- Decoloration rates of a photomerocyanine dye as a visual probe into hydrogen bonding interactions
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We have developed a visual marker for the investigation of hydrogen bonding (HB) effects. The decoloration rate of a photochromic dye that incorporates a latent intra-molecular HB feature can be linked to the HB character of the media. Kinetic and thermodynamic parameters of this simple decoloration approach for HB sensing are investigated both experimentally and by high level theoretical studies. This principle has been applied for the detection of changes in the HB character of stationary and fluidic systems. A major finding is the observation of a shear-related perturbation of the balance between intra- and inter-molecular HB within a dynamic thin film.
- Ciampi, Simone,Eggers, Paul K.,Haworth, Naomi L.,Darwish, Nadim,Wagner, Pawel,Coote, Michelle L.,Wallace, Gordon G.,Raston, Colin L.
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- Spiropyran as a reusable chemosensor for selective colorimetric detection of aromatic thiols
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Design of optical molecular probes for selective detection of aromatic thiols has attracted much attention. Although several types of probes have been proposed, all of them exhibit colorimetric or fluorometric response via irreversible reaction with aromatic thiols and cannot be reused. Here we report that a spiropyran dye is the first example of a reusable chemosensor for aromatic thiols. A colorless spiropyran dye (1) dissolved in aqueous media containing aromatic thiols is selectively isomerized to the colored merocyanine form in the dark. In contrast, visible light irradiation of the merocyanine form promotes successful reversion to the colorless spirocyclic form. Kinetic absorption analysis and ab initio calculations of the transition states revealed that this colorimetric response in the dark is ascribed to the decrease in activation energy for isomerization via the nucleophilic interaction between the aromatic thiol and the olefinic carbon of the dye.
- Shiraishi, Yasuhiro,Yamamoto, Kohei,Sumiya, Shigehiro,Hirai, Takayuki
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- Dicondensed indolinobenzospiropyrans as precursors of thermo- and photochromic spiropyrans. Part II: Assignment of 1H and 13C NMR spectra
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The 1H and 13C NMR spectra of dicondensed indolinobenzospiropyrans as precursors of thermo- and photochromic spiropyrans, DC1-DC5, were completely assigned. Especially, the 1H assignment and coupling characteristics of the diastereotopic protons at the carbon-3 position of the benzopyran rings were achieved by conducting 1H-1H COSY and nOe experiments. The dihedral angles (θ1, θ2 and θ3) calculated from the experimental values of the vicinal coupling constants (3J) of DC5 are in good agreement with the observed values in the solid state. All of the carbons in the DC dye molecules were investigated through a combination of heteronuclear 2D-shift correlation spectroscopy (HETCOR) and DEPT135. Copyright
- Keum, Sam-Rok,Ahn, Su-Mi,Roh, Se-Jung,Park, Su-Jin,Kim, Sung-Hoon,Kon, Kwangnak
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- Light induced tuning of quantum cascade lasers
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A method for tuning the emission of a midinfrared quantum cascade laser using ultraviolet light is presented. The method uses a quantum cascade laser where a photochromic material is deposited as the top waveguide cladding. Changing the state of the cladding causes variations in the absorbance of the cladding. Wavelength dependent changes in the waveguide losses occur, forcing the laser to emit at a wavelength correlated with an absorbance minimum of the cladding. A blueshift by about 6 cm-1 was obtained at room temperature under UV irradiation which was fully reversed by exposure to visible light or room temperature relaxation.
- Basnar,Mujagic,Andrews,Roch,Schrenk,Strasser
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- 1',3',3'-Trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indoline]: Its thermal enantiomerization and the equilibration with its merocyanine
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The enantiomers of the title compound, the important photochromic material (RS)-1b, have been enriched semipreparatively by liquid chromatography. As a consequence, we were able to determine the barrier of the thermal interconversion (R)-1b?(S)-1b via time-dependent polarimetry, amounting to ΔG(≠)=85.9 kJ/mol at 22.0°C in d6-DMSO (Table 2). The thermal equilibration of the corresponding merocyanine 2b was monitored in d6-DMSO by time-dependent 1H NMR, resulting in ΔG1(≠)=102.8 and ΔG2(≠)=92.0 kJ/mol at 22°C (Table 1). This means that, starting from (RS)-1b, the opened isomer 2b is attained by a slow reaction (ΔG1(≠)=102.8 kJ/mol, Fig. 4). Therefore, the merocyanine 2b cannot be identified with the intermediate required for the fast process of C(sp3)-O bond cleavage (ΔG(≠)=85.9 kJ/mol) upon the above enantiomerization of (RS)-1b. Apparently, these two thermal isomerizations (Fig. 4) are independent of each other. The structure of the unknown intermediate of the interconversion (R)- 1b?(S)-1b must therefore differ from the known one of merocyanine 2b. (C) 2000 Elsevier Science Ltd.
- Kiesswetter, Roland,Pustet, Nikola,Brandi, Friedrich,Mannschreck, Albrecht
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- Photochromism of spiropyran in molecular sieve voids: Effects of host-guest interaction on isomer status, switching stability and reversibility
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Spiropyran or its preferred configurational isomers, respectively, are incorporated in faujasite (NaY, HY and DAY) cages by in situ synthesis, and in Si-MCM-41 channels by wetness impregnation. Luminescence spectra of the colored isomers indicate the non-aggregated incorporation of merocyanine forms. High quantum yields for the photochromism ( ~ 75%) demonstrate the ready access of the chromophores for the photons of the laser pulses, used for the photoinduced switching between the different configurational isomers. The strong retardation of the thermal relaxation rate from the photoproduct cis-merocyanine to the thermodynamically preferred trans-merocyanine in the faujasite hosts (HY, DAY) in comparison to spiropyrans in SiO2 or Al2O3 is attributed to an increase of the rotation barriers by the imposed spatial restrictions. Among the different faujasites the dealuminated Y-zeolite (DAY) exhibits the lowest relaxation rates of the photoproduct and the highest switching reversibilities between the trans- and the cis-merocyanine.
- Schomburg,Wark,Rohlfing,Schulz-Ekloff,Woehrle
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- Effects of metal ion complexation on the spiropyran-merocyanine interconversion: Development of a thermally stable photo-switch
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Spectrophotometric absorption and fluorescence measurements of spiropyrans 2 and 3 modified with chelating functionalities, in the presence of Ca2+ and Zn2+, provide evidence of a thermally stable spiropyran-merocyanine photoswitch that is modulated by the metal cations.
