Lichtgesteuerte Konstruktion und Zerstörung: Schaltung zwischen zwei unterschiedlich zusammengesetzten käfigartigen Komplexen

Wir berichten über zwei regioisomere Diazocinliganden1 und 2, die beide mit violettem und grünem Lichtzwischenden E- undZ Konfigurationen geschaltet werden können. Die Selbstorganisationder vier Spezies(1-Z,1-E,2-Z,2-E) mit CoII-Ionen wurde nach Änderung der Koordinationsvektoren in Abhängigkeit von der Ligandenkonfiguration (Evs.Z) und dem Regioisomer (1vs.2) untersucht. Mit1-Zbildetsich Co2(1-Z)3, während mit 2-Z ein undefiniertes Gemisch verschiedener Spezies(Oligomere) beobachtet wurde. Bei Belichtung der E-Konfigurationen mit 385 nm wurde die gegenteilige Situation beobachtet, wobei 1-E Oligomere und 2-Eden KomplexCo2(2-E) 3 bildete.Der lichtgesteuerte Abbau/Aufbau wurdein einem Ligandenverdrängungsexperiment mit substöchiometrischen Mengen von CoII-Ionen demonstriert. Die abwechselnde Bestrahlung mit violettem undg rünem Licht führte zu einer reversiblen Umwandlung zwischenCo2(1-Z) 3 und Co2(2-E) 3 übermehrere Zyklen hinweg ohne signifikante Ermüdung

Photoswitchable diazocine-based estrogen receptor agonists: stabilization of the active form inside the receptor

Photopharmacology is an emerging approach in drug design and pharmacological therapy. Light is used to switch a pharmacophore between a biologically inactive and an active isomer with high spatiotemporal resolution at the site of illness, thus potentially avoiding side effects in neighboring healthy tissue. The most frequently used strategy to design a photoswitchable drug is to replace a suitable functional group in a known bioactive molecule with azobenzene. Our strategy is different in that the photoswitch moiety is closer to the drug’s scaffold. Docking studies reveal a very high structural similarity of natural 17β-estradiol and the E isomers of dihydroxy diazocines, but not their Z isomers, respectively. Seven dihydroxy diazocines were synthesized and subjected to a biological estrogen reporter gene assay. Four derivatives exhibit distinct estrogenic activity after irradiation with violet light, which can be shut off with green light. Most remarkably, the photogenerated, active E form of one of the active compounds isomerizes back to the inactive Z form with a half-life of merely several milliseconds in water, but nevertheless is active for more than 3 h in the presence of the estrogen receptor. The results suggest a significant local impact of the ligand–receptor complex toward back-isomerization. Thus, drugs that are active when bound but lose their activity immediately after leaving the receptor could be of great pharmacological value because they strongly increase target specificity. Moreover, the drugs are released into the environment in their inactive form. The latter argument is particularly important for drugs that act as endocrine disruptors

Triplet-Sensitized Bidirectional Isomerization of Bridged Azobenzene

Diazocine is a bridged azobenzene with both phenyl rings connected by a CH2-CH2 group. Despite this rather small structural difference, diazocine exhibits improved properties over azobenzene as a photoswitch, such as high switching efficiencies, very high quantum yields, switching wavelengths in the visible range, and most importantly, the fact that it is more stable in the Z configuration, which is particularly expedient in photopharmacology and mechanophore applications. According to our studies presented here, another advantage over conventional azobenzene is now added. In contrast to azobenzenes and other photochromes, diazocine can be switched with two different triplet sensitizers present at the same time in both directions: Z→E as well as E→Z. Experimental and theoretical (CASPT2) studies of triplet excitation energies provide an explanation for this fact. The triplet energies in Z and E azobenzene are almost equal, which prevents selective sensitization of either isomer. In diazocine, the two excitation energies are well-separated, so they can be accessed selectively. Besides offering fundamental physical insight to diazocines, an emerging class of photoswitches, our work opens up a number of potential avenues for utilizing them for example in photopharmacology and smart materials design due to the significant redshift of excitation wavelengths to from blue to green (Z→E) and green to far-red (E→Z), which triplet sensitization offers

Triplet sensitization enables bidirectional isomerization of diazocine with 130 nm redshift in excitation wavelengths

Diazocines are bridged azobenzenes with phenyl rings connected by a CH2–CH2 group. Despite this rather small structural difference, diazocine exhibits improved properties over azobenzene as a photoswitch and most importantly, its Z configuration is more stable than the E isomer. Herein, we reveal yet another unique feature of this emerging class of photoswitches. In striking contrast to azobenzenes and other photochromes, diazocine can be selectively switched in E → Z direction and most intriguingly from its thermodynamically stable Z to metastable E isomer upon successive excitation of two different triplet sensitizers present in solution at the same time. This approach leads to extraordinary large redshift of excitation wavelengths to perform isomerization i.e. from 400 nm blue to 530 nm green light (Z → E) and from 530 nm green to 740 nm far-red one (E → Z), which falls in the near-infrared window in biological tissue. Therefore, this work opens up of potential avenues for utilizing diazocines for example in photopharmacology, smart materials, light energy harvesting/storage devices, and out-of-equilibrium systems.Peer reviewe