Synthesis and photochromic properties of a dithia-dithienylethenophane

The thermally irreversible photochromic compound dithia-dithienylethenophane was synthesized, which is the first example of a dithienylethene bridged with benzene ring and due to the fixation to the photoactive anti-conformation the quantum yield for the photocyclization reaction became higher than that of the corresponding nonbridged type dithienylethene.     

Synthesis and photochromic properties of substituted naphthopyran compounds

A group of 3,3-diaryl-3H-naphtho[2,1-b]pyran compounds with functional substituents at the 5- and 6-positions of the naphthopyran skeleton and the para positions at the 3-aryl moieties were prepared through condensation reactions between 2-naphthol derivatives and 1,1-diarylprop-2-yn-1-ol derivatives. The chemical structures of the compounds were confirmed by NMR and MS. The crystal structure of 3,3-diphenyl-6-morpholino-3H-naphtho[2,1-b]pyran (4b) was determined and the relationship between the pyran substructure and photochromism was discussed. The photochromic properties were studied as well, and decoloration kinetics of colored forms was fitted to the biexponential model. Among these compounds, 4b was considered to be the best one due to the large ΔOD of colored form, which is one of the most important properties used in the photochromic material.     

Synthesis and properties of novel photochromic bisthienylethenes containing imidazole and imidazolium derivatives

A series of bisthienylethenes containing imidazole and imidazolium derivatives have been prepared and the products have been characterized by means of NMR and MS.Their photochromic and fluorescent switch properties have been investigated by UV–vis absorption spectra and fluorescence spectra.The fluorescent emissions of these kinds of photochromic compounds can be simply modulated by varying the imidazole groups,which shows that these compounds may have potential application in the design of fluorescent photochromic materials.     

Synthesis, structure and photochromic properties of a novel 1,6-hexanediamine trimolybdate supramolecular compound

A novel supramolecular compound 1,6-hexanediamine trimolybdate ((C₆H₁₈N₂)[Mo₃O₁₀], denoted as HDAMo) has been synthesized by a hydrothermal method and its structure has been characterized by elemental analyses, Fourier transform infrared (FT-IR) spectra, single-crystal X-ray diffraction (XRD) technique. This single crystal compound consists of protonated 1,6-hexanediamine (HDA) cations and polyoxometalate [Mo₃O₁₀]²⁻ anions. Its crystal structure belongs to monoclinic system (space group P2₁/n) with a=7.7508(14), b=11.467(2), c=16.167(3) Å, β=92.689(3)°, V=1435.3(5) Å³, Z=4 and D_calc=2.619 g cm⁻³. The final statistics based on F² are GOF=0.980, R₁=0.0261 and wR₂=0.0506 for I>2σ(I). XRD analysis revealed that in the crystal structure of HDAMo, novel infinite [Mo₃O₁₀]²⁻ chains parallel to a axis are made up of distorted MoO₆ octahedra connected by corners and edges. The protonated HDA cations occupy channels formed by [Mo₃O₁₀]²⁻ chains and exhibit strong hydrogen bond interactions to terminal and bridging oxo groups of the chains. The [Mo₃O₁₀]²⁻ chains linked through protonated HAD cations formed a one-dimensional network. The HDAMo compound shows novel photochromic properties, i.e., its color changes from white to reddish brown gradually under UV irradiation. XRD, FT-IR, ESR spectra and XPS are used to investigate the photochromic behavior of the compound.     

Synthesis of photochromic diarylethene polymers for a write-by-light/erase-by-heat recording system

A functionalized styrene monomer (1a) having a photochromic diarylethene chromophore with functional properties of photocoloration, photostability of the colored state, and thermal erasion by heating was synthesized, and the polymer and copolymers of 1a were prepared by radical polymerization and copolymerization. Their polymers exhibited excellent photocoloration and rapid thermal bleaching above 150 °C in solution and in the solid state as well as the performance of the monomeric diarylethene chromophore. In addition, the colored state has a high photostability under visible room light. The diarylethene homopolymer had a glass transition temperature (T_g) as high as polystyrene. The copolymer of 1a with N-1-adamantylmaleimide exhibited extremely high T_g above 200 °C with keeping the photofunctional performance. Such photochromic polymer and copolymers with high T_g can be potentially applied to rewritable display materials and image recordings by a write-by-light/erase-by-heat system.     

Synthesis and properties of 1,3,3-trimethylspiro[indoline-2,3′-naphtho[2,1-b][1,4]oxazin]-6′-amine, a novel, red colouring photochromic spirooxazine

The synthesis and photochromic properties of 1,3,3-trimethylspiro[indoline-2,3′-naphtho[2,1-b][1,4]oxazin]-6′-amine, a novel red-colouring photochromic spirooxazine and derivatives is reported. The synthesis proceeds via an unusual one-pot transamination, oxime formation, N-O bond cleavage, spirooxazine formation process.     

Synthesis and photoreaction mechanism of a novel bifunctional photochromic compound

New functionalized spiroxazine containing azo group has been prepared and its photochromic mechanism has been investigated by laser induced time-resolved techniques.     

