Inclusion complexes of nabumetone with beta-cyclodextrins: thermodynamics and molecular modelling studies. Influence of sodium perchlorate

Fluorescence, H-1-NMR and molecular mechanics have been used to study the i nclusion complexes of nabumetone (4,6-methoxy-2-naphthyl-butan-2-one; NAB) with beta -cyclodextrin (beta -CD), randomly methylated-beta (M beta -CD) a nd hydroxypropyl-beta -cyclodextrins (HP beta -CD). The emission spectrum o f NAB shows a maximum whose fluorescence intensity increases with the diffe rent beta -CDs growing concentrations, This phenomenon allows calculation o f the stability constants at 15, 25, 37 and 45 degreesC. The thermodynamic parameters DeltaH degrees and DeltaS degrees for the inclusion process were obtained from the temperature dependence of the stability constants. Molec ular mechanics calculations, together with proton NMR measurements, for the complex with beta -CD prove that the complex can be formed by penetration through any of the rims, with the naphthalene nucleus included and the subs tituents outside the cavity. The influence of NaClO4 in the aforementioned complexes has been analysed by spectrofluorimetric measurements. It has bee n found that the stability constants for the complexes decrease with die sa lt concentration; the causes are discussed. Copyright (C) 2001 John Wiley & Sons, Ltd.