- Wojtyk, James T.C.,Kazmaier, Peter M.,Buncel, Erwin
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- Photochromism of a spiropyran and a diarylethene in bile salt aggregates in aqueous solution
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Bile salt aggregates incorporate aqueous-insoluble photochromic compounds. The photochromism of a spiropyran (1, 1′,3′,3′-trimethyl-6-nitrospiro[2H-1]-benzopyran-2,2′-indoline) and a diarylethene derivative (2, 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene) was quantified in different bile salt aggregates. These aggregates act as efficient hosts to solubilize aqueous insoluble photochromic compounds where either both isomers are nonpolar, for example, 2, or compounds where one isomer is hydrophobic and the other is more polar, for example, 1. Methodology was developed to determine molar absorptivity coefficients for solutions containing both isomers and to determine the photoconversion quantum yields under continuous irradiation. The methods were validated by determining parameters in homogeneous solution, which were the same as previously reported. In the case of the colored isomer of 1, the molar extinction coefficient in ethanol at 537 nm ((3.68 ± 0.03) × 104cm-1M-1) was determined with higher precision. The quantum yields for the photoconversion between the isomers of 2 were shown to be the same in cyclohexane and in the aggregates of sodium cholate (NaCh), deoxycholate (NaDC), and taurocholate (NaTC), showing that bile salt aggregates are not sufficiently rigid to affect the equilibrium between the two possible conformers of the colorless form. In contrast, for 1 the quantum yields for the conversion from the colorless to the colored isomer were higher in bile salts than in ethanol, and the quantum yield was highest in the more hydrophobic aggregates of NaDC, followed by NaCh and then NaTC. The structure of the bile salt had no effect on the quantum yield for the conversion of the colored to the colorless isomer of 1, but these values were higher than in ethanol. For all three bile salts, the absorption maximum for the colored form of 1 suggested that this isomer was located in an environment that is more polar than ethanol.
- Santos, Cerize S.,Miller, Allyson C.,Pace, Tamara C. S.,Morimitsu, Kentaro,Bohne, Cornelia
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- Characterization of organic photochromic materials as 3-D optical data storage media
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We present our work on data storage and characterization in photochromic materials, and have succeeded in recording data at a total of 26 overlapping layers. The effect of bit depth and bit size were investigated by varying exposure time of the sample to the laser pulses. Bit size and bit depth were found to increase with exposure time and optimizing their values would increase the density of the possible number of data stored in a photochromic medium.
- Kawata, Satoshi,Amistoso, Jose Omar
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- Direct Access by Mechanochemistry or Sonochemistry to Protonated Merocyanines: Components of a Four-State Molecular Switch
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Direct access to the protonated merocyanine forms of two substituted spiropyrans by mechanosynthesis or sonochemistry was explored. The compounds were formed by the condensation reaction of the methyleneindolium iodide salt with salicylaldehyde derivatives. X-ray crystallography, 1H NMR spectroscopy, ab initio geometry optimization, and absorption spectroscopy were combined to provide a better understanding of the four-state molecular switch system in which the newly synthesized protonated merocyanines were found to play a central role. The results of this study suggest that the stability of the protonated merocyanines requires acidic conditions, as treatment with base led to the corresponding unprotonated merocyanines, which in turn spontaneously converted into photochromic closed spiropyrans.
- Cola?o, Melwin,Carletta, Andrea,Van Gysel, Mégane,Robeyns, Koen,Tumanov, Nikolay,Wouters, Johan
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- Thermal isomerization of spiropyran to merocyanine in aqueous media and its application to colorimetric temperature indication
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Thermally-induced isomerization of spiropyran derivatives in aqueous media has been studied. The colorless spirocyclic (SP) forms of spiropyran derivatives are isomerized to colored merocyanine (MC) forms even in dark conditions at elevated temperature. Equilibrium, kinetic, and deuterium experiments reveal that the thermal SP → MC isomerization is due to the stabilization of MC form by a hydrogen bonding interaction with water molecules. This leads to the ground state energy of the MC form decreasing to lower than that of the SP form, resulting in SP → MC isomerization. The thermal isomerization property is applicable to a rough indication of solution temperature. The spiropyran derivatives, when dissolved in aqueous media under irradiation of visible light with an appropriate light intensity, demonstrate an increase in MC absorbance with a rise in temperature. The absorption response occurs reversibly regardless of the heating/cooling sequence. The spiropyran derivatives therefore have a potential for colorimetric temperature indication.
- Shiraishi, Yasuhiro,Itoh, Masataka,Hirai, Takayuki
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- Effect of the Phase Transition of a Bilayer Membrane on the Thermal Decolouration of a U.V.-irradiated Indolinospirobenzopyran
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The kinetic parameters for the thermal decolouration of u.v.-irradiated spiropyran derivatives incorporated in a bilayer vesicle membrane were affected by the crystal to liquid crystal phase transition.
- Seki, Takahiro,Ichimura, Kunihiro
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- Conductance Photoswitching of Metal–Organic Frameworks with Embedded Spiropyran
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Conductive metal–organic frameworks (MOFs) as well as smart, stimuli-responsive MOF materials have attracted considerable attention with respect to advanced applications in energy harvesting and storage as well as in signal processing. Here, the conductance of MOF films of type UiO-67 with embedded photoswitchable nitro-substituted spiropyrans was investigated. Under UV irradiation, the spiropyran (SP) reversibly isomerizes to the open merocyanine (MC) form, a zwitterionic molecule with an extended conjugated π-system. The light-induced SP–MC isomerization allows for remote control over the conductance of the SP@UiO-67 MOF film, and the conductance can be increased by one order of magnitude. This research has the potential to contribute to the development of a new generation of photoelectronic devices based on smart hybrid materials.
- Garg, Shubham,Schwartz, Heidi,Kozlowska, Mariana,Kanj, Anemar Bruno,Müller, Kai,Wenzel, Wolfgang,Ruschewitz, Uwe,Heinke, Lars
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- Photo- and solvatochromic properties of nitrobenzospiropyran in ionic liquids containing the [NTf2]- anion
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The photo-, thermo- and solvatochromic properties of 2,3-dihydro-1′, 3′,3′-trimethyl-6-nitrospiro-[1-benzopyran-2,2′-1H-indole] (BSP-NO2) were studied in ILs containing the anion [NTf 2]- by UV-Vis absorption spectroscopy, ab initio molecular orbital theory and density functional theory (DFT) calculations. It was found that the kinetics and thermodynamics of the BSP-NO2 ? MC (merocyanine) equilibrium was sensitive to the nature of the cation. It was also observed that the imidazolium cation can form a through-space orbital interaction with the MC isomer, rather than a simple electrostatic interaction, thus preventing the MC conversion back to the BSP-NO2 isomer. The BSP-NO2 ? MC equilibrium thus serves as a model system for studying modes of interaction of the cations in ionic liquids. the Owner Societies.
- Byrne, Robert,Fraser, Kevin J.,Izgorodina, Ekaterina,MacFarlane, Douglas R.,Forsyth, Maria,Diamond, Dermot
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- Transmission spectroscopy and kinetics in crystalline solids using aqueous nanocrystalline suspensions: The spiropyran-merocyanine photochromic system
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A comparison of the solution and solid state thermal decay kinetics of five photochromic spiropyrans with different N-Alkyl groups (SP1-SP5) was carried out in acetonitrile and nanocrystalline suspensions at 298 K. The change in absorbance at ca. 550 nm was measured as a function of time for the merocyanine (MC) using transmission UV-vis spectroscopy. We found that the thermal decay kinetics are slower and follow a biexponential decay in the solid state compared to a faster, monoexponential decay that was measured in solution. We observed that, while the kinetic range measured in solution varies by a factor of 13, the decay kinetics in the solid state cover a range of ca. 150, indicating that crystal packing has an influence much greater than that of the effects of N-Alkyl substitution. A fluorescence analysis of irradiated samples of SP1 in solution could be used to determine the formation of the MC species and its subsequent decay. By contrast, a similar analysis of nanocrystalline suspensions displayed changes as a function of time that are consistent with selfquenching.