Synthesis and characterisation of photochromic dithienylcyclopentene liquid crystal with thermal irreversibility

A series of photochromic liquid crystal dithienylcyclopentene derivatives were synthesised from the initial material 2-chloro-5-methylthiophene. They were characterised by ¹H NMR, high resolution mass spectrometer, differential scanning calorimetry (DSC) and polarised optical microscopy (POM) with a hot stage. All of them exhibited excellent photochemically reversible isomerisation between the open-ring form and the closed-ring form in both organic solvents and LC media, resulting in the colour change between colourless and purple under different light irradiations. The typical textures from POM showed that their isomers both had nematic phase and smectic phase with different colours. These compounds with bent shape were more sensitive to light than those of diarylethenes reported.     

Structure and solid-state photochromic properties of two new compounds with pyrazolone-ring

Two new organic photochromic compounds based on pyrazolone were synthesized and further characterized by elemental analysis, MS, IR spectra, and ¹H NMR spectra. The photochromic properties and photochemical kinetics of them have been studied by UV absorption spectra under irradiation of 365 nm light. The photochromism of pyrazolone derivatives in the solid state has been so far explained only in terms of the light-induced change of absorption and their crystal structures, which is caused by the shift of the tautomeric equilibrium between the enol and keto forms. In this work, their IR spectra have been measured before and after irradiation. Based on the IR spectra and crystal structure analysis, a reasonable mechanism was proposed, the photochromic phenomenon may be due to the photoisomerization from enol-form to keto-form through proton transfer.     

Synthesis and photochromic properties of polymers containing spirooxazine groups

Two spirooxazine (SO) compounds containing bromobutyl substituents on 1-position (SO1) and 9′- position (SO2) have been synthesized and characterized by 1H-NMR, IR and ESI-MS in this paper. SO1-g-PMMA and SO2-g-PMMA polymer were prepared by grafting SO1 and SO2 onto PMMA through C-Br bonding sites. Also, SOs were doped into PMMA matrix to afford SO1-d-PMMA and SO2-d-PMMA. Photochromic behaviors of these compounds have been studied. Compared with SO1, SO2 exhibited better photoresponse and slower bleaching in dichloromethane solution. Inserted into polymer films, the decoloration process of SOs were significantly retarded and it was found that the fading curves fitted a first-order equation; As regard to four polymers, 1-position grafting (SO2-g-PMMA) can cause a higher reduction degree on the thermal fading rate.     

A novel strategy for developing yellow diarylethenes based on acid stimulus

A novel strategy for the preparation of yellow diarylethenes was established based on the acidichromism of two new diarylethenes with a bromopyridine moiety. The bromopyridine was connected directly to the central perfluorocyclopentene ring to participate in photoisomerization reaction. The two diarylethenes exhibited favorable photochromism and function as notable fluorescence switches in solution. The absorption maxima of their closed-ring isomers shifted dramatically to shorter wavelengths with notable color change from red to yellow upon the stimulation of trifluoroacetic acid.     

Synthesis and photochromic properties of quinoxalino[e]-annelated dimethyldihydropyrene with planar chirality

9,10-Diacetyl-2,7-di-tert-butyl-trans-10b,10c-dimethyl-10b,10c-dihydropyrene annelated with a quinoxaline unit (q-DM-DHP, 3) was prepared from 5,13-di-tert-butyl-8,16-dimethyl[2.2]metacyclophane-1,2,9,10-tetraoxide (2) and o-phenylenediamine in two steps. The photochromic isomers of q-DM-DHP 3, closed form 3a and open form 3b, were separated by reverse-phase HPLC, and their isolated UV–visible spectra were estimated. The chiral HPLC analyses of q-DM-DHP 3 indicated their planar chirality, and their CD spectra were measured. The photochromic properties and thermodynamic properties of 3 were also discussed based on their UV–visible, ¹H NMR, CD, and fluorescence spectra.     

Photoswitching of an alcohol-sensitive photochromic diarylethene

The closed-ring isomer of diarylethene 1a, 1-(2-methyl-5-(4-N,N-diethylaminophenyl)thien-3-yl)-2-(2-methyl-5-phenylthien-3-yl)perfluorocyclopentene was found to cause the substitution reaction with primary alcohols at room temperature. The open-ring isomer 1a was stable in the alcohols. The product obtained in methanol was isolated by HPLC, and the structure was identified by ¹H NMR, mass spectrometry, and X-ray crystallographic analysis. It was revealed that two fluorine atoms were replaced with methoxy groups. The substitution reaction was also caused with ethylene glycol to form the five-membered ring. Both the products also showed photochromism, and had absorption maxima and photocycloreversion quantum yields different from those of 1a.     

