Effect of substitution position of aryl groups on the thermal back reactivity of aza-diarylethene photoswitches and prediction by density functional theory

• Misato Suganuma,
• Daichi Kitagawa,
• Shota Hamatani and
• Seiya Kobatake

Beilstein J. Org. Chem. 2025, 21, 242–252, doi:10.3762/bjoc.21.16

• -withdrawing substituents on the N-aryl moieties enhanced the thermal stability of the Z-isomers while maintaining the advantageous photoswitching properties upon irradiation with red light [52]. The effect of substituents on the thermal cis–trans isomerization of azobenzenes has also been widely studied, and

Understanding X-ray-induced isomerisation in photoswitchable surfactant assemblies

• Beatrice E. Jones,
• Camille Blayo,
• Jake L. Greenfield,
• Matthew J. Fuchter,
• Nathan Cowieson and
• Rachel C. Evans

Beilstein J. Org. Chem. 2024, 20, 2005–2015, doi:10.3762/bjoc.20.176

• ]. However, the potential scope for Azo in practice is limited by its incomplete photoswitching to the metastable isomer in the PSS and its rapid thermal reversion to the E isomer [12][13]. To tackle this, arylazopyrazoles (AAPs) have emerged as promising alternatives, where one of the phenyl rings of Azo is

• replaced by a pyrazole, which improves several aspects of their performance, including quantitative photoswitching between isomers and significantly enhanced thermal stability of the Z isomer [13][14][15]. This has led to recent reports on the integration of AAPs into surfactants to form systems with

Supramolecular assemblies of amphiphilic donor–acceptor Stenhouse adducts as macroscopic soft scaffolds

• Ka-Lung Hung,
• Leong-Hung Cheung,
• Yikun Ren,
• Ming-Hin Chau,
• Yan-Yi Lam,
• Takashi Kajitani and
• Franco King-Chi Leung

Beilstein J. Org. Chem. 2024, 20, 1590–1603, doi:10.3762/bjoc.20.142

• cycle (Figure S1a and S1b, Supporting Information File 1). In contrast, the previously studied reversibility of the photoswitching of DA10 had revealed 10% absorbance decreases per cycle [37], indicating a mild improvement to the fatigue resistance of DA11. To further investigate the photostability and

• feasible photoreversibility of DA7 and DA6 for five additional photoswitching cycles. However, a more significant fatigue effect was observed in DA7 (Figure S1c and S1d, Supporting Information File 1) and DA6 (Figure S1e and S1f, Supporting Information File 1), with 15% absorbance decline per cycle. As a

Photoswitchable glycoligands targeting Pseudomonas aeruginosa LecA

• Yu Fan,
• Ahmed El Rhaz,
• Stéphane Maisonneuve,
• Emilie Gillon,
• Maha Fatthalla,
• Franck Le Bideau,
• Guillaume Laurent,
• Samir Messaoudi,
• Anne Imberty and
• Juan Xie

Beilstein J. Org. Chem. 2024, 20, 1486–1496, doi:10.3762/bjoc.20.132

• ] or to mannosyl azobenzene-modified human cells [21] through photoswitching the orientation of the attached mannoside [22]. Photoswitchable glycooligomers [23] or glycodendrimers [24] have been investigated for the inhibition of PA lectin PA-IL or LecA and LecB. A variation of the IC50 value by a

• respectively 71%, 41%, and 37% total yields (Scheme 1). Photophysical characterization The photoswitching properties of galactosyl azobenzenes 1–5 were realized in water or in Tris buffer containing 5 to 10% DMSO, in accordance with the biophysical evaluation conditions by using ITC. All these compounds

• ). The S-galactosyl azobenzenes 3–5 also displayed excellent photoswitching properties, with a red shift for the π→π* transition (λmax = 348–364 nm) compared to the O-galactosyl derivatives (Table 1, entries 5–8). However, the absorption coefficient and the thermostability of the Z-isomers are increased

Novel route to enhance the thermo-optical performance of bicyclic diene photoswitches for solar thermal batteries