- Breslin, Vanessa M.,Garcia-Garibay, Miguel A.
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- Influence of Disc-Rod-Sphere Phase Transitions in Nematic Lyotropics on a Unimolecular Isomerization Reaction
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The unimolecular isomerization of a photochromic merocyanine to an indolinospiropyran was performed in the nematic lyophases formed by potassium laurate (KL) or sodium decyl sulfate (SDS) with 1-decanol and water.In both systems there are discontinuities in reaction rates as a function of concentration or temperature which correspond to the phase transitions from disc- to rod- to sphere-like aggregates.Because of the change in molecular shape during the reaction, the order parameters of the reactant and products are quite different, and also reflect the differences between the rod- and disc-like phases in their ability to order the solute.The micropolarity and bulk viscosities of these phases are not very different, but microviscosity changes are the most likely explanation for the rate discontinuities at the phase transitions.
- Ramesh, V.,Labes, M. M.
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- Synthesis and studies of photochromic properties of spirobenzopyran carboxy derivatives and their model compounds as potential markers
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A number of photochromic markers, viz., spirobenzopyrans containing one or two active carboxy groups attached directly or through a spacer, as well as their model derivatives, were synthesized. The obtained compounds were characterized by instrumental methods of analysis. Spectrokinetic methods were used to study the behavior of the spirobenzopyran markers and the model derivatives in solutions in EtOH and toluene.
- Laptev,Lukin,Belikov,Zvezdin,Demina,Barachevsky,Varfolomeev,Khodonov,Shvets
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- THERMAL AND PHOTOSTABILITY OF 5',7'-DIALKOXY-5,6'-DINITRO-1,3,3,-TRIMETHYLSPIRO(INDOLIN-2,2'-CHROMENES)
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Some photochromic indoline spiropyrans have been synthesized and their thermal and photostability examined in films and in solution.Introduction of the NO2 group into the indoline moiety of the molecule stabilized the spiropyran form in solution and in films, but blocking the NO2 group in the pyran moiety by adjacent alkoxy groups enhances the light stability of the compounds.
- Arsenov, V. D.,Manakova, I. V.,Przhiyalgovskaya, N. M.,Suvorov, N. N.
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- LIQUID CRYSTALLINE SOLVENTS AS MECHANISTIC PROBES - 7. INVESTIGATION OF A PHOTOCHROMIC MEROCYANINE TO INDOLINOSPIROPYRAN ISOMERIZATION IN THE ISOTROPIC AND SMECTIC PHASES OF N-BUTYL STEARATE AND IN POLYBUTADIENE OLIGOMERS.
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The unimolecular isomerization of a merocyanine (t - 2a) to an indolinospiropyran, 1 prime , 3 prime , 3 prime -trimethyl-6-nitrospiro left bracket 2H-benzopyran-2,2 prime -indoline right bracket (1a), has been followed in the isotropic and smectic liquid crystalline phases of n-butyl stearate (BS) and in three polybutadiene oligomers (PB). The rate constants, k// minus //t, for isomerization in PB demonstrate that viscosity is not a factor as long as the solvent chains are mobile. The k// minus //t for all three PB fractions ( eta 13. 1-506 cP) at 25 degree C range only from 1. 0 - 3. 6 min** minus **1. Comparison of the activation parameters in the two phases of BS with each other and with other solvents reveals that polarity considerations, although important, are incapable of explaining the data completely. The effect of solvent order on the activation parameters must be included.
- Otruba III,Weiss
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- Photocyclization of diarylethenes: The effect of imidazole on the oxidative photodegradation process
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We have studied the photoreaction of 1,2-diarylethenes under aerobic conditions in the presence of various amines to prevent side processes promoted by singlet oxygen. It has been found that the most amines quite effectively deactivate processes associated with singlet oxygen, but primary and secondary amines unlike tertiary ones, react with substrates resulting in various side products. Among the studied amines, the most effective additive for preventing side processes, including those associated with singlet oxygen is imidazole, which is practically not consumed in photoreaction. It was shown that imidazole can also prevents the photodegradation of organic photochromes in solutions. The results obtained can be used in various branches of science, technology and medicine to improve the photostability of photosensitive organics (dyes).
- Zakharov,Lvov,Rostovtseva,Metelitsa,Chernyshev,Krayushkin,Yadykov,Shirinian
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- Entropy-driven thermal isomerization of spiropyran in viscous media
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Effects of solvent viscosity on the thermal isomerization properties of a spiropyran derivative have been studied in glycerol, ethylene glycol, 1,4-butanediol, and ionic liquid solutions. Thermal isomerization of the colorless spirocyclic (SP) form to the colored merocyanine (MC) form is enhanced with an increase in the concentrations of viscous solvents in solution. Equilibrium absorption analysis revealed that the enhanced SP → MC isomerization in viscous media is due to the strong solvent-solvent interaction, which suppresses the ordering of solvent molecules around the MC form. This results in a positive entropy change for isomerization and, hence, promotes entropy-driven isomerization. Kinetic absorption analysis revealed that the solvent viscosity scarcely affects the thermal activation process for isomerization, where the activation enthalpy and entropy parameters are solely affected by the solvent polarity.
- Shiraishi, Yasuhiro,Inoue, Takuya,Sumiya, Shigehiro,Hirai, Takayuki
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- Photochromism and photopolymerization induced mesophase transitions in mixtures of spiropyran and mesogenic diacrylate
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A phase diagram of a binary mixture of photochromic molecule (spiropyran) and mesogenic diacrylate monomer has been established by means of differential scanning calorimetry and polarized optical microscopy. Subsequently, a theoretical phase diagram has been calculated by self-consistently solving the combined Flory-Huggins free energy for isotropic mixing, Maier-Saupe free energy for nematic ordering, and phase field free energy for crystal solidification. The phase diagram thus obtained consists of various coexistence regions involving single-phase crystals, pure nematic, crystal + liquid, crystal + nematic, and crystal + crystal coexistence gaps. Under UV irradiation, both SP and SP/RM257 mixtures showed the lowering trend of the melting points, which may be attributed to the plasticization effect by the merocyanine isomers. When UV light is illuminated on the 2/98 SP/RM257 mixture for an extended period, mesogenic diacrylate in the mixtures gets polymerized, showing the permanent fixation of isotropic and nematic structures due to the network formation of RM257 caused by the biradicals in the merocyanine intermediate.
