6019 Figure 7. Iz9Xe CP/MAS spectrum (a) same sample as described in Figure 6b, and (b) same sample as described in Figure 6c.both singly and doubly occupied by xenon are indicated.13C NMR spectra for these two samples and for samples recrystallized from octane and dodecane (empty host lattice) are shown in Figure 6 (parts a-c). The CIS methyl carbon appears to be especially sensitive to the presence or absence of guest or to the nature of the guest. This is thought to originate in the flexiblity of the ring to which the CIS methyl is attached. The line marked C18 in Figure 6a corresponds to the empty host lattice. C l i and CI8" then correspond to cages filled or half-filled with xenon, and C I F corresponds to cages filled with octane. The C19 line also is sensitive to the presence of octane. This appears to be the general case for guests occupying the neck of the cage.The lines due to C13 and C15 also show some sensitivity to the presence of guest molecules. The shift of these two carbons, being ortho to the phenolic hydroxyl group, is sensitive to the torsional angle of the O H group with respect to the plane of the aromatic ring. The torsional angle may well change depending on the cage content. Indeed, for the empty host lattice (Figure 6a) there appears to be some structure on the C1,, C15 lines and CI8 as well.These features suggest the presence of some disorder in the empty lattice, related to rotation or movement of flexible parts of the host lattice molecules so as to partially occupy the empty cage space.The lines due to enclathrated octane, labeled 1-4 in Figure 6d occur at 13.2, 19.4, 28.2, and 23.7 ppm. These positions are quite different from those measured in solution 13.9, 22.9, 32.2, and 29.5 ppm.26 This can be explained by the fact that octane in the Dianin's compound cage is not in the extended all-trans configuration. X-ray diffraction has shown that the end methyl group of enclathrated n-heptanol, a molecule of similar length as octane, is gauche with respect to the C4 methylene group. This conformer is considerably shorter than the all-trans form which cannot fit in the Dianin's compound cage. The same must be true for octane: rotation of the end methyl groups by 120' about the C2-C3 bond allows the incorporation of octane in the clathrate cage.The presence of both xenon and octane as guests gives rise to a small shift in the octane carbon resonances, visible mainly as line broadening except for C4 where two lines are partially resolved.Evidently the presence of two guests causes short-range disorder not only for the host lattice but also for guests in neighboring cages.It is also clear from the I3C and Iz9Xe spectra that in no case is there evidence for clustering; i.e., cages with two Xe atoms per cage are not favored over cages containing a single Xe atom. One cannot expect exact statistical distributions of empty, half full, and completely full cages, as the samples were not prepared under equilibrium conditions. Supplementary Material Available:Tables of atomic parameters and anisotro...

The nature of the (Na–DB30C10)+ complex has been studied by 23Na NMR in four non‐aqueous solvents: nitromethane (NM), acetonitrile (AN), acetone (AC) and pyridine (PY). The equilibrium constant of formation (Kf) of (Na‐DB30C10)+ in AC, AN and PY was determined at 300 K: log Kf = 3·9 ± 0·3, 3·4 ± 0·5 and 3·0 ± 0·1, respectively. In cases such as in pyridine, where exact values of the rate constants for the chemical exchange could not be calculated, limiting values were determined giving k−1 (the rate constant for complex dissociation) > 6·6 × 10−4 s−1 and kc (the rate constant for the formation of the complex) > 5 × 107 l mol−1 s−1. Evidence was found for the formation of a 2 : 1 (Na2–DB30C10)+2 complex in nitromethane. It has been previously shown that for (Na–DB24C8)+ the first coordination sphere of Na+ is exclusively filled by the oxygens of the crown ether, whereas for (Na–DB18C6)+ there is participation of at least one solvent molecule. The first coordination sphere of Na+ in (Na–DB30C10)+ consists of one or several molecules of solvent in addition to a number of oxygens from the crown ether. The soft wrapping of the Na+ by DB30C10 is in constrast with the hard wrapping of Na+ by DB24C8 and of K+ by DB30C10.

ChemInform Abstract In propylene carbonate, acetonitrile, Py, and acetone the Na cation exchanges between solvated and 1:1 complexed sites in the presence of 18-crown-6. Two mechanisms of exchange are shown to be in competition in the first three solvents. In acetone the exchange mechanism is almost exclusively unimolecular. Kinetic parameters are determined.