Abstract
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.
Highlights
Most metallo-supramolecular assemblies of low nuclearity adopt simple topologies, with bridging ligands spanning neighboring metal centers in a direct fashion
In the large family of [PdnL2n] assemblies, consisting of squareplanar coordinated PdII cations surrounded by bis-monodentate bridging ligands, this trend and its exceptions can be nicely observed.[3]
We present the first example of a [Pd2L4] structural motif containing both metals chelated by two bidentate donors, in which these two Figure-eight-shaped
Summary
Most metallo-supramolecular assemblies of low nuclearity adopt simple topologies, with bridging ligands spanning neighboring metal centers in a direct fashion. [Pd2L4], a large variety of the topologically most simple lantern-shaped cages (Figure 1 a) were reported by Steel,[3b] Fujita,[12] Yoshizawa,[13] Chand,[3e,14] Crowley,[3f,15] our group[8,16] and others.[17] Recently, we introduced the first example of a self-penetrating [Pd2L4] topology, albeit composed of two different ligands in a heteroleptic fashion (Figure 1 b).[18] Here, we present the first example of a [Pd2L4] structural motif containing both metals chelated by two bidentate donors, in which these two Figure-eight-shaped
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