- Kim, Namil,Lam, Harris,Kyu, Thein
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- On-Tip Photo-Modulated Molecular Printing
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The concept of using cantilever-free scanning probe arrays as structures that can modulate nanoscale ink flow and composition with light is introduced and evaluated. By utilizing polymer pen arrays with an opaque gold layer surrounding the base of the transparent polymer pyramids, we show that inks with photopolymerizable or isomerizable constituents can be used in conjunction with light channelled through the pyramids to control ink viscosity or composition in a dynamic manner. This on-tip photo-modulated molecular printing provides novel chemically and mechanically controlled approaches to regulating ink transport and composition in real time and could be useful not only for rapidly adjusting feature size but also for studying processes including photoreactions and mass transport at the nanoscale, self-assembly, and cell-material interactions.
- Xie, Zhuang,Zhou, Yu,Hedrick, James L.,Chen, Peng-Cheng,He, Shu,Shahjamali, Mohammad M.,Wang, Shunzhi,Zheng, Zijian,Mirkin, Chad A.
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- Photochromism of nitrobenzospiropyran in phosphonium based ionic liquids
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The photo-, thermo- and solvatochromic properties of 2,3-dihydro-1′, 3′,3′-trimethyl-6-nitrospiro[1-benzopyran-2,2′-1H-indole] (BSP) and its photo-induced merocyanine isomer (MC) were investigated in phosphonium based ILs by UV-vis absorption spectroscopy. It was found that the kinetics and thermodynamics of the BSP ? MC equilibrium were sensitive to the nature of the anion. The MC λmax shifted from 560 nm to 578 nm when in solutions of [P1,4,4,4][tos] and [P 6,6,6,14][dca], respectively. The BSP isomer was highly favoured at equilibrium in the ILs studied; Ke values observed were similar to non-polar solvents such as dichloromethane. The thermal relaxation of MC in all ILs is first order, and in comparison with aprotic polar solvents possessing comparable polarity (such as acetonitrile). Thermal relaxation rates of MC were monitored over a range of temperatures; at 293 K rates varied from 5.19 to 25.03 × 10-4 s-1. A non-linear relationship between Ke and k was observed; this contradicts what is expected for BSP in molecular solvents and suggests the isomers exhibit different molecular/solvation environments. The energetics of the thermal relaxation of MC in ILs were observed; activation energies ranged from 71 to 90 kJ mol -1 and all ILs exhibit negative activation entropies ranging between -72 and -8.2 J K-1 mol-1. A linear relationship between activation energy and entropy was observed.
- Byrne, Robert,Coleman, Simon,Fraser, Kevin J.,Raduta, Ana,MacFarlane, Douglas R.,Diamond, Dermot
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- Spiropyran-merocyanine equilibrium in presence of organic acids and bases
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Manipulation of the rate of thermal reversion of N-functionalized merocyanines (MC) to the corresponding spiropyran isomers in the dark, was demonstrated by using both organic acid and base additives. In the presence of organic bases, increase or decrease of the rate of reaction was dependent on the solvent used. When organic acids were used, in all cases the reaction rate decreased when compared with the system containing no acid. Similar behavior was also observed in polymer films. This approach is of interest for applications in the design of optical switches and memory with enhanced stability of the stored information.
- Xiao, Ningning,Chen, Yu,Lemieux, Robert,Buncel, Erwin,Iftime, Gabriel,Kazmaier, Peter M.
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- Micro-environmental fine-tuning of electronic and kinetic properties of photochromic dyes
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Despite the recognition of the importance of Spiropyran (SP)-Merocyanine (MC) photochromic materials in molecular switching, the majority of studies have been reported in solution with relatively few in the solid-state as required in modern displays and other devices. In contrast, the present work bridges solution, condensed phase and solid-phase media and is to our knowledge the first micro-environmental study on electronic and kinetic effects for the SP-MC system. Expanding on our previous work we have investigated the photochromic properties of an SP molecule (1b) attached to a 100 μm commercially available polystyrene micro-particle (Wang Resin). The thermal MC → SP reversion kinetics (5a,b → 4a,b and 2a,b → 1a,b) which reflect the critical lifetime of the open MC form were measured. Reduction in kobs of thermal reversion, MC → SP, up to two orders of magnitude, and a blue-shift up to 58 nm was observed with the potential for tailoring or fine tuning. The use of polymeric micro-particles in controlling both electronic and kinetic properties of photochromic molecular switches has been highlighted. The Royal Society of Chemistry 2010.
- Whelan, Jamie,Abdallah, Dalia,Wojtyk, James,Buncel, Erwin
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- A highly selective probe for fluorescence turn-on detection of Fe3+ ion based on a novel spiropyran derivative
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A new spiropyran bearing multiple phenolic hydroxyl groups is synthesized. It acts as a chemosensor for selective detection of Fe3+ ions in both organic and aqueous solution. The optimal pH range for Fe3+ fluorescent detection by the sensor is pH 4.5–10.5. Upon addition of Fe3+ to the sensor solution the fluorescence emission intensity is enhanced by around 50 fold. Other common competitive metal ions including Li+, Na+, K+, Ag+, Cu2+, Fe2+, Zn2+, Co2+, Ni2+, Mn2+, Sr2+, Hg2+, Ca2+, Mg2+, Al3+ and Cr3+ do not substantially interfere with the selective detection of Fe3+ by the sensor. Changes in the fluorescence emission intensity with the equivalent ratio of Fe3+/sensor exhibits an approximate linear relationship, from which the concentration of Fe3+ ion may be estimated. The detection limit of Fe3+ ion by the sensor is measured to be 1.93 × 10–7 M. A plausible sensing mechanism for selective Fe3+ ion detection by the sensor is proposed based on the Job's plot measurement.
- Zhang, Ruiqing,Hu, Luping,Xu, Zhenxiang,Song, Yanxi,Li, Hongqi,Zhang, Xin,Gao, Xucheng,Wang, Mengxuan,Xian, Chunying
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- Reversible regulation of pyrene excimer emission by light and metal ions in the presence of photochromic spiropyran: Toward creation of a new molecular logic circuit
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The excimer fluorescence of a bis-pyrene molecule can be reversibly regulated by ultraviolet light, metal ions and visible light in the presence of spiropyran. Based on this result, a new molecular logic circuit is proposed.
- Guo, Xuefeng,Zhang, Deqing,Wang, Tongxin,Zhu, Daoben
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- Aqueous solubilization of photochromic compounds by bile salt aggregates
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Bile salts form aggregates in aqueous solutions which were shown to efficiently solubilize aqueous insoluble photochromic compounds. Photochromic switching was observed for a spiropyran and a diarylethene. In the case of the spiropyran, the incorporation into the bile salt aggregate led to improved hydrolytic stability and changes in thermal rate constants. The Royal Society of Chemistry 2010.
- Li, Rui,Santos, Cerize S.,Norsten, Tyler B.,Morimitsu, Kentaro,Bohne, Cornelia
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- Reversible photorheological fluids based on spiropyran-doped reverse micelles
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We describe a new class of photorheological (PR) fluids whose rheological properties can be reversibly tuned by light. The fluids were obtained by doping lecithin/sodium deoxycholate (SDC) reverse micelles with a photochromic spiropyran (SP) compound. Initially, the lecithin/SDC/SP mixtures formed highly viscoelastic fluids, reflecting the presence of long, wormlike reverse micelles. Under UV irradiation, the SP was isomerized to the open merocyanine (MC) form, causing the fluid viscosity to decrease 10-fold. When the UV irradiation was switched off, the MC reverted to the SP form, and the viscosity recovered its initial value. This cycle could be repeated several times without loss of response. The rheological transitions are believed to reflect changes in the lengths of the reverse worms. To our knowledge, this is the first example of a simple, reversible PR fluid that can be made entirely from commercially available components.
