diphenylphosphine)-9,9-dimethyl-oxoanthracene, ethylenediamine, oxalate, acetylacetone, hexafluoroacetylacetone, 1,3-diphenyl-1,3-propanedione.

[0069] Quinoline ligands are a well-known term in the art, including but not limited to 8-hydroxyquinoline, 5-chloro-8-hydroxyquinoline, 7-bromo-8-hydroxyquinoline, 2-amino-8-hydroxyquinoline, 2-methyl-8-hydroxyquinoline, 5,7-dimethyl-8-hydroxyquinoline, 8-hydroxyquinoline-7-carboxaldehyde, 8-hydroxyquinoline-2-carboxylic acid, 8-hydroxyquinoline-5-sulfonic acid monohydrate, 2-benzyl-8-hydroxyquinoline, and 8-mercaptoquinoline.

[0070] Benzene includes both substituted and unsubstituted benzene.

[0071] Pyridine includes substituted or unsubstituted pyridine.

[0072] Thiophene includes substituted or unsubstituted thiophenes.

[0073] Furans include substituted or unsubstituted furans.

[0074] Fused thiophenes include substituted or unsubstituted fused thiophenes.

[0075] Pyrazoles include substituted or unsubstituted pyrazoles.

[0076] Pyrimidines include substituted or unsubstituted pyrimidines.

[0077] Pyrroles include substituted or unsubstituted pyrroles.

[0078] Benzimidazoles include substituted or unsubstituted benzimidazoles.

[0079] Benzofurans include substituted or unsubstituted benzofurans.

[0080] Benzothiazoles include substituted or unsubstituted benzothiazoles.

[0081] Indole includes substituted or unsubstituted indole.

[0082] Naphthalene includes substituted or unsubstituted naphthalene.

[0083] Anthracene includes substituted or unsubstituted anthracene.

[0084] Pyrene includes substituted or unsubstituted pyrene.

[0085] Thiazoles include substituted or unsubstituted thiazoles.

[0086] Pyrans include substituted or unsubstituted pyrans.

[0087] Thianans include substituted or unsubstituted thiarans.

[0088] Carbazole includes substituted or unsubstituted carbazole.

[0089] Dibenzothiophene includes substituted or unsubstituted dibenzothiophene.

[0090] Dibenzofurans include substituted or unsubstituted dibenzofurans.

[0091] Fluorene includes substituted or unsubstituted fluorene.

[0092] The present invention is illustrated by the following non-limiting examples. It should be understood that changes and modifications can be made without departing from the scope and spirit of the invention as claimed below. It should also be understood that various theories regarding why the invention works are not intended to be limiting. The compounds described herein are represented throughout by their monomeric structures. As is well known to those skilled in the art, the compounds may also exist as dimers, trimers, larger oligomers, dendritic polymers, or polymers.

[0093] In some embodiments, the photoresponsive coordination compound of formula (I) is prepared with high purity. High purity means one of at least 90% by weight, at least 95% by weight, at least 99% by weight, or at least 99.9% by weight.

[0094] Photoresponsive coordination compounds can be used to form thin films via spin coating, spraying, dip coating, layer-by-layer deposition, inkjet printing, 3D printing, or other known suitable manufacturing methods, enabling photoresponsive electron transport functions and applications in organic resistive storage devices. (Reference) Figure 1 An example of the structure of a conductivity measurement device for a photoresponsive coordination compound is shown in sequence: Aluminum 10 / LiF 11 / Active layer 12 / LiF 13 / Compound 14 / ITO coated glass 15, wherein the active layer is formed by mixing the photoresponsive coordination compound, as a dopant, into the host complex. A suitable host material should be selected to ensure efficient energy transfer between the host material and the dopant material. Ideal examples of the host are m-(N,N'-dicarbazole)benzene (mCP), 4,4'-bis(carbazole-9-yl)-biphenyl (CBP), 4,4',4”-tris(carbazole-9-yl)triphenylamine (TCTA), 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,butylphenyl-1,2,4-triazole (TAZ), p-bis(triphenylsilyl)benzene (UGH2), and PVK. LiF is deposited on an ITO-coated glass or active layer by thermal deposition. An aluminum layer is then thermally deposited on the LiF layer using a shadow mask. In some embodiments, the conductivity of the photoresponsive coordination compound increases dramatically by two times after light irradiation. Unlike conventional methods that modulate conductivity by reconstructing the molecular structure of the target compound, this invention integrates the photochromic unit into the coordination compound, providing a direct and simple method for improving the versatility of the corresponding coordination compound in organic electronic devices.

