Patterned colloid assembly by grafted photochromic polymer layers

Quartz surfaces and colloidal silica particles were derivatized with a poly(methyl methacrylate) copolymer containing spirobenzopyran (SP) photochromic molecules in the pendant groups at a concentration of 20 mol %. Two-photon near-IR excitation (approximately 780 nm) was then used to create chemically distinct patterns on the modified surfaces through a photochromic process of SP transformation to the zwitterionic merocyanine (MC) isomer. The derivatized colloids were approximately 10 times more likely to adsorb onto the photoswitched, MC regions. Surface coverage and adsorption kinetics have been compared to the mean-field model of irreversible monolayer adsorption.     

Bistable photoswitching in poly(N-isopropylacrylamide) with spironaphthoxazine hydrogel for optical data storage

A bistable switching photochromic poly(N-isopropylacrylamide) with spironaphthoxazine hydrogel copolymer (PNIPA-SPO-BIS) has been designed and synthesized by radical polymerization. The PNIPA-SPO-BIS copolymer is identified by ¹H NMR spectroscopy, FIT-IR spectroscopy and gel permeation chromatography (GPC). The morphology of the internal microstructures of the PNIPA-SPO-BIS hydrogels was observed by scanning electron microscopy (SEM). The PNIPA-SPO-BIS copolymer showed excellent photochromic behavior in water solution and in gel state. In addition, erasable and rewritable (EARW) photoimaging on the PNIPA-SPO-BIS hydrogel was successfully demonstrated. A novel optical data storage materials based on photochromic hydrogel was developed. These developments are crucial for fundamental studies and eventual technical application for all-photo mode high-density optical data storage.     

Time-resolved fluorescence study on the photomerocyanine form of spiropyran and its derivative with azobenzene

The excited state dynamics of the photomerocyanine (PMC) form originating from spirobenzopyran and the bi-functional photochromic compound spirobenzopyran–azobenzene (SpAz), containing typical photochromic molecules of spirobenzopyran (Sp) and azobenzene (Az), were investigated using picosecond time-resolved fluorescence measurements in solution at 200 and 285 K and in a PMMA polymer film at 298 K. While the fluorescence lifetimes of PMC were about twice as long as those of SpAz under all experimental conditions, both lifetimes showed similar strong dependence on viscosity rather than temperature. These results suggest that non-radiative decay to an intermediate state could be accompanied by a significant conformational change. The effect of the Az moiety in this relaxation process is also discussed. It is unlikely that an energy transfer from the PMC moiety to the Az moiety occurs. It was concluded that the PMC moiety in the bi-functional SpAz is independent from the Az moiety.     

Optically switchable chelates: optical control and sensing of metal ions

This study introduces new concepts in the design, synthesis, and in vitro and in vivo characterization, manipulation, and imaging of organic chelates whose association with metal ions is rapidly and reversibly controlled by using light. Di- and tricarboxylic group bearing photochromes, nitrobenzospiropyran (nitroBIPS), undergo rapid and reversible, optically driven transitions between their spiro (SP) and fluorescent merocyanine (MC) states. The MC state of nitroBIPS-8-DA binds tightly to various metal ions resulting in specific shifts in absorption and fluorescence, and the dissociation constant for its Gadolinium complex in water is measured at approximately 5 microM. The metal-bound MC state is converted to the weaker-binding SP state with use of 543 nm light, while the SP to MC transition is complete with use of 365 or 720 nm (2-photon) light within several microseconds. Fluorescence imaging of the MC state of nitroBIPS-8-TriA was used to quantify the rate and efficiency of optical switching and to provide a real-time readout of the state of the optically switchable chelate within living cells.     

双功能螺吡喃螺噁嗪类光致变色化合物研究进展

光致变色材料在光学镜头、光学信息存储、光分子开关等方面具有广泛的应用.双功能光致变色材料的合成与应用研究越来越受关注.综述了以螺吡喃、螺噁嗪为光致变色基团的双功能光致变色化合体系的研究进展,主要介绍了具有荧光性能、与金属离子络合性能的光致变色体系的研究进展以及应用.     

