engleski

Diamantane Alcohols and Hydrophobic Cavities: The (not so) Perfect Match in Water and Structured Organic Solvents

Diamantane derivatives combined with cucurbit[n]urils have received significant attention in the field of supramolecular chemistry due to their outstandingly high complex stability constants, reaching above petamolar values for positively charged diamantane diammonium salts and cucurbit[7]uril in water. On the other hand, their complexation with cyclodextrins has been rarely investigated.2 We have therefore studied temperature and solvent effects on the complexation of diamantane alcohols with cucurbit[7]uril and β-cyclodextrin in water and structured organic solvents (formamide, ethylene glycol) by means of isothermal titration calorimetry and NMR spectroscopy. The complexes of apical derivatives with CB7 in water were the most stable products (log K > 7), whereas the complexation of 4-DiaOH with β-CD was the most favorable in formamide. For most of the studied host-guest systems a significant temperature dependence of ΔrH° and ΔrS° was observed, which resulted in an almost complete enthalpy-entropy compensation. For these systems complexation thermodynamics was 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 were in accord with the thermodynamic studies and have revealed an interesting difference in complex formation kinetics between cucurbit[7]uril and β-cyclodextrin hosts.

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

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