Host-guest affinity

The work of Kaifer and colleagues [82a-c] and other researchers [83a,b] on different ferrocene derivatives complexed with jff-CD illustrates a similar behavior the monoelectronic oxidation drastically lowers the host guest affinity (see Scheme 3). 

Fig. 1 Free-energy diagram relating the pertinent energy quantities to the thermodynamic selectivity of three competing guest species. The host-guest complexes are formed according to their respective host-guest affinities represented by free energies of association AG°. Preferential binding is expressed as AAC° [e.g., AAG° = AG°(A)-AG°(0].

Fig. 11.6 The SC24/halide system. (Figure adapted from Lybrand T P, ] A McCammon and G Wipff 1986. Theoretical Calculation of Relative Binding Affinity in Host-Guest Systems. Proceedings of the National Al adeniy of Sciences USA 83 833-835.)...

Materials with uniform pore structures offer a wide range of applications, including catalysis, adsorption, and separation. These materials have the benefit ofboth specific pore systems and intrinsic chemical properties [1-3]. The pores in the materials are able to host guest species and provide a pathway for molecule transportation. The skeletal pore walls provide an active and/or affinity surface to associate with guest molecules. According to the International Union of Pure and Applied Chemistry (IUPAC), porous materials can be classified into three main categories based on the diameters of their pores, that is, microporous, mesoporous, and macroporous... 

As mPE oligomers become longer, the aspect ratio of the helical cavity also increases, such that a rodlike shape complements the cavity better than a spherical shape. To take advantage of this change in aspect ratio a chiral, rodlike piperazine guest (40) was synthesized [58]. The affinity of a host-guest com-... 

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,... 

The high affinity of ammonium cations for tetra-bridged phosphorus(IV) P=0 cavitands was used to complex bis-ammonium guests. The highly insoluble NjAT-dimethyl-bipyridinium dication [paraquat " ] was readily dissolved in chloroform solution in presence of 12b in a 2 1 host-guest ratio. 

Houk KN, Leach AG, Kim SP, Zhang X. Binding affinities of host-guest, protein-ligand, and protein-transition-state complexes. Angew Chem Int Ed 2003 42 4872-4897. 

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