Ruthenium(II) Metalla[2]catenanes and Macrocycles via Donor-Dependent Self-Assembly

Donor-selective coordination-driven self-assembly of a bis(dipyrrin)-bridged new diruthenium acceptor (RuA) with dipyridyl and diimidazolyl donors has been reported. The self-assembly of the ruthenium(II) acceptor with imidazolyl donors resulted in the formation of either [2 + 2] self-assembled monomeric macrocycles (MMs) or a mixture of metalla[2]catenanes (MCs) and MMs depending on the solvents used. On the contrary, similar self-assembly with the pyridyl donors resulted in simple [2 + 2] macrocycles (MMs) exclusively, irrespective of the solvents used. The new ruthenium acceptor and self-assembled macrocycles were systematically characterized by multinuclear NMR and electrospray ionization mass spectrometry study. The structure of one of the metalla[2]catenanes (MC1) was further confirmed by single-crystal X-ray diffraction studies. Density functional theory calculations inferred that the interlocked structures with imidazolyl donors are stabilized by pi-pi interactions between the benzene rings, while such interactions cease to exist with the pyridyl linkers, leading to the formation of noninterlocked macrocycles.