Asymmetrical Photochromic Diarylethene Research Articles

High-contrast multicolour photoswitching based on dithienylethene Schiff base with a hydrazinylquinoline moiety

A new asymmetrical photochromic diarylethene DTE-HQo composed of a 2-hydrazinoquinoline moiety as the binding unit for ions and dithenylethene as a photoswitching trigger was reported. DTE-HQo displayed favourable photochromism upon irradiation with UV/vis light. Its fluorescent behaviour could be efficiently modulated by light, Zn2+, Cd2+ and HSO4−. The binding of Zn2+ induced a strong fluorescence peak at 510 nm in DTE-HQo due to the formation of a 1:2 complex [Zn2+ + 2DTE-HQo], resulting in a notable colour change from dark to intense white emission. Triggered by Cd2+, DTE-HQo formed a 1:1 complex [Cd2+ + DTE-HQo], leading to an enhanced emission intensity by 21-fold with an emission peak red-shifted from 461 nm to 514 nm. Unexpectedly, [Zn2+ + 2DTE-HQo] underwent hydrolysis when stimulated with water, generating a yellow-emitting complex [Zn2+ + DTE-HQo]. This color change easily distinguishes it from Cd2+ complex. Additionally, DTE-HQo showed high selectivity towards HSO4− and exhibited distinct “turn-on” fluorescence with a colour change from dark to bright blue upon stimulation. Moreover, the strong emission complexes of DTE-HQo with Zn2+, Cd2+ and HSO4− could be effectively quenched during the photocyclization process. Therefore, DTE-HQo can serve as an unimolecular multicolour photoswitching chemosensor, offering potential applications as a multifunctional probe for detecting Zn2+, Cd2+ and HSO4−.

Synthesis and Properties of 1-(3,5-Dimethyl-4-isoxazolyl)-2- [2-methyl-5-(3-fluoro-4-chloro)phenyl-3- thienyl]perfluorocyclopentene

An asymmetrical photochromic diarylethene 1-(3,5-Dimethyl-4-isoxazolyl)-2-[2- methyl-5-(3-fluoro-4-chloro)phenyl-3-thienyl]perfluorocyclopentene (1o) was synthesized and its photochromic properties were investigated. Upon irradiation with 297 nm UV light, diarylethene 1o exhibited photochromism in solution and in PMMA film. Moreover, 1o also exhibited obviously fluorescence switches along with the photochromism.

A highly selective fluorescent sensor for Cd2+ based on a new diarylethene with a 1,8-naphthyridine unit

A new asymmetrical photochromic diarylethene has been synthesized by using 1,8-naphthyridine as a functional group and perfluorodiarylethene as photoswitching unit via a peptide bond linkage, and its molecular structure was characterized by single crystal X-ray diffraction analysis. The compound exhibited favorable photochromism upon irradiation with UV/vis light, and its fluorescent behaviour could be efficiently modulated by light, base/acid, and metal ion in THF. The deprotonated derivative of the diarylethene also showed good photochromism, and displayed remarkable “turn-on” fluorescence response during photocyclization process. Furthermore, the diarylethene was highly selective toward Cd2+ with an obvious fluorescent color change from dark to bright green in THF. Finally, a logic circuit was fabricated with four inputs of the combinational stimuli of UV/vis and Cd2+/EDTA, and one output of fluorescence intensity.

A highly selective fluorescence probe for Al3+ based on a new diarylethene with a 6-(hydroxymethyl)picolinohydrazide unit

A new asymmetrical photochromic diarylethene with a 6-(hydroxymethyl)picolinohydrazide unit has been synthesized. Its multichromism behaviors induced by base/acid and light were investigated. The compound exhibited high selectivity and sensitivity toward Al3+, and the fluorescence intensity of the diarylethene was remarkably enhanced by 95-fold and the emission peak was blue-shifted from 585 nm to 542 nm with a concomitant color change from dark to bright green triggered by Al3+. The complexation-decomplexation reaction between the diarylethene and Al3+ was reversible with a binding constant of 1.22 × 104 L mol−1, and the detection limit was determined to be 2.88 × 10−8 mol L−1. Our experimental results demonstrated that the diarylethene could be served as a selective fluorescent sensor for the recognition of Al3+ with high sensitivity and selectivity in methanol.

A novel sensitive sensor for Cu2+ and multi-switch based on a diarylethene with a 2-(2′-hydroxyphenyl)benzothiazole unit

A new asymmetrical photochromic diarylethene with a 2-(2′-hydroxyphenyl)benzothiazole unit has been synthesized. It underwent reversible cyclization and cycloreversion reactions upon alternating irradiation with lower energy UV (297 nm, 25 μW/cm2) and visible light, while it could induce intramolecular proton transfer reaction upon irradiation with higher energy UV light (254 nm, 92 μW/cm2) with distinct color change. The absorption maximum of the closed-ring isomer was redshifted from 539 nm to 660 nm and the color changed from purple to cyan when the diarylethene was stimulated with base. Furthermore, addition of acid enhanced its fluorescence intensity by 5.5 fold and the emission peak was blueshifted from 596 nm to 570 nm with a concomitant color change from light orange to bright green, while base could efficiently quench its fluorescence intensity. Finally, the diarylethene was highly selective towards Cu2+ with significant absorption and fluorescence changes, which makes the ‘naked-eye’ detection of Cu2+ possible.

