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.