Selective synthesis of iridium(III)-derived molecular Borromean rings, [2]catenane and ring-in-ring macrocycles via coordination-driven self-assembly

This paper reports the formation of unprecedented iridium(III)-derived topological macrocycles. Discrete molecular Borromean rings 1 and 3 in pure form are synthesized via coordination-driven self-assembly of an acceptor [(Cp*Ir)(2)(OO boolean AND OO)](OTf)(2) (Cp* = pentamethylcyclopentadienyl, OO boolean AND OO = 6,11-dioxido-5,12-naphthacenedione) (A) with dipyridyl donors 1,4-bis(4-pyridinylethynyl) benzene (L-1) and 2,5-bis(4-pyridinylethynyl) thiophene (L-2) respectively in methanol. Self-assembly using the same acceptor under similar conditions with two other donors 9,10-bis(4-pyridinylethynyl) anthracene (L-3) and 1,4-di(4-pyridinyl-ethynyl)buta-1,3-diyne (L-4) resulted in [2] catenane 5 and non-catenane ring-in-ring topological macrocycle 7 respectively. Rectangular macrocycles 2, 4, 6, and 8 were respectively obtained when the selfassembly of acceptor A with one of the donors L-1-L-4 was carried out under dilute conditions in nitromethane or methanol. All these new macrocycles were characterized by H-1 and C-13 NMR, 2D NMR, ESI-MS and elemental analyses. Single crystal X-ray structures of Borromean rings 1 and 3, and ring-in-ring macrocycle 7 revealed that the length and functionality of donors enabling CH center dot center dot center dot pi and pi center dot center dot center dot pi interactions govern the topology.