• Akanksha Ashok Sangolkar,
• Rama Krishna Kadiyam and
• Ravinder Pawar

Beilstein J. Org. Chem. 2024, 20, 1053–1068, doi:10.3762/bjoc.20.93

• by employing chemical photoswitches in molecular solar thermal (MOST) energy storage systems is a topic of appealing research interest. However, incorporating all the features desired for an ideal MOST system in a single photoswitching couple is challenging. Inspired by experimental synthesis, herein

• the most versatile solvent to exhibit the best photoswitching behaviour which is beneficial for real-life energy storage applications. Additionally, the stability and reversibility of the photoswitching system with elongated unsaturated bridges have also been assessed. By means of the studied

• the photoswitching cycle [8][9][10][11][12][13]. This enables the harvesting, conversion, and storage of solar energy into thermal energy via a reversible and closed photoswitching cycle. The photoswitching couple must exhibit distinct features to be applicable for solar energy harvesting and storage

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• allosterically regulated host–guest systems to catalysis or magnetic properties. Redox switchable molecular tweezers One of the cleanest stimuli for supramolecular switching is electron transfer. Besides photoswitching, the undeniable advantages of redox switching are the absence of chemical waste and the fact

Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• of prospective applications of indigo photoswitches. Keywords: indigoid dyes; photochemistry; photophysics; photoswitching; E–Z isomerization; Review Historical milestones in the development of photochromic indigo derivatives 1954: first reported photochromic indigo derivative – N,N'-diacetylindigo

• in the presence of water in organic solvent. In 2023, Huang, Hecht, Priimagi and co-workers provided the first study of the photoswitching of Ν,Ν'-derivatized indigos in polymer films of different rigidity and described the molecular design strategy allowing to improve the photoswitching performance

• within the polymer matrix [67]. Based on the obtained results, the authors are aiming to translate the photoswitching effect to the macroscopic level and to achieve the modulation of macroscopic properties of materials by red light. Conclusion From the first report on the photochromic N,N'-diacetylindigo

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

• Jannis Ludwig,
• Julian Helberg,
• Hendrik Zipse and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2119–2126, doi:10.3762/bjoc.16.179

• . reported on the photoswitching of the basicity of a piperidine nitrogen by reversible steric shielding of the nitrogen lone pair. The photoswitchable base was applied as a nucleophilic catalyst in the nitroaldol (Henry) reaction. Attached to a sterically demanding azobenzene unit, the lone pair was

Potent hemithioindigo-based antimitotics photocontrol the microtubule cytoskeleton in cellulo

• Alexander Sailer,
• Franziska Ermer,
• Yvonne Kraus,
• Rebekkah Bingham,
• Ferdinand H. Lutter,
• Julia Ahlfeld and
• Oliver Thorn-Seshold

Beilstein J. Org. Chem. 2020, 16, 125–134, doi:10.3762/bjoc.16.14

• hemithioindigo-based indanone-like tubulin inhibitors (HITubs) and optimised their cellular potency as antimitotic photopharmaceuticals. These HITubs feature reliable and robust visible-light photoswitching and high fatigue resistance. The use of the hemithioindigo scaffold also permitted us to employ a para

• , all-visible-light photoswitching. Results and Discussion Design strategy for HTIs The HTI-based colchicinoid HOTubs (e.g., HOTub-31) that we previously explored had the HTI photoswitch embedded inside a methoxylation pattern, such that one isomer obeyed the structure–activity relationship (SAR) of

• photopharmaceutical scaffold than the widely used azobenzene motif. While para-hydroxyazobenzenes feature negligibly short cis-to-trans thermal relaxation half- lives in aqueous media in the range of μs [24][25], probably making them unsuitable for robust photoswitching applications against intracellular targets

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

• Sarah Kölsch,
• Heiko Ihmels,
• Jochen Mattay,
• Norbert Sewald and
• Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

• coupling of its transition dipole moment with the ones of the DNA bases. Overall, these data revealed a loose binding of the cyclobutane derivative 4b to DNA through outside-edge binding of the ligand that enabled the association of one or two aromatic units in the DNA grooves. Photoswitching of the DNA

Light-controllable dithienylethene-modified cyclic peptides: photoswitching the in vivo toxicity in zebrafish embryos

• Sergii Afonin,
• Oleg Babii,
• Aline Reuter,
• Volker Middel,
• Masanari Takamiya,
• Uwe Strähle,
• Igor V. Komarov and
• Anne S. Ulrich

