Dimers tennis ball units

Coordination interactions are not the only way to use self-assembly to produce closed, capsular systems capable of binding guest species in solution. Work by Julius Rebek Jr (Scripps, USA)43 has shown that multiple hydrogen-bonding interactions, because of their relatively weak, but directional, nature, are ideal for the strict self-assembly of closed spherical molecules and capsules. For example, component 10.49 consists of two intrinsically curved diphenylglycoluril units linked by a durene-based (1,2,4,5-tetramethyl benzene-based) spacer. In both solution and in the solid state, 10.49 self-assembles spontaneously to produce the tennis ball-shaped dimer (10.49)2 shown in Figure 10.43. The formation of the dimer has been observed by ... 

Rebek has conducted extensive studies on curve-shaped molecules that self-assemble to form homodimers, in the form of molecular capsules, in both solution and the solid state.34 In particular, Valdes et al. have demonstrated the ability of two glycoluril units separated by a benzene spacer to self-assemble in the solid state via eight N-H O hydrogen bonds to form a capsule with a structure that conforms to a tennis ball (Fig. 16).34a A disordered guest, identified as probably being methanol, occupied the interior. A related dimer based on an ethylene spacer was also prepared and shown to accommodate a guest, also identified as probably being methanol, in the crystalline state.34b... 

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