Unsymmetrical Diarylethene Research Articles

Mechanistic Aspects of Photoinduced Rearrangement of 2,3-Diarylcyclopentenone Bearing Benzene and Oxazole Moieties.

Photoinduced rearrangement of diarylethenes to naphthalenes or isoelectronic benzoannulated heterocycles is a novel reaction in preparative organic photochemistry. Recently it was shown that unsymmetrical diarylethenes containing benzene and oxazole derivatives efficiently undergo this transformation leading to amide derivatives of naphthalene. Mechanistic study of skeletal rearrangement for a typical representative of these compounds, namely 3-(5-methyl-2-phenyl-1,3-oxazol-4-yl)-2-phenylcyclopent-2-en-1-one, was performed by stationary and laser flash photolysis as well as density functional theory (DFT) calculations. The mechanism of the rearrangement was found to comprise several thermal stages. Both singlet and triplet states of the initial compound can be transformed to the reaction product, which results in the dependence of the quantum yield vs concentration of dissolved oxygen. Three reactive intermediates were registered in the laser flash photolysis experiment; the predicted structures were in accordance with DFT calculations of the electronic absorption spectra. In addition to the previously proposed mechanism of skeletal rearrangement based on a sigmatropic shift of hydrogen, two new parallel pathways based on formation of a carbanion/carbocation were determined.

Spectral properties and structure of unsymmetrical diarylethenes based on thiazole ring with hydrogen at the reactive carbon

Six new photoactive unsymmetrical diarylethenes bearing thiazole ring with hydrogen at the reactive carbon atom have been synthesized. Their structures have been studied by DFT calculations and X-ray crystallography. All compounds undergo irreversible photochemical transformations under irradiation with ultraviolet light, proceeding through the photocyclization stage. It has been found that only some normal (thiophene, imidazole and pyrazole derivatives) and inverse type (oxazole derivative) diarylethenes form colored photoinduced isomers under UV. In polar acetonitrile these intermediates show relatively fast irreversible thermal reaction, while in nonpolar toluene slow cycloreversion to initial diarylethenes is the predominant process of these species.

A multi-responsive diarylethene-rhodamine 6G derivative for sequential detection of Cr3+ and CO32−

A new unsymmetrical diarylethene derivative (1o) with rhodamine 6G as a functional group has been designed and synthesized. It displayed good physicochemical properties induced by lights and chemical stimuli. 1o could sensitively detect towards Cr3+ with a 1:1 stoichiometry, and exhibit an obviously fluorescence (from dark to light cyan) and color (from colorless to pink) changes during the recognition process. The limit of detection was determined to be 27 nM and 8.5 nM via UV/vis and fluorescence methods, respectively. More importantly, the resulting complex 1o-Cr3+ (1o') could be served as a potential fluorescent probe to selectively and sensitively recognize toward CO32−, the limit of detection was determined to be 0.88 μM and 0.26 μM via UV/vis and fluorescence methods, respectively. Moreover, the quenching of fluorescence intensity can reach 95% due to the perfect FRET processes between the excited open-ring rhodamine 6G moiety and the closed-ring diarylethene unit.

Photochromism of new unsymmetrical diarylethenes with a quinoline moiety

Three unsymmetrical diarylethenes with a 6-membered quinoline moiety were synthesized to investigate the effects of the substituents on their photochromism, and fluorescence, and the structure of one diarylethene was determined by single crystal X-ray diffraction analysis. Quinoline was connected directly to the central perfluorocyclopentene ring as an aryl moiety and available to participate in photoisomerization reaction in solution, amorphous films, and crystalline phase. These diarylethenes exhibited good photochromism with excellent thermal stability and obvious fatigue resistance. The electron-donating methoxy group could enhance the absorption maxima of closed-ring isomers and the quantum yields of cyclization and cycloreversion, but the electron-withdrawing trifluoromethyl had an opposite effect. In addition, they functioned as notable fluorescence switches in both solution and polymethylmethacrylate films, and the trifluoromethyl group and the methoxy group both increased the emission intensity. The results revealed that the quinoline moiety and substituents played a vital role in the process of photoisomerization reactions for these diarylethenes.

