Light-triggered reversible disassembly of stimuli-responsive coordination metallosupramolecular Pd₂L₄ cages mediated by azobenzene-containing ligands

Abstract

A light-stimuli-responsive supramolecular azobenzene-containing M2L4 cage has been designed and synthesized. This cage can be reversibly disassembled/reassembled mediated by the azo-ligand under visible and UV light irradiation.

UV/enzyme dual responsive photosensitizer‐loaded 4‐(Phenylazo)benzoic Acid‐mPEG nanosystem for enhanced photodynamic insecticide efficacy

“…5(b), the absorbance intensity at 325 nm gradually increased with exposure time until it returned to its initial strength after 50 min, showing completely reversible cis‐trans conversion. Similar results had been reported in previous studies 43,44 . The changes in UV–vis absorbance were attributed to the reversible photoisomerization of AZO.…”

“…Similar results had been reported in previous studies. 43,44 The changes in UV-vis absorbance were attributed to the reversible photoisomerization of AZO.…”

Visible‐Light Switching of Metallosupramolecular Assemblies**

“…Another example used a 3pyridyl functionalized azobenzene and palladium(II) to form M 2 L 4 dimers that disassembled on irradiation. [27] However, the most well-studied photoswitchable cages are based on pyridylfunctionalized DTE photoswitches assembled with palladium(II) ions reported by the Clever group. [28] The difference in geometries has been exploited for selective guest uptake, [28a,d,e] and control over macromolecular properties when incorporated into gels.…”

“…Photoswitching units can also modulate the connectivity of metallosupramolecular structures; however, this usually leads to the assembly of new non‐discrete structures [27,30] . There are few reported examples of modulation between discrete metallosupramolecular structures, with some key examples represented in Figure 1b,c [28b,31] .…”

Light‐Triggered High‐Affinity Binding of Tetramethylammonium over Potassium Ions by [18]crown‐6 in a Tetrahedral Anion Cage

“…Notably, a few azo (or other photoactive groups)‐decorated metallo‐cycles and cages have been studied in light‐driven structural transformations, e.g. the interconversion of homo‐ or heterometallic (Pd/Re) tetranuclear and dinuclear squares bridged by azobenzene‐pyridyl ligands; [10] assembly and disassembly of Pd 2 L 4 lantern‐shaped cage with an azobenzene‐containing bis‐pyridyl ligand; [11] visible‐light modulated transformations of a dynamic mixture of Pd 3 L 6 and Pd 4 L 8 complexes with ortho‐fluoroazobenzene modified pyridyl ligands; [7] light‐driven structural rearrangement of a Pd 3 L 6 ring based on bis(3‐pyridyl)dithienylethene ligands into a rhombicuboctahedral Pd 24 L 48 sphere; [6a] among other examples [12] . However, the M 4 L 6 tetrahedron had not been accessed until very recently that the [Zn 4 L 6 ] 8+ complex with dynamic coordination of a bis(diimine) ligand incorporating an azobenzene linker was reported, yet the azo bonds were locked without structural transformation under UV light [5c] .…”