Self‐Assembly of Tricuprous Double Helicates: Thermodynamics,Kinetics, and Mechanism

We report in this paper the coordination and kinetic properties of two oligobipyridine strands, which contain three 2,2′‐bipyridine subunits separated by oxydimethylene bridges, the 4,4′‐bis(CONET₂)‐substituted L and the 4,4′‐bis(CO₂Et)‐substituted L ′. Spectrophotometric measurements allowed the characterization of thermodynamic complexes and kinetic intermediates* which are involved in the self‐assembly process of L ₂Cu₃ and L Cu₃ helicates. The reaction presents positive cooperativity for the binding of two 2,2′‐bipyridine strands to the cuprous cations. While reactive kinetic intermediates* present distorted coordination geometries around Cu^I, the final rearrangement of the tricuprous bistranded helicates allows more closely tetrahedral coordination of each cation and reduces the interactions. Differences in the bulkiness and electronic properties of the L and L ′ substituents do not affect significantly the stability of the corresponding helicates, but greatly influence binding rates in the self‐assembly process.