Absorptiometric and spectrofluorimetric study of the inclusion complexes of 2-naphthyloxyacetic acid and 1-naphthylacetic acid with ?-cyclodextrin in aqueous solution

Abstract

The inclusion complexes of 2-naphthyloxyacetic acid (NOA) and 1-naphthylacetic acid (NAA) with β-cyclodextrin have been investigated in aqueous solution. It has been demonstrated that the naphthalene derivatives form 1:1 complexes when included in the cyclodextrin. A possible structure is proposed, having an axial inclusion of the naphthalene derivatives. In the case of the β-CD: NOA complex, the naphthyl moiety is included in the cyclodextrin and the acetic acid group protrudes from the cavity, while NAA is only partially included because of the steric effect of the group in position 1. Association constants of 560±100 M−1 and 100±50 M−1 have been calculated for the β-CD: NOA and β-CD: NAA complexes, making use of the increment in the fluorescene emission produced in the inclusion process.