Quantitative Kinetic Modeling in Photoresponsive Supramolecular Chemistry: The Case of Water-Soluble Azobenzene/Cyclodextrin Complexes

Hydrophilic
host–guest complexes, consisting of water-soluble
azobenzene and α-, β-, or γ-cyclodextrins, have
been proposed as a model to study supramolecular photoresponsive systems
in aqueous environments through a full spectrometric approach combined
with a simulation and data fitting methodology. Various essential
and complementary spectroscopic techniques have been used: circular
dichroism to determine whether the complex is formed or not, NMR for
the stoichiometry elucidation, and UV–visible spectrophotometry
to obtain the association equilibrium constant of each complex and
the quantum yield for each photochemical process. A step-by-step fitting
procedure is presented, which enables the determination of all thermodynamic
and photokinetic parameters. A sequential methodology is applied to
dissipate all uncertainties on the variability of the results and
to develop a relevant and reliable protocol applicable to other types
of complexes. The proposed procedure has thus been shown to be very
robust and largely applicable to other photoresponsive host–guest
systems.