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Evidence for the Formation of a Benzo[ a ]phenothiazine/2- Hydroxypropyl-beta-Cyclodextrin Inclusion Complex Using a Fluorescence Method *

Volume 52, Number 1 (Jan. 1998) Page 91-95

Maafi, Mounir; Aaron, Jean-Jacques; Mahedero, Maria Carmen; Salinas, Francisco

The inclusion complex of benzo[ a ]-12H-phenothiazine (BPHT) and 2-hydroxypropyl- beta -cyclodextrin (HP- beta -CD) was investigated in an aqueous solution containing 1% ethanol. It was found that the fluorescence emission intensity of the complexed fluorophore is six times larger than that of uncomplexed species and 1.5 times higher than that in pure ethanol. BPHT forms a 1:1 complex when included in the HP- beta -CD. An association constant of the complex of 100 +/-20 M-1 was calculated by using the Benesi-Hildebrand treatment of fluorescence emission data. A discussion based on AM1 semiempirical calculation of BPHT geometry indicates that the inclusion of BPHT in HP- beta -CD is partially achieved, probably by the hydrophobic aromatic moiety of the molecule.