Unusual Excited State Characteristics of 6-aminobenzothiazole with Delta b-cyclodextrin

The interaction between 6-aminobenzothiazole (6ABT) and Delta *b-cyclodextrin ( Delta *b-CDx) has been investigated in solution and solid state. The stoichiometry and binding constants of the complex between 6ABT and Delta *b-CDx in solution have been determined by steady state and time-resolved fluorescence spectroscopy. Fluorescence intensity of neutral form decreases during complexation which is contrary to the usual observation. This is explained by hydrogen bonding interaction between lone pair of nitrogen with OH groups of Delta *b-CDx. The FT-IR spectral study and SEM images of solid complex confirmed the formation of inclusion complex. Excited state acidity constants for 6ABT have been determined in aqueous and Delta *b-CDx medium and discussed.