Energy host -» guest

Badertscher, M., Welti, M., Portmann. P., and Pretsch, E. Calculation of Interaction Energies in Host-Guest Systems. 136, 17-80 (1986). 

Macrocyclic receptors made up of two, four or six zinc porphyrins covalently connected have been used as hosts for di- and tetrapyridyl porphyrins, and the association constants are in the range 105-106 M-1, reflecting the cooperative multipoint interactions (84-86). These host-guest complexes have well-defined structures, like Lindsey s wheel and spoke architecture (70, Fig. 27a), and have been used to study energy and electron transfer between the chromophores. A similar host-guest complex (71, Fig. 27b) was reported by Slone and Hupp (87), but in this case the host was itself a supramolecular structure. Four 5,15-dipyridyl zinc porphyrins coordinated to four rhenium complexes form the walls of a macrocyclic molecular square. This host binds meso-tetrapyridyl and 5,15-dipyridyl porphyrins with association constants of 4 x 107 M-1 and 3 x 106 M-1 respectively. 

Acceptor guest molecules such as quinone, TCNQ, or toluene can be accommodated in the flexible cavity of face-to-face bismacrocyclic Nin complexes (656). The host-guest interactions decrease the energy gap between the LUMO of the organic acceptors and the HOMO of the complex donors.1664... 

In ultrasonic relaxation measurements perturbation of an equilibrium is achieved by passing a sound wave through a solution, resulting in periodic variations in pressure and temperature.40,41 If a system in chemical equilibrium has a non-zero value of AH° or AV° then it can be cyclically perturbed by the sound wave. The system cannot react to a sound wave with a frequency that is faster than the rates of equilibration of the system, and in this case only classical sound absorption due to frictional effects occurs. When the rate for the host-guest equilibration is faster than the frequency of the sound wave the system re-equilibrates during the cyclic variation of the sound wave with the net result of an absorption of energy from the sound wave to supply heat to the reaction (Fig. 4). 

In host-guest systems based on electron donor/ acceptor interactions, association/dissociation can be driven by redox processes so that it is possible to design electrochemical switches than can be used to control energy- and electron-transfer processes. 

Host) (Guest) Poor energy transfer Efficient energy transfer... 

Moreover, these dendrimers proved to be good hosts for anionic dye molecules. Films prepared from these host-guest complexes showed efficient ( > 90%) energy transfer from the OPV units to the encapsulated dye molecules... 

The maximum observed free energy difference between two enantiomeric host-guest complexes in which one 1,1 -dinaphthyl element is the only source of chirality in the crown ether is about 0.3 kcal mol-1. Improvement of the free energy difference can be achieved by introduction of two such elements. Unfortunately crown ethers with three 1,1 -dinaphthyl groups did not form complexes with primary ammonium salts (de Jong et al., 1975). The dilocular chiral crown ether [294] forms complexes of different stability with R- and 5-cr-phenylethylammonium hexafluorophosphate. The (J )-J J -[284] complex was the more stable by 0.3 kcal mol-1 at 0°C (EDC value 1.77) (Kyba et al., 1973b). Crown ether [284] also discriminates between the two enantiomers of phenylglycine methyl ester hexafluorophosphate and valine methyl ester... 

Excitation energy transfer in dendritic host-guest donor-acceptor systems. Chem Phys Chem 3 1005-1013... 

The host-guest interaction of manganese(II) with a range of ferrocene-containing species, which included the dithia derivative (219), has been investigated in acetonitrile. Complexation gave rise to a bathochromic shift of the lowest-energy ferrocene-centered d-d transitions. 

CL Copper, MJ Sepaniak. Cyclodextrin-modified micellar electrokinetic capillary chromatography separations of benzopyrene isomers. Correlation with computationally derived host-guest energies. Anal Chem 66 147—154, 1994. 

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