[0095] Meanwhile, photoresponsive coordination compounds have been shown to be suitable as electroactive components for use in organic resistive memory devices. A typical structure of an organic resistive memory device is shown below. Figure 2 As shown: Aluminum 20 / Active layer 21 / ITO coated glass 22, wherein a photoresponsive compound is used as the active layer material, which is formed by spin-coating on the ITO coated glass, and an aluminum cathode prepared by shadow mask thermal deposition is deposited on top of it. The ITO coated glass has a size of 2cm × 2cm, in which 400 individual devices are fabricated simultaneously. In particular, storage performance has been obtained after irradiating the active layer with light. Up to 10 4 High on / off ratio, threshold voltage of approximately 3.5V, and over 10 4 The invention represents the first example of a resistive memory device based on a coordination compound with photochromic motifs, demonstrating unique photoresponsive storage performance reported to date.

[0096] The following examples illustrate the invention. Unless otherwise stated in the following examples, the specification, and the claims, all parts and percentages are by weight, all temperatures are in degrees Celsius, and all pressures are at or near atmospheric pressure.

[0097] Example 1

[0098] Synthesis and characterization of compounds 1-4

[0099] Compounds 1-4 were synthesized according to the following method. The desired compounds were synthesized by coordinating 8-hydroxyquinoline containing diarylethene with an Al(III) center. For example, triethylaluminum dissolved in heptane was added to a toluene solution (1 M) (0.50 mmol) of 5-(4-(2-(2,5-dimethylthiophen-3-yl)benzo[b]thiophen-3-yl)-5-methylthiophen-2-yl)quinoline-8-ol. The mixture was stirred overnight, and then the solvent was removed under vacuum.

[0100] The aluminum compound was purified by recrystallization from dichloromethane-diethyl ether to obtain the Al(III) compound.

[0101]

[0102]

[0103]

[0104] The characteristic spectral properties of compounds 1-4 are as follows:

[0105] Compound 1

[0106] Yield: 0.60 g, 0.40 mmol, 81%. 1¹H NMR (400MHz, [D6]DMSO, 298K, δ / ppm): δ 2.04–2.08 (m, 9H, –CH3), 2.14–2.16 (m, 9H, –CH3), 2.35–2.37 (s, 9H, –CH3), 6.68–6.64 (m, 3H, thiophene), 6.82–6.86 (m, 3H, quinoline), 6.98–7.00 (m, 3H, thiophene), 7.42–7.46 (m, 8H, phenyl and quinoline), 7.61–7.68 (m, 8H, phenyl and quinoline), 8.01 (m, 3H, phenyl), 8.35–8.43 (m, 3H, quinoline), 8.83 (s, 1H, quinoline), 8.90 (s, 1H, quinoline). HRMS (positive ESI)C 84 H 60 Calculated value of AlN3O3S9: m / z 1473.1936; Measured value: 1473.1919 [M] + Elemental analysis revealed the following (%): C 65.42, H 4.13, N 2.70; C 84 H 60 Calculated values ​​(%) of AlN3O3S9CH2Cl2: C 65.45, H 4.01, N 2.69.

[0107] Compound 2

[0108] Yield: 0.64 g, 0.41 mmol, 82%. 1 ¹H NMR (400MHz, [D₆]DMSO, 298K, δ / ppm): δ 2.01–2.08 (m, 9H, –CH₃), 2.11–2.16 (m, 9H, –CH₃), 2.41–2.44 (s, 9H, –CH₃), 6.85–6.89 (m, 3H, thiophene), 7.02 (d, J=8.0Hz, 3H, quinolinyl), 7.11 –7.17(m, 3H, thiophene), 7.40–7.42(m, 3H, phenyl), 7.56–7.74(m, 12H, phenyl and quinolinyl), 8.01(m, 4H, phenyl and quinolinyl), 8.44–8.57(m, 3H, quinolinyl), 8.73(d, J = 4.2Hz, 1H, quinolinyl), 8.87(d, J = 4.2Hz, 1H, quinolinyl). HRMS(positive ESI)C 84 H 60 Calculated value of AlN3O9S9: m / z 1569.1631; Measured value: 1569.1610 [M] + Elemental analysis revealed the following (%): C 58.43, H 3.94, N 2.63; C 84 H 60Calculated values ​​(%) of AlN3O9S92.5CH2Cl2: C 58.26, H 3.67, N 2.36.

