Photoresponsive Compound Research Articles

Photo-switching compound that controls ATPase and motor activities of mitotic kinesin Eg5.

Kinesins are motor proteins that convert the chemical energy of ATP into mechanical energy and move along microtubules and play various physiological roles. Eg5 is a homotetrameric protein that belongs to the kinesin-5 family. It plays an important role in separating and the formation of bipolar spindles during mitosis cell division. Eg5 is overexpressed in proliferative tissues, and specific inhibition of Eg5 has been shown to induce apoptosis in cancer cells, making it an attractive target part for cancer therapy. Eg5 has specific inhibitors such as Monastrol and STLC, and these are attracting attention as anticancer agents. In our laboratory, previously we synthesized a photochromic Eg5 inhibitor with a photoswitch mechanism by introducing a photoresponsive compound such as azobenzene into a specific Eg5 inhibitor. In this study so far, by coupling of azobenzene and spiropyran, we synthesized an Eg5 inhibitor that introduced a novel photochromic compound that transitions into three different states by light, and photoreversibly controlled the function of Eg5 in three states. In this study, we conducted in vivo experiments to stepwise and appropriately regulated the physiological functions of Eg5. We have attempted to develop new inhibitors that exhibit multi-stage inhibitory activity. Finally, we clarified which steps of the Eg5-ATPase cycle are inhibited by azobenzene and spiropyran derivatives by the mixed motor assays and analyzed the kinetic inhibition mechanisms of Eg5 inhibitors by azobenzene-spiropyran derivatives.

Photo-induced change in alignment of mesogens using reduction of viologens as a trigger

Liquid crystals (LCs), whose refractive index can be changed by light irradiation, can be used as photoresponsive optical materials. In this study, an LC viologen was proposed as a novel photoresponsive compound that induced a change in the alignment of LC molecules (mesogens). An extended viologen with an asymmetric core, that exhibits a low-order LC phase at room temperature, was mixed with the well-known nematic LC compound (5CB) to prepare homogeneously aligned films. The change in the alignment of the mesogens was successfully induced by triggering a one-electron reduction reaction of the viologen moieties by light irradiation.

Synthesis of photoswitchable submicroparticles and their evaluation as ion-imprinted polymers for Pd(II) uptake

The idea of developing a system that enables modulation of the amount of Pd(II) ions bonded to a substrate upon exposure to external stimuli could open interesting prospects for application in various research fields such as sensors, catalysis, gas storage, and separation. In this context, in the present work, a photoresponsive compound was used as a functional monomer in the preparation, for the first time, of a photoresponsive ion-imprinted polymer (PIIP) for metal ion uptake. The Pd(II) template was used as a metal ion model, and the binding behavior of PIIP was evaluated under different experimental conditions. The adopted precipitation polymerization technique allowed us to obtain dispersed submicroparticles, as confirmed by the dynamic light scattering and Langmuir isotherm results. The photoisomerization capability of PIIP, with conformational changes of the polymer, was demonstrated, and an improved binding capacity for Pd(II) was observed after UV exposure of the polymer, with a maximum binding capacity approaching 22 mg g−1. Moreover, from the kinetic studies, the equilibrium binding capacity was reached within almost 3 h either in the dark or under UV irradiation. Finally, the reusability of the polymer over three cycles was demonstrated, and the ion selectivity of Pd(II)-PIIP was confirmed when other metal ions such as Ni(II) and Pb(II) were tested. The present work focuses on the development of a system enable to modulate, upon an external stimuli, the amount of metal ions uptake. A photoresponsive compound was used as a functional monomer for the preparation, for the first time, of a photoresponsive ion-imprinted polymer (PIIP) for Pd(II) uptake. The photoisomerization capability of the submicroparticles of PIIP, with conformational changes of the polymer, was demonstrated and an improved binding capacity versus Pd(II) was observed after UV exposure of the polymer with maximum binding capacity near to 22 mg g−1.

Sunlight and UV driven synthesis of Ag nanoparticles for fluorometric and colorimetric dual-mode sensing of ClO.

A photo-responsive compound BINOL-LA (1) having a rigid backbone ending up with two 5-membered cyclic disulfide moieties was designed. BINOL-LA capped Ag nanoparticles (1@Ag NPs) with a network structure were synthesized in a green way by sunlight or UV lamp irradiation. 1@Ag NPs exhibit a selective recognition towards ClO- in aqueous solution with a switch-on fluorescence response and a visual color change, with detection limits of 0.17μM and 1.54μM, respectively. The sensing mechanism is based on the ClO--mediated oxidation of AgS bond, resulting in a disaggregation of 1@Ag NPs assembly. With the strategy demonstrated here, ClO- in tap water and lake water can be detected quantitatively in 5s.