Beilstein J. Org. Chem. 2020, 16, 39–49, doi:10.3762/bjoc.16.6

• embryotoxicity of dithienylethene-modified peptides upon photoswitching, using 19 analogues based on the β-hairpin scaffold of the natural membranolytic peptide gramicidin S. We established an in vivo assay in two variations (with ex vivo and in situ photoisomerization), using larvae of the model organism Danio

• , (iii) demonstrate photoswitching of the whole-body toxicity for the dithienylethene-modified peptides in vivo, (iv) re-analyze previous structure–toxicity relationship data, and (v) select promising candidates for potential clinical development. Keywords: diarylethene photoswitch; gramicidin S

• dilution steps. In the photoconversion experiments, in order to prevent spontaneous photoswitching of the ring-closed peptides by vis light, zebrafish embryos and peptides were kept in the dark before the first readout, and the vials were sealed to avoid evaporation of the embryonic medium (E3) at

Starazo triple switches – synthesis of unsymmetrical 1,3,5-tris(arylazo)benzenes

• Andreas H. Heindl and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2020, 16, 22–31, doi:10.3762/bjoc.16.4

• variety of unsymmetrical starazo species, starting from suitable dibromoazobenzenes. A preliminary investigation of the presented three-state switches by UV–vis and 1H NMR spectroscopy revealed that both derivatives 3a and 3b were capable of E→Z photoisomerization. However, no selective photoswitching

Synthesis and characterization of bis(4-amino-2-bromo-6-methoxy)azobenzene derivatives

• David Martínez-López,
• Amirhossein Babalhavaeji,
• Diego Sampedro and
• G. Andrew Woolley

Beilstein J. Org. Chem. 2019, 15, 3000–3008, doi:10.3762/bjoc.15.296

• in particular can form azonium ions under physiological conditions and exhibit red-light photoswitching. Here, we report the synthesis and characterization of two bis(4-amino-2-bromo-6-methoxy)azobenzene derivatives. These compounds form red-light-absorbing azonium ions, but only under very acidic

• azobenzenes – have recently been found to exhibit photoswitching properties suitable for in vivo use [8][9][10]. Typically, the formation of azonium ions from aminoazobenzenes occurs at pH < 3.5 [11][12], however, the pKa of the trans-azonium ion 1 is ca. 7.5 in aqueous solution (Figure 1) [9][10]. The

• isomerization with 720 nm light under physiological conditions [8]. While the photoswitching properties of 3 are suitable for the use in biological systems, the overall size of 3 may limit the possibilities for the use as a component of photopharmaceutical agents. Currently, most photopharmaceutical agents are

Design, synthesis and investigation of water-soluble hemi-indigo photoswitches for bioapplications

• Daria V. Berdnikova

Beilstein J. Org. Chem. 2019, 15, 2822–2829, doi:10.3762/bjoc.15.275

• Daria V. Berdnikova Department Chemie–Biologie, Organische Chemie II, Universität Siegen, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany 10.3762/bjoc.15.275 Abstract A series of hemi-indigo derivatives was synthesized and their photoswitching properties in aqueous medium were studied. The

• that allowed to obtain an RNA-binding hemi-indigo derivative with photoswitchable fluorescent properties. Keywords: hemi-indigo; molecular switches; photochromism; photoswitching; visible light; water solubility; Introduction The application of organic photochromes in biological systems is fraught

• with their poor solubility and reduced photoswitching efficiency in aqueous medium. In many cases, approaches to improve the water solubility by chemical modification of the photochromic scaffolds are not straightforward because the introduction of substituents often interferes with the desired

Chemical tuning of photoswitchable azobenzenes: a photopharmacological case study using nicotinic transmission

• Lorenzo Sansalone,
• Jun Zhao,
• Matthew T. Richers and
• Graham C. R. Ellis-Davies

Beilstein J. Org. Chem. 2019, 15, 2812–2821, doi:10.3762/bjoc.15.274

• the cis-4FAB configuration (thermal half-life > 12 days at 37 °C in physiological buffer) and cis–trans photostationary states above 84%. Furthermore, the well-separated n–π* absorption bands of trans- and cis-4FAB allow facile photoswitching with visible light in two optical channels. A convergent 11