Synthesis, Photochromism Properties of 1-(1,5-Dimethyl-2-Pyrrolecarbonitrile)-2-[2-Methyl-5-(4-Aminomethyl)Phenyl-3-Thienyl] Perfluorocyclopentene

A new unsymmetrical diarylethene derivative 1-(1, 5-dimethyl-2-pyrrolecarbonitrile) -2-[2-methyl-5-(4-aminomethyl) phenyl-3-thienyl] perfluorocyclopentene (1o) was designed and constructed successfully. Its optoelectronic properties have been discussed systematically, such as photochromic, kinetics experiments in acetonitrile solution and PMMA.

Effects of the Peripheral Heteroaryl Substituents on the Photochromism of New Pyridine-Containing Diarylethenes

Three new unsymmetrical pyridine-containing diarylethenes with a variable peripheral heteroaryl unit were synthesized and their structures were determined by single-crystal X-ray diffraction analysis. The substituent effects of variable heteroaryl groups on the photochromic and fluorescence properties were systematically discussed. Thienyl and thiazyl could effectively enhance the cyclization quantum yields and photoconversion ratios in the photostationary state, as compared to the phenyl group. However, they had no obvious effect on the fluorescence behaviors. Moreover, X-ray structural analysis revealed that the N···S heteroatom-contact interactions resulted in a higher cyclization quantum yield, which may be ascribed to the effective stabilizing ability on the photoreactive formations in diarylethenes with a thienyl/thiazyl unit.

Photochromism of new unsymmetrical diarylethenes with an indazole moiety

A new class of photochromic diarylethenes with an indazole moiety has been firstly synthesized, and their photochromic and fluorescence properties have been investigated. The indazole moiety was connected directly to the central cyclopentene ring as one heteroaryl unit and availably participated in the photoinduced cyclization reaction in solution, amorphous film, as well as in the crystalline phase. These diarylethenes exhibited excellent photochromism with good thermal stability and remarkable fatigue resistance. They also functioned as notable fluorescence switches in both solution and amorphorous films. In addition, the different substituents at the para-position of the terminal benzene ring had a significant effect on their properties: the electron-donating methoxy group could enhance the quantum yields of cyclization and cycloreversion and fluorescence quantum yield, but the electron-withdrawing trifluoromethyl had opposite effect.

Synthesis and Characterization of Unsymmetrical Diarylethene Based on Phenylpentane

An unsymmetrical photochromic diarylethene, 1-[2-methyl-3-benzothiophene]-2-[2-methyl-5-(4-pentylphenyl)-3-thienyl] perfluorocyclopentene (1a), has been synthesized, and its properties including photochromism and fluorescence have been investigated. The results showed that this compound undergo reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light in solution.

ChemInform Abstract: Synthesis and Photochromism of Novel Unsymmetrical Diarylethenes with an Azaindole Unit.

AbstractThe synthesized unsymmetrical photochromic diarylethenes exhibit fluorescence in solution and in PMMA films.

Research on Photochromic Materials with Synthesis and Properties of a New Unsymmetrical Diarylethene 1-(2-cyano-1,5-dimethyl-4-pyrryl)-2-{2-methyl-[5-(4-methylene-bromine)phenyl]-3-thienyl} Perfluorocyclopentene

A new photochromic diarylethene having a pyrrole unit, which is named 1-(2-cyano-1,5-dimethyl-4-pyrryl)-2-{2-methyl-[5-(4-methylene-bromine) phenyl]-3-thienyl} perfluorocyclopentene, was designed and constructed successfully. And its properties have been discussed systematically, including photochromic, fluorescence switch and kinetics experiments in acetonitrile solution. The results showed that its photochromic behaviors could be modulated by UV/Vis light, changing from colorless to blue in acetonitrile solution. What is more, the kinetic experiments illustrated that the cyclization/cycloreversion process of this compound was determined to be the zeroth/first reaction.

Research on Photochromic Compounds with Synthesis and Properties of a Novel Unsymmetrical Diarylethene with a Benzothiophene and a Pyrrole Group

A new unsymmetrical photochromic diarylethene 1o, which is named [1-(2-methyl-benzothiophene)-2-(2-cyano-1,5-dimethyl-4-pyrryl)]perfluorocyclopentene, was synthesized. We used it to accomplish recording by optical storage technology as memory medium. Then its photochromic both in hexane solution and in PMMA film and kinetics experiment were investigated in detail. The result indicated that this diarylethene had good thermal stability and exhibited reversible photochromism, changing the color from colorless to violet in hexane solution upon appropriate irradiation with 297 nm UV light, respectively. What is more, the kinetic experiments illustrated that the cyclization/cycloreversion process of this compound was determined to be the zeroth/first reaction. The results demonstrated that the unsymmetrical diarylethene compound 1o, which we have synthesized, had attractive properties for potential application in optical storage.