- Lee, Hee-Young,Diehn, Kevin K.,Sun, Kunshan,Chen, Tianhong,Raghavan, Srinivasa R.
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- Photochromic reaction of 6-nitro-1',3',3'-trimethylspiro: time-resolved resonance Raman and absorption study
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Time-resolved resonance Raman spectra and time-resolved absorption spectra of transient species of photochromic 6-nitro-1',3',3'-trimethylspiro-1-benzopyran-2,2'-indoline> (6-nitroBIPS) generated by irradiation with UV light in cyclohexane have been measured.Three transients were observed to appear sequentially in the nanosecond-microsecond time region.The first transient (transient I) with the shortest lifetime is identified as the T1 state of photomerocyanine having an open structure (spiro C-O bond-cleaved).The second transient (transient II) is attributed to photomerocyanine produced from transient I, and the last transient to appear (transient III) having the longest lifetime is assigned to a dimeric species of photomerocyanine because of the quadratic dependence of its quantum yiel on both the pump UV laser power and the concentration of the solution.It is concluded that the cleavage of the spiro C-O bond occurs in the S1 state of the parent species.
- Yuzawa, Tetsuro,Shimojima, Atsushi,Takahashi, Hiroaki
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- Synthesis of stereochemically-biased spiropyrans by microwave-promoted, one-pot alkylation-condensation
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A microwave-assisted, two-step, one-pot synthesis of spiropyrans has been developed. This process was used to synthesise a range of sterically-congested spiropyrans from readily available precursors, employing environmentally benign solvents. The unusual substituent pattern possessed by these structures has been shown to influence the stereoselectivity of spiropyran ring-closure.
- Perry, Alexis,Davis, Kane,West, Lara
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- Photochromic transformations of 6-nitrospiropyran in matrices of linear and branched polymers
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Photochromic transformations of 6-nitrospiropyran in matrices of linear polystyrene and poly(methyl methacrylate) and branched polymethacrylates of various composition and structure were studied by absorption spectroscopy. In the case of linear polymers the kinetics of bleaching of the colored merocyanine form of 6-nitrospiropyran is determined by polarity and molecular mobility of the polymer matrix. The kinetic regularities of merocyanine transformations into the initial spiropyran in the branched polymer matrices are apparently caused by specific features of their architecture, differences in the degree of branching, and the properties associated with molecular mobility.
- Kurmaz,Kochneva,Perepelitsina,Korolev,Grachev,Aldoshin
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- Determination of critical aggregation concentrations of self-assembling lipids in nonpolar organic media using spiropyrans as photochromic probes
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Critical aggregation concentrations of organic gel-forming lipids in nonpolar organic media such as benzene were found to be determined by measuring the first-order rate constants of merocyanine-to-spiropyran thermal isomerizations for spiropyrans added as probes.
- Hachisako, Hiroshi,Nakayama, Hiroki,Ihara, Hirotaka
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- Acid-base isomerization of hybrid molecules based on fullerene C60 and spiropyrans
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The reversible acid-base isomerization of fullerene C60 hybrid compounds with spiropyrans has been performed for the first time. It has been found that irradiation induces isomerization only for hybrid bearing NO2 group in the photochromic spiropyran part, while the treatment with trifluoroacetic acid induces isomerization for compounds containing NO2, Cl or F, i.e. irrespective of the nature of substituent in the spiropyran moiety.
- Tuktarov, Airat R.,Khuzin, Artur A.,Dzhemilev, Usein M.
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- A colour tunable microcavity by weak-to-strong coupling regime transition through a light-switchable material
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An organic based microcavity showing fully reversible colour tunability has been achieved for the first time. The emission output changes according to the modulation from pure photonic to polaritonic resonant modes through UV irradiation of the light-switchable matrix.
- Accorsi, Gianluca,Carallo, Sonia,Mazzeo, Marco,Genco, Armando,Gambino, Salvatore,Gigli, Giuseppe
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- Ultraviolet-light-responsive liquid marbles
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Photoresponsive liquid marbles were prepared using spiropyran (SP) powder. The liquid marbles were transferred to a Petri dish containing water and remained stable on the water surface for more than a week in the dark. The liquid marbles disintegrated immediately upon irradiation with ultraviolet (UV) light.
- Nakai, Keita,Fujii, Syuji,Nakamura, Yoshinobu,Yusa, Shin-Ichi
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- Time-resolved thermodynamic profile upon photoexcitation of a nitrospiropyran in cycloalkanes and of the corresponding merocyanine in aqueous solutions
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The photoconversion of 2′,3′-dihydro-6-nitro-1′,3′,3′- trimethylspiro[2H-1-benzopyran-2,2′-indole] (Sp) to its open merocyanine form (Mc) in a series of aerated cycloalkanes (cyclopentane, cyclohexane, and trans- and cis-decalin) and of the protonated merocyanine (McH+) to Sp in aqueous solution were studied by laser-induced optoacoustic spectroscopy (LIOAS), The + (11 ± 2) ml mol-1 expansion determined for the ring closure is due to deprotonation of McH+ plus the reaction of the ejected proton with the monoanion of malonic acid (added to stabilize Mc), an intrinsic expansion and a small electrostriction term. The energy difference between Sp and initial McH+ is (282 ± 110) kJ mol-1. An intrinsic contraction of - (47 ± 15) ml mol-1 occurs upon ring opening, forming triplet 3Mc in the cycloalkanes, whereas no volume change was detected for the 3Mc to Mc relaxation. Electrostriction decreases the 3Mc energy, (165 ± 18) kJ mol-1; to 135 kJ mol-1. The difference in the values of the ring-opening (Sp to Mc) reaction enthalpy in cycloalkanes as derived from the temperature dependence of the Sp?Mc equilibrium, (29 ± 8)kJ mol-1, and from the LIOAS data, - (9 ± 25) kJ mol-1, is due to the formation of Mc-Sp aggregates during steady-state measurements. The Sp-sensitized singlet molecular oxygen, O2(1Δg), quantum yield (average ΦΔ = 0.58 ± 0.03) derived from the near-IR emission of O2(1Δg), was taken as a measure of Mc production in the cycloalkanes. These solvents, albeit troublesome in their handling, provide an additional series for the determination of structural volume changes in nonaqueous media, besides the alkanes already used.
- Williams, Rene M.,Klihm, Gudrun,Braslavsky, Silvia E.
