Unique Ruthenium Bimetallic Supramolecular Cages From C₄-Symmetric Tetrapyridyl Metalloligands

The self-assembly of C₄-symmetric tetrapyridyl metalloligands containing Fe or Co and diruthenium electron acceptors by means of dative coordination bonding led to the formation of six different heterobimetallic supramolecules. All complexes were characterized by X-ray crystallography, ESI mass spectrometry, and ¹H NMR (in the case of diamagnetic systems) spectroscopy. The bridging units in the diruthenium complexes greatly influenced the geometrical preference of the supramolecular structures, resulting in the formation of different architectures, namely A₄D₂ or A₆D₃ (A = acceptor, D = donor). Depending on the bridging unit, A₄D₂ tetragonal prism, A₄D₂ molecular tweezer, or A₆D₃ triple-decker complexes were obtained selectively. The self-assembly of an unexpected triple-decker type Ru₁₂Fe₃ heterobimetallic species was also observed.