Research on Photochromic Compounds with Efficient Synthesis and Photochromic Properties of 1-(2-methyl-5-chlorine-3-thienyl)-2-[2-methyl -5-(4-chlorophenyl)-3-thienyl] Perfluorocyclopentene

A novel unsymmetrical diarylethene derivative bearing both phenyl and thiophene moieties, in which two chlorine groups were separately substituted at thiophene and the para-positions of the terminal phenyl ring, were synthesized. Its photochemical , fluorescence properties were investigated systematically both in solution and PMMA amorphous film. The results showed that this compound exhibited reversible photochromism, changing from colorless to purple after irradiation with 313 UV light both in solution and in PMMA amorphous film. Also, it exhibited remarkable fluorescence switching in the solid state.

Synthesis and Properties of a Novel Unsymmetrical Diarylethene{1-[2-methyl-5-(10-phenanthrenyl)-3-thienyl]-2-{2-methyl-5-[4-(2-(1,3-dioxolane))phenyl]-3-thienyl}} Perfluorocyclopentene

A novel unsymmetrical isomeric photochromic diarylethene based on phenanthrene unit, {1-[2-methyl-5-(10-phenanthrenyl)-3-thienyl]-2-{2-methyl-5-[4-(2-(1,3-dioxolane)) phenyl]-3-thienyl}} perfluorocyclopentene (1o), was designed and synthesized. Its properties were investigated in detail, including photochromic, kinetics and fluorescent. The results showed that the compound exhibited excellent photochromism, changing from colorless to violet after irradiation with UV light in solution. What is more, the kinetic experiments illustrated that the cyclization/cycloreversion process of this compound was determined to be the zeroth/first reaction. Furthermore, the fluorescence intensity of the photochromic diarylethene1odeclined dramatically.

Synthesis and Properties of a New Unsymmetry Diarylethene 1-{2-methyl-[5-(4-methylene-bromine)phenyl]-3-thienyl}-2-[2-methyl-5-(10-phenanthrenyl)-3-thienyl]perfluorocyclopentene

A new photochromic diarylethene based on a phenanthrene, which is named 1-{2-methyl-[5-(4-methylene-bromine) phenyl]-3-thienyl}-2-[2-methyl-5-(10-phenanthrenyl)-3-thienyl] perfluorocyclopentene 1o, was designed and constructed successfully. We used it to accomplished recording by optical storage technology as memory medium. And its properties have been discussed systematically, including photochromic both in dichloromethane solution and in PMMA film and kinetics experiments. The result indicated that its photochromic behaviors could be modulated by UV/Vis light, changing between colorless and blue in dichloromethane solution and in PMMA film, respectively. What is more, the kinetic experiments illustrated that the cyclization/cycloreversion process of this compound was determined to be the zeroth/first reaction. In addition, the results demonstrated that the unsymmetrical diarylethene compound 1o, which we had synthesized, had attractive properties for potential application in optical storage.

Synthesis, crystal structure and photochromism of new diarylethenes with a benzene moiety

Three unsymmetrical diarylethenes with both thiophene and benzene moieties were synthesized. Their crystal structures and photochromic features were investigated systematically to elucidate the substituent effects of the terminal phenyl group on photochromism. Computational studies were performed to provide further insight into their frontier molecular orbitals and spatial distributions of electronic density. Each compound exhibited favorable photochromism in hexane and functioned as notable fluorescent photo-switches with fluorescence quenching efficiency of ∼96% induced by the intensity change of UV/vis light. Among the three diarylethenes, the cyano group on the terminal phenyl group significantly decreased the distance of the two reactive carbon atoms and strengthened the intermolecular hydrogen bond stacking interactions, resulting in improved stability in crystal state. Furthermore, it exhibited a red-shifted absorption maximum, an enhanced molar absorption coefficient, cyclization quantum yield, and fluorescence quantum yield in solution.

