Kinetics and Solvent-Dependent Thermodynamics of Water Capture by a Fullerene-Based Hydrophobic Nanocavity

Abstract

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 (k(a) = 4.3 M(-1) × s(-1) and k(d) = 0.42 s(-1) at 300 K) in 1,1,2,2-tetrachloroethane-d(2) as well as the activation energies (E(a,ass) = 27 kJ mol(-1), E(a,diss) = 50 kJ mol(-1)). The equilibrium constants and thermodynamic parameters in various solvents (benzene-d(6), 1,2-dichlorobenzene-d(4), and dimethylsulfoxide-d(6)) were estimated using 1D-(1)H 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-d(6) in less polar 1,1,2,2-tetrachloroethane-d(2) showed a similar trend.

Nuclear spin isomers of guest molecules in H 2 @C 60 , H 2 O@C 60 and other endofullerenes

“…One possibility would be to design open cages, or ways of opening closed cages, that would be able to expel enriched para molecules into the surrounding medium to be used as chemical reagents to produce enhancement via PHIP. Indeed, such chemical exchange between endo and exo water molecules has been measured in the NMR spectrum of an open cage fullerene containing water [62]. The direct [63] and muon-catalysed [10] fusion of two deuterium nuclei is nuclear-spindependent.…”

Synchronized On/Off Switching of Four Binding Sites for Water in a Molecular Solomon Link

“…[16,17] In this experiment, we measured the observed rate constants of the forward and reverse reactions (k A and k B ,r espectively; Figure 1) from the intensity of the exchange cross-peaks between 1 and 2 after each addition of D 2 Oa tf ive temperatures (273-303 K). [16,17] In this experiment, we measured the observed rate constants of the forward and reverse reactions (k A and k B ,r espectively; Figure 1) from the intensity of the exchange cross-peaks between 1 and 2 after each addition of D 2 Oa tf ive temperatures (273-303 K).…”

Encapsulation of Formaldehyde and Hydrogen Cyanide in an Open‐Cage Fullerene

“…The filling factor varies depending on the experimental conditions such that the ratio of H 2 O@ 2 decreased to 25 % by heating the toluene solution over molecular sieves, but it reached 85 % when the solution was heated in the presence of trace water. Notably, the water‐inclusion behavior of open‐cage fullerenes was previously shown also depending on the polarity of solvents …”

“…The filling factor varies depending on the experimentalc onditions such that the ratio of H 2 O@2 decreased to 25 %b yheating the toluenes olution over molecular sieves, but it reached 85 %w hen the solution was heated in the presence of trace water.N otably,t he water-inclusion behavioro fo pen-cage fullerenes was previously shown also depending on the polarity of solvents. [28] The elliptic orifice of 2 spans 7.45 a long the major axis and 5.62 a long the minor axis (Figure 3a). This size is large enought ot rap water molecule from wet solvents spontaneously.W ec onsequently studied insertion of small organic substratesi nto the cavity of 2.F ormaldehyde (H 2 C=O) and hydrogen cyanide (HCN) were investigated because they are important precursors to many other materials and chemical compounds, significant considerations for human health,a nd have suitable dimensions for inclusion ( Figure 3b).…”