Dual fluorescence of 4-dimethylaminobenzonitrile (DMABN) in the presence of
hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and dimethyl-beta-cyclodextri
n (DM-beta-CD) in aqueous media is reported. Equilibrium constants for the
formation of inclusion complexes between DMABN and CD-derivatives are calcu
lated for the ground as well as the excited states. Two maxima are observed
in the excitation spectra, indicating the presence of two absorbing specie
s. Fluorescence lifetimes of these complexes are also reported in addition
to their ICD spectra. Based on the experimental observations, it is conclud
ed that while the more polar TICT emission originates from the aqueous exte
rior, LE emission occurs predominantly from the complexed molecule. Higher
order complexes are not observed. Absence of hydrogen bonding and a 'tighte
r fit' with the CD derivatives are the main factors responsible for this. (
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