Non-resonance charge transfer

Let a crossing of diabatic surfaces of potential energy occur in a certain point R0. Taking into account only the linear expansion term of the difference between the energies of the diabatic states near the crossing point (the Landau-Zener model) 

It is seen in these reasonings that charge transfer occurs primarily with a size of about vrr (vTl dmidR )112 near the crossing point. This size must be small compared with the characteristic atom size, otherwise the initial supposition that V = const, is not satisfied. 

A typical example of the tunnel non-resonance charge transfer is charge transfer in collisions of the ions H and H+ 

The diabatic term of the H + H+ initial state decreases with decreasing internuclear distance because of the Coulomb and polarizing interactions 

The example considered shows that, due to electron tunneling at large distances, the non-resonance (as well as resonance) charge transfer in the gas phase can occur at distances which substantially exceed the size of the colliding particles themselves. 

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There are three types of simple charge transfer (a) resonant charge transfer, (b) accidental resonant charge transfer and (c) non-resonant charge transfer. 

Non-Resonant Charge Transfer Processes and Ion-Molecular Chemical Reactions of Positive and Negative Ions... 

The 0-to-N electron transfer is an example of non-resonant charge exchange with a 1-eV energy defect ... 

Irradiation of a non-polar solvent (RH) generates an electron— hole pair (RH+, e ), which can transfer their charges to other molecules within the spur through reaction. These solvent holes can diffuse within a spur in two ways (1) by molecular diffusion and (2) by molecular resonant charge transfer as... 

The ortho effect may consist of several components. The normal electronic effect may receive contributions from inductive and resonance factors, just as with tneta and para substituents. There may also be a proximity or field electronic effect that operates directly between the substituent and the reaction site. In addition there may exist a true steric effect, as a result of the space-filling nature of the substituent (itself ultimately an electronic effect). Finally it is possible that non-covalent interactions, such as hydrogen bonding or charge transfer, may take place. The role of the solvent in both the initial state and the transition state may be different in the presence of ortho substitution. Many attempts have been made to separate these several effects. For example. Farthing and Nam defined an ortho substituent constant in the usual way by = log (K/K ) for the ionization of benzoic acids, postulating that includes both electronic and steric components. They assumed that the electronic portion of the ortho effect is identical to the para effect, writing CTe = o-p, and that the steric component is equal to the difference between the total effect and the electronic effect, or cts = cr — cte- They then used a multiple LFER to correlate data for orrAo-substituted reactants. 

As it concerns the band in the UV region (at 315 nm in the present case), Benesi and Hildebrand [5] assigned this absorption to a charge-transfer transition, where the phenyl ring acts as an electron donor (D) and the iodine as an electron acceptor. The interaction can be described in resonance terms as D-I2 <-> D+I2", the band being assigned to the transition from the ground non polar state to the excited polar state. 

A typical cyclic voltammetric trace for the anodic oxidation of the fluorenyl anion 2 at platinum is shown in Figure 1. The oxidation potential for this and several other resonance stabilized carbanions lies conveniently within the band gap of n-type Ti02 in the non-aqueous solvents, and hence in a range susceptible to photoinduced charge transfer. Furthermore, dimeric products (e. g., bifluorenyl) can be isolated in good yield (55-80%) after a one Faraday/mole controlled potential (+1.0 eV vs Ag quasireference) oxidation at platinum. 

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