Inclusion of menadione with cyclodextrins studied by calorimetry and spectroscopic methods

Complex formation of menadione with α ‐, hydroxypropyl α ‐, β ‐, hydroxypropyl‐ β ‐, methyl‐ β ‐ and hydroxypropyl‐ γ cyclodextrins in aqueous solution at 298.15 K was studied by using isothermal titration calorimetry, 1 H NMR, and UV–vis spectrophotometry. The experimental data indicated the partial insertion of menadione into macrocyclic cavity upon formation of two alternative types of 1:1 inclusion complexes, whose thermodynamic parameters ( K , Δ c G 0 , Δ c H 0 , and Δ c S 0 ) were calculated. The influence of host size on the complex formation process was analyzed. β ‐Cyclodextrin and its hydroxypropylated and methylated derivatives were found more effective binders towards menadione than α ‐ and γ ‐cyclodextrins. Copyright © 2007 John Wiley & Sons, Ltd.