Study of bimolecular processes in ternary cyclodextrin complexes in the solid state by diffuse reflectance laser flash photolysis

Abstract

The photochemistry of binary inclusion complexes of nitroveratrole (NV) and p-dinitrobenzene (DNB) with β-cyclodextrin (β-CD) and of ternary inclusion complexes of NV or DNB and L-phenylethylamine (PhEA) with β-CD has been examined in the solid state by diffuse reflectance laser flash photolysis. The binary NV/β-CD complex shows a transient absorption signal assigned to the triplet excited state of NV. The binary DNB/β-CD complex shows a transient signal assigned to the protonated anion of DNB formed via hydrogen abstraction from the β-CD cavity. Laser excitation of the ternary complexes generates the corresponding radical ion pairs via photoinduced electron transfer from the amine to the nitroaromatic triplet state. Comparison with previously described conventional laser flash photolysis studies in solution shows that the investigation of solid ternary CD inclusion complexes by diffuse reflectance laser flash photolysis is valuable in the case of bimolecular photoreactions that are difficult to study in solution due to the existence of other competitive processes.