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 M₈L ₄ tubular complexes via subcomponent self-assembly, starting from Cu^I or Ag^I 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 (D_2d 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 Au^I, the D ₄-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.