Furan and thiophene
diarylmethenes are potential redox-active ligands for metal centers
that could be exploited in the development of nontraditional, stoichiometric,
and catalytic redox reactions. As such, we describe here the selective <i>meso</i>-deprotonations of dithiophene, difuran, and diimine–difuran
diarylmethanes to form the π-conjugated anions, for which only
the diimino–difuryl anion is truly isolable and studied by
X-ray crystallography. In all cases, facile one-electron oxidation
of these anions occurs, which allows the isolation of the neutral
dithienyl and diimino–difuryl radicals. UV–Visible and
time-dependent density functional theory studies reveal that the oxidation
of the dithienyl anion to its radical is associated with an increase
in the highest (singly) occupied molecular orbital–lowest unoccupied
molecular orbital gap, evident through a hypsochromic shift of the
main absorption band in the electronic spectrum, whereas oxidation
of the diimino–difuryl anion causes only minor spectroscopic
changes. Electrochemical studies support the stability of the radicals
with respect to the anion, showing strongly negative oxidation potentials.
The control of the redox activity of these diarylmethene carbanions
through variation of the nature of the substituents, donor-atom, and
the conjugated π-system and their potential as ligands for redox-inert
metal centers makes them intriguing candidates as noninnocent partners
for redox reactions