Novel Organic Ions of High-Spin States. 5. Generation of a High-Spin Ground-State Anion from an Intramolecularly Spin-Frustrated System

4,4‘,4‘‘-Tris(diphenylmethylene)amine (N( p -DPM) 3 ) may be regarded as a prototype of intramolecularly spin-frustrated organic systems. In the present work the monoanion of N( p -DPM) 3 was obtained by thermal electron attachment and studied by ESR spectroscopy to find that the ground state is a spin quartet with the fine-structure parameters of | D | = 0.123 cm - 1 and | E | = 0.005 cm - 1 and an isotropic g factor of 2.003. These results are explained consistently if the excess electron occupies an in-plane n non-bonding MO predominantly localized at the divalent carbon sites and if the molecular structure of N( p -DPM) 3 • - is of non- C 3 symmetry which indicates the quantum nature of the spin alignment in the spin-frustrated finite system. The temperature dependence of the ESR signal indicates that the lowest excited doublet state of the anion is located at least 300 cm - 1 above the quartet ground state.