Dynamics for the assembly of pyrene-γ-cyclodextrin host-guest complexes

Pyrene and gamma-cyclodextrin (gamma-CD) form complexes with 1: 1, 1:2, and 2:2 (pyrene/CD) stoichiometries. The complexation dynamics was studied using stopped flow. The dynamics for the higher-order complexes (1:2 and 2:2) occurs in the millisecond time domain, which contrasts with the much faster dynamics for the 1:1 complex. When pyrene is mixed with gamma-CD, a transient enhancement of the concentration for the 2:2 complex was observed between 0.2 and I s, which at longer times leads to the formation of the 1:2 complex. This enhancement of the nonthermodynamic product is an example of the kinetic formation of a host-guest complex, and these types of processes may be explored to build self-assemblies under kinetic control.