Charge transfer contributions

A charge transfer contribution is often identified in perturbative descriptions of intennolecular forces. This, however, is not a new effect but a part of the short-range induction energy. It is possible to separate the charge transfer part from the rest of the induction energy [80]. It turns out to be relatively small and often negligible. Stone [28] has explained clearly how charge transfer has often been a source of confusion and error. 

The 260 nm band of chiral thiiranes is optically active and a Cotton effect is observed R) (+)-methylthiirane shows a negative Cotton effect at ca. 250 nm followed by a positive effect below 200 nm. An MO analysis indicates that charge transfer contributions are most important in determining the optical activity of the transition (81JCS(F2)503). The... 

In a recent paper. Mo and Gao [5] used a sophisticated computational method [block-localized wave function energy decomposition (BLW-ED)] to decompose the total interaction energy between two prototypical ionic systems, acetate and meth-ylammonium ions, and water into permanent electrostatic (including Pauli exclusion), electronic polarization and charge-transfer contributions. Furthermore, the use of quantum mechanics also enabled them to account for the charge flow between the species involved in the interaction. Their calculations (Table 12.2) demonstrated that the permanent electrostatic interaction energy dominates solute-solvent interactions, as expected in the presence of ion species (76.1 and 84.6% for acetate and methylammonium ions, respectively) and showed the active involvement of solvent molecules in the interaction, even with a small but evident flow of electrons (Eig. 12.3). Evidently, by changing the solvent, different results could be obtained. 

Piquemal J-P, Marquez A, Parisel O, Giessner-Prettre C (2005) A CSOV Study of the difference between HF and DFT Intermolecular Interaction Energy Values the importance of the charge transfer contribution. J Comput Chem 26 1052... 

Gresh N, Claverie P, Pullman A (1986) Intermolecular interactions Elaboration on an additive procedure including an explicit charge-transfer contribution. Int J Quant Chem 29 101... 

J >> D. The triplet characteristics will be affected by a charge transfer contribution to the triplet electronic state. It is predicted that this will reduce the values of D and E, and increase the rate constants of decay from the triplet sublevels (5,8,24). 

The result of an energy decomposition analysis performed for this complex was also unusual. In contrast to numerous dihydrogen-bonded systems with significant predominance of the electrostatic interaction, the dihydrogen-bonded dimer (LiH H20)2 has shown the charge transfer contribution to exceed the electrostatic energy —125.30 versus —81.40 kcal/mol, respectively. 

Table VI. Charge transfer contributions to the three-body interaction energy at the MP3 and MP4 correlated levels for the studied He-clusters (in jiH, see Figure I. for notations, numbering of atoms are given from left to right))...

Additional information has been obtained from single crystal, polarized optical and ESR spectroscopic studies924 on poplar plastocyanin, which have allowed a correlation of the electronic structure of the blue copper active site with its geometric structure. In summary, the three dominant absorption bands at 13 350, 16 490 and 17 870 cm-1 were assigned to CysS- Cu (d 2-,2 charge-transfer transitions. The methionine makes only a small contribution, due to the long Cu—S(Met) bond (2.9 A) and the poor overlap of the methionine sulfur orbitals with the dx y orbital of copper. Histidine-Cu charge transfer contributes to the weaker absorptions at 21 390 and... 

The solvent effect in the photoreaction of 255c clearly showed that the formation of 257c strongly correlates with the polarity of solvent, but the formation of 256c did not [297], From these facts, the formation of 3,4-adducts 257 is explained by the charge-transfer contribution of the singlet exciplex, whereas the 1,2-adducts 256 are formed via normal exciplex with less charge-transfer na-... 

The experimental data on crystal fields have been summarized [31] and shown that the overlap and covalency (charge transfer) contribute to a significant extent to the crystal field parameters when n = 4 and 6. Analysis of the data on PrCb showed that the experimental parameters for A < (r6) and A (r4) are in good agreement with the sum of the calculated electrostatic and covalent contributions. The values for (r2) showed poor agreement. 

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