pH Independent Complexation of ۲-Aminobenzimidazole with β-cyclodextrin

The spectral characteristics of ۲-aminobenzimidazole (۲ABZ) in aqueous and β-cyclodextrin media has been investigated using absorption, steady state and time resolved fluorescence techniques. The stoichiometric ratio of the inclusion complex of neutral and monocationic forms of ۲ABZ in β-CDx medium is found to be ۱:۱. There is no significant differences between ground and the excited state pKa values of ۲ABZ under both the media and thus the amino group of ۲ABZ molecule is not much affected by the complexation process i.e., it lies outside the β-CDx cavity. Considering the shape and dimensions of β-CDx, it is clear that the ۲ABZ molecule cannot be completely included in the β-CDx cavity. Because, the overall height of ۲ABZ is ۱۰.۶ Å, but the overall height of β-CDx is only ۷.۸ Å. Hence, it is possible to locate half of the ۲ABZ molecule only permitted inside the β-CDx cavity as interpreted using experimental data.

Keywords:

۲-Aminobenzimidazole , inclusion complex , Lifetime , Acidity constant , Patch-Dock server