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 π–π interactions between the benzene rings, while such interactions cease to exist with the pyridyl linkers, leading to the formation of noninterlocked macrocycles