Quasi-crystals from irradiated photochromic dyes in an applied electric field

Krongauz, Valeri; Goldburt, E. S.

doi:10.1038/271043a0

Cited by 55 publications

(34 citation statements)

References 3 publications

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“…[64,65] The MCH isomer in its ground state is polar,w hich is also expressedi nahigh dipole moment m g .T he first excited state dipole moment m e then is usually smaller (m g > m e ). Furthermore, since no MCH band splitting occurs, it can be excluded that MCH undergoes stacking into J-or H-aggregates upon polyelectro- Aggregation of the open-ring isomer has been observed in aliphatic hydrocarbons followed by crystallization [67,68] and in Langmuir-Blodgettf ilms. Thus, the more polar ground state of MCH becomes destabilized, while the excited state is relativelyu naffected.…”

Section: Size Characterization Of Spiropyran-polyelectrolytea Ssembliesmentioning

confidence: 99%

Water‐Soluble Spiropyrans with Inverse Photochromism and Their Photoresponsive Electrostatic Self‐Assembly

Moldenhauer

Gröhn

2017

Chemistry A European J

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A new type of light responsive nanoscale assemblies based on water-soluble spiropyrans is presented. We have synthesized four anionic spiropyrans bearing multiple sulfonate groups and investigated their photochromic behavior in aqueous solution. Depending on the pH, either inverse photochromism (acidic conditions) or normal photochromism (alkaline conditions) is found. Kinetic data for the interconversion of the spiropyran and merocyanine isomers including the subsequent slow hydrolysis have been obtained by UV/Vis spectroscopy. The results show that the spiropyrans undergo hydrolysis in both alkaline and acidic solution, while in the latter the rate is far slower than in the former. This prolonged hydrolytic stability together with the inverse photochromism under acidic conditions makes the sulfonated spiropyrans suitable to build photoresponsive nanostructures with cationic polyelectrolytes. We show how the self-assembly process is driven by electrostatic interactions and how the spiropyrans' photochromic property allows the size control of the supramolecular objects by visible light. The assembly size is characterized by dynamic light scattering and TEM. In addition, UV/Vis and fluorescence spectroscopy and ζ-potential measurements help to explain the size change upon visible light irradiation.

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Section: Size Characterization Of Spiropyran-polyelectrolytea Ssembliesmentioning

confidence: 99%

Water‐Soluble Spiropyrans with Inverse Photochromism and Their Photoresponsive Electrostatic Self‐Assembly

Moldenhauer

Gröhn

2017

Chemistry A European J

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“…In the 1970's, Krongauz et al reported the formation of MC aggregates (referred to as ''quasicrystals'') upon UV irradiation of SP molecules in aliphatic hydrocarbons. [11] They also concluded that the crystalline cores were composed of J-aggregate-like stacks of the MC form based on spectral studies. Sato et al reported recently the observation of micrometer-sized long-lived crystals generated by prolonged UV irradiation of the solutions of SP molecules.…”

Section: Introductionmentioning

confidence: 99%

Light‐Triggered Self‐Assembly of a Spiropyran‐Functionalized Dendron into Nano‐/Micrometer‐Sized Particles and Photoresponsive Organogel with Switchable Fluorescence

Chen

Zhang

et al. 2009

Adv Funct Materials

123

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The synthesis, self‐assembly, and spectroscopic investigations of spiropyran (SP)‐functionalized dendron 1 are reported. Under UV light irradiation, assembly of 1 into nano‐/microparticles occurs due to the transformation of the closed form of SP into the open merocyanine (MC) form. The formation of these nano‐/microparticles is confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) experiments in addition to the confocal laser scanning microscopy (CLSM) measurements. These nano‐/microparticles exhibit relatively strong red emission. It is interesting to note that the direct cooling of the toluene/benzene solution of 1 to 0 °C leads to gel formation. Multivalent π–π interactions due to the dendron in 1 may be the driving‐force for the gelation. The UV light irradiation cannot destroy the gel phase, and in fact, the gel–gel transition is successfully realized. The purple‐blue gel exhibits relatively strong red fluorescence; moreover, the fluorescence can be reversibly switched by alternating UV and visible light irradiation. The results clearly indicate that the MC form after aggregation becomes more stable and fluorescent.

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“…15, 16 Among various kinds of spiropyrans, 6-nitro-BIPS has been intensively studied; [16][17][18][19][20][21][22] its reaction scheme is depicted in Figure 1. The zwitterionic merocyanine form, which is created upon ultraviolet excitation, thermally isomerizes to the nonionic spiro form.…”

Section: Introductionmentioning

confidence: 99%

Study on the Chemical Reaction of Spiropyran in Medium- and High-Density Fluids

1996

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We have studied the thermal conversion of 1,3′,3′-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-indoline] (6-nitro-BIPS) in trifluoromethane (CHF 3 ) and nitrous oxide (N 2 O) from near-critical to liquid-like density regions. The rate constant decreases with increasing solvent density, which can be simply inferred from the density dependence of the dielectric constants of fluids. The activation energy, however, tends to decrease with increasing solvent density in the measured region in contrast to the dependence on the dielectric constant in liquid solutions. Desolvation due to the charge recombination and the conformational change may be the key to interpret this experimental result. We have also observed the aggregate formation and the deaggregation process of 6-nitro-BIPS in N 2 O.

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Quasi-crystals from irradiated photochromic dyes in an applied electric field

Cited by 55 publications

References 3 publications

Water‐Soluble Spiropyrans with Inverse Photochromism and Their Photoresponsive Electrostatic Self‐Assembly

Water‐Soluble Spiropyrans with Inverse Photochromism and Their Photoresponsive Electrostatic Self‐Assembly

Light‐Triggered Self‐Assembly of a Spiropyran‐Functionalized Dendron into Nano‐/Micrometer‐Sized Particles and Photoresponsive Organogel with Switchable Fluorescence

Study on the Chemical Reaction of Spiropyran in Medium- and High-Density Fluids

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