Synthesis and Properties of 1-(2-methyl-3-benzothienyl)-2-[2-methyl-5-(3-trifluoromethyl)-3-thienyl]perfluorocyclopentene

A novel asymmetrical photochromic diarylethene 1-(2-methyl-3-benzothienyl)-2-[2-methyl-5-(3-trifluoromethyl)-3-thienyl] perfluorocyclopentene was synthesized and its photochromic and fluorescent properties were also investigated. The compound exhibited remarkable photochromism, changing from colorless to red after irradiation with UV light and the open-ring isomer of the diarylethene 1 exhibited relatively remarkable fluorescence in hexane solution. The cyclization/cycloreversion process of the compound was determined to be the zeroth/first order reaction.

Synthesis and Properties of 1-(2-Cyano-1,5-Dimethyl-4-Pyrryl)-2-{2-Methyl-[5-(4-Methylene-Hydroxyl)Phenyl]-3-Thienyl}Perfluorocyclopentene

A new asymmetrical photochromic diarylethene 1-(2-cyano-1,5-dimethyl-4-pyrryl)-2-{2-methyl-[5-(4-methylene-hydroxyl) phenyl]-3-thienyl} perflu-orocyclopentene (1o) was synthesized and its photochromic properties were investigated systematically. Upon irradiation with 297 nm UV light, 1o exhibited photochromism in acetonitrile solution and in a PMMA amorphous film. The kinetic experiments showed that the cyclization and cycloreversion processes were zeroth and first order reaction, respectively. In addition, diarylethene 1o also exhibited obvious fluorescence switches along with the photochromism.

Synthesis and Properties Study of 1-[2-Methyl-5-(3-Trifluoromethyl)-3-Thienyl]-2-[2-Methyl-5-(9-Phenanthrene)-3-Thienyl]Perfluorocyclopentene

An asymmetrical photochromic diarylethene 1-[2-methyl-5-(3-trifluoromethyl)-3-thienyl]-2-[2-methyl-5-(9-phenanthren-e)-3-thienyl] perfluorocyclopente-ne was synthesized and its photochemical properties were investigated in detail. The results demonstrated that the compound has excellent photochromic properties and good fluoresence. The cyclization/cycloreversion process of the compound was determined to be the zeroth/first order reaction.

Effects of solvents on the growth of an asymmetrical photochromic diarylethene crystal

An asymmetrical photochromic diarylethene with one pyridine unit was synthesized, which could have two types of crystals controlled through the evaporation of either an ether solution or a hexane/chloroform (V = 1:1) solution at room temperature, respectively. The obtained open-ring isomer and closed-ring isomer of the diarylethene could be interconverted in solution, in a solid film, and even in the crystalline phase via alternating irradiation with UV and visible light. The diarylethene exhibited proton-controlling fluorescence switching behavior through alternating the stimulation of trifluoroacetic acid and triethylamine. Its fluorescence intensity could also be modulated reversibly through alternating irradiation with UV and visible light. Thus, the diarylethene could be used as a multi-addressable fluorescence switch when triggered with light and acid/base. Cyclic voltammograms with an oxidation wave of the closed-ring isomer was clearly observed at 0.82 V.

Research on Photochromic Materials with Synthesis and Properties of 1-(3,5-Dimethyl-4-isoxazolyl)-2-[2-methyl-5-(<i>p</i>-ethoxyphenyl)-3-thienyl]perfluorocyclopentene

An asymmetrical photochromic diarylethene 1-(3,5-Dimethyl-4-isoxazolyl)-2-[2-methyl-5-(p-ethoxyphenyl)-3-thienyl] perfluorocyclopentene (1o) was synthesized and its photochromic properties were investigated. Upon irradiation with 297 nm UV light, 1o exhibited photochromism in hexane solution. The kinetic experiments showed that the cyclization and cycloreversion processes were zeroth and first order reaction, respectively. Moreover, diarylethene 1o also exhibited obviously fluorescence switches along with the photochromism.

Synthesis and Properties of 1-(2,4-Dimethyl-5-thiazolyl)-2-(2-methyl-5-(2-methyl)-3-thienyl)perfluorocyclopentene

An asymmetrical photochromic diarylethene 1-(2,4-dimethyl-5-thiazolyl)-2-(2-methyl-5-(2-methyl)-3-thienyl) perfluorocyclopentene (1o) was synthesized and its photochromic properties were investigated. Upon irradiation with 297 nm UV light, 1o exhibited photochromism in solution and in PMMA film. The kinetic experiments showed that the cyclization and cycloreversion processes were zeroth and first order reaction, respectively. Moreover, diarylethene 1o also exhibited obviously fluorescence switches along with the photochromism.

