Charge change localization

Coordination compounds and organometallics represent a vast group of compounds with a unique property There are two types of completely different redox centers - the metal based ones and the ligand based ones. These different redox centers have, of course, different properties, especially in the effect the charge change localized on them during electron transfer exerts upon the structure of the species. There is, however, a wide range of combination of these redox centers, from fully localized ones to fully delocalized, which provides not only intellectual interest for the study of complexes but also possibilities, how to use these properties for a broad variety of purposes. 

Example 12.4 Influence of the Environment on D i. Nitromethane is interesting to some people because it explodes. The reason is, of course, in the cleavage of the carbon-nitrogen bond. The monomer, compared to its trimer (taken as a model for the crystal), reveals that the C and N net charges change by A c — 8.7 and A n—1-1 me. respectively, on crystallization. Our bond energy formula and the appropriate parameters thus indicate that the crystalline environment reinforces the CN bond by 4.7 kcal/mol, which is significant at the local point of rupture, responsible for the reaction [251]. 

In addition to all these, it is also important to keep in mind that the results depend also on what types of surface equilibrium conditions exist as the double layers interact. For example, when two charged surfaces approach each other, the overlap of the double layers will also affect the manner in which the charges on the surfaces adjust themselves to the changing local conditions. As the double layers overlap and get compressed, the local ionic equilibrium at the surface may change, and this will clearly have an impact on the potential distribution and on the potential energy of interaction. 

The empirical correction factors 4> (calculated on assumption that for all networks swollen in pure water % from Eq. (6) should be 0.48) change between 0.05 and 0.3 (see Ref. [48] for salt I the data are in Fig. 8). Generally, we can say that the effect of the positive charge on the formation and extent of transition is 5 to 10 times smaller than the effect of MNa. There are probably several reasons for the low value of (a) positive charges are localized at a larger distance from the main chain (smaller influence on the chain conformation) (b) due to the... 

Clearly the charges and local softnesses contain different information since they sometimes change in the opposite direction. Even without proton jump, the sensitivity coefficients of the pyridine molecule are drastically affected. In this model, the role of the active surface is explicitly taken into account and can help us to better understand its influence on the activation of substrates. 

---