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- Spectroscopy and thermal decay of a photomerocyanine in mixtures of polar and nonpolar solvents
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Absorption and emission spectra of the merocyanine (MC) form of 6- nitrobenzospiropyran (SP), as well as the kinetics of the thermal decay of MC to SP, were measured in solvent mixtures of ethanol-hexane, ethanol-toluene and acetonitrile-toluene. For all these mixtures, the Stokes shift of MC shows the same linear dependence with the solvent parameter E(T)(30). The thermal decay kinetics is monoexponential in acetonitrile-toluene mixtures and biexponential in those containing ethanol. The activation parameters of the rate constants display very different behaviours with E(T)(30): whereas ΔG≠ is linear in this parameter, E(a) shows abrupt variations with this polarity parameter. This is compensated by changes in ΔS≠, resulting in a linear correlation between E(a) and ΔS≠.
- Wetzler, Diana E.,Aramendia, Pedro F.,Japas, Maria Laura,Fernandez-Prini, Roberto
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- Mixed Solvent Chemistry through Synergistic Solvation: Structure, Property and Function of t-Butanol—Dichloromethane Binary Solvent Mixtures
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The present study elucidates the synergetic solvation behavior of t-butanol–dichloromethane (t-BuOH–DCM) binary solvent mixtures. UV–visible absorption, emission and 1H-NMR spectroscopy along with analytical modelling were used to ascertain the nature of interactions present, which are found to be maximum at Xt-BuOH?=?0.40, leading to a super solvation environment. The increased polarity of the t-BuOH–DCM binary solvent mixtures through interactive solvent association is believed provide a unique reaction medium that can alter the fate of chemical processes involving a polar species. This idea has been demonstrated by the transformation of merocyanine to 1′,3′-dihydro-,1′,3′,3′-trimethyl-6-nitropiro[2H-1-benzopyran-2,2′-(2H)-indole] and the oxidation of cholestanol to cholestanone.
- Gupta, Shradhey,Parida, Keshaba Nanda,Mukherjee, Puspal,Sen, Pratik
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- Photochromism of Spiropyrans in Organized Molecular Assemblies. Formation of J- and H-Aggregates of Photomerocyanines in Bilayers-Clay Matrices
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Photochromism of a series of 1'-alkyl-3',3'-dimethyl-6-nitro-8-alkanoyloxymethylspiro(2H-1-benzopyran-2,2'-indoline) derivatives (SPs) having different lengths of their alkyl chains has been investigated in didodecyldimethylammonium chloride-clay matrices; stable H (parallel type) and J (head-to-tail type) aggregates of photo-merocyanines are formed when SPs containing an appropriate length of alkyl chains are irradiated.
- Tomioka, Hideo,Itoh, Toshio
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- Local molecular dynamics of poly(ethylene glycol) dimethacrylate synthesized in the presence of branched poly(methyl methacrylate): A photochromic probe study
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The local molecular dynamics and morphology of poly(ethylene glycol) dimethacrylate networks synthesized in the presence of 0-40% branched poly(methyl methacrylate) were studied using a photochromic probe (6-nitrospiropyran). The change in the free volume of the polymer in the vicinity of the photochromic probe was monitored by the rate of dark bleaching of merocyanine (colored form of 6-nitrospiropyran). The local free volume and the mobility of the polymer chain fragments decrease as the conversion of C=C bonds and the content of branched poly(methyl methacrylate) in the polymer increase. ; 2009 Springer Science+Business Media, Inc.
- Kurmaz,Ozhiganov,Berezin
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- Synthesis, optical properties and in vitro cell viability of novel spiropyrans and their photostationary states
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A novel class of spiropyran (SP) was synthesized using a multistep process that involves three key intermediates: (a) diazonium-tetrafluoroborate, (b) hydrazine and (c) indolium iodide. Single crystal X-ray spectroscopy was used to confirm the structure of one of the analogues. The SP analogues were confirmed as being able to isomerize and attain a photostationary state (PSS) upon irradiation with ultraviolet light (UV, 365 nm) in an aqueous environment. UV–visible absorption spectra were recorded to confirm the isomerization properties. The ability of the synthesized compounds to induce growth inhibition of HeLa cervical cancer cells was assessed via the MTT assay after incubation with either the SP or their PSS. The IC50 values of two PSS (PSS-2, 4), were observed to be around 14 ± 4 fold lower (26 ± 3 μM) than their corresponding SPs. The most cytotoxic compounds SP-7 and PSS-7 showed the lowest IC50 values (12 μM). An in vitro tubulin polymerization assay showed that SP-7 and PSS-7 exhibited the greatest difference in tubulin inhibition relative to unirradiated SP-1 and SP-4.
- Rastogi, Shiva K.,Zhao, Zhenze,Gildner, M. Brenton,Shoulders, Ben A.,Velasquez, Tara L.,Blumenthal, Madeleine O.,Wang, Lei,Li, Xiaopeng,Hudnall, Todd W.,Betancourt, Tania,Du, Liqin,Brittain, William J.
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- Synthesis method for producing 1,3,3-trimethylindolinobenzopyrylospiran through one-pot method
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The invention discloses a synthesis method for producing 1,3,3-trimethylindolinobenzopyrylospiran through a one-pot method, and belongs to the field of organic synthesis. The synthesis method for producing the 1,3,3-trimethylindolinobenzopyrylospiran through the one-pot method comprises the steps of using 2,3,3-trimethylindolenine, iodomethane and 5-nitrosalicylaldehyde as raw materials and usingalkali as a catalyst, and carrying out reaction to produce the 1,3,3-trimethylindolinobenzopyrylospiran. The method is simple in technology, the reaction is completed in one pot, in the reaction process, anhydrous and anaerobic operation is not needed, and the synthesis method for producing the 1,3,3-trimethylindolinobenzopyrylospiran through the one-pot method has the advantages that the synthesis efficiency is high, and little chemical waste is generated.
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Paragraph 0016-0024
(2019/08/20)
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- Novel Spiropyran Based Composition and Application Thereof as Security Tag
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The present invention discloses the spiropyran compound of formula (I), process for preparation thereof and a composition comprising spiropyran compound of formula (I) on a support, wherein said support selected from polymers such as Poly (ethylene oxide), Polydimethylsiloxane (PDMS), Ethylene propylene diene monomer (EPDM).
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- Greener route for the synthesis of photo- and thermochromic spiropyrans using a highly efficient, reusable, and biocompatible choline hydroxide in an aqueous medium
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Here, we report the synthesis of photo- and thermochromic spiropyrans promoted by a highly efficient, biocompatible, and reusable choline hydroxide (ChOH) in greener solvent water. This procedure provides several advantages such as simple workup, mild reaction conditions, short reaction time, and high yields of the products. Furthermore, the ChOH could be reused at least five times without significantly losing its catalytic activity. The structures of the synthesized spiropyran derivatives were confirmed by several characterization methods such as 1H NMR, 13C NMR, and mass spectra.
- Pargaonkar, Jyotsna G.,Patil, Sanjay K.,Vajekar, Shailesh N.