• photoswitching of 2 (Figure 5c, colored traces). The time between these sweeps was 3 min. Since we used full field illumination through the epi-fluorescence port of the microscope for our experiments, the light not only illuminates an area around the cell, but much of the volume of the puffer pipette reservoir

• neurotransmitters. We have synthesized a photoswitchable tetrafluoroazobenzene (4FAB) agonist of nicotinic acetylcholine receptors that is biologically inert at sub-millimolar levels in the cis AB configuration. Photoswitching of the chromophore on neurons with violet light rapidly activates inward currents. We

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• calcium upon acting on the conformation of the adjacent binding site, rendering it a stronger or weaker binder. Photoswitching was studied in pseudo-physiological conditions (pH 7.2, [KCl] = 100 mM) and dissociation constants for azobenzene cis- and trans-isomers have been determined (0.230 μM and 0.102

• EDTA) such that photoswitching would enhance or lower Ca2+ binding based on the state of the adjacent photoswitch. Photogeneration of a positive charge proximal to the BAPTA site is undoubtedly the most robust approach to provoke calcium cation release, while diminishing electron density on the

• affinity. Herein we describe the synthesis of 1, its photoswitching, and affinity changes between both forms in pseudo-physiological conditions, further rationalized by energy-minimized molecular modelling structures. Results and Discussion The synthetic pathway for the preparation of molecule 1 is shown

A chiral self-sorting photoresponsive coordination cage based on overcrowded alkenes

• Constantin Stuckhardt,
• Diederik Roke,
• Wojciech Danowski,
• Edwin Otten,
• Sander J. Wezenberg and
• Ben L. Feringa

Beilstein J. Org. Chem. 2019, 15, 2767–2773, doi:10.3762/bjoc.15.268

• photoswitching affords a large geometric change of the ligands, only minor changes were observed in binding constants of the different cage structures. These results show that by incorporation of overcrowded alkenes into SCCs the geometry of cage structures can be controlled by light. Different designs might be

A combinatorial approach to improving the performance of azoarene photoswitches

• Joaquin Calbo,
• Aditya R. Thawani,
• Rosina S. L. Gibson,
• Andrew J. P. White and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2019, 15, 2753–2764, doi:10.3762/bjoc.15.266

• photopharmacology [1][2] and optochemical genetics [3] to data storage [4]. Numerous classes of photochromic molecules exist, each with their own unique characteristics. For example, spiropyrans [5][6] may exhibit significant changes in solubility upon photoswitching, whilst the photoswitching of diarylethenes [7

• thermal stability of the Z-isomer. Despite the huge body of structure–property relationship studies known for substituted azobenzenes [8][9], it is still common to observe azo photoswitches that undergo incomplete photoswitching and/or possess low Z-isomer thermal stability. Perhaps the most important

• advancement to tackle these limitations in recent times has been the discovery that tetra-ortho substitution of the azobenzene unit can lead to a significant improvement of the photoswitching properties (Figure 1a). Specifically, o-methoxy [10][11] and o-thio [12] analogues reported by Woolley and co-workers

A photochemical determination of luminescence efficiency of upconverting nanoparticles

• Baptiste Amouroux,
• Clément Roux,
• Jean-Claude Micheau,
• Fabienne Gauffre and
• Christophe Coudret

Beilstein J. Org. Chem. 2019, 15, 2671–2677, doi:10.3762/bjoc.15.260

• mimic such a situation, we have designed an experiment with larger nanoparticles (35 nm) and dilute 1-c dye: an absorbance at 540 nm of 0.11 ([1-c] = 1.14 × 105 mol L−1) corresponds to number of dyes of 6800 molecules per femtoliter. The photoswitching of the actinometer 1-c was clearly observed

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• full agonism. The compound class disclosed here can aid in new photopharmacology studies of CXCR3 signaling. Keywords: azo compounds; chemokine receptor; efficacy photoswitching; G protein-coupled receptors; photopharmacology; Introduction Photopharmacology is an emerging discipline at the interface

