Polycationic high-spin states of one- and two-dimensional (diarylamino)benzenes, prototypical model units for purely organic ferromagnetic metals as studied by pulsed ESR/electron spin transient nutation spectroscopy

Polycationic high-spin states of 1,3-bis(diarylamino)benzene and 1,3,5-tris(diarylamino)benzene as prototypical model units for organic ferromagnetic metals have been studied by cw and pulsed ESR spectroscopy. An electron spin transient nutation (ESTN) method as a novel technique based on pulsed ESR spectroscopy has been applied to the dicationic and tricationic high-spin states of them in glasses, unequivocally identifying the spin multiplicities of those molecules in the ground state to be triplet with the fine-structure parameters of \D\ = 0.007 cm(-1) and quartet with \D\ = 0.004 cm(-1), \E\ = 0.0002 cm(-1), and g = 2.0023, respectively, and concluding that the high-spin ground states originate from the topological pseudodegeneracy of the pi-HOMOs which governs spin alignment in polycationic heteroatomic systems. It has been illustrated by the resolution enhancement inherent in the dimensional decomposition of 2D spectroscopy that magnetic-field-swept 2D ESTN spectroscopy is a powerful and facile method for spin identification and discrimination between different spin multiplicities in nonoriented systems. Also, ESTN phenomena have been treated in terms of both numerical calculation and perturbation theory. An analytical expression for the nutational motion has been derived.