Stimuli-Responsive Molecular Dimers Self-Assembled inside Palladium Coordination Cage
The chemical reactivity and physicochemical properties of molecules occluded within confined spaces, though explored to date by numerous research groups, still remain highly unpredictable. Various approaches to this subject, based on organic or metal-organic capsules1,2 as places where molecules can be trapped, have shown the exceptional reactivity or stability of encapsulated compounds.3 These especially include a particular reaction rate acceleration in confined environment, and highly chemo-, enantio- or diastereoselective performance of studied transformations.4,5
We worked with flexible self-assembled Pd6 cage comprising four 1,3,5-tris(1-imidazolyl)benzene units, described by Samanta and co-authors,6 and successfully encapsulated redox-active dyes, i.e. resorufin and resorufamine, within a nonpolar cage’s cavity. Once occluded, the fluorescence of these compounds dramatically decreased due to the formation of homodimeric assemblies. As-produced complexes could be reassembled into heterodimeric structures by an addition of polycyclic aromatic hydrocarbons (e.g. anthracenes), to result in highly fluorescent systems. Finally, our cage-stabilized dye/arene dimers exhibited photoactive and redox-switchable properties, what allowed us to tune their photochemical response by applying light of specific wavelengths or upon reversible reduction of the dye.
1. Tian, N.; Zhou, Z.; Sun, S.; Ding, Y.; Wang, Z. Science 2007, 316, 732.
2. Suzuki, K.; Sato, S.; Fujita, M. Nat. Chem. 2009, 2, 25.
3. Yoshizawa, M.; Tamura, M.; Fujita, M. Science 2006, 312, 251.
4. Kang, J.; Rebek, J. Nature 1997, 385, 50.
5. Zhao, H.; Sen, S.; Udayabhaskararao, T.; Sawczyk, M.; Kučanda, K.; Manna, D.; Kundu, P.; Lee, J.; Král, P.; Klajn, R. Nat. Nanotech. 2016, 11, 82.
6. Samanta, D.; Mukherjee, S.; Patil, Y.; Mukherjee, P. Chem. Eur. J. 2012, 18, 12322.
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