Gold(I) Macrocycles and Topologically Chiral [2]Catenanes

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Abstract
The design and synthesis of a new type of topologically chiral [2]catenane is reported. The compounds are formed easily by self-assembly on reaction of the oligomeric digold(I) diacetylide precursor complex [{4-BrC6H4CH(4-C6H4OCH2CCAu)2}n] with diphosphine ligands. Reactions with the diphosphines PP = bis(diphenylphosphinophoshino)acetylene, trans-1,2-bis(diphenylphosphino)ethylene, bis(diphenylphosphino)ethane, and 1,1‘-bis(diphenylphosphino)ferrocene yield simple ring complexes [4-BrC6H4CH(4-C6H4OCH2CCAu)2(μ-PP)] as the only products, since the spacer groups in the diphosphines are not long enough or are too bulky to allow catenane formation. Reaction with PP = bis(diphenylphosphino)propane or bis(diphenylphosphino)butane gave [2]catenane complexes [{4-BrC6H4CH(4-C6H4OCH2CCAu)2(μ-PP)}2], whose structures are confirmed crystallographically. The macrocyclic ring compounds have Cs symmetry but, as a result of the presence of the unsymmetrical “hinge group” 4-BrC6H4CH, the [2]catenanes have C2 symmetry and so are topologically chiral. In favorable cases, the formation of the [2]catenane can be proved by NMR spectroscopy since catenane formation leads to nonequivalence of most ring atoms. The formation of the [2]catenanes was successfully predicted based on the conformation of the precursor bis(phenol), and it is argued that the methods used should be more generally applicable to the synthesis of functionally substituted supermolecules of interest for application in molecular devices.

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