Unravelling the Roles of Solvophobic Effects and π⋅⋅⋅π Stacking Interactions in the Formation of [2]Catenanes Featuring Di‐(N‐Heterocyclic Carbene) Building Blocks
Ya‐Wen Zhang, Ye Lu, Li‐Ying Sun, Patrick D. Dutschke, Ming‐Ming Gan, Le Zhang, Alexander Hepp, Ying‐Feng Han, F. Ekkehardt Hahn
Abstract
Abstract A series of [2]catenanes has been prepared from di‐NHC building blocks by utilizing solvophobic effects and/or π⋅⋅⋅π stacking interactions. The dinickel naphthobiscarbene complex syn ‐[ 1 ] and the kinked biphenyl‐bridged bipyridyl ligand L 2 yield the [2]catenane [ 2‐IL ](OTf) 4 by self‐assembly. Solvophobic effects are pivotal for the formation of the interlocked species. Substitution of the biphenyl‐linker in L 2 for a pyromellitic diimide group gave ligand L 3 , which yielded in combination with syn ‐[ 1 ] the [2]catenane [ 3‐IL ](OTf) 4 . This assembly exhibits enhanced stability in diluted solution, aided by additional π⋅⋅⋅π stacking interactions. The π⋅⋅⋅π stacking was augmented by the introduction of a pyrene bridge between two NHC donors in ligand L 4 . Di‐NHC precursor H 2 ‐ L 4 (PF 6 ) 2 reacts with Ag 2 O to give the [Ag 2 L 4 2 ] 2 [2]catenane [ 4‐IL ](PF 6 ) 4 , which shows strong π⋅⋅⋅π stacking interactions between the pyrene groups. This assembly was readily converted into the [Au 2 L 4 2 ] 2 gold species [ 5‐IL ](PF 6 ) 4 , which exhibits exceptional stability based on the strong π⋅⋅⋅π stacking interactions and the enhanced stability of the Au‐C NHC bonds.