Synthesis and Properties of 1-[2,5-dimethyl-3-thienyl]-2-[2-methyl-5-(<i>p</i>-N,N-dimethylaminophenyl)-3-thienyl]perfluorocyclopentene

An asymmetrical photochromic diarylethene 1-[2,5-dimethyl-3-thieny-2-[2-methyl-5-(p-N,N-dimethylaminophenyl)-3-thienyperfluorocyclopentene was synthesized and its photochemical properties were investigated in detail. The results demonstrated that the compound has excellent photochromic properties and good fluoresence. The cyclization/cycloreversion process of the compound was determined to be the zeroth/first order reaction. The fluorescence intensity increased with increasing concentration, but when the concentration increased enough high, the fluorescence intensity decreased rapidly.

Synthesis and Properties of 1-[2-trifluoromethylpheny-2-[2-methyl-5-(3,5-difluorophenyl)-3-thienyl] perfluorocyclopentene

An asymmetrical photochromic diarylethene 1-[2-trifluoromethylpheny-2-[2-methyl-5-(3,5-difluorophenyl)-3-thienyperfluorocyclopentene (1o) was synthesized and its phtochromic, fluorescent properties in both solution and PMMA films were investigated in detail. This compound exhibited remarkable photochromism, upon irradiation with 297 nm UV light, the colorless solution of 1o turned to plum with a new visible absorption band centered at 544 nm (ε =3.75 × 103 L mol-1 cm-1) attributable to the closed-ring isomer 1c.The fluorescence intensity of diarylethene decreased dramatically along with the photochromism from open-ring isomer to closed-ring isomer in PMMA films and in hexane. The emission intensity of diarylethene 1o in a photostationary state was quenched to ca. 64% in hexane and 27% in PMMA films.

Photochromism and Optical Recording of a Novel Diarylethene Bearing Phenanthrene Unit

Photochromic molecules are part of a large class of materials in which light stimulus not only induces a color variation but also affects other physicochemical properties. In the paper, an asymmetrical photochromic diarylethene, 1-(2,4-dimethyl-3-thiazole)-2-[2-methyl-5-(10-phenanthrenyl)-3-thienyPerfluorocyclopentene was synthesized and its photochromic and fluorescent properties were systematically investigated. The compound exhibited remarkable photochromic, changing from colorless to OrangeRed after irradiation with UV light both in solution and in PMMA film. In addition, its fluorescence property was also discussed. When irradiation with UV light, the fluorescence intensity declined remarkably. The results showed that the diarylethene exhibited a relatively strong fluorescence switch along with the photochromism from open-ring isomer to closed-ring isomer. Using this diarylethene 1a as optical storage was performed successfully.

Synthesis, kinetics and application for optical recording of a new asymmetrical photochromic diarylethene

A novel photochromic diarylethene was synthesized and its photochromic, fluorescence and kinetics properties were investigated detail. This compound exhibited remakable photochromism, changing from colorless to blue after irradiation with UV light both in solution and in PMMA amorphous film. In hexane, the kinetic experiments showed that the cyclization /cycloreversion process of the compound was determined to be the zeroth/first reaction, respectively. Finally, The results demonstrated that the diarylethene compound had attractive properties for high density optical storage.

Electron-donating methoxyl group position effect on properties of diarylethene derivatives having a pyrazole unit

New types of asymmetrical photochromic diarylethene derivatives having a pyrazole unit, namely 1-[1,3,5-trimethyl-1-pyrazol-4-yl],2-[2-methyl-5-(4-methoxylphenyl)-1-thien-3-yl]perfluorocyclopentene (1a), 1-[1,3,5-trimethylpyrazol-4-yl],2-[2-methyl-5-(3-methoxylphenyl)-1-thien-3-yl] perfluorocyclopentene (2a), 1-[1,3,5-trimethyl-pyrazol-4-yl],2-[2-methyl-5-(2-methoxylphenyl)-1-thien-3-yl]perfluorocyclopentene (3a), and 1-[1,3,5-trimethyl-pyrazol-4-yl],2-[2-methyl-5-phenyl-1-thien-3-yl]perfluorocyclopentene (4a), were synthesized. Their optical and electrochemical properties, such as photochromism, photochromic cyclization–cycloreversion kinetics, and fluorescence and electrochemical properties were investigated in detail. The results show that all of these compounds have good photochromism, high cycloreversion quantum yield, and relatively strong fluorescence. Their cyclization-cycloreversion processes were determined to be zeroth to first order reactions. The oxidations of diarylethenes 1a–4a were initiated at 0.73, 1.11, 0.79, and 1.03 V, respectively. Furthermore, introduction of the electron-donating methoxyl group at different positions of the terminal phenyl ring was found to strongly influence these optical and electrochemical properties.Key words: photochromism, diarylethene, electron-donating group, optical and electrochemical properties.