[0109] Compound 3

[0110] Yield: 0.59g, 0.41mmol, 80%. 1 ¹H NMR (400MHz, [D₆]DMSO, 298K, δ / ppm): δ 1.93–1.95 (m, 9H, –CH₃), 2.21–2.23 (m, 9H, –CH₃), 2.41–2.44 (s, 9H, –CH₃), 3.64 (s, 9H, –CH₃), 6.77–6.81 (m, 6H, phenyl and thiophene), 6.96–6 .98(m, 3H, thiophene), 7.12(t, J = 6.8Hz, 3H, phenyl), 7.23(t, J = 6.8Hz, 3H, phenyl), 7.41–7.53(m, 12H, phenyl and quinolinyl), 7.70(s, 1H, quinolinyl), 8.30(s, 3H, quinolinyl), 8.69(s, 1H, quinolinyl), 8.84(s, 1H, quinolinyl). HRMS (positive ESI)C 87 H 69 Calculated value of AlN6O3S6: m / z 1464.3571; Measured value: 1464.3437 [M] + Elemental analysis revealed the following (%): C 69.62, H 5.11, N 5.34; C 87 H 69 Calculated values ​​(%) of AlN6O3S62H2O: C 69.57, H 4.90, N 5.60.

[0111] Compound 4

[0112] Yield: 0.60g, 0.42mmol, 83%. 1 ¹H NMR (400MHz, [D₆]DMSO, 298K, δ / ppm): δ 2.00–2.04 (m, 9H, -CH₃), 2.14–2.19 (m, 9H, -CH₃), 2.34–2.36 (s, 9H, -CH₃), 6.65–6.81 (m, 6H, phenyl and thiophene), 6.94–6.96 (m, 3H, thiophene), 7.16–7.27 (m, 6H, phenyl), 7.31–7.58 (m, 12H, phenyl and quinolino), 7.68 (s, 1H, quinolino), 7.97–8.01 (m, 1H, quinolino), 8.59 (s, 1H, quinolino), 8.72 (s, 1H, quinolino). HRMS (positive ESI) C 84 H 61Calculated value of AlN3O3S9: m / z 1474.2015; Measured value: 1474.2005 [M+H] + Elemental analysis revealed the following (%): C 66.51, H 4.40, N 2.78; C 84 H 60 Calculated values ​​(%) of AlN3O3S92H2O: C 66.77, H 4.27, N 2.78.

[0113] Example 2

[0114] Photochromic properties

[0115] The solution sample of the compound was degassed in a high vacuum line in a degassing cell and stored in 10 cm⁻¹. 3 In a Pyrex round-bottom flask connected to a 1-cm quartz fluorescence cuvette via a side arm, and isolated from the atmosphere by a Rotaflo HP6 / 6 fast-release Teflon stopper, the solution sample underwent rigorous degassing through at least four freeze-pump-thaw cycles prior to measurement.

[0116] When the solution sample is irradiated with UV absorption bands, the initially pale yellow solution changes to various colors. The colored state is thermally stable. Then, irradiation with visible light restores the solution to its original color. The UV-Vis absorbance changes of the compound can undergo reversible cycling. Figure 3 The UV-Vis absorption spectrum changes of compound 2 in degassed benzene under 300 nm excitation are shown. Electron absorption data for both the open-ring and closed-ring forms are summarized in Table 1. In addition to the UV-Vis spectral changes, the emission intensity also decreases due to the photocyclization reaction of the Alq3 compound. Figure 4 This allows the compounds to exhibit photo-switching properties. The quantum yields of photocycloidization and photocycloreversion of the photochromic compounds are summarized in Table 2. The conversion rates under steady-state light are also summarized in Table 2.

[0117] Table 1: Electron absorption data of compounds 1-4 in benzene solution at 298 K

[0118]

[0119]

[0120] Table 2: Photochemical quantum yield and conversion at steady state under light conditions determined in degassed benzene solution at 298 K.

[0121]

[0122] [a] Data obtained with 10% uncertainty.

[0123] [b]Data obtained using 316nm as the excitation source.

[0124] [c] Data obtained using 600 nm as the excitation source.

[0125] Example 3

[0126] The thermal stability of the closed-ring form of the photochromic compound was demonstrated by measuring the absorbance decay of compound 2 at different temperatures in the dark. Figure 5 By plotting the relationship between the thermal reverse reaction rate and temperature at different temperatures, an Arrhenius diagram can be obtained. Figure 6 This figure can be used to determine the activation energy (66.7 kJ mol). -1 The pre-exponential factor for the thermal cyclization reversal of compound 2 (4.1 × 10⁻⁶) and compound 2. 6 s -1 ).

