Modulation of complexation of 4(1H-pyrrole 1-yl) benzoic acid with β-cyclodextrin in aqueous and non-aqueous environments

This Letter reports a very interesting observation of 1:1 inclusion complex of 4(1H-pyrrole 1-yl) benzoic acid (PBA) with β-cyclodextrin (β-CD) in aqueous solution having an orientation of benzoic acid residing inside the cavity and the pyrrole group available in the bulk medium. In the non-aqueous solution surprisingly PBA does not form inclusion complex but forms an association with variation of β-CD concentration in the rim region affecting the free rotation of donor moiety. Absence of driving force and dissimilar solvation of pyrrole and benzoic acid moieties in N,N-dimethyl formamide solution attributed for PBA not getting inside the cavity.