engleski

Diamantanes are a hydrophobic cavity's best friend: the role of solvent structuring in complex stability

Diamantane derivatives are excellent guests for cucurbiturils in aqueous solutions, forming complexes with stability constants reaching above petamolar values. On the other hand, their complexation with cyclodextrins has been scarcely explored. We therefore studied temperature and solvent effects on the complexation of diamantane alcohols with cucurbit[7]uril, β- and γ- cyclodextrin by means of isothermal titration calorimetry and NMR spectroscopy. The stability constant among all investigated complexes was by far the highest in the case of the diol derivate with cucurbit[7]uril in water. A pronounced temperature dependence of ΔrH° and ΔrS°, resulting in an almost complete enthalpy- entropy compensation, was observed for most studied host-guest systems. The corresponding complexation thermodynamics were in line with the classical rationale of the solvophobic effect at lower temperatures, and the non- classical explanation at higher ones. The results of 1H NMR titrations and ROESY experiments were in line with the thermodynamic studies and have revealed an interesting difference in complex formation kinetics between cucurbit[7]uril and β-cyclodextrin.

Hydrophobic effect ; solvophobic effect ; inclusion complex ; complexation thermodynamics ; cyclodextrins ; cucurbit[7]uril ; mannoconjugates

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