[0127] Example 4

[0128] Fatigue resistance represents another important parameter, commonly used to evaluate the performance of photochromic materials. Photochromic materials may lose their photochromic reactivity through side reactions in the closed-ring form. The fatigue resistance of a compound can be illustrated by alternately exciting the absorption bands of the open-ring and closed-ring forms of the compound and monitoring the changes in UV-Vis absorption at selected wavelengths. Compound 2 is used to illustrate the fatigue resistance of photochromic compounds, such as... Figure 7 As shown.

[0129] Example 5

[0130] Electrochemical properties

[0131] To investigate the electrochemical characteristics, a 0.1 M solution was used in a three-electrode cell. n Bu4NPF6 was used as the supporting electrolyte for cyclic voltammetry testing of compounds 1 to 4 in dichloromethane. Ferrocene salts / ferrocene pairs (Fc...) + / Fc) is used as an internal reference.

[0132] Relative to the standard calomel electrode (SCE), compounds 1–4 exhibited several irreversible oxidation waves at approximately +0.95 to +1.99 V. For the reduction process, one or two quasi-reversible reduction pairs and reduction waves at approximately -1.57 to -1.82 V relative to the SCE were observed. No significant shift in the first oxidation wave was observed after structural modification of the 8-hydroxyquinoline ligand on the peripheral photochromic unit. Compounds 1 and 3, which have no substituents on the pyridyl side of the ligand, showed similar reduction potentials. Meanwhile, a smaller negative reduction pair at approximately -1.57 V was found in compound 2. Compound 4 also exhibited a smaller negative reduction potential, indicating that the substitution of the dithienylethylene unit on the pyridyl side has a significant impact on the electronic properties of the aluminum(III) compounds. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of compounds 1–4 were determined using ferrocene as a reference. The LUMO energy levels of all compounds range from -2.52 to -2.77 eV, while the HOMO energy levels of all compounds range from -5.29 to -5.50 eV. The electrochemical data are summarized in Table 3.

[0133] Table 3: Electrochemical data in dichloromethane solution at 298 K

[0134]

[0135] [a]0.1M n Bu4NPF6 (TBAH) was used as the supporting electrolyte at room temperature; scan rate 100 mV s –1 .

[0136] [b]Anodic peak potential of irreversible oxidation wave.

[0137] [c]E 1 / 2 =(E pa +E pc ) / 2;E pa and E pc These are the peak anode potential and the peak cathode potential, respectively.

[0138] [d] Cathode peak potential of irreversible reduction wave.

[0139] The [e] level is determined with reference to the HOMO level of ferrocene (-4.8 eV vs. vacuum level).

[0140] Example 6

[0141] An apparatus for measuring conductivity according to one embodiment of the present invention is constructed in the following manner:

[0142] a) A transparent anodized ITO-coated borosilicate glass substrate (38mm × 38mm) with a sheet resistance of 30Ω per square meter was ultrasonically treated with commercial detergent Decon 90, rinsed for 15 minutes in deionized water with a resistivity of 18.2 megohms, and then dried in an oven at 120°C for one hour. The substrate was then subjected to a 15-minute UV-ozone treatment in a Jelight 42-220UVO cleaner equipped with a mercury grid lamp.

[0143] b) A 5 nm thick LiF layer is deposited on the ITO-coated glass substrate of step a by thermal evaporation.

[0144] c) Using a Laurell WS-400Ez-6NPP-Lit2 single-wafer spin coater, spin-coat a 60nm thick active layer on the LiF layer from step b at a speed of 6000rpm for 30 seconds, and bake in air at 80°C for 10 minutes, wherein compound 2 is doped into the host material MCP layer at a concentration of 20wt%.

[0145] d) An electron-injected cathode is formed by thermally evaporating a 5 nm thick LiF layer and a 100 nm thick Al layer onto the active layer of step c.

[0146] LiF and Al were prepared by thermal evaporation from a tantalum boat by applying an electric current through the boat. The deposition rate was monitored using a quartz crystal oscillation method and a Sigma SQM-242 quartz crystal card, and the deposition rates of the organic and metal layers were controlled within 0.1–0.2 nm s⁻¹. -1 The J-V characteristics of the device were measured under ambient air conditions using a programmable Keithley model 2420 source meter.