7-trifluoromethylquinoline-functionalized luminescent photochromic spiropyran with the stable merocyanine species both in solution and in the solid state

A new spiropyran (SP2) with the stable merocyanine form (MC2) both in solution and in the solid state at room temperature was designed and synthesized. The stability of MC2 is believed to be due to the electron-withdrawing effect of both the quinoline and the trifluoromethyl groups. (1)H NMR spectra indicate that the ratio of the open form vs the closed form of SP2 is dependent on the polarity of solvents. Single crystals composed of only the open form (MC2) were successfully obtained. X-ray structural analysis indicates that except trifluoromethyl and two methyl groups MC2 is completely planar with an s-trans,s-cis conformation. It should be noted that this is the first report of the X-ray crystal structure of the pure open form of spiropyran. MC2 can be slowly transformed into SP2 at -30 degrees C or lower temperature, and the process is accelerated by visible light irradiation. This special photochromic behavior can be explained by the calculated thermodynamic data. The spectral properties of SP2/MC2 in the presence of different metal ions are also studied, and the results show the potential application of SP2/MC2 in sensing metal ions.     

A Photoswitchable Solvatochromic Dye for Probing Membrane Ordering by RESOLFT Super-resolution Microscopy**

A switchable solvatochromic fluorescent dyad can be used to map ordering of lipids in vesicle membranes at a resolution better than the diffraction limit. Combining a Nile Red fluorophore with a photochromic spironaphthoxazine quencher allows the fluorescence to be controlled using visible light, via photoswitching and FRET quenching. Synthetic lipid vesicles of varying composition were imaged with an average 2.5-fold resolution enhancement, compared to the confocal images. Ratiometric detection was used to probe the membrane polarity, and domains of different lipid ordering were distinguished within the same membrane.     

Photochromism of side-chain liquid crystal polymers containing spironaphthoxazines

Side-chain liquid crystal polyacrylates and polysiloxanes containing different photochromic spironaphthoxazine side groups were synthesized. Thermodynamic, spectral and kinetic properties of the polymers were investigated. The structure of the mesophase is discussed.     

Visible light responsive spiropyran derivatives based on dynamic coordination bonds

Spiropyrans (SPs) are a well-known class of photochromic compounds and have found widespread application due to their unique properties. However, for many conventional SPs, high energy ultraviolet (UV) light is commonly essential to drive photoisomerization, leading to poor fatigue resistance. Moreover, the practical application of spiropyrans is hindered by their fast fading speed due to the instability of closed forms (SP) or open forms (MC). Herein, we disclose a novel strategy to address these challenges through introducing both electron-donating substituents to stabilize the SP and dynamic coordination bonds to stabilize the MC. The resulting new spiropyrans complexes exhibit negative photochromic properties, with fast visible light response, good stability of both SP and MC, and significantly improved fatigue resistance.     

Photo‐switchable spiropyran immobilized polystyrene beads using catechol chemistry

Catechol and spiropyran functional groups were conjugated to a polymer backbone, allowing immobilization on polystyrene beads (PS beads). The final product was capable of stably reproducing the optical properties of spiropyran. Through the outstanding surface adhesion properties of the catechol functional group, spiropyran was immobilized on PS beads. Switchable photoluminescence in the spiropyran coated PS bead surfaces was observed depending on irradiation with either UV or visible light. The surfaces of the PS beads were morphologically examined by field emission scanning electron microscopy and X‐ray photoelectron spectroscopy was used for characterization of the constituent atoms. Furthermore, UV–Vis and fluorescence spectroscopy were used to confirm conversion between the spiropyran (SP) and merocyanine (MC) forms through UV or visible light irradiation on SP, while fluorescent images for both SP and MC were studied using confocal laser scanning microscopy. The confocal images of the SP‐PS beads system onto MDAMB‐231 cells under UV and visible light indicate the cellular uptake by emerging color within the cytoplasm. Advancing study, the remaining catechol groups can confers adhesive properties, given by contact angle data of various coated surfaces film. These stimuli‐responsive coatings are compatible as drawing switchable photochromic material on versatile substrate shown in confocal images of propylene film. Overall, this great water solubility and biocompatibility PS beads system also showed potential as cell bio‐imaging light stimuli responsive material, and the benefits of this system can also possibly address coat able advanced material for a wide range of surface light sensor applications. Copyright © 2017 John Wiley & Sons, Ltd.     

