Coulomb stabilization

Dissociative Low-Energy Electron Attachment to the C-S Bond of H3CSCH3 Influenced by Coulomb Stabilization... 

The effects that proximal positively charged groups can have on the DEA process were the primary focus in Ref. [5]. Specifically, we considered the Coulomb stabilization that one or more nearby positive groups (e.g., simulating the protonated Lys sites in the molecule shown in Fig. 1) can have on the nascent a anion. As an example of the effects of Coulomb interactions, in Fig. 3 we show the MeS-SMe neutral and MeS-SMe a anion potentials as in Fig. 2 but calculated in the presence of two +1 charges each 30 or 10 A from the midpoint... 

Figure 3 Energies, as functions of the S-S bond length, of the parent charged polypeptide (top), of ground and excited-Rydberg states localized on the protonated amine side chain, and of the SS CT -attached state in the absence of (upper curve) and in the presence of (lower curve) Coulomb stabilization (appears as Figure 1 in ref. 3s).

A and that is sufficiently Coulomb stabilized by nearby positive charges to render positive its electron binding energy,... 

Of the reactions listed in Table II, the only process that leads to a decrease of the energy of molecular oxygen is the formation of the free superoxide ion, Oj ( — 10.15 kcal/mol). The superoxide ion would therefore be expected to be the dioxygen species most commonly formed on oxide surfaces and in fact it is the species most studied, both in the bulk of various matrices and on surfaces. The other species (Oj and Oj ) are not stable in the gas phase, although they can be stabilized in the solid state (Table I) due to the additional coulombic stabilization from the lattice. 

As mentioned above, the energy levels in Fig. 8 have been estimated from cyclic voltammetric studies and may be slightly in error in that they do not explicitly correct for coulombic stabilization of intermediates such as C-PA-PB -Q 7. If such stabilization were to drop the energy of C-PA-P -Qr below that of C-PA -Pb-Q t, then the formation of the final C+-PA-PB-Q 7 state might be thought of as a single step from C-PA-PB -Q7 in which the porphyrin PA facilitates the transfer via superexchange [8, 26]. As was noted earlier, the accessory bac-teriochlorophyll in the natural reaction center may play a similar role. 

The Type 3 SN2 reaction between Cl- + CH3SHf is interesting because it represents a formal anion-cation recombination through substitution. Because charges are annihilated in forming the transition state, polar solvents will significantly destabilize product formation. Fortunately, the loss in solvation of the two ions is compensated for by electrostatic attractions in bringing the two reactant species into contact. Therefore, the outcome of an SN2 reaction of Type 3 depends on the balance of Coulomb stabilization and solvent destabilization. The reactant and product diabatic states are defined as follows in MOVB theory ... 

Moving toward the left of Fignre 3.10, the potential energy of the system decreases rapidly dne to the attractive Coulomb stabilization energy (the second term in Eq. 3.21), reaching a minimnm at the equilibrinm bond length, R = 2.17 A. If... 

We have discussed how ionic bonding results from electron transfer and Coulomb stabilization of the resulting ions and that the propensity of a pair of atoms to form an ionic bond is determined by the difference in their electronegativities. What kinds of bonds are formed between elements of identical or comparable electronegativities such as Hi or CO, and what is the driving force for bond formation from separated atoms in the gas phase ... 

---