Nanosegregated Chiral Materials with Self-Assembled Hierarchical Mesophases: Effect of Thermotropic and Photoinduced Polymorphism in Rodlike Molecules.

Supramolecular chirality in a binary mixture of achiral bent-core (BC) and achiral rodlike mesogens was observed. Three different nanosegregated mesophases were determined in the binary system, and meaningful changes in circular dichroism (CD) were detected near the phase-transition temperatures of the rodlike mesogens. The highest CD intensity in the binary system was noted in the nanosegregated mesophase, in which the BC mesogens were in the helical nanofilament (HNF) phase and the rodlike mesogens were in the smectic A phase. The supramolecular chirality in the binary mixture was attributed to the self-assembled hierarchical chiral superstructures. Based on the experimental results, plausible scenarios for the chiral superstructures of the rodlike molecules embedded in the HNF networks are suggested. In addition, a system comprising BC and rodlike molecules doped with a photoresponsive compound exhibited remarkable photoswitching of CD intensity. According to the isothermal photoinduced phase transition of the embedded molecules in BC molecular HNFs, the observed CD intensities can be dynamically and reversibly modulated. Such a material with easily controllable functionality is of considerable interest in the field of materials science.

Development of a Photoresponsive Organic–Inorganic Hybrid Magnet: Layered Cobalt Hydroxides Intercalated with Spiropyran Anions

Abstract To develop an organic–inorganic hybrid photomagnet, we performed the intercalation of sulfonate-substituted spiropyran anions into layered cobalt hydroxides, obtaining the photoresponsive compound, Co(OH)1.84(nSPSO3)0.16·0.8H2O (CoLHSP; nSPSO3: 1′,3′,3′-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-indoline]-5′-sulfonate). After UV irradiation (313 nm), the optical and magnetic properties of CoLHSP clearly changed. A new band emerged in the absorption spectrum at 564 nm, corresponding to the π–π* transition in the open form of nSPSO3. Moreover, the photoisomerization of nSPSO3 induced a new ferrimagnetic phase transition at 10 K in the temperature dependence of DC and AC magnetic susceptibilities in addition to the ferrimagnetic phase transition at 15 K for the unirradiated sample. Analyzing the magnetic measurements before and after UV irradiation, we estimated the phototransformation ratio of the magnetic phase in CoLHSP at approximately 40%.

A neutral Fe(iii) compound exhibiting a two-step spin transition and dielectric anomalies

The mononuclear ferric compound Fe(H-5-Cl-thsa-Me)(5-Cl-thsa-Me)·H2O () was synthesized and characterized using powder/single-crystal X-ray diffraction, Mössbauer spectroscopy, differential scanning calorimetry (DSC), and magnetic susceptibility measurements. This photo-responsive compound shows reversible, two-step spin-crossover behaviour. Moreover, dielectric anomalies were observed during the spin transitions, demonstrating the multifunctional properties of compound .

A ‘chemically-gated’ photoresponsive compound as a visible detector for organophosphorus nerve agents

We describe a versatile and convenient visible detection method for organophosphorus compounds based on a colorless 'pro-photoresponsive' organic molecule that undergoes photochemical ring-closing to produce a colored isomer only after it reacts with vapors of the phosphorylating agent.

Photoresponsive Pseudopolyrotaxane Hydrogels Based on Competition of Host–Guest Interactions

Reversibility is a basic and crucial feature of supramolecular systems. In designing and fabricating new supramolecular materials, the realization of reversibility is particularly important as it could enable these substances to be superior to conventional materials. An excellent example is an elastomer reported recently, made of small functional molecules which form both long chains and cross-linkers through intermolecular multiple hydrogen bonding. When broken or cut, the elastomer can be simply repaired by just bringing together the fractured surfaces and allowing the recovery of the hydrogen bonding. There are plenty of reports on supramolecular assemblies of polymers showing reversible responses to environmental changes; however, these are mostly based on the inherent stimuli-sensitive properties of the building blocks, such as the temperature-induced coil–globule transition of poly(N-isopropyl acrylamide) (PNIPAM) and pH-induced protonation of poly(vinyl pyridine), rather than the reversibility of the supramolecular interactions. Therefore, taking full advantage of the reversibility of the noncovalent interactions to construct supramolecular materials is still a big challenge. This has drawn increasing interest in recent years, and has led to a series of promising results. For example, some hydrophobically modified water-soluble polymers realized sol–gel transition as a result of the reversible interactions of cyclodextrin and alkyl chains. The assembly and disassembly of polymeric vesicles can be controlled by photosensitive interactions between cyclodextrin and azobenzene compounds. The self-assembly of polyethylene glycol (PEG) and a-cyclodextrins (a-CDs) to form linear pseudopolyrotaxane (PPR), with PEG as the axis and a-CDs as threaded rings, was reported by Harada et al. Since the ability of PPR to form physical hydrogels was first reported in 1994, the system has been extensively studied as the hydrogels show very promising uses as biomedicine materials. There is now good understanding of the formation mechanisms and structures of such PPR hydrogels, but little has been explored concerning their dissociation and reassembly, though increasing temperature and shearing could make the hydrogel turn to a sol. Herein, we demonstrate a facile photocontrollable supramolecular route to realize the disassembly and reassembly of the PPR hydrogels. The addition of a photoresponsive compound containing an azobenzene moiety to the PPR hydrogel was found to be effective in converting the hydrogels to transparent solutions. By subsequent alternation of UVand visible irradiation, reversible sol-to-gel and gel-to-sol transitions were observed. Thus, the widely investigated PEG/aCD PPR hydrogel is proved to be “active” in supramolecular chemistry, and the reversible nature of supramolecular materials is fully realized. In our study, the PPR hydrogel (Figure 1a) was prepared by using PEG10K (molecular weight 10000) and a-CD in water as described in reference [7c]. The concentrations of

