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.     

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 photochromic properties of novel yellow developing photochromic compounds

Two 1-thiazolyl-2-thienylcyclopentene derivatives, 1a and 2a, and a 1-thiazolyl-2-vinylcyclopentene derivative 3a have been synthesized in an attempt to obtain photochromic compounds which change the color from colorless to yellow, and have low photocycloreversion quantum yields and high absorption coefficients of the colored isomers. All of these compounds underwent reversible photochromic reactions. Compounds 1a and 2a in toluene solutions changed the color upon 313 nm light irradiation from colorless to orange and pink, in which absorption maxima were observed at 494 nm (ε=10,000 M⁻¹ cm⁻¹) and 525 nm (ε=8500 M⁻¹ cm⁻¹), respectively. On the other hand, the colorless toluene solution of 3a turned yellow upon irradiation with 313 nm light, in which the absorption maximum was observed at 416 nm (ε=17,100 M⁻¹ cm⁻¹). The photocyclization/cycloreversion quantum yields of 3 were 0.19 and 0.0014, respectively. The conversion from the open- to the closed-ring isomer of 3 in the photostationary state under irradiation with 313 nm light was close to 100%.     

Photostability of a photochromic naphthopyran dye in different sol-gel prepared ormosil coatings

A photochromic naphthopyran derivative was embedded in sol-gel prepared thin ormosil films. The resulting samples show high transparency and exhibit a strong red colouration upon irradiation with UV light. The photostability of the photochromic molecules is strongly related to the nature of the embedding ormosil matrix. The introduction of organic functional groups into the inner pore surface of the matrix allows tailoring the chemical environment where the dye molecules will be allocated, in terms of the effectiveness of the interaction between the photochromic molecules and the Si-OH groups on the surface of the pores, affecting the stability of the molecules upon prolonged exposition to UV light. The photostability of the molecules was increased in matrices functionalized with larger organic groups, or with larger amount of modifying groups. In this way the photodegradation of the photochromic molecules could be reduced by a factor of 5, as compared with the photodegradation of the molecules in unfunctionalized silica matrix.     

Design,synthesis, photochromism and electrochemistry of a novel material with pendant photochromic units

In the present work, the synthesis, photochromism and electrochemistry of a novel material 1, 1-(4-[3,4-bis(2,5-dimethyl-3-thienyl)cyclopent-3-en-1-yl]phenyl)-2,5-di-2-thienyl-1H-pyrrole, with pendant dithienylethene (DTE) photochromic units are described. It should be noted that the system 1 can be reversibly and efficiently switched between open (1o) and closed (1c) states by light in both solution and in the solid poly(methyl methacrylate) matrix. It is also noteworthy that the two isomers (1o and 1c) of this novel system 1 can be smoothly polymerized on ITO by electrochemical means. Surprisingly, the DTE unit in 1 does not retain its photochemical switching properties after immobilization onto ITO. The morphology of the polymer film was investigated by AFM analysis. Furthermore, it was found that the polymer exhibited remarkable electrochromic features that can be switched from green in the neutral state to violet state under applied external potentials without disturbing the photochromic units.     

Preparation and Properties of Electrospun Sheath-core Modified-PMMA Nanofibers with Photoluminescence and Photochromic Functions

Multi-functional nanofibers are playing an important role in the optical field, and are widely used in fluorescence indication, product anti-counterfeit identification and smart clothing. Nanofibers with photoluminescence and photochromic functions are already attracting more interest from researchers. In this work, based on electrospun technology, the modified-PMMA nanofibers[PMMA=poly(methyl methacrylate)] with photoluminescence and photochromic functions were prepared through the design of the sheath-core structure(SCNFs 1-4). Compared with other samples, SCNF-4 shows outstanding photoluminescence and photochromic functions. SCNF-4 can produce green light and its fluorescence intensity and fluorescence lifetime can reach 7144 a.u. and 1031.32 μs, respectively. In photochromic functions, SCNF-4 can show purple in 1 min under the 365 nm ultraviolet light, and the color can be preserved for more than 4 h under the sunlight. When SCNF-4 is irradiated by far infrared light, the color of the samples can fade quickly in 40 s. Under the irradiation of ultraviolet light of different wavelengths, SCNF-4 can display multi-color fluorescence and achieve a reversible transition between white and purple. The design of the sheath-core structure realizes the complementarity of photoluminescence and photochromic functions of the electrospun modified-PMMA nanofibers, which is important to promote the wide application of multi-functional nanofibers in the optical field.     

Electrical switching effect in a photochromic molecule between two graphene electrodes

We propose a single-molecule electrical switches consisting of a photochromic dimethyldihydropyrene/cyclophanediene molecule sandwiched between two graphene electrodes and investigate the electronic transport by using density-functional theory and nonequilibrium Green's function methods. The “open” and “closed” isomers of the photochromic molecule are shown to have electrical switching behavior and negative differential resistance effect. Moreover, it is also found that the switching ratio between two different conductive states depends on the ambient temperature, and the device behaves as a stable electrical switch around room temperature, which is in agreement with a recent experimental study of another photochromic molecule diarylethene reported by Jia et al. (2016) [17].     

偶氮型光致变色液晶树状大分子的量子产率、异构转化率和活化能研究

研究了化合物端基含36个己氧基偶氮苯介晶基元的二代(G2)光致变色液晶树状大分子在氯仿及四氢呋喃溶液中的量子产率、吸收光强Ia、活化能E、异构转化率A/A0、热回复异构化速率常数kH及其反/顺异构体组分比A′/A′0,并与一代光致变色液晶碳硅烷树状大分子(G1)及介晶基元化合物(M3)的光化学行为进行了比较.在氯仿及四氢呋喃溶液中的量子产率的顺序均为M3>G1>G2,吸收光强Ia在氯仿及四氢呋喃溶液中的顺序分别为G2>G1>M3(氯仿)和M3>G1>G2(四氢呋喃),在氯仿及四氢呋喃溶液中活化能的顺序均为M3>G2>G1,在氯仿及四氢呋喃溶液中热回复异构化速率常数kH的顺序均为G1>G2>M3,在热回复异构化反应中的反/顺异构体组分比A′/A0′在氯仿及四氢呋喃溶液中的顺序均为G2>G1>M3.     

Synthesis and spectroscopic characterization of red-shifted spironaphthoxazine based optical switch probes

Spironaphthoxazine (NISO) is an efficient optical switch probe that has applications in high contrast detection of Förster resonance energy transfer (FRET) using optical lock-in detection (OLID). NISO exists in two distinct states, spiro (SP) and merocyanine (MC), that can be independently controlled by using alternate irradiation with near ultraviolet and visible light. Unfortunately, the SP-state of NISO has an absorption centered at 350 nm, which may lead to phototoxic effects when manipulating the probe within a living cell. To overcome this problem we introduce new, red-shifted amino-substituted NISO probes compared to NISO that undergo an efficient SP to MC transition in response to irradiation by using 405-nm light, which is less damaging to living cells. This study details the synthesis of amino-substituted NISO and their N-hydroxysuccinimide ester and maleimide derivatives and their use in generating covalent attached protein conjugates. This study also presents a characterization of the spectroscopic and optical switching properties of these red-shifted NISO probe in solution.     

Novel photochromic macrocycles composed of thiophene and ethylene building blocks: synthesis, structure, and photochromic property

Two novel photochromic macrocycles composed of thiophene and ethylene building blocks have been synthesized, and their crystal structure and photochromic properties are described. Macrocycle 2 shows good photochromic properties.