• ligands [10]. The ensuing photochromic GPCR ligands are usually orthosteric and the photoswitching generally affects the functional potency [4][11][23] and/or the binding affinity [3][4][5][11] of the ligand (Figure 1A). However, as mentioned, GPCRs that endogenously bind large molecules (large peptides

• substituent to the binding site of the receptor [24]. In order to obtain an efficacy photoswitching, we opted for replacing the biaryl moiety for an azobenzene in an azologization approach (Figure 1D) with the expectation that the isomerization of the azobenzene would provide changes in 3D shape that are

Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

• Alessandro Iagatti,
• Baihao Shao,
• Alberto Credi,
• Barbara Ventura,
• Ivan Aprahamian and
• Mariangela Di Donato

Beilstein J. Org. Chem. 2019, 15, 2438–2446, doi:10.3762/bjoc.15.236

• photoswitching mechanism, aimed at characterizing the timescale of the photoinduced structure variation and the solvent dependence of its fluorescence properties, is still lacking. Here we present a spectroscopic characterization of this hydrazone species, using both steady state and time resolved absorption and

• similarity of the successive evolution and of the transient spectra detected in the two cases indicates that a similar reactivity is induced upon one-photon and two-photon excitation, further confirming the two-photon photoswitching ability of hydrazone 1 already inferred by previous measurements [29]. Using

Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes

• Andrey G. Lvov,
• Max Mörtel,
• Anton V. Yadykov,
• Frank W. Heinemann,
• Valerii Z. Shirinian and
• Marat M. Khusniyarov

Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235

• at the iron(II) ion at room temperature (rt) in solution via ligand photocyclization [19]. More recently, the remarkable photoswitching between high-spin and low-spin states at rt in the solid state and thin films was demonstrated [20][21][22]. Kawai et al. obtained a luminescent complex of europium

Reversible switching of arylazopyrazole within a metal–organic cage

• Anton I. Hanopolskyi,
• Soumen De,
• Michał J. Białek,
• Yael Diskin-Posner,
• Liat Avram,
• Moran Feller and
• Rafal Klajn

Beilstein J. Org. Chem. 2019, 15, 2398–2407, doi:10.3762/bjoc.15.232

• )22 prior to UV irradiation and, as expected, did not observe any shifts of 1’s signals. To further confirm the photoswitching-induced guest expulsion, we performed detailed diffusion-ordered spectroscopy (DOSY) measurements. A representative DOSY spectrum of (E-1)22 is shown in Figure 7, left. The

Targeted photoswitchable imaging of intracellular glutathione by a photochromic glycosheet sensor

• Xianzhi Chai,
• Hai-Hao Han,
• Yi Zang,
• Jia Li,
• Xiao-Peng He,
• Junji Zhang and
• He Tian

Beilstein J. Org. Chem. 2019, 15, 2380–2389, doi:10.3762/bjoc.15.230

• integrate these functions into one molecule. By taking advantages of both redox-active/high loading features of two-dimensional (2D) manganese dioxide (MnO2) and dynamic fluorescence photoswitching of photochromic sensors, we here design a hybrid photochromic MnO2 glycosheet (Glyco-DTE@MnO2) to achieve the

• precise outputs can be obtained for targeted analytes even at low concentrations. Though promising, common “photochromophore–fluorophore”-type sensors require elaborate designs to integrate multifunctionality (e.g., photoswitching, fluorescence sensing, targetability, water solubility, etc.) into one

• control reporter 8o with a PEG chain instead of the galactoside targeting group was also prepared. The detailed synthetic procedures and characterizations are given in Supporting Information File 1. Photochromic performances of Glyco-DTE The photoswitching performances of Glyco-DTE (1 × 10−5 mol/L) were

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• open forms with rather low emission efficiency. The photoswitching kinetics was studied at several wavelengths with UV and visible light. New diarylethenes underwent ring-closure reactions by irradiation with UV light (365 nm, 405 nm), and the reversible ring-opening by irradiation with visible light

• large fluorescence quantum yield, compound SyOTh1 emerged as a candidate for single-molecule based super-resolution fluorescence microscopy. Keywords: diarylethenes; dyes; fluorescence; organic synthesis; photochromism; photoswitching; Introduction Reversibly photoswitchable diarylethenes (DAEs) with