A Rotaxane-like Cage-in-Ring Structural Motif for a Metallosupramolecular $\mathrm{Pd_{6}L_{12}}$ Aggregate

A BODIPY‐based bis(3‐pyridyl) ligand undergoes self‐assembly upon coordination to tetravalent palladium(II) cations to form a Pd$_6$L$_{12}$ metallosupramolecular assembly with an unprecedented structural motif that resembles a rotaxane‐like cage‐in‐ring arrangement. In this assembly the ligand adopts two different conformations—a C‐shaped one to form a Pd$_2$L$_4$ cage which is located in the center of a Pd$_4$L$_8$ ring consisting of ligands in a W‐shaped conformation. This assembly is not mechanically interlocked in the sense of catenation but it is stabilized only by attractive π‐stacking between the peripheral BODIPY chromophores and the ligands’ skeleton as well as attractive van der Waals interactions between the long alkoxy chains. As a result, the co‐arrangement of the two components leads to a very efficient space filling. The overall structure can be described as a rotaxane‐like assembly with a metallosupramolecular cage forming the axle in a metallosupramolecular ring. This unique structural motif could be characterized via ESI mass spectrometry, NMR spectroscopy, and X‐ray crystallography