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 π-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.
Functional materials for organic light‐emitting diodes (LEDs), in addition to exhibiting the qualities listed in the previous article, should also be thermally and morphologically stable and not crystallize even above the glass transition temperature. The synthesis and properties of hyperbranched π‐electron systems (such as that in the Figure) fulfilling these condition are presented, together with their unique multiredox properties.
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