Orthogonal photoswitching of heterobivalent azobenzene glycoclusters: the effect of glycoligand orientation in bacterial adhesion

• Leon M. Friedrich and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2025, 21, 736–748, doi:10.3762/bjoc.21.57

• well as of 3, 4, and 5 is illustrated by the respective switching cycles in Figure 2A and B. In a next step, thermal relaxation of the metastable ZZ and Z isomers, respectively, was studied. In 2, thermal relaxation of the ZZ isomer can occur via the EZ or the ZE isomer (Figure 2C), respectively [24

• ][39]. The kinetics of these processes are described by the rate constants k1, k2, k3, and k4, where k1 and k4 describe thermal relaxation of the AB unit and k2 and k3 of the ABF4 unit, respectively. For the thermal Z to E relaxation of the individual glycoazobenzene antennas 6αMan 3, 6βGlc 4, and

• published tailor-made fitting program [24], the rate constants k1–k4 were extracted from the kinetic traces and are summarized in Table 2. The thermal relaxation of the glycoazobenzene antennas 3, 4, and 5, on the other hand, was monitored by UV–vis spectroscopy at 37 °C and the rate constants k5, k6, and

Synthesis of N-acetyl diazocine derivatives via cross-coupling reaction

• Thomas Brandt,
• Pascal Lentes,
• Jeremy Rudtke,
• Michael Hösgen,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2025, 21, 490–499, doi:10.3762/bjoc.21.36

• -substituted diazocines were prepared via Stille, Suzuki, and Buchwald–Hartwig reactions. X-ray structures are presented for derivatives 1, 2 and 7. Keywords: cross-coupling; diazocine; N-acetyl diazocine; photoisomerization; photoswitch; thermal relaxation; Introduction Diazocines are frequently used

• all synthesized compounds. Thermal half-lives (t1/2) were determined by monitoring the thermal relaxation of the synthesized diazocines at 25 °C in a UV spectrometer (see Supporting Information File 1, section III). The dihalogenated N-acetyl diazocine 4 shows a significantly reduced half-life

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

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

• (λirr = 660 nm). The excited state dynamics of 18c was later studied in detail by Nagasawa and co-workers using femtosecond time-resolved transient absorption spectroscopy [44]. In 2022, Qiao and co-workers attempted to extend the thermal relaxation half-life of compound 18c by addition of cations such

• solvents and under high pressures were performed. It was found that N,N'-dibenzoylindigos underwent the thermal relaxation much more slowly than the compounds without the aromatic ring in the acyl group. The biradical mechanism (Figure 11) was found to be the preferable pathway for the thermal Z–E

• the Z-isomer with metal cations. Schematic representation of indigo-type (left) and amide-type (right) resonances in N,N'-acetylindigo (9a). Suggested intermediates for the double bond cleavage for the thermal relaxation of N,N'-diacylindigos: (A) a biradical transient species, (B) a dipolar transient

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

• , the thermal relaxation time for the cis→trans isomerization in THF was determined by 1H NMR spectroscopy. Similar to previous record player systems a long half-life of the metastable cis isomer of about 505 d (25 °C, THF-d8) was determined (Figure S5 in Supporting Information File 1). Thus, the

• thermal relaxation of the coordinated cis state is insignificant for our catalytic studies. Experiments using porphyrin 1 as a catalyst The Henry reaction (Scheme 2) was chosen as a model reaction to investigate the catalytic activity of porphyrin 1 in the two different switching states because the rate

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

• 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

• Information File 1). Photocharacterisation Although some para-hydroxy-substituted HTIs have been described [28][29], we are unaware of any report of the solvent- and pH-dependency of their photochromism and thermal relaxation. Dube and co-workers have reported that in general, increasing the electron-donating

• strength of groups in the hemistilbene para-position of HTIs correlates to (a) a bathochromic shift of the S0 → S1 absorption band (up to λmax ≈ 500 nm with julolidine substitution) and (b) decreased thermal stability of the metastable E-isomer, i.e., faster thermal relaxation [30]. However, they also

Photocontrolled DNA minor groove interactions of imidazole/pyrrole polyamides

• Sabrina Müller,
• Jannik Paulus,
• Jochen Mattay,
• Heiko Ihmels,
• Veronica I. Dodero and
• Norbert Sewald