[0147] Example 7

[0148] Figure 8 The J-V curves of the device doped with compound 2 are shown. Compared to the device not exposed to ultraviolet light, a significant decrease in driving voltage was observed under light irradiation. Furthermore, compared to the device without any light exposure, the device under light irradiation exhibited a higher current density at a specific voltage. Notably, the decrease in driving voltage became more significant with increasing exposure time. In addition, the conductivity of compound 2 was found to increase to 7.8 × 10⁻⁶ after light irradiation. -6 mS cm -1 This is for non-irradiation conditions (i.e., 3.7 × 10⁻⁶). -6 mS cm -1 The improvements are identifiable below. However, as... Figure 9As shown, there was no significant difference in the J-V curves obtained from devices containing the original Alq3 compound whether exposed to or not under ultraviolet light. The conductivity of the Alq3 compound containing diarylethene doubled, suggesting that this coordination compound is a promising candidate for photoresponsive electron transport materials.

[0149] Example 8

[0150] The storage device according to one embodiment of the present invention is constructed in the following manner:

[0151] (a) A transparent anodic ITO-coated borosilicate glass substrate (2cm×2cm) was ultrasonically treated for 15 minutes in sequence with deionized water with a resistivity of 18.2 megohms, analytical grade acetone, analytical grade isopropanol and anhydrous ethanol, and then dried in an oven at 120°C for one hour.

[0152] (b) Spin-coat 300 μL of a toluene solution of compound 2 onto the ITO substrate of step a in a two-step spin coating mode, at 500 rpm for 9 seconds and then at 2000 rpm for 30 seconds.

[0153] (c) Place the substrate in an oven at 75°C for 30 minutes to remove solvent residue;

[0154] (d) Place the substrate into the vacuum chamber and evacuate the chamber from 1 bar to 5 × 10⁻⁶ bar. -6 millibar;

[0155] (e) An aluminum layer was deposited on compound 2 from step b by thermal evaporation to form a cathode. The J-V characteristics of the memory devices were measured using a programmable Keithley model 4200 power supply on a four-probe stage. 400 devices were fabricated on each ITO glass substrate, with an effective area of ​​0.25 mm² per cell. 2 .

[0156] Example 9

[0157] The J-V characteristics of compound 2 in fabricated memory devices under both light-free and UV-irradiated conditions were investigated. For devices without any light exposure, the current did not increase, and the device maintained a high-resistance state (off state) over a voltage range of 0 to +5 V. Interestingly, after light irradiation, as... Figure 10 As shown, a sudden increase in current was observed at a switching threshold voltage of approximately 3.5V. This process demonstrates the transition from a low conductivity state to a high conductivity state (on state), with a high on / off ratio exceeding 10. 4 (from 10) –7 Up to 10 –3A). During repetitive voltage scans (scan 2), the device remains in the on state, indicating that it remains on and acquires the storage effect. By applying a reverse bias of the same magnitude as when it transitioned to the on state (scan 3), the memory device cannot return to the off state. The stability of the device under a constant stress of 1V is as follows: Figure 11 As shown. During the measurement process, no significant drop in current was observed in the ON and OFF states for at least 10,000 seconds, indicating that the device exhibits precise control over the ON and OFF states with a low rate of missed readings. Figure 12 As shown, SEM observation of the device's cross-section revealed that the film thicknesses of compound 2 and aluminum were approximately 77 nm and 78 nm, respectively. These findings demonstrate the uniqueness of the diarylethene-containing Alq3 compound in the fabrication of organic memory devices, whose performance is light-controlled.

[0158] These examples should not be construed as limiting the scope of the invention, but rather as providing illustrations of some embodiments of the invention. It should be understood that changes and modifications can be made without departing from the scope and spirit of the invention as claimed below.

[0159] For any number or range of values ​​with a given property, a number or parameter from one range can be combined with another number or parameter from a different range of the same property to produce a range of values.

[0160] Except as described in the operational examples or otherwise, all numbers, values ​​and / or expressions relating to the amount of ingredients, reaction conditions, etc., used in the specification and claims should be understood to be modified by the term "about" in all cases.

[0161] While the invention has been explained in conjunction with certain embodiments, it should be understood that various modifications thereto will be apparent to those skilled in the art upon reading the specification. Therefore, it should be understood that the invention disclosed herein is intended to cover such modifications falling within the scope of the appended claims.

Claims

1. A photoresponsive coordination compound, wherein, The compound is selected from the following structures:

2. An organic storage device comprising, in sequence, an anode, an active layer containing a cathode and the photoresponsive coordination compound of claim 1.

3. The organic storage device according to claim 2, wherein, The photoresponsive coordination compound is thermally evaporated or spin-coated.

4. The organic storage device according to claim 2, wherein, The photoresponsive coordination compound is a material used as the active layer in the preparation of organic storage devices with light-controlled properties.

5. A photoresponsive electron transport material comprising the coordination compound of claim 1.

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