Synthesis and photochromism of novel unsymmetrical diarylethenes with an azaindole unit

A new class of unsymmetrical photochromic diarylethenes with an azaindole moiety has been firstly synthesized. Their properties, including photochromism, crystal structure, as well as fluorescence, were investigated systematically. The azaindole was connected directly to the central cyclopentene ring as a heteroaryl moiety and available to participate in the photoisomerization reaction. Each of the diarylethenes exhibited favorable photochromism, good thermal stability, remarkable fatigue resistance, and notable fluorescence switches in both solution and solid media. The substituents at the para-position of the terminal benzene ring affected evidently their properties: the electron-donating methoxy could be effective to enhance the cyclization quantum yield, while the electron-withdrawing cyano could shift the absorption maximum to a longer wavelength in both hexane and solid film. The results revealed that the introduction of azaindole moieties and different substituents played an important role in the photoisomerization process of these diarylethenes.

Photochromism of new unsymmetrical diarylethenes based on the hybrid of azaindole and thiophene moieties

A new class of photochromic diarylethenes with both azaindole and thiophene moieties were synthesized to investigate the effects of the substituents on their photochromic behaviors, and their structures were determined by single crystal X-ray diffraction analysis. The azaindole moiety was connected directly to the central cyclopentene ring as a heteroaryl moiety to participate the photoisomerization reaction in solution, solid amorphous films, and the single crystalline phase. Each of the diarylethenes exhibited remarkable fluorescent photo-switches in both solution and solid media. The electron-donating substituents significantly enhanced their cyclization quantum yields, while the electron-withdrawing groups greatly increased the molar absorption coefficient of their closed-ring isomers. Cyclic voltammetry studies indicated that the band-gaps of diarylethenes with an azaindole notably increased when going from electron-donating substituents to electron-withdrawing substituents. The results revealed that the azaindole moiety and substituents played a vital role in the process of photoisomerization reactions for these diarylethenes.

A multi‐addressable molecular switch based on a novel diarylethene with an imidazo [4,5‐f] [1,10] phenanthroline unit

A novel unsymmetrical diarylethene with an imidazo [4,5‐f] [1,10] phenanthroline unit has been synthesized, and its properties including photochromism and fluorescence have been investigated. It showed favorable photochromism and functioned as notable fluorescence switches by photoirradiation in both solution and a poly (methylmethacrylate) film. Moreover, the interaction between the phenanthroline unit of its closed‐ring isomer with trifluoroacetic acid caused a notable change in its absorption, accompanied by an evident color change from magenta to slateblue. Its fluorescence could be modulated by trifluoroacetic acid and triethylamine. By adding enough amount of trifluoroacetic acid in chloroform, its emission peak hypochromatic shifted from 501 nm to 456 nm, and the intensity increased significantly with a concomitant change of color from bright cyan to bright blue. However, its emission intensity decreased notably by 95% with a fluorescence color change from bright cyan to dark gray by the addition of triethylamine. Copyright © 2013 John Wiley & Sons, Ltd.

Synthesis, Photochromic Properties of a Novel Unsymmetrical Hybrid Diarylethene Material with Benzene Unit

A new unsymmetrical photochromic diarylethene 1o, which is named 1-[2-methyl-5-(4-methoxyphenyl)-3-thienyl]-2-[2-methyl-5-(4-formyphenyl)-3-thienyl] perfluorocyclopentene, was synthesized. Its optical properties, including photochromic reactivity, kinetics and fluorescence properties were investigated in detail. The result indicated that the diarylethene underwent reversible photochromism, changing between colorless and blue in hexane solution and in PMMA, respectively. What is more, the kinetic experiments illustrated that the cyclization/cycloreversion process of this compound was determined to be the zeroth/first reaction. In addition, the results demonstrated that the diarylethene 1o had remarkable fluorescence switching properties.

Near‐Infrared Photochromic Diarylethenes Based on the Changes in the π‐Conjugated System and the Electronic Properties of the Heteroaryl Moieties

AbstractIt is very challenging to construct photochromic materials with absorption and reactivity in the near‐infrared (NIR) spectral region. Herein, four unsymmetrical diarylethene derivatives 1o–4o, which contain both indole and thiophene moieties, have been successfully synthesized, and their photochromic behaviors have been shifted to the NIR region. These newly developed NIR photochromic materials are highly sensitive and responsive to photostimuli both in solution and in poly(methyl methacrylate) films. It has been shown that 1o–4o exhibit remarkable UV/Vis and fluorescence spectral changes, allowing them to behave as reversible optical molecular switches in the NIR region.