Inclusion complex formation between host-guest

Host-Guest Inclusion Complex Formation between Surfactant Stilbenes and Amylose... 

Fluorescence correlation spectroscopy analyses the temporal fluctuations of the fluorescence intensity by means of an autocorrelation function from which translational and rotational diffusion coefficients, flow rates and rate constants of chemical processes of single molecules can be determined. For example, the dynamics of complex formation between /3-cyclodextrin as a host for guest molecules was investigated with singlemolecule sensitivity, which revealed that the formation of an encounter complex is followed by a unimolecular inclusion reaction as the rate-limiting step.263... 

The Rf values of a guest molecule decrease to a considerable extent, thus helping in identification of the complex formation between guest and host molecules [55]. Inclusion complexation is a reversible process, thus it may separate completely in guest and host molecules during the chromatographic process, and individual spots of the guest and host molecules are found on the TLC plate. 

Fig. 1. Schematic representation of a receptor—substrate (host—guest) complex involving cavity inclusion of the substrate and the formation of different types of weak supramolecular interactions between receptor (hatched) and substrate (dotted).

Recently, it has become clear to the author that cyclodextrin is one of the promising hosts for macromolecular recognition, with the finding that the cylindrical channel formed when it is stacked in a linear row is able to accommodate one or more long-chain guests. Thus, he and his coworkers launched a series of experiments to explore the formation of inclusion complexes between... 

In order to determine the mechanism of complex-formation, however, kinetic methods must be used. Consider one host-two guests complex-ation. The two possible mechanisms are dimerization of the guest outside the cyclodextrin cavity followed by inclusion, and dimerization within the cyclodextrin cavity. Equilibrium measurements alone cannot distinguish between these two possibilities. The same is the case for 2 2 complex-formation, where a larger number of possible mechanisms exist. 

The formation of a one host-two guests inclusion-complex could proceed by way of two main mechanisms (/) dimerization of the guest, followed by inclusion and (2) stepwise inclusion of two guest molecules. In order to distinguish between these two possibilities, several temperature-jump relaxation kinetic studies have been carried us-... 

The driving forces of complex formation were thought to be the geometric compatibility or fit and intermolecular interaction between hosts and guests. It has been reported that many linear polymeric guests could form inclusion complexes with CDs resulting in main-chain pseudopolyrotaxanes. When the polymers were added into the CD solutions and then sonicated, crystalline inclusion complexes precipitated. As the result of X- ray diffraction study, all crystalline inclusion complexes between CDs and polymeric guests are columnar in structure [27,43],... 

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