Microenvironmental effects in the excited state properties of p-dimethylaminobenzonitrile complexed to ?- and ?-cyclodextrinDedicated to Professor Jean Kossanyi on the occasion of his 70th birthday.

The steady, state and time resolved fluorescence and the triplet-triplet absorption of p-dimethylaminobenzonitrile (DMABN) in presence of alpha- and beta-cyclodextrin (CD) were investigated at various host and guest concentrations and temperatures. The formation of I : I and 1 :2 DMABN: alpha-CD and 1 : 1 and 2: 2 complexes DMABN: beta-CD complexes was ascertained by applying global analysis methods. The "pure" fluorescence spectra as well as the emission quantum yields and lifetimes and the triplet properties of the various associates were determined. The role of environmental features in the radiative and non-radiative deactivation of the LE and ICT excited states of the complexed DMABN was elucidated.