Kinetics and solvent-dependent thermodynamics of water capture by a fullerene-based hydrophobic nanocavity.

Kinetic and thermodynamic properties of water encapsulation from organic solution by an open-cage [60]fullerene derivative have been investigated. 2D exchange NMR spectroscopy (EXSY) measurements were employed to determine the association and dissociation constants at 300−330 K (ka = 4.3 M−1 × s−1 and kd = 0.42 s−1 at 300 K) in 1,1,2,2-tetrachloroethane-d2 as well as the activation energies (Ea,ass = 27 kJ mol−1, Ea,diss = 50 kJ mol−1). The equilibrium constants and thermodynamic parameters in various solvents (benzene-d6, 1,2-dichlorobenzene-d4, and dimethylsulfoxide-d6) were estimated using 1D-1H NMR spectroscopy. The parameters were dependent on the polarity of the solvent; ΔH depended linearly on the solvent polarity, becoming increasingly unfavorable as polarity increased. Mixtures of polar dimethylsulfoxide-d6 in less polar 1,1,2,2-tetrachloroethane-d2 showed a similar trend.