Beilstein J. Org. Chem. 2020, 16, 60–70, doi:10.3762/bjoc.16.8

• the E- to the Z-form usually takes place at 350 nm irradiation (π–π* transition), the reverse is photochemically induced at 450 nm (n–π* transition) or thermally. The rate of thermal relaxation, inter alia, depends on the substituents, and only derivatives with very slow thermal relaxation are

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

• absorbance at 440 nm was diminished and that at 330 nm slightly enhanced (Figure 3). An estimated PSS of ca. 60% Z-isomer was calculated as described in the Experimental section. Thermal relaxation from the PSS was monitored by UV–vis spectroscopy, recording a spectrum every minute. As shown in Figure 3, a

• significantly lowered pKa value, made 5 unsuitable as an azonium photoswitch under physiological conditions. Despite this undesired effect on the pKa value, the steric bulk introduced by the bromine substituents did appear to slow thermal relaxation of the neutral (unprotonated) azo forms of these compounds

• thermal relaxation (τ1/2 ca. 10 min). Experimental General All commercial materials (solvents, reagents, and substrates) were used as received. SilicaFlash silica gel, P60, 40–63 µm particle size (SiliCycle) was used for column chromatography. High-performance liquid chromatography was performed on a

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

• properties of the tetrafluoroazobenzene (4FAB) scaffold. Ultraviolet light switching and rapid thermal relaxation of the metastable cis configuration are the main drawbacks associated with standard AB-based switches. We designed our photoprobes to take advantage of the excellent thermodynamic stability of

In search of visible-light photoresponsive peptide nucleic acids (PNAs) for reversible control of DNA hybridization

• Lei Zhang,
• Greta Linden and
• Olalla Vázquez

Beilstein J. Org. Chem. 2019, 15, 2500–2508, doi:10.3762/bjoc.15.243

• room temperature in the dark according to UV–vis measurements (Figure 2 and Figure S32, Supporting Information File 1). The thermal relaxation of the cis-PNA12(oF4Azo) (3) was slow even at high temperatures (Figures S27 and S28, Supporting Information File 1). Furthermore, RP-HPLC chromatograms of its

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

• increasing concentrations of 2 (A∞ denotes the absorbance at λmax before irradiation; A0 – immediately after exposure to UV light; At – after thermal relaxation for time t). b) Cage concentration dependence of the pseudo-first-order rate constant kobs. c) The proposed mechanism underlying the Pd2

• -1)2, photoisomerization and thermal relaxation studies, and details on X-ray data collection and refinement. In addition, X-ray data for inclusion complex (E-1)22 and the energy-optimized structure for inclusion complex (Z-1)2 are given. Supporting Information File 194: Further experimental details

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

• Jennifer Klose,
• Tobias Severin,
• Peter Hahn,
• Alexander Jeremies,
• Jens Bergmann,
• Daniel Fuhrmann,
• Jan Griebel,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

• macrocycle and the electron poor azobenzene-carboxylato ligands. There are little, if any, differences in the time-scales for thermal relaxation of the free and Cd-bound azobenzene-carboxylate systems, suggesting that the cavity of [Cd2L]2+ does not sterically constrain the photoisomerization process

Azologization of serotonin 5-HT₃ receptor antagonists

• Karin Rustler,
• Galyna Maleeva,
• Piotr Bregestovski and
• Burkhard König

Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

• indicated wavelength or by thermal relaxation (5a, 5b, 12a, 16a–d, 23, and 28). The irradiation times were determined by following the UV–vis spectrum upon isomerization until no more changes in absorption were observed and the photostationary state (PSS) was reached. The points of intersection in the

Synthesis of functionalized diazocines for application as building blocks in photo- and mechanoresponsive materials

• Widukind Moormann,
• Daniel Langbehn and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 727–732, doi:10.3762/bjoc.15.68

• achieved after 2 min of irradiation at 385 nm in yields of 74–85%. All trans-diazocines were converted quantitatively to the cis-configuration either by thermal relaxation or by irradiation at 530 nm. In general, the (trans → cis) isomerization can be accomplished with wavelengths between 520 and 620 nm

