A New Mechanically‐Interlocked [Pd2L4] Cage Motif by Dimerization of two Peptide‐based Lemniscates

• Published in: Angewandte Chemie International Edition Vol. 59; no. 50; pp. 22489 - 22493
• Main Authors: Schulte, Thorben R., Holstein, Julian J., Schneider, Laura, Adam, Abdulselam, Haberhauer, Gebhard, Clever, Guido H.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 07-12-2020; John Wiley and Sons Inc
• Edition: International ed. in English
• Subjects: Assemblies; Cages; catenane; chirality; Communication; Communications; coordination cage; Dimerization; Ligands; mechanical bond; Metallography; Metals; Natural products; NMR; Nuclear magnetic resonance; supramolecular chemistry; Topology; coordination cage; chirality; catenane; mechanical bond; supramolecular chemistry
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202010995

Most metallo‐supramolecular assemblies of low nuclearity adopt simple topologies, with bridging ligands spanning neighboring metal centers in a direct fashion. Here we contribute a new structural motif to the family of host compounds with low metal count (two) that consists of a pair of doubly‐interlocked, Figure‐eight‐shaped subunits, also termed “lemniscates”. Each metal is chelated by two chiral bidentate ligands, composed of a peptidic macrocycle that resembles a natural product with two pyridyl‐terminated arms. DFT calculation results suggest that dimerization of the mononuclear halves is driven by a combination of 1) Coulomb interaction with a central anion, 2) π‐stacking between intertwined ligand arms and 3) dispersive interactions between the structure's compact inner core bedded into an outer shell composed of the cavitand‐type macrocycles. The resulting cage‐like architecture was characterized by NMR, MS and X‐ray structure analyses. This new mechanically bonded system highlights the scope of structural variety accessible in metal‐mediated self‐assemblies composed of only a few constituents.
A chiral macrocycle, equipped with two pyridine donors, assembles with PdII cations to an unprecedented metallo‐supramolecular architecture by pairwise catenation of two figure‐eight‐shaped subunits. Interlocking in solid state and solution is driven by close non‐covalent interaction between the basket‐shaped macrocycles and coordinating ligand arms.