Inorganic Chemistry

Visible light switching of metallosupramolecular assemblies



A photoswitchable ligand and palladium(II) ions form a dynamic mixture of self-assembled metallosupramolecular structures. The photoswitching ligand is an ortho-fluoroazobenzene with appended pyridyl groups. The E-isomer is combined with palladium(II) salts affords a double-walled triangle with composition [Pd3L6]6+ and a distorted tetrahedron [Pd4L8]8+(1:2 ratio at 298 K). Irradiation with 410 nm light generates a photostationary state with ~80% of the E-isomer of the ligand which results in the selective disassembly of the tetrahedron, the more thermodynamically stable structure, and the formation of the triangle, the kinetic product. The triangle is then slowly transformed back into the tetrahedron over 2 days at 333 K. The Z-isomer of the ligand does not form any well-defined structures and has a thermal half-life of 25 days at 298K. This approach shows how a thermodynamically preferred self-assembled structure can be reversibly pumped to a kinetic trap by small perturbations of the isomer distribution using non-destructive visible light.


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Supplementary material

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Supplementary Information
All the supplementary information.
Thumbnail image of 1 - NMR characterisation of synthesised
All the NMR data for this work
All the 1H, 19F, 13C and 2D NMR data for photoswitches 3 and 4, and the Pd(tty)2+ complex.
Thumbnail image of 2 - Photoswitching data for ligand
Photoswitching data for 3
All the UV-vis and NMR data from photoswitching experiments with ligand 3.
Thumbnail image of 3 - Photoswitching data for ligand
Photoswitching data for 4
All the UV-vis and NMR data from photoswitching experiments with photoswitch 4.
Thumbnail image of 4 - Characterisation of [Pd3(3)6](BF4)6 and [Pd4(3)8](BF4)
Characterisation of self-assembled species
All NMR (1H, 19F, 13C, 2D and diffusion) and UV-vis absorption data for the self-assembled species [Pd3L6]6+ and [Pd4L8]8+.
Thumbnail image of 5 - Binding
Binding constant measurments
All binding constant measurements using ITC and competitive binding experiment by 1H NMR.
Thumbnail image of 6 - Combination of Z-3 and
Self-assembly with Z-3 and Pd(II)
1H and 19F NMR data from the reaction of the metastable Z-3 ligand with Pd(II).
Thumbnail image of 7 - Formation of self-assembled structures with BArF
Self-assembly of E-3 with a more soluble Pd(II) complex
1H NMR data from the self-assembly of ligand E-3 with [Pd(py*)4](BArF)2
Thumbnail image of 8 - NMR spectra for [Pd(ttpy)(MeCN)](BF4)2 + Py
NMR data for Pd(tty)(MeCN) with 3-methylpyridine or ligand E-3.
1H NMR data for the reaction of [Pd(ttpy)(MeCN)](BF4)2 with 3-methylpyridine or ligand E-3.