Photoinduced intermolecular electron transfer from dimethyl aniline to 7-amino coumarin dyes in the surface of beta-cyclodextrin

The photoinduced electron-transfer reaction between Coumarin dyes and N,N-dimethylaniline has been investigated using steady-state and Time-resolved fluorescence spectroscopy in the surface of beta-cyclodextrin in dimethyl formamide (DMF) solvent. The electron-transfer rate constant has been correlated with the free-energy change during the process. We have observed a diffusion-controlled ET process in pure DMF by showing a normal Marcus region. However, the picture is different in presence of cyclodextrin. Here the ET is retarded at higher free-energy region. This unusual feature in bimolecular electron-transfer reaction is assumed to be arising from the different binding possibility of the Coumarin molecules to the cyclodextrin moity.