Interactions charge transfer

In water, however, the above contribution from EDA interactions tends to be over-ridden by solvation effects. In this solvent, solvophobic forces (see below) can provide a very favourable contribution to the free energy of association of host and guest. 

In another application of the same principle, an electron donor/ electron acceptor pair of disk-shaped groups were attached through a flexible atom chain [170]. When incorporated into columns of discotic molecules containing only the electron donor group, the tethered donor/acceptor molecule was able to influence the motions of columns of donor molecules in their D phases [170]. 

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NMR signals of the amino acid ligand that are induced by the ring current of the diamine ligand" ". From the temperature dependence of the stability constants of a number of ternary palladium complexes involving dipeptides and aromatic amines, the arene - arene interaction enthalpies and entropies have been determined" ". It turned out that the interaction is generally enthalpy-driven and counteracted by entropy. Yamauchi et al. hold a charge transfer interaction responsible for this effect. 

TT-stacking and charge-transfer interaction between aromatic residues in the receptor and delocalized regions of the substrate van der Waals attraction between hydrophobic regions on the two components... 

These results indicate that a complete electron transfer is brought about from the charge-transfer interaction and can be summarized [62] as follows ... 

Recently, the quaternized poly-4-vinylpyridine, 50-54 (QPVP) was found to be an electron acceptor in the charge-transfer interactions 104 Ishiwatari et al.105) studied alkaline hydrolyses of p-nitrophenyl-3-indoleacetate 58 (p-NPIA) and N-(indole-3-acryloyl) imidazole 59 (IAI) (electron donor) in the presence of QPVP. The fcobs vs. polyelectrolyte concentration plots are shown in Fig. 12. As is seen in... 

The radical anions of dialkyl sulfoxides (or sulfones) may be obtained by direct capture of electron during y-irradiation. It was shown that electron capture by several electron acceptors in the solid state gave anion adducts 27. It was concluded276 that these species are not properly described as radical anions but are genuine radicals which, formed in a solid state cavity, are unable to leave the site of the anions and exhibit a weak charge-transfer interaction which does not modify their conformation or reactivity appreciably, but only their ESR spectra. For hexadeuteriodimethyl sulfoxide in the solid state, electron capture gave this kind of adduct 278,28 (2H isotopic coupling 2.97 G is less than 3.58 G normally found for -CD3). 

The generally observed endo preference has been justified by secondary orbital interactions, [17e, 42,43] by inductive or charge-transfer interactions [44] and by the geometrical overlap relationship of the n orbitals at the primary centers [45]. 

C20-0102. Blue copper proteins are blue when they contain Cu but colorless as Cu compounds. The color comes from an interaction in which a photon causes an electron to transfer from a sulfur lone pair on a cysteine iigand to the copper center. Why does this charge transfer interaction occur for Cu but not Cu+ ... 

More recently, Kim et al. synthesized dendritic [n] pseudorotaxane based on the stable charge-transfer complex formation inside cucurbit[8]uril (CB[8j) (Fig. 17) [59]. Reaction of triply branched molecule 47 containing an electron deficient bipyridinium unit on each branch, and three equiv of CB[8] forms branched [4] pseudorotaxane 48 which has been characterized by NMR and ESI mass spectrometry. Addition of three equivalents of electron-rich dihydrox-ynaphthalene 49 produces branched [4]rotaxane 50, which is stabilized by charge-transfer interactions between the bipyridinium unit and dihydroxy-naphthalene inside CB[8]. No dethreading of CB[8] is observed in solution. Reaction of [4] pseudorotaxane 48 with three equiv of triply branched molecule 51 having an electron donor unit on one arm and CB[6] threaded on a diaminobutane unit on each of two remaining arms produced dendritic [ 10] pseudorotaxane 52 which may be considered to be a second generation dendritic pseudorotaxane. 

Robel, I., Bunker, B. A. and Kamat, P. V. (2005) Single-walled carbon nanotube-CdS nanocomposites as light-harvesting assemblies Photoinduced charge-transfer interactions. Adv. Mater., 17, 2458-22463. 

In the Born equation, the ion solvent interaction energy is determined only by one physical parameter of the solvent, i.e., the dielectric constant. However, since actual ion-solvent interactions include specific interactions such as the charge-transfer interaction or hydrogen bonds, it is natural to think that the Born equation should be insufficient. It is well known that the difference in the behavior of an ion in different solvents is not often elucidated in terms of the dielectric constant. 

The range of structural alternatives explored by valency-deficient carbon species and the subtle interplay of substituents is remarkable. Scheme 7.6 (ORTEP adapted from reference 31) illustrates an example of an X-ray structure clearly describing a localized [C-H C+] carbenium ion (A) where a symmetric bridging structure [C-H-C] + (B) could have been assumed. In this case it is proposed that a charge-transfer interaction between the resonance delocalized cation and the adjacent electron-rich carbazol moiety may be responsible for the stabilization of the localized form over the three-center, two-electron (3c-2e) bridging structure. 

An HSAB analysis of singlet carbene reactivity based on B3LYP/6-31G computations has calculated the extent of charge transfer for substituted alkenes,122 and the results are summarized in Figure 10.3 The trends are as anticipated for changes in structure of both the carbene and alkene. The charge transfer interactions are consistent with HOMO-LUMO interactions between the carbene and alkene. Similarly, a correlation was found for the global electrophilicity parameter, co, and the ANmax parameters (see Topic 1.5, Part A for definition of these DFT-based parameters).123... 

As described most elegantly elsewhere in this volume, the halogen bond is an intermolecular, charge-transfer interaction between a Lewis base and an electron-deficient halogen. Other chapters that accompany this chart its use in, for example, supramolecular chemistry, molecular conductors and coordination chemistry. In this chapter, a much more recent application of halogen bonding is described, namely in the realisation of liquid-crystalline materials. 

This quantity represents the energy of the multiple-site charge-transfer interaction which will later play an important role in the theory of stereoselection. It is to be remarked that, although any MO may involve an arbitrary constant of which the absolute value is unity, the value of the numerator in each term of the right side of this equation is always definite. 

Eq. (3.25) stands for Mulliken s overlap and orientation principle. The charge-transfer interaction takes place according to the way in which the overlap of HO of the donor and LU of the acceptor becomes maximum. Particularly, the single-site interaction will occur at the position of the greatest HO density of the donor and at the position of the greatest LU density of the acceptor, as is seen from Eq. (3.26). In such cases the particular role of the frontier orbitals is evident. 

These circumstances become clear when we consider several common examples. The Diels-Alder addition of ethylene and butadiene is taken as the first and simplest example. Fig. 4.2a indicates the nodal property of HO and LU of ethylene and butadiene and the mode of charge transfer interaction. The ethylene HO is bonding while LU is antibonding. The... 

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