Morphological Changes in Vesicles and Release of an Encapsulated Compound Triggered by a Photoresponsive Malachite Green Leuconitrile Derivative

Photoinduced morphological changes in phosphatidylcholine vesicles are triggered by a Malachite Green leuconitrile derivative dissolved in the lipidic membrane, and are observed at Malachite Green derivative/lipid ratios <5 mol %. This Malachite Green derivative is a photoresponsive compound that undergoes ionization to afford a positive charge on the molecule by UV irradiation. The Malachite Green derivative exhibits amphiphilicity when ionized photochemically, whereas it behaves as a lipophilic compound under dark conditions. Cryo-transmission electron microscopy was used to determine vesicle morphology. The effects of the Malachite Green derivative on vesicles were studied by dynamic light scattering and fluorescence resonance energy transfer. Irradiation of vesicles containing the Malachite Green derivative induces nonspherical vesicle morphology, fusion of vesicles, and membrane solubilization, depending on conditions. Furthermore, irradiation of the Malachite Green derivative induces the release of a vesicle-encapsulated compound.

Fabrication and optical properties of photochromic compound/clay hybrid films

A cationic spiropyran iodide derivative (SPI) was synthesized as a photoresponsive compound, and SPI/montmorillonite clay hybrid films were prepared using ion- and guest-exchange intercalation methods. When the ion-exchange method was applied to clay with a low cation-exchange capacity (CEC), intercalation of SPI into clay interlayers did not occur. Using the clay with a high CEC, SPI was intercalated into clay interlayer and the interlayer distances were elongated. Upon UV and visible light irradiation, SPI in hybrid film photoisomerized reversibly and the interlayer distance also changed reversibly. On the other hand, intercalation by the guest-exchange method using cethyltrimethylammoniumbromide (CTAB) as a pre-exchanging reagent was independent on the CEC. After the addition of SPI, the CTAB in the clay interlayers was exchanged for SPI, but a partial CTAB remained in the interlayer. SPI in the hybrid films prepared by the guest-exchange method photoisomerized reversibly without any change in interplanar distance due to the coexisted CTAB.

Planar Chiral Azobenzenophanes as Chiroptic Switches for Photon Mode Reversible Reflection Color Control in Induced Chiral Nematic Liquid Crystals

In this report, for the first time, a planar chiral photoresponsive compound has been employed in commercially available nematic liquid crystals to achieve phototunable reflection colors. We designed an azobenzenophane compound having conformational restriction on the free rotation of naphthalene moiety to impose an element of planar chirality and the corresponding enantiomers were resolved by HPLC on chiral column. We have determined the absolute configuration by comparison of density functional theory (DFT) calculations of its electronic circular dichroism (ECD) spectrum and specific rotation [alpha] D to experimental ECD and [alpha] D data. Enantiomers exhibit photochemically reversible isomerization in solution without undergoing thermal or photoinduced racemization. As chiroptic switches in different host nematic liquid crystals, they exhibit good solubility, moderately high helical twisting power, as well as a large change in helical twisting power due to photoisomerization. A unique feature of these chiral photochromic compounds is that no other auxiliary chiral agents is required to achieve a fast photon mode reversible full-range color control in induced cholesterics, that is, both the hypsochromic and bathochromic shift can be obtained from a single LC formulation by reversible photoisomerization of the single chiral compound.

Effective Photocontrol of Micelle Formation by Malachite Green Derivative Carrying a Long Alkyl Chain

Abstract We designed Malachite Green leuconitrile carrying a long alkyl chain that is intended for a photoresponsive surfactant. The critical micelle concentration of cetyltrimethylammoium chloride solution containing the photoresponsive compound was decreased significantly by UV irradiation. The lipophilic photochromic compound realizes photochemical control of micelle formation.