Pulsed ESR/ENDOR and ESTN(Electron Spin Transient Nutation) study of polycationic high-spin states of one-and two-dimensional (diarylamino)benzenes

Polycationic high-spin states of 1,3-bis(diarylamino)benzenes, 1,3,5-tris(diarylamino)benzenes, and their homologues have been studied by cw and pulsed ESR/ENDOR spectroscopy. An electron spin transient nutation (ESTN) method based on pulsed ESR spectroscopy was applied to the dicationic and tricationic high-spin states of N,N,N′,N″-tetra(4-anisyl)-2,4-dimethyl-1,5phenylenediamine and N,N,N′,N′,N″,N″-hexa(4-anisyl)-1,3,5-triaminobenzene, respectively, in order to identify the spin multiplicity of the polycationic states. The observed 2D nutation spectra of the dicationic and tricationic states unequivocally showed that the dicationic and tricationic states are ground-state triplet and quartet, respectively. We have also carried out cw-and pulsed ENDOR measurements to the tricationic state of 1,3,5-tris(diarylamino)benzene, clarifying the electronic structure of the cationic quartet spin state. On the central phenyl ring there are carbon sites with large π-spin densities which are additively brought from each diarylamino moiety by spin polarization mechanism. In the triplet and quartet ground states, the topological spin polarization mechanism is dominant for forming the high-spin states.