Inclusion complexation of 2-amino-7-bromofluorene by beta-cyclodextrin: spectral characteristics and the effect of pH.

Spectral characteristics of 2-amino-7-bromofluorene (2ABF) have been studied in aqueous beta-cyclodextrin (beta-CDx) solution. Enhancement in the fluorescence intensity of the neutral from of 2ABF was observed due to the formation of 1:1 complex with beta-CDx. The formation of this complex was confirmed by time-resolved fluorescence spectroscopy. The ground state pKa value for the monocation-neutral equilibrium of 2ABF in beta-CDx shows no change with that in aqueous solution, but the excited state pKa value changes. Based on its photophysical and photoprototropic characteristics in beta-CDx, the structure of the 1:1 inclusion complex is proposed.