Topological Kinetic Effects: Complexation of Interlocked Macrocyclic Ligands by Cationic Species

Article abstract of DOI:10.1021/ja00213a018

Complexation of kinetic studies of various metal cations by a catenand have been performed.For comparison, the properties of some related open chain or monocyclic ligands have also been examined.Copper(I) and silver(I) catenate formation obeys a classical second-order rate law.The same is true for the model ligands examined, m-30 and dap.For Cu(dap)2⁺, the rate-limiting step corresponds to the formation of the bis-chelate complex from the monochelated one.On the other hand, Li⁺, Cd²⁺, Zn²⁺, and Co²⁺ catenates are formed in two distinct steps.The first process is second order, and it is likely to be the binding of the metallic cation to one of the chelating subunits.The second step is more intriguing.It does not depend on the metal concentration, and it might correspond to the gliding motion of one ring within the other while the second chelate fragment attempts to coordinate to the metal center.