Light‐Controlled Destruction and Assembly: Switching between Two Differently Composed Cage‐Type Complexes

Abstract

We report on two regioisomeric, diazocine ligands 1 and 2 that can both be photoswitched between the E‐ and Z‐configurations with violet and green light. The self‐assembly of the four species (1‐Z, 1‐E, 2‐Z, 2‐E) with CoII ions was investigated upon changing the coordination vectors as a function of the ligand configuration (E vs Z) and regioisomer (1 vs 2). With 1‐Z, Co2(1‐Z)3 was self‐assembled, while a mixture of ill‐defined species (oligomers) was observed with 2‐Z. Upon photoswitching with 385 nm to the E configurations, the opposite was observed with 1‐E forming oligomers and 2‐E forming Co2(2‐E)3. Light‐controlled dis/assembly was demonstrated in a ligand competition experiment with sub‐stoichiometric amounts of CoII ions; alternating irradiation with violet and green light resulted in the reversible transformation between Co2(1‐Z)3 and Co2(2‐E)3 over multiple cycles without significant fatigue by photoswitching.

Azoheteroarene und Diazocine als Molekulare Photoschalter: Selbstassemblierung, Responsive Materialien und Photopharmakologie

“…[97] Anschließend wurde eine durch Metallkoordination angetriebene Selbstorganisation von DZ-basierten Liganden mit Co 2 + -Ionen getestet, die metastabile metallorganische Käfige bildeten (Abbildung 7b). [98] In einer anderen Studie installierten Chen und Mitarbeiter über eine Amidbindung hydrophobe Einheiten auf beiden des DZ, die sich in unpolaren Kohlenwasserstoff-Lösungsmitteln selbst anordneten und bei höheren Konzentrationen Organogele bildeten (Abbildung 7c). [92] Ein reversibler Sol-Gel-Übergang und eine Veränderung der Morphologie war wurde durch die Bestrahlung mit grünem Licht erreicht.…”

“…(a) und (b) Einkapselung von Gast-Molekülen in DZbasierten dynamischen Käfigen. [97,98] (c) Photoresponsives DZ-Organogel vorgestelllt von Chen. [92] (d) Diindan-DZ mit besonders effizienter Energieumwandlung von Herges.…”

Shining a Light on Dissipative Supramolecular Assemblies

“…The Herges group reported the self-assembly and interconversion of a similar supramolecular system containing the regioisomeric 2-pyridyltriazole-substituted diazocine ligands L2 and L3 together with Co II ions. 10b Even though both ligands Z - L2 and Z - L3 show similar bite angles (61° and 63°), the cage [Co 2 ( Z - L2 ) 3 ] 4+ assembles exclusively, whereas the regioisomeric congener Z - L3 does not assemble into well-defined structures (Figure 3 ) when both ligands are mixed. Irradiating the cage and ligands at 385 nm induces Z → E isomerization to give [Co 2 ( E - L3 ) 3 ] 4+ and free E - L2 .…”

Reactions in Endohedral Functionalized Cages

“…The ligand that gave oligomers with the Z-form results now in the formation of a Co 2 (L-E) 3 species. [31] After this brief overview on current developments for an enhanced functionalization of supramolecular cage compounds, the focus should now lie on an additional way to bring function into cage chemistry. That is the introduction of endohedralfunctionalization into the cage cavities (Figure 1, right).…”

“…Switching to the E ‐form, the opposite was observed. The ligand that gave oligomers with the Z ‐form results now in the formation of a Co 2 (L‐ E ) 3 species [31] …”