Electronic interaction intramolecular

Asymmetric Diels-Alder reactions. Unlike methyl crotonate, which is a weak dienophile, chiral (E)-crotonyl oxazolidinones when activated by a dialkylaluminum chloride (1 equiv.) are highly reactive and diastereoselective dienophiles. For this purpose, the unsaturated imides formed from oxazolidinones (Xp) derived from (S)-phenylalanol show consistently higher diastereoselectivity than those derived from (S)-valinol or (IS, 2R)-norephedrine. The effect of the phenyl group is attributed in part at least to an electronic interaction of the aromatic ring. The reactions of the unsaturated imide 1 shown in equation (I) are typical of reactions of unsaturated N-acyloxazolidinones with cyclic and acyclic dienes. All the Diels-Alder reactions show almost complete endo-selectivity and high diastereoselectivity. Oxazolidinones are useful chiral auxiliaries for intramolecular Diels-Alder... 

The third area of interest in SCS determinations, namely the interpretation of experimental data in terms of changes in the electronic environment of the nuclei, is intrinsically not amenable to the above techniques. Although the field is still in its infancy, one may expect that someday, 3C NMR spectroscopy will rank among those methods that allow one to detect intramolecular electron interactions and proximity effects (520). 

We cite here two examples of triiron complexes which can depict well the possible intramolecular electronic interactions in polymetallic complexes. First of all we take into account that, as discussed in Chapter 2, Section 1.5.1 and Chapter 4, Section 1.3, from the electrochemical viewpoint, the existence of a mutual electronic (through-space or through-bond) interaction in molecules containing two or more redox-active centres leads to the appearance of separate electron transfer processes. There are, however, two main classes of polynuclear molecules ... 

Both of the bisfullerene compounds 19 and 23 undergo the intramolecular [2-1-2] reaction in chloroform and in ODCB, respectively, to give 24 [38] and 25 [41 ] quantitatively under irradiation by visible light. In these newly formed bisfullerene compounds, the electronic interaction between two Cgo cages was found to be greater than that in 19 and 23, as examined by electrochemical measurements, due to the closely fixed geometry. 

Intramolecular interception of an Af-alkoxy-AT-acylnitrenium ion by an aromatic ring results in a spirocyclic species [203], There follows a C-migration (instead of N-migration) to restore aromaticity. This migration is assisted by the stabilization of the incipient carbocation by the resident donor nitrogen atom N-migration would not profit from this favorable electronic interaction. 

At very long separations, for example, transfer to the biphenyl cation radical over 34 A in 1C)2 s, electronic interactions seemed to be propagated by ion states of the solvent (25), although quantum mechanical tunnelling may be important when diffusion is blocked by steric factors or by immobilization of the reagents (26). Perhaps most convincing are Miller and Closs demonstration of intramolecular electron transfer between donor-acceptor pairs separated by a rigid steroid spacer (27, 28). In 1, for example,... 

A series of silyl and disilyl substituted thioketene dimers (2,4-diylidene-1,3-dithietane), including polymers, have been synthesized (33, 34) [117]. HOMO-LUMO calculation by PM3 semi-empirical molecular orbital method predicted an intramolecular CT from the thioketene dimer to the Si-Si bond in disilyl thioketene dimer (33a) and no electronic interaction between the... 

The key to understand the anomalous behaviors in A vC,o is the electron-electron interaction, U, and the electron-phonon interaction, S. In A vCgo, the important interaction as U is the Coulomb repulsion between the flu electrons. The importance of U has been pointed out based on the results of the photoemission experiments [15]. Also, in AxC o, the important interaction as S is the coupling of the tlu electrons to the intramolecular phonons of the CRaman experiments [16], Nevertheless, a complete understanding of the anomalous behaviors in AxCgo has not been established yet. The reason is that the system with the orbital degree of freedom in which both U and S are important has not been known so far [17-20],... 

In this section, a model which gives the basis of the present study is introduced to investigate the electronic properties of A,Cfio [17]. First, the one-electron part of the Hamiltonian, which describes the itinerant motion of the flu electrons in terms of the electron transfer T, is given. Next, the electron-electron interaction U and the electron-phonon interaction S are examined U represents the Coulomb repulsion between the t u electrons and S represents the coupling of the fiu electrons to the intramolecular phonons of the Cdynamical aspect of S is pointed out. 

In our attempts to design functional clusters we have focused on substitution of the heteroanions within the Wells-Dawson structure to create nonconventional Dawson clusters incorporating two pyramidal anions. Our design rationale was based on the idea that such clusters may exhibit unprecedented properties arising from the intramolecular electronic interactions between the encapsulated anions (in this case we aimed to engineer between S S atoms of two encapsulated sulfite ions), thus providing a novel route to manipulate the physical properties of... 

The symbol ( )n denotes one mole of domains of any spin state with n molecules in each domain. Interactions between the domains, irrespective of the spin state, are neglected. The total energy of an individual complex molecule is considered to be composed of electronic and intramolecular vibrational contributions. In terms of the partition functions for these contributions the equilibrium constant K = xhs/O-xhs) may be formulated as... 

The above examples of the unique possibilities of stereochemically fixed aromatic rings in multibridged, multilayered and multistepped hydrocarbon compounds show that these classes of compounds are most appropriate for the study of intramolecular, steric and electronic interactions, from which too little quantitative relations are known. Again, it follows that further synthetic approaches are not only possible, but also necessary for a more accurate differentiation and analysis of the frequently overlapping electronic and steric effects. More progress in this field is sure to be expected, above all when synthetic and spectroscopic chemists, and physicists adhere to interdisciplinary, collaborative work. 

In organic conductors the electron-phonon couplings play a fundamental role. In general, the interaction of the electrons with intramolecular vibrations can be written in the form given by Rice [13] ... 

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