Guest-binding and structural reorganization in stimuli-responsive coordination cages

Rujin Li, TU Dortmund, Dortmund, Germany
Muxin Han, Georg August Universität Göttingen, Göttingen, Germany
Guido H. Clever, TU Dortmund, Dortmund, Germany

In supramolecular chemistry, banana-shaped bis-monodentate ligands form the basis of a family of coordination cages whose members show variable topologies, rich encapsulation properties and several functional features.[1] Among these, switchable host-guest systems are of particular interest because they promise to find application in fields such as uptake & release of molecular cargo, sensing and separation as well as catalysis inside confined molecular environments. Our current research efforts focus on the triggering of structural reorganizations and the implementation of reversible control over the size and shape of the cages’ internal cavities.[2-3]

We present photochromic coordination cages based on dithienylethene (DTE) ligands in which light of different wavelengths was used as a trigger to reversibly switch guest uptake and release in solution.[4] Such systems may spur the development in subfields of nanotechnology and materials science such as drug delivery, switchable receptors, supramolecular catalysis and adaptive compounds.

Upon slight changes in the design of the DTE ligand, light was shown to induce a complete structural reorganization of the self-assembled system, going from small triangular rings to 7 nm large, spherical assemblies consisting of 24 palladium(II) cations and 48 ligands.[5]

[1] M. Han, D. M. Engelhard, G. H. Clever, Chem. Soc. Rev. 2014, 43, 1848.
[2] S. Löffler, J. Lübben, L. Krause, D. Stalke, B. Dittrich, G. H. Clever, J. Am. Chem. Soc. 2015, 137, 1060.
[3] R. Zhu, J. Lübben, B. Dittrich, G. H. Clever, Angew. Chem. Int. Ed. 2015, 54, 2796.
[4] M. Han, R. Michel, B. He, Y.-S. Chen, D. Stalke, M. John, G. H. Clever, Angew. Chem. Int. Ed. 2013, 52, 1319.
[5] M. Han, Y. Luo, B. Damaschke, L. Gómez, X. Ribas, A. Jose, P. Peretzki, M. Seibt, G. H. Clever, Angew. Chem.Int. Ed. 2016, 55, 445.

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