Negative photochromism in organic systems

Barachevsky, V. А.

doi:10.1134/s2079978017030013

“…Donor–acceptor Stenhouse adducts (DASAs, Figure a) were introduced in 2014 and feature important advantages as compared to traditional photoswitches, including visible light responsiveness and negative photochromism . Moreover, their modular architecture allows for a fine‐tuning of properties .…”

Section: Figurementioning

confidence: 73%

Solvent Effects on the Actinic Step of Donor–Acceptor Stenhouse Adduct Photoswitching

Lerch

¹

,

Donato

²

,

Laurent

³

et al. 2018

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Donor–acceptor Stenhouse adducts (DASAs) are negative photochromes that switch with visible light and are highly promising for applications ranging from smart materials to biological systems. However, the strong solvent dependence of the photoswitching kinetics limits their application. The nature of the photoswitching mechanism in different solvents is key for addressing the solvatochromism of DASAs, but as yet has remained elusive. Here, we employ spectroscopic analyses and TD‐DFT calculations to reveal changing solvatochromic shifts and energies of the species involved in DASA photoswitching. Time‐resolved visible pump‐probe spectroscopy suggests that the primary photochemical step remains the same, irrespective of the polarity and protic nature of the solvent. Disentangling the different factors determining the solvent‐dependence of DASA photoswitching, presented here, is crucial for the rational development of applications in a wide range of different media.

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“…Such spatial changes enabled for example the development of an isomer specific cryptand for metal cations by the reversible folding and unfolding of acrownether. [23] The trans!cis isomerization of typical thioindigos is conveniently triggered by green or yellow light,w hereas the reverse process can be initiated by blue light (negative photochromism [24] ). Quantumy ields for both processes (f tc and f ct )r each values close to 50 %i nf avorably substituted derivatives such as 1b, [13] whereas higherv alues are usually precluded by stochastic aspects of the isomerization mechanisms.…”

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confidence: 99%

Reversible Spatial Control in Aqueous Media by Visible Light: A Thioindigo Photoswitch that is Soluble and Operates Efficiently in Water

Koeppe

¹

,

Römpp

²

2018

Chemistry A European J

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Aiming to extend the scope of indigoid photoswitches to polar protic environments, we have synthesized a sulfonated thioindigo derivative highly soluble in water. Studies by UV/Vis absorption, fluorescence, and NMR spectroscopy indicate that, despite aggregation effects at micromolar concentrations, the novel dye offers satisfactory performance in aqueous solution in the absence of solvation aides. Enrichment of the metastable cis isomer by irradiation may exceed 65 % and its half-life at room temperature may exceed several hours. Degradation after 20 yellow and blue light irradiation cycles within 2 hours is less than 2 %. Performance can be expected to further improve in future molecular designs if the tendency towards self-association is further reduced. Crucially, photoisomerization of indigoids is not necessarily inhibited by water and, thus, the superior spatial control offered by this class of molecular switches may be of great benefit also in biological systems.

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“…[7][8][9][10][11][12] Applications differ markedly in the environment the photoswitch is exposed to,b ei td ifferent solvents, [13,14] matrices or surfaces,a nd understanding how ag iven photoswitch behaves in various environments is crucial for its success in any applications.Donor-acceptor Stenhouse adducts (DASAs,F igure 1a) were introduced in 2014 [17,18] and feature important advantages as compared to traditional photoswitches,i ncluding visible light responsiveness [11,19,20] and negative photochromism. [21] Moreover,t heir modular architecture [22] allows for afine-tuning of properties. [23] First-generation DASAs (1 and 2,F igure 1a) [17,18] are based on dialkylamine donors,whereas second-generation DASAs (3) [24,25] employ secondary anilines leading to bathochromically shifted spectra.…”

mentioning

confidence: 99%

“…Donor-acceptor Stenhouse adducts (DASAs,F igure 1a) were introduced in 2014 [17,18] and feature important advantages as compared to traditional photoswitches,i ncluding visible light responsiveness [11,19,20] and negative photochromism. [21] Moreover,t heir modular architecture [22] allows for afine-tuning of properties. [23] First-generation DASAs (1 and 2,F igure 1a) [17,18] are based on dialkylamine donors,whereas second-generation DASAs (3) [24,25] employ secondary anilines leading to bathochromically shifted spectra.…”

mentioning

confidence: 99%

Solvent Effects on the Actinic Step of Donor–Acceptor Stenhouse Adduct Photoswitching

Lerch

¹

,

Donato

²

,

Laurent

³

et al. 2018

View full text Add to dashboard Cite

Donor–acceptor Stenhouse adducts (DASAs) are negative photochromes that switch with visible light and are highly promising for applications ranging from smart materials to biological systems. However, the strong solvent dependence of the photoswitching kinetics limits their application. The nature of the photoswitching mechanism in different solvents is key for addressing the solvatochromism of DASAs, but as yet has remained elusive. Here, we employ spectroscopic analyses and TD‐DFT calculations to reveal changing solvatochromic shifts and energies of the species involved in DASA photoswitching. Time‐resolved visible pump‐probe spectroscopy suggests that the primary photochemical step remains the same, irrespective of the polarity and protic nature of the solvent. Disentangling the different factors determining the solvent‐dependence of DASA photoswitching, presented here, is crucial for the rational development of applications in a wide range of different media.

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Negative photochromism in organic systems

Cited by 61 publications

References 91 publications

Solvent Effects on the Actinic Step of Donor–Acceptor Stenhouse Adduct Photoswitching

Solvent Effects on the Actinic Step of Donor–Acceptor Stenhouse Adduct Photoswitching

Reversible Spatial Control in Aqueous Media by Visible Light: A Thioindigo Photoswitch that is Soluble and Operates Efficiently in Water

Solvent Effects on the Actinic Step of Donor–Acceptor Stenhouse Adduct Photoswitching

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