Guest-host mechanism

The use of low molar mass thermotropic nematic liquid crystals to orient photoconductive chromophores by a guest-host mechanism. 

The Use of Low Molar Mass Thermotropic Liquid Crystals to Orient Photoconductive Chromophores by a Guest-Host Mechanism ... 

Supramolecular chemistry takes into consideration the weak and reversible non-covalent interactions between molecules, which include H-bond-ing, metal coordination, hydrophobic forces, van der Waals forces, n—n interactions, and covers different research fields, for example, molecular recognition, host-guest chemistry, mechanically interlocked and nanochemistry. 

I. Tanaka, Y. Tabata, and S. Tokito, Energy-transfer and light-emission mechanism of blue phosphorescent molecules in guest-host systems, Chem. Phys. Lett., 400 86-89 (2004). 

Fig. 9.—Schematic Diagram of the Two Hosts-Two Guests Inclusion Mechanism Shown for the Tropaeolin 000 No. 2-Gamma Cyclodextrin System.

Pluth, M.D. and Raymond, K.N. (2007) Reversible guest exchange mechanisms in supramolecular host-guest assemblies. Chem. Soc. Rev, 36 (2), 161-171. 

Leung, D.H., Bergman, R.G. and Raymond, K.N. (2006) Scope and mechanism of the C—H bond activation reactivity within a supramolecular host by an iridium guest A stepwise ion pair guest dissociation mechanism. J. Am. Chem. Soc., 128 (30), 9781-9797. 

In the case of LC polymers, the polymeric matrix performs as a host, while the guest is a dye, whose molecules are elongated in shape, and the absorption oscillator is parallel (or perpendicular) to the big axis of the molecule 65,163-165>. The experiments investigating guest-host effect in nematic polymers with dichroic dyes covalently attached to the polymer 163) (type I) and mechanically incorporated65) (type II) reveal the possibility to obtain regulated color indicators (see page 60). 

The application of ab initio quantum mechanical calculations to determine the guest-host intermolecular potential parameters was performed in a parallel effort by the group of Sandler et al. (Klauda and Sandler, 2000, 2003) and the groups of Trout and Tester et al. (Anderson et al., 2004, 2005). Klauda and Sandler (2005) extended their model to predict in-place hydrate formation in nature. 

Supramolecular modification of carbene chemistry may be achieved, to some degree, by forming guest host ICs of nitrogenous carbene precursors with CyDs and FAU zeolites. The results of these reactions should help physical organic chemists better understand the detailed mechanisms by which carbenes decay. 

Molecular dynamics employs Newtonian mechanics to model the time evolution of the system. The positions, velocities, and accelerations of each atom in the system are calculated from the force-field potential. Newtonian mechanics describes the relationship between the potential felt by each atom, the forces on each atom, and, therefore, the accelerations, velocities, and positions of each atom at each time step of the simulation. From the time evolution of the system, we can calculate many properties of the system. In this chapter, we describe the history, methods, and results of the work on the electric field poling of nonlinear optical polymeric guest-host systems. 

The major difference between these three categories, irrespective of the type of intermolecular attractions, is the extent of inclusion. Type I has no inclusion complexation, Type II has partial inclusion and Type III uses inclusion complexation as the "primary mechanism." For this review I shall create a greater line of demarcation than Wainer between Type II and Type III phases. Here Type III shall be considered to be exclusively guest-host complexes as found in crown ethers, cyclodextrins and related systems, whereas Type II uses only partial guest-host complexation. 

Koen de Vries, Coussens and Meier likewise found that a combined molecular mechanics and molecular dynamics approach is a valuable tool for rationalizing qualitative gas chromatographic trends [69]. Experimentally they evaluated the thermodynamic parameters (AG, AAG, AH, AAH, etc.) for guest-host complexation of six analytes on a variety of derivatized CD columns. Their interpretation of the computational results is that one enantiomer fits the CD cavity better than the other resulting in a larger Interaction energy and greater loss of mobility. 

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