Subject ionization isomerism

Indazoles have been subjected to certain theoretical calculations. Kamiya (70BCJ3344) has used the semiempirical Pariser-Parr-Pople method with configuration interaction for calculation of the electronic spectrum, ionization energy, tt-electron distribution and total 7T-energy of indazole (36) and isoindazole (37). The tt-densities and bond orders are collected in Figure 5 the molecular diagrams for the lowest (77,77 ) singlet and (77,77 ) triplet states have also been calculated they show that the isomerization (36) -> (37) is easier in the excited state. 

Not only tautomeric equilibria are subject to considerable solvent effects. Other equilibria, such as rotational and conformational equilibria [81-83], cisitrans (or E/Z) isomerization, valence isomerization [84], ionization, dissociation, and association [85] (some of which are considered in Section 2.6), complex equilibria [86, 163, 262, 263], acid/base equilibria [264, 265] etc., are also strongly affected by the medium. Only a small number of representative examples will be considered in this Section in order to give an idea of how solvents can affect these different kinds of equilibria. 

Among multiple-bond-containing silicon compounds, neutral HNSi holds a special place. The [H,N,Si] potential energy surface and several possible N- and Si-substituted isomers have formed the subject of several experimentaP " and theoretical investigations . In a recent experimental and theoretical study, the ionic as well as the neutral [H,N,Si] surfaces were explored . Ionization of a mixture of iodosilane and NH3 gives rise to [H,N,Si]+ cations, which according to CA experiments exist in an N-protonated (65) rather than the isomeric Si-protonated form (66). 

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