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supporting information
p. 208 - 215
(2017/12/26)
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- Combined In Situ Illumination-NMR-UV/Vis Spectroscopy: A New Mechanistic Tool in Photochemistry
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Synthetic applications in photochemistry are booming. Despite great progress in the development of new reactions, mechanistic investigations are still challenging. Therefore, we present a fully automated in situ combination of NMR spectroscopy, UV/Vis spectroscopy, and illumination to allow simultaneous and time-resolved detection of paramagnetic and diamagnetic species. This optical fiber-based setup enables the first acquisition of combined UV/Vis and NMR spectra in photocatalysis, as demonstrated on a conPET process. Furthermore, the broad applicability of combined UVNMR spectroscopy for light-induced processes is demonstrated on a structural and quantitative analysis of a photoswitch, including rate modulation and stabilization of transient species by temperature variation. Owing to the flexibility regarding the NMR hardware, temperature, and light sources, we expect wide-ranging applications of this setup in various research fields.
- Seegerer, Andreas,Nitschke, Philipp,Gschwind, Ruth M.
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supporting information
p. 7493 - 7497
(2018/04/02)
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- A Multiaddressable Dyad with Switchable Cyan/Magenta/Yellow Colors for Full-Color Rewritable Paper
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Reversible multicolor displays on solid media created from single-molecule pigments are a long-awaited goal. Herein, a new and simple molecular dyad, which can undergo switchable cyan (C), magenta (M), and yellow (Y) color changes in both solution and the solid state upon exposure to light, water/acid, and nucleophiles, has been designed and synthesized. The stimuli used herein can be applied independent of each other, which is beneficial for color changes without mutual interference. For comparison, mixtures of the two molecular switching motifs that form the basis of the dyad were also studied. The dyad greatly outperforms the corresponding mixed system with respect to reversible color switching on the paper substrate. Its potential for full-color rewritable paper with excellent reversibility has been demonstrated. Legible multicolor prints, that is, high color contrast and resolution, good dispersion, and excellent reversibility, were achieved by using common water-jet and light-based printers. This work provides a very promising approach for the further development of full-color switchable molecules, materials, and displays.
- Qin, Tianyou,Han, Jiaqi,Geng, Yue,Ju, Le,Sheng, Lan,Zhang, Sean Xiao-An
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supporting information
p. 12539 - 12545
(2018/09/10)
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- Shining new light on the spiropyran photoswitch: A photocage decides between cis-trans or spiro-merocyanine isomerization
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Photochromic molecules from the spiropyran family are known to undergo light-induced interconversion between the colorless spiro- and the colored merocyanine forms. Here, we show for the first time that small structural modifications open up for an additional photoisomerization mode: reversible cis-trans isomerization of the merocyanine. Moreover, the introduction of a photocage allows for light-activated switching between the two modes.
- Fleming, Cassandra L.,Li, Shiming,Grotli, Morten,Andréasson, Joakim
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supporting information
p. 14069 - 14072
(2018/10/31)
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- Comparative Evaluation of Substituent Effect on the Photochromic Properties of Spiropyrans and Spirooxazines
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Spiropyrans and spirooxazines represent an important class of photochromic compounds with a wide variety of applications. In order to effectively utilize and design these photoswitches it is desirable to understand how the substituents affect photochromic properties, and how the different structural motifs compare under identical conditions. In this work a small library of photoswitches was synthesized in order to comparatively evaluate the effect of substituent modifications and structure on photochromism. The library was designed to modify positions that were believed to have the greatest effect on C-O bond lability and therefore the photochromic properties. Herein we report a comparative analysis of the UV and visible light responses of 30 spiropyrans, spiroindolinonaphthopyrans, and spirooxazines. The influence of gadolinium(III) binding was also investigated on the library of compounds to determine its effect on photoswitching. Both assays demonstrated different trends in substituent and structural requirements for optimal photochromism.
- Balmond, Edward I.,Tautges, Brandon K.,Faulkner, Andrea L.,Or, Victor W.,Hodur, Blanka M.,Shaw, Jared T.,Louie, Angelique Y.
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supporting information
p. 8744 - 8758
(2016/10/14)
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- An off-the-shelf sensor for colourimetric detection of sulfide
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The cheap, accessible spiropyran nitroBIPS is a sensitive, selective colourimetric sensor for quantitative determination of sulfide in aqueous media at neutral pH.
- Perry, Alexis,Miles, Daniel
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p. 5788 - 5793
(2016/12/03)
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- Unusual thermo(photo)chromic properties of some mononitro- and dinitro- substituted 3′-alkyl indolospirobenzopyrans This paper is dedicated to the memory of Dr Thomas G. Nevell.
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Isomeric equilbria of dinitro-substituted indolospirobenzopyrans, possessing 3′-gem-methyl- or 3′-cyclohexyl-substitutents, have been investigated using 1H NMR spectroscopy at six temperatures, ranging from 298 K to 410 K; isomerisation processes in a methanolic solution have been monitored by spectrophotometry. For the mononitro-substituted compounds, equilibrium favoured the colourless spirocyclic isomers. Reversion of the coloured merocyanine isomers, generated by UV irradiation, followed first-order kinetics. For the dinitro-substituted compounds the coloured merocyanine isomers predominated. Following decolourisation by visible light photoirradiation, reversion towards the merocyanine structures were particularly slow, absorbances unusually increasing sigmoidally. UV. spectral observations for the gem-methyl- 1 and 3′-cyclohexyl-substituted systems 2 are qualitatively consistent with the simultaneous involvement of two relatively slow rate determining steps, possessing slowly forming and long-lived intermediates - postulated to be the oxygen protonated pyran-ring of the spirocyclic structure and TCC merocyanine isomer, the latter undergoing relatively slow isomerisation about the central β-alkenic bond to the TTC isomer.
- Abdullah, Ayse,Nevell, Thomas G.,Sammes, Peter G.,Roxburgh, Craig J.
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- Synthesis and photochromic properties of methacryloxy 6- nitrospirobenzopyrans
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The synthesis and spectroscopic characterization of several methacryloxy-modified spiropyran dyes is reported. The dyes were found to have similar photochromic isomerization rates relative to a commercially available reference compound in solution. The methacryloxy-modified dyes were also successfully incorporated into polymer matrices, where they retained their ability to photoisomerize and complex with cobalt (II) and zinc (II) ions.
- Sennett, Kelly A.,Lindner, Brian K.,Kaur, Navdeep,Fetner, Shannon M.,Stitzel, Shannon E.
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p. 437 - 441
(2013/07/25)
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- Interaction studies between photochromic spiropyrans and transition metal cations: The curious case of copper
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A series of four spiropyrans bearing different substituents on the indolic nitrogen were synthesized and their capability of binding mono and bivalent transition metal cations in solution was assessed via UV-visible absorption spectroscopy. All the compounds responded selectively to the presence of Cu(ii) ions producing intense absorption bands in the visible region of their spectra. Bidimensional 1H-NMR and MALDI-TOF MS spectroscopies revealed the formation of SP dimers mediated by Cu(ii). This is the first example of cross-coupling mediated by copper(ii) in mild conditions causing the symmetric dimerization of spiropyran dyes. The Royal Society of Chemistry 2012.
