Dynamics for the Assembly of Pyrene−γ-Cyclodextrin Host−Guest Complexes

Pyrene and γ-cyclodextrin (γ-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 γ-CD, a transient enhancement of the concentration for the 2:2 complex was observed between 0.2 and 1 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.