2006 年 5 巻 4 号 p. 171-176
High-spin stability of non-Kekulé-type molecule triiminiummethane ion (TIM3+) is discussed using the semiempirical molecular orbital method. The triplet ground state 3A2' with a D3h geometry is predicted to lie below the Jahn-Teller distorted singlet states similar to trimethylenemethane (TMM). The lowest singlet states 1B1, 1B2 and 1A1 with C2v geometries are nearly degenerate. The spin-density distribution of the 3A2' state is calculated and the origin of the spin alignment is discussed relating to the spin-polarization rule characteristic of high-spin organic molecules. The valence bond analysis on the spin states of TIM3+ is also carried out.