Synthesis and properties of photochromic liquid-crystalline polyacrylates containing a spirooxazine group

The novel photochromic liquid-crystalline polyacrylates containing a spirooxazine group were synthesized. The photochromic polymer containing (4-penta- methyleneoxy)biphenylene moiety at the 5-position of spironaphthoxazine showed nematic phase from 122.9 to 133.8°C. The photochromic polymer containing undeca- methylene instead of pentamethylene showed smectic phase from 93.1 to 169.7°C. On the other hand, the photochromic polymer containing both undecamethylene as a spacer and spironaphthoxazine-bound biphenylene moiety at 9′-position did not show any liquid crystallinity. All spirooxazine-containing liquid-crystalline polymers showed photochromism in the solid state at room temperature. Because the shape of the absorption spectra of the photochromic quenched liquid-crystalline polymer films was almost the same as those of the photochromic amorphous polymer films, the photochromic properties did not depend on the mesophase in the polymers examined. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3513–3522, 1999     

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.     

Photophysical effects between spirobenzopyran-methyl methacrylate-functionalized colloidal particles

Colloidal particles were derivatized with end-grafted polymethylmethacrylate polymer brushes containing varying concentrations of spirobenzopyran photochromic molecules. The polymers were grown from initiator-functionalized silica particles by an atom-transfer radical polymerization (ATRP). These core-shell colloids formed stable suspensions in toluene with the spirobenzopyran in its closed, nonpolar form. However, UV-induced photoswitching of the photochrome to its open, polar merocyanine isomer caused rapid aggregation. The nature of this colloidal stability transition was examined with respect to the spirobenzopyran content in the polymeric brush and solvent polarity. Turbidimetry, wettability studies, UV-vis spectroscopy, suspension rheology, SEM, and visual inspection were utilized to characterize the system photoswitchability. It was found that the system exhibiting the greatest transition in toluene was the copolymer brush composed of 20% spirobenzopyran and 80% methyl methacrylate.     

Highly stable and fluorescent switching spirooxazines

Two novel photochromic spirooxazines, SO-NA1 and SO-NA2, containing a naphthalimide unit were synthesized. The imide group of naphthalimide unit is incorporated at the naphthoxazine fragment, thus giving strong electron-withdrawing effect favoring the long-lived merocyanine (MC) in the dark giving good colorability in solution. Remarkably, their open merocyanine (MC) forms exhibit significantly long lifetimes, almost three magnitudes longer than that of unsubstituted spironaphthoxazine (1). Moreover, the fluorescence of naphthalimide unit can be switched on and off by photoinduced conversion between the open and closed forms.     

New developments in photochromic polymers

New developments on photochromic polymers have been obtained with systems containing spirobenzopyran derivatives. The importance of the chemical incorporation of the photochrome within the polymer backbone is stressed, and the influence of matrix orientation on the rate of fading is shown. Well known fatigue phenomena are illustrated on the basis of the changes of photostationary optical density on repeating the irradiation–dark recovery cycle. The photomechanical properties and characteristics of rubbery polyethylacrylates crosslinked with the photochrome bismethacrylate are considered in detail. Another principle of photochromism based on photodissociation phenomena is also discussed in the case of the photodissociation and photorecombination of anthracene derivatives and benzacridizinium tosylate, as well as in the case of the photodissociation and thermal recombination of benzpinacol groups incorporated in the polymer main chain. In these experiments in the solid state, it can be shown that the recombination involves always two successive steps: a rapid step corresponding to cage recombination and a second slow step related to diffusion and segment mobility (T_g) of the polymer.     