• . The half-lives (t1/2) for the thermal relaxation (trans → cis) at 298.15 K of diazocines 4–7 in acetonitrile are between 10.2–16.7 h and thus are in the same order of magnitude as the parent system 1 (15.3 h). In comparison, the 3,3’-diaminodiazocine 2 has a much longer half-life (t1/2) of 24.5 h. The

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

• long-lived metastable HS state (middle left, quadrupole doublet shown in red). Thermal relaxation occurs at 50 K on a 15 minute timescale; the HS doublet disappears in favor of the reappearance of the thermodynamically stable LS state (lower left and upper right: the sample was heated for 15 minutes at

• 50 K and then cooled down quickly to the measuring temperature of 15 K in two runs). As indicated by the spectrum shown in Figure 6 (middle right), thermal relaxation of the metastable HS (LIESST) state to the stable LS state is complete at 100 K. Further heating to 150 K converts the sample

• -forbidden; the long-lived metastable HS state is trapped until radiationless thermal relaxation (heat is transferred to lattice vibrations) sets in by nonadiabatic multiphonon processes [23][149]. Light-induced back conversion (reverse-LIESST) of the metastable LIESST state is effected by irradiating the

Synthesis and testing of the first azobenzene mannobioside as photoswitchable ligand for the bacterial lectin FimH

• Vijayanand Chandrasekaran,
• Katharina Kolbe,
• Femke Beiroth and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2013, 9, 223–233, doi:10.3762/bjoc.9.26

• ) in order to make a photoswitchable FimH antagonist available. Photoirradiation of azobenzene glycosides at ~365 nm effects E→Z isomerisation of the N=N double bond, and thermal relaxation or irradiation at ~450 nm leads to Z→E back isomerisation [13][14]. In the case that the E→Z isomerisation

A bisazobenzene crosslinker that isomerizes with visible light

• Subhas Samanta,
• Harris I. Qureshi and
• G. Andrew Woolley

Beilstein J. Org. Chem. 2012, 8, 2184–2190, doi:10.3762/bjoc.8.246

• with visible light (violet to blue wavelengths). However, the thermal relaxation rate of this crosslinker is rather high (τ½ ~ 1 s in aqueous buffer at neutral pH) so that it is difficult to produce large fractions of the cis,cis-species without very bright light sources. Conclusion: While cis

• -lifetimes may be longer when the crosslinker is attached to a biomolecule, it appears the para-piperazine unit may be best suited for applications where rapid thermal relaxation is required. Keywords: azobenzene; molecular switches; switch; photo-control; visible; Introduction Azobenzene derivatives have

• measurable (Figure 3). The half-life of the irradiated isomers of 2 in phosphate buffer at 4 °C was measured to be 1.5 ± 0.3 s. Numerous cycles of photoisomerization could be carried out without noticeable photobleaching (Figure 3b). The relatively rapid thermal relaxation, however, means that the overall

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• irradiated with light of 400–450 nm, or heated. For many azobenzenes, the two photochemical conversions occur on the scale of picoseconds, while the thermal relaxation of the cis isomer to the trans isomer is much slower (milliseconds to days). The photoinduced isomerization of the azobenzenes leads to a

Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

• Jaume García-Amorós and
• Dolores Velasco

Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113

• the azobenzene core is one of the main factors that allows modulating the thermal relaxation rate of azo-dyes and, therefore, determines the response time of the photochromic molecular switch. The response time of the photochromic switch is a key feature in its overall performance. This parameter is

• μM). From [44] – Reprinted with permission from J. Phys. Chem. B. © 2010, American Chemical Society. Chemical structure and thermal relaxation time in ethanol at 298 K, τ, for the slow thermally-isomerising type-I azoderivatives 1–4. Rotation and inversion mechanisms proposed for the thermal cis-to

• -trans isomerisation processes of azobenzenes. Effect of the presence of the electron-withdrawing cyano and nitro groups on the thermal relaxation time in ethanol at 298 K, τ, for the type-I azoderivatives 5 and 6. Transient absorption generated by UV irradiation (λ = 355 nm) for azo-dyes 8 (right) and 9