Synthesis, crystal structure and optoelectronic properties of a new unsymmetrical photochromic diarylethene

A new unsymmetrical photochromic diarylethene, 1-(2-methyl-5-phenyl-3-thienyl)-2-[2-methyl-5-(3-trifluoromethylphenyl)-3-thienyl]perfluorocyclopentene (1a), was synthesized and its structure was determined by single-crystal X-ray diffraction analysis. Its optical and electrochemical properties, including photochromic reactivity both in solution and in the solid state (PMMA film and the single-crystalline phase), fluorescence and electrochemical properties were investigated in detail. The compound showed excellent photochromism even in the single-crystalline phase by photo-irradiation. In acetonitrile, the open-ring isomer of diarylethene 1 exhibited relatively strong fluorescence at 470nm when excited at 300nm, and its emission intensity decreased along with the photochromism upon irradiation with 313nm light. Its closed-ring isomer showed almost no fluorescence. The electrochemical properties of diarylethene were investigated by performing cyclic voltammetry experiment and its HOMO and LUMO energy level were calculated.     

Syntheses and optoelectronic properties of four photochromic dithienylethenes

Four photochromic dithienylethene compounds, 1,2-bis(2-methyl-5-naphthalene-3-thienyl)perfluorocyclopentene 1a, 1,2-bis[2-methyl-5(p-fluorophenyl)-3-thienyl]perfluorocyclopentene 2a, 1,2-bis[2-methyl-5(p-ethoxyphenyl)-3-thienyl]perfluorocyclopentene 3a, and 1,2-bis[2-methyl-5(p-N,N-dimethylaminophenyl)-3-thienyl]perfluorocyclopentene 4a were synthesized, and their optoelectronic properties, such as photochromism in solution as well as in poly-methylmethacrylate (PMMA) amorphous films, fluorescences and electrochemical properties were investigated in detail. These dithienylethenes have shown good photochromic behavior both in solution and in PMMA amorphous film. All of them exhibited relatively strong fluorescence and gave a bathochromic shift upon increasing concentration in THF. The irreversible anodic oxidation of 1a, 2a and 4a was observed by performing cyclic voltammetry experiments.     

Synthesis, characterization and photochromic studies of three novel calix[4]arene-Schiff bases

Synthesis and characterization of three novel Schiff bases based on calix[4]arene are described. The synthesis of these compounds had been achieved by the condensation of salicylaldehyde derivatives with the amine group of upper rim of de-butylcalix[4]arene in ethanol. The structures of new compounds were confirmed on the basis of IR, (1)H NMR, (13)C NMR, MS and elementary analysis. Photochromic properties of compounds were studied in CH(3)CN by UV/vis and fluorescence spectra. These Schiff base-calix[4]arene can be used in certain 'supermolecular electronic devices' through combining the photochromic behaviors with others such as non-linear optical or charge transfer properties.     

One-step synthesis and photochromic properties of a stable triangle terthiophene

A new photochromic compound based on the hexatriene backbone was prepared by one-step coupling. The photochromic backbone, composed of three thiophene ring, undergoes reversible ring-opening and ring-closing photoisomerization reactions when irradiated with ultraviolet and visible light, respectively. It exhibited fatigue resistance and thermally irreversible photochromic properties. The ring-open form exhibits appreciable fluorescence, while quenched by the ring-closed form.     

Synthesis and the effect of alkyl chain length on photochromic properties of diarylethene derivatives

A new class of photochromic diarylethenes bearing pyrrole and thiophene units with different length of alkyl chains at 2-position of thiophene rings have been synthesized. Their characteristics, including photochromism and fatigue resistance were investigated systematically, and each diarylethene derivative showed good photochromic properties whether in solution or in PMMA films. The alkyl group moiety was connected directly to the central cyclopentene ring as a heteroaryl unit and availably participated in photoisomerization reaction. And some properties, for example, the conversion ratio in the photostationary state(PSS) and the absorption coefficient of the ring-closed isomers in acetonitrile were significantly affected by the alkyl chain length. The results revealed that substituents of alkyl chain played an important role in the photoisomerization process of diarylethenes.     

Synthesis and properties of a novel photochromic luminophore

A photochemically bifunctional compound was obtained. Its molecule includes the spironaphthoxazine and dansylamino fragments. This compound exhibits both photochromic and luminescent properties. Its spectroscopic characteristics were studied in different solvents. The electronic systems of two constituent fragments do not interact with each other. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2802–2805, December, 2005.     

Synthesis and characterisation of polymerisable photochromic spiropyrans: towards photomechanical biomaterials

A methodology for the synthesis of novel polymerisable spiropyrans with photomechanical properties suitable for subsequent copolymerisation with either vinyl or acrylate-based biomaterials is described. UV-vis spectroscopic characterisation of photoisomerism shows that photochromic behaviour with respect to related non-polymerisable compounds is retained and is solvent dependent. In acetone, conventional spiropyran-merocyanine photochromism is observed for nitro-spiropyran derivatives, whereas in dichloromethane both nitro-spiropyrans and spiropyrans isomerise to merocyanines which rapidly form H-aggregates. The monomers were designed such that an alkyl spacer of variable length, both electronically and sterically, separates the polymerisable moiety from the photochromic core and allows steric aspects of the resulting photomechanical behaviour to be explored.