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Ab initio calculations were carried out for the 2-, 3-, and 4-pyridyl cations, anions, and radicals in order to examine their molecular structures and relative energies among three isomers. The 4-31G//3-21G calculations have predicted that 2-pyridyl cation, 4-pyridyl anion, and 2-pyridyl radical are most stable among the isomers.

The ESR spectra of the radical anions of 2,9- and 5,6-dimethyl-1,10-phenanthrolines have shown that these radical anions are in the 2B1 state, as is the unsubstituted 1,10-phenanthroline radical anion. MO calculations have indicated that the two lower electronic states of these radical anions, 2B1 and 2A2, lie close to each other, and that the relative stability is largely affected by an interaction with the counter cation.

The reaction space map (RESMAP) representation is proposed for the comprehensive description of the chlorination and dechlorination reactions of polychlorobenzenes. By using the B3LYP/6-311G** ener...

The electronic structures of allene episulfide, cyclopropanethione and thioxyallyl were examined by ab initio MO calculations and were compared with those of the corresponding oxygen compounds, allene oxide, cyclopropanone and oxyallyl. The difference in reactivities of allene episulfide and allene oxide was also speculatively estimated from the calculated electronic structures. The lowest singlet state of thioxyallyl was predicted to be the B2 state, which corresponds to the σ, π-diradical. A small activation energy is required for the cyclization of the B2 state to give allene episulfide. The A1 singlet state lies 11 kcal mol−1 higher than the B2 singlet state and undergoes the disrotatory rotation of methylene groups to give cyclopropanethione with no activation energy.