Photocontrollable cation extraction with crowned oligo(spirobenzopyran)s.

The photoinduced changes of metal-ion extractability of crown ether derivatives bearing three or four spirobenzopyran moieties and their analogues were studied using 1,2-dichloroethane as the organic solvent. Under dark conditions, these compounds extracted Cu2+, Ag+, and Pb2+ with their counteranions from the aqueous phase to the organic phase. The extraction equilibrium constants of the photochromic crown ether derivatives for Cu2+ and Ag+ were determined successfully. Under UV-light irradiation conditions, the extraction of Cu2+ by crowned tris(spirobenzopyran) was enhanced, while that of Ag+ was suppressed. During the competitive metal-ion extraction of crowned oligo(spirobenzopyran)s between Cu2+ and Ag+, the metal-ion selectivity was reversed explicitly by photoirradiation.     

Kinetics of photochemical reactions of a new biphotochromic compound upon photolysis with light of different wavelengths

Using the method of microsecond flash photolysis with UV and visible light, the spectral and kinetic characteristics of intermediate products of photolysis in toluene and methanol solutions of a new biphotochromic compound have been studied, in which two photochromic moieties, spironaphthoxazine and azomethine, are linked to each other in such a way that there is conjugation between π-electronic systems of the moieties in the ground state of the molecule. Two intermediate products have detected, whose relative efficiency of formation substantially depends on the solvent and the wavelength of excitation light.     

Sensitivity and Resolution Development of Spiropyran‐based Molecular Photoswitches

The phenylazo moiety and its donor‐ and acceptor‐substituted derivatives are studied as effective auxochromes to improve their sensitivity and resolution for distinguishing between the spiro (SP; OFF) and mero (ON) forms in molecular photoswitching applications. Thus, 13 azospiropyran derivatives were synthesized and their spectroscopic and photokinetic behaviors were studied. The quality of photochromic reactions of the synthesized photochromic compounds were compared using a dose–response model. Interestingly, by replacing the nitro group in 6‐nitrospiropyran (ε = 0.42 × 10⁴ M^?1 cm^?1) with a simple phenylazo moiety, the SP form is still colorless and the color intensity of the merocyanine (MC) form is improved desirably by extending the conjugation length ( 1a , ε = 1.35 × 10⁴ M^?1 cm^?1). The presence of a hydrophilic OH group or a CH₃ group at the para position of phenylazo moiety revealed more or less the same photochromic properties as 1a . The OCH₃ group substituted at position 6 of the phenylazo moiety at the para position of the azobenzene moiety effectively increased the photochromic properties with the maximum k‐value for SP to MC switching. Meanwhile, Cl, Br, COOH, and NO₂ groups at the para position of the azobenzene moiety revealed the reduction in photochromic properties compared to 1a .     

Dynamics of photoprocesses in novel bifunctional salicylideneiminospironaphthoxazines

The dynamics of photochemical processes in a number of novel photobifunctional compounds, whose molecules combine a photochromic spironaphthoxazine fragment with the salicylideneimine moiety containing different substituents, was studied by the flash photolysis technique. Three products of photolysis of these compounds were detected, and the effects of the substituents and the solvent nature (toluene and methanol) on their spectral and kinetic characteristics and quantum yields were studied.     

Detailed investigation on a negative photochromic spiropyran

The negative photochromic properties of a spiropyran are investigated in various solvents and in solutions of different acidity. The results indicate that the polarity of the solvent has a prominent effect on λ_max of the coloured merocyanine form (MC), whereas its effects on λ_max of the closed form (SP) and on the coloration rates after visible bleaching are very weak. From the effect of acid concentration on the coloration rates the pK_a of the cis intermediate Y in the coloration process is determined to be about 1.1 lower than that of the protonated merocyanine (MCH⁺). The structures and configurations of MC, SP, MCH⁺ and Y are assigned via their ¹H NMR spectra.