Inclusion complexation of 2-(4′-N,N-dimethylaminophenyl)-1H-naphth[2,3-d]imidazole by β-cyclodextrin: effect on the twisted intramolecular charge transfer emission

Spectral characteristics of 2-(4′-N,N-dimethylaminophenyl)-1H-naphth[2,3-d] imidazole (DMAPNI) have been studied in aqueous β-cyclodextrin (β-CDx) solution. Enhancement in the fluorescence intensity of the normal band (B) is more than that of the twisted intramolecular charge transfer (TICT) band (A). pKa value for the protonation of N atom and the blue shifts observed in both the fluorescence bands suggest the encapsulation of DMAPNI in the hydrophobic cavity of β-CDx. Steady state and time resolved spectral analysis support the formation 1:2 complex between DMAPNI and β-CDx. Enhancement in the fluorescence intensity in aqueous β-CDx solution is due to the decrease in the non-radiative processes.