Photoisomerization of Mono‐Arylated Indigo and Water‐Induced Acceleration of Thermal cis ‐to‐ trans Isomerization

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Light is a nearly ideal stimulus for molecular systems. It delivers information encoded in the form of wavelengths and their intensities with high precision in space and time. Light is a mild trigger that does not permanently contaminate targeted samples. Its energy can be reversibly transformed into molecular motion, polarity, or flexibility changes. This leads to sophisticated functions at the supramolecular and macroscopic levels, from light‐triggered nanomaterials to photocontrol over biological systems. New methods and molecular adapters of light are reported almost daily. Recently reported applications of photoresponsive systems, particularly azobenzenes, spiropyrans, diarylethenes, and indigoids, for smart materials and photocontrol of biological setups are described herein with the aim to demonstrate that the 21st century has become the Age of Enlightenment—“Le siècle des Lumières”—in molecular sciences.

Section: Molecular Photoswitchesmentioning

confidence: 99%

Recent Implementations of Molecular Photoswitches into Smart Materials and Biological Systems

Pianowski

2019

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“…Notably, distinctly separated elution peaks occurred in RP‐HPLC for all the diarylindigos under dilute acidic conditions giving different UV/Vis‐spectra, but identical mass spectra. This observation indicates the presence of cis / trans isomers (Figures S13–S15) [9] . In general, N ‐unsubstituted indigos do not photoisomerize because of dominating and fast deactivation mechanisms [55] .…”

Section: Methodsmentioning

confidence: 91%

“…Thanks to tremendous efforts by several research groups traditional indigoids recently turned into focus as natural product‐based, non‐toxic materials for sustainable organic electronics [4–6] . Topical studies examining the photoswitching abilities of N , N ’‐aryl‐substituted indigos pointed to a useful strategy to tailor their photochemical properties [7–9] . Synthetic routes towards 1 were developed by Baeyer and by Heumann and paved the way to multi‐ton production, yet its dibrominated counterpart 2 has never entered an industrial scale production [10] …”

Section: Methodsmentioning

confidence: 99%

“…presenceo fcis/trans isomers( Figures S13-S15). [9] In general, Nunsubstituted indigos do not photoisomerize because of dominating and fast deactivation mechanisms. [55] On the other hand, under acidic conditions and in the gas phaseatrans/cisprotoisomerization hasb een detectedf or indigo and its bisimine derivatives.…”

Section: #P Roductmentioning

confidence: 99%

“…[4][5][6] To pical studies examiningt he photoswitching abilitieso fN,N'-aryl-substituted indigos pointedt oau seful strategyt ot ailor their photochemical properties. [7][8][9] Synthetic routes towards 1 were developed by Baeyer and by Heumann and paved the way to multi-ton production, yet its dibrominated counterpart 2 has never entereda ni ndustrial scale production. [10] To day biocatalysis offers av ersatile methodology to address selectivity issues, e.g.,a rising from similarly reactive CÀHm oieties.…”

mentioning

confidence: 99%

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Novel Arylindigoids by Late‐Stage Derivatization of Biocatalytically Synthesized Dibromoindigo

Schnepel

Dodero

Sewald

2021

Indigoids represent natural product-based compounds applicable as organic semiconductors and photoresponsive materials. Yetm odified indigo derivatives are difficult to access by chemicals ynthesis. Ab iocatalytic approach applying several consecutive selective CÀHf unctionalizations was developed that selectively provides access to variousi ndigoids:E nzymatic halogenation of ltryptophan followed by indole generation with tryptophanase yields 5-, 6-and 7-bromoindoles. Subsequent hydroxylation using af lavin monooxygenasef urnishes dibromoindigo that is derivatized by acylation.T his four-step one-pot cascade gives dibromoindigo in good isolated yields. Moreover,t he halogens ubstituent allows for late-stage diversification by cross-coupling directly performed in the crude mixture, thus enabling synthesis of a small set of 6,6'-diarylindigo derivatives. This chemoenzymatic approachp rovides am odular platform towards novel indigoids with attractive spectral properties.

Mechanistic Insights into the Photoisomerization of N,N′‐Disubstituted Indigos

Budzák

Jovaišaitė

Huang

et al. 2022

N,N′‐disubstituted indigos are photoswitchable molecules that have recently caught the attention due to their addressability by red‐light. When alkyl and aryl groups are utilized as the N‐substituents, the thermal half‐lives of Z isomers can be tuned independently while maintaining the advantageous red‐shifted absorption spectra. To utilize these molecules in real‐world applications, it is of immense importance to understand how their molecular structures as well as the environment influence their switching properties. To this end, we probed their photoisomerization mechanism by carrying out photophysical and computational studies in solvents of different polarities. The fluorescence and transient absorption experiments suggest for more polar excited and transition states, which explains the bathochromic shifts of absorption spectra and shorter thermal half‐lives. On the other hand, the quantum chemical calculations reveal that in contrast to N‐carbonyl groups, N‐alkyl and N‐aryl substituents are not strongly conjugated with the indigo chromophore and can thus serve as a tool for tuning the thermal stability of Z isomers. Both approaches are combined to provide in‐depth understandings of how indigos undergo photoswitching as well as how they are influenced by N‐substituent and the chemical surroundings. These mechanistic insights will serve as guiding principles for designing molecules eyeing broader applications.