Shape guest

The metathesis reaction of the imine bond was also able to dynamically select for oligomers that form the most stable host-guest complex [88]. It has been shown that rodlike and dumbbell-shaped guests have a higher affinity and specificity for oligomers of 20-22 repeat units [58,61 ]. Imine starter sequences 60,61a, and 61b, which can potentially form 16- (63a), 22- (63b), and 28-mers (63c) as well as smaller molecular weight (MW) materials (62a and 62b), were chosen as starter sequences for an imine ligation experiment (Fig. 37). When equiUbrated in chloroform the product distribution of 63a-c was close to 1 1 1,... 

Removal of reversibly adsorbed (physisorbed) cyanine-dye molecules, D, led to skeletonized, SA silane monolayers having pinholes in the shape of D (Fig. 18) [185]. Such pinholes can, in turn, serve as templates for similarly shaped guest molecules. This approach opens the door for molecular recognition and device construction based on molecular recognition [186-190]. The idea relies upon the construction of a well-packed, SA monolayer from a mixture of OTS molecules and a solvent removable guest species. Removal of the guest molecules leaves pinholes with precise dimensions which only accept molecules with... 

Grotzfeld, R. M., Branda, N., Rebek, J., Reversible encapsulation of disc-shaped guests by a synthetic, self-assembled host. Science 1996, 271, 487 489. 

Figure 3.16 Imine oligomers used as building blocks and rod-shaped guest used to amplify a linear receptor.

The incorporation of similarly shaped guest components into the lattice of a host component can be quantified by a distribution coefficient, keq, equal to the ratio of the impurity content in the solid phase, Ximp.s. to that in the liquid phase, Ximp.i (with % in mol fractions), supposing both phases are in equilibrium at a given temperature. The so-defined coefficient is called thermodynamic distribution (or segregation) coefficient (Equation 7.2) ... 

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