Empirical and Theoretical Insights into the Structural Features and Host–Guest Chemistry of M₈L₄ Tube Architectures

We demonstrate a general method for the construction of M8L4 tubular complexes via subcomponent self-assembly, starting from CuI or AgI precursors together with suitable elongated tetraamine and 2-formylpyridine subcomponents. The tubular architectures were often observed as equilibrium mixtures of diastereomers having two different point symmetries (D2d or D2 ⇄ D4) in solution. The equilibria between diastereomers were influenced through variation in ligand length, substituents, metal ion identity, counteranion, and temperature. In the presence of dicyanoaurate­(I) and AuI, the D4-symmetric hosts were able to bind linear Au­(Au­(CN)2)2– (with two different configurations) as the best-fitting guest. Substitution of dicyanoargentate­(I) for dicyanoaurate­(I) resulted in the formation of Ag­(Au­(CN)2)2– as the optimal guest through transmetalation. Density functional theory was employed to elucidate the host–guest chemistries of the tubes.