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

• underwent E–Z photoisomerization in benzene upon irradiation with yellow light and returned to E-isomer in darkness at room temperature within about 30 seconds [39]. One year later, Pummerer and Marondel attempted to reproduce this experiment and to detect the Z-isomer of N,N'-dimethylindigo 11a upon

• (9a) [57]. The bridged compounds 14 and 15 showed E–Z photoisomerization upon irradiation by 550 nm light at room temperature and then underwent thermal Z–E relaxation in xylene at 81.8 °C. The azelaoyl substituent in the intermolecularly bridged N,N'-diacylindigo 15 did not have significant influence

• photolysis in combination with steady-state measurements [59]. It was found that the E–Z photoisomerization of 9a, 9d, 9g, 9h occurred through a singlet mechanism upon direct excitation. However, the triplet state could be achieved by a sensitized reaction. At room temperature, a transient species that could

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

Formation of an exceptionally stable ketene during phototransformations of bicyclo[2.2.2]oct-5-en-2-ones having mixed chromophores

• Asitanga Ghosh

Beilstein J. Org. Chem. 2020, 16, 2297–2303, doi:10.3762/bjoc.16.190

• primarily engaged in synthesizing various types of such multichromophoric systems to compare their photochemistry in detail [9][10][11][12][13][14][15]. Since in acyclic enones like C, E/Z-photoisomerization becomes one of the major energy dissipation pathways, we selected rigid bicyclic multichromophoric

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

• could be reached after only 20 and 7 s of irradiation, respectively, which was significantly faster than the E→Z photoisomerization. All in all, the irradiation experiments revealed that the methoxy-substituted derivative 3b shows reversible photoisomerization, while cyano-substituted tris(arylazo

• 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

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

• state (PSS) for the E→Z photoisomerization at 365 nm was 88:12 in favor of the cis-form (Figure 4). The reversibility of the photoswitching of the supramolecular host was tested over several isomerization cycles with little evidence of fatigue (Figure 5). Thermal isomerization Z→E resulted in the

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

• in Supporting Information File 1). Compared to 4pzMe, photoswitches 4pzMe-Cl2 and 4pzMe-OMe2 show smaller π–π* band separations, which supports the reduced E–Z photoisomerization efficiency (80 and 81%, respectively) upon E–Z switching (Table 3). In contrast, 4pzMe-F2 and 4pzH-F2 still provide

• excellent E–Z photoisomerization of 93% and 92%, respectively, despite the relatively small π–π* band separation (30 and 33 nm, respectively). Conversely, the experimental n–π* band separation is very small (near complete band overlap) for the 4pzMe-X family (Figure 8), in contrast to the theoretical

• –Z photoisomerization is achieved by irradiating in the region of the high-energy π–π* band for the E-isomer, whereas Z–E photoisomerization occurs through irradiation in the low-energy n–π* band of the Z-isomer. However, an overlap in the absorbances between E/Z isomers causes incomplete

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

• even upon excitation at 350 nm, because of the induced E/Z photoisomerization process occurring within the experiment. Finally, the kinetics of the fluorescence decay of the Z-isomer has also been determined in acetonitrile, upon excitation at 400 nm, resulting in a lifetime of 479 ps (Figure S2

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• unclear. Photochemistry of azastilbenes The photochemical behaviour of stilbenes has been subject to intense investigation in the past. It is reported that unsubstituted stilbene undergoes E→Z photoisomerization [47], as well as photocyclization to dihydrophenanthrene upon UV irradiation, which is

• were able to isolate a preparative amount of 8a and tested it for its biological activity against Sirt1, Sirt2 and Sirt3. Surprisingly, 8a showed complete inactivity towards all sirtuins tested (Table 1). Hence it can be assumed that E→Z photoisomerization in similar compounds lowers inhibitory

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• -crown-5 ether; benzothiazolium crown ether-containing styryl dyes; E/Z photoisomerization; molecular solar thermal system; Introduction Molecular photoswitches permanently attract considerable interest because they hold potential for application in molecular electronic and photonic devices [1][2][3][4

• reactions. Real-time E/Z-photoisomerization of dyes 4a–d and their complexes The photoisomerization of free dyes 4a–d and dye–Ba2+ inclusion complexes were investigated in real time mode upon irradiation with visible light (λ = 488 nm) close to their absorption maxima. Figure 3a illustrates the

• constants of metal complexes were determined and are in good agreement with the literature data for reference dyes. The temporal evolution of trans-to-cis isomerization was observed in a real-time regime. The dyes demonstrated a low intrinsic fluorescence of their Ba2+ complexes and high yield of E/Z

Cycloheximide congeners produced by Streptomyces sp. SC0581 and photoinduced interconversion between (E)- and (Z)-2,3-dehydroanhydrocycloheximides

• Li Yang,
• Ping Wu,
• Jinghua Xue,
• Huitong Tan,
• Zheng Zhang and
• Xiaoyi Wei

Beilstein J. Org. Chem. 2017, 13, 1039–1049, doi:10.3762/bjoc.13.103

• important to the activities of cycloheximide congeners. Keywords: antifungal activity; cycloheximide derivatives; E/Z photoisomerization; Streptomyces sp; theoretical conformational analysis; Introduction The glutarimide-containing antibiotics represent a fascinating class of natural products that exhibit

• chromophore, were found to undergo E/Z photoisomerization under the indoor light. Theoretical investigation showed the presence of the C2–C3 double bond in 2 and 3 strengthens the C6–Cα double bond and increases the rotational barrier of the C6–Cα bond in the S1 (n–π*) states due to the extended electron

Photoswitchable precision glycooligomers and their lectin binding

• Daniela Ponader,
• Sinaida Igde,
• Marko Wehle,
• Katharina Märker,
• Mark Santer,
• David Bléger and
• Laura Hartmann

Beilstein J. Org. Chem. 2014, 10, 1603–1612, doi:10.3762/bjoc.10.166

• light-induced change in the geometry of the glycooligomers. Binding studies of the galactose-functionalized glycooligomers showed specific binding to PA-IL and a controlled reduction in binding affinity upon E → Z photoisomerization. We proposed a first model to explain our findings based on molecular

• solid support followed by on-resin functionalization of alkyne side chains with sugar azide ligands and final cleavage from the support. Characterization of the E → Z photoisomerization (λ = 360 nm) of Azo-Gal(1,3,5)-5 in buffer solution at 25 °C via UV–vis absorption spectroscopy measurements

Design and synthesis of a photoswitchable guanidine catalyst

• Philipp Viehmann and
• Stefan Hecht

Beilstein J. Org. Chem. 2012, 8, 1825–1830, doi:10.3762/bjoc.8.209

• properties can still be improved, in particular to obtain a pss with higher (Z)-content in the E→Z photoisomerization. Besides the photo-induced Z→E isomerization, the thermal back-reaction of guanidine 2Z was examined as well (Figure 2c). Based on the measured UV–vis and UPLC data and assuming a first-order