- Natali, Manuel,Giordani, Silvia
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p. 1162 - 1171
(2012/03/07)
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- Rapid colorimetric sensing of cyanide anion in aqueous media with a spiropyran derivative containing a dinitrophenolate moiety
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A spiropyran derivative containing a dinitrophenolate moiety (2: 1′,3′,3′-trimethyl-6,8-dinitro-spiro-[2H-1-benzopyran-2, 2′-indoline]) behaves as a receptor for selective detection of cyanide anion (CN-) in aqueous media. Compound 2, when dissolved in aqueous media, spontaneously produces the spirocycle-opened merocyanine (MC) form even in dark condition. The absorption band of the MC form decreases selectively upon addition of CN-, via a nucleophilic addition of CN- to the spirocarbon of the MC form. The nucleophilic addition occurs very rapidly (within 1 min) and enables rapid and selective quantification of very low levels of CN- (>0.8 μM) by an absorption analysis.
- Shiraishi, Yasuhiro,Itoh, Masataka,Hirai, Takayuki
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supporting information; scheme or table
p. 1515 - 1519
(2011/05/16)
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- Steric and substituent control on the photoreversibility of some novel N-alkyl-3,3′-disubstituted-6-nitro-indolospirobenzopyrans: Evaluation using UV spectroscopic studies
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A series of novel 6-nitro substituted indolospirobenzopyrans are reported. The effects of substitution on their photoreversibility are investigated by: synthesising derivatives that possess sterically hindering (with regard to the spiropyran-opening ? closing) groups contained within the spirocyclic skeleton. Specifically, spirobenzopyrans possessing combinations of various N-alkyl, and/or, simultaneously, 3,3′-geminal methyl and/or cyclohexyl groups are synthesised. Further, these systems are evaluated in three solvents; methanol, acetonitrile and dichloroethane. The thermal decolourisation rates of the gem-dimethyl and 3,3′-cyclohexyl compounds are additionally evaluated at the temperature of 50 °C. The above systems, and changes in physical parameters are extensively evaluated, and the subsequent biasing of the equilibria established using UV spectroscopy. Rates of colourisation, decolourisation and the equilibrium constants are obtained. The overall photochromic 'tuneability' of these systems is subsequently established.
- Roxburgh, Craig J.,Sammes, Peter G.,Abdullah, Ayse
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experimental part
p. 146 - 162
(2011/12/04)
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- Spiropyran as a selective, sensitive, and reproducible cyanide anion receptor
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A spiropyran derivative (1) behaves as a selective and sensitive cyanide anion receptor in aqueous media under UV irradiation. The receptor can be reproduced just by irradiation with visible light.
- Shiraishi, Yasuhiro,Adachi, Kenichi,Itoh, Masataka,Hirai, Takayuki
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supporting information; experimental part
p. 3482 - 3485
(2009/12/08)
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- Stereoselective formation of dicondensed spiropyran product obtained from the reaction of excess Fischer base with salicylaldehydes: First full characterization by X-ray crystal structure analysis of a DC·acetone crystal
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The structure and stereochemistry of the dicondensed spiropyran product (DC-1, X=COOH) obtained from reaction of excess Fischer base with substituted salicylaldehydes has been fully assigned as C with (8R, 10R) configuration on the basis of single crystal X-ray diffraction analysis. The stereoselective formation of DC molecules indicates that the most plausible mechanism for DC formation involves dehydration of the cyclic carbinol intermediate with the aid of intramolecular H-bonding via transition structure TS1 ?.
- Keum, Sam-Rok,Ku, Byung-Soo,Shin, Jin-Taek,Jae, Jung Ko,Buncel, Erwin
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p. 6720 - 6725
(2007/10/03)
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- Photochromism of a spiropyran derivative of 1,3-calix[4]crown-5
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A new spiropyran derivative containing a calixcrown ring has been synthesised. Thermal conversion from merocyanine to the spiropyran form was studied in ethanol and in acetonitrile, and equilibrium and kinetic data were compared with those of the parent 6-nitrospiropyran. The kinetics of thermal decay of the merocyanine form of the calixcrown-spiropyran molecule shows a biexponential character in both solvents, while the decay is much slower in ethanol than in acetonitrile.
- Grofcsik, András,Baranyai, Péter,Bitter, István,Grün, Alajos,K?szegi, éva,Kubinyi, Miklós,Pál, Krisztina,Vidóczy, Tamás
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- Photochromism of nitrospiropyrans: Effects of structure, solvent and temperature
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The thermal and photochemical ring opening and ring closure of the spiropyran/merocyanine couple of three nitro-substituted spiropyrans (6-NO2: 6, 7 and 8-NO2: 8) were studied and the results were compared with those of other 6-NO2 spirobenzopyranindolines (BIPS) (1-5). The photocolouration, which occurs in the triplet manifold throughout, and the photochemical conversion and thermal relaxation of the two observable photomerocyanines into the closed spiropyran (Sp) form (decolouration) were quantified as a function of solvent polarity and temperature. The relaxation time (τt-Sp) at 25°C ranges from 2 s for 5 in methylcyclohexane to 104 s for 7 in ethanol. This large variation in τt-Sp is due to changes in both the activation energy (Ea = 75-105 kJ mol-1, increasing with polarity) and the pre-exponential factor (A = 1012-1015 s-1). The quantum yield of colouration with 308 nm pulses is substantial in solvents of low polarity (φcol = 0.3-0.8) and decreases (c→t = 30-40 kJ mol-1. The effects of substituents and medium properties are described and the mechanism of photochromism is discussed.
- Goerner
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p. 416 - 423
(2007/10/03)
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- Thermal racemization of substituted indolinobenzospiropyrans: Evidence of competing polar and nonpolar mechanisms
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A series of 6-substituted indolinobenzospiropyrans were resolved by chiral stationary phase HPLC and rate constants k(rac) for their thermal racemization were measured by circular dichroism spectropolarimetry at 60 °C in three different solvents: cyclohexane, 90:10 hexanes/2-propanol, and acetonitrile. Results show that the spiropyrans undergo thermal racemization most rapidly in acetonitrile, with k(rac) values ranging from 9.3 x 10 -5 to >5.0 x 10 -3 s -1, and least rapidly in cyclohexane, with k(rac) values ranging from 6.8 x 10 -6 to 4.6 x 10 -4 s -1. V-shaped plots of log k(rac) vs Hammett σ(p) constants in 90:10 hexanes/2-propanol and acetonitrile suggest that thermal racemization of the 6-substituted spiropyrans proceed via two competing mechanisms: a polar mechanism involving heterolytic C(sp3)-O bond cleavage with anchimeric assistance from the indoline nitrogen and a nonpolar electrocyclic ring opening mechanism with no anchimeric assistance from the indoline nitrogen. The outcome of this competition appears to be strongly influenced by solvent polarity: plots of log k(rac) vs σ(p) and σ- in cyclohexane show a near-linear correlation with negative slope, which is consistent with the nonpolar mechanism. However, an increase in solvent polarity results in a shift toward a linear correlation with positive slope, which is consistent with the polar mechanism.
- Swansburg, Susan,Buncel, Erwin,Lemieux, Robert P.
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p. 6594 - 6600
(2007/10/03)
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